JP2004128515A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing semiconductor device by which a crystalline silicon film having excellent characteristics can be obtained by removing or reducing a metallic element existing in a crystalline silicon film obtained by utilizing the element and, at the same time, a highly efficient semiconductor device can be obtained by using the silicon film. <P>SOLUTION: In this method, the crystalline silicon film is obtained by crystallizing an amorphous silicon film through first heat-treatment after introducing the metallic element which promotes the crystallization of silicon into the amorphous silicon film. Then the semiconductor device is obtained by removing or reducing the metallic element existing in the silicon film and, at the same time, removing a formed thermally oxidized film, by performing second heat-treatment in an oxidizing atmosphere and forming a thermally oxidized film on the surface of the area from which the thermally-oxidized film is removed by again performing thermal oxidation. In this method, an oxygen-containing oxidizing atmosphere, halogen-containing oxidizing atmosphere, or the like, is used as the oxidizing atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a semiconductor device and a manufacturing method thereof, and more specifically, to a semiconductor device represented by a thin film transistor and a manufacturing method thereof. The present invention also relates to a semiconductor device using a crystalline silicon thin film formed on a substrate such as a glass substrate or a quartz substrate, and a method for manufacturing the same. Further, the present invention relates to an insulating gate type semiconductor device such as a thin film transistor And a manufacturing method thereof.

Conventionally, a thin film transistor using a silicon film has been known. This is a technique for forming a thin film transistor using a silicon film formed on a glass substrate or a quartz substrate. The reason why a glass substrate or a quartz substrate is used as the substrate is to use the thin film transistor in an active matrix type liquid crystal display. Conventionally, thin film transistors have been formed using an amorphous silicon film (a-Si). However, in order to obtain higher performance, a silicon film having crystallinity (hereinafter referred to as a “crystalline silicon film” as appropriate) It has been attempted to produce a thin film transistor by using the above method.

(4) A thin film transistor using a crystalline silicon film can perform a high-speed operation of two digits or more as compared with a thin film transistor using an amorphous silicon film. Therefore, a peripheral drive circuit of an active matrix type liquid crystal display device, which has been constituted by an external IC circuit, can be formed on a glass substrate or a quartz substrate with a crystalline silicon film in the same manner as the active matrix circuit. it can. Such a configuration is very advantageous for miniaturization of the entire apparatus and simplification of a manufacturing process, and also leads to a reduction in manufacturing cost.

Conventionally, a crystalline silicon film is obtained by forming an amorphous silicon film by a plasma CVD method or a low pressure thermal CVD method, and then performing crystallization by performing a heat treatment or laser light irradiation. However, in the case of heat treatment, it is difficult at present to obtain the required crystallinity over a wide area due to uneven crystallization. In the case of laser light irradiation, high crystallinity can be obtained partially, but it is difficult to obtain a good annealing effect over a wide area. In this case, the irradiation of the laser beam under the condition for obtaining particularly good crystallinity tends to be unstable.

By the way, the present inventors have introduced a technique of introducing a metal element (for example, nickel) that promotes crystallization of silicon into an amorphous silicon film and obtaining a crystalline silicon film by heat treatment at a lower temperature than before. (JP-A-6-232520, JP-A-7-321339). According to these methods, not only can the crystallization speed be increased and the crystallization can be performed in a short time, but also compared to the conventional crystallization method using only heating or crystallization of an amorphous film using only laser light irradiation, High crystallinity can be obtained uniformly over a large area, and the obtained crystalline silicon film has crystallinity that can be practically used.

However, since the metal element introduced to promote crystallization of silicon is contained in the film and the surface of the crystalline silicon film obtained by the above method, the control of the amount of introduction is delicate. And reproducibility and stability (electrical stability of the obtained device). In particular, due to the influence of the remaining metal element, for example, there is a problem that the characteristics of the obtained semiconductor device change over time, and in the case of a thin film transistor, the OFF value is large. That is, the metal element that promotes the crystallization of silicon plays a valuable and useful role in obtaining a crystalline silicon film, but its existence presents a number of problems once a crystalline silicon film is obtained. It becomes a negative factor to cause.

The present inventors have introduced a metal element (for example, nickel) that promotes crystallization of silicon into an amorphous silicon film as described above, and heat-treated the amorphous silicon film. In order to solve the problem, a number of experiments and examinations were carried out from various directions. As a result, the metal element contained in the crystalline silicon film and remaining was identified by a specific method which will be described later. It has been found that it can be eliminated or reduced, leading to the present invention.

By the way, for example, an active matrix type liquid crystal display device is small and lightweight, and can display fine and high-speed moving images. However, since the substrate constituting the liquid crystal display device has a restriction that it needs to have a light-transmitting property, its type is limited, and examples thereof include a plastic substrate, a glass substrate, and a quartz substrate.

Among them, plastic substrates lack heat resistance, and quartz substrates can withstand high temperatures of about 1000 ° C., and even about 1100 ° C., but are extremely expensive, especially when the area is increased. The price is more than 10 times the price of a glass substrate, and lacks cost performance. Therefore, glass substrates are generally widely used for reasons of heat resistance and economy.

At present, the performance required for liquid crystal display devices is increasing, and the demands for performance and characteristics required for thin film transistors (hereinafter, appropriately referred to as TFTs) used as switching elements of liquid crystal display devices are also increasing. Therefore, research on forming a crystalline silicon film having crystallinity on a glass substrate has been actively conducted. However, at present, to form a crystalline silicon film on a glass substrate, first, an amorphous silicon film is used. Are formed and heated to crystallize, or a method of irradiating laser light to crystallize.

That is, although the heat resistance temperature of the glass substrate depends on the kind thereof, it is usually about 600 ° C. or slightly higher than that, so that the step of forming a crystalline silicon film requires the use of such a glass substrate. It is not possible to adopt a process that exceeds the heat resistance temperature. For this reason, conventionally, in order to form a crystalline silicon film on a glass substrate, a method of forming an amorphous silicon film by a plasma CVD method or a low pressure CVD method and then heating the amorphous silicon film to a temperature lower than the above-mentioned heat-resistant temperature to crystallize it is used. Has been adopted. Further, according to the method in which a silicon film is crystallized by irradiating a laser beam, a crystalline silicon film having excellent crystallinity can be formed on a glass substrate, and the laser beam is thermally applied to the glass substrate. It has the advantage of not causing significant damage.

However, a crystalline silicon film obtained by crystallizing an amorphous silicon film by irradiation with the laser light has many defects derived from dangling bonds and the like. Since these defects are factors that degrade the characteristics of the TFT, when a TFT is manufactured using such a crystalline silicon film, defects at the interface between the active layer and the gate insulating film and the silicon in the active layer are not obtained. It is necessary to passivate the defects in the crystal grains and at the crystal grain boundaries. In particular, defects at the grain boundaries are the largest factor for scattering the electric charge, but it is very difficult to passivate the defects at the grain boundaries.

On the other hand, when a TFT is manufactured on a quartz substrate, high-temperature heat treatment, for example, about 1000 ° C. or about 1100 ° C. is possible, so that defects at crystal grain boundaries of the crystalline silicon film are compensated by silicon. It is possible to do. On the other hand, when manufacturing a TFT on a glass substrate, it is difficult to perform heat treatment at a high temperature. In general, by performing hydrogen plasma treatment in an atmosphere at a temperature of about 300 to 400 ° C. in the final stage of the process, The defects at the crystal grain boundaries of the crystalline silicon film are passivated with hydrogen.

(4) The N-channel TFT exhibits a practical field-effect mobility by performing the hydrogen plasma treatment. On the other hand, the effect of the hydrogen plasma treatment is not so remarkable in the P-channel TFT. This is interpreted as the level caused by crystal defects being formed in a relatively shallow region below the conduction electron band. Defects at the grain boundaries of the crystalline silicon film can be compensated by the hydrogen plasma treatment. However, since hydrogen compensating for the defects is easily released, the hydrogen plasma-treated TFT, especially an N-channel TFT, is used. Is not stable over time. For example, when an N-channel TFT is energized for 48 hours in an atmosphere at a temperature of 90 ° C., the mobility is reduced by half.

Although the crystalline silicon film obtained by irradiating the laser beam has good film quality, if the thickness is less than 1000 angstroms, ridges (irregularities) are formed on the surface of the crystalline silicon film. That is, when the silicon film is irradiated with a laser beam, the silicon film is instantaneously melted and locally expanded. In order to reduce internal stress caused by the expansion, a ridge (R) is formed on the surface of the obtained crystalline silicon film. Irregularities) are formed. The height difference of the ridge is about 1/2 to 1 times the film thickness. For example, when laser annealing is performed after an amorphous silicon film having a thickness of about 700 angstroms is heated and crystallized, a ridge having a height of about 100 to 300 angstroms is formed on the surface.

In an insulating gate type semiconductor device, potential barriers and trap levels due to dangling bonds and lattice distortion are formed at ridges on the surface of the crystalline silicon film, so that an interface between the active layer and the gate insulating film is formed. Raises the level. In addition, since the top of the ridge is steep, the electric field tends to concentrate, which may cause a leak current and eventually cause dielectric breakdown. The ridge on the surface of the crystalline silicon film impairs the coverage of the gate insulating film deposited by the sputtering method or the CVD method, and lowers the reliability such as insulation failure.

The present invention forms a crystalline silicon film using a metal element that promotes crystallization of silicon in an amorphous silicon film, and removes or removes the metal element in the crystalline silicon film obtained thereby. It is an object of the present invention to provide a new and extremely useful method for reducing the metal element concentration.

Further, the present invention is obtained by removing a metal element or reducing the concentration of the metal element from a crystalline silicon film obtained by using a metal element which promotes crystallization of silicon in an amorphous silicon film. It is an object to provide a semiconductor device having high characteristics using a crystalline silicon film having high crystallinity and a manufacturing method thereof. Still another object of the present invention is to provide a semiconductor device which can improve characteristics and reliability of the semiconductor device thus obtained, and a manufacturing method thereof.

Further, the present invention solves the above-mentioned problems and provides a method of manufacturing a semiconductor device capable of passivating defects at crystal grain boundaries of a silicon film obtained by crystallizing an amorphous silicon film without using a hydrogen plasma treatment. The purpose is to provide. Another object of the present invention is to provide a method for manufacturing a semiconductor device having high reliability and high mobility. In particular, the present invention has a gate insulating film made of a deposited film, and has the reliability and characteristics of a glass substrate semiconductor device. It is an object to provide an improved semiconductor device and a manufacturing method thereof. In addition to the above, the present invention has an object corresponding to the configuration described below, and these will be supplementally described in the following description as appropriate.

(1) In the present invention, a metal element which promotes crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of performing a second heat treatment in an oxidizing atmosphere to remove or reduce the metal element present in the crystalline silicon film, and a step of removing the thermal oxide film formed in the step. Forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed.

(2) In the present invention, a metal element for promoting crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to form a crystalline silicon film. Obtaining a second thermal oxidation process in an oxidizing atmosphere to form a thermal oxide film on the surface of the crystalline silicon film, and gettering the thermal oxide film with the metal element. A step of removing or reducing the metal element present in the silicon film, a step of removing the thermal oxide film formed in the step, and a thermal oxidation step on the surface of the region from which the thermal oxide film has been removed by thermal oxidation again. And a step of forming an oxide film.

(3) In the present invention, a metal element which promotes crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of performing a second thermal oxidation treatment in an oxidizing atmosphere to remove or reduce the metal element present in the crystalline silicon film, and a step of removing the thermal oxide film formed in the step A step of forming an active layer of a thin film transistor by patterning, and a step of forming a thermal oxide film constituting at least a part of the gate insulating film on the surface of the active layer by thermal oxidation. A method for manufacturing a device is provided.

(4) The present invention provides a step of selectively introducing a metal element for promoting crystallization of silicon into an amorphous silicon film, and a step of forming a film from a region where the metal element is selectively introduced by the first heat treatment. Performing a crystal growth in a direction parallel to the above, a step of performing a second heat treatment in an oxidizing atmosphere to form a thermal oxide film on the surface of the region where the crystal growth has been performed, A method for manufacturing a semiconductor device, comprising: a step of removing; and a step of forming an active layer of a semiconductor device using a region from which the thermal oxide film is removed.

(5) The present invention has a crystalline silicon film sandwiched between first and second oxide films, wherein the crystalline silicon film contains a metal element that promotes crystallization of silicon. The present invention provides a semiconductor device, wherein the metal element has a high concentration distribution in the vicinity of the interface with the first and / or second oxide film in the conductive silicon film.

(6) The present invention includes a base film made of an oxide film, a crystalline silicon film formed on the base film, and a thermal oxide film formed on the crystalline silicon film. The silicon film contains a metal element that promotes crystallization of silicon, and the metal element that promotes crystallization of silicon has a high concentration distribution in the vicinity of an interface with a base and / or a thermal oxide film. An oxide film forms at least a part of a gate insulating film of a thin film transistor.

(7) The present invention provides a method in which a metal element which promotes crystallization of silicon is intentionally introduced into an amorphous silicon film and the amorphous silicon film is crystallized by a first heat treatment to form a crystalline silicon film. Obtaining, a second heat treatment in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the crystalline silicon film, and a heat treatment formed in the step. A method for manufacturing a semiconductor device, comprising: a step of removing an oxide film; and a step of forming a thermal oxide film by thermal oxidation again on a surface of a region from which the thermal oxide film has been removed.

(8) In the present invention, a metal element for promoting crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Performing a second heat oxidation treatment in an oxidizing atmosphere containing a halogen element to form a thermal oxide film on the surface of the crystalline silicon film, and to getter the metal element on the thermal oxide film. Removing or reducing the metal element present in the crystalline silicon film, removing the thermal oxide film formed in the process, and re-applying the surface of the region from which the thermal oxide film has been removed. Forming a thermal oxide film by thermal oxidation.

(9) In the present invention, a step of intentionally introducing a metal element for promoting crystallization of silicon into an amorphous silicon film and crystallizing the amorphous silicon film by a first heat treatment to obtain a crystalline silicon film And a step of performing a second heat oxidation treatment in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the crystalline silicon film, and a step of removing the thermal oxide film formed in the step. Removing, forming an active layer of the thin film transistor by patterning, and forming a thermal oxide film constituting at least a part of the gate insulating film on the surface of the active layer by thermal oxidation. And a method for manufacturing a semiconductor device.

(10) The present invention provides a step of selectively introducing a metal element for promoting crystallization of silicon into an amorphous silicon film, and a step of forming a film from a region where the metal element is selectively introduced by the first heat treatment. Forming a thermal oxide film on the surface of the region where the crystal growth has been performed by performing a second heat treatment in an oxidizing atmosphere containing a halogen element, A step of removing the thermal oxide film; and a step of forming an active layer of the semiconductor device using the region from which the thermal oxide film has been removed.

(11) The present invention has a crystalline silicon film sandwiched between first and second oxide films, the crystalline silicon film containing hydrogen and a halogen element, and a metal element for promoting crystallization of silicon. Wherein the metal element has a high concentration distribution near the interface with the first and / or second oxide film in the crystalline silicon film. provide.

(12) The present invention includes a base film made of an oxide film, a crystalline silicon film formed on the base film, and a thermal oxide film formed on the crystalline silicon film. The silicon film contains a metal element which promotes crystallization of silicon, hydrogen and a halogen element, and the metal element which promotes crystallization of silicon has a high concentration distribution near the interface with the base and / or the thermal oxide film. Wherein the halogen element has a high concentration distribution in the vicinity of an interface with a base and / or a thermal oxide film, and the thermal oxide film constitutes at least a part of a gate insulating film of a thin film transistor. I will provide a.

(13) In the present invention, a metal element for promoting crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of irradiating the crystalline silicon film with laser light or strong light, and performing a second heat treatment in an oxidizing atmosphere containing a halogen element to be present in the crystalline silicon film. A step of removing or reducing the metal element, a step of removing the thermal oxide film formed in the step, and a step of forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed And a method for manufacturing a semiconductor device.

(14) In the present invention, a step of intentionally introducing a metal element for promoting crystallization of silicon into an amorphous silicon film and crystallizing the amorphous silicon film by a first heat treatment to obtain a crystalline silicon film Irradiating the crystalline silicon film with laser light or intense light to diffuse the metal element present in the crystalline silicon film in the crystalline silicon film, and including a halogen element. Performing a second heat treatment in an oxidizing atmosphere to getter the metal element present in the crystalline silicon film into the thermal oxide film to be formed; A method for manufacturing a semiconductor device, comprising: a step of removing; and a step of forming a thermal oxide film by thermal oxidation again on a surface of a region from which the thermal oxide film has been removed.

(15) In the present invention, a step of intentionally and selectively introducing a metal element for promoting crystallization of silicon into an amorphous silicon film, and performing a first heat treatment on the amorphous silicon film; A step of intentionally and selectively growing a crystal in a direction parallel to the film from a region in which the metal element is introduced, and a step of irradiating laser light or intense light with the metal present in the crystal-grown region. A step of diffusing the element, and a step of performing a second heat treatment in an oxidizing atmosphere containing a halogen element to getter the metal element present in the crystal-grown region in the formed thermal oxide film A step of removing the thermal oxide film formed in the step, and a step of forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed. A method for manufacturing a device is provided.

(16) In the present invention, a metal element which promotes crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of patterning the crystalline silicon film to form an active layer of a semiconductor device, a step of irradiating the active layer with laser light or intense light, and in an oxidizing atmosphere containing a halogen element. Performing a second heat treatment to remove or reduce the metal element present in the active layer; removing the thermal oxide film formed in the step; Forming a thermal oxide film by oxidation.

(17) The present invention provides a method in which a metal element that promotes crystallization of silicon is intentionally introduced into an amorphous silicon film and the amorphous silicon film is crystallized by a first heat treatment to form a crystalline silicon film. Obtaining, a step of patterning the crystalline silicon film to form an active layer of a semiconductor device, a step of irradiating the active layer with laser light or strong light, and a step of irradiating the active layer with an oxidizing atmosphere containing a halogen element. Performing a second heat treatment to remove or reduce the metal element present in the active layer; removing the thermal oxide film formed in the step; Forming a thermal oxide film by thermal oxidation, wherein the active layer has an inclined shape having an angle of 20 ° to 50 ° with respect to a side surface of the active layer. I will provide a.

(18) In the present invention, a metal element which promotes crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of irradiating the crystalline silicon film with laser light or strong light, and performing a second heat treatment in an oxidizing atmosphere to remove the metal element present in the crystalline silicon film or Reducing, a step of removing the thermal oxide film formed in the step, and a step of forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed. And a method for manufacturing a semiconductor device.

(19) In the present invention, a metal element for promoting crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of irradiating the crystalline silicon film with laser light or intense light to diffuse the metal element present in the crystalline silicon film in the crystalline silicon film; Performing a second heat treatment, gettering the metal element present in the crystalline silicon film into the formed thermal oxide film, and removing the thermal oxide film formed in the process. Forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed.

(20) The present invention provides a step of intentionally and selectively introducing a metal element for promoting crystallization of silicon into an amorphous silicon film, and performing a first heat treatment on the amorphous silicon film; A step of intentionally and selectively growing a crystal in a direction parallel to the film from a region in which the metal element is introduced, and a step of irradiating laser light or intense light with the metal present in the crystal-grown region. A step of diffusing the element, a step of performing a second heat treatment in an oxidizing atmosphere, and a step of gettering the metal element present in the crystal-grown region into a thermal oxide film to be formed; A method for manufacturing a semiconductor device, comprising: a step of removing a formed thermal oxide film; and a step of forming a thermal oxide film by thermal oxidation again on a surface of a region from which the thermal oxide film has been removed. provide.

(21) In the present invention, a metal element for promoting crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of patterning the crystalline silicon film to form an active layer of the semiconductor device, a step of irradiating the active layer with laser light or strong light, and a step of performing second heating in an oxidizing atmosphere. Performing a treatment to remove or reduce the metal element present in the active layer; removing the thermal oxide film formed in the process; and thermally oxidizing the surface of the active layer by thermal oxidation again. And a step of forming a film.

(22) In the present invention, a metal element for promoting crystallization of silicon is intentionally introduced into an amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. A step of patterning the crystalline silicon film to form an active layer of the semiconductor device, a step of irradiating the active layer with laser light or strong light, and a step of performing second heating in an oxidizing atmosphere. Performing a treatment to remove or reduce the metal element present in the active layer; removing the thermal oxide film formed in the process; and thermally oxidizing the surface of the active layer by thermal oxidation again. Forming a film, wherein the active layer has an inclined shape in which a side surface forms an angle of 20 ° to 50 ° with a base surface.

(23) The present invention provides a step of forming an amorphous silicon film on a substrate having an insulating surface, a step of intentionally introducing a metal element for promoting crystallization of silicon into the amorphous silicon film, A step of crystallizing the amorphous silicon film by a first heat treatment at 750 ° C. to 1100 ° C. to obtain a crystalline silicon film, and a step of patterning the crystalline silicon film to form an active layer of a semiconductor device. Performing a second heat treatment in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the active layer; and removing the thermal oxide film formed in the step. And forming a thermal oxide film by thermal oxidation again after removing the thermal oxide film, wherein the temperature of the second heat treatment is higher than the temperature of the first heat treatment. And a method for manufacturing a semiconductor device.

(24) The present invention provides a step of forming an amorphous silicon film on a substrate having an insulating surface, a step of intentionally introducing a metal element for promoting crystallization of silicon into the amorphous silicon film, A step of crystallizing the amorphous silicon film by a first heat treatment at 750 ° C. to 1100 ° C. to obtain a crystalline silicon film, and a step of patterning the crystalline silicon film to form an active layer of a semiconductor device. Performing a second heat treatment in an oxidizing atmosphere containing a halogen element to getter the metal element present in the active layer into a thermal oxide film to be formed; Removing the thermally oxidized film, and forming a thermally oxidized film by thermal oxidation again after removing the thermally oxidized film, wherein the temperature of the second heat treatment is the first heat treatment. A method for manufacturing a semiconductor device, which is higher than a processing temperature To provide.

(25) The present invention provides a step of forming an amorphous silicon film on a substrate having an insulating surface and a step of intentionally and selectively introducing a metal element for promoting crystallization of silicon into the amorphous silicon film. And a step of performing crystal growth in a direction parallel to the film from a region of the amorphous silicon film into which the metal element is intentionally and selectively introduced by a first heat treatment at a temperature of 750 ° C. to 1100 ° C. Forming an active layer of a semiconductor device using a region crystallized in a direction parallel to the film by patterning; and performing a second heat treatment in an oxidizing atmosphere containing a halogen element to form the active layer. A step of gettering the metal element present therein into the formed thermal oxide film, a step of removing the thermal oxide film formed in the step, and a step of removing the thermal oxide film again, Forming a thermal oxide film by The temperature of the second heat treatment is to provide a method for manufacturing a semiconductor device, wherein the higher than the temperature of the first heat treatment.

(26) In the present invention, a step of forming an amorphous silicon film, a step of contacting and holding a metal element for promoting crystallization of silicon on the surface of the amorphous silicon film, and a first heat treatment are performed. Crystallizing the amorphous silicon film to obtain a crystalline silicon film, and performing a second heat treatment at a temperature of 500 ° C. to 700 ° C. in an atmosphere containing oxygen, hydrogen, and fluorine to form the crystalline silicon film. There is provided a method for manufacturing a semiconductor device, comprising: a step of forming a thermal oxide film on a surface of a film; and a step of removing the thermal oxide film.

(27) In the present invention, a step of forming an amorphous silicon film, a step of contacting and holding a metal element which promotes crystallization of silicon on the surface of the amorphous silicon film, and a first heat treatment are performed. Crystallizing the amorphous silicon film to obtain a crystalline silicon film, and performing a second heat treatment at a temperature of 500 ° C. to 700 ° C. in an atmosphere containing oxygen, hydrogen, fluorine and chlorine. A method for manufacturing a semiconductor device, comprising: a step of forming a thermal oxide film on a surface of a conductive silicon film; and a step of removing the thermal oxide film.

(28) The present invention provides a step of forming an amorphous silicon film, a step of holding a metal element that promotes crystallization of silicon in contact with the surface of the amorphous silicon film, and a step of performing heat treatment to form the amorphous silicon film. Crystallizing the crystalline silicon film to obtain a crystalline silicon film, forming a wet oxide film on the surface of the crystalline silicon film in an atmosphere containing fluorine and / or chlorine, and removing the oxide film And a method for manufacturing a semiconductor device.

(29) The present invention is a semiconductor device having a silicon film having crystallinity, wherein the silicon film contains a metal element for promoting crystallization of silicon at 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁸ cm ^{−. 3} and fluorine atoms are contained at a concentration of 1 × 10 ¹⁵ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ , and hydrogen atoms are contained at a concentration of 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ²¹ cm ⁻³ . Provided is a semiconductor device which is contained at a concentration. The concentration unit “... Cm ⁻³ ” means the number of atoms per cubic centimeter (atoms / cm ³ ), and is the same in this specification.

(30) The present invention provides a step of forming an amorphous silicon film, a step of crystallizing the amorphous silicon film to form a crystalline silicon film, and a step of heating in an oxidizing atmosphere to which a fluorine compound gas is added. Growing a thermal oxide film on the surface of the crystalline silicon film, removing the thermal oxide film on the surface of the crystalline silicon film, and depositing an insulating film on the surface of the crystalline silicon film And a method for manufacturing a semiconductor device.

(31) The present invention includes a step of forming an amorphous silicon film, a step of irradiating a laser beam to crystallize the amorphous silicon film to form a crystalline silicon film, and adding a fluorine compound gas. Heating in an oxidizing atmosphere to grow a thermal oxide film on the surface of the crystalline silicon film; removing the thermal oxide film on the surface of the crystalline silicon film; And a step of depositing a film.

(32) The present invention provides a method for manufacturing a thin film transistor on a substrate having an insulating surface, wherein a step of forming an amorphous silicon film and a step of crystallizing the amorphous silicon film to form a crystalline silicon film Heating in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film, and removing the thermal oxide film on the crystalline silicon film surface; Shaping the crystalline silicon film to form an active layer of a thin film transistor; depositing an insulating film on a surface of the active layer to form a gate insulating film on at least a surface of a channel region; Forming a gate electrode on the surface of the film; and implanting impurity ions imparting a conductivity type to the active layer using the gate electrode as a mask to form a source and a drain in a self-aligned manner. Especially To provide a method for manufacturing a semiconductor device according to.

(33) The present invention provides a method for manufacturing a thin film transistor on a substrate having an insulating surface, wherein a step of forming an amorphous silicon film, a step of crystallizing the amorphous silicon film to form a crystalline silicon film, Irradiating the crystalline silicon film with a laser beam; heating the crystalline silicon film in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film; Removing the thermal oxide film on the surface of the film, shaping the crystalline silicon film to form an active layer of the thin film transistor, and depositing an insulating film on the surface of the active layer to form at least a surface of the channel region. Forming a gate insulating film, forming a gate electrode on the surface of the gate insulating film, implanting impurity ions for imparting a conductivity type to the active layer using the gate electrode as a mask, and forming a source and a drain. Own There is provided a method for manufacturing a semiconductor device characterized by comprising the step of aligning manner.

As described above, according to the present invention, the metal can be removed from the crystalline silicon film obtained by using the metal element that promotes crystallization of silicon, and the concentration thereof can be reduced. By kettering the metal in an oxidizing atmosphere containing the halogen, particularly an oxidizing atmosphere to which halogen is added, a silicon film having excellent crystallinity can be obtained. In addition, a thin film semiconductor device having higher reliability and excellent performance can be obtained by using these crystalline silicon films.

In the method for manufacturing a semiconductor device according to the present invention, the thermal oxide film is grown in an oxidizing atmosphere to which fluorine is added, so that the temperature is lower than the strain point of the glass substrate for several hours to several tens of times. By heating for a time, a thermal oxide film can be grown to a thickness of several hundred angstroms. Further, by growing the thermal oxide film, excess Si is generated, and defects at the crystal grain boundaries of the crystalline silicon film can be passivated with Si, so that hydrogen plasma treatment can be eliminated. .

Furthermore, since the surface of the crystalline silicon film can be flattened by the thermal oxidation process, even if the process of irradiating the laser beam to obtain the crystalline silicon film is adopted, the gate insulating film formed of the deposited film can be used. Can be formed with good covering properties. Therefore, the interface state between the gate insulating film and the active layer can be reduced. In addition, the crystalline silicon film obtained by laser light irradiation has excellent crystallinity, so that the mobility of the semiconductor device can be further improved. Therefore, an insulating gate type semiconductor device such as a TFT having high mobility and high reliability can be manufactured over a substrate such as a glass substrate which is difficult to process at a high temperature such as about 1000 ° C.

In a typical embodiment of the present invention, first, a metal element that promotes crystallization of silicon is introduced into the surface of a previously formed amorphous silicon film, and a crystalline silicon film is formed using the metal element. I do. Next, by forming a thermal oxide film on the surface of the crystalline silicon film, the metal element is transferred or gettered into the thermal oxide film, and the concentration of the metal element in the crystalline silicon film is reduced or The metal element is removed.

The formation of the amorphous silicon film can be performed by a plasma CVD method, a low pressure thermal CVD method, or other appropriate methods. The amorphous silicon film is formed on an appropriate solid surface, but is formed on a substrate when the semiconductor device is configured as a semiconductor device. The substrate is not particularly limited, and a glass substrate, a quartz substrate, a ceramic substrate, or another substrate is used. Further, the amorphous silicon film is also formed on a film such as a silicon oxide film formed on the surface of the substrate, but the substrate in this specification includes these cases. Meaning.

Next, a metal element for promoting crystallization of silicon is introduced into the surface of the amorphous silicon film formed in advance as described above. Metal elements that promote crystallization of silicon include iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium (Ir). ), Platinum (Pt), copper (Cu), and gold (Au). The metal element is a metal element used as a metal element that promotes crystallization of silicon in any of the inventions described in this specification. Metal element that promotes the crystallization of silicon to be produced ".

The locations where these metal elements are introduced include (a) the entire surface of the amorphous silicon film, and (b) a slit-shaped surface at an appropriate location on the film surface of the amorphous silicon film (in this embodiment, preferably, (Slit-shaped openings are provided on the surface of the silicon film.) (C) End portions of the surface of the amorphous silicon film (for example, if the film surface of the amorphous silicon film is a rectangular surface, (D) one end, two ends, three ends or four ends, or, if the film surface of the amorphous silicon film is a circular surface, its peripheral portion, etc.) Although there is no particular limitation on the center portion of the film surface of the amorphous silicon film, (e) dots (that is, dots at predetermined intervals on the film surface of the amorphous silicon film), the above (A) to (A) are preferable. It is introduced in the mode of a).

The dimensions of the slit-shaped opening in the mode of introducing into the slit-shaped surface in the mode of the above (A) are not particularly limited. For example, a method of introducing the metal salt solution is applied as follows. In the embodiment, the width may be, for example, 20 μm or more, depending on the wettability and fluidity of the solution. The length in the longitudinal direction may be arbitrarily determined, and may be, for example, in the range of about several tens μm to 30 cm. In addition, a mode in which the metal element is introduced to the back surface of the amorphous silicon film is adopted, and the metal element can be introduced to both front and back surfaces.

The method of introducing these metal elements into the amorphous silicon film is not particularly limited as long as the metal element can be present on or in the surface of the amorphous silicon film. , A CVD method, a plasma processing method (including a plasma CVD method), an adsorption method, and a method of applying a solution of a metal salt can be used. Among them, the method using a solution is simple and useful in that the concentration of the metal element can be easily adjusted. As the metal salt, various salts can be used. As the solvent, in addition to water, alcohols, aldehydes, ethers, and other organic solvents, or a mixed solvent of water and an organic solvent can be used. The solution is not limited to a solution in which the salt is completely dissolved, and may be a solution in which part or all of the metal salt exists in a suspended state.

As for the kind of the metal salt, any salt can be used regardless of an organic salt or an inorganic salt as long as it can exist as a solution or a suspension as described above. For example, iron salts include ferrous bromide, ferric bromide, ferric acetate, ferrous chloride, ferrous chloride, ferric fluoride chloride, ferric nitrate, and ferrous phosphate. And ferric phosphate, and the like, and examples of the cobalt salt include cobalt bromide, cobalt acetate, cobalt chloride, cobalt fluoride, and cobalt nitrate.

Nickel salts include nickel bromide, nickel acetate, nickel oxalate, nickel carbonate, nickel chloride, nickel iodide, nickel nitrate, nickel sulfate, nickel formate, nickel oxide, nickel hydroxide, nickel acetyl acetate, and 4-cyclohexyl. Examples thereof include nickel butyrate and nickel 2-ethylhexanoate. Examples of ruthenium salts include ruthenium chloride and the like, examples of rhodium salts include rhodium chloride and the like, examples of palladium salts include palladium chloride and the like, examples of osmium salts include osmium chloride and the like, and examples of iridium salts. Examples include iridium trichloride and iridium tetrachloride, platinum salts include platinum chloride, and copper salts include copper acetate, cupric chloride, and cupric nitrate. Examples include gold trichloride, gold chloride and the like.

後 After the metal element is introduced into the amorphous silicon film as described above, a crystalline silicon film is formed using the metal element. This crystallization is performed by a heat treatment (thermal crystallization: Solid Phase Crystallization), or irradiation with a laser beam or strong light such as ultraviolet light or infrared light, but a heat treatment is preferably used. In the case where heat treatment is performed, laser light irradiation or strong light irradiation may be performed thereafter. This thermal crystallization proceeds in an atmosphere containing hydrogen or oxygen as a heating atmosphere, but preferably an inert atmosphere such as nitrogen or argon is used. Note that this heat treatment or this heat treatment temperature is appropriately referred to as “first heat treatment” or “first heat treatment temperature” in this specification.

The first heat treatment can be performed at a temperature of about 450 to 1100 ° C., and preferably at a temperature of about 550 to 1050 ° C. The crystallization proceeds even at a temperature of about 400 ° C., but in this case, the crystallization speed is slow and a long time is required. Therefore, the temperature is about 450 ° C. or more, preferably about 550 ° C. or more. When a heat-resistant substrate such as a quartz substrate is used as the substrate, the temperature is preferably 700 ° C. or higher, more preferably 750 ° C. or higher. If the heat treatment temperature is higher, higher quality crystals can be obtained and the crystallization rate can be increased.

For example, when a glass substrate having a strain point of 667 ° C. is used as the substrate, the first heating temperature is limited to about 600 to 650 ° C. in relation to the strain point, but a glass substrate having higher heat resistance may be used. Needless to say, a higher temperature may be used. In the case of a quartz substrate, the temperature can be applied up to about 1100 ° C., but it is preferably about 1050 ° C. or less. If the temperature exceeds about 1050 ° C., the jig made of quartz may be distorted or a load may be applied to the apparatus. In this sense, the temperature is preferably 980 ° C. or lower. However, when a more heat-resistant jig is used, the temperature can be reduced to about 1100 ° C. After the heat treatment, irradiation with laser light or irradiation with strong light such as infrared light or ultraviolet light can be performed.

Next, a thermal oxide film is formed on the surface of the crystalline silicon film. In the present invention, this allows the metal element to migrate or getter into the thermal oxide film, thereby reducing the concentration of the metal element in the crystalline silicon film or removing the metal element. An oxidizing atmosphere is used to form the thermal oxide film. Preferred embodiments thereof include (f) an oxygen atmosphere, (g) an atmosphere containing oxygen, and (h) a compound which releases oxygen at the temperature at which the thermal oxide film is formed. , An atmosphere containing (h) halogen, an atmosphere containing oxygen and halogen (c) and (h) to (h), and the like.

This thermal oxide film can be formed in the same range as the temperature applied in the thermal crystallization, that is, in the range of about 450 to 1100 ° C, preferably in the range of about 700 to 1050 ° C, and more preferably in the range of about 800 ° C. It can be performed in the range of -1050 ° C. This temperature can be about the same as the temperature applied in thermal crystallization (first heat treatment temperature), but is preferably higher than the temperature applied in thermal crystallization. Thereby, a thermal oxide film can be formed, and thermal crystallization can be further advanced as compared with the case where the thermal oxidation is performed at a temperature approximately equal to the first heat treatment temperature.

In this manner, a thermal oxide film is formed on the surface of the crystalline silicon film. At this time, due to the action of oxygen in the oxidizing atmosphere, the action of halogen, or the action of oxygen and halogen, the metal element is gettered in the thermal oxide film. The ring is formed, and the concentration of the metal element in the crystalline silicon film is reduced or the metal element is removed. Further, with the formation of the thermal oxide film, the crystallinity of the crystalline silicon film is improved. Note that the heat treatment for forming the thermal oxide film or the temperature thereof is appropriately referred to as “second heat treatment” or “second heat treatment temperature” in this specification.

Next, the thermal oxide film on which the metal element has been gettered is removed. The method for removing the thermal oxide film is not particularly limited as long as the thermal oxide film can be removed. For example, buffer hydrofluoric acid or another hydrofluoric acid-based etchant can be used. Thus, a crystalline silicon film which has high crystallinity and from which the metal element is removed or whose concentration is low is obtained. This crystalline silicon film has excellent characteristics as various elements in a semiconductor device, and particularly has extremely excellent characteristics as an active layer thereof.

FIGS. 1 to 4 are micrographs of several examples of the crystalline silicon film obtained by the present invention. 1 and 2 are enlarged photographs of 450 times magnification by an optical microscope, FIG. 3 is an enlarged photograph of 50,000 times (50,000 times) by a transmission electron microscope (TEM), and FIG. 4 is magnification by a transmission electron microscope. It is an enlarged photograph of 250,000 times (250,000 times).

FIG. 1 shows a crystalline silicon film obtained by introducing and applying a nickel element to one end of a rectangular amorphous silicon film and crystallizing the same. FIG. Is a crystalline silicon film obtained by being introduced, applied and crystallized over the entire surface of the substrate. As is clear from the photograph of FIG. 1, it can be seen that the crystal grows from one end to the other end in parallel or almost parallel. In the photograph of FIG. 2, which is a case where the nickel element is grown by applying the nickel element to the entire surface of the amorphous silicon film, star-shaped shading is seen, and the crystal grows radially around many points. You can see that.

Next, FIGS. 3 and 4 are enlarged photographs taken by a transmission electron microscope. The crystalline silicon films shown in FIGS. 3 and 4 are obtained by the following steps (A) to (G). (These steps are similar to the steps of Example 21 described later). These steps (A) to (G) are schematically shown in FIG.

(A) A quartz substrate having a sufficiently smooth flat surface was washed, and an amorphous silicon film was formed to a thickness of 500 angstroms on the surface by low pressure thermal CVD (LPCVD). (B) Next, a silicon oxide film was formed to a thickness of 700 Å by a CVD method using TEOS (tetraethoxysilane), and an opening was formed by patterning the silicon oxide film. Here, the width of the opening was 30 μm and the length was 3 cm. At the bottom of this opening, amorphous silicon is exposed.

(C) An aqueous solution of nickel acetate having a concentration of 100 ppm nickel (in terms of weight) was applied by a spin coater as shown in FIG. (D) With the nickel acetate aqueous solution attached, a heat treatment was performed in a nitrogen atmosphere at a temperature of 600 ° C. (corresponding to the first heat treatment temperature) for 8 hours. (E) The mask of the silicon oxide film was removed to obtain a crystalline silicon film having a laterally grown region.

(F) Heat treatment was performed at 950 ° C. (corresponding to the second heat treatment temperature) for 20 minutes in an oxygen atmosphere (normal pressure) containing 3% by volume of HCl. As a result, an oxide film of 200 Å was formed, and the thickness of the silicon film was 400 Å. Incidentally, as the thickness of the crystalline silicon film decreases during the formation of the thermal oxide film, silicon in an amorphous state or not completely crystallized is consumed for forming the thermal oxide film, and the crystallinity is improved. It is presumed that the deactivation of the grain boundaries progresses. Next, the oxide films formed in (G) and (F) were removed using buffered hydrofluoric acid.

〜 As is clear from FIGS. 3 and 4, it can be seen that the crystals in the crystalline silicon film according to the present invention have the following features (a) to (s). (Vi) The structure of the crystal lattice is continuous in almost a specific direction. (G) Growing into a thin rod-shaped crystal or a thin flat rod-shaped crystal. (S) A plurality of thin rod-shaped crystals or thin flat rod-shaped crystals are grown, and they are grown in parallel or almost in parallel at intervals. Further, in the photograph of FIG. 4, for example, a thin rod-like crystal having a width of about 0.15 μm extends obliquely from the lower left to the upper right, and there are clear boundaries (crystal grain boundaries) at both edges. You can see that. The reason why the light and shade such as linear shapes are observed in the photographs of FIGS. 3 and 4 is due to the difference in the orientation of the crystal plane between the rod-shaped crystals.

In this regard, the crystalline silicon films obtained in each of the examples described later were also individually observed with an optical microscope and a transmission electron microscope. ) To (S) [Some differences were observed in the diameter (width) of each crystal rod, for example, about 0.1 to 1 μm].

As described above, the crystal in the crystalline silicon film according to the present invention grows in parallel or almost in parallel when viewed macroscopically or microscopically, and has the above-mentioned features (a) to (s). have. From a different point of view, each of these crystals is a single crystal, but when viewed as an aggregate thereof, it can be said that they are a kind of polycrystal (Poly-crystal) state.

FIGS. 7A and 7B show crystal growth assumed for the crystalline silicon film obtained by the present invention based on the results observed from many micrographs represented by FIGS. Is schematically shown in FIG. First, FIG. 7A shows, as an example, a case where the amorphous silicon film is grown with a metal element that promotes crystallization of silicon is present at one end. In this case, the crystal of silicon grows linearly and in parallel or almost in parallel with the crystal lattice continuously extending from the region where the metal is added.

{Circle over (2)} FIG. 7 (b) shows a case where a metal element which promotes crystallization of silicon is grown on the entire surface of the amorphous silicon film. In this case, the crystal of silicon grows radially from the center of innumerable points on the entire surface of the amorphous silicon film, and each radial crystal grows in a rod shape with a continuous crystal lattice. Looking at the positional relationship between adjacent radial crystal rods extending from the center of each point, each crystal rod grows in parallel or almost parallel to each other. Each crystal rod is parallel or almost parallel to each other when a part of is cut.

By the way, it is effective to shorten the channel length in order to increase the operation speed of, for example, a TFT (the same applies to a general MOS type transistor, but here, a TFT is used as an example, and this is mainly described). . However, if the channel length is shortened to 1 μm or less, a disadvantage called a short channel effect occurs. Specifically, problems such as deterioration of the sub-threshold characteristic and reduction of the threshold value occur.

Here, the sub-threshold characteristic (also referred to as S value) means a rising characteristic when the TFT switch is turned ON, as schematically shown in FIG. Specifically, if the rise is steep, the subthreshold characteristic is good, and the TFT can operate at high speed. On the other hand, a TFT having a poor subthreshold characteristic has a small slope of a rising curve (= the curve is flat) and is not suitable for high-speed operation.

悪 化 The deterioration of the subthreshold characteristic due to the short channel effect can be explained as follows based on the current technical knowledge (current technical knowledge or conventional theory). First, a shorter channel means that a distance between a source region and a drain region is shorter. Generally, a channel is an intrinsic (I-type semiconductor), and a source region and a drain region are N-type or P-type. For example, if the intrinsic semiconductor and the N-type semiconductor come into contact with each other, the nature of the N-type semiconductor as a semiconductor influences the inside of the intrinsic semiconductor. This can be understood from the example of the PN junction model.

(4) In the case of a TFT, the above-mentioned influence is exerted on the inside of the channel. That is, an N-type or P-type effect is exerted from the source region and the drain region to the inside of the channel. The extent of this effect, ie the distance over which it affects, does not change as the channel becomes shorter.

(4) As the channel length becomes shorter and shorter, the influence of the source region and the drain region on the channel cannot be ignored. In an extreme case, the distance from the source region and the drain region to the inside of the channel may be longer than the channel length. In such a state, the change in the conductivity type of the channel is controlled by the application of an electric field from the gate electrode, and the conductivity of the source region and the drain changes, which hinders the operation of the TFT (the same applies to the MOS transistor). Comes out. As a result, a state in which the sub-threshold characteristic deteriorates occurs.

Therefore, from the above technical recognition (the technical knowledge at the present time or the conventional theory), it is expected that the TFT using the crystalline silicon film obtained by the present invention will naturally exhibit the short channel effect. You. However, in the TFT using the crystalline silicon film obtained according to the present invention, even if the channel length is 1 μm or less, the short channel effect does not appear, and it has been found that there is no such trouble or deterioration.

The crystal of the crystalline silicon film having the above-mentioned features (a) to (s), which is obtained by the present invention, that is, (a) a thin rod-like structure in which the (sa) crystal lattice structure is continuously connected in a substantially specific direction. In a crystal that is growing into a crystal or a thin flat rod-shaped crystal, or (s) growing into a plurality of thin rod-shaped crystals or thin flat rod-shaped crystals and they are growing parallel or almost parallel at intervals. Has not only a short channel effect but also a very good subthreshold characteristic which cannot be explained by the conventional technology recognition, and has been found to operate at a high speed corresponding to this.

Tables 1 and 2 and FIG. 9 show one example. The semiconductor device used here was manufactured by the following steps (H) to (L) generally following the step shown in FIG. These steps are illustrated in FIG. The step (G) in FIG. 6 corresponds to the step (G) in the step shown in FIG.

(H) The crystalline silicon film formed in the steps (A) to (F) was patterned to form an active layer of a thin film transistor. (I) Next, a silicon oxide film was formed as a GI film (gate insulator film) by a plasma CVD method using a mixed gas of SiH ₄ + N ₂ O as a film forming gas.

(J) Heat treatment was performed at 950 ° C. for 28 minutes in an oxygen atmosphere (normal pressure) containing 3% by volume of HCl. As a result, a 300 Å thermal oxide film was formed, and the thickness of the crystalline silicon film was 250 Å. Incidentally, as the thickness of the crystalline silicon film decreases during the formation of the thermal oxide film, silicon in an amorphous state or not completely crystallized is consumed for forming the thermal oxide film, and the crystallinity is improved. It is presumed that the deactivation of the grain boundaries progresses. In addition, the thermal oxide film formed here is formed on the surface of the active layer because oxygen molecules that have been activated enter the GI film.

An aluminum film having a thickness of 4000 angstroms was formed by (K) sputtering, and 0.18% by weight of scandium was contained in this aluminum. Further, an anodic oxide film of about 100 angstroms was formed on the surface of the aluminum film. (L) Next, a resist mask was arranged, and the aluminum film was patterned to prepare a prototype of the gate electrode.

Table 1 shows the measured values for an N-channel TFT, and Table 2 shows the measured values for a P-channel TFT. In Tables 1 and 2, the measurement points 1 to 20 mean that the measurement was performed using each part of the film surface of one batch of the crystalline silicon film manufactured as described above. First, as is clear from Table 1, when an N-channel TFT is formed, the S value (S-value) is very small, about 80 mV / decade, and the overall value is 70 to 90 mV / decade. The value falls within the range of "decade", and particularly at the measurement point 13, a small value of 72.53 mV / decade is shown.

S value (sub-threshold coefficient) is defined as the inverse of the maximum gradient in the I _D over V _G rising part of the curve as shown in FIG. 8, in other words, required gate voltage to increase the drain current by one digit It is understood that it is the increase of. That is, as the S value is smaller, the slope of the rising portion becomes steeper, the responsiveness as a switching element is excellent, and high-speed operation can be performed.

The ideal value of the S value derived from the theoretical formula is 60 mV / decade, and a value close to this value has been obtained with a transistor using a single crystal wafer until now, but a conventional TFT using a general low-temperature polysilicon has been obtained. In this case, the limit is about 300 to 500 mV / dacade. For this reason, the S value of about 80 mV / decade in the TFT using the crystalline silicon film according to the present invention is an extremely excellent characteristic, and can be said to be a surprising characteristic.

Table 2 shows actual measured values when a crystalline silicon film according to the present invention is used to form a P-channel TFT. Regarding the S value (S-value) in this case, as in the case of the N-channel type TFT, the S value is also very small in this case, about 80 mV / decade, and 70 to 100 mV / dcade as a whole. In particular, at the measurement point 4, a small value of 72.41 mV / decade is shown. The meanings of these values are the same as in the case of the above-mentioned N-channel type TFT, except that the plus (+) and the minus (-) are viewed in reverse.

ほ か In addition to the above, the meaning of each characteristic (sign) in Tables 1 and 2 is as follows. As is clear from Tables 1 and 2, all of these characteristics show values that can be sufficiently endured in practical use. Ion is a drain current that flows when the TFT is in the ON state. When VD = 1 V (1 volt), Ion-1 (note that the horizontal bar “-” in Ion-1 is usually represented in Table 1) As described below, the characters are drawn at the center of the character, and the same applies to the following symbols having a horizontal bar "-"). And The larger the Ion, the more current can flow in a short time.

Ioff is a drain current flowing when the TFT is in an OFF state, and Ioff-1 when VD = 1V (1 volt) and Ioff-2 when VD = 5V. When a current flows in the OFF state, power is consumed correspondingly. Therefore, it is extremely important to reduce Ioff. If Ioff is large, a problem arises that, for example, electric charges held in the liquid crystal flow out by Ioff. .

For Ion / Ioff-1 and Ion / Ioff-2, for example, Ion / Ioff-1 is a ratio of Ion-1 to Ioff-1, and the number of digits of the ON current and the OFF current Only different. The larger the ratio of Ion / Ioff, the better the switching characteristics and the more important it is in increasing the contrast of the panel.

Vth is a parameter generally called a threshold voltage, and is defined as, for example, a voltage at which a TFT switches to an ON state. The values in the table are values obtained by using the route ID extrapolation method when VD = 5. If Vth is large, the voltage applied to the gate electrode must be set high, which leads to an increase in drive voltage and an increase in power consumption.

ΜFE is the field-effect mobility and is also called mobility. μFE is a parameter indicating the mobility of carriers, and a TFT having a large μFE is suitable for high-speed operation. As is clear from Tables 1 and 2, all of these characteristics show values that can be sufficiently used in practical use.

Figure 9 (a) ~ (b) may choose one from the above measured data representative values is a diagram showing a graph of actually measured the I _D over V _G characteristics. 9A shows the case of an N-channel TFT, and FIG. 9B shows the case of a P-channel TFT, all showing the case where VD = 1 V (1 volt). 9A and 9B, the horizontal axis indicates the gate voltage (V), the vertical axis indicates the drain current (A), and the scale on the vertical axis ranges from “1E-13” to “1E-01”, that is, FIG. The range is 1 × 10 ^-13 to 1 × 10 ^-1 A (ampere).

First, when we have the case of the N-channel type TFT Nitsu in FIG. 9 (a), the slope of the rising portion of the I _D over V _G curve, i.e. it can be seen that the curve in the linear region is out extremely steep. This is because the characteristic corresponding to the small S value has appeared as it is, and the time to be completely ON is very short, the response as a switching element is excellent, and high-speed operation can be performed. ing. Also, in FIG. 9A, the range of the gate voltage -6 to -0.5 V is a portion corresponding to Ioff in Table 1, but the drain current flowing in the OFF state is extremely small, and this point is also excellent. It can be seen that it has the property of

Next, referring to FIG. 9B, also in the case of the P-channel TFT, the curve in the linear region is extremely steep, and the drain current flowing when in the OFF state is extremely small. Similar to the above, it shows excellent characteristics. In these technical meanings, the signs of plus (+) and minus (-) are only reversed as compared with the case of the N-channel TFT.

Tables 3 to 4 and FIG. 10 show that the second heat treatment temperature is set to be lower (700 ° C.) than in the case described above in crystallization after the application of the nickel acetate solution to the amorphous silicon film. 3) shows the case of a crystalline silicon film produced by irradiating laser light. The crystalline silicon film here is manufactured according to the manufacturing process in Example 28 described later as described in (1) to (3) below, and the semiconductor device used here is the same as the above (H) to (L). ).

That is, (1) a quartz substrate is used as a substrate, and an amorphous silicon film is formed on the surface using a plasma CVD method, and (2) a 100 ppm nickel acetate aqueous solution is applied to the entire surface of the amorphous silicon film. (The direction of crystal growth is a direction perpendicular to the film surface, that is, a vertical direction). (3) This is heated in a nitrogen atmosphere at a temperature of 600 ° C. for 4 hours, and the second heating temperature is increased. A laser beam was irradiated (the substrate was not heated at the time of the irradiation) except for the point of 700 ° C., and other steps were performed in the same manner as in Example 28.

As is clear from Tables 3 and 4, there are some differences as compared with the data in Tables 1 and 2, but also in this case, excellent characteristics including the S value are shown. a) as is clear from ~ (b), the slope of the rising portion of the I _D over V _G curve, i.e. the curve in the linear region is compared in FIG. 9 (a) ~ (b) , although the sleeping some extent, Even so, it can be seen that it is quite steep.

Next, FIG. 11A is a graph of the curves shown in FIG. 9A and FIG. 10A for the N-channel TFT. Here, the curve indicated by the symbol K in FIG. 11A corresponds to the curve in FIG. 9A, and the curve indicated by the symbol T corresponds to the curve in FIG. As is clear from FIG. 11A, the slope of the linear region is steep in all cases, but in the case of the K curve, it is steeper than in the case of the T curve, which means that the S value in the linear region is smaller. Yes, it is.

Further, looking at the ON current in the saturation region (in FIG. 11A, the region on the right side from the gate voltage value of 0.5 V (V = 0.5) on the horizontal axis: Ion), in the case of the K curve, T Larger than the curve. Further, the current in the OFF region (in FIG. 11A, the region on the left side from the vicinity of the gate voltage value −0.3 V on the horizontal axis: Ioff) is smaller in the case of the K curve than in the T curve.

FIG. 11B shows typical characteristics of a TFT using an amorphous silicon film. At this time, this is probably the ideal characteristic of a TFT using an amorphous silicon film. It is understood as a characteristic. Compared with FIG. 11 (a), in the case of the curve K, there is a marked difference between the curve (S value) in the linear region and the current value in the OFF region with respect to the curve in FIG. 11 (b). In the case of the curve T, the current value in the OFF region is almost equal to or slightly lower than the curve in FIG. 11B, but the curve (S value) in the linear region is steeper. , Indicating more excellent characteristics.

Tables 1 to 2 and FIG. 9 show crystalline silicon manufactured by setting the second heating temperature (950 ° C.) higher than the second heating temperature (700 ° C.) in the case of Tables 3 to 4 and FIG. This is the case for a membrane. Further, Tables 1 to 2 and FIG. 9 show that better characteristics including S values are obtained than Tables 3 to 4 and FIG. However, as described above, also in Tables 3 and 4 and FIG. 10, the TFT is considerably superior to the TFT which seems to use the most excellent amorphous silicon film among the conventional amorphous silicon films. It is clear that they exhibit effective characteristics.

13 (a) and 13 (b) show a nine-stage ring oscillator formed by combining a circuit combining an N-channel TFT and a P-channel TFT having the characteristics shown in FIG. This is an oscilloscope (oscillation waveform) obtained by the above. In this circuit, the N-channel TFT and the P-channel TFT work so as to complement each other at the same time, and when one TFT discharges electric charge, the other TFT operates so as to absorb electric charge.

FIG. 12 is a schematic diagram for explanation of FIG. 13. When FIG. 12 is viewed as a whole, the waveform on the + side of the oscillation waveform is mainly related to the N-channel type operation, and the waveform on the − side is the main waveform. Is related to a P-channel type operation. Therefore, when oscillation is performed at a frequency of, for example, 152.0 MHz or 252.9 MHz, if the oscillation waveform maintains symmetry between the + side and the − side, an N-channel type is obtained at that frequency. The TFT and the P-channel type TFT operate symmetrically, and operate normally with similar characteristics.

Therefore, looking at the oscilloscopes shown in FIGS. 13A and 13B, the oscillation waveform is a positive sine wave, no linear distortion is observed, and the oscilloscope is symmetrical both vertically and horizontally. As described above, according to the crystalline silicon film according to the present invention, excellent characteristics are exhibited both when it is applied as an N-channel type and when it is applied as a P-channel type. It can be seen that there is no difference in characteristics.

モ デ ル A model that can explain the above phenomena and characteristics is considered as follows. First, as shown in electron micrographs represented by FIGS. 3 and 4, the silicon semiconductor thin film constituting the TFT composed of the crystalline silicon film obtained in the present invention is oriented in a specific direction as described above. The structure has crystal continuity, and detailed observation of many samples by an electron microscope confirmed that the structure of the crystal lattice was continuous in a specific direction.

According to the above observation result, it is understood that the state is a state in which a single crystal state is continuous in a specific direction at a predetermined interval. It is understood that the carrier easily moves in a direction in which the lattice structure is continuous. That is, it is considered that in the TFT using the crystalline silicon film obtained according to the present invention, a channel region is constituted by countless elongated channels.

Here, what separates the minute channels from each other is a linear grain boundary (grain @ boundary) observed by a transmission electron microscope photograph represented in FIGS. No segregation of impurities is particularly observed at the grain boundaries.

This crystal grain boundary is an inactive grain boundary having low electrical activity, and has a structure in which a deep in-gap level does not exist or hardly exists. However, it is considered that the energy is higher than other regions due to non-uniformity and discontinuity. Therefore, it is presumed that it has a function of restricting carrier movement in a direction in which the crystal structure is continuous. Also, when such a small channel is formed, the penetration distance of the influence from the source region and the drain region to the inside of the small channel is considered to be reduced correspondingly to the narrowness. Can be

The above-mentioned electric influence is ideally analogously spread two-dimensionally or three-dimensionally isotropically, for example, as analogized from the spread of electromagnetic waves in a place where there is no obstacle. You. Considering that, in the TFT using the crystalline silicon film obtained in the present invention, a state in which a large number of minute narrow channels are formed is realized. It can be understood that the influence on the channel is suppressed, which is a suppression of the short channel effect as a whole.

Further, FIGS. 14 and 15 show diagrams in a crystalline silicon film formed using a metal element that promotes crystallization of silicon in the course of many studies and tests conducted up to the present invention. This is a measured value of a gate current value of a planar thin film transistor that the present inventors prototyped using a crystalline silicon film in which the concentration of the metal element was reduced. The difference between FIG. 14 and FIG. 15 depends on whether the thermal oxidation method or the plasma CVD method is used for forming the gate insulating film.

That is, FIG. 14 shows measured values when a gate insulating film is formed by a thermal oxide film, and FIG. 15 shows measured values when a gate insulating film is formed by a plasma CVD method. 14 and 15, the horizontal axis indicates the gate current, and the vertical axis indicates the number of measurement samples. Here, a quartz substrate was used as the substrate. The active layer was formed by a method in which a nickel element was brought into contact with the surface of the amorphous silicon film to be held and crystallized by heat treatment at 640 ° C. for 4 hours. Further, the thermal oxide film was formed in an oxygen atmosphere at a temperature of 950 ° C.

From FIG. 14, it can be seen that the gate current value varies greatly depending on the sample. This indicates that the film quality of the gate insulating film varies. On the other hand, in the thin film transistor in which the gate insulating film shown in FIG. 15 is formed by the plasma CVD method, the variation in the gate current is small and the value is extremely small. The difference between the measurement values shown in FIGS. 14 and 15 is explained as follows.

That is, in the sample in which the gate insulating film is formed with the thermal oxide film, the nickel element is sucked from the active layer into the thermal oxide film when the thermal oxide film is formed. As a result, a nickel element that inhibits the insulating property is present in the thermal oxide film. Due to the presence of the nickel element, the value of the current leaking through the gate insulating film increases, and the value varies.

This was supported by SIMS (secondary ion analysis method) by measuring the concentration of the nickel element in the gate insulating film of the sample from which the measured values in FIGS. 14 and 15 were obtained. That is, a nickel element of 10 ¹⁷ cm ⁻³ or more is measured in the gate insulating film formed by the thermal oxidation method, but the concentration of the nickel element is measured in the gate insulating film formed by the plasma CVD method. Was found to be 10 ¹⁶ cm ⁻³ or less. Note that the impurity concentration described in this specification is defined as a minimum value of a measurement value measured by SIMS (secondary ion analysis).

The above are a few examples of the findings obtained by the present inventors in the course of numerous experiments and studies carried out to confirm the characteristics, effects, etc. of the present invention. The present invention is based on such findings. The above facts are common to various aspects of the present invention.

Regardless of whether it is an amorphous silicon film or a crystalline silicon film, in a semiconductor device including a thin film transistor (such as a TFT) using a silicon film, the metal element is usually a harmful substance. The metal element needs to be removed from the silicon film as much as possible. According to the present invention, the metal elements that promote crystallization of silicon can be removed or reduced very effectively after being used for forming a crystalline silicon film.

In the present invention, by forming a thermal oxide film on the surface of a crystalline silicon film obtained by utilizing a metal element that promotes crystallization of silicon, the metal element is gettered in the thermal oxide film. As a result, the concentration of the metal element in the crystalline silicon film is reduced or the metal element is removed. According to the present invention, a semiconductor device having excellent characteristics can be obtained.

The main aspects of the inventions (1) to (6) are as follows. In the inventions (1) and (2), first, an amorphous silicon film is formed. Next, the amorphous silicon film is crystallized by the action of a metal element which promotes crystallization of silicon typified by nickel to obtain a crystalline silicon film. This crystallization is performed by a heat treatment. After this heat treatment, the crystalline silicon film contains the metal element intentionally introduced at a somewhat high concentration.

(4) The crystalline silicon film in the above state is subjected to a heat treatment in an oxidizing atmosphere to form a thermal oxide film on the surface of the crystalline silicon film. At this time, the metal element is gettered in the thermal oxide film by the action of oxygen in the oxidizing atmosphere, and the concentration of the metal element in the crystalline silicon film is reduced or the metal element is removed. . Next, the thermal oxide film on which the metal element has been gettered is removed.

に よ り By these treatments, a crystalline silicon film having high crystallinity and from which the metal element has been removed or a crystalline silicon film having a low concentration of the metal element can be obtained. The removal of the thermal oxide film can be performed using, for example, buffered hydrofluoric acid or another hydrofluoric acid-based etchant. This thermal oxide film removing process is the same as the thermal oxide film removing process in each invention described below.

In the invention (3), following the above steps, patterning is performed to form an active layer of the thin film transistor. The active layer is formed of a crystalline silicon film from which the metal element has been removed or a crystalline silicon film having a low concentration of the metal element. Next, a semiconductor device is formed by forming a thermal oxide film constituting at least a part of the gate insulating film on the surface of the active layer by thermal oxidation.

In the invention of (4), first, after forming an amorphous silicon film, a metal element for promoting crystallization of silicon is selectively introduced into the amorphous silicon film. As a mode for selectively introducing the metal element, if the mode is such that silicon can be crystallized in the amorphous silicon film in parallel with the film surface, (a) the metal element is introduced at one end of the amorphous silicon film. There are no particular restrictions on (b) introduction at one end of the amorphous silicon film at intervals, and (c) introduction of dots at intervals over the entire surface of the amorphous silicon film. It is introduced from the slit-shaped surface at an appropriate position in the film surface of the amorphous silicon film in (a) of the above-described embodiments (a) to (e). After that, crystal growth is performed by a first heat treatment in a direction parallel to the film from a region where the metal element is selectively introduced.

Next, a second heat treatment is performed in an oxidizing atmosphere to form a thermal oxide film on the surface of the region where the crystal growth has been performed. At this time, the metal element is gettered in the thermal oxide film by the action of oxygen in the oxidizing atmosphere, and the concentration of the metal element in the crystalline silicon film is reduced or the metal element is removed. . Further, the thermal oxide film is removed, and an active layer of the semiconductor device is formed using the region from which the thermal oxide film has been removed.

In any of these modes, it is preferable that the second heat treatment temperature is higher than the first heat treatment temperature. In addition, after removing the thermal oxide film, a plasma atmosphere containing oxygen and hydrogen is used. Preferably, annealing is performed. Further, the concentration of oxygen contained in the amorphous silicon film is preferably in the range of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ .

In the invention (5), a silicon oxide film or a silicon oxynitride film is first formed on a glass substrate or a quartz substrate. Next, in the same manner as described above, the semiconductor device has a crystalline silicon film sandwiched between the first and second oxide films, and the crystalline silicon film contains a metal element that promotes crystallization of silicon. In the crystalline silicon film, a semiconductor device having a high concentration distribution of the metal element near the interface with the first and / or second oxide film can be obtained. In an embodiment of the semiconductor device, the first oxide film is a silicon oxide film or a silicon oxynitride film formed over a glass substrate or a quartz substrate, and the crystalline silicon film forms an active layer of the thin film transistor. Can be formed as a silicon oxide film or a silicon oxynitride film forming a gate insulating film.

Further, in the invention of (6), similarly to the above, the base film made of the oxide film, the crystalline silicon film formed on the base film, and the thermal oxide film formed on the crystalline silicon film The crystalline silicon film contains a metal element that promotes crystallization of silicon, and the metal element that promotes crystallization of silicon is high in the vicinity of an interface with a base and / or a thermal oxide film. A semiconductor device having a concentration distribution and in which the thermal oxide film forms at least a part of the gate insulating film of the thin film transistor is obtained.

主 The main aspects of the inventions (7) to (12) are as follows. In the invention of (7), first, an amorphous silicon film is formed. To this, a metal element which promotes crystallization of silicon is intentionally introduced, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. This crystallization is performed by a heat treatment. In the state after the heat treatment, the crystalline silicon film contains the metal element. Next, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to form a thermal oxide film.

At this time, the metal element is transferred or gettered into the thermal oxide film by the action of oxygen, the action of halogen, and the action of halogen and oxygen, and at the same time, the nickel element is transferred by the action of halogen such as chlorine. Is vaporized and removed to the outside. The concentration of the metal element in the crystalline silicon film is reduced or the metal element is removed. Next, after removing the thermal oxide film formed there, a thermal oxide film is formed again by thermal oxidation on the surface of the region where the thermal oxide film has been removed.

In the invention of (8), first, an amorphous silicon film is formed. After intentionally introducing a metal element which promotes crystallization of silicon into the amorphous silicon film, the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, a second heat oxidation treatment is performed in an oxidizing atmosphere containing a halogen element to form a thermal oxide film on the surface of the crystalline silicon film, and transfer or getter the metal element to the thermal oxide film. At this time, at the same time, the nickel element is vaporized and removed to the outside by the action of halogen such as chlorine. This removes or reduces the metal element present in the crystalline silicon film. Thereafter, after removing the thermal oxide film formed there, a thermal oxide film is formed again by thermal oxidation on the surface of the region from which the thermal oxide film has been removed.

In the invention of (9), first, an amorphous silicon film is formed. After intentionally introducing a metal element that promotes crystallization of silicon into the amorphous silicon film, the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, a second heat oxidation treatment is performed in an oxidizing atmosphere containing a halogen element, and the metal element is transferred or gettered to a thermal oxide film formed at this time. By the action, the nickel element is vaporized and removed to the outside.

(4) This removes or reduces the metal element present in the crystalline silicon film. After removing the thermal oxide film formed here, patterning is performed to form an active layer of the thin film transistor, and a thermal oxide film constituting at least a part of the gate insulating film is formed on the surface of the active layer by thermal oxidation. I do.

In the invention of (10), first, an amorphous silicon film is formed. A metal element for promoting crystallization of silicon is selectively introduced into the amorphous silicon film. As a mode for selectively introducing the metal element, if the mode is such that silicon can be crystallized in the amorphous silicon film in parallel with the film surface, (a) the metal element is introduced at one end of the amorphous silicon film. There are no particular restrictions on (b) introduction at one end of the amorphous silicon film at intervals, and (c) introduction of dots at intervals over the entire surface of the amorphous silicon film. (A) of the embodiments (a) to (e), that is, from the slit-shaped surface at an appropriate position in the film surface of the amorphous silicon film. After that, crystal growth is performed by a first heat treatment in a direction parallel to the film from a region where the metal element is selectively introduced.

Next, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to form a thermal oxide film on the surface of the region where the crystal growth has been performed, and transfer or getter the metal element to the thermal oxide film. At the same time, the nickel element is vaporized and removed to the outside by the action of halogen such as chlorine. This removes or reduces the metal element present in the crystalline silicon film. Next, after removing the thermal oxide film, an active layer of a semiconductor device is formed using the region from which the thermal oxide film has been removed. The active layer is formed of a crystalline silicon film from which the metal element has been removed or a crystalline silicon film having a low concentration of the metal element.

The oxidizing atmosphere containing a halogen element in the method for manufacturing a semiconductor device described in (7) to (10) is selected from HCl, HF, HBr, Cl ₂ , F ₂ , and Br _{2 in} an O ₂ atmosphere. Alternatively, an atmosphere to which one or more kinds of gases are added can be used. As each heating temperature, it is preferable that the second heat treatment temperature is higher than the first heat treatment temperature, and annealing in a plasma atmosphere containing oxygen and hydrogen after removing the thermal oxide film is performed. preferable. Further, the concentration of oxygen contained in the amorphous silicon film is preferably in the range of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ .

In the invention of (11), first, a silicon oxide film or a silicon oxynitride film is formed on a glass substrate or a quartz substrate. Next, in the same manner as described above, the semiconductor device has a crystalline silicon film sandwiched between the first and second oxide films, and the crystalline silicon film contains a metal element that promotes crystallization of silicon. In the crystalline silicon film, a semiconductor device having a high concentration distribution of the metal element near the interface with the first and / or second oxide film can be obtained.

In this semiconductor device, a halogen element is contained in the first oxide film and / or in the vicinity of the interface between the first oxide film and the crystalline silicon film in a high concentration distribution. In the vicinity of the interface with the second oxide film, a halogen element is contained in a high concentration distribution. In this case, the first oxide film is a silicon oxide film or a silicon oxynitride film formed on a glass substrate or a quartz substrate, and the crystalline silicon film forms an active layer of the thin film transistor. Is formed of a silicon oxide film or a silicon oxynitride film constituting a gate insulating film.

In the invention of (12), in the same manner as described above, the base film made of the oxide film, the crystalline silicon film formed on the base film, and the thermal oxide film formed on the crystalline silicon film are formed. The crystalline silicon film contains a metal element which promotes crystallization of silicon, and hydrogen and a halogen element, and the metal element which promotes crystallization of silicon has an interface with a base and / or a thermal oxide film. A high concentration distribution in the vicinity, and the halogen element has a high concentration distribution in the vicinity of the interface with the base and / or the thermal oxide film, and the thermal oxide film forms at least a part of the gate insulating film of the thin film transistor. A semiconductor device is configured.

主 The main aspects of the inventions (13) to (17) are as follows. In the invention of (13), first, an amorphous silicon film is formed. A metal element which promotes the crystallization of silicon is intentionally introduced therein, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. After that, the crystalline silicon film is irradiated with laser light or strong light. Next, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the crystalline silicon film. Further, the thermal oxide film formed here is removed, and a thermal oxide film is formed on the surface of the region where the thermal oxide film has been removed by thermal oxidation again.

In the invention of (14), first, an amorphous silicon film is formed. A metal element which promotes crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. The crystalline silicon film is irradiated with laser light or intense light to diffuse the metal element present in the crystalline silicon film in the crystalline silicon film.

Next, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to transfer or getter the metal element present in the crystalline silicon film into the thermal oxide film to be formed. The thermal oxide film formed here is removed, and a thermal oxide film is formed again by thermal oxidation on the surface of the region where the thermal oxide film has been removed.

In the invention of (15), first, an amorphous silicon film is formed. A metal element for promoting crystallization of silicon is intentionally and selectively introduced into the amorphous silicon film. As a mode for selectively introducing the metal element, if the mode is such that silicon can be crystallized in the amorphous silicon film in parallel with the film surface, (a) the metal element is introduced at one end of the amorphous silicon film. There are no particular restrictions on (b) introduction at one end of the amorphous silicon film at intervals, and (c) introduction of dots at intervals over the entire surface of the amorphous silicon film. It is introduced from the slit-shaped surface at an appropriate position in the film surface of the amorphous silicon film in (a) of the above-described embodiments (a) to (e).

(4) Thereafter, a first heat treatment is performed on the amorphous silicon film to cause crystal growth from a region where the metal element is selectively introduced in a direction parallel to the film. Next, irradiation with laser light or strong light is performed to diffuse the metal element present in the crystal grown region. Further, the second heat treatment is performed in an oxidizing atmosphere containing a halogen element, and the metal element present in the region where the crystal has been grown is transferred or transferred into the thermal oxide film formed by the second heat treatment. Gettering. Next, after removing the thermal oxide film formed here, a thermal oxide film is formed again by thermal oxidation on the surface of the region where the thermal oxide film has been removed.

In the above inventions (13) to (15), it is preferable that the second processing temperature is higher than 600 ° C. and lower than 750 ° C., and that the gate insulating film is formed again by using a thermal oxide film. Preferably, it is formed. In these inventions, as the oxidizing atmosphere containing a halogen element, one or a plurality of gases selected from HCl, HF, HBr, Cl ₂ , F ₂ and Br ₂ are added to an O ₂ atmosphere. Atmosphere is used.

Furthermore, in these inventions (13) to (15), the second heat treatment temperature is preferably higher than the first heat treatment temperature, and oxygen and hydrogen are removed after removing the thermal oxide film. Annealing can be performed in a plasma atmosphere including the above. In these inventions, the concentration of oxygen contained in the amorphous silicon film is preferably in the range of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ .

In the invention of (16), first, an amorphous silicon film is formed. After intentionally introducing a metal element that promotes crystallization of silicon into the amorphous silicon film, the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, the crystalline silicon film is patterned to form an active layer of the semiconductor device, and the active layer is irradiated with laser light or strong light. After that, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the active layer. Subsequently, the thermal oxide film formed here is removed, and a thermal oxide film is formed on the surface of the active layer by thermal oxidation again.

In the invention of (17), first, an amorphous silicon film is formed. A metal element that promotes crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. The crystalline silicon film is patterned to form an active layer of a semiconductor device, and the active layer is irradiated with laser light or strong light. Next, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the active layer. Thereafter, the thermal oxide film formed here is removed, and a thermal oxide film is formed on the surface of the active layer by thermal oxidation again. At this time, the active layer is configured such that the side surface has an inclined shape having an angle of 20 ° to 50 ° with the base surface.

In the inventions (16) and (17), the gate insulating film can be formed by using the thermal oxide film again. The upper limits of the first heat treatment temperature and the second heat treatment temperature are preferably 750 ° C. or less, and the oxidizing atmosphere containing a halogen element is preferably HCl, HF, or O ₂ atmosphere. An atmosphere to which one or more gases selected from HBr, Cl ₂ , F ₂ and Br ₂ are added is used.

Further, in these inventions, the second heat treatment temperature is preferably higher than the first heat treatment temperature, and annealing is performed in a plasma atmosphere containing oxygen and hydrogen after removing the thermal oxide film. be able to. The concentration of oxygen contained in the amorphous silicon film is preferably in the range of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ .

主 The main aspects of the inventions (18) to (22) are as follows. In the invention of (18), first, an amorphous silicon film is formed. A metal element which promotes crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, the crystalline silicon film is irradiated with laser light or strong light, and a second heat treatment is performed in an oxidizing atmosphere to remove or reduce the metal element present in the crystalline silicon film. . Thereafter, the thermal oxide film formed in the step is removed, and a thermal oxide film is formed on the surface of the region where the thermal oxide film has been removed by thermal oxidation again.

In the invention of (19), first, an amorphous silicon film is formed. After intentionally introducing a metal element that promotes crystallization of silicon into the amorphous silicon film, the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, the crystalline silicon film is irradiated with laser light or strong light, whereby the metal element present in the crystalline silicon film is diffused in the crystalline silicon film. After that, a second heat treatment is performed in an oxidizing atmosphere to transfer or getter the metal element present in the crystalline silicon film into the formed thermal oxide film. Further, after removing the thermal oxide film formed here, a thermal oxide film is formed again by thermal oxidation on the surface of the region where the thermal oxide film has been removed.

In the invention of (20), first, an amorphous silicon film is formed. A metal element for promoting crystallization of silicon is intentionally and selectively introduced into the amorphous silicon film. As a mode for selectively introducing the metal element, if the mode is such that silicon can be crystallized in the amorphous silicon film in parallel with the film surface, (a) the metal element is introduced at one end of the amorphous silicon film. There are no particular restrictions on (b) introduction at one end of the amorphous silicon film at intervals, and (c) introduction of dots at intervals over the entire surface of the amorphous silicon film. It is introduced from the slit-shaped surface at an appropriate position in the film surface of the amorphous silicon film in (a) of the above-described embodiments (a) to (e).

(4) Next, a first heat treatment is performed on the amorphous silicon film, and crystal growth is performed in a direction parallel to the film from the region where the metal element is intentionally and selectively introduced. Thereafter, irradiation with laser light or strong light is performed to diffuse the metal element present in the region where the crystal has grown. Next, a second heat treatment is performed in an oxidizing atmosphere to transfer or getter the metal element present in the crystal grown region into a thermal oxide film formed by the second heat treatment. Further, the thermal oxide film formed here is removed, and a thermal oxide film is formed on the surface of the region where the thermal oxide film has been removed by thermal oxidation again.

In the inventions of (18) to (20), the second heat treatment is preferably performed at a temperature of more than 600 ° C. and 750 ° C. or less. Can be formed. In these inventions, it is preferable that the second heat treatment temperature is higher than the first heat treatment temperature. Further, in these inventions, after removing the thermal oxide film, annealing in a plasma atmosphere containing oxygen and hydrogen can be performed. The concentration of oxygen contained in the amorphous silicon film is preferably in the range of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ .

In the invention of (21), first, an amorphous silicon film is formed. A metal element which promotes crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, the crystalline silicon film is patterned to form an active layer of the semiconductor device, and the active layer is irradiated with laser light or strong light. After that, a second heat treatment is performed in an oxidizing atmosphere to remove or reduce the metal element present in the active layer. Next, the thermal oxide film formed here is removed, and a thermal oxide film is formed on the surface of the active layer by thermal oxidation again.

In the invention of (22), first, an amorphous silicon film is formed. After intentionally introducing a metal element that promotes crystallization of silicon into the amorphous silicon film, the amorphous silicon film is crystallized by a first heat treatment to obtain a crystalline silicon film. Next, the crystalline silicon film is patterned to form an active layer of the semiconductor device, and the active layer is irradiated with laser light or strong light. After that, a second heat treatment is performed in an oxidizing atmosphere to remove or reduce the metal element present in the active layer. The thermal oxide film formed here is removed, and a thermal oxide film is formed on the surface of the active layer by thermal oxidation again. At this time, the side surface of the active layer is formed to have an inclined shape having an angle of preferably 20 ° to 50 ° with the base surface.

In the inventions (21) and (22), the gate insulating film can be formed by using the thermal oxide film again. The second treatment temperature is preferably higher than 600 ° C. and not higher than 750 ° C., and the second heat treatment temperature is preferably higher than the first heat treatment temperature. Further, in these inventions, it is preferable to perform annealing in a plasma atmosphere containing oxygen and hydrogen after removing the thermal oxide film, and the concentration of oxygen contained in the amorphous silicon film is 5 × 10 ¹⁷ cm ⁻ It is preferably in the range of ^{3 to} 2 × 10 ¹⁹ cm ⁻³ .

主 The main aspects of the inventions (23) to (25) are as follows. In the invention (23), first, an amorphous silicon film is formed on a substrate having an insulating surface, and a metal element that promotes crystallization of silicon is intentionally introduced into the amorphous silicon film. Next, after the amorphous silicon film is crystallized by a first heat treatment at a temperature of 750 ° C. to 1100 ° C. to obtain a crystalline silicon film, the crystalline silicon film is patterned to form an active layer of a semiconductor device. .

(4) Thereafter, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to remove or reduce the metal element present in the active layer. The thermal oxide film formed here is removed, and after removing the thermal oxide film, a thermal oxide film is formed by thermal oxidation again. At this time, preferably, the temperature of the second heat treatment is higher than the temperature of the first heat treatment.

In the invention of (24), after an amorphous silicon film is first formed on a substrate having an insulating surface, a metal element which promotes crystallization of silicon is intentionally introduced into the amorphous silicon film. Next, the amorphous silicon film is crystallized by a first heat treatment at a temperature of 750 ° C. to 1100 ° C. to obtain a crystalline silicon film. Then, after patterning the crystalline silicon film to form an active layer of the semiconductor device, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to remove the metal element present in the active layer. Is transferred or gettered into the thermal oxide film formed by the second heat treatment. Next, after removing the thermal oxide film formed in the step, a thermal oxide film is formed by thermal oxidation again. At this time, preferably, the temperature of the second heat treatment is set to be higher than the temperature of the first heat treatment.

In the invention of (25), first, an amorphous silicon film is formed on a substrate having an insulating surface, and a metal element for promoting crystallization of silicon is intentionally and selectively introduced into the amorphous silicon film. . As a mode for selectively introducing the metal element, if the mode is such that silicon can be crystallized in the amorphous silicon film in parallel with the film surface, (a) the metal element is introduced at one end of the amorphous silicon film. There are no particular restrictions on (b) introduction at one end of the amorphous silicon film at intervals, and (c) introduction of dots at intervals over the entire surface of the amorphous silicon film. It is introduced from the slit-shaped surface at an appropriate position in the film surface of the amorphous silicon film in (a) of the above-described embodiments (a) to (e).

Next, by a first heat treatment at a temperature of 750 ° C. to 1100 ° C., crystal growth is performed in a direction parallel to the film from a region of the amorphous silicon film into which the metal element is intentionally and selectively introduced. Next, patterning is performed to form an active layer of the semiconductor device using the region where the crystal has grown in a direction parallel to the film. After that, a second heat treatment is performed in an oxidizing atmosphere containing a halogen element to transfer or getter the metal element present in the active layer into the thermal oxide film formed by the second heat treatment. Let it ring. Further, after removing the thermal oxide film, a thermal oxide film is formed by thermal oxidation again. At this time, preferably, the temperature of the second heat treatment is set to be higher than the temperature of the first heat treatment.

As described above, in the inventions (23) to (25), a quartz substrate is preferably used as a substrate on which an amorphous silicon film is formed, and a gate insulating film is formed using a thermal oxide film again. Furthermore, in the inventions (23) to (25), annealing can be performed in a plasma atmosphere containing oxygen and hydrogen after the removal of the thermal oxide film, and the concentration of oxygen contained in the amorphous silicon film is reduced. It is preferably in the range of 5 × 10 ¹⁷ cm ^{−3 to} 2 × 10 ¹⁹ cm ⁻³ .

主 The main aspects of the inventions (26) to (29) are as follows. In the invention (26), first, an amorphous silicon film is formed. After a metal element that promotes crystallization of silicon is in contact with and held on the surface of the amorphous silicon film, a first heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film. Next, a second heat treatment is performed at a temperature of 500 ° C. to 700 ° C. in an atmosphere containing oxygen, hydrogen, and fluorine to form a thermal oxide film on the surface of the crystalline silicon film. Is removed.

In the invention of (27), first, an amorphous silicon film is formed. After a metal element that promotes crystallization of silicon is brought into contact with and held on the surface of the amorphous silicon film, a first heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film. Next, a second heat treatment is performed at a temperature of 500 ° C. to 700 ° C. in an atmosphere containing oxygen, hydrogen, fluorine, and chlorine to form a thermal oxide film on the surface of the crystalline silicon film. Remove the film.

In the invention of (28), first, an amorphous silicon film is formed. After a metal element that promotes crystallization of silicon is in contact with and held on the surface of the amorphous silicon film, heat treatment is performed to crystallize the amorphous silicon film to obtain a crystalline silicon film. Next, after forming a wet oxide film on the surface of the crystalline silicon film in an atmosphere containing fluorine and / or chlorine, the oxide film is removed.

In the inventions of (26) to (28), the concentration of the metal element in the oxide film is preferably higher than the concentration of the metal element in the crystalline silicon film. Further, it is preferable that hydrogen be contained in an atmosphere in which the second heat treatment is performed at a concentration of 1% by volume or more and less than an explosion limit. Further, the first heat treatment is preferably performed in a reducing atmosphere, and the crystalline silicon film can be irradiated with laser light after the first heat treatment.

The invention of (29) relates to a semiconductor device having a crystalline silicon film, wherein the silicon film contains a metal element for promoting crystallization of silicon in a range of 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁸ cm ^{−. 3} and fluorine atoms are contained at a concentration of 1 × 10 ¹⁵ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ , and hydrogen atoms are contained at a concentration of 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ²¹ cm ⁻³ . A semiconductor device characterized by being contained at a concentration. This semiconductor device can be manufactured by the manufacturing method described in the above (26) to (28). Further, the silicon film in the semiconductor device is preferably formed over an insulating film, and fluorine atoms are preferably present in a high concentration distribution near an interface between the insulating film and the silicon film.

主 The main aspects of the inventions (30) to (33) are as follows. In the invention of (30), first, an amorphous silicon film is formed, and the amorphous silicon film is crystallized to form a crystalline silicon film. Next, the crystalline silicon film is heated in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film. Remove. After that, a semiconductor device is manufactured by depositing an insulating film on the surface of the crystalline silicon film.

In the invention of (31), an amorphous silicon film is formed, and the amorphous silicon film is irradiated with a laser beam and crystallized to form a crystalline silicon film. Next, the crystalline silicon film is heated in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film. Remove. After that, a semiconductor device is manufactured by depositing an insulating film on the surface of the crystalline silicon film.

The invention of (32) is a method for manufacturing a thin film transistor over a substrate having an insulating surface. First, an amorphous silicon film is formed, and the amorphous silicon film is crystallized to form a crystalline silicon film. Thereafter, the crystalline silicon film is heated in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film, and then the thermal oxide film on the crystalline silicon film surface is removed.

Next, after shaping the crystalline silicon film to form an active layer of a thin film transistor, an insulating film is deposited on the surface of the active layer, and a gate insulating film is formed at least on the surface of the channel region. Further, a gate electrode is formed on the surface of the gate insulating film, impurity ions for imparting a conductivity type are implanted into the active layer using the gate electrode as a mask, and a source and a drain are formed in a self-aligned manner. Make the device.

The invention of (33) is a method for manufacturing a thin film transistor on a substrate having an insulating surface. First, an amorphous silicon film is formed, and the amorphous silicon film is crystallized to form a crystalline silicon film. Next, after irradiating the crystalline silicon film with a laser beam, the crystalline silicon film is heated in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film. The thermal oxide film on the surface is removed.

Next, the crystalline silicon film is shaped to form an active layer of a thin film transistor, an insulating film is deposited on the surface of the active layer, and a gate insulating film is formed on at least the surface of the channel region. A gate electrode is formed on the surface of the substrate. Further, a semiconductor device is manufactured by implanting impurity ions imparting a conductivity type into the active layer using the gate electrode as a mask to form a source and a drain in a self-aligned manner.

In the above inventions (30) to (33), the thermal oxide film preferably has a thickness of 200 to 500 Å, and the metal element is added to the amorphous silicon film after the step of forming the amorphous silicon film. Is preferably added at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ . Further, a metal element is preferably used in forming the crystalline silicon film, and the metal element is at least one selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Cu, and Au. Can be used. This is the same in the case of the above-described invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. First, as Examples 1 to 3, an example showing the effect of removing or reducing the metal element and the halogen concentration in a crystalline silicon film crystallized by the action of the metal element using the metal element will be described. Then, embodiments corresponding to the inventions of the above (1) to (33) are sequentially described.

<< Example 1 >>
FIG. 16 shows the result of measuring the concentration distribution of nickel element in the cross-sectional direction of the film when the amorphous silicon film is crystallized by using nickel as the metal element and a thermal oxide film is formed. This measurement was performed by SIMS (secondary ion analysis method). The process of preparing a sample that has obtained the measured values is as follows.

(4) After forming a silicon oxide film as a base film to a thickness of 4000 angstroms on a quartz substrate, an amorphous silicon film was formed to a thickness of 500 angstroms by a low pressure thermal CVD method. Next, a nickel element was introduced into the amorphous silicon film using an aqueous solution of nickel acetate. Further, the resultant was crystallized by a heat treatment at a temperature of 650 ° C. for 4 hours to obtain a crystalline silicon film. Thereafter, a heat treatment was performed in an oxygen atmosphere at a temperature of 950 ° C. to form a thermal oxide film having a thickness of 700 Å.

As apparent from FIG. 16, the nickel element migrates from the crystalline silicon film (Poly-Si film) to the silicon oxide film (thermal oxide film) and is included in the thermal oxide film. The nickel element is relatively larger in the crystalline silicon film than in the thermal oxide film, which is understood as a result of the large amount of O taken in as SiO _{2 in the} thermal oxide film. The high concentration of the nickel element on the surface of the thermal oxide film is understood to be a measurement error affected by the surface state due to surface irregularities or adsorbed substances. Absent. For the same reason, data near the interface also includes some errors.

<< Example 2 >>
Next, as a method of forming a thermal oxide film, a heat treatment is performed in an oxygen atmosphere containing 950 ° C. and 3% by volume of HCl, and the other steps are the same as those in the first embodiment, and the thickness is 500 Å. A thermal oxide film was formed. FIG. 17 shows measurement data of the sample in this case. As is clear from FIG. 17, the nickel concentration in the crystalline silicon film further decreases, and instead, the nickel concentration in the thermal oxide film relatively increases. This means that the nickel element was further sucked out (that is, gettered) in the formed thermal oxide film.

A difference between FIG. 16 and FIG. 17 is only whether or not HCl is contained in the atmosphere when the oxide film is formed. Therefore, it can be concluded that the above-mentioned gettering effect largely depends on HCl in addition to oxygen. Further, since the gettering effect by H (hydrogen), which is a component of HCl, has not been confirmed, the gettering effect as shown in the difference between FIG. 16 and FIG. It can be seen that it can be obtained.

(4) By removing the thermal oxide film obtained by gettering the nickel element, a crystalline silicon film having a low nickel concentration can be obtained. FIG. 18 is a graph showing a Cl element concentration distribution in a sample manufactured under the same conditions as the sample from which the data in FIG. 17 was obtained. As is clear from FIG. 18, the Cl element is concentrated near the interface between the crystalline silicon film and the thermal oxide film.

<< Example 3 >>
In the third embodiment, an amorphous silicon film formed by a plasma CVD method is used instead of the amorphous silicon film which is the starting film of the crystalline silicon film from which the data described in the first and second embodiments is obtained. This is an example in which a film is used, and other manufacturing conditions are the same as those in Example 1. Since the amorphous silicon film formed by the plasma CVD method has a different film quality from the amorphous silicon film formed by the low pressure thermal CVD method, gettering action after forming the crystalline silicon film is also reduced. Will be different.

First, FIG. 19 shows measurement data of a sample when a thermal oxide film is formed in an oxygen atmosphere at a temperature of 950 ° C. As is clear from FIG. 19, although the nickel element is also transferred to the thermal oxide film, the nickel element is present at a relatively high concentration in the crystalline silicon film. Although the conditions for introducing nickel are the same, the nickel concentration in the crystalline silicon film is higher than that in FIG. This is presumably because the amorphous silicon film formed by the plasma CVD method is not dense and has many defects, so that the nickel element is more easily diffused into the film.

と Looking at the above facts from another point of view, we can take the following different perspectives. That is, before applying the nickel acetic acid aqueous solution, an extremely thin oxide film was formed on the surface of the amorphous silicon film by a UV (ultraviolet) oxidation method in order to improve the wettability. It may be different due to the influence of the film quality of the underlying amorphous silicon film. In this case, the amount of the nickel element diffused in the silicon film varies depending on the difference in the film thickness, and therefore, it can be considered that the influence appears in the difference between FIG. 16 and FIG.

{Circumflex over (2)} FIG. 20 shows data obtained when HCl was contained at 1% by volume with respect to oxygen as the atmosphere when the thermal oxide film was formed. As is clear from FIG. 20, the nickel concentration in the crystalline silicon film is further reduced as compared with the data shown in FIG. Correspondingly, the nickel concentration in the thermal oxide film has increased.

This fact means that the nickel element was gettered in the thermal oxide film by the action of chlorine. As described above, by forming the thermal oxide film in an oxidizing atmosphere containing chlorine, the nickel element present in the crystalline silicon film in the thermal oxide film can be more effectively gettered. Then, by removing the thermal oxide film obtained by gettering the nickel element, a crystalline silicon film having a low nickel concentration can be obtained.

Further, the graph shown in FIG. 21 is a result of examining the chlorine concentration in a sample obtained under the same manufacturing conditions as the sample from which the data shown in FIG. 20 was obtained. As is clear from FIG. 21, chlorine exists at a high concentration near the interface between the base film and the crystalline silicon film and near the interface between the crystalline silicon film and the thermal oxide film. FIG. 21 corresponds to FIG. 18, but the distribution of chlorine concentration is formed as shown in FIG. 21 because the amorphous silicon film as the starting film is formed by the plasma CVD method and the film quality is It is presumed to be due to the lack of precision.

20. Further, as is clear from FIG. 20, in this case, the nickel concentration tends to be high also in the vicinity of the interface between the base film and the crystalline silicon film. This is understood to be the result of nickel gettering toward the base film by the action of chlorine existing near the interface with the base film (or in the base film). It is considered that such a phenomenon can be obtained even when a halogen element is added to the base film.

The effects demonstrated in Examples 1 to 3 can be more effectively performed depending on the transfer of the metal element to the thermal oxide film, gettering conditions, and the like according to the present invention. Hereinafter, Examples corresponding to the inventions (1) to (33) will be described, appropriately including modifications and the like.

<< Example 4 >>
Example 4 is an example in which a crystalline silicon film was obtained on a glass substrate by using a nickel element. First, a crystalline silicon film having high crystallinity was obtained by the action of the nickel element. Next, a film was formed on the crystalline silicon film by a thermal oxidation method. At this time, the nickel element remaining in the crystalline silicon film is gettered in the thermal oxide film. Next, as a result of the gettering, the thermal oxide film containing the nickel element at a high concentration was removed. Thus, a crystalline silicon film having high crystallinity and a low concentration of nickel element on a glass substrate was obtained.

FIG. 22 is a diagram illustrating a manufacturing process in the fourth embodiment. First, a silicon oxynitride film 2 having a thickness of 3000 Å was formed as a base film on a Corning 1737 glass substrate (strain point: 667 ° C.) 1. The silicon oxynitride film is formed by, for example, a plasma CVD method using silane, N ₂ O gas, and oxygen as source gases, or a plasma CVD method using TEOS gas and N ₂ O gas. However, the former was used here.

This silicon oxynitride film has a function of suppressing the diffusion of impurities from a glass substrate (a glass substrate contains a large amount of impurities at a semiconductor manufacturing level) in a later step. . As the base film, a silicon oxide film can be used instead of the silicon oxynitride film. Note that a silicon nitride film is optimal for maximizing the function of suppressing the diffusion of the impurity, but the silicon nitride film is peeled off from the glass substrate due to stress. is not.

(4) It is important that the undercoat film 2 has as high a hardness as possible. This is concluded from the fact that in a durability test of the finally obtained thin film transistor, the higher the hardness of the base film (that is, the lower the etching rate), the higher the reliability. Although the reason for this is not known in detail, it is presumed to be due to the effect of shielding impurities from the glass substrate during the manufacturing process of the thin film transistor.

(4) It is effective that the base film 2 contains a trace amount of a halogen element typified by chlorine. By doing so, in a later step, a metal element that promotes crystallization of silicon present in the semiconductor layer can be gettered by the halogen element. It is effective to apply hydrogen plasma treatment after forming the base film, and it is effective to perform plasma treatment in an atmosphere in which oxygen and hydrogen are mixed. These treatments are effective in removing carbon components adsorbed on the surface of the base film and improving interface characteristics with a semiconductor film to be formed later.

Next, an amorphous silicon film 3 to be a crystalline silicon film later was formed to a thickness of 500 angstroms by a low pressure thermal CVD method. The reason why the reduced pressure thermal CVD method is used here is that the crystalline silicon film obtained later is excellent in film quality, and specifically, the film quality is dense. As a method other than the low pressure thermal CVD method, a plasma CVD method or the like can be used. The amorphous silicon film manufactured here preferably has an oxygen concentration in the film of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ . This is because oxygen plays an important role in a later step of a metal element gettering step that promotes crystallization of silicon.

However, care must be taken when the oxygen concentration is higher than the above concentration range, because crystallization of the amorphous silicon film is hindered. The concentration of another impurity, for example, the concentration of nitrogen or carbon is preferably as low as possible. Specifically, the concentration needs to be 2 × 10 ¹⁹ cm ⁻³ or less. Here, the thickness of the amorphous silicon film 3 was 1600 Å. The thickness of the amorphous film needs to be larger than the finally required thickness.

When the amorphous silicon film 3 is crystallized only by heating, the thickness of the starting film (amorphous silicon film) 3 is set to 800 Å to 5000 μm, preferably 1500 to 3000 Å. If the thickness is larger than this range, the film formation time becomes longer, which is uneconomical in terms of production cost. If the thickness is smaller than this range, the crystallization becomes uneven or the reproducibility of the process becomes poor. Thus, the state shown in FIG. 20A was obtained. Next, a nickel element is introduced to crystallize the amorphous silicon film 3. Here, the nickel element was introduced by applying a nickel acetate aqueous solution containing 10 ppm (weight conversion) of nickel to the surface of the amorphous silicon film 3.

As a method for introducing the nickel element, a sputtering method, a CVD method, a plasma processing method, or an adsorption method can be used in addition to the method using a nickel salt solution as described above. Among them, the method using a solution is simple and useful in that the concentration of the metal element is easily adjusted. Various nickel salts can be used as the nickel salt. As the solvent, water, alcohols or other organic solvents, or a mixed solvent of water and an organic solvent can be used as the solvent.

In this example, the water film 4 was formed as shown in FIG. 22B by applying the nickel acetate solution as described above. In this state, an excess solution was blown off using a spin coater (not shown). In this way, the state is such that the nickel element is held in contact with the surface of the amorphous silicon film 3. In consideration of the residual impurities in the subsequent heating step, it is preferable to use a solution containing a nickel salt containing no carbon, for example, a nickel sulfate solution instead of using a nickel acetate solution. The reason for this is that the nickel acetate salt solution contains carbon, which may be carbonized in the subsequent heating step and remain in the film. The introduction amount of the nickel element can be adjusted by adjusting the concentration of the nickel salt in the solution.

Next, in the state shown in FIG. 22C, heat treatment was performed at a temperature of 450 ° C. to 650 ° C. to crystallize the amorphous silicon film 3 and obtain a crystalline silicon film 5. This heat treatment is performed in a reducing atmosphere. Here, heat treatment was performed at 620 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen. Thus, a crystalline silicon film 5 was obtained as shown in FIG. The reason why the atmosphere is set to the reducing atmosphere in the crystallization step by the heat treatment is to prevent oxides from being formed during the heat treatment step, and more specifically, nickel and oxygen react with each other. NiO _X is to suppress the undesirably formed on the surface of the film or within the film to.

By the way, in the later gettering step, oxygen combines with nickel and makes a great contribution to gettering of nickel. However, it has been found that the combination of oxygen and nickel in the crystallization step inhibits crystallization. Therefore, in the step of crystallization by heating, it is important to suppress the formation of oxides as much as possible. The oxygen concentration in the atmosphere in which the heat treatment for crystallization is performed needs to be on the order of ppm, preferably 1 ppm or less.

As a gas occupying most of the atmosphere in which the heat treatment for crystallization is performed, an inert gas such as nitrogen or argon, or a mixed gas thereof can be used. Using. In addition, the lower limit of the heat treatment temperature for the crystallization is preferably 450 ° C. or higher in view of its effect and reproducibility. On the other hand, the upper limit is preferably lower than the strain point of the glass substrate to be used. In this embodiment, a Corning 1737 glass substrate having a strain point of 667 ° C. is used. Degree.

In this regard, if a quartz substrate is used as the substrate, the heating temperature can be further increased to about 900 ° C. or higher. In this case, a crystalline silicon film having higher crystallinity can be obtained, and a crystalline silicon film can be obtained in a shorter time. After the crystalline silicon film 5 was obtained, another heat treatment was performed. This heat treatment is performed to form a thermal oxide film containing a nickel element. Here, this heat treatment was performed in an atmosphere of 100% oxygen.

FIG. 22D is a view for explaining this heat treatment step. This step is for removing the nickel element (other metal elements that promote crystallization of silicon) intentionally mixed in the initial stage for crystallization from the crystalline silicon film 5. This heat treatment is performed at a higher temperature than the heat treatment performed for performing the above-described crystallization. This is an important condition for effective gettering of the nickel element.

This heat treatment is performed at a temperature of 550 ° C. to 1050 ° C., preferably 600 ° C. to 980 ° C., after satisfying the above conditions. This is because the effect cannot be obtained at a temperature of 600 ° C. or less, and conversely, at a temperature of 1050 ° C. or more, a jig made of quartz is distorted or a load is imposed on the apparatus (in this sense, the temperature is 980 ° C. Is preferable). The upper limit of the heat treatment temperature is limited by the strain point of the glass substrate used. It is necessary to pay attention to heat treatment at a temperature higher than the strain point of the glass substrate to be used, since the substrate is deformed.

加熱 In this example, the heating temperature was 640 ° C. because a Corning 1737 glass substrate having a strain point of 667 ° C. was used. When the heat treatment is performed under such conditions, a thermal oxide film 6 is formed as shown in FIG. Here, a heat treatment was performed for 12 hours to form a thermal oxide film 6 having a thickness of 200 angstroms. By forming the thermal oxide film 6, the thickness of the crystalline silicon film 3 becomes about 1500 angstroms. In this heat treatment, when the heating temperature is 600 ° C. to 750 ° C., the treatment time (heating time) is about 10 hours to 48 hours, typically 24 hours. When the heating temperature is 750 ° C. to 900 ° C., the processing time is about 5 hours to 24 hours, typically 12 hours.

(4) When the heating temperature is in the range of 900 ° C. to 1050 ° C., the treatment time is about 1 hour to 12 hours, typically 6 hours. Needless to say, these processing times are appropriately set depending on the thickness of the oxide film to be obtained. In this step, the nickel element is gettered in the thermal oxide film 6 to be formed. In this gettering, oxygen present in the crystalline silicon film plays an important role in addition to the oxygen atmosphere. In other words, nickel oxide is formed by the combination of oxygen and nickel, and the nickel element is gettered in the thermal oxide film 6 in this form.

As described above, if the concentration of oxygen is too large, it becomes an element that hinders crystallization of the amorphous silicon film 3 in the crystallization step shown in FIG. However, as described above, its presence plays an important role in the nickel gettering process. Therefore, it is important to control the concentration of oxygen existing in the amorphous silicon film serving as the starting film. Through this step, the nickel element in the crystalline silicon film 5 can be removed or its concentration can be made lower than the initial concentration.

In addition, in the above process, since the nickel element is gettered in the oxide film to be formed, the nickel concentration in the oxide film naturally becomes higher than in other regions. In addition, it was observed that the nickel element tended to increase near the silicon film 5 side at the interface between the silicon film 5 and the oxide film 6. This is probably because the region where gettering is mainly performed is on the oxide film side near the interface between the silicon film and the oxide film. It is considered that the gettering proceeds in the vicinity of the interface due to the presence of stress and defects in the vicinity of the interface, and furthermore, to the organic matter.

(4) After the formation of the thermal oxide film 6, the thermal oxide film 6 containing nickel at a high concentration was removed. The removal of the thermal oxide film 6 is performed by, for example, wet etching or dry etching using buffered hydrofluoric acid (other hydrofluoric acid-based etchant). In this case, the former is applied. Thus, as shown in FIG. 22E, a crystalline silicon film 7 having a reduced nickel content was obtained. In the vicinity of the surface of the obtained crystalline silicon film 7, a relatively high concentration of nickel element is contained. Therefore, the etching of the thermal oxide film 6 is further advanced, and the surface of the crystalline silicon film 7 is slightly reduced. Over-etching is effective.

<< Example 5 >>
Example 5 is different from the structure shown in Example 4 in the case where a crystalline silicon film was obtained by the heat treatment shown in FIG. 22C and further irradiated with laser light to promote the crystallinity. Here is an example. This is necessary when the temperature of the heat treatment shown in FIG. 22C is low or the treatment time is short, that is, when the heating temperature is limited or the heating time is limited because of a manufacturing process. Crystallinity may not be obtained. In such a case, the required high crystallinity can be obtained by performing annealing by laser light irradiation.

(4) In this case, laser light irradiation allows a wider range of allowable laser irradiation conditions and higher reproducibility as compared with the case where the amorphous silicon film is directly crystallized. Irradiation with laser light may be performed after the step illustrated in FIG. It is important that the thickness of the amorphous silicon film 3 serving as a starting film formed in FIG. 22A be 200 Å to 2000 Å. This is because the smaller the thickness of the amorphous silicon film, the higher the annealing effect by laser light irradiation.

The laser beam to be used is not particularly limited, but preferably a laser beam in the ultraviolet region, for example, an excimer laser in the ultraviolet region. Specifically, a KrF excimer laser (wavelength 248 nm), a XeCl excimer laser (wavelength 308 nm), or the like can be used. In this embodiment, a KrF excimer laser (wavelength 248 nm) is used. Annealing can also be performed by irradiating with strong light using an ultraviolet lamp or an infrared lamp instead of laser light.

<< Example 6 >>
The sixth embodiment is an example in which an infrared lamp is used instead of the laser beam in the fifth embodiment. When infrared rays are used, the silicon film can be selectively heated without heating the glass substrate much. Therefore, an effective heat treatment could be performed without thermally damaging the glass substrate.

<< Example 7 >>
Example 7 is an example in which Cu is used as a metal element for promoting crystallization of silicon in the configuration shown in Example 4. In the case of a copper element, as a solution for introducing Cu, for example, a solution such as cupric acetate [Cu (CH ₃ COO) ₂ ] or cupric chloride (CuCl ₂ 2H ₂ O) may be used. In this embodiment, an aqueous solution of cupric acetate [Cu (CH ₃ COO) ₂ ] was used.

<< Embodiment 8 >>
The eighth embodiment is an example in which a quartz substrate is used as the substrate 1 in the configuration shown in the fourth embodiment. In this embodiment, the thickness of the amorphous silicon film 3 serving as a starting film is set to 2000 Å. The heating temperature during the formation of the thermal oxide film by the heat treatment shown in FIG. In this case, since the oxide film is formed quickly and the effect of gettering cannot be sufficiently obtained, the oxygen concentration in the atmosphere is reduced. Specifically, the oxygen concentration in the nitrogen atmosphere was set to 10% by volume.

上 記 The processing time in this example was 300 minutes. Under these conditions, a thermal oxide film having a thickness of about 500 angstroms can be obtained. At the same time, the time required for gettering can be earned. Note that when the heat treatment is performed at 950 ° C. in an atmosphere of 100% oxygen, a thermal oxide film having a thickness of 500 Å or more can be obtained in about 30 minutes.

In this case, since nickel gettering cannot be performed sufficiently, nickel element remains in the crystalline silicon film 7 at a relatively high concentration. Therefore, as shown in this embodiment, it is preferable to form the thermal oxide film while adjusting the oxygen concentration and allowing time for obtaining a sufficient gettering effect. As in this method, when the thickness and the formation temperature of the thermal oxide film are changed, the time required for gettering the metal element can be set by adjusting the oxygen concentration in the atmosphere.

<< Example 9 >>
The ninth embodiment is an example in which a different form of crystal growth from the fourth embodiment is performed. The present embodiment relates to a method of performing crystal growth in a direction parallel to a substrate called lateral growth using a metal element that promotes crystallization of silicon. FIG. 23 is a diagram showing a manufacturing process of the ninth embodiment. First, a silicon oxynitride film having a thickness of 3000 Å was formed as a base film 9 on a Corning 1737 glass substrate 8 by a low pressure thermal CVD method. Of course, a quartz substrate may be used instead of the glass substrate.

Next, an amorphous silicon film 10 serving as a starting film of the crystalline silicon film was formed to a thickness of 2000 angstroms by a low pressure thermal CVD method. It is preferable that the thickness of the amorphous silicon film be 2000 Å or less as described above. Note that a plasma CVD method or the like may be used instead of the reduced pressure thermal CVD method. Next, a silicon oxide film (not shown) was formed to a thickness of 1500 angstroms, and was patterned to form a mask denoted by reference numeral 11. This mask has an opening formed in a region indicated by reference numeral 12. In the region where the opening 12 is formed, the amorphous silicon film 10 is exposed.

The opening 12 has a rectangular shape elongated in the longitudinal direction from the depth of the drawing to the front. The width of the opening 12 is suitably 20 μm or more, and the length in the longitudinal direction may be arbitrarily determined. Here, the width is 30 μm and the length is 5 cm. Then, as shown in Example 4, after applying an aqueous solution of nickel acetate containing 10 ppm by weight of nickel element, spin-drying was performed using a spinner (not shown) to remove excess solution. Thus, a state was realized in which the nickel element was held as a solution in contact with the exposed surface of the amorphous silicon film 10 as shown by the dotted line 13 in FIG.

Next, a heat treatment was performed at 640 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen and containing as little oxygen as possible. Then, crystal growth proceeded in a direction parallel to the substrate as indicated by 14 in FIG. This crystal growth proceeds from the region of the opening 12 into which the nickel element has been introduced toward the periphery. The crystal growth in the direction parallel to the substrate is referred to as lateral growth or lateral growth in this specification.

横 Under the conditions as in the ninth embodiment, the lateral growth can be performed over 100 μm or more. Thus, a crystalline silicon film 15 having a region grown laterally was obtained. In the region where the opening 12 is formed, crystal growth in a vertical direction called vertical growth proceeds from the surface of the silicon film to the interface of the base. Next, the mask 11, which was a silicon oxide film for selectively introducing a nickel element, was removed. Thus, the state shown in FIG. In this state, the silicon film 15 includes a vertical growth region, a horizontal growth region, and a region that has not been subjected to crystal growth (a region in an amorphous state).

で In this state, a heat treatment at a temperature of 640 ° C. was performed for 12 hours in an oxygen atmosphere. In this step, the oxide film 16 containing the nickel element in the film at a high concentration is formed, and at the same time, the nickel element concentration in the silicon film 15 can be relatively reduced. Here, the thermal oxide film 16 was formed to a thickness of 200 angstroms. This thermal oxide film contains the gettered nickel element at a high concentration. Further, by forming the thermal oxide film 16, the crystalline silicon film 15 has a thickness of about 2000 to 1900 angstroms.

Next, the thermal oxide film 16 containing the nickel element at a high concentration was removed in the same manner as in Example 4. The crystalline silicon film in this state has a concentration distribution such that the nickel element exists at a high concentration toward the surface of the crystalline silicon film. Therefore, it is useful to remove the region where the nickel element exists at a high concentration by further etching the surface of the crystalline silicon film after removing the thermal oxide film 16. That is, by etching the surface of the crystalline silicon film in which the nickel element exists at a high concentration, a crystalline silicon film in which the nickel element concentration is further reduced can be obtained.

Next, patterning was performed to form a pattern 17 composed of a laterally grown region as shown in FIG. Here, it is important that the pattern 17 does not include a vertically grown region, an amorphous region, and a tip region for lateral growth. This is because the concentration of the nickel element is relatively high in the leading end regions of the vertical growth and the lateral growth, and the electrical characteristics of the amorphous region which has not reached the crystal growth are inferior. Thus, the concentration of the nickel element remaining in the pattern 17 can be further reduced as compared with the case shown in the fourth embodiment.

This is also due to the fact that the concentration of the metal element contained in the lateral growth region is originally low. Specifically, the concentration of the nickel element in the pattern 17 composed of the lateral growth region can be easily set to the order of 10 ¹⁷ cm ⁻³ or less. Further, when the thin film transistor is formed using the lateral growth region, the height is higher than when the thin film transistor is formed using the vertical growth region as shown in the fourth embodiment (the entire surface is vertically grown in the fourth embodiment). A semiconductor device having mobility can be obtained.

It is useful to further perform an etching process after forming the pattern shown in FIG. 23E to remove the nickel element present on the pattern surface. It is not effective to form a thermal oxide film for gettering after forming the pattern 17. In this case, the gettering effect by the thermal oxide film is certainly obtained, but since the etching of the base film progresses when the thermal oxide film is removed, the underside of the crystalline silicon film formed in an island shape is excavated. This is because the etching proceeds as follows.

状態 Such a condition will later cause disconnection of wiring and malfunction of elements. In this embodiment, after the pattern 17 is formed, the thermal oxide film 18 is formed. This thermal oxide film 18 is a portion that will later become a part of the gate insulating film in the case of forming a thin film transistor, and has the above-described gettering effect, but is not intended to remove it.

<< Example 10 >>
Example 10 Example 10 is an example in which a thin film transistor arranged in a pixel region of an active matrix type liquid crystal display device or an active matrix type EL display device is manufactured using the crystalline silicon film according to the present invention. FIG. 24 is a diagram showing a manufacturing process of the tenth embodiment.

{Circle over (1)} First, a crystalline silicon film is formed on a glass substrate by the steps described in the fourth or ninth embodiment. The state shown in FIG. 24A was obtained by patterning the obtained crystalline silicon film. In FIG. 24A, reference numeral 20 denotes a glass substrate, reference numeral 21 denotes a base film, and reference numeral 22 denotes an active layer formed of a crystalline silicon film. After the state shown in FIG. 24A was obtained, plasma treatment was performed in a reduced-pressure atmosphere in which oxygen and hydrogen were mixed. This plasma was formed by high frequency discharge.

有機 By the plasma treatment, organic substances existing on the exposed surface of the active layer 22 are removed. To be precise, the organic substances adsorbed on the surface of the active layer are oxidized by the oxygen plasma, and the oxidized organic substances are reduced and vaporized by the hydrogen plasma. Thus, the organic substances existing on the exposed surface of the active layer 22 are removed. This removal of organic substances is very effective in suppressing the presence of fixed charges on the surface of the active layer 22. The fixed charge caused by the presence of the organic substance hinders the operation of the device and causes instability of the characteristics, and it is very useful to reduce the presence thereof.

After the removal of the organic matter, thermal oxidation was performed in an oxygen atmosphere at a temperature of 640 ° C. to form a thermal oxide film 19 of 100 Å. This thermal oxide film has a high interface characteristic with the semiconductor layer, and will form a part of the gate insulating film later. Thus, the state shown in FIG. Thereafter, a silicon oxynitride film 23 constituting a gate insulating film was formed to a thickness of 1000 Å. As a film forming method, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O, a plasma CVD method using a mixed gas of TEOS and N ₂ O, and the like can be used. Was used. This silicon oxynitride film 23 functions as a gate insulating film together with the thermal oxide film 19.

(4) It is effective that the silicon oxynitride film 23 contains a halogen element. That is, by fixing the nickel element by the action of the halogen element, the insulation of the gate insulating film is affected by the nickel element present in the active layer 22 (the same applies to other metal elements that promote crystallization of silicon). It is possible to prevent the function as a film from being reduced. The use of a silicon oxynitride film has a significance that a metal element is less likely to enter the gate insulating film due to its dense film quality. When a metal element enters the gate insulating film, the function as the insulating film is reduced, which causes instability and variation in characteristics of the thin film transistor. Note that a commonly used silicon oxide film can be used as the gate insulating film.

After the silicon oxynitride film 23 functioning as a gate insulating film was formed, an aluminum film (not shown) functioning as a gate electrode was formed later by a sputtering method. This aluminum film contained 0.2% by weight of scandium. The reason why scandium is contained in the aluminum film is to suppress generation of hillocks and whiskers in a later step. Here, hillocks and whiskers mean that heating causes abnormal growth of aluminum, thereby forming needle-like or barbed projections.

After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodized film was formed by using an ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. By performing anodic oxidation using the aluminum film as an anode and platinum as a cathode in this electrolytic solution, an anodic oxide film having dense film quality is formed on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) is about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation.

Next, a resist mask 25 was formed, and the aluminum film was patterned into a pattern indicated by 24. Thus, the state shown in FIG. 24B is obtained. Here, anodic oxidation is performed again. Here, a 3% by weight aqueous solution of oxalic acid was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 26 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 27 is formed. In this step, the anodic oxide film 27 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 25 having high adhesion on the upper portion.

This anodic oxide film can be grown to a thickness of several μm. Here, the film thickness was 6000 Å. The growth distance can be controlled by the anodic oxidation time. Next, the resist mask 25 was removed, and a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. As a result, an anodic oxide film having a dense film quality was formed as indicated by reference numeral 28 because the electrolytic solution entered the porous anodic oxide film 27.

膜厚 The thickness of the dense anodic oxide film 28 was 1000 Å. This film thickness was controlled by adjusting the applied voltage. Here, the exposed silicon oxynitride film 23 and thermal oxide film 19 were etched. For this etching, dry etching was used. Then, the porous anodic oxide film 27 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG.

(4) After obtaining the state shown in FIG. 24D, impurity ions were implanted. Here, P (phosphorus) ions were implanted by a plasma doping method in order to manufacture an N-channel thin film transistor. In this step, regions to be heavily doped (30 and 34) and regions to be lightly doped (31 and 33) are formed. This is because a part of the remaining silicon oxide film 29 functions as a semi-transparent mask, and a part of the implanted ions is shielded there.

Next, the region into which the impurity ions were implanted was activated by irradiating a laser beam. In addition, it can also be performed by irradiation of strong light instead of laser light. Thus, the source region 30, the channel forming region 32, the drain region 34, and the low-concentration impurity regions 31 and 33 were formed in a self-aligned manner. Here, what is indicated by reference numeral 33 in FIG. 24D is a region called an LDD (lightly doped drain) region. When the thickness of the dense anodic oxide film 28 is set to be as large as 2000 Å or more, an offset gate region can be formed outside the channel formation region 32 by the thickness.

Also in this embodiment, although the offset gate region is formed, since its size is small, its contribution due to its existence is small and the drawing becomes complicated, so that it is not shown in FIG. . Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 35. Here, a silicon oxide film was used. Note that the interlayer insulating film may be formed by forming a layer made of a resin material on a silicon oxide film or a silicon nitride film. Next, a contact hole was formed, and a source electrode 36 and a drain electrode 37 were formed. Thus, the thin film transistor shown in FIG. 24E was completed.

<< Example 11 >>
The eleventh embodiment is an embodiment relating to a method for forming the gate insulating film 23 in the configuration shown in the tenth embodiment. In the case where a quartz substrate, a glass substrate having high heat resistance, or the like is used as the substrate, a thermal oxidation method can be used as a method for forming the gate insulating film. The thermal oxidation method can make the film quality dense and is useful for obtaining a thin film transistor having stable characteristics. That is, an oxide film formed by a thermal oxidation method is one of the most suitable as a gate insulating film because it is dense as an insulating film and can reduce mobile charges existing therein.

In this embodiment, as a method for forming a thermal oxide film, heat treatment was performed in an oxidizing atmosphere at a temperature of 950 ° C. At this time, it is effective to mix HCl or the like in an oxidizing atmosphere. By doing so, the metal element existing in the active layer can be fixed simultaneously with the formation of the thermal oxide film. It is also effective to mix N ₂ O gas in an oxidizing atmosphere to form a thermal oxide film containing a nitrogen component. Here, by optimizing the mixing ratio of the N ₂ O gas, it is possible to obtain a silicon oxynitride film by a thermal oxidation method. In the case of the present embodiment, there is no need to particularly form the thermal oxide film 19, and the thermal oxide film 19 was not formed in the present embodiment.

<< Example 12 >>
The twelfth embodiment is an example in which a thin film transistor is manufactured by a process different from the processes described in the tenth to eleventh embodiments. FIG. 25 is a diagram showing the manufacturing process of this example. First, a crystalline silicon film is formed on a glass substrate by the steps shown in Example 4 or Example 5. Here, the crystalline silicon film is formed in accordance with the steps of Example 4. Next, by patterning it, the state shown in FIG. 25A was obtained.

(4) Thereafter, plasma treatment was performed in a mixed reduced pressure atmosphere of oxygen and hydrogen. In the state shown in FIG. 25A, 39 is a glass substrate, 40 is a base film, and 41 is an active layer formed of a crystalline silicon film. Reference numeral 38 denotes a thermal oxide film formed again after removing the thermal oxide film for gettering. After the state shown in FIG. 25A was obtained, a silicon oxynitride film 42 constituting a gate insulating film was formed to a thickness of 1000 angstroms.

As a film formation method, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O, a plasma CVD method using a mixed gas of TEOS and N ₂ O, or the like can be used. A mixed gas with N ₂ O was used. The silicon oxynitride film 42 forms a gate insulating film together with the thermal oxide film 38. Note that a silicon oxide film can be used instead of the silicon oxynitride film. After the silicon oxynitride film 42 functioning as a gate insulating film was formed, an aluminum film (not shown) functioning as a gate electrode was formed later by a sputtering method. This aluminum film contained 0.2% by weight of scandium.

After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodized film was formed using an ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having this dense film quality is about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by adjusting the voltage applied during anodic oxidation.

Next, a resist mask 43 was formed, and the aluminum film was patterned into a pattern indicated by 44. Next, anodic oxidation was performed again here. For this anodic oxidation, a 3% by weight aqueous solution of oxalic acid was used as an electrolytic solution. By performing anodic oxidation using the aluminum pattern 44 as an anode in this electrolytic solution, a porous anodic oxide film 45 is formed.

(4) In this step, the anodic oxide film 45 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 43 having high adhesion on the upper portion. This anodic oxide film can be grown to a thickness of several μm. Here, the thickness was set to 6000 Å. The growth distance can be controlled by adjusting the anodic oxidation time.

Next, after removing the resist mask 43, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, since the electrolytic solution enters (enters) the porous anodic oxide film 45, an anodic oxide film having a dense film quality is formed as shown by reference numeral 46 in FIG. 25C.

Here, the first impurity ion implantation was performed. Note that this step may be performed at that time after the resist mask 43 is removed. By the implantation of the impurity ions, a source region 47 and a drain region 49 are formed. No impurity ions are implanted into the region 48. Next, the porous anodic oxide film 45 was removed using a mixed acid obtained by mixing acetic acid, nitric acid and phosphoric acid. Thus, the state shown in FIG.

(4) After obtaining the state shown in FIG. 25D, impurity ions were implanted again. The impurity ions are implanted under light doping conditions rather than the first impurity ion implantation conditions. In this step, lightly doped regions (50 and 51) are formed, and a region indicated by reference numeral 52 in FIG. 25D becomes a channel formation region. Next, irradiation of intense light with an ultraviolet lamp was performed to activate the region into which the impurity ions had been implanted. Note that laser light can be used instead of strong light. Thus, the source region 47, the channel formation region 52, the drain region 49, and the low-concentration impurity regions 50 and 51 are formed in a self-aligned manner.

Here, what is indicated by reference numeral 51 in FIG. 25D is a region called an LDD (lightly doped drain) region. Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 53. Here, a silicon nitride film was used. Note that the interlayer insulating film may be formed by forming a layer made of a resin material on a silicon oxide film or a silicon nitride film. Thereafter, a contact hole was formed, and a source electrode 54 and a drain electrode 55 were formed. Thus, the thin film transistor shown in FIG. 25E was completed.

<< Example 13 >>
The thirteenth embodiment is an example in which an N-channel thin film transistor and a P-channel thin film transistor are configured to be complementary. The structure shown in this embodiment can be used, for example, for various thin film integrated circuits integrated on an insulating surface, and can be used for, for example, a peripheral drive circuit of an active matrix type liquid crystal display device.

FIG. 26 is a diagram showing the manufacturing process of the thirteenth embodiment. First, as shown in FIG. 26A, a silicon oxide film or a silicon oxynitride film is formed as a base film 58 over a glass substrate 57. Of these, a silicon oxynitride film is preferably used. Here, a silicon oxynitride film was used. Next, an amorphous silicon film (not shown) is formed by a plasma CVD method, a low pressure thermal CVD method or the like. Here, the amorphous silicon film is formed by a low pressure thermal CVD method.

{Circle around (2)} This amorphous silicon film was transformed into a crystalline silicon film by the same method as that described in Example 4, and then nickel element gettering was performed by forming a thermal oxide film. Next, after performing a plasma treatment in a mixed atmosphere of oxygen and hydrogen, the obtained crystalline silicon film was patterned to obtain active layers (59 and 60). Further, a thermal oxide film 56 constituting a gate insulating film was formed.

後 After the state shown in FIG. 26A was obtained, a silicon oxynitride film 61 was formed. In the case where quartz is used as the substrate, it is desirable to form the gate insulating film using only the thermal oxide film by using the above-described thermal oxidation method. Next, an aluminum film (not shown) for forming a gate electrode was formed to a thickness of 4000 angstroms. As a film other than the aluminum film, an anodizable metal such as tantalum can be used. After forming the aluminum film, an extremely thin and dense anodic oxide film was formed on the surface by the above-described method.

Next, after a resist mask (not shown) is arranged on the aluminum film and the aluminum film is patterned, anodic oxidation is performed using the obtained aluminum pattern as an anode to form a porous anodic oxide film (64 and 65). Formed. The thickness of the porous anodic oxide film was 5000 Å. Further, anodic oxidation was performed again under the conditions for forming a dense anodic oxide film, thereby forming dense anodic oxide films (66 and 67). Here, the thickness of the dense anodic oxide films 66 and 67 was 800 Å. Thus, the state shown in FIG. 26B is obtained.

(6) Further, the exposed silicon oxide film 61 and thermal oxide film 56 were removed by dry etching to obtain a state shown in FIG. Thereafter, the porous anodic oxide films 64 and 65 were removed using a mixed acid obtained by mixing acetic acid, nitric acid and phosphoric acid. Thus, the state shown in FIG. 26D is obtained. Here, resist masks were alternately arranged, and P (phosphorus) ions were implanted into the left thin film transistor and B (boron) ions were implanted into the right thin film transistor.

(4) By implantation of these impurity ions, a source region 70 and a drain region 73 having a high concentration of N-type were formed in a self-aligned manner. In addition, a weak N-type region 71 doped with P ions at a low concentration was simultaneously formed, and a channel forming region 72 was simultaneously formed. The reason for forming the region having the weak N-type shown by reference numeral 71 is that the remaining gate insulating film 68 exists. That is, P ions transmitted through the gate insulating film 68 are partially shielded by the gate insulating film 68.

Further, by the same principle and method, a source region 77 and a drain region 74 having a strong P-type were formed in a self-aligned manner, a low-concentration impurity region 76 was formed at the same time, and a channel formation region 75 was formed at the same time. . When the dense anodic oxide films 66 and 67 have a large film thickness of, for example, 2000 Å, the offset gate region can be formed in contact with the channel forming region with the thickness.

In the case of this embodiment, since the dense anodic oxide films 66 and 67 have a thin film thickness of 1000 angstroms or less, their existence can be neglected. Then, irradiation with laser light or strong light is performed to anneal the region into which the impurity ions have been implanted. Here, irradiation is performed using an infrared lamp. Next, as shown in FIG. 26E, a silicon nitride film 78 and a silicon oxide film 79 were formed as interlayer insulating films, and the thickness of each was set to 1000 Å. In this case, the silicon oxide film 79 need not be formed.

Here, the thin film transistor is covered with the silicon nitride film. Since the silicon nitride film is dense and has good interface characteristics, with such a structure, the reliability of the thin film transistor can be increased. Further, the interlayer insulating film 80 made of a resin material was formed by a spin coating method. Here, the thickness of the interlayer insulating film 80 was 1 μm. Next, a contact hole was formed to form a source electrode 81 and a drain electrode 82 of the left N-channel thin film transistor. At the same time, a source electrode 83 and a drain electrode 82 of the right thin film transistor were formed. Here, the drain electrodes 82 are commonly arranged. Thus, the state shown in FIG.

As described above, a thin film transistor circuit having a complementary CMOS structure can be formed. In the configuration shown in this example, a configuration was obtained in which the thin film transistor was covered with a nitride film and further covered with a resin material. With this configuration, it is possible to provide a highly durable one in which mobile ions and moisture hardly enter. Further, in the case where a multilayer wiring is formed, it is possible to prevent a capacitance from being formed between the thin film transistor and the wiring.

<< Example 14 >>
The fourteenth embodiment relates to a configuration in which the crystalline silicon film obtained in the fourth or fifth embodiment is further irradiated with a laser beam to form a single crystal or a region substantially regarded as a single crystal. It is an example.

First, as shown in Example 4, a crystalline silicon film was obtained by using the action of the nickel element. Next, the film was irradiated with a KrF excimer laser to further promote its crystallinity. At this time, a region which can be regarded as a single crystal or a substantially single crystal was formed by using a heat treatment at a temperature of 450 ° C. or higher in combination and further optimizing the irradiation conditions of the laser light.

The film that has greatly promoted crystallization by such a method has an electron spin density measured by ESR of 3 × 10 ¹⁷ cm ⁻³ or less, and has a minimum nickel element concentration of 3 × 10 ¹⁷ measured by SIMS. It had a density of 10 ¹⁷ cm ⁻³ or less and further had a region that could be regarded as a single crystal. In addition, there is substantially no grain boundary in this region, and high electrical characteristics comparable to a single crystal silicon wafer can be obtained.

The region which can be regarded as a single crystal contains 5 atomic% or less of hydrogen to about 1 × 10 ¹⁵ cm ⁻³ . This value was made clear by measurement by SIMS (secondary ion analysis method). When a thin film transistor is manufactured using such a single crystal or a region which can be regarded as a single crystal, a semiconductor device comparable to a MOS transistor manufactured using a single crystal wafer can be obtained.

<< Example 15 >>
Example 15 shows an example in which the nickel element was directly introduced into the surface of the base film in the process shown in Example 4 above. In this case, the nickel element is held in contact with the lower surface of the amorphous silicon film. In this embodiment, the nickel element was introduced after the formation of the base film, and first, the nickel element (the metal element) was brought into contact with and held on the surface of the base film. As a method for introducing the nickel element, a sputtering method, a CVD method, or an adsorption method can be used in addition to a method using a solution.

<< Example 16 >>
Example 16 is an example in which a crystalline silicon film was obtained on a glass substrate by using a nickel element. In this embodiment, first, a crystalline silicon film having high crystallinity was formed by the action of the nickel element. Next, an oxide film containing a halogen element was formed on the crystalline silicon film by a thermal oxidation method. At this time, the nickel element remaining in the obtained crystalline silicon film is gettered in the thermal oxide film by the action of oxygen and a halogen element.

Next, as a result of the gettering, the thermal oxide film containing a high concentration of nickel element was removed. This makes it possible to obtain a crystalline silicon film having high crystallinity and a low nickel element concentration on a glass substrate. FIG. 27 is a diagram showing a manufacturing process in this example.

First, a silicon oxynitride film 85 having a thickness of 3000 Å was formed as a base film on a Corning 1737 glass substrate (strain point: 667 ° C.). The silicon oxynitride film was formed by a plasma CVD method using silane, N ₂ O gas, and oxygen as source gases. This film formation may be performed by a plasma CVD method using a TEOS gas and a N ₂ O gas, for example.

(4) The silicon oxynitride film has a function of suppressing the diffusion of impurities from a glass substrate (a glass substrate contains a large amount of impurities at a semiconductor manufacturing level) in a later step. In order to maximize the function of suppressing the diffusion of impurities, a silicon nitride film is optimal. However, since the silicon nitride film comes off from the glass substrate due to stress, it is difficult to obtain the function as in this embodiment. If not practical. Alternatively, a silicon oxide film can be used as the base film.

Here, it is important that the underlayer 85 be as hard as possible. This is concluded from the fact that in a durability test of the finally obtained thin film transistor, the higher the hardness of the base film (that is, the lower the etching rate), the higher the reliability. The reason is considered to be due to the effect of shielding impurities from the glass substrate during the manufacturing process of the thin film transistor.

(4) It is effective that the base film 85 contains a trace amount of a halogen element typified by chlorine. By doing so, in a later step, a metal element that promotes crystallization of silicon present in the semiconductor layer can be gettered by the halogen element. It is effective to add a hydrogen plasma treatment after the formation of the base film. It is effective to perform plasma treatment in an atmosphere in which oxygen and hydrogen are mixed. This is effective in removing carbon components adsorbed on the surface of the base film and improving interface characteristics with a semiconductor film to be formed later.

Next, an amorphous silicon film 86 to be a crystalline silicon film later was formed to a thickness of 500 angstroms by a low pressure thermal CVD method. The reason why the low pressure thermal CVD method is used is that the film quality of the crystalline silicon film obtained later is superior, and specifically, the film quality is dense. As a method other than the reduced pressure thermal CVD method, a plasma CVD method or the like can be used.

The amorphous silicon film manufactured here preferably has an oxygen concentration in the film of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ . This is because oxygen plays an important role in the later step of gettering a metal element that promotes crystallization of silicon. However, care must be taken when the oxygen concentration is higher than the above concentration range, because crystallization of the amorphous silicon film is hindered. The other impurity concentration, for example, the impurity concentration of nitrogen or carbon is preferably as low as possible. Specifically, the concentration needs to be 2 × 10 ¹⁹ cm ⁻³ or less.

  In this embodiment, the thickness of the amorphous silicon film 86 is set to 1600 Å. This film thickness needs to be larger than the finally required film thickness as described later. When the amorphous silicon film 86 is crystallized only by heating, the thickness of the starting film (amorphous silicon film) 86 is set to 800 Å to 5000 μm, preferably 1500 to 3000 Å. If the thickness is larger than this range, the film formation time becomes longer, which is uneconomical in terms of production cost. If the thickness is smaller than this range, the crystallization becomes uneven or the reproducibility of the process becomes poor. Thus, the state shown in FIG.

Next, a nickel element was introduced to crystallize the amorphous silicon film 86. Here, the nickel element was introduced by applying a nickel acetate aqueous solution containing 10 ppm (by weight) of nickel to the surface of the amorphous silicon film 86. As a method for introducing the nickel element, in addition to the method using the above solution, a sputtering method, a CVD method, a plasma treatment, or an adsorption method can be used. Among them, the method using the above solution is simple and useful in that the concentration of the metal element can be easily adjusted.

By applying the nickel acetate aqueous solution, a water film (liquid film) 87 is formed as shown in FIG. In this state, an excess solution was blown off using a spin coater (not shown). Thus, the nickel element was held in contact with the surface of the amorphous silicon film 86. In consideration of the residual impurities in the subsequent heating step, it is preferable to use, for example, nickel sulfate instead of using nickel acetate. This is because the nickel acetate salt contains carbon, which may be carbonized in the subsequent heating step and remain in the film. The introduction amount of the nickel element can be adjusted by adjusting the concentration of the nickel salt in the solution.

Next, in the state shown in FIG. 27C, heat treatment is performed at a temperature of 450 ° C. to 650 ° C. to crystallize. This heat treatment is performed in a reducing atmosphere. Here, the heat treatment is performed at 620 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen. Thus, the amorphous silicon film 86 was crystallized to obtain a crystalline silicon film 88.

The reason why the atmosphere is a reducing atmosphere in the crystallization step by the heat treatment is to prevent formation of an oxide during the heat treatment step. More specifically, the reaction with nickel and oxygen, because the NiO _X is prevented from undesirably formed on the surface of the film or within the film.

Oxygen combines with nickel in a later gettering step and makes a great contribution to gettering of nickel. However, it has been found that the combination of oxygen and nickel in the crystallization step inhibits crystallization. Therefore, in the crystallization step by heating, it is important to suppress the formation of oxides as much as possible.

Here, the oxygen concentration in the atmosphere in which the heat treatment for crystallization is performed needs to be on the order of ppm, preferably 1 ppm or less. The gas that occupies most of the atmosphere in which the heat treatment for crystallization is performed is not limited to nitrogen, and may be an inert gas such as argon or a mixed gas thereof. The lower limit of the heat treatment temperature for the crystallization is preferably 450 ° C. or higher in view of its effect and reproducibility. The upper limit is preferably equal to or lower than the strain point of the glass substrate to be used. When a Corning 1737 glass substrate having a strain point of 667 ° C. is used as in this embodiment, the upper limit is set to about some margin. 650 ° C.

(4) In this regard, when a material having higher heat resistance, such as a quartz substrate, is used as the substrate, it can be performed at a temperature of up to about 1100 ° C. (preferably up to about 1050 ° C.). In this case, a crystalline silicon film having higher crystallinity can be obtained, and a crystalline silicon film can be obtained in a shorter time. Thus, a crystalline silicon film 88 was formed as shown in FIG.

(4) After the crystalline silicon film 88 was obtained, another heat treatment was performed. This heat treatment is performed to form a thermal oxide film containing a halogen element. Here, this heat treatment was performed in an atmosphere containing a halogen element. This step is for removing the nickel element intentionally mixed in the initial stage for crystallization from the crystalline silicon film 88.

This heat treatment is preferably performed at a higher temperature than the heat treatment performed for crystallization. This is an important condition for effectively performing nickel element gettering. Note that this heat treatment may be performed at a temperature similar to that of the heat treatment performed for crystallization, but a higher temperature is more effective, and higher quality crystals can be obtained.

This heat treatment is performed at a temperature of 550 ° C. to 1100 ° C., preferably about 700 ° C. to 1050 ° C., and more preferably 800 ° C. to 980 ° C., after satisfying the above conditions. This is because when the temperature is lower than 600 ° C., the effect is small, and when the temperature is higher than 1050 ° C., the jig made of quartz is distorted or a load is imposed on the apparatus. However, when a more heat-resistant jig is used, it can be carried out even at about 1100 ° C.). The upper limit of the heat treatment temperature is also limited by the strain point of the substrate used. It is necessary to pay attention to heat treatment at a temperature higher than the strain point of the substrate to be used, since the substrate is deformed.

Here, the heating temperature was set to 650 ° C. because a Corning 1737 glass substrate having a strain point of 667 ° C. was used. The atmosphere of the second heat treatment was performed in an atmosphere containing 5% by volume of HCl in oxygen. HCl is preferably mixed with oxygen at a rate of 0.5 to 10% (vol%). It should be noted that if the concentration is higher than this concentration, the surface of the film is roughened to the same level as the film thickness or more.

加熱 By performing the heat treatment under such conditions, a thermal oxide film 89 containing chlorine is formed as shown in FIG. In this embodiment, a heat treatment is performed for 12 hours to form a thermal oxide film 89 having a thickness of 200 Å. With the formation of the thermal oxide film 89, the thickness of the crystalline silicon film 86 becomes about 1500 angstroms.

In this heat treatment, when the heating temperature is 600 ° C. to 750 ° C., the treatment time (heating time) is 10 hours to 48 hours, typically 24 hours. When the heating temperature is 750 ° C. to 900 ° C., the treatment time is 5 hours to 24 hours, typically 12 hours. When the heating temperature is 900 ° C. to 1050 ° C., the processing time is 1 hour to 12 hours, typically 6 hours. Needless to say, these processing times are appropriately set depending on the thickness of the oxide film to be obtained.

In this step, the nickel element is gettered out of the crystalline silicon film by the action of oxygen and the action of the halogen element, particularly the action of the halogen element. Here, the nickel element is gettered in the natural oxide film 89 formed particularly by the action of chlorine. In this gettering, oxygen existing in the crystalline silicon film plays an important role. That is, the gettering effect by chlorine acts on the nickel oxide formed by the combination of oxygen and nickel, and the gettering of the nickel element proceeds effectively.

As described above, if the concentration of oxygen is too high, in the crystallization step shown in FIG. 27C, it becomes an element that hinders the crystallization of the amorphous silicon film 86. However, as mentioned above, its presence plays an important role in the nickel gettering process. Therefore, it is important to control the concentration of oxygen existing in the amorphous silicon film serving as the starting film. In this embodiment, an example has been described in which Cl is selected as a halogen element and HCl is used as a method for introducing Cl. As the gas other than HCl, one or a plurality of mixed gases selected from HF, HBr, Cl ₂ , F ₂ , and Br ₂ can be used. In addition to these, generally, hydrides of halogen can be used.

These gases content in atmosphere (volume), if HF 0.25 to 5%, if HBr 1 to 15%, 0.25 to 5% if Cl _2, F ₂ 0.125 to 2.5% if it is preferable that 0.5 to 10% for Br _2. If the concentration is lower than the above range, a significant effect cannot be obtained. If the concentration exceeds the upper limit of the above range, the surface of the crystalline silicon film becomes rough.

を Through this step, the concentration of the nickel element can be reduced to 1/10 or less of the initial concentration. This means that the nickel element can be reduced to 1/10 or less by the halogen element as compared with the case where no gettering by the halogen element is performed. This effect can be similarly obtained even when a metal element other than nickel, which promotes crystallization of silicon, is used. In addition, in the above-described step, since the nickel element is gettered in the oxide film to be formed, the nickel concentration in the oxide film naturally becomes higher than in other regions.

{Circle around (4)} The tendency of the nickel element to increase near the interface between the crystalline silicon film 88 and the oxide film 89 is observed. This is probably because the region where gettering is mainly performed is on the oxide film side near the interface between the crystalline silicon film and the oxide film. Further, it is considered that the reason why the gettering proceeds in the vicinity of the interface between the two films is due to the presence of stress and defects near the interface.

Next, the oxide film 89 containing nickel at a high concentration was removed. The removal of the oxide film 89 can be performed by wet etching using buffered hydrofluoric acid or another hydrofluoric acid-based etchant or by dry etching. Here, the etching was performed using buffered hydrofluoric acid.

Thus, as shown in FIG. 27E, a crystalline silicon film 90 with a reduced nickel content was obtained. In this case, since the nickel element is contained at a relatively high concentration in the vicinity of the surface of the obtained crystalline silicon film 90, the above etching is further advanced, and the surface of the crystalline silicon film 90 is slightly over-etched. That is valid.

<< Example 17 >>
In the seventeenth embodiment, in the configuration shown in the sixteenth embodiment, after a crystalline silicon film is obtained by the heat treatment step shown in FIG. 27C, laser light irradiation with a KrF excimer laser (wavelength: 248 nm) is performed. This is an example in which the crystallinity is promoted. In this embodiment, after the heat treatment step in FIG. 27C, annealing is performed by irradiating a laser beam, and the other steps are the same as those in Embodiment 16 as shown in FIG. A crystalline silicon film 90 having a reduced nickel content was obtained.

When the temperature of the heat treatment shown in FIG. 27C is low or the treatment time is short, that is, when the heating temperature is limited or the heating time is limited because of a manufacturing process, it is necessary. May not be obtained. In such a case, the required high crystallinity can be obtained by performing annealing by laser light irradiation. In this case, the laser beam irradiation allows a wider range of allowable laser irradiation conditions and higher reproducibility as compared with the case where the amorphous silicon film is directly crystallized thereby. .

照射 The above laser beam irradiation is performed after the step shown in FIG. It is important that the thickness of the amorphous silicon film 86 which is a starting film formed in FIG. 27A be 200 to 2000 Å. This is because the smaller the thickness of the amorphous silicon film, the higher the annealing effect by laser light irradiation. Although there is no particular limitation on the laser light used, it is preferable to use an excimer laser in the ultraviolet region. Specifically, for example, a KrF excimer laser (wavelength 248 nm) or a XeCl excimer laser (wavelength 308 nm) can be used. In addition, annealing may be performed by irradiating not only laser light but also strong light using, for example, an ultraviolet lamp.

<< Example 18 >>
The eighteenth embodiment is an example in which an infrared lamp is used instead of the laser beam in the seventeenth embodiment. In the present embodiment, after the heat treatment step of FIG. 27C, annealing is performed by irradiating an infrared lamp, and the other steps are the same as in Embodiment 16 as shown in FIG. A crystalline silicon film 90 having a reduced nickel content was obtained. When infrared rays are used, the silicon film can be selectively heated without heating the glass substrate much. Therefore, an effective heat treatment can be performed without causing thermal damage to the glass substrate.

<< Example 19 >>
Embodiment 19 Embodiment 19 is an example in which Cu is used as the metal element for promoting crystallization of silicon in the configuration shown in Embodiment 16. In this case, cupric acetate [Cu (CH ₃ COO) ₂ ], cupric chloride (CuCl ₂ 2H ₂ O) or the like may be used as a solution for introducing Cu. Copper [Cu (CH ₃ COO) ₂ ] was used. Other steps were performed in the same manner as in Example 16 to obtain a crystalline silicon film 90 having a reduced nickel concentration, as shown in FIG.

<< Example 20 >>
The twentieth embodiment is an example in which a quartz substrate is used as the substrate 84 in the configuration shown in the sixteenth embodiment. In this embodiment, the thickness of the amorphous silicon film 86 serving as a starting film is set to 2000 Å. The heating temperature at the time of forming the thermal oxide film by the heat treatment shown in FIG. In this case, since the oxide film is formed quickly and the effect of gettering cannot be sufficiently obtained, the oxygen concentration in the atmosphere is reduced. Specifically, heat oxidation was performed in an atmosphere in which the oxygen concentration in a nitrogen atmosphere was 10% by volume and the concentration of HCl with respect to oxygen was 3% by volume.

(4) The processing time was 300 minutes. Under these conditions, a thermal oxide film having a thickness of about 500 angstroms can be obtained. At the same time, the time required for gettering can be earned. When a heat treatment is performed at 950 ° C. in an atmosphere in which oxygen is 97% by volume and HCl is 3% by volume, a thermal oxide film having a thickness of 500 angstroms is obtained in about 30 minutes.

In the above case, since nickel gettering cannot be performed sufficiently, nickel element remains in the crystalline silicon film 90 at a relatively high concentration. Therefore, it is preferable to form the thermal oxide film while adjusting the oxygen concentration as in this embodiment and allowing time for obtaining a sufficient gettering effect. By using this method, the time required for gettering can be set by adjusting the oxygen concentration in the atmosphere when the thickness or the formation temperature of the thermal oxide film is changed.

<< Example 21 >>
Example 21 is an example in which crystal growth of a form different from that of Example 16 was performed. The present embodiment relates to a method of performing crystal growth in a direction parallel to a substrate, called lateral growth, using a metal element that promotes crystallization of silicon. FIG. 28 is a diagram showing a manufacturing process of the present Example 21.

First, a silicon oxynitride film was formed as a base film 92 on a Corning 1737 glass substrate 91 to a thickness of 3000 angstroms. The substrate may be a substrate such as a quartz substrate. Next, an amorphous silicon film 93 serving as a starting film of the crystalline silicon film was formed to a thickness of 2000 angstroms by a low pressure thermal CVD method. It is preferable that the thickness of the amorphous silicon film be 2000 Å or less as described above. Note that a plasma CVD method may be used instead of the reduced pressure thermal CVD method.

Next, a silicon oxide film (not shown) was formed to a thickness of 1500 angstroms, and was patterned to form a mask indicated by reference numeral 94. This mask has an opening formed in a region indicated by reference numeral 95. In the region where the opening 95 is formed, the amorphous silicon film 93 is exposed. The opening 95 has a rectangular shape elongated from the depth of the drawing to the front (longitudinal direction). The width of the opening 95 is suitably 20 μm or more, and the length in the longitudinal direction may be arbitrarily determined. In this embodiment, the width of the opening 95 is 30 μm and the length in the longitudinal direction is 200 μm. .

Next, a nickel acetate solution containing 10 ppm by weight of nickel element was applied in the same manner as in Example 16 described above. Further, spin drying was performed using a spinner (not shown) to remove excess solution. Thus, a state was realized in which the nickel acetate solution was held in contact with the exposed surface of the amorphous silicon film 93 as shown by the dotted line 96 in FIG.

Next, a heat treatment was performed at 640 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen and containing as little oxygen as possible. Then, crystal growth proceeded in a direction parallel to the substrate as indicated by 97 in FIG. 28B. This crystal growth proceeds from the region of the opening 95 into which the nickel element has been introduced toward the periphery. The crystal growth in the direction parallel to the substrate is referred to as lateral growth or lateral growth in this specification.

横 Under the conditions shown in this embodiment, the lateral growth can be performed over 100 μm. Thus, a silicon film 98 having a laterally grown region was obtained. In the region where the opening 95 is formed, crystal growth in the vertical direction called vertical growth progresses from the surface of the silicon film to the interface of the base. Next, the mask 94 made of a silicon oxide film for selectively introducing a nickel element was removed. Thus, the state shown in FIG. 28C is obtained. In this state, in the silicon film 98, there are a vertical growth region, a horizontal growth region, and a region that has not been subjected to crystal growth (amorphous state).

加熱 In the above state, a heat treatment at a temperature of 650 ° C. was performed for 12 hours in an oxygen atmosphere containing 3% by volume of HCl. In this step, an oxide film 99 containing a nickel element at a high concentration is formed. At the same time, the nickel element concentration in the silicon film 98 can be relatively reduced. Here, a thermal oxide film denoted by reference numeral 99 was formed to a thickness of 200 angstroms. This thermal oxide film contains a high concentration of nickel element gettered by the action of oxygen and the action of chlorine, especially the action of chlorine. Further, by forming the thermal oxide film 99, the crystalline silicon film 98 has a thickness of about 1900 angstroms.

(4) Next, the thermal oxide film 99 containing the nickel element at a high concentration was removed. The crystalline silicon film in this state has a concentration distribution such that the nickel element exists at a high concentration toward the surface of the crystalline silicon film. Therefore, it is useful to further etch the surface of the crystalline silicon film after removing the thermal oxide film 99 to remove the region where the nickel element exists at a high concentration. That is, by etching the surface of the crystalline silicon film in which the nickel element exists at a high concentration, a crystalline silicon film with a further reduced nickel element concentration can be obtained.

Next, patterning was performed to form a pattern 100 composed of a laterally grown region. Here, it is important that the pattern 100 does not include a vertically grown region, an amorphous region, and a tip region for lateral growth. This is because the concentration of the nickel element is relatively high in the tip regions of the vertical growth and the lateral growth, and the amorphous region has poor electrical characteristics.

The concentration of the nickel element remaining in the pattern 100 composed of the lateral growth regions obtained in this manner can be further reduced as compared with the case shown in the sixteenth embodiment. This is also due to the fact that the concentration of the metal element contained in the lateral growth region is originally low. Specifically, the concentration of the nickel element in the pattern 100 composed of the lateral growth region can be easily set to the order of 10 ¹⁷ cm ⁻³ or less.

Further, when the thin film transistor is formed using the lateral growth region, the height is higher than when the thin film transistor is formed using the vertical growth region as shown in Embodiment 16 (in the case of Embodiment 16, the entire surface is grown vertically). A semiconductor device having mobility can be obtained. After the pattern shown in FIG. 28E is formed, it is useful to further perform an etching process to remove the nickel element present on the pattern surface.

On the other hand, it is not useful to perform thermal oxidation in an oxidizing atmosphere containing a halogen element after patterning the crystalline silicon film into an island shape, and then remove the thermal oxide film. In this configuration, the gettering effect by the thermal oxide film is certainly obtained, but the etching of the underlying film proceeds when the thermal oxide film is removed, so that the etching is performed under the island-shaped crystalline silicon film. It is because it progresses so that it can be exterminated.

状態 Such a state later causes disconnection of wiring and malfunction of elements in the semiconductor device. Next, a thermal oxide film 101 was formed on the pattern 100 formed as described above. This thermal oxide film 101 will later become a part of the gate insulating film when forming a thin film transistor.

<< Example 22 >>
Example 22 is an example in which a thin film transistor arranged in a pixel region of an active matrix type liquid crystal display device or an active matrix type EL display device is manufactured using the crystalline silicon film according to the present invention. FIG. 29 is a diagram showing the manufacturing process of this example.

First, a crystalline silicon film was formed on a glass substrate by the steps shown in Example 16 and Example 21. Based on each of them, a thin film transistor was manufactured in the same manner. Hereinafter, the case where the crystalline silicon film having the configuration shown in Embodiment 16 is used will be described, but the same applies to the case where the crystalline silicon film having the configuration shown in Embodiment 21 is used. By patterning the crystalline silicon film, a state shown in FIG. 27A was obtained. In the state shown in FIG. 29A, 103 is a glass substrate, 104 is a base film, and 105 is an active layer formed of a crystalline silicon film.

Next, plasma treatment was performed in a reduced-pressure atmosphere in which oxygen and hydrogen were mixed. This plasma was generated by high frequency discharge. By this plasma treatment, organic substances existing on the exposed surface of the active layer 105 are removed. To be precise, the organic substances adsorbed on the surface of the active layer are oxidized by the oxygen plasma, and the oxidized organic substances are reduced and vaporized by the hydrogen plasma. Thus, the organic substances present on the exposed surface of the active layer 105 were removed. This removal of organic substances is very effective in suppressing the presence of fixed charges on the surface of the active layer 105.

固定 Since the fixed charge caused by the presence of the above-mentioned organic substance hinders the operation of the device or causes instability of characteristics, it is very useful to reduce the presence thereof. Next, after removing organic substances, thermal oxidation was performed in an oxygen atmosphere at a temperature of 640 ° C. to form a 100 Å thermal oxide film 102. This thermal oxide film has high interface characteristics with the semiconductor layer (active layer), and will later constitute a part of the gate insulating film. Thus, the state shown in FIG. 29A is obtained.

After that, a silicon oxynitride film 106 constituting a gate insulating film was formed to a thickness of 1000 Å. As a film forming method, for example, a plasma CVD method using a mixed gas of silane and N ₂ O, a plasma CVD method using a mixed gas of TEOS and N ₂ O, and the like are used. Here, silane and N ₂ O are used. The latter gas mixture was used. This silicon oxynitride film 106 functions as a gate insulating film together with the thermal oxide film 102.

(4) It is effective to include a halogen element in the silicon oxynitride film. That is, by fixing the nickel element by the action of the halogen element, the function of the gate insulating film as an insulating film due to the effect of the nickel element (other metal elements that promote crystallization of silicon) existing in the active layer. Can be prevented from decreasing.

こ と The use of such a silicon oxynitride film has a significance that the metal element is less likely to enter the gate insulating film due to its dense film quality. When a metal element enters the gate insulating film, its function as an insulating film is degraded, causing instability and variations in the characteristics of the thin film transistor. Note that, as the gate insulating film, a commonly used silicon oxide film can be used.

(4) After forming the silicon oxynitride film 106 functioning as a gate insulating film, an aluminum film (not shown, which becomes a pattern 107 after patterning described later) functioning as a gate electrode is formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium. Scandium is contained in the aluminum film in order to suppress generation of hillocks and whiskers in a later step. Here, the hillocks and whiskers mean that heating causes abnormal growth of aluminum, thereby forming needle-like or barbed protrusions.

After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodized film was formed by using an ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) was about 100 angstroms. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by adjusting the voltage applied during anodic oxidation.

Next, a resist mask 108 was formed, and the aluminum film was patterned into a pattern indicated by reference numeral 107. Thus, the state shown in FIG. 29B is obtained. Here, anodic oxidation was performed again. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 107 as an anode in this electrolytic solution, a porous anodic oxide film denoted by reference numeral 110 is formed.

In the above process, the anodic oxide film 110 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 108 having high adhesion on the upper portion. This anodic oxide film can be grown to a thickness of several μm. Here, the film thickness was 6000 Å. The growth distance can be controlled by the anodic oxidation time. Next, the resist mask 108 was removed.

Furthermore, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as indicated by reference numeral 111 because the electrolytic solution enters (enters) the porous anodic oxide film 110. The thickness of the dense anodic oxide film 111 was 1000 Å. This film thickness was controlled by adjusting the applied voltage.

(4) Here, the exposed silicon oxynitride film 106 and thermal oxide film 102 were etched. For this etching, dry etching was used. Next, the porous anodic oxide film 110 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 29D is obtained. After that, impurity ions were implanted. Here, P (phosphorus) ions were implanted by a plasma doping method in order to manufacture an N-channel thin film transistor.

In this step, regions 113 and 117 to be heavily doped and regions 114 and 116 to be lightly doped are formed. This is because a part of the remaining silicon oxide film 112 functions as a semi-transmissive mask, and a part of the implanted ions is shielded there. Next, irradiation with laser light or strong light is performed to activate the region into which the impurity ions have been implanted. Here, laser light is used. Thus, the source region 113, the channel formation region 115, the drain region 117, and the low-concentration impurity regions 114 and 116 were formed in a self-aligned manner.

Here, what is indicated by reference numeral 116 is a region called an LDD (lightly doped drain) region. Note that when the thickness of the dense anodic oxide film 111 is set to be as large as 2000 Å or more, the offset gate region can be formed outside the channel formation region 115 with the thickness. Although the offset gate region is also formed in this embodiment, its size is small, so its contribution due to its existence is small, and the drawing is complicated, so that it is not shown in the drawing.

Next, a silicon oxide film, a silicon nitride film, or a laminated film thereof is formed as the interlayer insulating film 118. Here, a silicon nitride film is used. As the interlayer insulating film, a layer made of a resin material may be formed over a silicon oxide film or a silicon nitride film. Next, a contact hole was formed, and a source electrode 119 and a drain electrode 120 were formed. Thus, the thin film transistor shown in FIG. 29E was completed.

<< Example 23 >>
Example 23 Example 23 relates to a method for forming the gate insulating film 106 in the structure shown in Example 22. When a quartz substrate or a glass substrate having high heat resistance is used as a substrate, a thermal oxidation method can be used as a method for forming a gate insulating film. The thermal oxidation method can make the film quality dense, and is useful for obtaining a thin film transistor having stable characteristics. That is, an oxide film formed by a thermal oxidation method is one of the most suitable as a gate insulating film because it is dense as an insulating film and can reduce mobile charges existing therein.

In this embodiment, as a method for forming a thermal oxide film, heat treatment was performed in an oxidizing atmosphere at a temperature of 950 ° C. At this time, it is effective to mix HCl or the like in an oxidizing atmosphere. By doing so, the metal element existing in the active layer can be fixed simultaneously with the formation of the thermal oxide film. It is also effective to mix N ₂ O gas in an oxidizing atmosphere to form a thermal oxide film containing a nitrogen component. Here, by optimizing the mixing ratio of the N ₂ O gas, it is possible to obtain a silicon oxynitride film by a thermal oxidation method. In this embodiment, it is not necessary to particularly form the thermal oxide film 102.

<< Example 24 >>
Example 24 is an example in which a thin film transistor is manufactured by a process different from the processes described in Examples 22 to 23. FIG. 30 shows a manufacturing process of this embodiment. First, a crystalline silicon film was formed on a glass substrate by the steps described in Example 16 or Example 17. Then, by patterning it, the state shown in FIG. 30A was obtained.

(5) Next, plasma treatment was performed in a mixed reduced pressure atmosphere of oxygen and hydrogen. In the state shown in FIG. 30A, 122 is a glass substrate, 123 is a base film, and 124 is an active layer formed of a crystalline silicon film. A portion denoted by reference numeral 121 is a thermal oxide film formed again after removing the thermal oxide film for gettering.

Next, a silicon oxynitride film 125 forming a gate insulating film was formed to a thickness of 1000 Å. As a film formation method, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O or a mixed gas of TEOS and N ₂ O is used, but the former is used here. The silicon oxynitride film 125 forms a gate insulating film together with the thermal oxide film 121. Note that a silicon oxide film can be used instead of the silicon oxynitride film.

(4) After forming the silicon oxynitride film 125 functioning as a gate insulating film, an aluminum film (not shown) functioning as a gate electrode was formed later by a sputtering method. This aluminum film contained 0.2% by weight of scandium. After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodic oxide film was formed using an ethylene glycol solution containing 3% by weight of tartaric acid as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed by using the aluminum film as an anode and platinum as a cathode to form an anodized film having a dense film quality on the surface of the aluminum film.

膜厚 The thickness of the anodic oxide film having a dense film quality (not shown) was about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation. Next, a resist mask 126 was formed, and the aluminum film was patterned into a pattern indicated by 127.

で Anodization was performed again here. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 127 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 128 is formed. In this step, an anodic oxide film 128 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 126 having high adhesion on the upper portion.

This anodic oxide film can be grown to a thickness of several μm. Here, the film thickness was 6000 Å. The growth distance can be controlled by adjusting the anodic oxidation time. Next, after removing the resist mask 126, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as shown by reference numeral 129 because the electrolytic solution enters (penetrates) into the porous anodic oxide film 128.

Next, the first impurity ion implantation was performed. This step may be performed after the resist mask 126 is removed. By the implantation of the impurity ions, a source region 130 and a drain region 132 are formed. Note that no impurity ions are implanted into the region indicated by reference numeral 131. Next, the porous anodic oxide film 128 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG.

Thereafter, impurity ions were implanted again. The impurity ions were formed under light doping conditions rather than the first impurity ion implantation conditions. In this step, lightly doped regions 133 and 134 are formed, and a region indicated by reference numeral 135 becomes a channel forming region. Next, irradiation with strong light using an infrared lamp was performed to activate the region into which the impurity ions had been implanted. Note that a laser beam can be used instead of the strong light. Thus, the source region 130, the channel formation region 135, the drain region 132, and the low-concentration impurity regions 133 and 134 were formed in a self-aligned manner.

Here, what is indicated by reference numeral 134 is a region called an LDD (lightly doped drain) region. Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 136. Here, a silicon nitride film is formed. As the interlayer insulating film, a layer made of a resin material may be formed over a silicon oxide film or a silicon nitride film. Next, a contact hole was formed, and a source electrode 137 and a drain electrode 138 were formed. Thus, the thin film transistor shown in FIG. 30E was completed.

<< Example 25 >>
The twenty-fifth embodiment is an example in which an N-channel thin film transistor and a P-channel thin film transistor are configured to be complementary. FIG. 31 shows a manufacturing process of Example 25. The configuration shown in this embodiment can be used, for example, for various thin film integrated circuits integrated on an insulating surface. Further, for example, it can be used for a peripheral drive circuit of an active matrix type liquid crystal display device.

First, as shown in FIG. 31A, a silicon oxide film or a silicon oxynitride film was formed as a base film 141 over a glass substrate 140. Preferably, a silicon oxynitride film is used, and this is used here. Further, an amorphous silicon film (not shown) is formed by a plasma CVD method or a low pressure thermal CVD method. Here, a low pressure thermal CVD method is used. Further, the amorphous silicon film was transformed into a crystalline silicon film by the method shown in Example 16.

Next, plasma treatment was performed in a mixed atmosphere of oxygen and hydrogen, and the obtained crystalline silicon film was patterned to obtain active layers 142 and 143. Thus, the state shown in FIG. Note that here, in order to suppress the influence of carriers moving on the side surface of the active layer, in the state shown in FIG. Heat treatment was performed.

When a trap level due to the presence of a metal element exists on the side surface of the active layer, the OFF current characteristic is deteriorated. Useful. Further, a thermal oxide film 139 constituting a gate insulating film and a silicon oxynitride film 144 were formed. Here, in the case where quartz is used as the substrate, it is desirable that the gate insulating film is constituted only by the thermal oxide film using the above-described thermal oxidation method.

Next, an aluminum film (not shown) for forming a gate electrode was formed to a thickness of 4000 angstroms later. Other than the aluminum film, an anodizable metal (for example, tantalum) can be used. After forming the aluminum film, an extremely thin and dense anodic oxide film was formed on the surface by the above-described method. Next, a resist mask (not shown) was arranged on the aluminum film, and the aluminum film was patterned. Then, anodic oxidation was performed using the obtained aluminum pattern as an anode to form porous anodic oxide films 147 and 148.

膜厚 The thickness of the porous anodic oxide film was 5000 Å. Further, anodic oxidation was performed again under the conditions for forming a dense anodic oxide film, and dense anodic oxide films 149 and 150 were formed. Here, the thickness of the dense anodic oxide films 149 and 150 is 800 Å. Thus, the state shown in FIG. Further, the exposed silicon oxide film 144 and thermal oxide film 139 were removed by dry etching to obtain a state shown in FIG.

を 得 After obtaining the state shown in FIG. 31C, the porous anodic oxide films 147 and 148 were removed using a mixed acid obtained by mixing acetic acid, nitric acid and phosphoric acid. Thus, the state shown in FIG. 31D is obtained. Here, resist masks were alternately arranged so that P (phosphorus) ions were implanted into the left thin film transistor and B (boron) ions were implanted into the right thin film transistor. By the implantation of the impurity ions, a source region 153 and a drain region 156 having a high concentration of N-type are formed in a self-aligned manner.

{Circle around (4)} A region 154 having a weak N-type doped with P ions at a low concentration is formed at the same time, and a channel forming region 155 is formed at the same time. The reason why the region having the weak N-type shown by reference numeral 154 is formed is that the remaining gate insulating film 151 exists. That is, P ions transmitted through the gate insulating film 151 are partially shielded by the gate insulating film 151.

{Circle around (4)} According to the same principle and method, the source region 160 and the drain region 157 having a strong P type are formed in a self-aligned manner. At the same time, a low concentration impurity region 159 is formed, and a channel formation region 158 is formed at the same time. When the dense anodic oxide films 149 and 150 have a large thickness of, for example, 2000 Å, the offset gate region can be formed in contact with the channel forming region with the thickness.

In the case of this embodiment, since the dense anodic oxide films 149 and 150 have a thin film thickness of 1000 angstroms or less, their existence can be neglected. Next, laser light irradiation was performed to anneal the region into which the impurity ions had been implanted. Note that strong light can be used instead of laser light. Subsequently, as shown in FIG. 31E, a silicon nitride film 161 and a silicon oxide film 162 were formed as interlayer insulating films. Each film thickness was 1000 Å. Note that the silicon oxide film 162 need not be formed.

Here, the thin film transistor is covered with the silicon nitride film. Since the silicon nitride film is dense and has good interface characteristics, such a structure can increase the reliability of the thin film transistor. Further, an interlayer insulating film 163 made of a resin material was formed by a spin coating method, and the thickness of the interlayer insulating film 163 was 1 μm.

Next, a contact hole is formed, and a source electrode 164 and a drain electrode 165 of the N-channel thin film transistor on the left side are formed, and a source electrode 166 and a drain electrode 165 of the thin film transistor on the right side are formed at the same time. The configuration shown was obtained. Here, the drain electrodes 165 are commonly arranged. In this manner, a thin film transistor circuit having a complementary CMOS structure can be formed.

In the configuration shown in this embodiment, a configuration in which the thin film transistor is covered with a nitride film and further covered with a resin material is obtained. With this configuration, it is possible to provide a highly durable one in which mobile ions and moisture hardly enter. In addition, when a multilayer wiring is formed, it is possible to prevent a capacitance from being formed between the thin film transistor and the wiring.

<< Example 26 >>
Example 26 is an example in which the crystalline silicon film obtained in Example 16 or Example 17 is further irradiated with laser light to form a region that can be regarded as a single crystal or a substantially single crystal. is there.

First, as shown in Example 16, a crystalline silicon film was obtained by utilizing the action of the nickel element. Then, the film was irradiated with laser light to further promote its crystallinity. Here, a KrF excimer laser was used as the laser light. At that time, a region which can be regarded as a single crystal or a substantially single crystal can be formed by using heat treatment at a temperature of 450 ° C. or higher in combination with optimizing the laser irradiation conditions.

The film that has greatly promoted crystallization by such a method has an electron spin density measured by ESR of 3 × 10 ¹⁷ cm ⁻³ or less, and has a minimum nickel element concentration of 3 × 10 ¹⁷ measured by SIMS. It has a density of 10 ¹⁷ cm ^-3 or less and further has a region that can be regarded as a single crystal. In this region, there is substantially no crystal grain boundary, and high electrical characteristics comparable to a single crystal silicon wafer can be obtained.

The region which can be regarded as a single crystal contains 5 atomic% or less of hydrogen to about 1 × 10 ¹⁵ cm ⁻³ . This value was made clear by measurement by SIMS (secondary ion analysis method). When a thin film transistor is manufactured using such a single crystal or a region which can be regarded as a single crystal, a semiconductor device comparable to a MOS transistor manufactured using a single crystal wafer can be obtained.

<< Example 27 >>
Example 27 is an example in which the nickel element was directly introduced into the surface of the underlayer in the process shown in Example 16. In this case, the nickel element is held in contact with the lower surface of the amorphous silicon film. In this embodiment, the nickel element is introduced by applying a nickel acetate aqueous solution after the formation of the base film, and first, the nickel element (the metal element) is brought into contact with and held on the surface of the base film. Other steps were the same as those in Example 16 to complete a thin film transistor similar to that shown in FIG. As a method for introducing the nickel element, a sputtering method, a CVD method, and an adsorption method can be used in addition to a method using a solution.

<< Example 28 >>
Example 28 is an example in which a crystalline silicon film is obtained on a glass substrate by using a nickel element. In this embodiment, first, a crystalline silicon film having high crystallinity is obtained by the action of the nickel element, and then irradiation with laser light is performed to increase the crystallinity of the film and to be locally concentrated. The nickel element was diffused into the film. That is, the mass of nickel was eliminated.

Next, an oxide film containing a halogen element was formed on the crystalline silicon film by a thermal oxidation method. At this time, the nickel element remaining in the crystalline silicon film is gettered in the thermal oxide film by the action of oxygen and a halogen element. At the same time, since the nickel element is dispersed and present by the irradiation of the laser beam, gettering proceeds effectively. Next, as a result of gettering, the thermal oxide film containing a high concentration of nickel element was removed. By doing so, a crystalline silicon film having high crystallinity and a low nickel element concentration on a glass substrate can be obtained.

FIG. 32 is a diagram showing the manufacturing process of this example. First, a silicon oxynitride film 168 as a base film was formed to a thickness of 3000 Å on a Corning 1737 glass substrate (strain point 667 ° C.) 167. The silicon oxynitride film was formed by a plasma CVD method using a mixed gas of silane, N ₂ O gas, and oxygen as a source gas. Note that a mixed gas of TEOS gas and N ₂ O gas may be used as the source gas.

The silicon oxynitride film has a function of suppressing diffusion of impurities from a glass substrate (a glass substrate contains a large amount of impurities at a semiconductor manufacturing level) in a later step. . In order to maximize the function of suppressing the diffusion of impurities, a silicon nitride film is optimal, but the silicon nitride film is not practical because it comes off the glass substrate due to stress. Note that a silicon oxide film can be used as the base film.

(4) It is important that the underlayer 168 be as hard as possible. This is concluded from the fact that in a durability test of the finally obtained thin film transistor, the higher the hardness of the base film (that is, the lower the etching rate), the higher the reliability. The reason is considered to be due to the effect of shielding impurities from the glass substrate during the manufacturing process of the thin film transistor.

(4) It is effective that the base film 168 contains a trace amount of a halogen element represented by chlorine. By doing so, in a later step, a metal element that promotes crystallization of silicon present in the semiconductor layer can be gettered by the halogen element. Further, it is effective to apply a hydrogen plasma treatment after forming the base film. It is effective to perform plasma treatment in an atmosphere in which oxygen and hydrogen are mixed. This is effective in removing carbon components adsorbed on the surface of the base film and improving interface characteristics with a semiconductor film to be formed later.

Next, an amorphous silicon film 169 to be a crystalline silicon film later was formed to a thickness of 500 angstroms by a low pressure thermal CVD method. The reason why the low pressure thermal CVD method is used is that the film quality of the crystalline silicon film obtained later is superior, and specifically, the film quality is dense. As a method other than the reduced pressure thermal CVD method, a plasma CVD method or the like can be used. The amorphous silicon film manufactured here preferably has an oxygen concentration in the film of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ . This is because oxygen plays an important role in a later metal element (metal element that promotes crystallization of silicon) gettering step. However, care must be taken when the oxygen concentration is higher than the above concentration range, because crystallization of the amorphous silicon film is hindered.

The other impurity concentration, for example, the impurity concentration of nitrogen or carbon is preferably as low as possible. Specifically, the concentration needs to be 2 × 10 ¹⁹ cm ⁻³ or less. The upper limit of the thickness of this amorphous silicon film is about 2000 Å. This is because it is disadvantageous that the film is too thick in order to obtain the effect of the subsequent laser light irradiation. The disadvantage of the thick film is that most of the laser light applied to the silicon film is absorbed on the surface of the film. Note that the lower limit of the film thickness of the amorphous silicon film 169 depends on the film forming method, but is practically about 200 Å.

(4) Next, a nickel element was introduced to crystallize the amorphous silicon film 169. Here, the nickel element was introduced by applying an aqueous solution of nickel acetate containing 10 ppm (by weight) of nickel to the surface of the amorphous silicon film 169. As a method for introducing the nickel element, in addition to the method using the above solution, a sputtering method, a CVD method, a plasma treatment, and an adsorption method can be used.

の う ち Among them, the method using the above solution is simple and useful in that the concentration of the metal element can be easily adjusted. By applying the nickel acetate aqueous solution, a water film of the nickel acetate solution is formed as indicated by reference numeral 170 in FIG. After obtaining this state, excess solution was blown off using a spinner (not shown). In this manner, the nickel element was held in contact with the surface of the amorphous silicon film 169.

Considering residual impurities in the subsequent heating step, it is preferable to use, for example, nickel sulfate instead of using the nickel acetate aqueous solution. This is because the nickel acetate aqueous solution contains carbon, which may be carbonized in a subsequent heating step and remain in the film. The introduction amount of the nickel element can be adjusted by adjusting the concentration of the nickel salt in the solution.

Next, in the state shown in FIG. 32B, heat treatment is performed at a temperature of 550 ° C. to 650 ° C. to crystallize the amorphous silicon film 169 to form a crystalline silicon film 171. The treatment is preferably performed at a temperature lower than the strain point of the glass substrate. Since the strain point of the Corning 1737 glass substrate used here is 667 ° C., the upper limit is preferably set to about 650 ° C. in consideration of a margin. This heat treatment is performed in a reducing atmosphere. In this embodiment, the atmosphere for this heat treatment was a nitrogen atmosphere containing 3% by volume of hydrogen, the heating temperature was 620 ° C., and the heating time was 4 hours.

The reason why the atmosphere is a reducing atmosphere in the crystallization step by the above heat treatment is to prevent oxides from being formed during the heat treatment step. Specifically, in order to prevent the nickel and oxygen NiO _X reacts from being formed on the surface of the film or within the film. Oxygen combines with nickel in a later gettering step and makes a great contribution to gettering of nickel.

However, it has been found that the binding of oxygen and nickel at this crystallization stage inhibits crystallization. Therefore, in the step of crystallization by heating, it is important to suppress the formation of oxides as much as possible. Therefore, the oxygen concentration in the atmosphere in which the heat treatment for crystallization is performed needs to be on the order of ppm, preferably 1 ppm or less.

In addition, as the gas occupying most of the atmosphere in which the heat treatment for the crystallization is performed, an inert gas such as argon or a mixed gas thereof can be used in addition to nitrogen. After the crystallization step by the heat treatment, the nickel element remains in a certain amount of lump. This was confirmed by observation with a TEM (transmission electron microscope). The cause for the fact that nickel is present in some mass is not clear, but is believed to be related to some crystallization mechanism.

Next, laser light irradiation is performed as shown in FIG. Here, a method was used in which a KrF excimer laser (wavelength: 248 nm) was used and a laser beam having a linear beam shape was irradiated while scanning. By irradiating this laser light, the nickel element that has been locally concentrated as a result of the crystallization by the above-described heat treatment is dispersed to some extent in the film 171. That is, the lump of the nickel element can be eliminated by laser light irradiation, and the nickel element can be dispersed.

Next, another heat treatment was performed in the step shown in FIG. This heat treatment is performed to form a thermal oxide film for gettering the nickel element. Here, the heat treatment was performed in an atmosphere containing a halogen element. Specifically, the heat treatment was performed in an oxygen atmosphere containing 5% by volume of HCl. This step is for removing from the crystalline silicon film 171 the nickel element intentionally mixed at the initial stage for crystallization (the same applies to other metal elements that promote crystallization of silicon). It is a process.

(4) The heat treatment is performed at a higher temperature than the heat treatment performed for performing the above-described crystallization. This is an important condition for effectively performing nickel element gettering. Note that the heat treatment can be performed at a temperature equal to or lower than the temperature of the heat treatment performed for crystallization, but the effect is small.

This heat treatment is performed at a temperature of 600 ° C. to 750 ° C. after satisfying the above conditions. The gettering effect of the nickel element in this step can be remarkably obtained when the temperature is higher than 600 ° C., but in this embodiment, the temperature was 650 ° C. In this step, the nickel element dispersed by the above-described laser light irradiation is effectively gettered in the oxide film. Further, the upper limit of the heat treatment temperature is limited by the strain point of the glass substrate used. Note that if heat treatment is performed at a temperature equal to or higher than the strain point of the glass substrate to be used, the substrate is deformed;

It is preferable that HCl is mixed with oxygen at a ratio of 0.5 to 10% by volume. It should be noted that if HCl is mixed at a concentration higher than this concentration, the surface of the film is roughened to the same level as the film thickness. When heat treatment is performed under such conditions, a thermal oxide film 172 containing chlorine is formed as illustrated in FIG. In this embodiment, the heat treatment time is 12 hours, and the thickness of the thermal oxide film 172 is 100 Å.

(4) By forming the thermal oxide film 172, the thickness of the crystalline silicon film 169 becomes about 450 angstroms. In this heat treatment, when the heating temperature is 600 ° C. to 750 ° C., the treatment time (heating time) is 10 hours to 48 hours, typically 24 hours. Of course, this processing time may be set as appropriate according to the thickness of the oxide film to be obtained. In this step, the nickel element is gettered outside the silicon film by the action of oxygen and the action of the halogen element. Here, the nickel element is gettered in the formed thermal oxide film 172 by the action of chlorine in particular.

酸 素 Oxygen is also involved in the gettering. In this gettering, oxygen existing in the crystalline silicon film plays an important role. That is, the gettering effect of chlorine acts on nickel oxide formed by the combination of oxygen and nickel, and gettering of the nickel element proceeds effectively. As described above, if the concentration of oxygen is too high, in the crystallization step shown in FIG. 32B, it becomes an element that hinders the crystallization of the amorphous silicon film 169. However, as described above, its presence plays an important role in the nickel gettering process. Therefore, it is important to control the concentration of oxygen existing in the amorphous silicon film serving as the starting film.

In this embodiment, an example has been described in which Cl is selected as a halogen element and HCl is used as a method for introducing Cl. As the gas other than HCl, one or a plurality of gases selected from HF, HBr, Cl ₂ , F ₂ , and Br ₂ can be used. In general, a hydride of a halogen can be used. These gases, the content in the atmosphere (volume) to as long as HF 0.25 to 5%, if HBr 1 to 15%, if the Cl ₂ 0.25 to 5%, by F ₂ 0.125 to 2.5% if it is preferable that 0.5 to 10% for Br _2.

濃度 If the concentration is lower than the above range, no significant effect can be obtained, and if the concentration is higher than the above range, the surface of the silicon film becomes rough. Through this step, the concentration of the nickel element can be reduced to 1/10 or less of the initial concentration. This means that the nickel element can be reduced to 1/10 or less as compared with the case where no gettering by the halogen element is performed. This effect can be obtained similarly when another metal element is used. In addition, in the above process, since the nickel element is gettered in the oxide film to be formed, the nickel concentration in the oxide film is naturally higher than in other regions.

{Circle around (4)} The tendency of the nickel element to increase near the interface between the crystalline silicon film 171 and the thermal oxide film 172 is observed. This is probably because the region where gettering is mainly performed is on the oxide film side near the interface between the crystalline silicon film and the oxide film. Further, it is considered that the gettering proceeds near the interface between the two due to the presence of stress and defects near the interface.

Next, the oxide film 172 containing nickel at a high concentration was removed. The removal of the oxide film 172 is performed by wet etching using buffer hydrofluoric acid (other hydrofluoric acid-based etchant) or dry etching. In this embodiment, wet etching using buffer hydrofluoric acid is performed.

Thus, as shown in FIG. 32E, a crystalline silicon film 173 having a reduced nickel concentration was obtained. In addition, since the nickel element is contained at a relatively high concentration in the vicinity of the surface of the obtained crystalline silicon film 173, the etching of the oxide film 172 is further advanced to slightly overetch the surface of the crystalline silicon film 173. It is effective to do.

(4) It is effective to irradiate laser light again after removing the thermal oxide film 172 to further promote the crystallinity of the obtained crystalline silicon film 173. That is, it is effective to perform laser light irradiation again after nickel element gettering is performed. In this embodiment, an example is shown in which a KrF excimer laser (wavelength: 248 nm) is used as the laser light. However, a XeCl excimer laser (wavelength 308 nm) and other types of lasers can also be used. Further, a configuration may be employed in which irradiation with, for example, ultraviolet light or infrared light is performed instead of laser light.

<< Example 29 >>
Embodiment 29 Embodiment 29 is an example in which Cu is used as a metal element for promoting crystallization of silicon in the configuration shown in Embodiment 28. In this case, cupric acetate [Cu (CH ₃ COO) ₂ ], cupric chloride (CuCl ₂ 2H ₂ O) or the like may be used as a solution for introducing Cu. Using copper (CuCl ₂ 2H ₂ O), the other steps were the same as in Example 28 to obtain the state shown in FIG.

<< Example 30 >>
The thirtieth embodiment is an example in which a different form of the crystal growth from the twenty-eighth embodiment is performed. The present embodiment relates to a method of performing crystal growth in a direction parallel to a substrate called lateral growth using a metal element that promotes crystallization of silicon. FIG. 33 is a diagram showing the manufacturing process of this example.

First, a silicon oxynitride film having a thickness of 3000 Å was formed as a base film 175 on a Corning 1737 glass substrate 174. Note that a quartz substrate may be used instead of the glass substrate. Next, an amorphous silicon film 176 serving as a starting film of the crystalline silicon film was formed to a thickness of 600 angstroms by a low pressure thermal CVD method. It is preferable that the thickness of the amorphous silicon film be 2000 Å or less as described above. Note that a plasma CVD method may be used instead of the low pressure thermal CVD method.

Next, a silicon oxide film (not shown) was formed to a thickness of 1500 angstroms and patterned to form a mask indicated by reference numeral 177. This mask has an opening formed in a region indicated by 178. In a region where the opening 178 is formed, the amorphous silicon film 176 is exposed. The opening 178 has an elongated rectangle extending from the depth of the drawing to the front (longitudinal direction). The width of the opening 178 is suitably 20 μm or more, and the length in the longitudinal direction may be a required length. In this embodiment, the width is 30 μm and the length is 4 cm.

Next, in the same manner as described in Example 28, a nickel acetate aqueous solution containing 10 ppm by weight of nickel element was applied, and spin-drying was performed using a spinner (not shown) to remove excess solution. Thus, a state was realized in which the nickel element was held in contact with the exposed surface of the amorphous silicon film 176 as shown by the dotted line 179 in FIG.

Next, a heat treatment was performed at 640 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen and containing as little oxygen as possible. Then, crystal growth proceeded in a direction parallel to the substrate 174 as indicated by 180 in FIG. This crystal growth proceeds from the region of the opening 178 into which the nickel element has been introduced toward the periphery. The crystal growth in the direction parallel to the substrate is referred to as lateral growth or lateral growth in this specification.

横 Under the conditions as shown in Example 30, the lateral growth can be performed over 100 μm or more. Thus, a crystalline silicon film 181 having a region grown laterally was obtained. In the region where the opening 178 is formed, crystal growth in the vertical direction called vertical growth proceeds from the surface of the silicon film toward the interface of the base.

Next, the mask 177 made of the silicon oxide film for selectively introducing the nickel element was removed to obtain a state shown in FIG. In this state, the silicon film 181 includes a vertical growth region, a horizontal growth region, and a region that has not been subjected to crystal growth (amorphous state). In this state, nickel element is contained in the film. It is unevenly distributed. In particular, the nickel element exists at a relatively high concentration in the region where the opening 178 is formed and in the tip portion in the crystal growth direction indicated by reference numeral 180.

Next, laser light irradiation is performed. Here, KrF excimer laser irradiation was performed in the same manner as in Example 28. The nickel element unevenly distributed in this step is diffused, and a state in which gettering is easily performed in a later gettering step is obtained. After the irradiation with the laser beam was completed, a heat treatment at 650 ° C. was performed for 12 hours in an oxygen atmosphere containing 3% by volume of HCl. In this step, an oxide film 182 containing a nickel element in the film at a high concentration is formed, and at the same time, the nickel element concentration in the silicon film 181 is relatively reduced.

Here, a thermal oxide film indicated by 182 was formed to a thickness of 100 angstroms. This thermal oxide film contains a high concentration of nickel element gettered by the action of oxygen and the action of chlorine, especially the action of chlorine. Further, by forming thermal oxide film 182, crystalline silicon film 181 has a thickness of about 500 angstroms. Next, the thermal oxide film 182 containing the nickel element at a high concentration was removed.

(4) The crystalline silicon film in this state has a concentration distribution such that the nickel element exists at a high concentration toward the surface of the crystalline silicon film. This state results from the nickel element being gettered in the thermal oxide film when the thermal oxide film 182 is formed. Therefore, it is useful to further etch the surface of the crystalline silicon film after removing the thermal oxide film 182 to remove the region where the nickel element exists at a high concentration. That is, by etching the surface of the crystalline silicon film in which the nickel element exists at a high concentration, a crystalline silicon film with a further reduced nickel element concentration can be obtained. However, in this case, it is necessary to consider the thickness of the silicon film finally obtained.

Next, a pattern 183 composed of a lateral growth region was formed by patterning. The concentration of the nickel element remaining in the pattern 183 formed of the lateral growth region obtained in this manner can be further reduced as compared with the case shown in Embodiment 28. This is also due to the fact that the concentration of the metal element contained in the lateral growth region is originally low. Specifically, the concentration of the nickel element in the pattern 183 composed of the lateral growth region can be easily set to the order of 10 ¹⁷ cm ⁻³ or less.

Further, when the thin film transistor is formed using the lateral growth region, the height is higher than in the case of using the vertical growth region as shown in Embodiment 28 (in the case of Embodiment 28, the entire surface grows vertically). A semiconductor device having mobility can be obtained. After the pattern shown in FIG. 33E is formed, it is useful to further perform an etching treatment to remove the nickel element present on the pattern surface.

Next, a thermal oxide film 184 was formed on the pattern 183. This thermal oxide film was formed to a thickness of 200 Å by performing a heat treatment in an oxygen atmosphere at a temperature of 650 ° C. for 12 hours. This thermal oxide film becomes a part of the gate insulating film later when a thin film transistor is formed. Thereafter, if a thin film transistor is to be manufactured, a silicon oxide film is formed over the thermal oxide film 184 by a plasma CVD method or the like, and a gate insulating film is formed.

<< Example 31 >>
Example 31 is an example in which a thin film transistor arranged in a pixel region of an active matrix type liquid crystal display device or an active matrix type EL display device is manufactured. FIG. 34 shows a manufacturing process of this embodiment. First, in this example, a crystalline silicon film was formed on a glass substrate by the steps shown in Examples 28 and 30.

In the following, the description will be made mainly on the case of the process shown in Example 28, but the same applies to the case of the process shown in Example 30. After a crystalline silicon film was obtained with the configuration shown in Example 28, it was patterned to obtain the state shown in FIG. In the state shown in FIG. 34A, reference numeral 186 is a glass substrate, 187 is a base film, and 188 is an active layer formed of a crystalline silicon film. After the state shown in FIG. 34A was obtained, plasma treatment was performed in a reduced-pressure atmosphere in which oxygen and hydrogen were mixed. This plasma was generated by high frequency discharge.

有機 By the plasma treatment, organic substances existing on the exposed surface of the active layer 188 are removed. To be precise, the organic substances adsorbed on the surface of the active layer are oxidized by the oxygen plasma, and the oxidized organic substances are reduced and vaporized by the hydrogen plasma. Thus, the organic substances present on the exposed surface of the active layer 188 are removed. This removal of organic substances is very effective in suppressing the presence of fixed charges on the surface of the active layer 188. The fixed charge caused by the presence of the organic substance hinders the operation of the device and causes instability of the characteristics, and it is very useful to reduce the presence thereof.

After removing the organic matter, thermal oxidation was performed in an oxygen atmosphere at a temperature of 640 ° C. to form a thermal oxide film 185 of 100 Å. This thermal oxide film has a high interface characteristic with the semiconductor layer, and will form a part of the gate insulating film later. Thus, the state shown in FIG. 34A is obtained. After that, a silicon oxynitride film 189 constituting a gate insulating film was formed to a thickness of 1000 angstroms. As a film forming method, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O was used. Note that a plasma CVD method using a mixed gas of TEOS and N ₂ O can also be used.

This silicon oxynitride film 189 functions as a gate insulating film together with the thermal oxide film 185. It is effective to include a halogen element in the silicon oxynitride film. That is, by fixing the nickel element by the action of the halogen element, the gate insulating film is affected by the nickel element present in the active layer (the same applies when another metal element that promotes crystallization of silicon is used). Can be prevented from deteriorating as an insulating film.

(4) The use of the silicon oxynitride film as described above has a significance that the metal element hardly enters the gate insulating film due to its dense film quality. When a metal element enters the gate insulating film, its function as an insulating film is degraded, causing instability and variations in the characteristics of the thin film transistor. Note that a commonly used silicon oxide film can be used as the gate insulating film.

After the silicon oxynitride film 189 functioning as a gate insulating film was formed, an aluminum film (not shown) functioning as a gate electrode was formed later by a sputtering method. This aluminum film contained 0.2% by weight of scandium. The reason why scandium is contained in the aluminum film is to suppress generation of hillocks and whiskers in a later step. Here, the hillocks and whiskers mean that heating causes abnormal growth of aluminum, thereby forming needle-like or barbed protrusions.

(4) After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodized film was formed by using an ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) is about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation.

Next, a resist mask 191 was formed. Then, the aluminum film was patterned into the pattern indicated by reference numeral 190, thus obtaining the state shown in FIG. Here, the anodic oxidation was performed again. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 190 as an anode in this electrolytic solution, a porous anodic oxide film 193 is formed.

In the above process, the anodic oxide film 193 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 191 having high adhesion on the upper portion. This anodic oxide film 193 can be grown to a thickness of several μm. Here, the thickness is 6000 Å. The growth distance can be controlled by the anodic oxidation time.

Next, after removing the resist mask 191, a dense anodic oxide film was formed again. That is, anodic oxidation using the ethylene glycol solution containing tartaric acid of 3% by weight as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as shown by reference numeral 194 because the electrolytic solution enters (penetrates) into the porous anodic oxide film 193. The thickness of this dense anodic oxide film 194 was 1000 Å. This film thickness was controlled by the applied voltage.

Next, the exposed silicon oxynitride film 189 and thermal oxide film 185 were etched. Dry etching was used for this etching. Further, the porous anodic oxide film 193 was removed using a mixed acid obtained by mixing acetic acid, nitric acid and phosphoric acid. Thus, the state shown in FIG. 34D is obtained. After that, impurity ions were implanted.

Here, P (phosphorus) ions were implanted by a plasma doping method in order to manufacture an N-channel thin film transistor. In this step, regions 196 and 200 to be heavily doped and regions 197 and 199 to be lightly doped are formed. This is because part of the remaining silicon oxide film 195 functions as a semi-transmissive mask, and part of the implanted ions is shielded there.

(4) Next, the region into which the impurity ions were implanted was activated by irradiation with laser light or strong light. Here, the irradiation was performed by intense light irradiation by an ultraviolet lamp. Thus, the source region 196, the channel formation region 198, the drain region 200, and the low-concentration impurity regions 197 and 199 were formed in a self-aligned manner. Here, a region denoted by reference numeral 199 is a region called an LDD (lightly doped drain) region.

If the thickness of the dense anodic oxide film 194 is increased to 2000 Å or more, an offset gate region can be formed outside the channel formation region 198 with the thickness. Although the off-gate region is also formed in this embodiment, its size is small, so its contribution due to its existence is small, and the drawing is complicated, so that it is not shown in the drawing.

Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 201. Here, a silicon nitride film was used. As the interlayer insulating film, a layer made of a resin material may be formed over a silicon oxide film or a silicon nitride film. Further, a contact hole was formed, and a source electrode 202 and a drain electrode 203 were formed. Thus, the thin film transistor shown in FIG. 34E was completed.

<< Example 32 >>
The present embodiment 32 relates to a method for forming the gate insulating film 189 in the configuration shown in the actual embodiment 31 (FIG. 34). When a quartz substrate or a glass substrate having high heat resistance is used as a substrate, a thermal oxidation method can be used as a method for forming a gate insulating film. The thermal oxidation method can make the film quality dense, and is useful for obtaining a thin film transistor having stable characteristics.

That is, the oxide film formed by the thermal oxidation method is one of the most suitable as a gate insulating film because it is dense as an insulating film and can reduce mobile charges existing inside. In this embodiment, the heat treatment is performed in an oxidizing atmosphere at a temperature of 950 ° C. Other steps were performed in the same manner as in Example 31 to complete a thin film transistor as shown in FIG. At this time, it is effective to mix HCl or the like in an oxidizing atmosphere.

By doing so, the metal element present in the active layer can be fixed simultaneously with the formation of the thermal oxide film. It is also effective to mix N ₂ O gas in an oxidizing atmosphere to form a thermal oxide film containing a nitrogen component. Here, by optimizing the mixing ratio of the N ₂ O gas, it is possible to obtain a silicon oxynitride film by a thermal oxidation method. In this embodiment, it is not necessary to particularly form the thermal oxide film 185.

<< Example 33 >>
Example 33 is an example in which a thin film transistor is manufactured by a process different from the process of Example 31 (FIG. 34). FIG. 35 shows a manufacturing process of this example. First, a crystalline silicon film was formed on a glass substrate by the steps shown in Example 28 and Example 30. Next, by patterning them, the state shown in FIG. 35A was obtained. In the following, description will be made mainly on the case of the process shown in Example 30. However, the same applies to the case of the process shown in Example 28.

After the state shown in FIG. 35A was obtained, plasma treatment was performed in a reduced-pressure atmosphere of a mixture of oxygen and hydrogen. In the state shown in FIG. 35A, 205 is a glass substrate, 206 is a base film, and 207 is an active layer formed of a crystalline silicon film. Reference numeral 204 denotes a thermal oxide film formed again after removing the thermal oxide film for gettering. After that, a silicon oxynitride film 208 constituting a gate insulating film was formed to a thickness of 1000 Å. This film formation was performed by a plasma CVD method using a mixed gas of oxygen, silane and N ₂ O. As a film formation method, a plasma CVD method using a mixed gas of TEOS and N ₂ O may be used.

(4) The silicon oxynitride film 208 forms a gate insulating film together with the thermal oxide film 204. Note that a silicon oxide film can be used instead of the silicon oxynitride film. After the silicon oxynitride film 208 functioning as a gate insulating film was formed, an aluminum film (not illustrated), which functions as a gate electrode later, was formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium.

Next, a dense anodic oxide film (not shown) was formed. This anodic oxide film was formed by using an ethylene glycol solution containing 3% by weight of tartaric acid as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) is about 100 angstroms. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation.

Next, a resist mask 209 was formed. Then, the aluminum film was patterned into a pattern indicated by reference numeral 210. Here, the anodic oxidation is performed again. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 210 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 211 is formed.

In this step, the anodic oxide film 211 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 209 having high adhesion on the upper portion. This anodic oxide film 211 can be grown to a thickness of several μm. Here, the thickness is 6000 Å. The growth distance can be controlled by the time of anodic oxidation.

Next, after removing the resist mask 209, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as indicated by reference numeral 212 because the electrolytic solution enters (enters) the porous anodic oxide film 211. Here, the first implantation of impurity ions is performed, but this step may be performed after the resist mask 209 is removed. The source region 213 and the drain region 215 were formed by the implantation of the impurity ions. Note that no impurity ions are implanted into the region indicated by reference numeral 214.

(4) Next, the porous anodic oxide film 211 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 35D is obtained. After that, impurity ions were implanted again. The impurity ions were implanted under light doping conditions from the initial impurity ion implantation conditions. In this step, lightly doped regions 216 and 217 are formed. Then, a region indicated by reference numeral 218 is a channel formation region.

Next, the region into which the impurity ions have been implanted is activated by irradiation with laser light or strong light. Here, the activation is performed with laser light. Thus, the source region 213, the channel formation region 218, the drain region 215, and the low-concentration impurity regions 216 and 217 were formed in a self-aligned manner. Here, what is indicated by reference numeral 217 is a region called an LDD (lightly doped drain) region.

Next, a silicon oxide film, a silicon nitride film, or a laminated film thereof is formed as the interlayer insulating film 219. Here, a laminated film of a silicon oxide film and a silicon nitride film is formed. Note that the interlayer insulating film may be formed by forming a layer made of a resin material on a silicon oxide film or a silicon nitride film. Then, a contact hole was formed, and a source electrode 220 and a drain electrode 221 were formed. Thus, the thin film transistor shown in FIG. 35E was completed.

<< Example 34 >>
The thirty-fourth embodiment is an example in which an N-channel thin film transistor and a P-channel thin film transistor are configured to be complementary. The configuration shown in this embodiment can be used, for example, for various thin film integrated circuits integrated on an insulating surface. Further, for example, it can be used for a peripheral drive circuit of an active matrix type liquid crystal display device. FIG. 36 shows a manufacturing process of this embodiment.

First, as illustrated in FIG. 36A, a silicon oxide film or a silicon oxynitride film is formed as a base film 224 over a glass substrate 223. Of these, a silicon oxynitride film is preferably used, but this is used here. Next, an amorphous silicon film (not shown) was formed by a plasma CVD method. Note that the film may be formed by a low pressure thermal CVD method. Further, this amorphous silicon film was transformed into a crystalline silicon film by the method shown in Example 28.

Next, plasma treatment was performed in a mixed atmosphere of oxygen and hydrogen, and the obtained crystalline silicon film was patterned to obtain active layers 225 and 226. Thus, the state shown in FIG. Further, here, in order to suppress the influence of carriers moving on the side surface of the active layer, in the state shown in FIG. 36A, a temperature of 650 ° C. for 10 hours in a nitrogen atmosphere containing 3% by volume of HCl. Was heated.

When a trap level due to the presence of a metal element exists on the side surface of the active layer, the OFF current characteristic is deteriorated. Useful. Further, a thermal oxide film 222 and a silicon oxynitride film 227 forming a gate insulating film were formed. Here, when quartz is used as the substrate, it is desirable that the gate insulating film is formed only by the thermal oxide film using the above-described thermal oxidation method.

Next, an aluminum film (not shown) for forming a gate electrode was formed to a thickness of 4000 angstroms later. As a metal other than aluminum, a metal that can be anodized (for example, tantalum) can be used. After forming the aluminum film, an extremely thin and dense anodic oxide film was formed on the surface by the above-described method. Next, a resist mask (not shown) was arranged on the aluminum film, and the aluminum film was patterned.

Next, anodization was performed using the aluminum pattern obtained above as an anode to form porous anodic oxide films 230 and 231. The thickness of the porous anodic oxide film was 5000 Å. Further, anodic oxidation was performed again under the conditions for forming a dense anodic oxide film, and dense anodic oxide films 232 and 233 were formed. Here, the thickness of the dense anodic oxide films 232 and 233 was 800 Å. Thus, the state shown in FIG. 36B is obtained.

{Circle around (2)} The exposed silicon oxide film 227 and thermal oxide film 222 were removed by dry etching to obtain the state shown in FIG. Thereafter, the porous anodic oxide films 230 and 231 were removed using a mixed acid obtained by mixing acetic acid, nitric acid and phosphoric acid. Thus, the state shown in FIG. 36D is obtained. Here, resist masks were alternately arranged so that P (phosphorus) ions were implanted into the left thin film transistor and B (boron) ions were implanted into the right thin film transistor.

(4) By the implantation of the impurity ions, a source region 236 and a drain region 239 having a high concentration of N-type were formed in a self-aligned manner. At the same time, a weak N-type region 237 doped with P ions at a low concentration was formed, and a channel forming region 238 was formed simultaneously. The reason why the region having the weak N-type shown by reference numeral 237 is formed is that the remaining gate insulating film 234 exists. That is, the P ions transmitted through the gate insulating film 234 are partially shielded by the gate insulating film 234.

ソ ー ス The source region 243 and the drain region 240 having a strong P-type are formed in a self-aligned manner by the same principle and method as described above. At the same time, the low concentration impurity region 242 is formed at the same time, and the channel formation region 241 is formed at the same time. If the dense anodic oxide films 232 and 233 are as thick as 2000 angstroms, the offset gate region can be formed in contact with the channel forming region with the thickness.

In the case of the present embodiment, since the dense anodic oxide films 232 and 233 are as thin as 1000 angstroms or less, their existence can be ignored. Next, the region into which the impurity ions were implanted was annealed by laser light irradiation. In addition, it can also be performed by irradiation of strong light instead of laser light. Next, as shown in FIG. 36E, a silicon nitride film 244 and a silicon oxide film 245 were formed as interlayer insulating films. Each film thickness was 1000 Å. Note that the silicon oxide film 245 need not be formed.

Here, the thin film transistor is covered with the silicon nitride film. Since the silicon nitride film is dense and has good interface characteristics, such a structure can increase the reliability of the thin film transistor. Further, the interlayer insulating film 246 made of a resin material was formed by using the spin coating method. Here, the thickness of the interlayer insulating film 246 was set to 1 μm.

(5) Then, a contact hole was formed to form a source electrode 247 and a drain electrode 248 of the left N-channel thin film transistor. At the same time, the source electrode 249 and the drain electrode 248 of the thin film transistor on the right were formed (the drain electrode 248 was commonly arranged), and the thin film transistor shown in FIG. 36F was completed. In this manner, a thin film transistor circuit having a complementary CMOS structure can be formed.

In the structure shown in the thirty-fourth embodiment, a structure is obtained in which the thin film transistor is covered with a nitride film and further covered with a resin material. With this configuration, it is possible to achieve high durability in which mobile ions and moisture hardly enter. In addition, when a multilayer wiring is formed, it is possible to prevent a capacitance from being formed between the thin film transistor and the wiring.

<< Example 35 >>
The thirty-fifth embodiment is an example in which the nickel element is directly introduced into the surface of the base film in the process shown in the twenty-eighth embodiment. In this case, the nickel element is held in contact with the lower surface of the amorphous silicon film. In the present embodiment, after the formation of the base film, the nickel element is introduced, and first, the nickel element is brought into contact with and held on the surface of the base film.

In this example, nickel element was introduced by applying an aqueous solution of nickel acetate containing 10 ppm (in terms of weight) of nickel to the surface of the base film, and an amorphous silicon film was formed on this surface. Other steps were performed in the same manner as in Example 28, to obtain a crystalline silicon film 173 having a reduced nickel concentration, as shown in FIG. As a method for introducing a metal element that promotes crystallization of silicon, in addition to the above-described method using a solution, a sputtering method, a CVD method, a plasma treatment, or an adsorption method can be used.

<< Example 36 >>
In Example 36, irradiation with laser light was performed in the state of FIG. 33E, the state of FIG. 34A, or the state of FIG. This is an example in which the crystallinity of the pattern is improved. In this embodiment, a predetermined annealing effect can be obtained with a relatively low irradiation energy density by irradiating a laser beam in the state of FIGS. 33 (E), 34 (A), and 35 (A). Was completed. It is considered that this effect is due to the fact that the laser energy is applied to a small area, so that the energy efficiency used for annealing is increased.

<< Example 37 >>
Example 37 is an example in which the patterning of the active layer of the thin film transistor is devised in order to enhance the annealing effect by laser light irradiation. FIG. 37 shows a manufacturing process of the thin film transistor in this embodiment.

First, a silicon oxide film or a silicon oxynitride film 251 was formed as a base film on a Corning 1737 glass substrate 250. Next, an amorphous silicon film was formed to a thickness of 500 angstroms. For this film formation, a low pressure thermal CVD method was used. This amorphous silicon film becomes a crystalline silicon film 252 through the following crystallization step.

Next, the amorphous silicon film was crystallized by the method shown in Example 28 (see FIG. 32) and Example 29 (see FIG. 33) to obtain a crystalline silicon film. Thus, the state shown in FIG. 37A is obtained. Thereafter, a crystalline silicon film 252 was formed on each of the glass substrates according to the steps described in Example 28 and Example 29. That is, the amorphous silicon film was crystallized by a heat treatment using a nickel element, and a crystalline silicon film 252 was obtained. This treatment was performed by heating at 620 ° C. for 4 hours. Subsequent steps are the same for the crystalline silicon film according to any of the steps of Example 28 and Example 29.

(4) After obtaining the crystalline silicon film, a pattern 253 for forming an active layer of the thin film transistor was formed. In this case, the cross-sectional shape of this pattern was as shown by 254 in FIG. The pattern 253 is formed in such a shape 254 in order to suppress the shape of the pattern from being deformed in a processing step by irradiation with laser light.

In general, when a laser beam is applied to a pattern 258 made of a normal island-shaped silicon film formed on a base 257 as shown in FIG. The protrusion 260 is formed at the edge of the pattern 259 after light irradiation. This is considered to be caused by the fact that the energy of the irradiated laser beam is concentrated on the edge portion of the pattern where there is no escape of heat.

(4) The above phenomenon causes a failure of a wiring constituting the thin film transistor and a malfunction of the thin film transistor later. Therefore, in the configuration shown in this embodiment, the pattern 253 of the active layer has a sectional shape as shown in FIG. With such a structure, the pattern of the silicon film can be prevented from becoming a shape illustrated in FIG. 38B during irradiation with laser light.

Here, it is preferable that the angle of the portion indicated by reference numeral 254 is set to 20 ° to 50 ° with respect to the surface of the base film 251. It is not preferable to set the angle of the portion indicated by the reference numeral 254 to be less than 20 ° because the occupation area of the active layer increases and the difficulty in forming the active layer increases. Further, if the angle of the portion indicated by reference numeral 254 exceeds 50 °, the effect of suppressing the formation of the shape shown in FIG. 38B is reduced, which is also not preferable.

The pattern indicated by the symbol 253 can be realized by using isotropic dry etching at the time of patterning and controlling the dry etching conditions. Next, after obtaining a pattern having a shape indicated by 253 in FIG. 37B (which will later become an active layer), irradiation with laser light was performed as shown in FIG. 37C. In this step, the nickel element that is locally solidified in the pattern 253 can be diffused. Further, the crystallinity can be promoted.

(4) After the irradiation with the laser light, heat treatment was performed in an oxygen atmosphere containing HCl at 3% by volume to form a thermal oxide film 255. Here, a thermal oxide film of 100 Å was formed by performing heat treatment for 12 hours in an oxygen atmosphere containing HCl at 3% by volume at a temperature of 650 ° C. The nickel element contained in the pattern 253 is gettered on the thermal oxide film by the action of chlorine. At this time, the lump of the nickel element is broken and diffused by the laser light irradiation in the previous step, so that the nickel element is gettered effectively.

In the case where the configuration shown in this embodiment is adopted, gettering is also performed from the side surface of the pattern 253. This is useful for improving the OFF current characteristics and reliability of the finally completed thin film transistor. This is because the presence of a metal element that promotes the crystallization of silicon typified by the nickel element present on the side surface of the active layer is greatly related to an increase in OFF current and instability of characteristics.

後 After forming the thermal oxide film 255 for gettering shown in FIG. 37D, the thermal oxide film 255 was removed. Thus, the state shown in FIG. 37E is obtained. When a silicon oxide film is used as the base film 251, there is a concern that the silicon oxide film 251 may be etched in the step of removing the thermal oxide film 255. However, when the thickness of the thermal oxide film 255 is as thin as about 100 angstroms as shown in this embodiment, this does not cause much problem.

{After obtaining the state shown in FIG. 37E, a new thermal oxide film 256 was formed. This thermal oxide film was formed by heat treatment in an atmosphere of 100% oxygen. Here, the thermal oxide film 256 was formed to have a thickness of 100 Å by heat treatment in the oxygen atmosphere at a temperature of 650 ° C. This thermal oxide film 256 is effective in suppressing the surface of the pattern 253 from being roughened during the subsequent irradiation with laser light. This thermal oxide film 256 later constitutes a part of the gate insulating film.

(4) Since the thermal oxide film 256 has extremely good interface characteristics with the crystalline silicon film 253, it is useful to use the thermal oxide film 256 as a part of the gate insulating film. After the thermal oxide film 256 is formed, laser light irradiation may be performed again. Thus, the concentration of the nickel element was reduced, and a crystalline silicon film 253 having high crystallinity was obtained. Thereafter, a thin film transistor is manufactured through the steps shown in FIG. 34 or FIG.

<< Example 38 >>
Embodiment 38 is an example of a device for performing a heat treatment at a temperature equal to or higher than the strain point of a glass substrate. In the present invention, the step of gettering a metal element that promotes crystallization of silicon is preferably performed at a temperature as high as possible.

For example, in the case of using a Corning 1737 glass substrate (strain point 667 ° C.), the gettering effect of 700 ° C. is higher at 700 ° C. than at 650 ° C. when the nickel element is gettered by forming a thermal oxide film. Obtainable. However, when a Corning 1737 glass substrate is used and the heating temperature for forming the thermal oxide film is 700 ° C., the glass substrate is deformed.

The present embodiment is an example that solves this problem. That is, in the configuration shown in this embodiment, the glass substrate was placed on a platen made of quartz whose flatness was guaranteed, and the heat treatment was performed in this state. In this way, the flatness of the softened glass substrate was also maintained by the flatness of the surface plate. It is important that cooling is performed with the glass substrate placed on the surface plate. By employing such a structure, heat treatment can be performed even at a temperature equal to or higher than the strain point of the glass substrate.

<< Example 39 >>
Example 39 is an example in which a crystalline silicon film was obtained on a glass substrate by using a nickel element. In this example, first, a crystalline silicon film having high crystallinity was obtained by the action of the nickel element, and then irradiation with laser light was performed. By irradiating this laser beam, the crystallinity of the film is increased, and the nickel element locally concentrated in the film is diffused into the film. That is, the mass of nickel is eliminated.

酸化 Then, an oxide film was formed on the crystalline silicon film by a thermal oxidation method. At this time, the nickel element remaining in the crystalline silicon film is gettered in the thermal oxide film. However, since the nickel element is dispersed and present by the laser light irradiation, the gettering proceeds effectively. I do. Next, as a result of this gettering, the thermal oxide film containing a high concentration of nickel element was removed. Thus, a crystalline silicon film having high crystallinity and a low nickel element concentration on a glass substrate was obtained.

FIG. 39 is a diagram showing the manufacturing process of this example. First, a silicon oxynitride film 262 as a base film was formed to a thickness of 3000 Å on a Corning 1737 glass substrate (strain point 667 ° C.) 261. The silicon oxynitride film was formed by a plasma CVD method using silane, N ₂ O gas, and oxygen as source gases. Alternatively, a plasma CVD method using TEOS gas and N ₂ O gas may be used.

The silicon oxynitride film has a function of suppressing diffusion of impurities from a glass substrate (a glass substrate contains a large amount of impurities at a semiconductor manufacturing level) in a later step. . In order to maximize the function of suppressing the diffusion of the impurity, a silicon nitride film is optimal. However, the silicon nitride film is not practical because it peels off from the glass substrate due to stress. Further, a silicon oxide film can be used as a base film.

(4) It is important that the underlayer film 262 has as high a hardness as possible. This is concluded from the fact that in a durability test of the finally obtained thin film transistor, the higher the hardness of the base film (that is, the lower the etching rate), the higher the reliability. The reason is considered to be due to the effect of shielding impurities from the glass substrate during the manufacturing process of the thin film transistor.

(4) It is effective that the base film 262 contains a trace amount of a halogen element represented by chlorine. By doing so, in a later step, a metal element that promotes crystallization of silicon present in the semiconductor layer can be gettered by the halogen element. It is effective to perform a hydrogen plasma treatment after the formation of the base film. Further, it is effective to perform plasma processing in an atmosphere in which oxygen and hydrogen are mixed. This is effective in removing carbon components adsorbed on the surface of the base film and improving interface characteristics with a semiconductor film to be formed later.

Next, an amorphous silicon film 263 to be a crystalline silicon film later was formed to a thickness of 500 angstroms by a low pressure thermal CVD method. The reason why the reduced pressure thermal CVD method is used is that the crystalline silicon film obtained later has better film quality. Specifically, the film quality is dense. As a method other than the low pressure thermal CVD method, a plasma CVD method can be used.

The amorphous silicon film manufactured here preferably has an oxygen concentration in the film of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ . This is because oxygen plays an important role in a later metal element gettering step that promotes crystallization of silicon. However, care must be taken when the oxygen concentration is higher than the above concentration range, because crystallization of the amorphous silicon film is hindered. The other impurity concentration, for example, the impurity concentration of nitrogen or carbon is preferably as low as possible. Specifically, the concentration needs to be 2 × 10 ¹⁹ cm ⁻³ or less.

(4) The upper limit of the film thickness of the amorphous silicon film 265 is about 2000 angstroms. This is because it is disadvantageous if the film is too thick in order to obtain the effect of the subsequent laser light irradiation. The disadvantage of the thick film is that most of the laser light applied to the silicon film is absorbed on the surface of the film. Note that the lower limit of the film thickness of the amorphous silicon film 263 depends on the film forming method, but is practically about 200 Å.

Next, a nickel element was introduced to crystallize the amorphous silicon film 263. Here, the nickel element was introduced by applying a nickel acetate aqueous solution containing 10 ppm (weight conversion) of nickel to the surface of the amorphous silicon film 263. As a method for introducing the nickel element, in addition to the method using the above solution, a sputtering method, a CVD method, a plasma treatment, or an adsorption method can be used. Among them, the method using the above-mentioned solution is useful because it is simple and the concentration of the metal element can be easily adjusted.

に よ り By applying the nickel acetate aqueous solution as described above, a water film of the nickel acetate aqueous solution was formed as shown by 264 in FIG. 39 (A). Thereafter, excess solution was blown off using a spinner (not shown). In this manner, the nickel element is held in contact with the surface of the amorphous silicon film 263. In consideration of residual impurities in a subsequent heating step, it is preferable to use, for example, nickel sulfate instead of using a nickel acetate salt solution. This is because the nickel acetate salt solution contains carbon, which may be carbonized in the subsequent heating step and remain in the film. Adjustment of the introduction amount of the nickel element can be performed by adjusting the concentration of the nickel element in the solution.

(3) Then, in the state shown in FIG. 39B, heat treatment was performed at a temperature of 550 ° C. to 650 ° C. to crystallize the amorphous silicon film 263 to obtain a crystalline silicon film 265. This heat treatment was performed in a reducing atmosphere. The heat treatment is preferably performed at a temperature equal to or lower than the strain point of the glass substrate. Since the strain point of the Corning 1737 glass substrate is 667 ° C., the upper limit of the heating temperature in this case is preferably set to about 650 ° C. in view of a margin.

In this example, the reducing atmosphere was a nitrogen atmosphere containing 3% by volume of hydrogen, the heating temperature was 620 ° C., and the heating time was 4 hours. The reason why the atmosphere is a reducing atmosphere in the crystallization step by the above heat treatment is to prevent formation of an oxide during the heat treatment step. More specifically, the reaction with nickel and oxygen, because the NiO _X is prevented from undesirably formed on the surface of the film or within the film.

酸 素 Note that oxygen combines with nickel in a later gettering step, and greatly contributes to nickel gettering. However, it has been found that the combination of oxygen and nickel in the crystallization step inhibits crystallization. Therefore, in the step of crystallization by heating, it is important to suppress the formation of oxides as much as possible.

Therefore, the oxygen concentration in the atmosphere in which the heat treatment for crystallization is performed needs to be on the order of ppm, preferably 1 ppm or less. In addition, as the gas occupying most of the atmosphere in which the heat treatment for crystallization is performed, an inert gas such as argon or a mixed gas thereof other than nitrogen can be used.

(4) After the crystallization step by the heat treatment, the nickel element remains in a certain amount of lump. This was confirmed by observation with a TEM (transmission electron microscope). The cause of the fact that the nickel is present in some mass is not clear, but is believed to be related to some crystallization mechanism.

(4) Next, laser light irradiation was performed as shown in FIG. Here, a method was used in which a KrF excimer laser (wavelength: 248 nm) was used and a laser beam having a linear beam shape was irradiated while scanning. By irradiating this laser light, nickel element locally concentrated in the film 265 is dispersed to some extent as a result of crystallization by the above-described heat treatment. That is, the cluster of the nickel element can be eliminated and the nickel element can be dispersed in the film 265.

(4) Next, as shown in FIG. 39D, another heat treatment was performed. This heat treatment is performed to form a thermal oxide film for gettering the nickel element. Here, a heat treatment at a temperature of 640 ° C. was performed for 12 hours in a 100% oxygen atmosphere. As a result of this step, a thermal oxide film was formed to a thickness of 100 Å.

This step is for removing the nickel element intentionally mixed at the initial stage for crystallization (the same applies to other metal elements that promote crystallization of silicon) from the crystalline silicon film 265. It is. This heat treatment is performed at a higher temperature than the heat treatment performed for performing the crystallization, which is an important condition for effectively performing gettering of the nickel element. Note that the heat treatment can be performed at a temperature equal to or lower than the temperature of the heat treatment performed for crystallization, but the effect is small.

This heat treatment is performed at a temperature of 600 ° C. to 750 ° C. after satisfying the above conditions. The gettering effect of the nickel element in this step can be remarkably obtained when the temperature is higher than 600 ° C. In this step, the nickel element dispersed by the laser light irradiation is effectively gettered in the oxide film. Note that the upper limit of the heat treatment temperature is limited by the strain point of the glass substrate used.

加熱 Care must be taken if heat treatment is performed at a temperature equal to or higher than the strain point of the glass substrate used, since the substrate will be deformed. In this regard, as described in the section of << Embodiment 38 >>, the glass substrate is placed on a platen made of, for example, quartz, whose flatness is guaranteed, and heat treatment is performed in this state. Thereby, heat treatment can be performed at a temperature equal to or higher than the strain point of the glass substrate used.

(4) By forming the thermal oxide film 266, the thickness of the crystalline silicon film 263 becomes about 450 Å. In this heat treatment, when the heating temperature is 600 ° C. to 750 ° C., the treatment time (heating time) is 10 hours to 48 hours, typically 24 hours. Of course, this processing time may be set as appropriate depending on the thickness of the oxide film to be obtained. In this gettering, oxygen existing in the crystalline silicon film plays an important role. That is, the gettering of the nickel element proceeds in the form of nickel oxide formed by the combination of oxygen and nickel.

As described above, if the concentration of oxygen is too high, it becomes an element that hinders crystallization of the amorphous silicon film 263 in the crystallization step shown in FIG. However, as mentioned above, its presence plays an important role in the nickel gettering process. Therefore, it is important to control the concentration of oxygen existing in the amorphous silicon film serving as the starting film. In addition, in the above-described process, since the nickel element is gettered in the oxide film to be formed, the nickel concentration in the oxide film naturally becomes higher than that in other regions.

{Circle around (2)} In the vicinity of the interface between the silicon film 265 and the thermal oxide film 266 on the thermal oxide film 266 side, a tendency for the nickel element to increase was observed. This is probably because the region where gettering is mainly performed is on the oxide film side near the interface between the silicon film and the oxide film. It is considered that gettering progresses near the interface due to the presence of stress and defects near the interface.

Next, the oxide film 266 containing nickel at a high concentration was removed. The removal of the oxide film 266 is performed by wet etching or dry etching using buffered hydrofluoric acid (another hydrofluoric acid-based etchant). Here, wet etching using buffered hydrofluoric acid is performed. Thus, as shown in FIG. 39E, a crystalline silicon film 267 with a reduced nickel concentration was obtained.

In addition, since the nickel element is contained at a relatively high concentration in the vicinity of the surface of the obtained crystalline silicon film 267, the etching of the oxide film 266 is further advanced to slightly overlie the surface of the crystalline silicon film 267. Etching is effective. Further, it is effective to irradiate laser light again after removing the thermal oxide film 266 to further promote the crystallinity of the obtained crystalline silicon film 267.

That is, it is effective to irradiate the laser beam again after the nickel element is gettered. Therefore, in the present embodiment, a KrF excimer laser (wavelength: 248 nm) was used as a laser beam. As the laser light, a XeCl excimer laser (wavelength 308 nm) or another type of excimer laser may be used. Further, a configuration may be employed in which irradiation with, for example, ultraviolet light or infrared light is performed instead of laser light.

<< Example 40 >>
The forty-ninth embodiment is an example in which Cu is used as a metal element for promoting crystallization of silicon in the configuration shown in the thirty-ninth embodiment. In this case, cupric acetate [Cu (CH ₃ COO) ₂ ], cupric chloride (CuCl ₂ 2H ₂ O) or the like may be used as a solution for introducing Cu. In this embodiment, cupric chloride (CuCl ₂ 2H ₂ O) is used, and in the other cases, as in the embodiment 39, as shown in FIG. 267 could be obtained.

<< Example 41 >>
The present embodiment 41 is an example in which the crystal growth of a form different from that of the embodiment 39 is performed. The present embodiment relates to a method of performing crystal growth in a direction parallel to a substrate called lateral growth using a metal element that promotes crystallization of silicon. FIG. 40 shows a manufacturing process of this embodiment.

First, a silicon oxynitride film having a thickness of 3000 Å was formed as a base film 269 on a Corning 1737 glass substrate 268. Note that a quartz substrate or the like may be used instead of the glass substrate. Next, an amorphous silicon film 270 serving as a starting film of the crystalline silicon film was formed to a thickness of 600 angstroms by a low pressure thermal CVD method. It is preferable that the thickness of the amorphous silicon film be 2000 Å or less as described above. Note that a plasma CVD method may be used instead of the low pressure thermal CVD method.

Next, a silicon oxide film (not shown) was formed to a thickness of 1500 angstroms and patterned to form a mask indicated by reference numeral 271. This mask has an opening formed in a region indicated by reference numeral 272. In the region where the opening 272 is formed, the amorphous silicon film 270 is exposed. The opening 272 has an elongated rectangular shape extending in the longitudinal direction from the depth of the drawing to the front. The width of the opening 272 is suitably 20 μm or more, and the length in the longitudinal direction may be formed as required. In the present embodiment, the width is 35 μm and the length is 2 cm.

(5) Next, as in Example 40, a nickel acetate aqueous solution containing 10 ppm by weight of nickel element was applied. Then, spin drying was performed using a spinner (not shown) to remove excess solution. Thus, a state where the nickel element is held in contact with the exposed surface of the amorphous silicon film 270 as shown by the dotted line 273 in FIG.

Next, a heat treatment was performed at 640 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen and containing as little oxygen as possible. Then, crystal growth in a direction parallel to the substrate 268 as indicated by 274 in FIG. 40B progressed. This crystal growth proceeds from the region of the opening 272 into which the nickel element has been introduced toward the periphery. The crystal growth in the direction parallel to the substrate is referred to as lateral growth or lateral growth in this specification.

横 Under the conditions shown in this embodiment, the lateral growth can be performed over 100 μm. Thus, a silicon film 275 having a region grown laterally was obtained. In the region where the opening 272 is formed, crystal growth proceeds in the vertical direction called vertical growth from the surface of the silicon film to the interface of the base.

Next, the mask 271 made of the silicon oxide film for selectively introducing the nickel element was removed to obtain a state shown in FIG. In this state, in the silicon film 275, there are a vertical growth region, a horizontal growth region, and a region that has not been subjected to crystal growth (amorphous state). In this state, the nickel element is unevenly distributed in the film. In particular, the nickel element is present at a relatively high concentration in the region where the opening 272 is formed and in the tip portion of the crystal growth indicated by 274.

Next, laser light irradiation was performed. Here, as in the case of Example 39, irradiation with a KrF excimer laser was performed to diffuse the unevenly distributed nickel element, so that gettering was easily performed in a later gettering step. After the laser light irradiation was completed, a heat treatment at a temperature of 650 ° C. was performed for 12 hours in an atmosphere of 100% oxygen.

In this step, an oxide film 276 containing nickel at a high concentration is formed in the film, and at the same time, the nickel element concentration in the crystalline silicon film 275 can be relatively reduced. In this embodiment, a thermal oxide film indicated by reference numeral 276 was formed to a thickness of 100 Å. This thermal oxide film contains a high concentration of nickel element gettered by the film formation.

{Circle around (5)} By forming the thermal oxide film 276, the crystalline silicon film 275 has a thickness of about 500 angstroms. Next, the thermal oxide film 276 containing nickel at a high concentration was removed. The crystalline silicon film in this state has a concentration distribution such that the nickel element exists at a high concentration toward the surface of the crystalline silicon film. This state is due to the fact that the nickel element was gettered on the thermal oxide film when the thermal oxide film 276 was formed.

Therefore, it is useful to further etch the surface of the crystalline silicon film after removing the thermal oxide film 276 to remove the region where the nickel element exists at a high concentration. That is, by etching the surface of the crystalline silicon film in which the nickel element exists at a high concentration, a crystalline silicon film with a further reduced nickel element concentration can be obtained. However, in this case, it is necessary to consider the thickness of the finally obtained crystalline silicon film.

Next, a pattern 277 consisting of a lateral growth region was formed by patterning. In this manner, the concentration of the nickel element remaining in the pattern 277 formed of the lateral growth region can be further reduced as compared with the case shown in Embodiment 39. This is also because the concentration of the metal element contained in the lateral growth region is originally low. Specifically, the concentration of the nickel element in the pattern 277 composed of the lateral growth region can be easily set to the order of 10 ¹⁷ cm ⁻³ or less.

Further, when the thin film transistor is formed using the lateral growth region, the thin film transistor is higher than in the case of using the vertical growth region as shown in the embodiment 39 (in the case of the embodiment 39, the entire surface is grown vertically). A semiconductor device having mobility can be obtained. After the pattern shown in FIG. 40E is formed, it is useful to further perform an etching treatment to remove the nickel element present on the pattern surface.

(4) After forming the pattern 277 as described above, the thermal oxide film 278 was formed. This thermal oxide film 278 was formed to a thickness of 100 Å by performing a heat treatment in an oxygen atmosphere at a temperature of 650 ° C. for 12 hours. This thermal oxide film will later become a part of the gate insulating film if it constitutes a thin film transistor. After that, if a thin film transistor is to be manufactured, a silicon oxide film is formed over the thermal oxide film 278 by a plasma CVD method or the like, and a gate insulating film is formed together with the thermal oxide film 278.

<< Example 42 >>
Example 42 is an example in which a thin film transistor arranged in a pixel region of an active matrix type liquid crystal display device or an active matrix type EL display device is manufactured. FIG. 41 is a diagram showing the manufacturing process of this example.

First, a crystalline silicon film was formed on a glass substrate by the steps shown in Example 39 and Example 41. Since the subsequent steps are the same for both, the case where a crystalline silicon film is obtained with the configuration shown in Example 39 will be described below. By patterning the crystalline silicon film, a state shown in FIG. 41A was obtained. In this state, 280 is a glass substrate, 281 is a base film, and 282 is an active layer formed of a crystalline silicon film. After obtaining the state shown in FIG. 41A, plasma treatment was performed in a reduced-pressure atmosphere in which oxygen and hydrogen were mixed. This plasma was generated by high frequency discharge.

有機 By this plasma treatment, organic substances present on the exposed surface of the active layer 282 are removed. To be precise, the organic substance adsorbed on the surface of the active layer is oxidized by oxygen plasma, and the oxidized organic substance is reduced and vaporized by hydrogen plasma. Thus, the organic substances present on the exposed surface of the active layer 282 are removed. This removal of organic substances is very effective in suppressing the presence of fixed charges on the surface of the active layer 282. The fixed charge caused by the presence of the organic substance hinders the operation of the device and causes instability of the characteristics, and it is very useful to reduce the presence thereof.

After removing the organic substances, thermal oxidation was performed in an oxygen atmosphere at a temperature of 640 ° C. to form a thermal oxide film 279 of 100 Å. This thermal oxide film has a high interface characteristic with the semiconductor layer, and will form a part of the gate insulating film later. Thus, the state shown in FIG. After that, a silicon oxynitride film 283 forming a gate insulating film was formed to a thickness of 1000 Å. As a film formation method, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O, a plasma CVD method using a mixed gas of TEOS and N ₂ O, and the like are used. A mixed gas of silane and N ₂ O was used.

This silicon oxynitride film 283 functions as a gate insulating film together with the thermal oxide film 279. It is effective to include a halogen element in the silicon oxynitride film. That is, by fixing the nickel element by the action of the halogen element, the insulating element of the gate insulating film is affected by the nickel element (the same applies to other metal elements that promote crystallization of silicon) existing in the active layer. Function can be prevented from deteriorating.

(4) The use of a silicon oxynitride film as the above film has a significant advantage that a metal element hardly enters the gate insulating film due to its dense film quality. When a metal element enters (penetrates) into the gate insulating film, its function as an insulating film is reduced, which causes instability and variations in the characteristics of the thin film transistor. Note that a commonly used silicon oxide film can be used as the gate insulating film.

After the silicon oxynitride film 283 functioning as a gate insulating film was formed, an aluminum film functioning as a gate electrode was formed later by a sputtering method. The aluminum film (not shown, which becomes a pattern 284 after patterning described later) contained scandium at 0.2% by weight. Scandium is contained in the aluminum film in order to suppress generation of hillocks and whiskers in a later step. Here, the hillocks and whiskers mean that heating causes abnormal growth of aluminum, thereby forming needle-like or barbed protrusions.

(4) After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodized film was formed by using an ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) was about 100 angstroms. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation.

(5) After forming a resist mask 285, the aluminum film was patterned into a pattern indicated by 284. Thus, the state shown in FIG. 41B is obtained. Here, anodic oxidation was performed again. In this example, a 3% by weight aqueous solution of oxalic acid was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 284 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 287 is formed.

In this step, the anodic oxide film 287 is selectively formed on the side surface of the aluminum pattern 284 due to the presence of the resist mask 285 having high adhesion on the upper part. This anodic oxide film can be grown to a thickness of several μm. Here, the thickness was set to 6000 Å. The growth distance can be controlled by the time of anodic oxidation.

Next, after removing the resist mask 285, a dense anodic oxide film was formed again. That is, anodic oxidation using the ethylene glycol solution containing tartaric acid of 3% by weight as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as indicated by reference numeral 288 because the electrolytic solution enters the porous anodic oxide film 287. The thickness of this dense anodic oxide film 288 was 1000 Å. This film thickness was controlled by adjusting the applied voltage.

(4) Here, the exposed silicon oxynitride film 283 and thermal oxide film 279 were etched. For this etching, dry etching was used. Next, the porous anodic oxide film 287 was removed using a mixed acid solution obtained by mixing acetic acid, nitric acid, and phosphoric acid. After obtaining the state shown in FIG. 41D in this manner, impurity ions were implanted. Here, P (phosphorus) ions were implanted by a plasma doping method in order to manufacture an N-channel thin film transistor. In this step, regions 290 and 294 to be heavily doped and regions 291 and 293 to be lightly doped are formed. This is because a part of the remaining silicon oxide film 289 functions as a semi-transparent mask, and a part of the implanted ions is shielded there.

(4) Next, the region into which the impurity ions have been implanted is activated by irradiating laser light or intense light. Here, an infrared lamp is used. Thus, a source region 290, a channel formation region 292, a drain region 294, and low-concentration impurity regions 291 and 293 were formed in a self-aligned manner. Here, what is indicated by reference numeral 293 is a region called an LDD (lightly doped drain) region.

When the thickness of the dense anodic oxide film 288 is set to be as large as 2000 Å or more, an offset gate region can be formed outside the channel formation region 292 with the thickness. Although the offset gate region is also formed in the present embodiment, its contribution is small due to its small size, and the drawing is complicated.

Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 295. Here, a silicon nitride film was formed. The interlayer insulating film 295 may be formed by forming a layer made of a resin material on a silicon oxide film or a silicon nitride film. Further, a contact hole was formed, and a source electrode 296 and a drain electrode 297 were formed. Thus, the thin film transistor shown in FIG. 39E was completed.

<< Example 43 >>
The present embodiment 43 relates to a method for forming the gate insulating film 283 in the configuration shown in the actual embodiment 42. When a quartz substrate or a glass substrate having high heat resistance is used as a substrate, a thermal oxidation method can be used as a method for forming a gate insulating film. In this example, a thermal oxidation method was used to form the gate insulating film 283, and the other steps were performed in the same manner as in Example 42 to obtain a thin film transistor having the structure shown in FIG.

(4) The thermal oxidation method can make the film quality dense and is useful for obtaining a thin film transistor having stable characteristics. That is, an oxide film formed by a thermal oxidation method is one of the most suitable as a gate insulating film because it is dense as an insulating film and can reduce mobile charges existing therein.

<< Example 44 >>
Example 44 is an example in which a thin film transistor was manufactured by a process different from that shown in FIG. FIG. 42 is a diagram showing the manufacturing process of this example. First, a crystalline silicon film was formed on a glass substrate by the steps described in Example 39 (FIG. 38) and Example 41 (FIG. 40). The following steps are the same for both. Next, by patterning it, the state shown in FIG. 42A was obtained.

After the state shown in FIG. 42A was obtained, plasma treatment was performed in a reduced-pressure atmosphere of a mixture of oxygen and hydrogen. In the state shown in FIG. 42A, 299 is a glass substrate, 300 is a base film, and 301 is an active layer formed of a crystalline silicon film. Reference numeral 298 denotes a thermal oxide film formed again after removing the thermal oxide film for gettering. After the state shown in FIG. 42A was obtained, a silicon oxynitride film 302 included in the gate insulating film was formed to a thickness of 1000 angstroms. For the film formation, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O, a plasma CVD method using a mixed gas of TEOS and N ₂ O, and the like are used. A mixed gas with N ₂ O was used.

(4) The silicon oxynitride film 302 and the thermal oxide film 298 constitute a gate insulating film. Note that a silicon oxide film can be used instead of the silicon oxynitride film. After the silicon oxynitride film 302 functioning as a gate insulating film was formed, an aluminum film (not shown, which becomes a pattern 304 after patterning to be described later), which later functions as a gate electrode, was formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium.

After forming the aluminum film, a dense anodic oxide film (not shown) was formed. The anodic oxide film was formed using an ethylene glycol solution containing tartaric acid at 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) is about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by adjusting the voltage applied during anodic oxidation.

Next, a resist mask 303 was formed. Then, after the aluminum film was patterned into a pattern indicated by 304, anodic oxidation was performed again. Here, a 3% by weight aqueous solution of oxalic acid was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 304 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 305 is formed.

In this step, the anodic oxide film 305 is selectively formed on the side surface of the aluminum pattern due to the presence of the resist mask 303 having high adhesion on the upper portion. This anodic oxide film 305 can be grown to a thickness of several μm. Here, the thickness was set to 6000 Å. The growth distance can be controlled by the time of anodic oxidation.

Next, after removing the resist mask 303, a dense anodic oxide film was formed again. That is, anodic oxidation using the ethylene glycol solution containing tartaric acid of 3% by weight as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as indicated by reference numeral 306 because the electrolytic solution enters the porous anodic oxide film 305. Here, the first implantation of impurity ions was performed. Note that this step may be performed after the resist mask 303 is removed. By the implantation of the impurity ions, a source region 307 and a drain region 309 are formed. At this time, no impurity ions are implanted into the region indicated by reference numeral 308.

(4) Next, the porous anodic oxide film 305 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 42D is obtained. After that, impurity ions are implanted again. The impurity ions were implanted under light doping conditions compared to the initial impurity ion implantation conditions. In this step, lightly doped regions 310 and 311 are formed, and a region indicated by 312 becomes a channel forming region.

Next, the region into which the impurity ions are implanted is activated by irradiating laser light or strong light. Here, laser light was used. Thus, the source region 307, the channel formation region 312, the drain region 309, and the low-concentration impurity regions 310 and 311 were formed in a self-aligned manner. Here, what is indicated by reference numeral 311 is a region called an LDD (lightly doped drain) region.

Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 313. Here, a laminated film of both was formed. The interlayer insulating film may be formed by forming a layer made of a resin material on a silicon oxide film or a silicon nitride film. Then, a contact hole was formed, and a source electrode 314 and a drain electrode 315 were formed. Thus, the thin film transistor shown in FIG. 42E was completed.

<< Example 45 >>
The forty-fifth embodiment is an example in which an N-channel thin film transistor and a P-channel thin film transistor are configured to be complementary. FIG. 43 is a diagram showing the steps of this embodiment. The configuration shown in this embodiment can be used, for example, for various thin film integrated circuits integrated on an insulating surface. Further, for example, it can be used for a peripheral drive circuit of an active matrix type liquid crystal display device.

First, as shown in FIG. 43A, a silicon oxide film or a silicon oxynitride film was formed as a base film 318 over a glass substrate 317. Of these, a silicon oxynitride film is preferably used, but this is used in the present embodiment. Next, an amorphous silicon film (not shown) is formed by a plasma CVD method or a low pressure thermal CVD method. Here, the low pressure thermal CVD method is used. Further, this amorphous silicon film was transformed into a crystalline silicon film by the method shown in the above-mentioned Example 39.

Next, plasma treatment was performed in a mixed atmosphere of oxygen and hydrogen, and the obtained crystalline silicon film was patterned to obtain active layers 319 and 320. Thus, the state shown in FIG. Here, in order to suppress the influence of carriers moving on the side surface of the active layer, in the state shown in FIG. 43A, heating is performed at 650 ° C. for 10 hours in a nitrogen atmosphere containing 3% by volume of HCl. Processing was performed.

If a trap level due to the presence of a metal element exists on the side surface of the active layer, the OFF current characteristics are deteriorated. Therefore, the treatment shown here should be performed to reduce the density of the level on the side surface of the active layer. Is useful. Next, a thermal oxide film 316 and a silicon oxynitride film 321 forming a gate insulating film were formed. Here, when quartz is used as the substrate, it is desirable to form the gate insulating film using only the thermal oxide film by using the above-described thermal oxidation method.

Next, an aluminum film (not shown, which becomes a pattern after patterning described later) for forming a gate electrode later was formed to a thickness of 4000 angstroms. In addition to the aluminum film, an anodizable metal (for example, tantalum) can be used. After forming the aluminum film, an extremely thin and dense anodic oxide film was formed on the surface by the above-described method.

Next, a resist mask (not shown) was arranged on the aluminum film, and the aluminum film was patterned. Further, anodic oxidation was performed using the obtained aluminum pattern as an anode to form porous anodic oxide films 324 and 325. The thickness of the porous anodic oxide film was 5000 Å.

陽極 Here, anodic oxidation was performed again under the condition of forming a dense anodic oxide film, and dense anodic oxide films 326 and 327 were formed. Here, the thickness of the dense anodic oxide films 326 and 327 was set to 800 Å. Thus, the state shown in FIG. 43B was obtained. Next, the exposed silicon oxide film 321 and thermal oxide film 316 were removed by dry etching to obtain a state shown in FIG.

(5) Thereafter, the porous anodic oxide films 324 and 325 were removed using a mixed acid solution obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 43D is obtained. Next, P (phosphorus) ions were implanted into the left thin film transistor and B (boron) ions were implanted into the right thin film transistor with alternately arranged resist masks. By the implantation of the impurity ions, a source region 330 and a drain region 333 having a high concentration of N-type were formed in a self-aligned manner.

(4) At the same time, a weakly N-type region 331 doped with P ions at a low concentration is formed at the same time, and a channel forming region 332 is formed at the same time. The reason why the region having the weak N-type shown by reference numeral 331 is formed is that the remaining gate insulating film 328 exists. That is, P ions transmitted through the gate insulating film 328 are partially shielded by the gate insulating film 328.

Further, by the same principle and method as described above, a source region 337 and a drain region 334 having a strong P-type are formed in a self-aligned manner, a low-concentration impurity region 336 is formed at the same time, and a channel formation region 335 is formed at the same time. You. When the dense anodic oxide films 326 and 327 are as thick as 2000 angstroms, the offset gate region can be formed in contact with the channel forming region with the thickness.

In the case of the present embodiment, since the dense anodic oxide films 326 and 327 are as thin as 1000 angstroms or less, their existence can be neglected. Next, laser light irradiation was performed to anneal the region into which the impurity ions had been implanted. Note that intense light irradiation may be performed instead of laser light. Then, as shown in FIG. 43E, a silicon nitride film 338 and a silicon oxide film 339 were formed as interlayer insulating films, each having a thickness of 1000 angstroms. Note that in this case, the silicon oxide film 339 does not have to be formed.

薄膜 ト ラ ン ジ ス タ Here, the thin film transistor is covered with the silicon nitride film. Since the silicon nitride film is dense and has good interface characteristics, such a structure can increase the reliability of the thin film transistor. Further, an interlayer insulating film 340 made of a resin material was formed by using a spin coating method. Here, the thickness of the interlayer insulating film 340 is 1 μm.

Then, a contact hole was formed, and a source electrode 341 and a drain electrode 342 of the left N-channel thin film transistor were formed, and simultaneously, a source electrode 343 and a drain electrode 342 of the right thin film transistor were formed. Here, the drain electrode 342 is arranged in common to both. Thus, a thin film transistor circuit having a complementary CMOS structure was formed.

In the structure shown in this embodiment, a structure is obtained in which the thin film transistor is covered with a silicon nitride film and further covered with a resin material. With this configuration, it is possible to achieve high durability in which mobile ions and moisture hardly enter. In addition, when a multilayer wiring is formed, it is possible to prevent a capacitance from being formed between the thin film transistor and the wiring.

<< Example 46 >>
The forty-sixth embodiment is an example in which the nickel element is directly introduced into the surface of the base film in the process shown in the forty-ninth embodiment. In this case, the nickel element is held in contact with the lower surface of the amorphous silicon film. In this embodiment, after the formation of the base film, the nickel element was introduced using an aqueous nickel acetate solution, and the nickel element was first brought into contact with and held on the surface of the base film.

(4) In other steps, in the same manner as in Example 39, a crystalline silicon film 267 with a reduced nickel concentration was obtained as shown in FIG. As a method for introducing the nickel element, a sputtering method, a CVD method, and an adsorption method can be used in addition to the method using a solution as in this embodiment. Further, even when a metal element other than nickel, which promotes crystallization of silicon, is used, a crystalline silicon film having a reduced concentration of the metal can be obtained in a similar manner.

<< Example 47 >>
In Example 47, laser light irradiation was performed in the state of FIG. 40E, the state of FIG. 41A, or the state of FIG. This is an example in which the crystallinity of the pattern is improved. When laser light irradiation is performed in the state of FIG. 40E, FIG. 41A, or FIG. 42A, a predetermined annealing effect can be obtained with a relatively low irradiation energy density. This is presumably because the laser energy is applied to a small area, which increases the energy efficiency used for annealing.

<< Example 48 >>
The forty-eighth embodiment is an example in which the active layer of the thin film transistor is patterned to improve the annealing effect by laser light irradiation. FIG. 44 is a diagram showing a manufacturing process of the thin film transistor in this embodiment. First, a silicon oxide film 345 was formed as a base film on a Corning 1737 glass substrate 344. As the base film, a silicon oxynitride film can be used.

Next, an amorphous silicon film (not shown) was formed to a thickness of 500 angstroms. The low pressure thermal CVD method was used for the film formation. This amorphous silicon film becomes a crystalline silicon film 346 through a crystallization step later. Next, the amorphous silicon film (not shown) was crystallized by the method shown in Example 39 (see FIG. 39) and Example 41 (see FIG. 40), respectively, to obtain a crystalline silicon film.

Thus, the state shown in FIG. 44 (A) was obtained. Hereinafter, the case according to the embodiment 39 will be mainly described, but the same applies to the case according to the embodiment 41. After obtaining the state shown in FIG. 44A, a crystalline silicon film 346 was formed over a glass substrate according to the manufacturing process of Example 39 (FIG. 39). That is, the amorphous silicon film was crystallized by a heat treatment using a nickel element, and a crystalline silicon film 346 was obtained. The heat treatment conditions here were heating at a temperature of 620 ° C. for 4 hours.

(4) After obtaining the crystalline silicon film, a pattern for forming an active layer of the thin film transistor was formed. In this case, the cross-sectional shape of this pattern is set to a shape indicated by 347 in FIG. The reason for forming the pattern 347 as shown in FIG. 44B is to suppress the shape of the pattern from being deformed in the subsequent processing step by laser light irradiation.

As described above, when the laser light is applied to the pattern 258 made of a normal island-shaped silicon film formed on the base 257 as shown in FIG. 38A, as shown in FIG. In addition, the projection 260 is formed at the edge of the pattern 259 after the laser light irradiation. This is considered to be caused by the fact that the energy of the irradiated laser beam is concentrated on the edge of the pattern where there is no escape of heat.

(4) The convex portion 260 formed by this phenomenon causes a failure of a wiring forming the thin film transistor and a malfunction of the thin film transistor later. Therefore, in the configuration shown in this embodiment, the pattern 347 of the active layer has a cross-sectional shape as shown in FIG. With such a structure, the pattern of the silicon film can be prevented from becoming a shape illustrated in FIG. 38B during irradiation with laser light. The pattern indicated by reference numeral 347 can be realized by using isotropic dry etching at the time of patterning and controlling the dry etching conditions.

Here, it is preferable that the angle of the portion indicated by reference numeral 348 be 20 ° to 50 ° with respect to the surface of the base film 345. It is not preferable to set the angle of the portion indicated by reference numeral 348 to an angle less than 20 °, because the area occupied by the active layer increases and the difficulty of forming the active layer increases. Further, setting the angle indicated by reference numeral 348 to an angle exceeding 50 ° is not preferable because the effect of suppressing the formation of the convex portion 260 as illustrated in FIG. 38B is reduced. .

{Circle around (4)} After obtaining a pattern having a shape indicated by reference numeral 347 in FIG. 44B (which will later become an active layer), irradiation with laser light was performed as shown in FIG. 44C. By this step, the nickel element locally solidified in the pattern 347 can be diffused, and its crystallinity can be promoted. Next, after the laser light irradiation was completed, heat treatment was performed in an oxygen atmosphere to form a thermal oxide film 349. Here, a thermal oxide film 349 of 100 Å was formed by performing heat treatment at 650 ° C. for 12 hours in an atmosphere of 100% oxygen.

(4) The nickel element contained in the pattern 347 is gettered on the thermal oxide film 349 by the action of oxygen. At this time, since the cluster of the nickel element is broken by the irradiation of the laser beam in the previous step, gettering of the nickel element is effectively performed. Note that when halogen is contained as an atmosphere for the heat treatment, gettering of the nickel element can be performed more effectively.

In the case where the configuration shown in this embodiment is adopted, gettering is also performed from the side surface of the pattern 347. This is useful for improving the OFF current characteristics and reliability of the finally completed thin film transistor. This is because the presence of the nickel element (the same applies to other metal elements that promote crystallization of silicon) existing on the side surface of the active layer is greatly related to an increase in OFF current and instability of characteristics.

後 After forming the thermal oxide film 349 for gettering shown in FIG. 44D, the thermal oxide film 349 was removed. Thus, the state shown in FIG. When a silicon oxide film is used as the base film 345 as in this embodiment, there is a concern that the silicon oxide film 345 may be etched in the step of removing the thermal oxide film 349. However, as shown in this embodiment, when the thickness of the thermal oxide film 349 is as thin as about 100 Å, this does not cause much problem.

{After obtaining the state shown in FIG. 44E, a new thermal oxide film 350 was formed. This thermal oxide film 350 was formed by a heat treatment in an atmosphere of 100% oxygen. Here, the thermal oxide film 350 was formed to a thickness of 100 Å by a heat treatment at 650 ° C. for 4 hours in an oxygen atmosphere. This thermal oxide film 350 is effective in suppressing the surface of the pattern 347 from being roughened when the laser light is irradiated later, and forms a part of the gate insulating film later.

(4) Since the thermal oxide film 350 has extremely good interface characteristics with the crystalline silicon film, it is useful to use the thermal oxide film 350 as a part of the gate insulating film. After the thermal oxide film 350 is formed, laser light irradiation may be performed again. Thus, the concentration of the nickel element was reduced, and a crystalline silicon film 347 having high crystallinity was obtained. Thereafter, through the steps shown in FIGS. 41 to 43, a thin film transistor is manufactured.

<< Example 49 >>
The forty-ninth embodiment is an example of a contrivance when a heat treatment is performed at a temperature equal to or higher than the strain point of the glass substrate. In the present invention, after crystallization of amorphous silicon using a metal element that promotes crystallization of silicon, the metal element is gettered, but this gettering step is preferably performed at a temperature as high as possible. .

For example, even when Corning 1737 glass (strain point 667 ° C.) is used as a substrate, the temperature at which the nickel element is gettered by forming a thermal oxide film is 700 ° C., for example, rather than 650 ° C. Can obtain a higher gettering action. However, in this case, if the heating temperature for forming the thermal oxide film is set to 700 ° C., the glass substrate is deformed.

The present embodiment is an example that solves this problem. That is, in the configuration shown in this embodiment, the glass substrate was placed on a platen made of quartz whose flatness was guaranteed, and the heat treatment was performed in this state. In this case, the flatness of the softened glass substrate is also maintained by the flatness of the surface plate. In this case, it is important to perform cooling in a state where the glass substrate is arranged on the surface plate. By employing such a structure, heat treatment can be performed even at a temperature equal to or higher than the strain point of the glass substrate.

<< Example 50 >>
Example 50 is an example in which a crystalline silicon film was obtained on a quartz substrate by using a nickel element. In this embodiment, first, an amorphous silicon film formed on a quartz substrate was transformed into a crystalline silicon film having high crystallinity by the action of nickel element.

Next, a heat treatment was performed in an oxidizing atmosphere to which HCl was added to form a thermal oxide film. At this time, the nickel element remaining in the crystalline silicon film is gettered by the action of chlorine (Cl) in the obtained crystalline silicon film. After the gettering, the thermal oxide film containing the nickel element at a high concentration was removed. In this manner, a crystalline silicon film having high crystallinity and a low nickel element concentration on a quartz substrate was obtained.

FIG. 45 is a diagram showing a manufacturing process of this example. First, a silicon oxynitride film 352 was formed over a quartz glass substrate 351 to a thickness of 5000 angstroms as a base film. It is preferable that the thickness of the base film 352 be about 5000 Å or more in order to have a function of reducing a difference in thermal expansion coefficient between the quartz glass substrate 351 and a silicon film to be formed later.

The silicon oxynitride film 352 was formed by a plasma CVD method using silane, N ₂ O gas, and oxygen as source gases. Alternatively, a plasma CVD method using TEOS gas and N ₂ O gas may be used. It is effective that the base film 352 contain a trace amount of a halogen element represented by chlorine. With this configuration, in a later step, a metal element that promotes crystallization of silicon present in the semiconductor layer can be gettered by the halogen element.

加 え る Also, it is effective to add a hydrogen plasma treatment after the formation of the base film. It is effective to perform plasma treatment in an atmosphere in which oxygen and hydrogen are mixed. This is effective in removing carbon components adsorbed on the surface of the base film and improving interface characteristics with a semiconductor film to be formed later. Next, an amorphous silicon film 353 to be a crystalline silicon film later was formed to a thickness of 1500 angstroms by a low pressure thermal CVD method. The reason why the low pressure thermal CVD method is used is that the film quality of the crystalline silicon film obtained later is excellent, and specifically, the film quality is dense. As a method other than the low pressure thermal CVD method, a plasma CVD method can be used.

The amorphous silicon film manufactured here preferably has an oxygen concentration in the film of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ . This is because oxygen plays an important role in a later metal element (metal element that promotes crystallization of silicon) gettering step. However, care must be taken when the oxygen concentration is higher than the above concentration range, because crystallization of the amorphous silicon film is hindered. The other impurity concentration, for example, the impurity concentration of nitrogen or carbon is preferably as low as possible. Specifically, it is necessary to make them have a concentration of 2 × 10 ¹⁹ cm ⁻³ or less.

膜厚 The thickness of the amorphous silicon film can be selected from the range of about 1000 to 5000 Å. Next, a nickel element was introduced to crystallize the amorphous silicon film 353. Here, the nickel element was introduced by applying a nickel acetate aqueous solution containing 10 ppm (in terms of weight) of nickel to the surface of the amorphous silicon film 353. As a method for introducing the nickel element, in addition to the method using the above solution, a sputtering method, a CVD method, a plasma treatment, or an adsorption method can be used. Among them, the method using the above-mentioned solution is useful because it is simple and the concentration of the metal element can be easily adjusted.

By applying the nickel acetate solution, a water film of the nickel acetate aqueous solution is formed as shown by 354 in FIG. After obtaining this state, excess solution was blown off using a spinner (not shown). Thus, the nickel element is held in contact with the surface of the amorphous silicon film 353.

Considering residual impurities in the subsequent heating step, it is preferable to use, for example, nickel sulfate instead of using a nickel acetate salt solution. This is because the nickel acetate salt solution contains carbon, which may be carbonized in the subsequent heating step and remain in the film. Adjustment of the introduction amount of the nickel element can be performed by adjusting the concentration of the nickel element in the solution.

Next, in the state illustrated in FIG. 45B, heat treatment was performed at a temperature of 750 ° C. to 1100 ° C. to crystallize the amorphous silicon film 353, so that a crystalline silicon film 355 was obtained. Here, heat treatment at 900 ° C. for 4 hours was performed in a nitrogen atmosphere (in a reducing atmosphere) in which hydrogen was mixed at 2% by volume. The reason why the atmosphere is set to the reducing atmosphere in the crystallization step by the heat treatment is to prevent the formation of oxide during the heat treatment step. Specifically, in order to prevent the nickel and oxygen NiO _X reacts from being formed on the surface of the film or within the film.

(4) Oxygen is combined with nickel in a later gettering step, and greatly contributes to nickel gettering. However, it has been found that the binding of oxygen and nickel at this stage of crystallization inhibits crystallization. Therefore, in the step of crystallization by heating, it is important to suppress the formation of oxides as much as possible.

酸 素 The oxygen concentration in the atmosphere in which the heat treatment for crystallization is performed must be in the order of ppm, and preferably 1 ppm or less. As a gas occupying most of the atmosphere in which the heat treatment for the crystallization is performed, an inert gas such as argon or a mixed gas containing nitrogen can be used in addition to nitrogen. After obtaining the crystalline silicon film 355, patterning was performed to form an island-shaped region 356 which would later become an active layer of the thin film transistor.

Next, in the step shown in FIG. 45D, another heat treatment was performed. This heat treatment is performed to form a thermal oxide film for gettering the nickel element. Here, a heat treatment at a temperature of 950 ° C. was performed for 1 hour and 30 minutes in a nitrogen atmosphere containing 5% by volume of oxygen and 3% by volume of HCl with respect to the oxygen. As a result of this step, a thermal oxide film 357 was formed to a thickness of 200 Å.

{Circle around (2)} As described above, this step is for removing the nickel element intentionally introduced in the initial stage for the crystallization of silicon from the crystalline silicon film 356 formed in the island pattern. This heat treatment is performed at a higher temperature than the heat treatment performed for performing the above-described crystallization. This is an important condition for effectively performing nickel element gettering. Note that the heat treatment can be performed at a temperature equal to or lower than the temperature of the heat treatment performed for crystallization, but the effect is small. These points are the same when other metal elements that promote crystallization of silicon are used.

(4) With the formation of the thermal oxide film 357, the thickness of the crystalline silicon film 356 formed in an island pattern is reduced by about 100 angstroms. In this gettering, oxygen existing in the crystalline silicon film plays an important role. That is, gettering of the nickel element proceeds in a form in which the chlorine element acts on the nickel oxide formed by the combination of oxygen and nickel.

As described above, if the concentration of oxygen is too large, it becomes an element that hinders crystallization of the amorphous silicon film 353 in the crystallization step shown in FIG. However, as mentioned above, its presence plays an important role in the nickel gettering process. Therefore, it is important to control the concentration of oxygen existing in the amorphous silicon film serving as the starting film. In addition, in the above process, since the nickel element is gettered in the oxide film to be formed, the nickel concentration in the oxide film is naturally higher than in other regions.

{Circle around (4)} In the vicinity of the interface between the crystalline silicon film 356 and the thermal oxide film 357 near the thermal oxide film 357, the nickel element tended to increase. This is probably because the region where gettering is mainly performed is on the oxide film side near the interface between the crystalline silicon film and the oxide film. It is considered that the reason why gettering proceeds near the interface between the two is due to the presence of stress and crystal defects near the interface.

In this embodiment, an example using chlorine (Cl) as a halogen element is shown, and an example using HCl as an introduction method is shown. However, as the gas other than HCl, one kind selected from HF, HBr, Cl ₂ , F ₂ , and Br ₂ or a mixed gas of plural kinds thereof can be used. In general, a hydride of a halogen can be used. These gases, if the content in the atmosphere (volume content) and HF 0.25 to 5%, 1 to 15% if HBr, 0.25 to 5% if Cl _2, F if ₂ from 0.125 to 2.5%, it is preferable that 0.5 to 10% for Br _2.

(4) If the concentration is lower than the above range, a significant effect cannot be obtained, and if the concentration exceeds the above range, the surface of the silicon film is roughened. Next, a thermal oxide film was formed by heat treatment in an oxidizing atmosphere containing a halogen element as described above, and then the thermal oxide film 357 containing nickel at a high concentration was removed. The removal of the thermal oxide film 357 is performed by wet etching or dry etching using buffered hydrofluoric acid (other hydrofluoric acid-based etchant). In this embodiment, wet etching using buffered hydrofluoric acid is used.

Thus, as shown in FIG. 45E, an island-shaped pattern 356 made of a crystalline silicon film with a reduced nickel concentration was obtained. Here, since the nickel element is contained in the vicinity of the surface of the obtained crystalline silicon film 356 at a relatively high concentration, the etching of the oxide film 357 is further advanced to slightly overlap the surface of the crystalline silicon film 356. Etching is effective.

(4) It is effective to irradiate laser light or strong light after removing the thermal oxide film 357 to further promote the crystallinity of the crystalline silicon film 356. That is, it is effective to perform laser light irradiation or strong light irradiation after the nickel element gettering is performed. As a laser beam to be used, a KrF excimer laser (wavelength 248 nm), a XeCl excimer laser (wavelength 308 nm), or another type of excimer laser can be used. As the strong light, for example, irradiation with ultraviolet light or infrared light can be performed.

{Circle around (4)} After the state shown in FIG. 45E is obtained, it is effective to form a thermal oxide film (not shown) by another heat treatment. This thermal oxide film functions as a part of the gate insulating film or as a gate insulating film when a thin film transistor is formed later. Since the thermal oxide film can improve the interface characteristics with the active layer made of crystalline silicon, the thermal oxide film is optimal as a material constituting the gate insulating film.

<< Example 51 >>
Example 51 is an example in which Cu is used as the metal element that promotes crystallization of silicon in the configuration shown in Example 50. In this case, cupric acetate [Cu (CH ₃ COO) ₂ ], cupric chloride (CuCl ₂ 2H ₂ O) or the like may be used as a solution for introducing Cu. In this example, cupric acetate [Cu (CH ₃ COO) ₂ ] was used, and the other steps were the same as in Example 50 to obtain the state shown in FIG.

<< Example 52 >>
The fifty-second embodiment is an example in which crystal growth of a different form from the fifty-first embodiment is performed. The present embodiment relates to a method of performing crystal growth in a direction parallel to a substrate called lateral growth using a metal element that promotes crystallization of silicon.

FIG. 46 shows a manufacturing process of this embodiment. First, a silicon oxynitride film having a thickness of 3000 Å was formed as a base film 359 over a quartz substrate 358. Next, an amorphous silicon film 360 serving as a starting film of the crystalline silicon film was formed to a thickness of 2000 angstroms by a low pressure thermal CVD method. Note that a plasma CVD method may be used instead of the reduced pressure thermal CVD method.

Next, a silicon oxide film (not shown) was formed to a thickness of 1500 angstroms and patterned to form a mask denoted by reference numeral 361. An opening is formed in a region indicated by reference numeral 362 in the mask. In a region where the opening 362 is formed, the amorphous silicon film 360 is exposed. The opening 362 has a rectangular shape elongated in the longitudinal direction from the depth of the drawing to the front side. The width of the opening 362 is suitably 20 μm or more, and the length in the longitudinal direction may be formed to a required length. Here, the width was 20 μm and the length was 1 cm.

Next, an aqueous solution of nickel acetate containing 10 ppm by weight of nickel element was applied to the mask 361 and the opening 362, and spin-drying was performed using a spinner (not shown) to remove excess solution. Thus, a state is realized in which the nickel element is held in contact with the exposed surface of the amorphous silicon film 360, as shown by the dotted line 363 in FIG.

Next, a heat treatment was performed at 800 ° C. for 4 hours in a nitrogen atmosphere containing 2% by volume of hydrogen and containing as little oxygen as possible. Then, as indicated by 364 in FIG. 46B, crystal growth proceeded in a direction parallel to the substrate 358. This crystal growth proceeds from the region of the opening 362 into which the nickel element is introduced toward the periphery. Such crystal growth in a direction parallel to the substrate is referred to as lateral growth or lateral growth in this specification.

横 Under the conditions shown in this embodiment, the lateral growth can be performed over 100 μm. Thus, a silicon film having a region grown laterally was obtained. In the region where the opening 362 is formed, crystal growth in the vertical direction called vertical growth progresses from the surface of the silicon film toward the interface of the base.

Next, after the mask 361 is removed, patterning is further performed, and as shown in FIG. 46C, an island made of a crystalline silicon film crystal-grown in a direction parallel to the substrate (that is, laterally grown). A pattern 366 was formed. Thereafter, a heat treatment was performed at a temperature of 950 ° C. for 1 hour and 30 minutes in a nitrogen atmosphere containing 10% by volume of oxygen and 3% by volume of HCl with respect to oxygen.

As a result, a thermal oxide film indicated by reference numeral 367 was formed to a thickness of 200 angstroms. FIG. 46D shows this state. In this step, an oxide film 367 containing a nickel element at a high concentration in the film (that is, the nickel element is gettered) is formed, whereby the concentration of the nickel element in the silicon film 367 is relatively reduced. .

Therefore, the thermal oxide film 367 contains a high concentration of nickel element gettered in accordance with the film formation. Further, by forming thermal oxide film 367, crystalline silicon film 366 has a thickness of about 500 Å. Next, the thermal oxide film 367 containing the nickel element at a high concentration was removed. Thus, the state shown in FIG.

In this state, the active layer (crystalline silicon film formed in an island shape) 366 has a concentration distribution in which the concentration of nickel increases toward the surface of the crystalline silicon film. This state is due to the fact that the nickel element is gettered in the thermal oxide film 367 when the thermal oxide film 367 is formed. Therefore, it is useful to further etch the surface of the crystalline silicon film after removing the thermal oxide film 367 to remove the region where the nickel element concentration is high.

The concentration of the nickel element remaining in the pattern 366 consisting of the lateral growth region obtained in this manner can be further reduced as compared with the case shown in the embodiment 50. This is also due to the fact that the concentration of the metal element contained in the lateral growth region is originally low. Thus, the concentration of the nickel element in the pattern 366 composed of the lateral growth region can be easily set to the order of 10 ¹⁷ cm ⁻³ or less.

In the case where a thin film transistor is formed using the lateral growth region as in the present embodiment, the vertical growth region as shown in the embodiment 50 (in the case of the embodiment 50, the entire surface grows vertically) is used. A semiconductor device having higher mobility can be obtained as compared with the case where the semiconductor device is used. After obtaining the state shown in FIG. 46E, a thermal oxide film (not shown) was further formed on the surface of the active layer 366. The thermal oxide film was formed in a thickness of 500 Å by performing a heat treatment in an oxygen atmosphere at 950 ° C. for 30 minutes.

Of course, the thickness of the thermal oxide film can be set to a desired or predetermined value by controlling the heating time, the heating temperature, and the oxygen concentration in the atmosphere. Thereafter, for example, in the case of manufacturing a thin film transistor, a silicon oxide film can be formed by plasma CVD or the like to cover the thermal oxide film, and a gate insulating film can be formed together with the thermal oxide film. . Alternatively, the thermal oxide film may have a desired and predetermined thickness, and may be used as it is as the gate insulating film.

<< Example 53 >>
Example 53 is an example in which a thin film transistor arranged in a pixel region of an active matrix type liquid crystal display device or an active matrix type EL display device is manufactured using the crystalline silicon film according to the present invention. FIG. 47 is a diagram showing a manufacturing process in this example.

First, an island-shaped semiconductor layer (a layer made of a crystalline silicon film) patterned into the shape of an active layer was formed on a glass substrate by the steps shown in Example 50 and Example 52. The following steps are the same for both. In the state shown in FIG. 47A, 369 is a glass substrate, 370 is a base film, and 371 is an active layer formed of a crystalline silicon film.

(4) Before forming the thermal oxide film 368, plasma treatment was performed in a reduced-pressure atmosphere in which oxygen and hydrogen were mixed. This plasma was generated by high frequency discharge. By this plasma treatment, organic substances existing on the exposed surface of the active layer 371 were removed. To be precise, the organic substances adsorbed on the surface of the active layer are oxidized by the oxygen plasma, and the oxidized organic substances are reduced and vaporized by the hydrogen plasma.

有機 Thus, the organic substances present on the exposed surface of the active layer 371 are removed. This removal of organic substances is very effective in suppressing the presence of fixed charges on the surface of the active layer 371. The fixed charge caused by the presence of the organic substance hinders the operation of the device and causes instability of the characteristics, and it is very useful to reduce the presence thereof. Next, a 200 Å thermal oxide film 368 was formed on the surface by thermal oxidation to obtain the state shown in FIG.

After that, a silicon oxynitride film 372 constituting a gate insulating film was formed to a thickness of 1000 angstroms. As a film forming method, a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O, a plasma CVD method using a mixed gas of TEOS and N ₂ O, and the like can be used. Here, TEOS and N ₂ O are used. A mixed gas with ₂ O was used. The silicon oxynitride film 372 functions as a gate insulating film together with the thermal oxide film 368.

When a metal element enters (penetrates) into the gate insulating film, its function as an insulating film is reduced, which causes instability and variations in the characteristics of the thin film transistor. It is effective to include a halogen element in the glass. That is, by fixing the nickel element by the action of the halogen element, it is possible to prevent the function of the gate insulating film as an insulating film from being deteriorated due to the effect of the nickel element present in the active layer. The use of a silicon oxynitride film has a significance that a metal element is less likely to enter the gate insulating film due to its dense film quality. Note that a commonly used silicon oxide film can be used as the gate insulating film.

After the silicon oxynitride film 372 functioning as a gate insulating film was formed, an aluminum film (not shown) functioning as a gate electrode later was formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium. Scandium is contained in the aluminum film in order to suppress generation of hillocks and whiskers in a later step. Here, the hillocks and whiskers mean that heating causes abnormal growth of aluminum, thereby forming needle-like or barbed protrusions.

(4) After forming the aluminum film, a dense anodic oxide film (not shown) was formed. This anodized film was formed by using an ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation is performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film. The thickness of the anodic oxide film having a dense film quality (not shown) was about 100 angstroms. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation.

Next, a resist mask 374 was formed, and the aluminum film was patterned into a pattern indicated by 373. Thus, the state shown in FIG. 47B is obtained. Next, anodic oxidation was performed again. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 373 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 376 is formed.

In this step, the anodic oxide film 376 is selectively formed on the side surface of the aluminum pattern due to the presence of the highly adhesive resist mask 374 on the upper part. This anodic oxide film can be grown to a thickness of several μm. Here, the thickness was set to 6000 Å. The growth distance can be controlled by the time of anodic oxidation.

(4) After removing the resist mask 306, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, an anodic oxide film having a dense film quality is formed as indicated by reference numeral 377 because the electrolytic solution enters the porous anodic oxide film 376.

膜厚 The thickness of this dense anodic oxide film 377 was 1000 angstroms. This film thickness was controlled by the applied voltage. Here, the exposed silicon oxynitride film 372 and thermal oxide film 368 were etched. This etching used dry etching. Next, the porous anodic oxide film 376 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 47D is obtained.

(4) Thereafter, impurity ions were implanted. Here, P (phosphorus) ions were implanted by a plasma doping method in order to manufacture an N-channel thin film transistor. In this step, regions 379 and 383 to be heavily doped and regions 380 and 382 to be lightly doped are formed. This is because part of the remaining silicon oxide film 378 functions as a semi-transparent mask, and part of the implanted ions is shielded there.

Next, the region into which the impurity ions were implanted was activated by irradiating ultraviolet rays. Infrared light or laser light can be used instead of ultraviolet light. Thus, a source region 379, a channel formation region 381, a drain region 383, and low-concentration impurity regions 380 and 382 were formed in a self-aligned manner. Here, what is indicated by reference numeral 382 is a region called an LDD (lightly doped drain) region.

In the case where the thickness of the dense anodic oxide film 377 is increased to 2000 Å or more, an offset gate region can be formed outside the channel formation region 381 with the thickness. Although the offset gate region is also formed in the present embodiment, its size is small, so its contribution due to its existence is small, and the drawing is complicated, so it is not shown in the drawing.

(4) Next, as the interlayer insulating film 384, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed. Here, a silicon oxide film is formed. As the interlayer insulating film, a layer made of a resin material may be formed over a silicon oxide film or a silicon nitride film. Then, a contact hole was formed, and a source electrode 385 and a drain electrode 386 were formed. Thus, the thin film transistor shown in FIG. 47E was completed.

<< Example 54 >>
Embodiment 54 is an example in which a thin film transistor is manufactured by a process different from that shown in Embodiment 53 (FIG. 47). FIG. 48 shows the manufacturing process of this embodiment. First, a crystalline silicon film was formed on a glass substrate by the steps described in Example 50 or Example 52, respectively. Next, they were patterned, and plasma treatment was performed in a mixed reduced pressure atmosphere of oxygen and hydrogen. The following steps are the same for both.

Next, a thermal oxide film 387 was formed to a thickness of 200 angstroms to obtain a state shown in FIG. The thermal oxide film 387 was formed by performing a heat treatment in an oxygen atmosphere at a temperature of 950 ° C. for 30 minutes. In the state shown in FIG. 48A, a portion indicated by reference numeral 388 is a glass substrate, 389 is an underlayer, and 390 is an active layer formed of a crystalline silicon film. The thermal oxide film 387 is a thermal oxide film formed again after removing the thermal oxide film for gettering.

After the state shown in FIG. 48A is obtained, a silicon oxynitride film 391 which forms a gate insulating film is formed to a thickness of 1000 angstroms. This film formation was performed by a plasma CVD method using a mixed gas of oxygen, silane, and N ₂ O. Instead, a plasma CVD method using a mixed gas of TEOS and N ₂ O can be used. The silicon oxynitride film 391 forms a gate insulating film together with the thermal oxide film 387. Note that a silicon oxide film can be used instead of the silicon oxynitride film.

Next, an aluminum film (not shown) functioning as a gate electrode later was formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium. Thereafter, a dense anodic oxide film (not shown) was formed. The anodic oxide film was formed using an ethylene glycol solution containing tartaric acid at 3% by weight as an electrolytic solution. That is, in this electrolytic solution, anodic oxidation was performed using the aluminum film as an anode and platinum as a cathode to form an anodic oxide film having a dense film quality on the surface of the aluminum film.

膜厚 The thickness of the anodic oxide film having a dense film quality (not shown) was about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation. Next, a resist mask 392 was formed, and the aluminum film was patterned into a pattern indicated by reference numeral 393.

(5) Next, anodic oxidation was performed again. Here, a 3 wt% oxalic acid aqueous solution was used as an electrolytic solution. By performing anodic oxidation using the aluminum pattern 393 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 394 is formed. In this step, an anodic oxide film 394 is selectively formed on the side surface of the aluminum pattern 393 due to the presence of the resist mask 392 having high adhesion on the upper portion.

The anodic oxide film can be grown to a thickness of several μm. Here, the film thickness was 6000 Å. The growth distance can be controlled by the anodic oxidation time. Next, after removing the resist mask 392, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, an anodic oxide film having dense film quality was formed as indicated by reference numeral 395 because the electrolytic solution entered the porous anodic oxide film 394.

Next, the first impurity ion implantation was performed. By the implantation of the impurity ions, a source region 396 and a drain region 398 are formed. Note that no impurity ions are implanted into the region denoted by reference numeral 397. Next, the porous anodic oxide film 394 was removed using a mixed acid solution in which acetic acid, nitric acid, and phosphoric acid were mixed. Thus, the state shown in FIG. 48D is obtained. After that, impurity ions were implanted again. The impurity ions were implanted under light doping conditions rather than the first impurity ion implantation conditions.

ラ イ ト Light-doped regions indicated by reference numerals 399 and 400 were formed by the above steps. Then, an area indicated by reference numeral 401 is a channel formation area. Next, by irradiating laser light or strong light, the region into which the impurity ions are implanted is activated. Here, laser light irradiation is performed. Thus, the source region 396, the channel formation region 401, the drain region 398, and the low-concentration impurity regions 399 and 400 were formed in a self-aligned manner. Here, what is indicated by reference numeral 400 is a region called an LDD (lightly doped drain) region.

Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 402. Here, a silicon nitride film is formed. As the interlayer insulating film, a layer made of a resin material may be formed over a silicon oxide film or a silicon nitride film. Next, a contact hole was formed, and a source electrode 403 and a drain electrode 404 were formed. Thus, the thin film transistor shown in FIG. 48E was completed.

<< Example 55 >>
The 55th embodiment is an example in which an N-channel thin film transistor and a P-channel thin film transistor are configured to be complementary. The configuration shown in this embodiment can be used, for example, for various thin film integrated circuits integrated on an insulating surface. Further, for example, it can be used for a peripheral drive circuit of an active matrix type liquid crystal display device. FIG. 49 is a diagram showing the manufacturing process of this example.

First, as shown in FIG. 49A, a silicon oxide film or a silicon oxynitride film is formed as a base film 407 over a glass substrate 406. Although a silicon oxynitride film is preferably used, a silicon oxynitride film is formed here. Next, an amorphous silicon film (not shown) was formed by a plasma CVD method. Instead, a reduced pressure thermal CVD method may be used. Further, this amorphous silicon film was transformed into a crystalline silicon film by the method shown in Example 50.

Next, after performing a plasma treatment in a mixed atmosphere of oxygen and hydrogen, the obtained crystalline silicon film was patterned to form active layers 408 and 409. Thus, the state shown in FIG. 49A is obtained. Note that here, in order to suppress the influence of carriers moving on the side surface of the active layer, in a state shown in FIG. 49A, a temperature of 650 ° C. for 10 hours in a nitrogen atmosphere containing 3% by volume of HCl. Heat treatment was performed.

If a trap level due to the presence of a metal element exists on the side surfaces of the active layers 408 and 409, the OFF current characteristics are deteriorated. Therefore, the above-described processing is performed to reduce the level density on the side surfaces of the active layers. Putting is useful. Next, a thermal oxide film 405 and a silicon oxynitride film 410 forming a gate insulating film were formed. Here, when quartz is used as the substrate, it is desirable to form the gate insulating film only with the thermal oxide film formed by the above-described thermal oxidation method.

Next, an aluminum film (not shown) for forming a gate electrode was formed to a thickness of 4000 angstroms later. As the metal other than the aluminum film, an anodizable metal (for example, tantalum) can be used. After forming the aluminum film, an extremely thin and dense anodic oxide film was formed on the surface by the above-described method. Next, a resist mask (not shown) was arranged on the aluminum film, and the aluminum film was patterned. Then, anodic oxidation was performed using the obtained aluminum pattern as an anode to form porous anodic oxide films 413 and 414. The thickness of the porous anodic oxide film was 5000 Å.

(5) Further, anodic oxidation was performed again under the condition of forming a dense anodic oxide film, thereby forming dense anodic oxide films 415 and 416. Here, the dense anodic oxide films 415 and 416 have a thickness of 800 Å. Thus, the state shown in FIG. 49B is obtained. Further, the exposed silicon oxide film 410 and thermal oxide film 405 were removed by dry etching to obtain a state shown in FIG. Thereafter, the porous anodic oxide films 413 and 414 were removed using a mixed acid obtained by mixing acetic acid, nitric acid and phosphoric acid. Thus, the state shown in FIG. 49D is obtained.

Here, resist masks were alternately arranged so that P (phosphorus) ions were implanted into the left thin film transistor and B (boron) ions were implanted into the right thin film transistor. By implanting the impurity ions (P ions), a source region 419 and a drain region 422 having a high concentration of N-type were formed in a self-aligned manner. In addition, a weakly N-type region 420 doped with P ions at a low concentration was formed at the same time, and a channel formation region 421 was formed at the same time.

The reason why the region having the weak N-type indicated by the symbol 420 is formed is that the remaining gate insulating film 417 exists. That is, P ions transmitted through the gate insulating film 417 are partially shielded by the gate insulating film 417. Further, the source region 426 and the drain region 423 having a strong P type are formed in a self-alignment manner by the same principle and method. Further, the low concentration impurity region 425 is formed at the same time, and the channel formation region 424 is formed at the same time.

If the dense anodic oxide films 415 and 416 are as thick as 2000 angstroms, the offset gate region can be formed in contact with the channel forming region with the thickness. In the case of the present embodiment, the dense anodic oxide films 415 and 416 have a thin film thickness of 1000 angstroms or less, and their existence can be ignored. Next, laser light irradiation was performed to anneal the region into which the impurity ions had been implanted. Note that strong light can be used instead of laser light.

Next, as shown in FIG. 49E, a silicon nitride film 427 and a silicon oxide film 428 were formed as interlayer insulating films. The thickness of each film was 1000 Å. Note that the silicon oxide film 428 need not be formed. Thus, the thin film transistor is covered with the silicon nitride film. Since the silicon nitride film is dense and has good interface characteristics, such a structure can increase the reliability of the thin film transistor.

(4) Further, an interlayer insulating film 429 made of a resin material was formed by using a spin coating method. Here, the thickness of the interlayer insulating film 429 is 1 μm. Then, a contact hole was formed, and a source electrode 430 and a drain electrode 431 of the left N-channel thin film transistor were formed, and at the same time, a source electrode 432 and a drain electrode 431 of the right thin film transistor were formed. Here, the drain electrodes 431 are commonly arranged. Thus, a thin film transistor in which the N-channel thin film transistor and the P-channel thin film transistor shown in FIG. 49F are formed in a complementary manner is completed.

As described above, a thin film transistor circuit having a complementary CMOS structure can be formed. In the structure shown in this embodiment, a structure in which the thin film transistor is covered with a silicon nitride film and further covered with a resin material is obtained. With this configuration, it is possible to provide a highly durable one in which mobile ions and moisture hardly enter. In addition, when a multilayer wiring is formed, it is possible to prevent a capacitance from being formed between the thin film transistor and the wiring.

<< Example 56 >>
The embodiment 56 is an example in which the nickel element is directly introduced into the surface of the base film in the process shown in the embodiment 50. In this case, the nickel element is held in contact with the lower surface of the amorphous silicon film. In this case, a nickel element is introduced after the formation of the base film, and first, the nickel element (the metal element) is brought into contact with and held on the surface of the base film.

In this embodiment, the nickel element is directly introduced by applying an aqueous solution of nickel acetate on the surface of the underlayer, and the other steps are the same as in Embodiment 50, as shown in FIG. Then, an island-shaped pattern 356 made of a crystalline silicon film having a reduced nickel concentration was obtained. As a method for introducing the nickel element, a sputtering method, a CVD method, an adsorption method, or the like can be used in addition to a method using a solution.

<< Example 57 >>
In the present embodiment 57, laser light irradiation is performed in the state of FIG. 45 (E), the state of FIG. 46 (E), the state of FIG. 47 (A) and the state of FIG. This is an example in which the crystallinity of the island-shaped pattern made of the obtained crystalline silicon film is improved by performing the above. In the present embodiment, laser light irradiation was performed in each state to improve the crystallinity of the island-shaped pattern made of the crystalline silicon film.

In the states shown in FIG. 45 (E), FIG. 46 (E), FIG. 47 (A), and FIG. 48 (A), when the laser light is irradiated, the entire film before patterning is annealed. , A predetermined annealing effect can be obtained with a relatively low irradiation energy density. This is considered to be because the energy of the laser used for annealing is increased because the laser energy is applied to a small area.

<< Example 58 >>
Example 58 is an example in which a crystalline silicon film was obtained on a glass substrate by using a nickel element. In this embodiment, first, a crystalline silicon film having high crystallinity was obtained by the action of the nickel element. Then, laser light irradiation was performed. By irradiating the laser light, the crystallinity of the film is increased, and the nickel element which is locally concentrated is diffused into the film. That is, the mass of nickel was reduced or eliminated.

Next, an oxide film containing F (fluorine) was formed on the crystalline silicon film by a thermal oxidation method. At this time, the nickel element remaining in the obtained crystalline silicon film is gettered in the thermal oxide film by the action of the F element. In this case, the gettering proceeds effectively because the nickel element is dispersed and present by the previous laser light irradiation. Further, gettering was performed as described above to remove the thermal oxide film containing the nickel element at a high concentration. Thus, a crystalline silicon film having high crystallinity and a low nickel element concentration on a glass substrate was obtained.

FIG. 50 is a diagram showing the manufacturing process of this example. First, a 3000-Å-thick silicon oxide film 434 was formed as a base film on a Corning 1737 glass substrate (strain point 667 ° C.) 433. This film was formed by a sputtering method. The silicon oxide film 434 has a function of preventing diffusion of impurities from a glass substrate in a later step. Further, it has a function of alleviating a stress acting between a glass substrate and a silicon film to be formed later.

(4) It is effective to include a trace amount of a halogen element in the base film 434. By doing so, in a later step, a metal element that promotes crystallization of silicon present in the semiconductor layer can be gettered in the base film by the halogen element. It is effective to perform a hydrogen plasma treatment after the formation of the base film. This is because there is an effect of removing carbides existing on the surface of the base film and suppressing the presence of fixed charge levels at the interface with the silicon film to be formed later. As an alternative to the hydrogen plasma treatment, it is also effective to perform the plasma treatment in an atmosphere in which oxygen and hydrogen are mixed.

Next, an amorphous silicon film 435 to be a crystalline silicon film later was formed to a thickness of 500 angstroms by a low pressure thermal CVD method. The reason why the low pressure thermal CVD method is used is that the film quality of the crystalline silicon film obtained later is superior, and specifically, the film quality is dense. As a method other than the low pressure thermal CVD method, a plasma CVD method can be used. The amorphous silicon film manufactured here preferably has an oxygen concentration in the film of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ .

This is because oxygen plays an important role in a later step of gettering a metal element (a metal element that promotes crystallization of silicon) (in this embodiment, a nickel gettering step). However, care must be taken when the oxygen concentration is higher than the above concentration range, because crystallization of the amorphous silicon film is hindered. Further, when the oxygen concentration is lower than the above concentration range, the contribution of the metal element to the gettering action becomes small. The other impurity concentration, for example, the impurity concentration of nitrogen or carbon is preferably as low as possible. Specifically, it is preferable to set the concentration to 2 × 10 ¹⁹ cm ⁻³ or less.

上限 The upper limit of the thickness of the amorphous silicon film is about 2000 Å. This is because it is disadvantageous that the film is too thick in order to obtain the effect of the subsequent laser light irradiation. The disadvantage of the thick film is that most of the laser light applied to the silicon film is absorbed on the surface of the film. Note that the lower limit of the film thickness of the amorphous silicon film 435 depends on the film formation method, but is practically about 200 Å. If the film thickness is less than that, there is a problem in the uniformity of the film thickness.

(4) Next, a metal element for crystallizing the amorphous silicon film 435 was introduced. Here, a nickel element was used as a metal element that promotes crystallization of silicon, and a method using a solution was used as a method for introducing the nickel element. Here, the nickel element was introduced by applying a nickel acetate aqueous solution containing 10 ppm (by weight) of nickel to the surface of the amorphous silicon film 435. As a method for introducing the nickel element, in addition to the method using the above solution, a sputtering method, a CVD method, a plasma treatment, or an adsorption method can be used. Among them, the method using a solution is useful because it is simple and the concentration of the metal element is easily adjusted.

(5) By applying the nickel acetate aqueous solution, a water film of the nickel acetate aqueous solution indicated by 436 in FIG. 50A was formed. After obtaining this state, excess solution was blown off using a spinner (not shown). In this manner, the nickel element is held in contact with the surface of the amorphous silicon film 435. The amount of the nickel element introduced into the amorphous silicon film 435 can also be adjusted by the holding time of the water film 436 and the removal conditions using a spinner.

Considering residual impurities in the subsequent heating step, it is preferable to use, for example, nickel sulfate or the like instead of using the nickel acetate aqueous solution. This is because the nickel acetate salt solution contains carbon, which is carbonized in a subsequent heating step, and there is a concern that a carbon component remains in the film or on the surface of the film.

Next, in the state shown in FIG. 50B, heat treatment was performed to crystallize the amorphous silicon film 435 and obtain a crystalline silicon film 437. Here, the heat treatment was performed in a nitrogen atmosphere at 640 ° C. containing 3% by volume of hydrogen, and the heating time was 4 hours. The heat treatment can be performed at a temperature in the range of 500 to 700 ° C., but is preferably performed at a temperature equal to or lower than the strain point of the glass substrate. Since the strain point of the Corning 1737 glass substrate used in this embodiment is 667 ° C., the upper limit is preferably set to about 650 ° C. in view of the margin.

The reason why the atmosphere is a reducing atmosphere in the crystallization step by the above heat treatment is to prevent oxides from being formed during the heat treatment step. More specifically, the reaction with nickel and oxygen, because the NiO _X is prevented from undesirably formed on the surface of the film or within the film. Oxygen combines with nickel in a later gettering step and makes a significant contribution to nickel gettering. However, it has been found that the binding of oxygen and nickel at this stage of crystallization inhibits crystallization. Therefore, in the step of crystallization by heating, it is important to suppress the formation of oxides as much as possible.

The oxygen concentration in the atmosphere in which the heat treatment for crystallization is performed must be on the order of ppm, preferably 1 ppm or less. As a gas occupying most of the atmosphere in which the heat treatment for crystallization is performed, an inert gas such as argon or a mixed gas thereof other than nitrogen can be used. After the crystallization step by the above-mentioned heat treatment, the nickel element remains as a certain mass. This was confirmed by observation with a TEM (transmission electron microscope). The cause of the fact that this nickel is present in a certain mass is not clear, but is thought to be related to some mechanism of crystallization.

{Next, laser light irradiation was performed as shown in FIG. 50C). Here, a method was employed in which a KrF excimer laser (wavelength: 248 nm) was used and a laser beam having a linear beam shape was irradiated while scanning. By irradiating the laser light, the nickel element locally concentrated is dispersed to some extent in the film 437 as a result of crystallization by the above-described heat treatment. That is, the mass of the nickel element can be eliminated or reduced, and the nickel element can be dispersed. As the laser light, a XeCl excimer laser (wavelength 308 nm) or another type of excimer laser can be used. Further, a configuration may be employed in which irradiation with, for example, ultraviolet light or infrared light is performed instead of laser light.

Next, heat treatment was performed again in the step illustrated in FIG. This heat treatment is a treatment for forming a thermal oxide film for gettering the nickel element. Here, the atmosphere is an oxygen atmosphere containing ₃ % by volume of hydrogen and 100 ppm (by volume) of ClF _3. At 640 ° C. In this step, a thermal oxide film was formed to a thickness of 200 angstroms.

This step is for removing the nickel element intentionally mixed in the initial stage for crystallization from the crystalline silicon film 437. This heat treatment is performed in a temperature range of about 500 to 700 ° C. when the substrate is an ordinary glass substrate. The upper limit of the heat treatment temperature is limited by the strain point of the glass substrate to be used. If the heat treatment is performed at a temperature equal to or higher than the strain point of the glass substrate to be used, the substrate is deformed.

In this step, the nickel element dispersed by the laser light irradiation is gettered in the oxide film 438 to be formed. Therefore, the nickel concentration in oxide film 438 is naturally higher than in other regions. In addition, it was observed that the nickel element tended to increase in the vicinity of the interface between the crystalline silicon film 437 and the thermal oxide film 438. This is probably because the region where gettering is mainly performed is on the oxide film side near the interface between the silicon film and the oxide film.

It is considered that gettering progresses near the interface due to the presence of stress and defects near the interface. Further, it was observed that the concentrations of fluorine and chlorine tended to increase near the interface between the silicon film 437 and the thermal oxide film 438. The crystalline silicon film thus obtained contains a metal element that promotes the crystallization of silicon at a concentration of 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁸ cm ⁻³ and a fluorine atom of 1 × 10 8 cm ^−3. It is contained at a concentration of ¹⁵ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ , and hydrogen atoms are contained at a concentration of 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ²¹ cm ⁻³ .

(5) After the formation of the thermal oxide film 438 shown in FIG. 50D was completed, the oxide film 438 containing nickel at a high concentration was removed. The removal of the oxide film 438 can be performed by wet etching or dry etching using buffered hydrofluoric acid (other hydrofluoric acid-based etchant). Here, wet etching using buffered hydrofluoric acid is performed. Thus, as shown in FIG. 50E, a crystalline silicon film 439 with a reduced nickel concentration was obtained.

Since the nickel element is contained at a relatively high concentration in the vicinity of the surface of the obtained crystalline silicon film 439, the etching of the oxide film 438 is further advanced to slightly overetch the surface of the crystalline silicon film 439. That is valid. Further, it is effective to irradiate laser light again after removing the thermal oxide film 438 to further promote the crystallinity of the obtained crystalline silicon film 439.

<< Example 59 >>
Example 59 is an example in which Cu is used as the metal element for promoting crystallization of silicon in the structure shown in Example 58. In this case, as a solution for introducing Cu, cupric acetate [Cu (CH ₃ COO) ₂ ], cupric chloride (CuCl ₂ 2H ₂ O), or the like is used. Here, cupric chloride (CuCl ₂ 2H ₂ O) is used. An aqueous solution of CuCl ₂ 2H ₂ O) was used. Other steps were the same as those of the example 58, and the state of FIG. 50E was obtained.

<< Example 60 >>
Embodiment 60 is an example in which the crystal growth of a form different from that of Embodiment 58 is performed. The present embodiment relates to a method of performing crystal growth in a direction parallel to a substrate called lateral growth using a metal element that promotes crystallization of silicon. FIG. 51 shows a manufacturing process of this embodiment.

First, a silicon oxide film having a thickness of 3000 Å was formed as a base film 441 on a Corning 1737 glass substrate 440. Next, an amorphous silicon film 442 serving as a starting film of the crystalline silicon film was formed to a thickness of 600 angstroms by a low pressure thermal CVD method. It is preferable that the thickness of the amorphous silicon film be 2000 Å or less as described above. As the substrate, another substrate such as a quartz substrate may be used.

Next, a silicon oxide film (not shown) was formed to a thickness of 1500 angstroms and patterned to form a mask 443. This mask has an opening formed in a region indicated by reference numeral 444. In the region where the opening 444 is formed, the amorphous silicon film 442 is exposed. The opening 444 has an elongated rectangular shape extending in the longitudinal direction from the depth of the drawing to the front. The width of the opening 444 is suitably 20 μm or more, and the length in the longitudinal direction may be formed to a required length. In this embodiment, the width is 50 μm and the length is 8 cm.

Then, as in Example 58, after applying an aqueous nickel acetate solution containing 10 ppm by weight of nickel element, spin drying was performed using a spinner to remove excess solution. Thus, a state in which the nickel element is held in contact with the exposed surface of the amorphous silicon film 442 as shown by the dotted line 445 in FIG.

Next, a heat treatment was performed at 640 ° C. for 4 hours in a nitrogen atmosphere containing 3% by volume of hydrogen and containing as little oxygen as possible. Then, crystal growth proceeded in a direction parallel to the substrate 440 as indicated by 446 in FIG. 51B. This crystal growth proceeds from the region of the opening 444 into which the nickel element has been introduced toward the periphery. Such crystal growth in a direction parallel to the substrate is referred to as lateral growth or lateral growth in this specification.

横 Under the conditions shown in this embodiment, the lateral growth can be performed over 100 μm. Thus, a silicon film 447 having a laterally grown region was obtained. In the region where the opening 444 is formed, crystal growth in the vertical direction called vertical growth proceeds from the surface of the silicon film toward the interface of the base. Next, the mask 443 made of a silicon oxide film for selectively introducing a nickel element was removed. Thus, the state shown in FIG. 51C is obtained. In this state, in the crystalline silicon film 447, there are a vertical growth region, a horizontal growth region, and a region that has not been subjected to crystal growth (amorphous state).

ニ ッ ケ ル In this state, the nickel element is unevenly distributed in the film. In particular, the nickel element is present at a relatively high concentration in the region where the opening 444 is formed and in the tip portion of the crystal growth indicated by reference numeral 446. Next, laser light irradiation was performed. Here, a KrF excimer laser was used as in Example 58. By this step, the unevenly distributed nickel element is diffused, and a state in which gettering is easily performed in a later gettering step is obtained.

After the laser beam irradiation was completed, heat treatment was performed at a temperature of 650 ° C. in an atmosphere containing ₃ % by volume of hydrogen and 100 ppm (by volume) of NF ₃ . In this step, an oxide film 448 containing a high concentration of nickel in the film was formed to a thickness of 200 angstroms, and at the same time, the concentration of nickel in the silicon film 447 was relatively reduced. After the formation of the thermal oxide film by the heat treatment was completed, the thermal oxide film 448 containing a high concentration of nickel element was removed.

(4) After removing the thermal oxide film 448, it is effective to further etch the surface of the crystalline silicon film. Next, a pattern 449 consisting of a lateral growth region was formed by patterning. The concentration of the nickel element remaining in the pattern 449 composed of the lateral growth region obtained in this manner can be further reduced as compared with the case shown in Embodiment 58.

This is also due to the fact that the concentration of the metal element contained in the lateral growth region is originally low. Specifically, the concentration of the nickel element in the pattern 448 including the lateral growth region can be easily set to the order of 10 ¹⁷ cm ⁻³ or less. After the pattern shown in FIG. 51E is formed, it is useful to further perform an etching treatment to remove a nickel element present on the pattern surface.

Next, a thermal oxide film 450 was formed on the formed pattern 449. This thermal oxide film was formed to a thickness of 200 Å by performing a heat treatment in an oxygen atmosphere at a temperature of 650 ° C. for 12 hours. When forming the thermal oxide film 450, it is effective to include fluorine in the atmosphere. If fluorine is contained in the atmosphere during the formation of the thermal oxide film 450, the action of fluorine can fix the nickel element and neutralize dangling bonds on the surface of the silicon film. That is, the interface characteristics between the active layer and the gate insulating film can be improved.

塩 素 Alternatively, chlorine may be used instead of fluorine. This thermal oxide film will later become a part of the gate insulating film in the case of forming a thin film transistor. After that, when a thin film transistor is manufactured, a silicon oxide film is formed by a plasma CVD method or the like so as to cover the thermal oxide film 450, and a gate insulating film is formed.

<< Example 61 >>
Example 61 is an example in which a thin film transistor arranged in a pixel region of an active matrix type liquid crystal display device or an active matrix type EL display device is manufactured using the crystalline silicon film obtained by the present invention. .

FIG. 52 shows a manufacturing process of this embodiment. First, a crystalline silicon film was formed on a glass substrate by the steps shown in Example 58 and Example 60. The following steps are the same for both. When a crystalline silicon film is obtained with the structure shown in Example 58, the crystalline silicon film is patterned and subjected to the steps shown in FIGS. 50 (A) to 50 (E) and then to the state shown in FIG. 52 (A). Got.

In the state shown in FIG. 52A, 452 is a glass substrate, 453 is a base film, and 454 is an active layer formed of a crystalline silicon film. After the state shown in FIG. 52A was obtained, plasma treatment was performed in a reduced-pressure atmosphere in which oxygen and hydrogen were mixed. This plasma was generated by high frequency discharge. By this plasma treatment, organic substances existing on the exposed surface of the active layer 454 were removed. To be precise, the organic substances adsorbed on the surface of the active layer are oxidized by the oxygen plasma, and the oxidized organic substances are reduced and vaporized by the hydrogen plasma. Thus, the organic substances present on the exposed surface of the active layer 454 were removed.

The removal of the organic substance is very effective in reducing the presence of fixed charges on the surface of the active layer 454. The fixed charge caused by the presence of the organic substance hinders the operation of the device and causes instability of the characteristics, and it is very useful to reduce the presence thereof. After such removal of organic substances, thermal oxidation was performed in an oxygen atmosphere at a temperature of 640 ° C. to form a 100 Å thermal oxide film 451. This thermal oxide film has a high interface characteristic with the semiconductor layer, and will form a part of the gate insulating film later. Thus, the state shown in FIG.

(4) Thereafter, a silicon oxide film 455 constituting a gate insulating film was formed to a thickness of 1000 Å. The silicon oxide film 455 was formed by a plasma CVD method. The silicon oxide film 455 functions as a gate insulating film integrally with the thermal oxide film 451. Note that it is effective to include a halogen element in the silicon oxide film 455. In this case, the nickel element can be fixed by the action of the halogen element. In addition, it is possible to suppress a decrease in the function of the gate insulating film as an insulating film due to the effect of the nickel element (and other metal elements that promote crystallization of silicon) existing in the active layer. it can.

Next, an aluminum film (not shown), which later functions as a gate electrode, was formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium. Scandium is contained in the aluminum film in order to suppress generation of hillocks and whiskers in a later step. Here, the hillocks and whiskers mean needle-like or barbed protrusions caused by abnormal growth of aluminum during heating.

後 After forming the aluminum film as described above, a dense anodic oxide film (not shown) was formed. This anodic oxide film was formed by using an ethylene glycol solution containing 3% by weight of tartaric acid as an electrolytic solution, using an aluminum film as an anode and platinum as a cathode. In this step, an anodic oxide film having a dense film quality was formed to a thickness of 100 Å on the aluminum film. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film was controlled by the voltage applied during anodic oxidation.

Next, a resist mask 457 was formed, and the aluminum film was patterned into a pattern indicated by 456. Thus, the state shown in FIG. 52B is obtained. Here, anodic oxidation was performed again. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 456 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 459 was formed.

In this step, the anodic oxide film 459 is selectively formed on the side surface of the aluminum pattern 456 because the resist mask 457 having high adhesion exists on the upper portion. This anodic oxide film 459 can be grown to a thickness of several μm. Here, the thickness was set to 6000 Å. The growth distance can be controlled by the anodic oxidation time.

(4) After removing the resist mask 457, a dense anodic oxide film was formed again. That is, anodic oxidation was again performed using the ethylene glycol solution containing tartaric acid of 3% by weight as an electrolytic solution. In this step, as indicated by reference numeral 460, an anodic oxide film having a dense film quality was formed due to the electrolytic solution entering (invading) into the porous anodic oxide film 459.

(4) The thickness of the dense anodic oxide film 460 was 1000 Å, but the thickness was controlled by the applied voltage. Next, the exposed silicon oxide film 455 was etched, and simultaneously, the thermal oxide film 451 was etched. For this etching, dry etching was used. Then, the porous anodic oxide film 459 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 52D is obtained.

(4) Thereafter, impurity ions were implanted. Here, P (phosphorus) ions were implanted by a plasma doping method in order to manufacture an N-channel thin film transistor. In this step, regions 462 and 466 to be heavily doped and regions 463 and 465 to be lightly doped are formed. This is because the remaining silicon oxide film 461 functions as a semi-transparent mask, and a part of the implanted ions is shielded there.

Next, the region into which the impurity ions were implanted was activated by irradiating a laser beam. Strong light can be applied instead of the laser light. Thus, a source region 462, a channel formation region 464, a drain region 466, and low-concentration impurity regions 463 and 465 were formed in a self-aligned manner. Here, what is indicated by reference numeral 465 is a region called an LDD (lightly doped drain) region.

In the case where the dense anodic oxide film 460 has a thickness as large as 2000 Å or more, an offset gate region can be formed outside the channel formation region 464 with the thickness. Although the offset gate region is also formed in the present embodiment, its size is small, so its contribution due to its existence is small, and the drawing is complicated, so it is not shown in the drawing. It should be noted that forming an anodic oxide film having a dense film quality as thick as 2000 Å or more requires an applied voltage of 200 V or more.

Next, a silicon oxide film, a silicon nitride film, or a laminated film thereof is formed as the interlayer insulating film 467. Here, the laminated film is formed. As the interlayer insulating film, a layer made of a resin material may be used over a silicon oxide film or a silicon nitride film. Then, a contact hole was formed, and a source electrode 468 and a drain electrode 469 were formed. Thus, a thin film transistor shown in FIG. 52E was obtained.

<< Example 62 >>
Embodiment 62 is an example in which a thin film transistor is manufactured by a process different from the process shown in Embodiment 61 (FIG. 52). FIG. 53 shows a manufacturing process of this embodiment. First, a crystalline silicon film was formed on a glass substrate by the steps shown in Example 58 and Example 60. Then, by patterning it, the state shown in FIG. 53 (A) was obtained. The following steps are the same for both.

を 得 After obtaining the state shown in FIG. 53A, plasma treatment was performed in a reduced-pressure atmosphere of a mixture of oxygen and hydrogen. In the state shown in FIG. 53A, 471 is a glass substrate, 472 is a base film made of a silicon oxide film, and 473 is an active layer formed of a crystalline silicon film. Reference numeral 470 denotes a thermal oxide film formed again after removing the thermal oxide film for gettering. Next, as shown in FIG. 53B, a silicon oxide film 474 forming a gate insulating film was formed to a thickness of 1000 angstroms by a plasma CVD method.

(4) The silicon oxide film 474 forms a gate insulating film together with the thermal oxide film 470. Next, an aluminum film (not shown) which later functions as a gate electrode was formed by a sputtering method. This aluminum film contained 0.2% by weight of scandium. After forming the aluminum film, a dense anodic oxide film (not shown) was formed on the surface. The anodic oxide film was formed using an ethylene glycol solution containing tartaric acid at 3% by weight as an electrolytic solution.

膜厚 The thickness of the anodic oxide film having a dense film quality (not shown) was about 100 Å. This anodic oxide film has a role of improving adhesion to a resist mask to be formed later. The thickness of the anodic oxide film can be controlled by the voltage applied during anodic oxidation. Next, a resist mask 475 was formed. Then, the aluminum film was patterned into a pattern indicated by reference numeral 476.

(5) Next, anodic oxidation was performed again. Here, a 3 wt% oxalic acid aqueous solution was used as the electrolytic solution. By performing anodic oxidation using the aluminum pattern 476 as an anode in this electrolytic solution, a porous anodic oxide film indicated by reference numeral 477 was formed. In this step, the anodic oxide film 477 is selectively formed on the side surface of the aluminum pattern 476 due to the presence of the resist mask 475 having high adhesion on the upper portion.

The anodic oxide film can be grown to a thickness of several μm. Here, the film thickness was 6000 Å. The growth distance can be controlled by the anodic oxidation time. Next, after removing the resist mask 475, a dense anodic oxide film was formed again. That is, the anodic oxidation using the ethylene glycol solution containing 3% by weight of tartaric acid as the electrolytic solution was performed again. Then, since the electrolytic solution enters (penetrates) into the porous anodic oxide film 477, an anodic oxide film having a dense film quality is formed as indicated by reference numeral 478.

Next, the first implantation of impurity ions was performed. Here, P (phosphorus) ions were implanted in order to manufacture an N-channel thin film transistor. Note that if a P-channel thin film transistor is to be manufactured, B (boron) ions are implanted. By the implantation of the impurity ions, a source region 479 and a drain region 481 are formed. At this time, no impurity ions are implanted into the region 480. Next, the porous anodic oxide film 477 was removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 53D is obtained.

Thereafter, impurity ions (phosphorus ions) were implanted again. The impurity ions were implanted under light doping conditions (lower dose) than the initial impurity ion implantation conditions. In this step, lightly doped regions 482 and 483 are formed, and a region indicated by reference numeral 484 becomes a channel formation region.

Next, the region into which the impurity ions were implanted was activated by irradiating a laser beam. Note that strong light such as infrared light or ultraviolet light may be applied instead of laser light. Thus, a source region 479, a channel formation region 484, a drain region 481, and low-concentration impurity regions 482 and 483 were formed in a self-aligned manner. Here, what is indicated by reference numeral 483 is a region called an LDD (lightly doped drain) region.

Next, a silicon oxide film, a silicon nitride film, or a stacked film thereof is formed as the interlayer insulating film 485. Here, the silicon oxide film or the silicon nitride film is formed using a silicon nitride film. As the interlayer insulating film, a film obtained by forming a layer made of a resin material on a silicon oxide film or a silicon nitride film may be used. Then, a contact hole was formed, a source electrode 486 and a drain electrode 487 were formed, and a heat treatment (hydrogenation heat treatment) was performed in a hydrogen atmosphere at a temperature of 350 ° C. for one hour. In this step, defects and dangling bonds in the active layer are neutralized. Thus, a thin film transistor shown in FIG. 53E was obtained.

<< Example 63 >>
The 63rd embodiment is an example in which an N-channel thin film transistor and a P-channel thin film transistor are configured to be complementary. The configuration shown in this embodiment can be used, for example, for various thin film integrated circuits integrated on an insulating surface. Further, for example, it can be used for a peripheral drive circuit of an active matrix type liquid crystal display device. FIG. 54 is a diagram showing the steps of this embodiment.

First, as shown in FIG. 54A, a silicon oxide film was formed as a base film 490 over a glass substrate 489. Note that a silicon nitride film may be used instead of the silicon oxide film. Next, an amorphous silicon film (not shown) is formed by a plasma CVD method or a low pressure thermal CVD method, but the former is used here. Further, the amorphous silicon film was transformed into a crystalline silicon film by the method shown in Example 58. After performing a plasma treatment in a mixed atmosphere of oxygen and hydrogen, the crystalline silicon film was patterned to obtain active layers 491 and 492. Thereafter, a thermal oxide film indicated by reference numeral 488 was formed. The thickness of the thermal oxide film 488 was about 100 Å. Thus, the state shown in FIG.

  Next, a silicon oxide film as a gate insulating film 493 was formed. Then, an aluminum film (not shown) for forming a gate electrode was formed to a thickness of 4000 Å by sputtering. As the metal other than the aluminum film, an anodizable metal (for example, tantalum) can be used. After the formation of the aluminum film, an extremely thin and dense anodic oxide film (not shown) was formed on the surface by the above-described method.

Next, a resist mask (not shown) was arranged on the aluminum film, and the aluminum film was patterned. Then, anodic oxidation was performed using the obtained aluminum pattern as an anode to form porous anodic oxide films 496 and 497. The thickness of the porous anodic oxide film was 5000 Å. Next, the resist mask (not shown) was removed, and anodic oxidation was performed again under the condition that a dense anodic oxide film was formed. In this step, dense anodic oxide films 498 and 499 were formed.

膜厚 Here, the thickness of the dense anodic oxide films 498 and 499 was set to 800 Å. Thus, the state shown in FIG. 54B is obtained. Further, the exposed silicon oxide film 493 and thermal oxide film 488 were removed by dry etching to obtain a state shown in FIG. Thereafter, the porous anodic oxide films 496 and 497 were removed using a mixed acid obtained by mixing acetic acid, nitric acid, and phosphoric acid. Thus, the state shown in FIG. 54D is obtained.

Here, resist masks were alternately arranged so that P (phosphorus) ions were implanted into the left thin film transistor and B (boron) ions were implanted into the right thin film transistor, and these were implanted by the plasma doping method. By the implantation of the impurity ions, a source region 502 and a drain region 505 having a high concentration of N-type were formed in a self-aligned manner. At the same time, a weakly N-type region 503 doped with P ions at a low concentration was formed, and a channel formation region 504 was formed at the same time.

<< Here, the region having the weak N-type indicated by reference numeral 503 is formed because the remaining gate insulating film 500 exists. That is, the P ions transmitted through the gate insulating film 500 are partially shielded by the gate insulating film 500. Further, a source region 509 and a drain region 506 having a strong P type were formed in a self-alignment manner by the same principle and method. At the same time, a low concentration impurity region 508 was formed, and a channel formation region 507 was formed at the same time.

In the case where the dense anodic oxide films 498 and 499 are as thick as 2000 angstroms, the offset gate region can be formed in contact with the channel forming region with the thickness. In the case of the present embodiment, since the dense anodic oxide films 498 and 499 have a thin film thickness of 1000 angstroms or less, their existence can be neglected.

Next, laser light irradiation was performed to anneal the region into which the impurity ions had been implanted. Note that strong light such as ultraviolet light may be applied instead of laser light. Then, as shown in FIG. 54E, a silicon nitride film 510 and a silicon oxide film 511 were formed as interlayer insulating films, and the thickness of each was set to 1000 Å. Note that the silicon oxide film 511 is not necessarily formed. Here, the thin film transistor is covered with the silicon nitride film. Since the silicon nitride film is dense and has good interface characteristics, with such a structure, the reliability of the thin film transistor can be increased.

(4) Further, an interlayer insulating film 512 made of a resin material was formed by using a spin coating method. Here, the thickness of the interlayer insulating film 512 is 1 μm. Then, a contact hole was formed, and a source electrode 513 and a drain electrode 514 of the left N-channel thin film transistor were formed. At the same time, a source electrode 515 and a drain electrode 514 of the right thin film transistor were formed. Here, the drain electrode 514 is arranged commonly to both.

Thus, a thin film transistor circuit having a complementary CMOS structure was formed as shown in FIG. In the structure shown in this embodiment, a structure in which the thin film transistor is covered with a silicon nitride film and further covered with a resin material is obtained. With this configuration, it is possible to provide a highly durable one in which mobile ions and moisture hardly enter. In addition, when a multilayer wiring is formed, it is possible to prevent a capacitance from being formed between the thin film transistor and the wiring.

<< Example 64 >>
The sixty-fourth embodiment is an example in which the nickel element is directly introduced into the surface of the base film in the process shown in the fifty-eighth embodiment. In this case, the nickel element is held in contact with the lower surface of the amorphous silicon film. In the case of this method, the nickel element is introduced after the formation of the base film, and first, the nickel element (the metal element) is brought into contact with and held on the surface of the base film.

In this example, an aqueous solution of nickel acetate was applied to the surface of the underlayer, and the other steps were the same as in Example 58 to obtain the state shown in FIG. As a method for introducing the nickel element, a sputtering method, a CVD method, and an adsorption method can be used in addition to the method using such a solution.

<< Example 65 >>
In Example 65, laser light irradiation was performed in the state of FIG. 51E, the state of FIG. 52A, or the state of FIG. This is an example in which the crystallinity of an island-like pattern made of a film is further improved. When laser light irradiation is performed in the states shown in FIGS. 51E, 52A, and 53A, a predetermined annealing effect can be obtained with a relatively low irradiation energy density. This is considered to be because the energy of the laser used for annealing is increased because the laser energy is applied to a small area.

<< Example 66 >>
Example 66 Example 66 relates to an example of manufacturing a bottom-gate thin film transistor. FIG. 55 shows a manufacturing process of the thin film transistor of this embodiment. First, a silicon oxide film 517 was formed over a glass substrate 516 as a base film.

(4) Next, the gate electrode 518 is formed using an appropriate metal material or a metal silicide material. In this case, aluminum is used. After forming the gate electrode 518, a silicon oxide film 519 functioning as a gate insulating film was formed. Further, an amorphous silicon film 520 was formed by a plasma CVD method. Next, as shown in FIG. 55B, a nickel acetate aqueous solution is applied, and the nickel element comes into contact with the surface of the amorphous silicon film 520 as indicated by reference numeral 521 as a liquid film of the nickel acetate aqueous solution. And held.

Next, heat treatment was performed at a temperature of 650 ° C. in a nitrogen atmosphere containing 3% by volume of hydrogen to crystallize the amorphous silicon film 520. Thus, a crystalline silicon film 522 was obtained. The crystalline silicon film was subjected to a heat treatment at a temperature of 650 ° C. in an oxygen atmosphere containing 5% by volume of HCl and 100 ppm (by volume) of NF ₃ . A thermal oxide film 523 was formed by this heat treatment, and after the state shown in FIG. 55C was obtained, the thermal oxide film 523 was removed.

Next, the crystalline silicon film 522 and the silicon oxide film 519 were patterned to form a gate insulating film 525 and an active layer 526 of a thin film transistor. Further, as shown in FIG. 55D, a resist mask 524 was provided. In the state of FIG. 55D, impurity ions were implanted to form source and drain regions. Here, P (phosphorus) ions were implanted in order to manufacture an N-channel thin film transistor. In this step, a source region 527 and a drain region 528 are formed.

(4) Thereafter, isotropic ashing was performed, and the resist mask 524 was entirely retracted. That is, as shown by reference numeral 529 in FIG. 55E, the size of the resist mask 524 is reduced as a whole. Thus, the retreated resist mask 529 was obtained. Next, in the state of FIG. 55E, P ion implantation was performed again.

This step was performed with a dose smaller than the dose of P ions in the step shown in FIG. Thus, low concentration impurity regions indicated by reference numerals 530 and 531 were formed. Next, metal electrodes 532 and 533 were formed. Here, the electrode 532 becomes a source electrode, and the electrode 533 becomes a drain electrode. Thus, a bottom gate type thin film transistor was completed.

<< Premise of Embodiment 67 >>
FIGS. 56 to 57 are explanatory diagrams of the manufacturing process of the thin film transistor (TFT), and are also explanatory diagrams of the TFT manufacturing process in Example 67 described later. Therefore, a specific example of the invention, which is a premise of the embodiment 67, will be described first with reference to FIGS.

In FIG. 56A, a base film 535 and an amorphous silicon film 536 are sequentially stacked over a glass substrate 534, and a nickel (Ni) layer 537 is formed on the surface of the amorphous silicon film 536. I have. By performing heat treatment in this state, the amorphous silicon film 536 is crystallized as shown in FIG. 56B, so that a crystalline silicon film 538 is formed. In this embodiment, the step of forming the nickel layer 537 is not an essential step. However, since nickel functions as a catalyst for reducing the heat energy required for crystallization, the heating temperature of the crystallization treatment is reduced and the treatment time is shortened. It becomes possible.

As such a catalyst element, besides nickel (Ni), at least one element selected from Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can be used. Nickel has the most remarkable catalytic effect. Note that it is also possible to form the crystalline silicon film by using a known technique or the like without using the nickel element. In the crystallization step, a laser beam may be irradiated instead of the heat treatment. Further, after forming the crystalline silicon film, light annealing using laser light or infrared light or thermal annealing may be performed.

FIG. 56 (C) illustrates a thermal oxidation step. As the thermal oxide film 539 grows on the surface of the crystalline silicon film 538, that is, as the Si—O bond is formed, unbonded Si is generated. This surplus Si diffuses from the interface between the thermal oxide film 539 and the crystalline silicon film 538 into the crystalline silicon film 538 and combines with the Si dangling bonds existing at the crystal grain boundaries to form the crystalline silicon. Defects at grain boundaries of the film 538 are passivated. Thus, the mobility of the TFT including the crystalline silicon film 538 can be improved.

(4) In the subsequent manufacturing process involving heating, Si that has passivated defects does not easily separate from the crystalline silicon film 538 as H does, so that hydrogen plasma treatment can be omitted. For example, for an N-channel TFT manufactured according to the method for manufacturing a semiconductor device according to the present invention, the mobility after hydrogen plasma treatment is increased by only 10 to 20% as compared with the mobility before hydrogen plasma treatment. This suggests that the defects in the crystalline silicon film 538 are sufficiently passivated in the thermal oxidation step, and also suggests that the Si passivating the defects is not released during the manufacturing process. .

The purpose of the thermal oxidation step in the present invention is to supply Si for passivating defects at grain boundaries of the crystalline silicon film. Considering that the crystalline silicon film 538 forms an active layer of the TFT, The thermal oxide film 539 may be grown to a film thickness of about 200 to 500 angstroms without considering film properties such as pressure resistance. In addition, since the present invention intends to manufacture a TFT on a glass substrate or the like, it is necessary to perform the thermal oxidation step under conditions where distortion, deformation, and the like of the substrate caused by heating can be tolerated. For example, the upper limit of the heating temperature may be set based on the strain point of the glass substrate.

In this embodiment, the thermal oxidation step is performed in an oxidizing atmosphere to which a fluorine compound has been added. Specifically, thermal oxidation is performed in an atmosphere in which NF ₃ gas or the like is added to oxygen gas. By appropriately adjusting the concentration of the NF ₃ gas, it is possible to grow a thermal oxide film to a thickness of several hundred angstroms by heating for several hours to several tens of hours at a temperature below the strain point of the glass substrate. It is.

By adding a gas that supplies Cl radicals, such as HCl, to the oxidizing atmosphere in addition to a gas that supplies fluorine radicals, such as NF ₃ gas, the growth of a thermal oxide film is promoted. It is not appropriate to form a thermal oxide film having a thickness of several hundred angstroms at a temperature below the strain point, for example, at a temperature of about 500 ° C. to 600 ° C., which is not suitable. In an oxidizing atmosphere in which 450 ppm of NF ₃ gas is added to oxygen gas, a thermal oxide film of about 200 Å can be formed by heating at 600 ° C. for 4 hours.

Further, in the thermal oxidation step, the fluorine radicals are supplied to the convex portions on the surface of the crystalline silicon film 538 in a concentrated manner, so that the thermal oxidation of the convex portions progresses most and the thermal oxidation of the concave portions is suppressed. . In addition, since the thermal oxide film 539 contains fluorine at a high concentration, stress is relieved. Therefore, the thermal oxide film 539 has a uniform thickness on the surface of the crystalline silicon film 538 in a state where the convex portion is rounded. Is formed.

In the thermal oxidation step, since the heating temperature and the heating time need to be determined so that the distortion or deformation of the substrate is within an allowable range, the concentration of the fluorine compound in the thermal oxidation atmosphere may increase. . As a result, there is a possibility that a large amount of fluorine is contained in the thermal oxide film 538 and a Si—F bond is formed. However, the thermal oxide film 539 is a film grown to supply Si for passivating defects at grain boundaries of the crystalline silicon film, and is formed as a film to be removed later. Does not require high functionality and high reliability like the gate insulating film, and does not matter the instability such as Si—F bond existing in the thermal oxide film 539 or the pressure resistance.

FIG. 56D is a diagram showing an active layer 540 and a gate insulating film 541 formed by patterning the crystalline silicon film 538 after the thermal oxide film 539 is removed. Although a thermal oxidation method can be used to form the gate insulating film 541, a thermal oxide film obtained by thermally oxidizing a glass substrate at a low temperature at which deformation thereof is acceptable is excellent. Absent. Therefore, in this embodiment, in order to stably obtain a gate insulating film having predetermined characteristics, the gate insulating film is formed by a deposition method such as a plasma CVD method or a sputtering method.

In this embodiment, the surface of the active layer 540 (the crystalline silicon film 538) is planarized by the thermal oxidation process. Can be made favorable. For this reason, it becomes possible to lower the interface state between the gate insulating film and the active layer.

Although a crystalline silicon film obtained by irradiating a laser beam has excellent crystallinity, a ridge having a steep projection is formed on the surface thereof. For example, an amorphous silicon film having a thickness of about 700 Å is formed. When the laser annealing is performed after the silicon film is heated and siliconized, a ridge having a height of about 100 to 300 Å is formed on the surface.

For example, by performing thermal oxidation for 12 hours in an atmosphere in which NF ₃ gas is added to oxygen gas at about 450 ppm to form a thermal oxide film having a thickness of about 500 Å, the height difference of the crystalline silicon film surface is reduced by several tens of degrees. Angstroms can be used. Therefore, the insulating film can be deposited with good coverage on the surface of the crystalline silicon film crystallized by the laser beam by the CVD method.

FIG. 57 (A) illustrates a step of doping impurity ions. The gate electrode 542 functions as a mask, and a source region 544, a drain region 545, and a channel region 546 are formed in a self-aligned manner. Further, as shown in FIG. 57B, an interlayer insulating film 547 and electrodes 548 and 549 are formed to complete a TFT.

<< Example 67 >>
Example 67 is an example in which a TFT is manufactured using a silicon film crystallized by utilizing the catalytic action of a metal element that promotes crystallization of silicon. FIG. 56 and FIG. 57 are explanatory views of the manufacturing process of the TFT in this embodiment, and are cross-sectional views for each process. In this example, nickel was used as the metal element.

As shown in FIG. 56A, a 3000-Å-thick silicon oxide film is formed as a base film 535 on a glass substrate 534 (Corning 1737, strain point 667 ° C.) by a plasma CVD method or a low pressure thermal CVD method. I do. Next, a substantially intrinsic (I-type) amorphous silicon film 536 is formed to a thickness of 700 to 1000 angstroms by a plasma CVD method or a low pressure thermal CVD method. Here, a low-pressure thermal CVD method was used for both film formation, and the film thickness of the amorphous silicon film 536 was set to 700 angstroms.

In an oxidizing atmosphere, UV (ultraviolet) light is irradiated on the surface of the amorphous silicon film 536 to form an oxide film (not shown) with a thickness of several tens of angstroms on the surface. A solution containing a nickel element was applied. The oxide film is for improving the wettability of the surface of the amorphous silicon film 538 and suppressing the repelling of the solution. In this example, a nickel acetate aqueous solution having a nickel content (weight) of 55 ppm was used as the solution containing the nickel element.

In this example, a nickel acetate solution was applied by a spinner and dried to form a nickel layer 537. Although the nickel layer 537 does not always form a complete film, in this state, the nickel element is held in contact with the surface of the amorphous silicon film 536 via the oxide film (not shown). It is preferable to use a dilute solution of a nickel salt as the solution, but it is preferable to use a solution having a nickel content of about 1 to 100 ppm.

Here, if the nickel concentration in the amorphous silicon film is 1 × 10 ¹⁶ atoms / cm ⁻³ or less, it is difficult to obtain the effect of promoting crystallization. On the other hand, if the nickel concentration is 5 × 10 ¹⁹ atoms / cm ³ or more, the characteristics of the obtained silicon film as a semiconductor are impaired, and the characteristics as a metal appear. For this reason, the concentration of nickel in the nickel acetic acid solution, the number of coating times, the coating amount, and the like are determined in advance so that the average nickel concentration in the finally obtained silicon film is 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ^3. Step conditions are set. Note that the nickel concentration may be measured by SIMS (secondary ion mass spectrometry).

In the state where the nickel element is held on the surface of the amorphous silicon film 536 as shown in FIG. 56A, heat treatment is performed in a nitrogen atmosphere as shown in FIG. 536 was crystallized to form a crystalline silicon film 538. To crystallize silicon, it is necessary to heat at a temperature of 450 ° C. or more. However, at a temperature of about 450 ° C. to 500 ° C., it takes tens of hours or more to crystallize an amorphous silicon film. It is desirable to heat at a temperature of at least ℃. Note that the heating temperature is not limited to the crystallization step illustrated in FIG. 56B and needs to be in a range where deformation and shrinkage of the glass substrate caused by heating can be tolerated.

基準 The upper limit of the heating temperature may be, for example, the strain point of the substrate. In this embodiment, since the glass substrate 534 having a strain point of 667 ° C. is used, heating was performed at 620 ° C. for 4 hours. This heating causes nickel to diffuse from the surface of the amorphous silicon film 536 to the interface with the base film 535 in a direction substantially orthogonal to the surface of the glass substrate 534, and crystal growth of silicon proceeds. Thus, a crystalline silicon film 538 is formed. This crystal growth proceeds in a direction perpendicular to the glass substrate 534. Such a crystallization process is referred to as vertical growth.

Note that if necessary, after the crystallization step, light annealing using laser light, infrared light, or ultraviolet light or thermal annealing may be performed to further improve the crystallinity of the crystalline silicon film 538. Light annealing and thermal annealing may be used in combination. However, when laser annealing is performed, a film of the amorphous silicon film 536 which is a starting film of the crystalline silicon film 538 is provided in order to effectively supply thermal energy to the crystalline silicon film 538 by laser light. The thickness is less than 1000 angstroms, preferably about 700 to 800 angstroms.

Next, by heating in an oxidizing atmosphere containing a fluorine atom, a thermal oxide film 539 is formed to a thickness of 200 to 500 Å on the surface of the crystalline silicon film 538. In this embodiment, the thermal oxide film 539 was formed to a thickness of about 200 angstroms by heating at a temperature of 600 ° C. for 4 hours in an atmosphere in which 400 ppm (capacity) of NF ₃ was added to oxygen gas.

As a result, the thickness of the crystalline silicon film 538 was about 700 angstroms before the thermal oxide film 539 was formed, but became about 600 angstroms. Since the crystalline silicon film 538 finally constitutes the active layer of the TFT, a non-crystalline silicon film 538 is formed in consideration of the thickness of the oxide film 539 so that an active layer having a required thickness can be obtained. It is necessary to determine the thickness of the crystalline silicon film 536 in advance.

(4) As the thermal oxide film 539 is formed on the surface of the crystalline silicon film 538, unbonded Si is generated. This excess Si diffuses from the interface between the thermal oxide film 539 and the crystalline silicon film 538 into the inside of the crystalline silicon film 538 and combines with the Si dangling bonds existing at the crystal grain boundaries to form the crystalline silicon. The defect density at the crystal grain boundary of the silicon film 538 is reduced. Further, in the subsequent manufacturing process involving heating, Si passivating a defect does not easily separate from the crystalline silicon film 538 unlike H, and thus the crystalline silicon film 538 is used for a semiconductor device such as a TFT. It is suitable for the material.

Further, the surface of the crystalline silicon film 538 is rounded and flattened due to the difference in the oxidation rate between the convex and concave portions. Note that when the crystalline silicon film 538 is irradiated with laser light as described above, a ridge is formed on the surface thereof. The thermal oxidation process conditions such as the thickness of the thermal oxide film 539 and the NF ₃ gas concentration may be set in consideration of the thickness of the crystalline silicon film 538 after the process.

Next, as shown in FIG. 56D, the thermal oxide film 539 is removed by etching. In this etching, an etching solution or an etching gas having a high etching rate between silicon oxide and silicon is used. As the etchant, buffer hydrofluoric acid or another hydrofluoric acid-based etchant is preferably used. In this embodiment, the thermal oxide film 539 is removed by wet etching using buffer hydrofluoric acid.

Next, after the crystalline silicon film 538 was patterned into an island shape to form a TFT active layer 540, a silicon oxide film was formed as a gate insulating film 541 to a thickness of 1000 angstroms by a plasma CVD method. Since the surface of the active layer 540 is flattened in the thermal oxidation step, the gate insulating film 541 can be deposited with good coverage. Thereafter, an aluminum film containing a small amount of scandium (not shown) is formed on the surface of the gate insulating film 541 by electron beam evaporation to a thickness of 6000 angstroms, and is patterned as shown in FIG. An electrode 542 was formed.

{Circle around (2)} Then, in the electrolytic solution, anodization was performed using the gate electrode 542 as an anode to form an oxide layer 543. In this case, by applying a voltage in an ethylene glycol solution containing 3% by weight of tartaric acid with the gate electrode 542 as an anode and platinum as a cathode, the anodic oxide layer 543 having a dense structure is formed in 2000. Angstrom thickness. Note that the film thickness of the anodic oxide 543 can be controlled by the voltage application time, and this is also controlled in this embodiment.

Next, as shown in FIG. 57A, impurity ions for imparting one conductivity type to the active layer 540 are formed by an ion implantation method, a plasma ion implantation method, or the like in order to form the source region 544 and the drain region 545. inject. In the case of forming an N-channel TFT, P (phosphorus) ions are implanted into the active layer 540 using phosphine diluted to 1 to 10% (capacity) with H ₂ gas. On the other hand, when fabricating a P-channel TFT, B (boron) ions are implanted using diborane also diluted to 1 to 10% (capacity). In this embodiment, N-channel and P-channel TFTs are manufactured by implanting P ions and B ions, respectively, by an ion implantation method.

When the impurity ions are implanted into the active layer 540, the gate electrode 542 and the surrounding anodic oxide 543 function as a mask, and the region into which the impurity ions are implanted is defined as a source region 544 and a drain region 545. The region where no ions are implanted is defined as channel 546. Note that doping conditions such as a dose amount and an acceleration voltage are controlled so that the concentration of impurity ions in the source region 544 and the drain 545 is 3 × 10 ¹⁹ to 1 × 10 ²¹ atoms / cm ³ . In addition, laser light is irradiated after doping to activate the impurity ions implanted into the source region 544 and the drain region 545.

Next, as shown as an interlayer insulating film 547 in FIG. 57B, a silicon oxide film was formed to a thickness of 7000 angstroms by a plasma CVD method. Next, contact holes were formed, and electrodes 548 and 549 connected to the source region 544 and the drain region 545 were formed using a material mainly containing aluminum.

(5) Finally, hydrogen plasma treatment was performed at a temperature of 300 ° C. to complete the thin film transistor shown in FIG. 57 (B). Note that this hydrogen plasma treatment is not mainly for passivation of defects in the active layer 540 but mainly for passivation at the interface between the active layer 540 and the electrodes 548 and 549 made of aluminum.

電 界 The field-effect mobility of the P-channel TFT manufactured according to the manufacturing process of this example did not significantly change between before and after the hydrogen plasma treatment. This is not because the thermal oxidation step shown in FIG. 56C does not have the effect of passivation. As described above, the passivation using only the hydrogen plasma treatment does not significantly improve the field-effect mobility of the P-channel TFT. As expected from the above, in the P-channel type TFT, passivating the defects at the crystal grain boundaries of the active layer 540 is considered to be because it is not the best means for improving the field effect mobility.

On the other hand, the N-channel TFT manufactured according to the manufacturing process of this embodiment had a field-effect mobility of 200 cm ² · V ^-1 · s ^-1 before performing the hydrogen plasma treatment. After the treatment, the field effect mobility increased only by about 10 to 20%. This fact indicates that the N-channel type TFT was not practical unless it was subjected to hydrogen plasma treatment in the past. However, as in the present embodiment, only the NF ₃ was added and the thermal oxidation treatment was performed. This suggests that it is possible to fabricate a type TFT.

That is, in the hydrogen plasma treatment, there are not many defects at the crystal grain boundaries of the active layer 540 passivated by hydrogen, and most of the defects at the crystal grain boundaries have been passivated in the thermal oxidation step shown in FIG. Is shown. Therefore, most of the defects passivated by the hydrogen plasma treatment of the present embodiment are defects generated after the thermal oxidation step, and are mainly generated when the electrodes 548 and 549 are formed. Further, in this embodiment, defects at the crystal grain boundaries of the active layer 540 are passivated with Si. Since Si is not easily separated from the active layer due to the thermal influence like H, the present invention can form a highly reliable TFT having excellent heat resistance.

<< Example 68 >>
Example 68 is an example in which a TFT is manufactured using a silicon film crystallized by utilizing the catalytic action of a metal element that promotes crystallization of silicon. FIGS. 58 and 59 are explanatory views of the manufacturing process of the TFT of this example, and are cross-sectional views for each process. In this embodiment, nickel was used as the metal element.

As shown in FIG. 58A, a silicon oxide film is formed as a base film 551 to a thickness of 3000 angstroms on a glass substrate 550 (Corning 1737, strain point 667 ° C.) by a plasma CVD method or a low pressure thermal CVD method. I do. Here, a plasma CVD method was used. Next, a substantially intrinsic amorphous silicon film 552 was formed to a thickness of 700 to 1000 Å by a plasma CVD method or a low pressure thermal CVD method. Here, the thickness of the amorphous silicon film 552 was formed to be 1000 Å by a plasma CVD method.

(4) In an oxidizing atmosphere, UV (ultraviolet) light was applied to the surface of the amorphous silicon film 552 to form an oxide film (not shown) with a thickness of several 20 angstroms on the surface. This oxide film is for improving the wettability of the surface of the amorphous silicon film 552 and for preventing the solution from being repelled. Next, a mask film 553 having an opening 554 made of a silicon oxide film having a thickness of 1500 angstroms was formed on the surface of the oxide film (not shown).

開 The opening 554 has a slit-like shape in the longitudinal direction in a direction perpendicular to the paper surface (from the near side to the depth direction). The width of the opening 554 is suitably 20 μm or more, while the length in the longitudinal direction is appropriately determined according to the substrate size and the like. Here, the width was 50 μm, and the length in the longitudinal direction was 3 cm.

Next, a nickel acetate solution containing 55 ppm (by weight) of a nickel element was applied by a spinner and dried to form a nickel layer 555. Although the nickel layer 555 does not always form a complete film, in this state, the nickel element is formed in the opening 554 of the mask film 553 through the oxide film (not shown) through the oxide film (not shown). It is held in contact with the surface. It is preferable to use a dilute solution of a nickel salt as the solution, but it is preferable to use a solution having a nickel content in the range of about 1 to 100 ppm (weight).

Next, the amorphous silicon film 552 was crystallized by heating at a temperature of 620 ° C. for 4 hours to form a crystalline silicon film 556. By this heating, the crystal grows vertically from the surface of the region 557 exposed in the opening 554 of the mask film 553 to the base film 551 in the amorphous silicon film 552, so that the region 557 becomes a vertical growth region. .

On the other hand, in the region 558, the crystal growth proceeds in parallel with the surface of the substrate 550, starting from the vertical growth region 557, as indicated by the arrow in FIG. The crystallization process in which the crystal grows in one direction is referred to as lateral growth. Therefore, the region 558 in the crystalline silicon film 556 is a lateral growth region.

(4) Thereafter, the mask film 553 made of the silicon oxide film was removed. Next, as shown in FIG. 58C, a thermal oxide film 559 is formed to a thickness of 200 to 500 Å on the surface of the crystalline silicon film 556 by heating in an oxidizing atmosphere containing fluorine atoms. . Note that, if necessary, before the thermal oxidation step, light annealing using laser light or infrared light or thermal annealing may be performed to further improve the crystallinity of the crystalline silicon film 556. Light annealing and thermal annealing may be used in combination.

In the thermal oxidation step in this embodiment, the thermal oxide film 559 is heated at a temperature of 600 ° C. for 12 hours in an atmosphere in which 450 ppm (capacity) of NF ₃ gas is added to an oxygen atmosphere to form a thermal oxide film 559 having a film thickness of about 500 Å. Formed. As a result, the thickness of the crystalline silicon film 556 was changed from about 1000 Å before the thermal oxidation step to about 750 Å.

(4) As the thermal oxide film 559 is formed on the surface of the crystalline silicon film 556, unbonded Si is generated. The Si atoms combine with dangling bonds of Si at the crystal grain boundaries of the crystalline silicon film 556, and the defects of the crystalline silicon film 556 are passivated. By forming the silicon oxide film 559 to a thickness of about 500 angstroms with respect to the crystalline silicon film 556 having a thickness of 1000 angstroms, the defect density of crystal grain boundaries of the crystalline silicon film 556 can be sufficiently reduced.

Next, as shown in FIG. 58D, the thermal oxide film 559 was removed by etching. In this etching step, an etching solution or an etching gas having a high etching rate between silicon oxide and silicon is used. In this embodiment, the thermal oxide film 559 was removed by wet etching using buffered hydrofluoric acid.

Next, as shown in FIG. 58E, the crystalline silicon film 556 was etched into an island shape to form a TFT active layer 560. In this case, it is preferable that the active layer 560 be constituted only by the lateral growth region 558. Next, a silicon oxide film 561 forming a gate insulating film is formed on the surface of the active layer 560 by a plasma CVD method or a low-pressure CVD method. Here, the low-pressure CVD method is used.

(5) Further, an aluminum film constituting the gate electrode 562 was deposited on the surface of the silicon oxide film 561 to a thickness of 5000 angstroms by a sputtering method. If a small amount of scandium is previously contained in aluminum, it is possible to suppress generation of hillocks and whiskers in a subsequent heating step or the like. Here, however, scandium was contained at 0.2% by weight.

Next, the surface of the aluminum film was anodized to form a very thin dense anodic oxide (not shown), and then a resist mask 563 was formed on the surface of the aluminum film. In this case, since the dense anodic oxide (not shown) is formed on the surface of the aluminum film, the mask 563 can be formed in close contact therewith. Next, the aluminum film was etched using the resist mask 563 to form a gate electrode 562 as shown in FIG.

Furthermore, as shown in FIG. 59A, the gate electrode 562 was anodized while leaving the resist mask 563, to form a porous anodic oxide 564 to a thickness of 4000 angstroms. In this case, since the resist mask 563 is in close contact with the surface of the gate electrode 562, the porous anodic oxide 564 is formed only on the side surface of the gate electrode 562.

Next, as shown in FIG. 59B, after removing the resist mask 563, the gate electrode 562 is anodized again in an electrolytic solution to form a dense anodic oxide 565 to a thickness of 1000 angstroms. did. The anodic oxides 564 and 565 may be separately formed by changing the electrolytic solution used. Among them, when the porous anodic oxide 564 is formed, for example, an acidic solution containing about 3 to 20% by weight of citric acid, oxalic acid, chromic acid or sulfuric acid may be used. A weight percent acidic aqueous solution was used.

On the other hand, when forming a dense anodic oxide 565, for example, an electrolytic solution in which an ethylene glycol solution containing tartaric acid, boric acid, or nitric acid of about 3 to 10% by weight and PH is adjusted to about 7 may be used. Here, an ethylene glycol solution containing 5% by weight of tartaric acid was used after adjusting the pH to 7.

Next, as shown in FIG. 59 (C), the silicon oxide film 561 is etched using the gate electrode 562 and the surrounding porous anodic oxide 564 and dense anodic oxide 565 as a mask to form a gate insulating film. A film 566 was formed. Next, as shown in FIG. 59D, after the porous anodic oxide 564 is removed, the active electrode is formed by ion doping using the gate electrode 562, the dense anodic oxide 565, and the gate insulating film 566 as a mask. An impurity imparting a conductivity type is implanted into the layer 560.

In this example, P (phosphorus) ions were doped using phosphine as a doping gas in order to form an N-channel TFT. At the time of doping, conditions such as a dose amount and an acceleration voltage are controlled so that the gate insulating film 564 functions as a translucent mask. As a result of the above doping, phosphorus (P) ions were implanted at a high concentration in a region not covered with the gate insulating film 564 to form a source region 567 and a drain region 568.

(4) On the other hand, low-concentration P ions were implanted into the region covered only by the gate insulating film 566 to form low-concentration impurity regions 569 and 570. In addition, a channel region 571 was formed because no impurity was implanted into a region immediately below the gate electrode 562. After the doping step, thermal annealing, laser annealing and the like are performed to activate the doped P ions. Here, thermal annealing is applied.

(4) Since the low-concentration impurity regions 569 and 570 function as high-resistance regions, they contribute to a reduction in off-state current. In particular, the low concentration impurity region 570 on the drain 568 side is called an LDD. Further, by making the dense anodic oxide 564 sufficiently thick, an offset structure in which an impurity region is shifted from an end surface of the gate electrode 562 can be obtained, so that off-state current can be further reduced.

Next, as shown in FIG. 59E, a 5000-Å-thick silicon oxide film was formed as the interlayer insulator 572 by a plasma CVD method. Note that as the interlayer insulator 572, a single-layer film of a silicon nitride film or a stacked film of a silicon oxide film and a silicon nitride film may be formed instead of the single-layer film of a silicon oxide film.

Next, the interlayer insulator 572 made of a silicon oxide film is etched by an etching method to form contact holes in each of the source region 567 and the drain region 568, and then an aluminum film is formed to a thickness of 4000 angstroms by a sputtering method. Filmed. This was patterned to form electrodes 573 and 574 in the contact holes of the source region 567 and the drain region 568.

(4) Finally, heat treatment was performed at a temperature of 300 ° C. in a hydrogen atmosphere. Note that this hydrogen plasma treatment is not mainly for passivating defects in the active layer 560, but is mainly for passivation at the interface between the active layer 560 and the electrodes 573 and 574 made of aluminum. Through the above steps, a TFT having an LDD structure was manufactured as shown in FIG.

In the N-channel TFT manufactured according to the manufacturing process of this example, the field-effect mobility after performing the hydrogen plasma treatment was increased only by about 10 to 20% before performing the hydrogen plasma treatment. . This is conventionally although N-channel type TFT is not practical and not the hydrogen plasma treatment, wherein such step of Figure 58 (C), only the thermal oxidation treatment for adding NF _3, crystal grains of the active layer 560 This implies that the field defects are effectively passivated.

<< Example 69 >>
Example 69 is an example in which a CMOS type TFT in which an N-channel type TFT and a P-channel type TFT are complementarily combined is manufactured. FIG. 60 to FIG. 61 are explanatory views of the manufacturing process of the TFT of this embodiment.

First, as shown in FIG. 60A, a base film 576 made of a silicon oxide film having a thickness of 2000 Å was formed over a glass substrate (Corning 1737) 575. Next, an intrinsic (I-type) amorphous silicon film was formed to a thickness of 700 angstroms by a plasma CVD method or a low pressure thermal CVD method. Then, a crystalline silicon film 577 was formed by the method described in Example 67. The amorphous silicon film may be crystallized by an appropriate crystallization method such as the method of Embodiment 68, heat treatment, laser irradiation, and the like, and in these cases, the following steps are the same.

As shown in FIG. 60B, thermal oxidation is performed at a temperature of 600 ° C. for 2 hours in an oxygen atmosphere in which the concentration of NF ₃ is 400 ppm to form a thermal oxide film 578 to a thickness of 200 angstroms. The defects at the crystal grain boundaries of the conductive silicon film 577 were passivated with Si. As a result, the crystalline silicon film 577 becomes suitable as a semiconductor material such as a TFT.

Next, after removing the thermal oxide film 578 using an etchant made of buffered hydrofluoric acid, the crystalline silicon film 577 was patterned into an island shape to form an active layer 579 and an active layer 580, respectively. Further, a silicon oxide film 581 constituting a gate insulating film was deposited to a thickness of 1500 angstroms by a plasma CVD method. Note that the active layer 579 constitutes an N-channel TFT, and the active layer 580 constitutes a P-channel TFT.

(4) Next, an aluminum film constituting the gate electrodes 582 and 583 was deposited to a thickness of 4000 angstroms by sputtering. Scandium was previously contained in the aluminum film at 0.2 wt% to suppress generation of hillocks and whiskers. Next, the aluminum film was anodized in an electrolytic solution to form a dense anodic oxide film 584 of about 100 Å on the surface. Next, a photoresist mask 585 was formed on the surface of the anodic oxide film, and the aluminum film was patterned to form gate electrodes 582 and 583, respectively.

{Circle around (5)} With the photoresist mask 585 still attached, the gate electrodes 582 and 583 were anodized again to form anodic oxides 586 and 587. As the electrolytic solution, for example, an acidic solution containing 3 to 20% by weight of citric acid, oxalic acid, chromic acid or sulfuric acid may be used. In this example, a 4% by weight aqueous solution of oxalic acid was used.

In the state where the photoresist mask 585 and the anodic oxide film 584 exist on the surfaces of the gate electrodes 582 and 583, porous anodic oxides 586 and 587 are formed only on the side surfaces of the gate electrodes 582 and 583. The growth distance of the porous anodic oxides 586, 587 can be controlled by the anodic oxidation treatment time, and the growth distance determines the length of the low concentration impurity region (LDD region). In this example, porous anodic oxides 586 and 587 were grown to a length of 7000 Å.

Next, after removing the photoresist mask 585, the gate electrodes 582 and 583 were anodized again to form dense and strong anodic oxide films 588 and 589 as shown in FIG. 61 (E). In this example, a 3 wt% tartaric acid ethylene glycol solution was neutralized to pH 6.9 with ammonia water and used as the electrolytic solution.

Next, P (phosphorus) ions were implanted into the island-shaped active layers 579 and 580 by ion doping using the gate electrodes 582 and 583 and the porous anodic oxides 586 and 587 as a mask. Phosphine diluted to 1 to 10% by volume with hydrogen was used as a doping gas. The doping is performed at an acceleration voltage of 60 to 90 kV and a dose of 1 × 10 ¹⁴ to 8 × 10 ¹⁵ atoms / cm ^{2. In} this embodiment, the acceleration voltage is 80 kV and the dose is 1 × 10 ^15. Atoms / cm ² .

At this time, phosphorus (P) ions do not pass through the gate electrodes 582 and 583 and the porous anodic oxides 586 and 587, but pass through the gate insulating film 581 and are implanted into the island-shaped silicon 589 and 580. . As a result, N-type impurity regions 590 to 593 are formed as shown in FIG.

Next, as shown in FIGS. 61E to 61F, after removing the dense anodic oxide film 584 with buffered hydrofluoric acid, a porous anodic oxide 586 is mixed with a mixed acid obtained by mixing phosphoric acid, acetic acid and nitric acid. 587 was removed. Since the porous anodic oxides 586 and 587 can be easily removed, the dense and strong anodic oxides 588 and 589 are not etched.

Next, phosphorus ions were again doped. The acceleration voltage is 60 to 90 kV and the dose is 1 × 10 ¹² to 1 × 10 ¹⁴ atoms / cm ^{2. In} this embodiment, the acceleration voltage is 80 kV and the dose is 1 × 10 ¹⁴ atoms / cm ² . did. In this case, phosphorus ions do not pass through the gate electrodes 582 and 583, but pass through the gate insulating film 581 and are implanted into the active layers 579 and 580. Therefore, the region into which phosphorus ions are implanted twice becomes N-type high-concentration impurity regions 594 to 597, and the region into which phosphorus ions are implanted once becomes N-type low-concentration impurity regions 598 to 601.

As shown in FIG. 61 (G), a region to be an N-channel TFT is covered with polyimide or a heat-resistant resist 602. Here, polyimide is used. Thereafter, boron ions were doped in order to invert the conductivity type of the active layer 580 from N-type to P-type. Diborane diluted to about 1 to 10% by volume with hydrogen was used as a doping gas, the acceleration voltage was 80 kV, and the dose of boron was 2 × 10 ¹⁵ atoms / cm ² .

(4) The region covered with the polyimide 602 remains N-type because boron is not implanted. Therefore, in the active layer 579, the high-concentration impurity regions 594 and 595 correspond to the source region and the drain region of the N-channel TFT, respectively, and the region 603 immediately below the gate electrode 582 is not implanted with phosphorus ions and boron ions. It remains intrinsic and corresponds to a TFT channel.

ド ー ピ ン グ In boron ion doping, a large amount of boron is implanted, so that a low-concentration impurity region (LDD region) is not formed, and only P-type high-concentration impurity regions 604 and 605 are formed. The high-concentration impurity regions 604 and 605 correspond to a source region and a drain region of a P-channel TFT, respectively. Further, the region 606 immediately below the gate electrode 583 remains intrinsic since phosphorus ions and boron ions are not implanted, and serves as a channel of the TFT.

Next, the resist 602 was removed, and as shown in FIG. 61H, a silicon oxide film having a thickness of 1 μm was formed as an interlayer insulating film 607 by a plasma CVD method, and a contact hole was formed therein. In this contact hole, electrodes and wirings 608 to 610 in the source region and the drain region were formed with a multilayer film of titanium and aluminum. Finally, a heat treatment was performed for 2 hours in a hydrogen atmosphere at a temperature of 350 ° C. Through the above steps, a CMOS thin film transistor was completed.

In this embodiment, since a CMOS structure is formed in which an N-type TFT and a P-type transistor are complementarily combined, power consumption can be reduced when driving the TFT. Further, since the low-concentration impurity region 599 is provided between the channel 603 and the drain region 595 of the N-channel TFT, generation of a high electric field between the channel 603 and the drain 595 can be prevented.

The conditions of the thermal oxidation step to which NF ₃ is added are not limited to those described in Examples 67 to 69, and the distortion or deformation of the substrate on which the TFT formed in the thermal oxidation step is formed is within an allowable range. In order to achieve this, the glass substrate is heated at a temperature equal to or lower than the strain point for several hours, and the concentration of NF ₃ in an oxygen atmosphere is determined so that a thermal oxide film grows to a thickness of several hundred angstroms. Just fine. In addition, when a substrate having high heat resistance such as a quartz substrate is used, the process is performed under higher temperature conditions.

Further, in Examples 67 to 69, since the Corning 1737 glass having a strain point of 667 ° C. was used for the glass substrate, the heating temperature in the thermal oxidation step was set to 600 ° C., for example, the strain point was 593 ° C. When glass is used, the heating temperature in the thermal oxidation step is preferably set to about 500 to 550 ° C.

《Applications》
INDUSTRIAL APPLICABILITY The semiconductor device of the present invention is applied to display devices of various electric appliances and various integrated circuits, or to circuits that replace conventional IC circuits. 62 to 63 illustrate some of them. FIG. 62A shows a portable information terminal, and FIG. 62B shows an HMD (head-mounted display) used for viewing images from an endoscope, for training a car, or for simulating a crane. FIG. 62C shows a car navigation system. FIG. 61D illustrates a mobile phone, FIG. 63E illustrates a video camera, and FIG. 61F illustrates a projection. The semiconductor device of the present invention is not limited to these, but is used for display devices of various kinds of electric equipment, for circuits replacing conventional IC circuits, for various integrated circuits, and the like.

FIG. 3 is a view showing a microstructure of a crystalline silicon film obtained by the present invention (optical micrograph: 450 times). FIG. 3 is a view showing a microstructure of a crystalline silicon film obtained by the present invention (optical micrograph: 450 times). FIG. 3 is a view showing a microstructure of a crystalline silicon film obtained by the present invention (TEM: 50,000 times). FIG. 2 is a view showing a microstructure of a crystalline silicon film obtained by the present invention (TEM: 250,000 times). FIG. 4 is a view showing an example of a typical mode of a manufacturing process of a crystalline silicon film according to the present invention. FIG. 4 is a view showing an example of a typical mode of a manufacturing process of a semiconductor device using a crystalline silicon film according to the present invention. The figure which showed typically the form of the crystal growth assumed based on the result observed from many micrographs about the crystalline silicon film which concerns on this invention. FIG. 4 is a schematic diagram for explaining a sub-threshold characteristic (S value) and the like of a semiconductor device. FIG. 4 is a graph showing various characteristics such as a subthreshold characteristic (S value) of a semiconductor device using a crystalline silicon film according to the present invention. FIG. 4 is a graph showing various characteristics such as a subthreshold characteristic (S value) of a semiconductor device using a crystalline silicon film according to the present invention. FIG. 4 is a graph showing various characteristics such as a subthreshold characteristic (S value) of a semiconductor device using a crystalline silicon film according to the present invention. FIG. 9 is a schematic diagram for explaining characteristics of a ring oscillator in which a circuit in which an N-channel TFT and a P-channel TFT are combined is described. FIG. 3 is a diagram illustrating an oscilloscope (oscillation waveform) using a ring oscillator in which a circuit in which an N-channel TFT and a P-channel TFT are combined using a crystalline silicon film according to the present invention; FIG. 4 is a diagram showing measured values of gate current values of a planar thin film transistor using a crystalline silicon film according to the present invention. FIG. 4 is a diagram showing measured values of gate current values of a planar thin film transistor using a crystalline silicon film according to the present invention. The figure which shows the result of having measured the density | concentration distribution of the Ni element in the film cross section direction at the time of forming a thermal oxide film after crystallizing an amorphous silicon film using Ni. The figure which shows the result of having measured the density | concentration distribution of the Ni element in the film cross section direction at the time of forming a thermal oxide film after crystallizing an amorphous silicon film using Ni. The figure which shows the result of having measured Cl concentration distribution in the film cross-section direction at the time of forming a thermal oxide film after crystallizing an amorphous silicon film using Ni. The figure which shows the result of having measured the density | concentration distribution of the Ni element in the film cross section direction at the time of forming a thermal oxide film after crystallizing an amorphous silicon film using Ni. The figure which shows the result of having measured the density | concentration distribution of Ni element in the film cross-section direction at the time of forming a thermal oxide film after crystallizing an amorphous silicon film using Ni. The figure which shows the result of having measured Cl concentration distribution in the film cross section direction at the time of forming a thermal oxide film after crystallizing an amorphous silicon film using Ni. FIG. 14 is a view showing a manufacturing process in Example 4. FIG. 19 is a diagram showing a manufacturing process in Example 9. FIG. 14 is a view showing a manufacturing process in Example 10. FIG. 14 is a diagram showing a manufacturing process in Example 12. FIG. 21 is a diagram showing a manufacturing process in Example 13. FIG. 21 is a diagram showing a manufacturing process in Example 16. 21A to 21C illustrate a manufacturing process in Example 21. 22A to 22C illustrate a manufacturing process in Example 22. 24A to 24C illustrate a manufacturing process in Example 24. 26A and 26B show a manufacturing step in Example 25. 30A to 30C illustrate a manufacturing process in Example 28. 30A and 30B illustrate a manufacturing process in Example 30. FIG. 32 is a view showing a manufacturing step in Example 31; FIG. 37 shows a manufacturing step in Example 33. 35A to 35C are diagrams illustrating manufacturing steps in Example 34. 37A and 37B illustrate a manufacturing process in Example 37. FIG. 4 is a schematic diagram illustrating a phenomenon when a crystalline silicon film surface is irradiated with a laser beam. 37A to 37C illustrate a manufacturing process in Example 39. FIG. 42 shows a manufacturing process in Example 41. FIG. 42 is a view showing a manufacturing step in Example 42; 37A and 37B show a manufacturing process in Example 44. 38A to 38F illustrate a manufacturing process in Example 45. 49A and 51B illustrate a manufacturing process in Example 48. 37A and 37B illustrate a manufacturing process in Example 50. 37A and 37B illustrate a manufacturing process in Example 52. 37A and 37B illustrate a manufacturing process in Example 53. 37A and 37B illustrate a manufacturing process in Example 54. 37A and 37B illustrate a manufacturing process in Example 55. 38A and 38B illustrate a manufacturing process in Example 58. 37A and 37B illustrate a manufacturing process in Example 60. 37A and 37B illustrate a manufacturing process in Example 61. 37A and 37B illustrate a manufacturing process in Example 62. 37A and 37B illustrate a manufacturing process in Example 63. 37A and 37B illustrate a manufacturing process in Example 66. 37A and 37B illustrate a manufacturing process in Example 67. 37A and 37B illustrate a manufacturing process in Example 67. FIG. 37 shows a manufacturing step in Example 68. FIG. 37 shows a manufacturing step in Example 68. 37A and 37B illustrate a manufacturing process in Example 69. 37A and 37B illustrate a manufacturing process in Example 69. FIG. 14 is a diagram showing some examples of various application examples of the semiconductor device of the present invention. FIG. 14 is a diagram showing some examples of various application examples of the semiconductor device of the present invention.

Explanation of reference numerals

1, 8, 20, 39, 57: glass substrate, quartz substrate, etc. 2, 9, 21, 40, 58: base film (silicon oxide film, silicon oxynitride film, etc.)
3, 10, 86, 93, 104: amorphous silicon film 4, 13, 87, 96, 170: water film of a solution containing nickel salt or the like 5, 15, 88, 98, 171,...・ Crystalline silicon film 6, 16, 89, 99, 172... Thermal oxide film (metal element contained in the film at high concentration)
7, 15, 90, 98, 173... Crystalline silicon film with reduced or removed metal element concentration 17, 22, 41, 59, 60... Reduced or removed metal element concentration and patterned Crystalline silicon film 11, 94, 177, 271 mask 12, 95, 178, 272 opening 17, 26 pattern 27 anodic oxide film 29 silicon oxide film 28 anodic oxide film 30 source region 31 Channel formation region 32 channel region 33 LDD region 34 drain region 35, 201 interlayer insulating film 36 source electrode 37 drain electrode

Claims (60)

A metal element for promoting crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to form a crystalline silicon film;
A second heat treatment is performed in an oxidizing atmosphere containing a halogen element to form a thermal oxide film on the surface of the crystalline silicon film, and to remove or reduce the metal element present in the crystalline silicon film. ,
Removing the thermal oxide film,
A method for manufacturing a semiconductor device, comprising forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed. A metal element for promoting crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to form a crystalline silicon film;
A second heat treatment is performed in an oxidizing atmosphere containing a halogen element, a thermal oxide film is formed on the surface of the crystalline silicon film, and the thermal oxide film is gettered with the metal element to obtain the crystalline oxide film. Removing or reducing the metal element present in the silicon film,
Removing the thermal oxide film,
A method for manufacturing a semiconductor device, comprising forming a thermal oxide film by thermal oxidation again on the surface of the region from which the thermal oxide film has been removed. A metal element for promoting crystallization of silicon is intentionally introduced into the amorphous silicon film, and the amorphous silicon film is crystallized by a first heat treatment to form a crystalline silicon film;
A second heat treatment is performed in an oxidizing atmosphere containing a halogen element to form a thermal oxide film on the surface of the crystalline silicon film, and to remove or reduce the metal element present in the crystalline silicon film. ,
Removing the thermal oxide film,
Patterning the crystalline silicon film to form an active layer of a thin film transistor,
A method for manufacturing a semiconductor device, comprising: forming a thermal oxide film constituting at least a part of a gate insulating film of the thin film transistor on a surface of the active layer by thermal oxidation. Selectively introducing a metal element that promotes crystallization of silicon into the amorphous silicon film,
Crystal growth is performed in a direction parallel to the film from the region where the metal element is selectively introduced by the first heat treatment;
Performing a second heat treatment in an oxidizing atmosphere containing a halogen element to form a thermal oxide film on the surface of the region where the crystal growth has been performed;
Removing the thermal oxide film,
A method for manufacturing a semiconductor device, comprising forming an active layer of a semiconductor device using a region from which the thermal oxide film has been removed. The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, wherein a crystal in a crystalline silicon film obtained by crystallizing the amorphous silicon film is a crystal in which a crystal lattice is continuously connected. The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, wherein a crystal in a crystalline silicon film obtained by crystallizing the amorphous silicon film is a thin rod-shaped crystal or a thin flat rod-shaped crystal. The method for manufacturing a semiconductor device according to claim 1, wherein
The crystal in the crystalline silicon film obtained by crystallizing the amorphous silicon film is a thin rod-shaped crystal or a thin flat rod-shaped crystal, and these are crystals grown in parallel or almost in parallel at intervals. A method for manufacturing a semiconductor device. The method for manufacturing a semiconductor device according to claim 1, wherein
The metal element that promotes the crystallization of silicon is one or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au. A method for manufacturing a semiconductor device. The method for manufacturing a semiconductor device according to claim 1, wherein
The oxidizing atmosphere containing the halogen element is characterized in that one or more gases selected from HCl, HF, HBr, Cl ₂ , F ₂ and Br ₂ are added to an O ₂ atmosphere. Of manufacturing a semiconductor device. The method for manufacturing a semiconductor device according to claim 1, wherein
The oxidizing atmosphere containing the halogen element is obtained by adding one or more kinds of gases selected from HCl, HF, HBr, Cl ₂ , F ₂ and Br ₂ to an atmosphere containing O _2. A method for manufacturing a semiconductor device, comprising: The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, wherein a gas of a hydride of oxygen and a halogen element is added to the oxidizing atmosphere containing the halogen element. The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, wherein the temperature of the second heat treatment is higher than the temperature of the first heat treatment. The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, wherein the temperature of the second heat treatment is in a range of 700 ° C to 1100 ° C. The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, comprising: performing annealing in a plasma atmosphere containing oxygen and hydrogen after removing the thermal oxide film. The method for manufacturing a semiconductor device according to claim 1, wherein
A method for manufacturing a semiconductor device, wherein the concentration of oxygen contained in the amorphous silicon film is 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁹ cm ⁻³ . The method for manufacturing a semiconductor device according to claim 1, wherein
After crystallizing the amorphous silicon film by the first heat treatment to obtain a crystalline silicon film, the crystalline silicon film is irradiated with laser light or strong light. Method for manufacturing the device. A crystalline silicon film sandwiched between the first oxide film and the second oxide film, wherein the crystalline silicon film contains a metal element containing hydrogen and a halogen element and promoting crystallization of silicon; A semiconductor device in which the metal element has a high concentration distribution in the vicinity of an interface between the first oxide film and the second oxide film in the crystalline silicon film. A crystalline silicon film sandwiched between the first oxide film and the second oxide film, wherein the crystalline silicon film contains a metal element containing hydrogen and a halogen element and promoting crystallization of silicon; A semiconductor device in which the metal element has a high concentration distribution in the vicinity of an interface with the first oxide film or the second oxide film in the crystalline silicon film. The semiconductor device according to claim 17, wherein:
A semiconductor device, wherein the crystal in the crystalline silicon film is a crystal in which a crystal lattice is continuously connected. The semiconductor device according to claim 17 or claim 18,
A semiconductor device, wherein the crystal in the crystalline silicon film obtained by crystallizing the amorphous silicon film is a thin rod-shaped crystal or a thin flat rod-shaped crystal. The semiconductor device according to claim 17 or claim 18,
The crystal in the crystalline silicon film obtained by crystallizing the amorphous silicon film is a plurality of thin rod-shaped crystals or thin flat rod-shaped crystals, and these are crystals that are grown in parallel or substantially parallel at intervals. A semiconductor device characterized by the above-mentioned. The semiconductor device according to any one of claims 17 to 21,
A semiconductor device, wherein a halogen element is contained in the first oxide film and in the vicinity of an interface between the first oxide film and the crystalline silicon film with a high concentration distribution. The semiconductor device according to any one of claims 17 to 22, wherein
A semiconductor device, wherein a halogen element is contained in the first oxide film or in the vicinity of an interface between the first oxide film and the crystalline silicon film with a high concentration distribution. The semiconductor device according to any one of claims 17 to 22, wherein
A semiconductor device, wherein a halogen element is contained in the crystalline silicon film in the vicinity of an interface with the second oxide film with a high concentration distribution. The semiconductor device according to any one of claims 17 to 24,
The first oxide film is a silicon oxide film or a silicon oxynitride film formed on a glass substrate or a quartz substrate, the crystalline silicon film forms an active layer of a thin film transistor, and the second oxide film A semiconductor device, which is a silicon oxide film or a silicon oxynitride film that forms a gate insulating film. A base film made of an oxide film, a crystalline silicon film formed on the base film, and a thermal oxide film formed on the crystalline silicon film; A metal element that promotes crystallization, hydrogen and a halogen element are included, and the metal element that promotes crystallization of silicon has a high concentration distribution near an interface between the base film and the thermal oxide film; Has a high concentration distribution in the vicinity of the interface between the base film and the thermal oxide film, and the thermal oxide film forms at least a part of a gate insulating film of the thin film transistor. A base film made of an oxide film, a crystalline silicon film formed on the base film, and a thermal oxide film formed on the crystalline silicon film; A metal element that promotes crystallization, a hydrogen element and a halogen element are included, and the metal element that promotes crystallization of silicon has a high concentration distribution near an interface with the base film or the thermal oxide film; Has a high concentration distribution near the interface with the base film or the thermal oxide film, and the thermal oxide film forms at least a part of a gate insulating film of the thin film transistor. The semiconductor device according to claim 26 or claim 27,
A semiconductor device, wherein the crystal in the crystalline silicon film is a crystal in which a crystal lattice is continuously connected. The semiconductor device according to claim 26 or claim 27,
A semiconductor device, wherein the crystal in the crystalline silicon film obtained by crystallizing the amorphous silicon film is a thin rod-shaped crystal or a thin flat rod-shaped crystal. The semiconductor device according to claim 26 or claim 27,
The crystal in the crystalline silicon film obtained by crystallizing the amorphous silicon film is a plurality of thin rod-shaped crystals or thin flat rod-shaped crystals, and these are crystals that are grown in parallel or substantially parallel at intervals. A semiconductor device characterized by the above-mentioned. The semiconductor device according to any one of claims 26 to 30,
The metal element that promotes the crystallization of silicon is one or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au. Semiconductor device. The semiconductor device according to any one of claims 17 to 31 is any one of an information information terminal, a head-mounted display, a car navigation system, a mobile phone, a video camera, and a projection. Forming an amorphous silicon film,
Contacting and holding a metal element that promotes crystallization of silicon on the surface of the amorphous silicon film;
Performing a first heat treatment to crystallize the amorphous silicon film to form a crystalline silicon film;
Performing a second heat treatment at a temperature of 500 ° C. to 700 ° C. in an atmosphere containing oxygen, hydrogen, and fluorine to form a thermal oxide film on the surface of the crystalline silicon film;
A method for manufacturing a semiconductor device, comprising removing the thermal oxide film. Forming an amorphous silicon film,
Contacting and holding a metal element that promotes crystallization of silicon on the surface of the amorphous silicon film;
Performing a first heat treatment to crystallize the amorphous silicon film to form a crystalline silicon film;
Performing a second heat treatment at a temperature of 500 ° C. to 700 ° C. in an atmosphere containing oxygen, hydrogen, fluorine, and chlorine to form a thermal oxide film on the surface of the crystalline silicon film;
A method for manufacturing a semiconductor device, comprising removing the thermal oxide film. Forming an amorphous silicon film,
Contacting and holding a metal element that promotes crystallization of silicon on the surface of the amorphous silicon film;
Performing a heat treatment to crystallize the amorphous silicon film to form a crystalline silicon film;
Forming a wet oxide film on the surface of the crystalline silicon film in an atmosphere containing fluorine and chlorine;
A method for manufacturing a semiconductor device, comprising removing the wet oxide film. Forming an amorphous silicon film,
Contacting and holding a metal element that promotes crystallization of silicon on the surface of the amorphous silicon film;
Performing a heat treatment to crystallize the amorphous silicon film to form a crystalline silicon film;
Forming a wet oxide film on the surface of the crystalline silicon film in an atmosphere containing fluorine or chlorine;
A method for manufacturing a semiconductor device, comprising removing the wet oxide film. The method for manufacturing a semiconductor device according to any one of claims 33 to 36,
A method for manufacturing a semiconductor device, wherein a crystal in a crystalline silicon film obtained by crystallizing the amorphous silicon film is a crystal in which a crystal lattice is continuously connected. The method for manufacturing a semiconductor device according to any one of claims 33 to 36,
A method for manufacturing a semiconductor device, wherein a crystal in a crystalline silicon film obtained by crystallizing the amorphous silicon film is a thin rod-shaped crystal or a thin flat rod-shaped crystal. The method for manufacturing a semiconductor device according to any one of claims 33 to 36,
The crystal in the crystalline silicon film obtained by crystallizing the amorphous silicon film is a plurality of thin rod-shaped crystals or thin flat rod-shaped crystals, and these are crystals that are grown in parallel or substantially parallel at intervals. A method for manufacturing a semiconductor device, comprising: The method for manufacturing a semiconductor device according to claim 33 or claim 34,
A method for manufacturing a semiconductor device, wherein a concentration of the metal element in the thermal oxide film is higher than a concentration of the metal element in the crystalline silicon film. A method for manufacturing a semiconductor device according to claim 35 or claim 36,
A method for manufacturing a semiconductor device, wherein the concentration of the metal element in the wet oxide film is higher than the concentration of the metal element in the crystalline silicon film. The method for manufacturing a semiconductor device according to claim 33 or claim 34,
A method for manufacturing a semiconductor device, characterized in that hydrogen is contained in an atmosphere in which the second heat treatment is performed at a concentration of 1 vol% or more and less than an explosion limit. The method for manufacturing a semiconductor device according to claim 33 or claim 34,
A method for manufacturing a semiconductor device, wherein the first heat treatment is performed in a reducing atmosphere. The method for manufacturing a semiconductor device according to any one of claims 33 to 36,
The metal element that promotes the crystallization of silicon is one or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au. A method for manufacturing a semiconductor device. The method for manufacturing a semiconductor device according to any one of claims 33 to 36,
A method for manufacturing a semiconductor device, wherein the metal element promoting crystallization of silicon is Ni. The method for manufacturing a semiconductor device according to claim 33 or claim 34,
After crystallizing the amorphous silicon film by the first heat treatment to obtain a crystalline silicon film, the crystalline silicon film is irradiated with laser light or strong light. Method for manufacturing the device. A semiconductor device having a silicon film having crystallinity,
The silicon film contains a metal element which promotes crystallization of silicon at a concentration of 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁸ cm ⁻³ , and a fluorine atom of 1 × 10 ¹⁵ cm ⁻³ to 1 × 10 ^3. A semiconductor device, which is contained at a concentration of ²⁰ cm ^-3 and contains hydrogen atoms at a concentration of 1 × 10 ¹⁷ cm ^-3 to 1 × 10 ²¹ cm ^-3 . The semiconductor device according to claim 47,
A semiconductor device, wherein the crystal in the crystalline silicon film is a crystal in which a crystal lattice is continuously connected. The semiconductor device according to claim 47,
A semiconductor device, wherein the crystal in the crystalline silicon film is a thin rod-shaped crystal or a thin flat rod-shaped crystal. The semiconductor device according to claim 47,
A semiconductor device, wherein the crystal in the crystalline silicon film is a plurality of thin rod-shaped crystals or thin flat rod-shaped crystals, and these are crystals grown in parallel or almost in parallel at intervals. The semiconductor device according to any one of claims 47 to 50,
The metal element that promotes the crystallization of silicon is one or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au. Semiconductor device. The semiconductor device according to any one of claims 47 to 50,
A semiconductor device, wherein the metal element that promotes crystallization of silicon is Ni. The semiconductor device according to any one of claims 47 to 52,
A semiconductor device, wherein the silicon film is formed on an insulating film, and fluorine atoms are present in a high concentration distribution near an interface between the insulating film and the silicon film. Forming an amorphous silicon film,
After introducing a metal element that promotes crystallization of silicon to the surface of the amorphous silicon film, a heat treatment is performed to crystallize the amorphous silicon film to form a crystalline silicon film,
Heating in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film;
Removing the thermal oxide film on the surface of the crystalline silicon film;
A method for manufacturing a semiconductor device, comprising: depositing an insulating film on a surface of the crystalline silicon film. In a method for manufacturing a thin film transistor over a substrate having an insulating surface,
Forming an amorphous silicon film,
After introducing a metal element that promotes crystallization of silicon to the surface of the amorphous silicon film, a heat treatment is performed to crystallize the amorphous silicon film to form a crystalline silicon film,
Heating in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film;
Removing the thermal oxide film on the surface of the crystalline silicon film;
Shaping the crystalline silicon film to form an active layer of a thin film transistor,
Depositing an insulating film on the surface of the active layer, forming a gate insulating film on at least the surface of the channel region;
Forming a gate electrode on the surface of the gate insulating film;
A method for manufacturing a semiconductor device, comprising: implanting impurity ions imparting a conductivity type to the active layer using the gate electrode as a mask to form a source region and a drain region in a self-aligned manner. Forming an amorphous silicon film,
After introducing a metal element that promotes crystallization of silicon to the surface of the amorphous silicon film, a heat treatment is performed to crystallize the amorphous silicon film to form a crystalline silicon film,
Irradiating the crystalline silicon film with laser light or strong light,
Heating in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film;
Removing the thermal oxide film on the surface of the crystalline silicon film;
A method for manufacturing a semiconductor device, comprising: depositing an insulating film on a surface of the crystalline silicon film. In a method for manufacturing a thin film transistor over a substrate having an insulating surface,
Forming an amorphous silicon film,
After introducing a metal element that promotes crystallization of silicon to the surface of the amorphous silicon film, a heat treatment is performed to crystallize the amorphous silicon film to form a crystalline silicon film,
Irradiating the crystalline silicon film with laser light or strong light,
Heating in an oxidizing atmosphere to which a fluorine compound gas is added to grow a thermal oxide film on the surface of the crystalline silicon film;
Removing the thermal oxide film on the surface of the crystalline silicon film;
Shaping the crystalline silicon film to form an active layer of a thin film transistor,
Depositing an insulating film on the surface of the active layer, forming a gate insulating film on at least the surface of the channel region;
Forming a gate electrode on the surface of the gate insulating film;
A method for manufacturing a semiconductor device, comprising: implanting impurity ions imparting a conductivity type to the active layer using the gate electrode as a mask to form a source region and a drain region in a self-aligned manner. The method for manufacturing a semiconductor device according to any one of claims 54 to 57,
A method for manufacturing a semiconductor device, wherein the thermal oxide film has a thickness of 20 to 50 nm. The method for manufacturing a semiconductor device according to any one of claims 54 to 58,
A method for manufacturing a semiconductor device, wherein the metal element that promotes crystallization of silicon is added to the amorphous silicon film at a concentration of 1 × 10 ^{16 to} 5 × 10 ¹⁹ atoms / cm ³ . 60. The method for manufacturing a semiconductor device according to claim 54, wherein
A semiconductor device, wherein the metal element that promotes crystallization of silicon is at least one element selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Cu, and Au. How to make.