JP2005167280A - Semiconductor device, active matrix substrate, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an improved polycrystalline thin-film semiconductor device at relatively low temperature. <P>SOLUTION: A method for manufacturing a semiconductor device for using a semiconductor film formed on a substrate as an active layer comprises a process for depositing an amorphous semiconductor film by using a material gas containing high-order silane while deposition temperature is less than 430°C and a deposition speed is equal to or higher than 0.5 nm/min in a low-pressure chemical vapor phase deposition method, a process for forming a crystalline semiconductor film by crystallizing the amorphous semiconductor film in a solid phase, and a process for melting one portion of the crystalline semiconductor film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for manufacturing a thin film semiconductor device applied to an active matrix liquid crystal display or the like, a thin film semiconductor device, a liquid crystal display device, and an electronic apparatus.

In recent years, with the increase in screen size and resolution of a liquid crystal display (LCD), the driving method has shifted from the simple matrix method to the active matrix method, and a large amount of information can be displayed. The active matrix method enables a liquid crystal display having more than several hundred thousand pixels, and forms a switching transistor for each pixel. As a substrate for various liquid crystal displays, a transparent insulating substrate such as a fused quartz plate or glass that enables a transmissive display is used.

As the active layer of the thin film transistor (TFT), a semiconductor film such as amorphous silicon or polycrystalline silicon is usually used. However, when the drive circuit is integrated with the thin film transistor, polycrystalline silicon having a high operation speed is used. Is advantageous. When a polycrystalline silicon film is used as an active layer, a fused quartz plate is used as a substrate, and a TFT is usually produced by a manufacturing method called a high-temperature process in which the maximum process temperature exceeds 1000 ° C. On the other hand, when an amorphous silicon film is used as an active layer, a normal glass substrate is used.
In order to expand the LCD display screen and reduce the price, it is indispensable to use inexpensive ordinary glass as the insulating substrate.

  However, as described above, the amorphous silicon film has problems such as significantly lower electrical characteristics than the polycrystalline silicon film and a low operation speed. In addition, since the polycrystalline silicon TFT of the high temperature process uses a fused quartz plate, there is a problem that it is difficult to increase the size and cost of the LCD. As a result, there is a strong demand for a technique for producing a thin film semiconductor device having a semiconductor film such as a polycrystalline silicon film as an active layer on a normal glass substrate.

  However, when using a large normal glass substrate that is rich in mass productivity, there is a great restriction that the maximum process temperature is about 570 ° C. or less in order to avoid deformation of the substrate. That is, a technique for forming a thin film transistor capable of operating a liquid crystal display under such restrictions and an active layer of a thin film transistor capable of operating a driving circuit at high speed is desired. These are now called low-temperature process poly-Si TFTs.

A conventional low-temperature process poly-Si TFT is disclosed in Non-Patent Document 1. According to this, first, monosilane (SiH ₄ ) is used as a raw material gas by LPCVD, an amorphous silicon (a-Si) film having a thickness of 50 nm is deposited at a deposition temperature of 550 ° C., and this a-Si film is irradiated with a laser. The a-Si film is modified to a poly-Si film. After buttering the poly-Si film, a SiO ₂ film as a gate insulating film is deposited at a substrate temperature of 100 ° C. by ECR-PECVD. After forming a gate electrode from tantalum (Ta) on the gate insulating film, donor or acceptor impurities are ion-implanted into the silicon film using the gate electrode as a mask to make the source / drain of the transistor self-aligned (self-aligned) Form. At this time, ion implantation uses a mass non-separation type implantation apparatus called ion doping method, and phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) diluted with hydrogen is used as a source gas.

  The activation of the implanted ions is 300 ° C. Thereafter, an interlayer insulating film is deposited, and electrodes and wirings are made of indium tin oxide (ITO) or aluminum (Al), thereby completing the thin film semiconductor device.

SID (Society for Information Display) '93 digest P.I. 387 (1993)

  However, the following problems are inherent in the low-temperature process poly-Si TFT according to the above-described conventional technology, and these are obstructive factors for mass production.

Problem 1). Since the process temperature is as high as 550 ° C., an inexpensive glass cannot be used, resulting in an increase in product price. In addition, distortion due to the weight of the glass itself increases as the size of the glass increases, and the liquid crystal display (LCD) cannot be increased in size.

Problem 2). Appropriate irradiation conditions for uniform laser irradiation over the entire substrate are strict and the application range is narrow. Therefore, crystallization varies from lot to lot and is not uniform, and stable production is not possible.

Problem 3). When a self-aligned TFT in which the source and drain are self-aligned with the gate electrode is activated at an ion doping method and subsequently at a low temperature of about 300 ° C. to 350 ° C., there is a problem that it cannot be activated occasionally. That is, the source / drain resistance becomes several gigaΩ. This problem is more serious when trying to make lightly doped drain (LDD) TFTs, which causes a significant drop in yield.

Problem 4). The low-temperature process poly-Si TFT shows only good transistor characteristics with SiO ₂ produced by ECR-PECVD, but the ECR-PECVD apparatus is difficult to increase the size of the ECR source and is not suitable for increasing the size of the LCD. Also, the throughput is very bad. Therefore, a practical gate oxide film manufacturing apparatus that can be applied to a large substrate and has high mass productivity has not been obtained.

Problem 5). When a semiconductor film such as silicon is formed by melt crystallization such as laser irradiation, partial agglomeration occurs, which causes large fluctuations in the electrical characteristics of the semiconductor film within the substrate, and the semiconductor film surface becomes rough, resulting in a gate / source. The electric withstand voltage between the gate and the drain becomes low.

Problem 6). When inexpensive general-purpose glass or the like is used for the substrate, the base protective film that effectively prevents impurities from entering the semiconductor film from the substrate is not the base protective film of the thin film semiconductor device exhibiting the best electrical characteristics. That is, if the base protective film is thickened to prevent contamination of impurities, the electrical characteristics of the thin film semiconductor device are deteriorated due to stress from the base protective film, or cracks are generated in the thin film semiconductor device.

Problem 7). In the case where a semiconductor film is formed by plasma enhanced chemical vapor deposition (PECVD), cleaning gas components such as fluorine (F) and carbon (C) remain in the film formation chamber after the film formation chamber is cleaned. When the semiconductor film is deposited, it is mixed into the semiconductor film as an impurity. As a result, the amount of mixed impurities differs between the substrates, and an excellent thin film semiconductor device cannot be manufactured stably.

Problem 8). When a semiconductor film is deposited by a low pressure chemical vapor deposition method (LPCVD method), it becomes difficult to achieve both uniformity and deposition rate in the substrate as the deposition temperature decreases. That is, when the deposition temperature is lowered, the deposition rate is lowered. Therefore, when the pressure is increased to compensate for this, the uniformity in the substrate is remarkably deteriorated. This tendency becomes prominent as the substrate becomes larger, and is a major obstacle to mass production of large LCDs.

Problem 9). In addition to variations in substrates, variations in electrical characteristics of thin film semiconductor devices include three types of variations: variations between substrates in the same lot and variations between lots. The thin film semiconductor device of the prior art and its manufacturing method cannot control these three types of variations, and in particular, no consideration has been given to the variation between lots.

Problem 10). When a semiconductor film is formed by PECVD, the adhesion between the semiconductor film and the undercoat protective film is poor, and numerous crater-like holes are generated in the semiconductor film, or the film is peeled off excessively. .

  Accordingly, the present invention aims to solve the above-mentioned problems, and its purpose is to stably manufacture a good thin film semiconductor device by a practical simple means at a process temperature at which a normal large glass substrate can be used. It is to provide a method.

  The thin film semiconductor device of the present invention includes a substrate provided with a base protective film that is an insulating material on at least a part of the substrate surface, and a semiconductor film that is formed on the base protective film of the substrate and forms an active layer of a transistor The base protective film has a surface roughness of 3.0 nm or less in terms of center line average roughness.

  In the thin film semiconductor device of the present invention, the base protective film has a surface roughness of 1.5 nm or less in terms of center line average roughness.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. A first step of forming a semiconductor film on a base protective film having a surface roughness of 1.5 nm or less as a center line average roughness, and melting the semiconductor film And a second step of crystallizing.

The thin film semiconductor device of the present invention includes a substrate provided with a base protective film that is an insulating material on at least a part of the substrate surface, and a semiconductor film that is formed on the base protective film of the substrate and forms an active layer of a transistor And the base protective film is a laminated film in which at least two kinds of different films are laminated, and the uppermost film of the two kinds of different films is silicon oxide ( It is characterized by being a SiO _x , 0 <x ≦ 2) film.

The thin film semiconductor device of the present invention is characterized in that the lower layer of the two different types of films is a silicon nitride (Si ₃ N _x , 0 <x ≦ 4) film. The film thickness of the silicon oxide film is between 100 nm and 500 nm, and the film thickness of the silicon nitride film is between 50 nm and 500 nm. A field effect transistor having a substrate partially provided with a base protective film that is an insulating material, a semiconductor film formed on the base protective film of the substrate, a gate insulating film, and a gate electrode, and the field effect transistor In a thin film semiconductor device having an interlayer insulating film that provides electrical insulation between the wirings, the sum of the thickness of the base protective film, the thickness of the gate insulating film, and the thickness of the interlayer insulating film Is less than 2μm And features.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method of manufacturing a thin film semiconductor device, a film forming step of continuously forming the base protective film and the semiconductor film with a single PECVD apparatus, which adheres to the film forming chamber of the PECVD apparatus A first step of removing the thin film, a second step of forming a passivation film in the film forming chamber, a third step of installing a substrate in the film forming chamber, and forming a base protective film on the substrate And a fourth step of forming a semiconductor film over the base protective film, and a sixth step of taking out the substrate from the film formation chamber.

According to the method of manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of a substrate surface of a substrate having a substrate area (S) of 90000 mm ² or more, and a semiconductor is further formed on the base protective film. In a method of manufacturing a thin film semiconductor device in which a film is formed and the semiconductor film is used as an active layer of a transistor, a plurality of substrates are placed in a film formation chamber of an LPCVD apparatus and the semiconductor film is formed by LPCVD And a step of depositing the semiconductor film under conditions satisfying the relational expression of d ≧ 0.02 × S ^1/2 , where (d (mm)) is the substrate interval in the LPCVD apparatus deposition chamber. Features.

In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film containing silicon is further formed on the base protective film, and the semiconductor film is formed. In a method of manufacturing a thin film semiconductor device as an active layer of a transistor, a semiconductor film is formed by LPCVD using high order silane (Si _n H _{2n + 2,} n is an integer of 2 or more) as a source gas, It is characterized by having a step of forming a semiconductor film under the condition that the higher order silane flow rate (R) per area is 1.13 × 10 ⁻³ sccm / cm ² or more.

The method for manufacturing a thin film semiconductor device of the present invention is characterized in that it includes a step of forming a semiconductor film under a condition that R is 2.27 × 10 ⁻³ sccm / cm ² or more.

In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film containing silicon is further formed on the base protective film, and the semiconductor film is formed. In a method of manufacturing a thin film semiconductor device as an active layer of a transistor, a deposition temperature is less than 450 ° C. and higher order silane (Si _n H _{2n + 2,} n is an integer of 2 or more) is used as at least one kind of source gas. The semiconductor film is formed by LPCVD, and the semiconductor film is formed under the condition that the deposition rate (DR) of the semiconductor film is 0.20 nm / min or more.

  The method for manufacturing a thin film semiconductor device according to the present invention includes a step of forming a semiconductor film under a condition where DR is 0.60 nm / min or more.

  The thin film semiconductor device of the present invention includes a substrate provided with a base protective film that is an insulating material on at least a part of the substrate surface, and a semiconductor film that is formed on the base protective film of the substrate and forms an active layer of a transistor The semiconductor film is a semiconductor film formed by being crystallized after being deposited by LPCVD with a deposition temperature of less than 450 ° C. and having a thickness of 10 nm. The semiconductor film has a thickness of 140 nm or less.

  A method for manufacturing a thin film semiconductor device according to the present invention is a method for manufacturing a thin film semiconductor device in which a semiconductor film is formed at least on the surface of a glass substrate, and the semiconductor film is used as an active layer of a transistor. The semiconductor film is formed by the above method, and at that time, at least two or more kinds of glass substrates having different strain points in the hot wall type vertical LPCVD apparatus are used as a set of two sheets, and the back surfaces are substantially aligned. It is characterized in that it has a film forming step of depositing a semiconductor film in a state where it is placed horizontally and the glass substrate having the larger strain point of the pair of glass substrates is placed on the lower side.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method of manufacturing a thin film semiconductor device, the semiconductor film is formed by a PECVD apparatus, and at that time, a first step of irradiating the base protective film with oxygen plasma, and the base layer continuously without breaking the vacuum And a second step of forming a semiconductor film over the protective film.

  The method for manufacturing a thin film semiconductor device of the present invention is characterized in that the film forming chamber is evacuated between the first step and the second step.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method of manufacturing a thin film semiconductor device, the semiconductor film is formed by a PECVD apparatus, and at that time, a first step of irradiating the base protective film with hydrogen plasma and the base layer continuously without breaking the vacuum And a second step of forming a semiconductor film over the protective film.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the manufacturing method of a thin film semiconductor device, the semiconductor film is formed by a PECVD apparatus, and at that time, the first step of irradiating the base protective film with oxygen plasma, and the base protection continuously without breaking the vacuum A film forming process comprising: a second process of irradiating the film with hydrogen plasma; and a third process of continuously forming a semiconductor film on the base protective film without breaking the vacuum. .

  The method for manufacturing a thin film semiconductor device of the present invention is characterized in that the film forming chamber is evacuated between the first step and the second step.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film soil, and the semiconductor film is used as an active layer of a transistor. In the thin film semiconductor device manufacturing method, the semiconductor film is formed by a PECVD apparatus, and at that time, the first step of forming the semiconductor film on the base protective film soil is continuously performed without breaking the vacuum. And a second step of irradiating the semiconductor film with hydrogen plasma.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film soil, and the semiconductor film is used as an active layer of a transistor. In the method of manufacturing a thin film semiconductor device, the semiconductor film is formed by a PECVD apparatus, and at that time, the first step of forming the semiconductor film on the base protective film is continuously performed without breaking the vacuum. And a second step of irradiating the semiconductor film with oxygen plasma.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method of manufacturing a thin film semiconductor device, the semiconductor film is formed by a PECVD apparatus, and at that time, the first step of forming the semiconductor film on the base protective film is continuously performed without breaking the vacuum. And a second step of irradiating the semiconductor film with hydrogen plasma and a third step of continuously irradiating the semiconductor film with oxygen plasma without breaking the vacuum. .

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method of manufacturing a thin film semiconductor device, a first step of forming a semiconductor film on a base protective film, a second step of removing the oxide film from the surface of the semiconductor film, and immediately after removing the oxide film, And a third step of melt crystallization of the semiconductor film.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method for manufacturing a thin film semiconductor device, a first step of forming a mixed crystal semiconductor film by PECVD under a condition that the deposition rate is about 0.1 nm / s or more, and melting the semiconductor film And a second step of crystallizing.

  In the method of manufacturing a thin film semiconductor device according to the present invention, the first step is a step of forming a mixed crystal semiconductor film under a condition that a deposition rate is about 3.7 nm / s or more.

  In the method for manufacturing a thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on at least a part of the substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is formed as an active layer of a transistor. In the method for manufacturing a thin film semiconductor device, a chemical substance containing a constituent element of the semiconductor film and a chemical substance containing the constituent element of the semiconductor film and an inert gas as a raw material gas and a flow rate of the gas of the inert gas are contained. A first step of forming a mixed crystal semiconductor film by PECVD under a condition where the flow rate ratio of the gas flow is less than 1/33, and a second step of melt crystallization of the semiconductor film. It is characterized by having.

  In the method of manufacturing a thin film semiconductor device of the present invention, a mixed crystal semiconductor film is formed by PECVD under the condition that the first step is performed with the flow rate ratio being between 1/124 and 40.67 / 1. It is a process.

  The thin film semiconductor device of the present invention includes a substrate provided with a base protective film that is an insulating material on at least a part of the substrate surface, and a semiconductor film that is formed on the base protective film of the substrate and forms an active layer of a transistor The semiconductor film is a semiconductor film formed by being crystallized after being formed by PECVD, and is a semiconductor film having a thickness of 9 nm to 135 nm. It is characterized by being.

  The method of manufacturing a thin film semiconductor device according to the present invention is a method for forming a thin film semiconductor device in which a semiconductor film is formed on the insulating material of a substrate having at least a part of the surface being an insulating material, and the semiconductor film serves as an active layer of a transistor In the manufacturing method, a first step of depositing a semiconductor film at a deposition temperature of less than 450 ° C. by low pressure chemical vapor deposition (LPCVD), and a second step of irradiating the semiconductor film with optical energy or electromagnetic energy And the maximum process temperature after the end of the second process is 350 ° C. or lower.

  In the method of manufacturing a thin film semiconductor device according to the present invention, the first step is a step of depositing a semiconductor film at a deposition temperature of 430 ° C. or lower.

  The method of manufacturing a thin film semiconductor device according to the present invention is a method for forming a thin film semiconductor device in which a semiconductor film is formed on the insulating material of a substrate having at least a part of the surface being an insulating material, and the semiconductor film is used as an active layer of a transistor. The manufacturing method includes a first step of forming a semiconductor film at a deposition temperature of 350 ° C. or less, and a second step of irradiating the semiconductor film with optical energy or electromagnetic energy, and the second step The maximum process temperature after the end is 350 ° C. or less.

  The thin film semiconductor device manufacturing method of the present invention is characterized in that the first step is performed by a plasma enhanced chemical vapor deposition method (PECVD method).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the first step is performed by a sputtering method.

  The method of manufacturing a thin film semiconductor device according to the present invention is a method for forming a thin film semiconductor device in which a semiconductor film is formed on the insulating material of a substrate having at least a part of the surface being an insulating material, and the semiconductor film is used as an active layer of a transistor. The manufacturing method includes a first step of forming a semiconductor film by a VHF plasma chemical vapor deposition method (VHF-PECVD method), and a maximum process temperature after the end of the first step is 350 ° C. or less. It is characterized by being.

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that when the semiconductor film is formed in the first step, the thickness of the semiconductor film is between 20 nm and 150 nm.

  In the method of manufacturing a thin film semiconductor device of the present invention, when forming a semiconductor film by the first step, a chemical substance containing a constituent element of the semiconductor film is used as a source gas, and a rare gas group element is used as an additional gas. It is characterized by.

The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the chemical substance containing the constituent element of the semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is helium (He).

The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is neon (Ne).
The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is argon (Ar).

  In the method for manufacturing a thin film semiconductor device of the present invention, a crystalline semiconductor film is formed on the insulating material of a substrate whose surface is at least part of an insulating material, and the crystalline semiconductor film is used as an active layer of a transistor. A method for manufacturing a thin film semiconductor device includes a first step of forming a crystalline semiconductor film by a microwave plasma chemical vapor deposition method (microwave-PECVD method), and the highest step after the first step. The temperature is 350 ° C. or lower.

  The thin film semiconductor device manufacturing method of the present invention is characterized in that when the crystalline semiconductor film is formed in the first step, the thickness of the crystalline semiconductor film is between 20 nm and 150 nm.

  In the method for manufacturing a thin film semiconductor device of the present invention, when the crystalline semiconductor film is formed in the first step, a chemical substance containing a constituent element of the crystalline semiconductor film is used as a source gas, and a rare gas is used as an additional gas. It is characterized by using a group element.

In the method for manufacturing a thin film semiconductor device according to the present invention, the chemical substance containing the constituent element of the crystalline semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is helium (He).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is neon (Ne).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is argon (Ar).

The method for manufacturing a thin film semiconductor device according to the present invention is a method for forming a thin film semiconductor device in which a semiconductor film is formed on the insulating material soil of a substrate having at least a part of the surface being an insulating material, and the semiconductor film is used as an active layer of a transistor. The manufacturing method includes a first step of forming a semiconductor film by a VHF plasma chemical vapor deposition method (VHF-PECVD method), and a second step of crystallizing the semiconductor film. The maximum process temperature after the process is 350 ° C. or less.
The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the thickness of the semiconductor film crystallized in the second step is between 10 nm and 150 nm.

In the method for manufacturing a thin film semiconductor device of the present invention, when forming a semiconductor film in the first step, a chemical substance containing a constituent element of the semiconductor film is used as a source gas, and a rare gas group element is used as an additional gas. It is characterized by that.
The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the chemical substance containing the constituent element of the semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is helium (He).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is neon (Ne).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is argon (Ar).

  In the method for manufacturing a thin film semiconductor device of the present invention, a crystalline semiconductor film is formed on the insulating material of a substrate whose surface is at least part of an insulating material, and the crystalline semiconductor film is used as an active layer of a transistor. A method of manufacturing a thin film semiconductor device includes a first step of forming a semiconductor film by a microwave plasma chemical vapor deposition method (microwave-PECVD method) and a second step of crystallizing the semiconductor film. And the process maximum temperature after this 2nd process is 350 degrees C or less, It is characterized by the above-mentioned.

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the thickness of the semiconductor film crystallized in the second step is between 10 nm and 150 nm.

  In the method for manufacturing a thin film semiconductor device of the present invention, when the crystalline semiconductor film is formed in the first step, a chemical substance containing a constituent element of the crystalline semiconductor film is used as a source gas, and a rare gas is used as an additional gas. It is characterized by using a group element.

In the method for manufacturing a thin film semiconductor device according to the present invention, the chemical substance containing the constituent element of the crystalline semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is helium (He).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is neon (Ne).

  The method for manufacturing a thin film semiconductor device according to the present invention is characterized in that the rare gas group element is argon (Ar).

The basic principle and operation of the present invention will be described with reference to the drawings.
FIG. 1A to FIG. 1D are schematic views showing, in cross section, a manufacturing process of a thin film semiconductor device for forming a MIS field effect transistor. After describing the outline of the manufacturing method of the low-temperature process poly-Si TFT using this figure, the details regarding the present invention will be described for each step.

(1. Outline of thin film semiconductor device manufacturing method of the present invention)
In the present invention, general-purpose non-alkali glass is used as an example of the substrate 101. First, a base protective film 102 that is an insulating material is formed on a substrate 101 by an atmospheric pressure chemical vapor deposition method (APCVD method), a PECVD method, or a sputtering method. Next, a semiconductor film such as an intrinsic silicon film, which will later become an active layer of the thin film semiconductor device, is deposited. The semiconductor film is formed by chemical vapor deposition (CVD) such as LPCVD, PECVD, APCVD, or physical vapor deposition (PVD) such as sputtering or vapor deposition. Crystallization proceeds by irradiating the semiconductor film thus obtained with optical energy such as laser light or electromagnetic energy for a short time. This process is called crystallization if the first deposited semiconductor film is amorphous or a mixed crystal containing both amorphous and microcrystals. On the other hand, if the first deposited semiconductor film is polycrystalline, this process is called recrystallization. In the present specification, unless otherwise specified, both are collectively referred to as crystallization. If the energy intensity of laser light or the like is high, the semiconductor film is once melted during crystallization and crystallized through a cooling and solidifying process. This is referred to as a melt crystallization method in the present application. On the other hand, a method of proceeding in the solid phase without melting the crystallization of the semiconductor film is called a solid phase growth method (SPC method).

  Solid phase growth methods include a heat treatment method (Furnace-SPC method) in which crystallization is performed at a temperature of about 550 ° C. to 650 ° C. over several hours to several tens of hours, and 700 ° C. in a short time of less than one second to about one minute. It is mainly classified into three types: rapid heat treatment method (RTA method) that promotes crystallization at a high temperature of 1000 to 1000 ° C, and extremely short time solid phase growth method (VST-SPC method) that occurs when the energy intensity of laser light or the like is low. Is done. Although any of these crystallization methods can be applied to the present invention, the melt crystallization method, the RTA method, and the VST-SPC method are particularly suitable from the viewpoint of manufacturing a large substrate with high productivity. In these crystallization methods, the irradiation time is very short, and the irradiation region is also local to the entire substrate. Therefore, the entire substrate is not heated during the crystallization of the semiconductor film, and is therefore caused by the heat of the substrate. This is because no deformation or cracking occurs. Thereafter, this semiconductor film is patterned to form a semiconductor film 103 which will later become an active layer of a transistor. (Fig. 1 (a))

After the semiconductor film is formed, the gate insulating film 104 is formed by a CVD method, a PVD method, or the like.
Various manufacturing methods are conceivable for forming the insulating film, but the insulating film forming temperature is preferably 350 ° C. or lower. This is important for preventing thermal degradation of the MOS interface and the gate insulating film. The same applies to all the following steps. All process temperatures after the formation of the gate insulating film must be kept below 350.degree. This is because a high performance thin film semiconductor device can be manufactured easily and stably.

  Subsequently, a thin film to be the gate electrode 105 is deposited by a PVD method or a CVD method. Usually, since the gate electrode and the gate wiring are made of the same material and in the same process, it is desirable that this material has a low electric resistance and is stable to a heat process of about 350 ° C. After depositing a thin film to be a gate electrode, patterning is performed, and subsequently, impurity ion implantation 106 is performed on the semiconductor film to form a source / drain region 107 and a channel region 108. (Fig. 1 (c))

At this time, since the gate electrode is a mask for ion implantation, the channel has a self-aligned structure formed only under the gate electrode. Impurity ion implantation is performed by ion doping using a mass non-separable ion implanter to implant hydride and hydrogen of an implanted impurity element, and ion implantation using a mass separated ion implanter to implant only a desired impurity element. Two types of can be applied. As a source gas for the ion doping method, a hydride of an implanted impurity element such as phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) having a concentration of about 0.1% to 10% diluted in hydrogen is used. In the ion implantation method, only a desired impurity element is implanted, and then hydrogen ions (protons and hydrogen molecular ions) are implanted. As described above, in order to keep the MOS interface and the gate insulating film stable, the substrate temperature at the time of ion implantation must be 350 ° C. or lower regardless of the ion doping method or the ion implantation method. On the other hand, it is desirable that the substrate temperature at the time of ion implantation be 200 ° C. or higher in order to always stably activate the implanted impurities at a low temperature of 350 ° C. or lower.

  In order to reliably activate the impurity ions implanted at a low concentration at a low temperature, such as performing channel dope to adjust the threshold voltage of the transistor or creating an LDD structure, the substrate at the time of ion implantation The temperature needs to be 250 ° C. or higher. When ion implantation is performed in such a state where the substrate temperature is high, recrystallization occurs at the same time as crystal breakage accompanying ion implantation of the semiconductor film, and as a result, it is possible to prevent the ion implantation portion from becoming amorphous. It is. That is, the ion-implanted region remains as crystalline after the implantation, and the implanted ions can be activated even when the subsequent activation temperature is as low as about 350 ° C. or less. When a CMOS TFT is formed, one of NMOS and PMOS is alternately covered with a mask using an appropriate mask material such as polyimide resin, and each ion implantation is performed by the method described above. If the substrate temperature at the time of ion implantation is about 300 ° C. or less, it is possible to use a general-purpose photoresist that is inexpensive and easy to handle as a mask for ion implantation instead of polyimide resin.

  Next, an interlayer insulating film 109 is formed by a CVD method or a PVD method. After the ion implantation and the formation of the interlayer insulating film, heat treatment is performed for several tens of minutes to several hours in an appropriate thermal environment of about 350 ° C. or less to activate the implanted ions and to bake the interlayer insulating film. The heat treatment temperature is preferably about 250 ° C. or higher in order to reliably activate the implanted ions. Further, a temperature of 300 ° C. or higher is preferable for effectively baking the interlayer insulating film. Usually, the gate insulating film and the interlayer insulating film have different film quality. Therefore, when the contact holes are opened in the two insulating films after forming the interlayer insulating film, the etching rate of the insulating films is usually different. Under such conditions, the shape of the contact hole becomes a reverse taper that is wider toward the bottom, or wrinkles are generated, and this causes a so-called poor contact in which electrical continuity cannot be obtained when the electrode is formed. If the interlayer insulating film is effectively baked, the occurrence of such a contact failure can be minimized. After the interlayer insulating film is formed, contact holes are opened on the source / drain, and the source / drain extraction electrodes 110 and wirings are formed by the PVD method, the CVD method, or the like to complete the thin film semiconductor device. (Fig. 1 (d))

(2. Detailed description for each process concerning the method of manufacturing the thin film semiconductor device of the present invention)

(2-1. Substrate to which the present invention is applied and base protective film)
First, a substrate and a base protective film to which the present invention is applied will be described. Substrates to which the present invention can be applied include conductive materials such as metals, ceramic materials such as silicon carbide (SiC), alumina (Al ₂ O ₃ ), and aluminum nitride (AlN), and transparent insulation such as fused quartz and glass. A crystalline insulating material such as a crystalline material, a semiconductor substrate such as a silicon wafer, LSI processing the same, sapphire (trigonal Al ₂ O ₃ crystal), or the like is used. As an inexpensive general-purpose glass substrate, # 7059 glass or # 1737 glass manufactured by Corning Japan Co., Ltd., OA-2 glass manufactured by Nippon Electric Glass Co., Ltd., NA35 glass manufactured by NH Techno Glass Co., Ltd. or the like can be used. Regardless of the type of the substrate, at least a part of the surface of the substrate is made of an insulating material and is deposited on the insulating material. This insulating substance is referred to as a base protective film in the present application. For example, when a fused quartz substrate is used as the substrate, the substrate itself is an insulating material, so that the semiconductor film may be deposited directly on the fused quartz substrate soil. Alternatively, a semiconductor film is formed after an insulating material such as a silicon oxide film (SiO _x : 0 <x ≦ 2) or a silicon nitride film (Si ₃ N _x : 0 <x ≦ 4) is formed as a base protective film on a fused quartz substrate. May be deposited.

  When normal glass is used as the substrate, the semiconductor film may be deposited directly on normal glass, which is an insulating material, but mobile ions such as sodium (Na) contained in the glass are mixed in the semiconductor film. It is preferable to deposit a semiconductor film after forming a base protective film on a glass substrate with an insulating material such as a silicon oxide film or a silicon nitride film. By doing so, the stability of the thin film semiconductor device is increased without changing its operating characteristics with respect to use over a long period of time or use under a high voltage. In the present application, this stability is referred to as transistor reliability. Except when a crystalline insulating material such as sapphire is used as the substrate, the semiconductor film is preferably deposited on the base protective film. When various ceramic substrates are used as the substrate, the base protective film plays a role of preventing the diffusion of the sintering aid material added in the ceramic into the semiconductor portion. Further, when a metal material is used as a substrate, a base protective film is indispensable in order to ensure insulation. Further, in a semiconductor substrate or LSI element, an interlayer insulating film between transistors or wirings serves as a base protective film. No limitation is imposed on the size and shape of the substrate as long as it does not undergo deformation such as expansion and contraction or distortion with respect to the thermal environment during the manufacturing process. That is, it is arbitrary from a disk having a diameter of about 3 inches (76.2 mm) to a rectangular substrate having a size of about 560 mm × 720 mm or more.

For the base protective film, the substrate is first cleaned with pure water, and then a silicon oxide film, an aluminum oxide film, or a tantalum oxide film is formed on the substrate by a CVD method such as an APCVD method, an LPCVD method, or a PECVD method, or a PVD method such as a sputtering method. Or the like, or a nitride film such as a silicon nitride film. The oxide film or nitride film may be formed by first forming a metal film such as a silicon film, aluminum, or tantalum on the substrate and using a thermal or electrical chemical reaction. For example, it is possible to deposit tantalum of about 100 nm by a sputtering method, and then perform thermal oxidation in an oxidizing atmosphere of about 450 ° C. to form a tantalum oxide film of about 200 nm. In the APCVD method, a silicon oxide film can be deposited by using monosilane (SiH ₄ ) or oxygen as a raw material at a substrate temperature of about 250 ° C. to 450 ° C. In the PECVD method or the sputtering method, these base protective films are formed when the substrate temperature is between room temperature and about 400 ° C.

  In the present invention, since the semiconductor film formed on the base protective film functions as an active layer of the transistor and the semiconductor film is formed by crystallization, the properties of the base protective film have a strong influence on the quality of the semiconductor film. First, it is desired that the surface roughness of the undercoat protective film is 3.0 nm or less in terms of centerline average roughness. When a semiconductor film such as silicon is deposited on the base protective film by a CVD method, several nuclei are first generated in the substrate soil in the very initial stage of film formation. While these nuclei are gradually growing, new nuclei are generated on the underlying protective film where no nucleation has yet been observed. These nuclei grow and collide with each other, and eventually form a film. Due to such a film formation mechanism, regardless of whether the deposited film is amorphous or crystalline, all of them are composed of regions corresponding to the nuclei in the initial stage of film formation. Therefore, if the generation density of nuclei is low, the region constituting the deposited film becomes large. If the region constituting the semiconductor film before crystallization is large, the crystal grains constituting the crystallized semiconductor film are also large. When the crystal grains of the semiconductor film are increased, the electrical characteristics such as mobility of a thin film semiconductor device using this as an active layer of a transistor are improved. According to the experiment by the present inventor, if the surface roughness of the base protective film is 3.0 nm or less in terms of the center line average roughness, the generation density of nuclei can be kept low, and as a result, a high performance thin film semiconductor device can be manufactured. It has been found. This is thought to be because unevenness on the surface of the undercoat protective film contributes to nucleation, and the more uneven the surface, the higher the nucleation density. Further, when the semiconductor film is melt crystallized, the surface roughness of the undercoat protective film is preferably 1.5 nm or less in terms of the center line average roughness. When the surface becomes so smooth, the melted semiconductor material such as silicon spreads well on the base protective film. For this reason, crystal grains having a large grain size are likely to grow, and the characteristics of the thin film semiconductor device are rapidly improved. At the same time, local aggregation of the molten material does not occur in the process of melting and solidifying the molten semiconductor material, and the uniformity in the molten region is increased. The scaling rule of LSI seems to be applied to thin film semiconductor devices, and it seems that the miniaturization of elements will progress with the future integration.

  Thus, as the transistor size is further refined from the order of about 1 μm to the order of submicron, how to avoid local aggregation becomes an important issue. When the semiconductor film is formed by melt crystallization, the surface roughness of the base protective film is ideally 1.0 nm or less in terms of the center line average roughness. In this way, a semiconductor film composed of large crystal grains can be obtained as a uniform film without local aggregation.

  Another role of the base protective film is to prevent diffusion of impurity elements from the substrate.

  For this purpose, it is effective to laminate the base protective film with at least two kinds of different films. For example, a tantalum oxide film, a silicon nitride film, and a silicon oxide film are stacked on the substrate from the lower layer. Usually, various types of impurity elements are contained in the substrate, and the diffusion coefficients in these insulating materials are all different. It can easily occur that a certain kind of impurity element diffuses slowly in one layer constituting the base protective film but fast in another layer. Since various impurity elements are contained in the substrate and the film thickness of the undercoat protective film has a predetermined limit as will be described later, the undercoat protective film is laminated with a plurality of different films rather than being composed of one layer. However, the ability of the base protective film to prevent the diffusion of impurities is higher. Various materials are conceivable for the base protective film, but considering that it can be easily formed by a CVD method or the like, the lamination of a silicon nitride film and a silicon oxide film is optimal. Even in the case of such two layers or multiple layers, the uppermost layer of the base protective film is preferably a silicon oxide film. This is because the silicon oxide film minimizes the interface states that inevitably occur at the interface between the base protective film and the semiconductor layer. In particular, when the semiconductor film is a thin film with a thickness of several hundred nm or less so that a depletion layer spreads over the entire film under the operation state of the transistor, it is important to keep this interface state low. Although the optimum semiconductor film thickness of the thin film semiconductor device of the present invention varies somewhat depending on the manufacturing method, it is approximately 150 nm or less. In addition, since the quality of the semiconductor film is high, there are few trap levels at the crystal grain boundaries and crystal defects within the crystal grain boundaries.

For these reasons, a depletion layer spreads over the entire semiconductor film under the operating state of the transistor. If there are many interface states generated at the interface between the base protective film and the semiconductor film, these work substantially the same as donor ions and acceptor ions, so that the depletion layer spreads during channel formation and the threshold value is delayed. Increase the voltage. That is, it becomes a factor that deteriorates the transistor characteristics. The effect on the transistor characteristics of the surface of the underlying protective film appears when the semiconductor film thickness is about 150 nm or less and the substantial impurity concentration in the channel portion (if NMOS, (acceptor ion concentration) − (donor (Ion concentration) + (capture level or crystal defect concentration that works like an acceptor ion), if PMOS, (donor ion concentration)-(acceptor ion concentration) + a trap level that works like a donor ion crystal defect concentration)) if the following order of 1 × 10 ¹⁸ cm ^-3, or the absolute value of the threshold voltage (Vth) is of the following thin film semiconductor device of about 4.5V. In order to further improve the characteristics of the transistor satisfying these conditions, it is essential to adjust the surface of the base protective film. As one of them, a silicon oxide film is preferable as the uppermost layer when the base protective film is a multilayer.

  Now, the thickness of the base protective film needs to be sufficient to prevent the diffusion and mixing of impurity ions from the substrate, and its value is about 100 nm at the minimum. Considering the variation between lots and substrates, the thickness is preferably about 200 nm or more, and if it is 300 nm, the function as a protective film can be sufficiently achieved. When the base protective film also serves as an interlayer insulating film such as a wiring connecting IC elements or wirings between them, the film thickness is usually about 400 nm to 600 nm.

  If the insulating film becomes too thick, cracks due to stress occur in the insulating film, so the maximum film thickness is preferably about 2 μm. Furthermore, if through-but is taken into consideration, the upper limit is about 1 μm. As described above, when the base protective film is composed of a lower silicon nitride film and an upper silicon oxide film, this relationship is the same, and the thinnest is required to be 100 nm in total of 50 nm. In the thin film semiconductor device of the present invention, the gate insulating film is formed by a CVD method or a PVD method of about 350 ° C. or less. At that time, in order to obtain a clean MOS interface, the natural oxide film on the surface of the semiconductor film is once removed immediately before forming the gate insulating film, and then the gate oxide film is formed. In this natural oxide film removing step, not only the natural oxide film on the surface of the semiconductor film but also the silicon oxide film surface where the semiconductor film does not exist and the underlying protective film is exposed is partially removed. In order for the base protective film to function correctly even after the natural oxide film removing step, the film thickness of at least the silicon oxide film forming the base protective film needs to be 100 nm or more. That is, the minimum film thickness of the silicon oxide film is about 100 nm, and the minimum film thickness of the silicon nitride film is about 50 nm. In the case of a thin film of 50 nm or less, the film may not be connected as a film, and voids may be formed in some places.

  In such a case, since the function of the base protective film for preventing the contamination of impurities is lost, at least 50 nm is necessary even when any film is used. As described above, the upper limit value of the film thickness of the silicon nitride film, the silicon oxide film, etc. is about 2 μm. However, if the thickness of the underlying protective film is 300 nm, its function is fully exerted. On the other hand, if it is too thick, cracking due to film stress and deterioration of transistor characteristics occur. The upper limit is approximately 500 nm. When different films are stacked, the stress state varies depending on each film, so there is no problem if each layer is about 500 nm or less.

  In general, a silicon oxide film formed at a deposition temperature of about 350 ° C. or less by a CVD method or a PVD method has a strong stress inside the film. Usually, part of such stress is released by high-temperature heat treatment after film formation. However, in the low temperature process of the present invention, the maximum process temperature after forming the gate insulating film is only about 350 ° C. or less.

  Such a silicon oxide film that can only be subjected to low-temperature heat treatment is difficult to release stress. Therefore, if the silicon oxide film thickness is about 2 μm or more, the substrate is cracked. Further, when the substrate is enlarged to about 300 mm × 300 mm or more, as the substrate is enlarged, stress is more easily accumulated, and cracks are more easily generated. This situation is the same regardless of whether the silicon oxide film is a single layer or multiple layers. When the total film thickness of the silicon oxide film is 2 μm or more, cracks occur according to the film thickness. In the thin film semiconductor device of the present invention, a base protective film that is an insulating material is provided on a part of the substrate surface, and a field effect transistor including a semiconductor film, a gate insulating film, and a gate electrode is formed on the base protective film, Further, an interlayer insulating film is provided to provide electrical insulation between the wirings of the field effect transistor. The uppermost layer of the base protective film is made of at least a silicon oxide film, the MOS interface side of the gate insulating film is also made of a silicon oxide film, and moreover, part of the interlayer insulating film is usually made of a silicon oxide film. Therefore, if the sum of the film thicknesses of these three types of silicon oxide films is 2 μm or less, even a thin film semiconductor device formed on a large substrate by a low temperature process will not crack. Of course, if the sum of the thickness of the base protective film, the thickness of the gate insulating film, and the thickness of the interlayer insulating film is 2 μm or less, cracks can be more reliably prevented.

  As described above for the reason that the uppermost layer of the base protective film is preferably a silicon oxide film, when a high-quality semiconductor thin film is used as an active layer of a transistor as in the thin film semiconductor device of the present invention, the semiconductor film and the base Control of the interface with the protective film is important. In particular, when forming a semiconductor film by melt crystallization, it is desirable that the surface of the base protective film be as clean as possible. If the surface of the base protective film is clean, not only the interface state existing between the base protective film and the semiconductor film is reduced, but also impurities such as dirt are taken into the semiconductor film during the melting process of the semiconductor film. This is because nothing will happen.

  For this purpose, the base protective film and the semiconductor film may be continuously formed with a single film forming apparatus. The base protective film is a silicon nitride film, a silicon oxide film, or a laminate of both, and if the semiconductor film is a silicon film or silicon-germanium film, the base protective film and the semiconductor film can be easily and continuously formed with a single PECVD apparatus. The Considering mass production of thin film semiconductor devices, it is necessary to periodically clean the film forming chambers of these films and remove the thin film adhering to the film forming chambers of the PECVD apparatus. This is because if the thin film continues to adhere to the film forming chamber without cleaning, the film is peeled off, or abnormal fine particles are generated and the yield is significantly reduced.

  On the other hand, when the thin film is removed from the film formation chamber by the cleaning process, the constituent elements of the cleaning gas such as fluorine (F) and carbon (C) always remain in the film formation chamber even though the amount is small. When the semiconductor film is deposited in such a state, residual elements are taken into the semiconductor film as impurities, and the characteristics of the transistor are deteriorated. Moreover, if a number of substrates are processed after the cleaning process and a predetermined number of substrates are processed and then the cleaning process is performed, the amount of impurities incorporated into the substrate immediately after the cleaning process is large, and the amount of impurities incorporated into the substrate immediately before the cleaning process Falls into a situation where there are few. In other words, the amount of impurities mixed between the substrates is different, so that an excellent thin film semiconductor device cannot be stably manufactured. Therefore, in the present invention, this cleaning process is performed as the same series of operations as the previous continuous film forming process. That is, a cleaning process is performed every time one substrate is formed.

First, as a first step, before the substrate is placed in the film formation chamber of the PECVD apparatus, the thin film attached to the film formation chamber during the previous substrate processing is removed. Specifically, cleaning gases such as NF ₃ , CF ₄ , CHF ₃ , CH ₂ F ₂ , and CH ₃ F are used alone, or these cleaning gases and oxygen (O ₂ ), hydrogen (H ₂ ), and ammonia (NH ₃ ). A mixture with a reaction control gas such as helium (He), argon (Ar), or nitrogen (N ₂ ), if necessary, is further appropriately mixed and introduced into the film formation chamber, and plasma is generated. Stand up. By this step, the thin film attached to the film formation chamber is removed. After completion of this cleaning process, the film forming chamber is evacuated once so that residual gas does not remain as much as possible.

In the subsequent second step, a silicon nitride film or a silicon oxide film is deposited in the film forming chamber as a passivation film for the residual impurity element. That is, the impurity element is confined by this passivation film. The passivation film needs to have a film thickness of about 100 nm or more as in the case of the base protective film to prevent contamination with impurities. This passivation film needs to be completely removed every time one substrate is processed. Accordingly, if the thickness is too thick, the cleaning time of the first step and the time of the second step for forming the passivation film become longer and the productivity is lowered. Therefore, the upper limit of the thickness of the passivation film is about 1 μm. When using a silicon nitride film as a passivation film, ammonia (NH ₃ ) and silane (SiH ₄ , Si ₂ H ₆ ...) Are used as source gases, and when using a silicon oxide film, a laughing gas (N ₂ O) is used. ) And silane.

  After the substrate is set in the film forming chamber in the third step, a base protective film is formed on the substrate in the fourth step. The base protective film functions as a base protective film on the substrate, but functions as a second passivation film in the deposition chamber outside the substrate. Since the base protective film alone prevents diffusion of impurities in the base protective film, when combined with the passivation film formed in the second step, it is possible to almost completely prevent impurities from being mixed into the semiconductor film. Become. A semiconductor film is formed in the fifth step without breaking the vacuum continuously in the fourth step, and the substrate is taken out of the film formation chamber in the sixth step, thereby completing one substrate processing operation. Thereafter, the same substrate processing operation is repeated for each substrate. When the base protective film and the semiconductor film are continuously formed in accordance with such a substrate processing operation, the interface between the base protective film and the semiconductor film is cleaned and an excellent thin film semiconductor device is manufactured. Furthermore, the amount of impurities such as fluorine and carbon in the semiconductor film can be kept to a minimum, and even if a very small amount of impurities is mixed, the amount can always be kept the same between the substrates. As a result, an excellent thin film semiconductor device can be manufactured stably and with high productivity.

(2-2. Semiconductor films of the present invention and raw materials for forming them)
In the present invention, a semiconductor film is deposited on some substrate. This is common to all inventions below. As a kind of semiconductor film to which the present invention is applied, in addition to a single semiconductor film such as silicon (Si) or germanium (Ge), silicon / germanium (Si _x Ge _1-x : 0 <x <1) or silicon carbide _{(Si x C 1-x:} 0 <x <1) and germanium carbide _{(Ge x C 1-x:} 0 <x <1) group IV element complex semiconductor film or gallium arsenide of such ( Complex compound semiconductor films of Group 3 and Group 5 elements such as GaAs) and Indium Antimony (InSd), or complex compound semiconductor films of Group 2 and Group 6 elements such as cadmium selenium (CdSe) are also possible. is there. Alternatively, silicon germanium gallium arsenide _{(Si x Ge y Ga z As} z: x + y + z = 1) and said further complex compound semiconductor film or a phosphorus these semiconductor films (P), arsenic (As), antimony ( The present invention also applies to an N-type semiconductor film to which a donor element such as Sb) is added, or a P-type semiconductor film to which an acceptor element such as boron (B), aluminum (Al), gallium (Ga), or indium (In) is added. Applicable.

In the present invention, when a semiconductor film is deposited by the CVD method, the semiconductor film is deposited using a chemical substance containing a constituent element of the deposited semiconductor film as a source gas. For example, when the semiconductor film is silicon (Si), the raw material gas is silane such as monosilane (SiH ₄ ), disilane (Si ₂ H ₆ ), trisilane (Si ₃ H ₈ ), or dichlorosilane (SiH ₂ Cl ₂ ). Is used. In this specification, disilane and trisilane are referred to as higher order silane (Si _n H _{2n + 2,} where n is an integer of 2 or more). When germanium (Ge) is a semiconductor film, germane (GeH ₄ ) or the like is used, and when phosphorus (P) or poron (B) is added to the semiconductor film, phosphine (PH ₃ ) or diborane (B ₂ H ₆ ). Etc. are also used together. As the source gas, chemical substances containing the elements constituting the various semiconductor films described above are used. However, since a part of the source gas always remains in the semiconductor film, a hydride of the constituent element is more preferable. For example, chlorine (Cl) always remains in a silicon film formed from dichlorosilane (SiH ₂ Cl ₂ ) regardless of the amount, and when this silicon film is used as an active layer of a thin film semiconductor device, residual chlorine is not formed. It becomes a factor of deterioration of transistor characteristics. Therefore, monosilane (SiH ₄ ), which is a hydride of the constituent element, is preferable to dichlorosilane.

The higher the purity of the raw material gas and the additional gas added if necessary, the better. However, in consideration of an increase in technical difficulty to obtain a high purity gas and an increase in price, the purity is 99.9999% or more. preferable. In general, a semiconductor film forming apparatus has a background vacuum of about 10 ⁻⁶ torr and a film forming pressure of 0.1 torr to several torr. Therefore, the ratio of impurity contamination from the background vacuum to the film forming process is about 10 ⁻⁵ to 10 ⁻⁶ . It is sufficient that the purity of the source gas and the additional gas used for film formation is equal to the ratio of the film formation pressure to the background vacuum degree of the film formation apparatus using those gases. Therefore, the purity of the gas flowing through the film forming apparatus in the present invention is preferably 99.999% or more (impurity ratio is 1 × 10 ⁻⁵ or less), and 99.9999% (impurity ratio is 1 × 10 ⁻⁶ or less). If so, there is no hindrance to the use as a raw material, and the purity is 10 times the ratio of the background vacuum to the film forming pressure (in this example, the purity is 99.99999% and the impurity ratio is 1 × 10 ⁻⁷ or less). In this case, it is ideal that there is no need to consider the mixing of impurities from the gas.

(2-3, LPCVD apparatus used in the present invention)
An outline of an LPCVD apparatus when a semiconductor film is deposited by the LPCVD method in the present invention will be described. The LPCVD apparatus may be a vertical furnace or a horizontal furnace. In general, the film formation chamber is made of quartz or the like, and a substrate is installed near the center of the film formation chamber. A heater divided into a plurality of zones is installed outside the film formation chamber, and a soaking zone is formed at a desired temperature near the center of the reaction chamber by independently adjusting the heaters.

This is a so-called hot wall type LPCVD apparatus. If a plurality of heaters are adjusted independently, the temperature deviation within the soaking zone can be kept within 0.2 ° C. There is always a small amount of temperature variation in the soaking zone, but this temperature deviation is the first factor of the deposited film thickness variation, and the uniformity within the substrate takes precedence over the uniformity between the substrates. Therefore, it is desirable to install the substrate in parallel with the direction of heat radiation from the heater. For example, if the LPCVD apparatus is a vertical furnace, the semiconductor film can be formed more uniformly when the substrate is installed substantially horizontally than when it is installed vertically. On the other hand, in the case of a horizontal furnace, it is better to install the substrate substantially vertically. A source gas such as silane (SiH ₄ ), disilane (Si ₂ H ₆ ), or germane (GeH ₄ ) and a diluent gas such as helium, nitrogen, argon, and hydrogen used as needed are provided in one of the film forming chambers. After the semiconductor film is deposited on the plurality of substrates installed near the center of the film forming chamber or the wall surface of the film forming chamber, the gas is introduced from the other side opposite to the gas introducing unit. Is done. Exhaust from the film forming chamber is taken by a vacuum exhaust device such as a turbo molecular pump or a rotary pump through a gate valve or a conductance valve. In the present invention, the vacuum evacuation device is composed of a turbo molecular pump and a rotary pump, but a mechanical booster pump, a dry pump, or the like may be combined.

Regardless of whether the furnace is a vertical furnace or a horizontal furnace, the normal direction of the substrate installed in the film forming chamber is substantially the same as the direction of the gas flow in the film forming chamber, so that the uniformity of the semiconductor film can be obtained relatively easily. It becomes like this. That is, in the case of a vertical furnace, the substrate is installed substantially horizontally as described above, so that the gas is preferably flowed in the vertical direction. Similarly, in the case of a horizontal furnace, since the substrate is installed substantially vertically, it is preferable that the gas is flowed in the horizontal direction. The LPCVD apparatus used in the present invention is a high vacuum type, and the background vacuum at the time of film formation is in the 10 ⁻⁷ torr range. For this reason, unnecessary and inevitably degassing from the substrate or boat jig can be exhausted sufficiently quickly. Degassing generated from a substrate, a boat jig or the like includes water (H ₂ O), oxygen (O ₂ ), and the like, and these impurity gases inhibit the growth of a high-quality semiconductor film. That is, the impurity gas generated from the substrate and the boat jig can become a nucleus of the deposited film in the initial deposition process when depositing a semiconductor film such as a silicon film. For this reason, when the degassing is not sufficiently exhausted, many impurity gases are adsorbed on the substrate surface, and many nuclei are generated.

Even if a semiconductor film is deposited and then crystallized by heat treatment, laser irradiation, etc., the presence of a large amount of nuclei due to these degassing reduces the average grain size after crystal growth and degrades semiconductor characteristics. . In addition, since these degas impurities are taken into the grown semiconductor film even during deposition, the semiconductor characteristics are further deteriorated. As explained in the section (2-1), the material and surface roughness of the base protective film play an important role in suppressing the generation of nuclei. At the same time, the deposition conditions of the semiconductor film are carefully controlled. You must. After all, in order to form a high-quality semiconductor film, an LPCVD apparatus capable of exhausting outgassing impurities inevitably generated from the substrate and the like sufficiently fast after adjusting the surface of the base protective film so that nuclei are not easily generated. It is essential to use it.
In the LPCVD method, a semiconductor film is deposited on a substrate by utilizing thermal decomposition of a source gas.

  The biggest problem when film formation is performed with a relatively low deposition temperature and high productivity on a large substrate such as 300 mm × 300 mm by this method is the deposition rate (DR). Uniformity is compatible. For example, consider depositing a silicon film on the above-mentioned inexpensive large-sized general-purpose glass substrate. For a large substrate having a substrate size of 300 mm × 300 mm or more, no matter how the substrate is installed, if the deposition temperature is not less than about 450 ° C., distortion occurs due to the weight of the substrate during film formation. Needless to say, the distortion caused by this heat becomes smaller as the deposition temperature becomes lower, but the distortion becomes so small that it does not affect the subsequent processes such as exposure at the time of patterning when the deposition temperature becomes about 430 ° C. or less. It is. Therefore, a semiconductor film such as a silicon film is deposited using a higher order silane such as disilane at a low temperature such as 425 ° C. However, if the deposition temperature is lowered to this level, the deposition rate becomes very slow. Therefore, the deposition pressure is increased so that a high deposition rate can be obtained even at a low deposition temperature.

  Since the gas concentration is proportional to the pressure, increasing the deposition pressure is equivalent to increasing the raw material gas concentration. Therefore, the transport rate of the raw material to the substrate surface is increased and the deposition rate is increased. However, when such a deposition method is used, only the semiconductor film at the periphery of the large substrate becomes particularly thick, and as a result, the uniformity within the substrate surface is deteriorated. The difference in film thickness between the central portion and the peripheral portion of the substrate becomes more prominent as the substrate becomes larger, and becomes more noticeable as the deposition temperature decreases.

  One reason for this is that when the transport speed of the source gas is increased, turbulence occurs in the edge portion of the substrate, so that a significant amount of source material is transported only to the peripheral portion, and finally compared to the center portion. It is thought that the film becomes thick. Another reason seems to be that the transport speed in the gas phase to the center decreases as the substrate size increases. In other words, in order to obtain a high deposition rate and a uniform film thickness distribution at a low temperature of about 450 ° C. or less than about 430 ° C., the transport rate of the source gas in the gas phase is said to be the central portion or the peripheral portion of the substrate. Regardless of the location, it is always in a large state, and it is important to control the turbulence generated in the edge portion to a minimum. If the source gas partial pressure during deposition (disilane partial pressure if disilane is a source gas) is a vacuum degree of about 10 mtorr to about 5 torr, the difference between the magnitude of turbulent flow and the transport speed is the substrate installed in the LPCVD apparatus. It has become clear from a series of experiments conducted by the inventors that it can be controlled to some extent by the distance d. Inventor's experiments generally found that the larger the substrate distance d, the better the uniformity, and the larger the substrate, the greater the substrate distance needed to obtain the same uniformity. When the distance between the substrates is increased to some extent, the source gas is also effectively transported to the central part of the substrate, the difference in transport amount between the central part and the peripheral part is reduced, and the turbulence generated in the peripheral part is reduced. These two events seem to improve uniformity.

Specifically, when the deposition temperature is about 410 ° C. to about 440 ° C. and the substrate area S is about 90000 mm ² (300 mm × 300 mm substrate) or more, the substrate interval d is set to d ≧ 0.02 × S ^{1 / 2} (mm) ... (1)

If the setting is made so as to satisfy the expression (1), the uniformity is improved. For example, when a 300 mm × 300 mm substrate is installed in the LPCVD apparatus, the substrate distance d may be set to 6 mm or more. An actual deposition temperature of 425 ° C., a disilane flow rate of 200 sccm, a helium flow rate of 1000 sccm, a pressure of 1.2 torr, a disilane partial pressure of 200 mtorr, and a deposition rate of 0.85 nm / min. When installed, the film thickness variation excluding 1 cm around the substrate was only 3.4%. (However, the variation is defined as (max-min) / (max + min) where max is the maximum film thickness and min is the minimum film thickness in a 280 mm × 280 mm area excluding the peripheral part.)
On the other hand, the variation was 8.9% when substrates of the same size were placed in the LPCVD apparatus at exactly 5 mm intervals under exactly the same deposition conditions. As will be described later, the semiconductor film thickness has a strong influence on the performance of the thin film semiconductor device, but if the variation is within about 5%, the difference in performance hardly becomes a problem. Similarly, the variation when a 360 mm × 465 mm substrate was placed in the LPCVD apparatus at intervals of 10 mm was 4.2%, whereas it was 10.1% at a distance of 7.5 mm. According to the formula (1), the substrate interval d should be 8.2 mm or more for a 360 mm × 465 mm substrate, but the fact supports this faithfully. Thus, for example, if the width of the soaking zone is about 120 cm and the interval between the installed substrates is 10 mm, 100 substrates can be processed in one batch even when considering the dummy space above and below the processing substrate. When the film forming method of the present invention described in the next section is used, the processing time per batch is about 3 hours. Therefore, the processing time per substrate (referred to as tact time in the present application) is 1 minute 48 seconds, and the tact time is about 2 minutes even when a stop period such as maintenance of the LPCVD apparatus is taken into account. That is, a thin film semiconductor device having such high productivity and good uniformity is manufactured.

As described above, as the deposition temperature is lowered, the deposition rate becomes slower, and it becomes difficult to obtain uniformity. If the deposition temperature is less than about 410 ° C., instead of (1), d ≧ 0.04 × S ^1/2 (mm) (2)

When the substrate is installed so as to satisfy the condition of formula (2), good uniformity can be obtained. As shown in FIG. 3 (a), when a semiconductor film is formed by setting two substrates as a set using a horizontal furnace and leaning back to back on a boat, the distance between adjacent sets is the substrate spacing d. It corresponds to. Considering the above example of 360 mm × 465 mm, 200 substrates can be processed in one batch, and the productivity is further doubled. A similar relationship applies to a vertical LPCVD apparatus. In this case as well, the back surfaces of the glass substrates are put together in a set substantially horizontally in pairs. That is, of the two glass substrates, the lower substrate has a surface facing downward, and the upper substrate has a surface facing upward.

  Also in such a case, the distance d between the sets corresponds to the above-described substrate interval. (See FIG. 3B) One of the problems that arise when a large substrate is horizontally installed in a hot wall type vertical LPCVD apparatus is the warpage of the central portion of the substrate shown in FIG. This warpage becomes larger as the substrate becomes larger, and becomes larger as the substrate has a lower glass strain point. On the other hand, glass substrates tend to be more expensive as they have higher strain points and higher heat resistance.

Therefore, as shown in FIG. 3B, when a plurality of glass substrates are installed in a LPCVD apparatus as a set of two pieces, a set of glasses having different strain points is used, and the glass substrate having the larger strain point is placed below. A semiconductor film is deposited on the side. Then, since the warp of the glass having a large strain point is small, the warp of the glass having a small strain point provided thereon can also be reduced, and as a result, a cheaper glass substrate can be used. In other words, by making a pair, not only the productivity doubles, but also the price per LCD can be easily reduced.
(2-4, Semiconductor Film Deposition by LPCVD Method According to the Present Invention)
As explained in the previous section, the deposition temperature is preferably as low as possible when using a general-purpose large glass substrate. However, a decrease in the deposition temperature also means a decrease in the deposition rate. When the deposition rate is slowed down, the time spent for film formation becomes long, and it goes without saying that the productivity is lowered, but it also adversely affects the performance of the thin film semiconductor device.

In other words, in manufacturing a good thin film semiconductor device in which silicon is contained in the semiconductor film by a low temperature process, the semiconductor film is deposited at a deposition temperature of less than 450 ° C., particularly about 430 ° C. or less, using a higher order silane such as disilane. When depositing, if the deposition rate is 0.20 nm / min or more, a thin film semiconductor device with high mobility can be obtained, and if the deposition rate is 0.60 nm / min or more, fluctuations in transistor characteristics in the substrate can be reduced. It is. In addition, when a semiconductor film made of a pure silicon film is formed at a low temperature of about 430 ° C. or less and a silicon film deposition rate of about 0.20 nm / min or more, the quality of the melt-crystallized semiconductor film is subject to laser fluctuations. On the other hand, since a poly-Si TFT using this is a thin-film semiconductor device having good transistor characteristics even if an SiO ₂ film formed without using an ECR-PECVD apparatus is used as a gate insulating film, a poly-Si TFT using the same is produced. is there. Actual deposition temperature of 400 ° C., disilane flow rate 200 sccm, helium flow rate 1000 sccm, pressure 880 mtorr, disilane partial pressure 147 mtorr, deposition rate 0.12 nm / min, deposition temperature 425 ° C., disilane flow rate 200 sccm, hydrogen flow rate 200 sccm, pressure 131 mtorr, The amorphous silicon film deposited under conditions of a disilane partial pressure of 65.5 mtorr and a deposition rate of 0.19 nm / min shows black spots everywhere according to transmission electron micrographs, and after crystallization by the RTA method The crystal grain size was also small.

Therefore, when this is used as an active layer of a transistor, the mobility is also reduced. The reason why black spots occur on the amorphous Si when the deposition rate is slower than 0.20 nm / min and degrades the transistor characteristics is not clear, but the growth rate is probably too slow. It seems that the time during which the growth surface is exposed to the gas phase becomes longer, and as a result, the contamination from the background vacuum increases. Therefore, the lower limit of the deposition rate depends on the background vacuum degree of the LPCVD apparatus. That is, in the LPCVD apparatus having a background vacuum degree of 1 × 10 ⁻⁷ torr to 1 × 10 ⁻⁶ torr as in the present application, a high-quality semiconductor film is deposited at a deposition rate of 0.20 nm / min or more. If the deposition rate is 0.60 nm / min or more, such an influence is completely eliminated, and the variation amount of transistor characteristics is also reduced.

  Further, as will be described later, the optimum film thickness of the semiconductor film when the thin film semiconductor device is formed by the LPCVD method of the present invention is about 50 nm. Therefore, if the deposition rate is 0.60 nm / min or more, the deposition time is about 80 minutes. It takes about 20 minutes to put the substrate in the LPCVD apparatus and evacuate it, the preheating time before film formation is about 1 hour, and the deposition time is about 1 hour 20 minutes as described above. It takes about 20 minutes to take out the substrate, and the processing time for one batch is about 3 hours. As shown in the previous section, if 100 substrates are processed in one batch, the tact time is about 2 minutes, and if a method of two sheets is used, extremely high productivity with a tact time of less than 1 minute is realized. The

As described so far, in order to stably produce a high-performance low-temperature process poly-Si TFT on a large substrate, a silicon-containing semiconductor film is deposited at a temperature of about 430 ° C. or less and a deposition rate is set to 0. It is ideally desired that the film thickness variation within a large substrate is about 5% or less at a speed of 6 nm / min or more. This condition is that a high-order silane such as disilane is used as a source gas when forming a semiconductor film by LPCVD, and the total surface area A (cm ² ) on which the semiconductor film can be formed in the LPCVD apparatus film forming chamber This is satisfied by defining the relationship with the flow rate Q (sccm) of the higher order silane introduced into the film formation chamber during film formation. That is, when the higher order silane flow rate per unit area is defined by R (sccm / cm ² ) R = Q / A, the above three ideal conditions are satisfied by adjusting this value. When the semiconductor film is formed by the LPCVD method, the deposition temperature mainly determines the chemical reaction rate on the substrate surface.

On the other hand, the transport speed of the source gas in the gas phase has a positive correlation with the concentration of the source gas in the space. The concentration C of the raw material gas is related to the pressure P and the temperature T _g of the raw material gas by a relational expression of C = P / kT _g . (K is Boltzmann's constant.) In order to increase the deposition rate while fixing the deposition temperature at a constant value, that is, while keeping the potential surface reaction rate constant, the gas P is increased by increasing the gas pressure P. It is common to increase the actual surface reaction rate by increasing the transport rate in the phase. However, as described above, if the pressure is increased to increase the deposition rate, the uniformity is impaired.

  While such a fact is recognized, the pressure P in the film forming chamber has a relationship of P = Q / S between the exhaust speed S of the film forming chamber and the gas flow rate Q. Here, three independent variables are recognized, and since there is one relational expression between them, there are two independent variables after all. In other words, even if only the pressure P is specified, one physical state cannot be determined. This means that, for example, a system with a gas flow rate of 100 sccm and a pumping speed of 1 sccm / mtorr and a system with a gas flow rate of 1 sccm and a pumping speed of 0.01 sccm / mtorr are completely different physical systems even at the same pressure of 100 mtorr. I mean. The inventor pays attention to this point, and after setting the deposition temperature and deposition pressure to constant values, the exhaust rate in the film formation chamber and the flow rate of disilane, which is the raw material gas, are changed. The effect on uniformity was investigated. As a result, it was found that even when the deposition temperature and pressure were kept constant, the deposition rate increased and the uniformity was improved as the flow rate of the source gas was increased.

Further, this relationship is deeply related to the total area A in the reaction chamber, and it was recognized that the raw material gas flow rate should be increased in proportion to the total area. This will be described with reference to FIG. Thirty-five 300 mm × 300 mm substrates were placed in a vertical hot wall LPCVD apparatus having a volume of 184.51 with a substrate spacing of 10 mm, and an amorphous silicon film was deposited. Since the area of one substrate is 30 cm × 30 cm × 2 (front and back) and 1800 cm ² , the total area of 35 substrates is 63000 cm ² .

On the other hand, since the area of the portion where the semiconductor film is formed in the film formation chamber is 25262 cm ² , the total area A where the semiconductor film can be formed in the LPCVD apparatus is A = 63000 + 25262 = 88262 cm ² . Under these conditions, the deposition temperature was 425 ° C., the volume pressure was 320 mtorr, and only disilane was allowed to flow into the film formation chamber to deposit a semiconductor film. The deposition pressure was maintained at a constant value of 320 mtorr by changing the flow rate of disilane from 50 sccm to 400 sccm and simultaneously changing the exhaust speed of the film forming chamber by the pressure regulator of the LPCVD apparatus. The deposition rate with respect to the disilane flow rate in the experiment conducted in this way is indicated by a circle and a solid line (DR) in FIG. 5, and the variation in the film thickness in the substrate is indicated by a square mark and a broken line (V). Since at A = 88262cm ^2, Q = 50sccm is R = 5.66 corresponds to a ^{× 10 -4 sccm / cm 2,} Q = 100sccm within ^{R = 1.13 × 10 -3 sccm /} cm 2 or less, Q = 200 sccm corresponds to R = 2.27 × 10 ⁻³ sccm / cm ² , and Q = 400 sccm corresponds to 4.53 × 10 ⁻³ sccm / cm ² .
When R is greater than 2.27 × 10 ⁻³ , the deposition rate is substantially saturated, and the surface reaction rate approximately matches the potential surface reaction rate. As described above, if the temperature and pressure are the same, a higher deposition rate is desirable from the viewpoint of productivity and semiconductor film quality. If the deposition rate is high, the growth rate increases with respect to the nucleus generation rate, so that the crystal grains after the crystallization process also increase, and the amount of impurity gas such as degassing incorporated into the semiconductor film decreases. These two points improve the semiconductor film quality. These two points mean that when this semiconductor film is used as an active layer of a thin film semiconductor device, the mobility increases and the threshold voltage decreases. Further, the small amount of impurities taken in leads to the low off current of the poly-Si TFT.

Thus, it is better that the deposition rate is high, but the value is saturated at R = 2.27 × 10 ⁻³ sccm / cm ² or more as can be seen from FIG. Accordingly, the flow rate of the higher order silane per unit area during the formation of the semiconductor film is preferably about 2.27 × 10 ⁻³ sccm / cm ² or more. This experiment was conducted in a vertical furnace, and the source gas was introduced from the upper part of the film forming chamber and exhausted from the lower part. At R = 5.66 × 10 ⁻⁴ sccm / cm ² , the deposition rate was 18% different between the substrate placed at the top and the substrate placed at the bottom. This deviation was hardly observed when R = 1.13 × 10 ⁻³ sccm / cm ² or more. Therefore, R is 1.13 × 10 ⁻³ sccm / cm ^{2 in} order to obtain uniformity between substrates. More than the degree is desired. Further, as can be seen from FIG. 5, when R ≧ 4.54 × 10 ⁻³ sccm / cm ² , the variation in the substrate is 5% or less and the deposition rate is 1.30 nm / min, which is ideal.

The flow rate of the source gas must be changed in accordance with the total area A where the semiconductor film can be formed in the LPCVD apparatus. That is, the parameter to be adjusted is the higher order silane flow rate R per unit area. In fact, 17 substrates of 235 mm × 235 mm were placed in the LPCVD apparatus at intervals of 20 mm, and the same experiment as described above was performed. The total area of the substrate is 23.5 cm × 23.5 cm × 2 × 17 = 18777 cm ² , and the area of the portion where the semiconductor film is formed in the film formation chamber is 25262 cm ² , so the total area A = 44039 cm ² and R = 5.66 × 10 ⁻⁴ sccm / cm ² , 1.13 × 10 ⁻³ sccm / cm ² , 2.27 × 10 ⁻³ sccm / cm ² , 4.53 × 10 ⁻³ sccm / cm ² The higher order silane flow rates are 25 sccm, 50 sccm, 100 sccm, and 199 sccm, respectively. When the deposition rate and the uniformity between the substrates were examined with these disilane flow rates, the same phenomenon as before was confirmed.

That is, the amount of higher-order silane per unit area is a parameter that uniquely determines the physical system in addition to the deposition temperature and pressure. When depositing a semiconductor film containing silicon at a deposition temperature of about 430 ° C. or less and a disilane partial pressure of about 100 mtorr or more, at least R is required to be 1.13 × 10 ⁻³ sccm / cm ² or more according to the above-described invention. . For example, when a semiconductor film is deposited by placing 100 substrates of 400 mm × 500 mm in a cylindrical film formation chamber having a diameter of 900 mm with a substrate interval of 15 mm, the total substrate area is 400,000 cm ² and the film formation chamber area is about 56550 cm ² . A = about 45650 cm ² . Therefore, the minimum required disilane flow rate is R = 1.13 × 10 ⁻³ sccm / cm ² multiplied by A and Q = 518 sccm. Similarly, the minimum disilane flow rate Q required for depositing a semiconductor film by placing 100 substrates of 560 mm × 720 mm in a film formation chamber having a diameter of about 1200 mm at intervals of 25 mm is A to 919500 cm ² R ≧ 1.13 × 10 ^{−. From} about ³ sccm / cm ² to about 1050 sccm.

(2-5, channel thickness and transistor characteristics of poly-Si TFT)
Here, the relationship between the film thickness of the active layer semiconductor constituting the channel film thickness of the poly-Si TFT type thin film semiconductor device and the transistor characteristics will be described. In general, in a thin film semiconductor device, the optimum film thickness of a semiconductor film to be a channel strongly depends on the formation method. This is because the film quality of the semiconductor film varies greatly depending on the film thickness. For example, if the semiconductor film quality does not depend on the film thickness in principle, such as SOS (Silicon On Sapphire) or SOI (Silicon On Insulator), the transistor characteristics are improved as the semiconductor film is thinner. (Here, this principle is called the thin film effect based on the theory of operation.) This is because in a thin semiconductor film, the depletion layer spreads over the entire semiconductor film thickness and an inversion layer is immediately formed on the semiconductor film surface. (Threshold voltage Vth decreases).

On the other hand, in a thin film semiconductor device using a polycrystalline film as a channel, the above-described mechanism becomes more complicated because the semiconductor film quality greatly varies depending on the film thickness. Usually, the film quality of a polycrystalline film deteriorates as the film becomes thinner. Specifically, when comparing a thin film with a thick film, the size of the crystal grains (grains) constituting the thin film becomes smaller, and at the same time, the number of defects in the crystal and the number of traps at the crystal grain boundary also increase. When the crystal grain size is reduced, the mobility of a thin film semiconductor device using the crystal grain is reduced. Furthermore, an increase in the number of defects in the crystal and the number of traps at the grain boundary slows the spread of the depletion layer and substantially increases the threshold voltage Vth. (Here, this principle is called thin film degradation.)
After all, the thin film effect based on the previous behavioral theory is in the process of thin film degradation and competition. If the film quality does not change so much even if the film is thinned (if the deterioration of the thin film is small), the thin film effect based on the operation theory is effective and the transistor characteristics are improved. On the contrary, if the film quality is significantly deteriorated by thinning (if the thin film is greatly deteriorated), the thin film effect based on the operation theory is canceled, and the characteristics are deteriorated as the film is thinned. That is, the transistor characteristics when the film is thinned are both good and bad due to the film thickness dependence of the film quality. The film thickness dependence of the film quality varies depending on the film forming method and also varies depending on the film thickness. Therefore, the optimum film thickness of the semiconductor film is completely different depending on the manufacturing method of the thin film semiconductor device, and the optimum value must be obtained according to each manufacturing method.

(2-6, LPCVD-optimum film thickness of crystallized film)
Here, in the above-described low-temperature process thin film semiconductor device of the present invention, the semiconductor film is formed by crystallization after being deposited by LPCVD at a deposition temperature of less than 450 ° C., ideally about 430 ° C. or less. The optimum semiconductor film thickness of the Si TFT will be described. In the LPCVD method, the film is connected as a film at a temperature lower than 450 ° C. or lower than 430 ° C. when the film thickness is about 10 nm or more. If the film is not connected and floats in the form of an island, the on-characteristics of the semiconductor are very poor because the arrow-carrying film does not connect even after crystallization, whether by melt crystallization or solid phase growth. In other words, thin film degradation is overwhelmingly superior to the thin film effect based on the theory of operation. Therefore, the minimum film thickness of the LPCVD-crystallized film is about 10 nm. When the film thickness is about 20 nm or more, the transistor characteristics of the melt crystallized film begin to improve.

  When a semiconductor film is melt-crystallized, it is crystallized around one nucleus in the cooling and solidification process, and semiconductor atoms around the nucleus are gathered together. Therefore, if it is thinner than about 20 nm, even if it is connected as a film immediately after deposition by the provisional LPCVD method, voids are generated everywhere after melt crystallization, and the transistor characteristics are still not excellent. That is, in the LPCVD-melt crystallized film, the thin film deterioration is dominant when it is 20 nm or less, and the thin film deterioration is gradually reduced, and the thin film effect based on the theory of operation antagonizes the thin film deterioration. It is. This continues until the film thickness is between about 20 nm and about 80 nm, and the transistor characteristics are best at this film thickness.

  When the film thickness is greater than 80 nm, the thin film effect based on the operation theory is superior, and the transistor characteristics gradually deteriorate as the film thickness increases. If the semiconductor film thickness is 30 nm or more, stable production becomes possible. In particular, when high-definition / microfabrication progresses and contact holes opened in interlayer insulating films and gate insulating films are formed by reactive ion etching (RIE), a semiconductor film of about 30 nm or more is in contact between the semiconductor film and the wiring. Defects (contact defects) are significantly reduced. Normally, the sum of the film thickness of the gate insulating film and the interlayer insulating film is about 600 nm, and when the variation in the film thickness within the substrate is ± 10%, which is 20% in total, the difference between the thinnest insulating film and the thickest insulating film is It is about 120 nm. Since the selection ratio of the RIE to the semiconductor film is about 1:10, when the contact hole is opened in the thickest insulating film, the semiconductor film located under the thinnest insulating film is cut by about 10 to 15 nm. Yes.

  This is because, if the semiconductor film thickness is about 30 nm or more, even if about 15 nm of provisional loss is lost at the time of opening a contact hole, the contact resistance is sufficiently low and no contact failure occurs. If the semiconductor film thickness is about 70 nm or less, the entire film is heated uniformly during melt crystallization, such as laser irradiation, and crystallization occurs clearly. If the film is thicker than about 140 nm, only the upper part of the film melts when irradiated with laser light from above, and the amorphous part remains in the lower part, so the transistor characteristics are combined with the thin film effect based on the theory of operation. It will fall violently. That is, the upper limit film thickness of the LPCVD-crystallization method is about 140 nm.

(2-7, Semiconductor Film Deposition by PECVD Method According to the Present Invention)
A method for forming a semiconductor film of a thin film semiconductor device according to the present invention by PECVD will be described. The PECVD apparatus used here is a capacitive coupling type, and plasma is generated between two parallel plate electrodes using industrial rf waves (13.56 MHz). Of the two parallel plate electrodes, the lower parallel plate electrode is at ground potential, and a substrate on which a semiconductor film is to be deposited is placed on this electrode. An rf wave is supplied to the upper parallel plate electrode. In addition, a large number of gas inlets are opened in the upper parallel plate electrode, and the source gas is supplied into the film forming chamber as a uniform laminar flow from the electrode surface. The pressure during film formation is about 0.1 to 5 torr, and the distance between parallel plate electrodes is variable between about 10 mm and about 50 mm.

After providing a base protective film that is an insulating material such as a silicon oxide film on at least a part of the substrate surface, a semiconductor film is formed on the base protective film, and finally this semiconductor film is used as an active layer of a transistor. Manufacturing thin film semiconductor devices. In the case of depositing a semiconductor film by the PECVD method, after the substrate is placed in the film formation chamber of the PECVD apparatus, first, the base protective film is irradiated with oxygen plasma. Oxygen plasma at 35mm about the inter-electrode distance 15mm about about 2.0torr from a pressure of about 1.0 torr, stand at 1 w / cm ² order of rf power density 0.05 w / cm ² approximately. The substrate temperature is about 250 ° C. to 350 ° C., which is the same as that for semiconductor deposition, and the oxygen plasma irradiation time is about 10 seconds to about 1 minute. After the oxygen plasma irradiation, the plasma is once extinguished and the film formation chamber is evacuated for about 10 to 30 seconds. When evacuation is performed for about 15 seconds or more, the degree of vacuum in the film formation chamber becomes about 1 mtorr or less.

  This is performed so that oxygen is not mixed in the semiconductor film during the semiconductor film deposition in the next step. After evacuation, a source gas used for semiconductor film deposition such as silane or hydrogen is continuously supplied for 10 seconds to 2 minutes without generating plasma. At this time, the conditions such as the pressure in the film forming chamber and the flow rate of the source gas are the same as those in the semiconductor film deposition. As a result, the inside of the film formation chamber is completely replaced with oxygen by the source gas, so that oxygen contamination into the semiconductor film can be minimized.

  Further, if this time is set to about 30 seconds or more, the substrate temperature is set to a constant value, and the semiconductor can always be deposited under the same conditions. In the thin film semiconductor device of the present invention, the uppermost layer of the base protective film is made of a silicon oxide film or the like with a slow nucleus generation rate. Since this silicon oxide film is formed by a CVD method or a PVD method, an unreacted pair of Si always exists. Therefore, when a semiconductor film is formed on the base protective film without performing any pretreatment, the unreacted pair becomes a fixed charge in the base protective film. As described above, when the semiconductor film is as thin as about several hundreds of nanometers or less, these fixed charges adversely affect the thin film semiconductor device such as shifting the threshold voltage (Vth). By irradiating the surface of the base protective film with oxygen plasma, the unreacted pair is combined with oxygen atoms, and the fixed charge in the base protective film is drastically reduced.

  That is, even if the semiconductor film is sufficiently thin to improve the semiconductor characteristics, characteristic instability such as Vth fluctuation caused by the base protective film can be eliminated. Furthermore, the oxygen plasma cleans the surface of the underlying protective film by an oxidation reaction (combustion), and further suppresses the nucleation rate in the initial stage of semiconductor film deposition. As a result, the purity of the semiconductor film is increased, the region constituting the deposited film is increased, and the crystal grains constituting the crystallized semiconductor film are also increased. This manifests itself as a decrease in off-state current, a decrease in Vth, a sharp subthreshold / swing, an improvement in switching characteristics, and an increase in mobility in the characteristics of the thin film semiconductor device.

  In addition to oxygen plasma irradiation, hydrogen plasma irradiation is also effective in improving the surface of the underlying protective film. That is, after the substrate on which the semiconductor film is to be deposited is placed in the PECVD apparatus, first, the hydrogen protective plasma on the substrate is irradiated with hydrogen plasma, and the semiconductor film is continuously formed on the base protective film without breaking the vacuum. To do. When the semiconductor film deposition conditions are such that hydrogen is 3000 sccm and monosilane 100 sccm, such as a large amount of hydrogen, and the ratio of hydrogen to silane is more than 10 times, the plasma is cut from hydrogen plasma treatment to semiconductor film formation. It is also possible to perform continuous processing without any problem.

  When the semiconductor film deposition conditions are different from the hydrogen plasma conditions such as argon 7000 sccm and monosilane 100 sccm, all the other process parameters are semiconductor except that the plasma is extinguished once and plasma is not generated after the hydrogen plasma treatment. It is preferable to provide a stable period before deposition in the same manner as the film deposition conditions. This is because the substrate temperature is always constant when the semiconductor film is deposited. The hydrogen plasma treatment time is about 10 seconds to about 1 minute, and the stable period before the semiconductor film deposition is about 10 seconds to about 2 minutes.

  There are unreacted pairs in the undercoat protective film that are terminated with oxygen, such as Si- *, and those that cannot be terminated with oxygen, such as Si-O- *. Since the hydrogen plasma irradiation can terminate these unreacted pairs in the form of Si—H and Si—OH, it is very effective to reduce the fixed charge in the base protective film. In addition, since the hydrogen plasma treatment has an effect of cleaning the surface of the base protective film to be cleaned, the purity of the semiconductor film is also increased. Furthermore, this cleaning significantly improves the adhesion between the base protective film and the semiconductor film. When a semiconductor film is formed by PECVD, crater-like holes may be generated in the semiconductor film or the film may be peeled off depending on the deposition conditions. However, these generations can be avoided by hydrogen plasma treatment.

  It is even more preferable to perform both oxygen plasma treatment and hydrogen plasma treatment when depositing the semiconductor film. That is, first, an oxygen plasma is irradiated to the base protective film whose surface is a silicon oxide film. First, an unreacted pair in the undercoat protective film is terminated by an oxidation reaction, and at the same time, the surface is cleaned by thermal baking to suppress the generation rate of nuclei. Next, the oxygen plasma is turned off, and vacuuming is performed for about 10 seconds to 1 minute to remove oxygen in the film formation chamber. Further, hydrogen plasma is irradiated to the base protective film continuously without breaking the vacuum. Some of the end reaction pairs that could not be terminated by oxygen plasma are terminated by hydrogen, and the fixed charge in the underlying protective film is minimized. In addition, the surface is further cleaned, and at the same time, the adhesion between the semiconductor film and the base protective film is also improved. After the hydrogen plasma treatment, evacuation or substrate heating is performed as necessary, and a semiconductor film is continuously formed on the base protective film without breaking the vacuum.

  In this way, not only can both the oxygen plasma effect and the hydrogen plasma effect be obtained, but also hydrogen plasma enters between the oxygen plasma and the semiconductor film formation, so the amount of oxygen mixed into the semiconductor film is also clearly reduced. A high-purity and high-quality semiconductor film can be obtained. Since the semiconductor film melt-crystallized as described in the section (2-1) is particularly important to control the clean undercoat protective film surface and the undercoat protective film-semiconductor interface, the undercoat protective film surface before the semiconductor film is deposited. Processing has a particularly important meaning.

  Next, a processing method after forming the semiconductor film by PECVD will be described. After the semiconductor film is formed on the base protective film, it is preferable to continuously irradiate the semiconductor film with hydrogen plasma without breaking the vacuum. This is because unreacted pairs of semiconductor atoms such as silicon are terminated. This is especially effective when the semiconductor film is deposited with a small amount of hydrogen. For example, the semiconductor film is particularly effective in a system in which the amount of hydrogen is less than 50% of the gas introduced into the film formation chamber, such as depositing a semiconductor film by mixing monosilane with an inert gas such as helium or argon.

  When a semiconductor film is deposited in such a system, a tremendous amount of unreacted pairs always appear in the film. Since these unreacted pairs are chemically very active, they react with various impurity elements and substances existing in the atmosphere or physically adsorb. When crystallization is performed by laser irradiation or the like in such a state, the purity of the semiconductor film is lowered, and furthermore, the adsorbed substance becomes a nucleus of crystal growth, so that the crystal grains are reduced. Such disadvantages can be easily removed by hydrogen plasma treatment. That is, a high-purity and high-quality semiconductor film itself is an unstable substance that is polluted by the atmosphere, but a high-purity and high-quality film is stabilized by hydrogen plasma irradiation after film formation.

  A similar effect can also be achieved by depositing a semiconductor film on the base protective film and then continuously irradiating the semiconductor film with oxygen plasma without breaking the vacuum. When the semiconductor film is silicon or mainly composed of silicon, oxygen plasma forms a silicon oxide film on the surface of the semiconductor film. This oxide film is very stable and has an excellent ability to prevent chemical / physical impurity adsorption and impurity diffusion into the semiconductor film as compared to the semiconductor surface. That is, it is optimal for protecting the semiconductor film from external contamination. Moreover, unlike oxygen in the atmosphere, the oxide film itself is high in purity because it is oxidized by oxygen plasma whose quality is adjusted to high purity. When the crystallization is performed later, it is preferable that the oxide film is removed. However, even if the oxide film is not removed, the contamination of impurities from the oxide film into the semiconductor film hardly poses a problem.

  Ideally, after depositing a semiconductor film with a PECVD apparatus, hydrogen plasma is continuously irradiated without breaking the vacuum, and unreacted pairs terminated by hydrogenation are first inactivated. After that, oxygen plasma is continuously irradiated to the semiconductor film without breaking the vacuum, and unreacted pairs that could not be terminated with hydrogen are terminated with oxygen, and the semiconductor film is protected from external contamination on the surface of the semiconductor film. It is desirable to form a pure silicon oxide film. With this treatment method, not only can both the hydrogen plasma effect and the oxygen plasma effect be obtained, but also the termination effect of unreacted pairs can be increased, and the amount of oxygen taken into the semiconductor film can also be reduced. As a result, the purity of the semiconductor film after crystallization becomes higher than the treatment of oxygen plasma alone, and a better thin film semiconductor device is formed.

  As described in the stage of oxygen plasma irradiation, the oxide film is present on the surface of the semiconductor film, even if careful attention is paid so that the semiconductor film has high purity regardless of the LPCVD method or PECVD method. Sometimes, if these oxygens are taken into the semiconductor film, the quality of the crystallized film will deteriorate. This situation is particularly serious in melt crystallization such as laser irradiation. Similar attention must be paid to crystallization of a semiconductor film which has been devised to form a high-quality semiconductor film by surface adjustment of the underlying protective film, LPCVD method or PECVD method as in the present invention. That is, when the semiconductor film constituting the active layer of the thin film semiconductor device is formed by melt crystallization such as laser irradiation, it is preferable to remove the oxide film on the surface of the semiconductor film immediately before the melt crystallization. By doing so, the amount of oxygen taken into the semiconductor film constituting the oxide film during melting of the semiconductor film can be minimized. When the amount of oxygen taken into the semiconductor film is reduced, not only the crystallinity of the crystallized film is increased, but also the defect density is reduced and the transistor characteristics are remarkably improved.

The treatment method that can most easily remove the oxide film immediately before the crystallization step is a method using a hydrofluoric acid aqueous solution. Of course, the oxide film may be removed by vapor phase plasma processing such as using NF ₃ plasma. It is preferable to crystallize the semiconductor film immediately after removing the oxide film. If the semiconductor film is melted and crystallized within about 2 hours after the completion of the removal step, the amount of oxygen taken into the semiconductor film becomes extremely small.

(2-8, melt crystallization of mixed crystal semiconductor film)
The thin film semiconductor device of the present invention is most effective for poly-Si TFTs having an upper gate structure, and this thin film semiconductor device is manufactured at a temperature of about 350 ° C. or lower in all steps after the formation of the gate insulating film. . Therefore, if the semiconductor film forming step can be performed at a temperature of about 350 ° C. or lower, the entire manufacturing process becomes about 350 ° C. or lower. At present, the thickness of a general-purpose glass substrate for LCD is 1.1 mm, but if this is 0.7 mm, the glass substrate will not only become cheap, but the weight of the substrate will also be reduced, so that it can be manufactured to carry an LCD. Also has great benefits.

Since the specific gravity of glass is about 2.5 g / cm ³ , for example, the weight of one glass substrate of 400 mm × 500 mm × 1.1 mm is about 550 g. If it is going to process this glass substrate by 100 batches, the weight will be as much as 55 kg and will become a big load with respect to a manufacturing apparatus or a conveyance robot. Needless to say, if this is 0.7 mm, the weight is reduced to 35 kg and the load is considerably reduced. Therefore, thinning of the glass substrate is required, but such a large thin plate glass is warped by its own weight shown in FIG. 4 even at room temperature, and the LPCVD method can form a semiconductor film by any method. I don't get. That is, in order to use such a large thin glass, the semiconductor film must be formed by PECVD at about 350 ° C. or less. However, in general, an amorphous semiconductor film formed by PECVD cannot be crystallized unless heat treatment at about 450 ° C. is performed due to the low density of the film and the high hydrogen content. is there.

  Therefore, the inventor studied various semiconductor films by PECVD method. As a result, PECVD method formed a mixed crystal semiconductor film with a deposition rate of about 0.1 nm / s or more, and this mixed crystal semiconductor film was irradiated with laser. When applied, it has been found that melt crystallization is possible without the aforementioned heat treatment. Although this mixed crystal semiconductor film is slightly crystallized by Raman spectroscopy, it is difficult to say that it is polycrystalline. Further, the density is as low as that of amorphous silicon formed by the conventional PECVD method, and hydrogen atoms are included in less than 20% of silicon atoms.

The details of why such a film is beautifully melted and crystallized are not known, but it is likely that the amorphous region melts more easily than the microcrystalline region, and the microcrystal floating in the molten silicon liquid is silicon. It is thought that it plays a role in suppressing evaporation and scattering of the melt. However, melt crystallization of a mixed crystal semiconductor film having a deposition rate of about 0.1 nm / s or less is difficult. This is because it is assumed that the slow deposition rate of the LPCVD method tends to take in impurities and the quality of the film deteriorates. Similarly, the PECVD method makes it difficult to crystallize mainly due to the impurity contamination during film formation. . The background vacuum degree of the LPCVD apparatus was in the 10 ⁻⁷ torr range, whereas the background vacuum degree of the PECVD apparatus was in the 10 ⁻⁴ torr range is the reason why the PECVD method requires higher film deposition. Let ’s go. When the deposition rate was 0.37 nm / s or higher, the adhesion between the semiconductor film and the base protective film was improved, and crater-like holes and film peeling were hardly observed. A mixed crystal silicon film can be obtained by PECVD with a flow ratio of hydrogen to monosilane of about 30: 1, or an inert gas such as argon and a chemical substance containing a constituent element of a semiconductor film such as monosilane. Even if the flow rate ratio is less than about 33: 1 (monosilane concentration is less than about 3%).

According to the inventor's experiment, the hydrogen-monosilane mixed crystal can be melt-crystallized without heat treatment, but the laser energy range in which the melt-crystallization is successful is limited to several tens of mJ / cm ² . In contrast Argon - mixed-crystallinity silicon film monosilane laser energy is clean crystallize over a wide energy range from 100 mJ / cm ² to 350 mJ / cm ^2. Therefore, the argon-monosilane mixed crystal silicon film is more suitable as a semiconductor film for a low-temperature process poly-Si TFT. The flow ratio of argon to monosilane is optimal for melt crystallization between 124: 1 (monosilane concentration 0.8%) and 40.67: 1 (monosilane concentration 2.4%).

(2-9, PECVD-optimum film thickness of crystallized film)
Here, among the above-described low-temperature process thin film semiconductor devices of the present invention, the optimum semiconductor film thickness of the poly-Si TFT formed by crystallizing the semiconductor film after being deposited by PECVD with a deposition temperature of about 350 ° C. or less. I will explain. In the PECVD method, the film is connected as a film as in the LPCVD method when the film thickness is about 10 nm or more. However, the density of the semiconductor film obtained by the PECVD method is about 85% to 95% of the film density obtained by the LPCVD method. Therefore, when a 10 nm semiconductor film is crystallized by PECVD, the film thickness decreases to about 9 nm after crystallization. Therefore, the minimum film thickness of the PECVD-crystallized film is about 9 nm.

  Thereafter, like the LPCVD-crystallized film, the transistor characteristics of the melt-crystallized film begin to improve when the film thickness is about 18 nm or more. That is, in PECVD-melt crystallized film, thin film deterioration is dominant at about 18 nm or less, and thin film deterioration is reduced from about 18 nm or more, and the thin film effect based on the theory of operation antagonizes. This continues for a film thickness of about 18 nm or more to about 72 nm, and the transistor characteristics are best at the film thickness during this period. When the film thickness is greater than 72 nm, the thin film effect based on the operation theory is superior, and the transistor characteristics gradually deteriorate as the film thickness increases.

  If the semiconductor film thickness is 30 nm or more, a highly integrated thin film semiconductor device that requires fine processing can be stably produced. That is, the contact hole can be stably formed without causing contact failure by RIE. If the semiconductor film thickness immediately after deposition by the PECVD method is about 80 nm or less, the entire film is uniformly heated at the time of melt crystallization such as laser irradiation and the crystallization proceeds beautifully. After crystallization, this film becomes about 72 nm. If the semiconductor film immediately after deposition is thicker than about 150 nm, only the upper part of the film melts when irradiated with laser light from above, and the amorphous part remains in the lower part, so this is combined with the thin film effect based on the theory of operation. As a result, the transistor characteristics are severely degraded. That is, the upper limit film thickness of the PECVD-crystallization method is about 135 nm after crystallization.

(2-10, MOS interface and gate insulating film, and thermal environment)
In the present invention, after the crystallization of the semiconductor film is completed, a gate insulating film is formed by a CVD method, a PVD method, or the like. Regardless of the means used to form the gate insulating film, the insulating film forming temperature is preferably about 350 ° C. or lower. This is important for preventing thermal deterioration of the MOS interface and the gate insulating film. The same applies to all subsequent steps. All process temperatures after the formation of the gate insulating film must be kept below about 350 ° C. In general, an insulating film formed by a CVD method or a PVD method has a large amount of unreacted pairs in the film, and its structure is also unstable. In the present invention, such unreacted pairs are terminated by oxygen plasma irradiation.

Further, a silicon oxide film formed by a CVD method has a Si—OH group in the film. Such a reaction pair terminated with a hydroxyl group or oxygen plasma is unstable to heat and easily dissociates in a thermal environment of about 350 ° C. or higher. That is, unreacted pairs such as Si—O— * and Si— * are generated again in the MOS interface and the gate insulating film, and this becomes a fixed charge in the interface state and the insulating film and degrades the transistor characteristics. Conventionally, hydrogen plasma treatment for about one hour has been performed to recover this. However, in the present application, since the entire process after the formation of the semiconductor film is about 350 ° C. or less, such thermal deterioration does not occur, and thus hydrogenation is not required. After all, according to the present application, a high-performance thin film semiconductor device can be manufactured easily and stably.
Now, such thermal degradation naturally extends to the underlying protective film. As described in the section (2-1), the thermal deterioration of the base protective film leads to the characteristic deterioration of the thin film semiconductor device. Of course, it is not as sensitive as the gate dielectric, but it still has a negligible effect. Therefore, the best thing for thin film semiconductor devices is that all processes including the semiconductor film deposition process are performed at a temperature of about 350 ° C. or lower. By doing so, both the thermal deterioration of the base protective film and the gate insulating film can be avoided. The step of forming the semiconductor film at about 350 ° C. or lower is performed by PECVD or sputtering.

(2-11, VHS-PECVD apparatus used in the present invention)
First, the schematic configuration of the VHS-plasma chemical vapor deposition apparatus (VHS-PECVD apparatus) used in the present invention will be described with reference to FIG. The PECVD apparatus is a capacitive coupling type, and plasma is generated between parallel plate electrodes using a 144 MHz VHS wave power source. 2 is a schematic view of the vicinity of the reaction chamber as viewed from above, and a cross-sectional view taken along the line AA ′ in FIG. The reaction chamber 201 is isolated from the outside air by the reaction vessel 202 and is in a reduced pressure state of about 5 mtorr to 5 torr during film formation. A lower plate electrode 203 and an upper plate electrode 204 are installed in parallel in the reaction vessel 202, and these two electrodes form a parallel plate electrode.

A space between the parallel plate electrodes is a reaction chamber 201. A parallel plate electrode of 410 mm × 510 mm in the present invention, the volume of the reaction chamber 201 because of the distance between the electrodes from 10mm to 50mm and variable becomes 10455Cm ³ from 2091Cm ³ depending on the distance between the electrodes. The distance between the parallel plate electrodes can be freely set between 10 mm and 50 mm as described above by moving the position of the lower plate electrode 203 up and down. Further, when the predetermined distance between the electrodes is set, the deviation of the distance between the electrodes within the 410 mm × 510 mm plate electrode surface is only 0.5 mm. Accordingly, the deviation of the electric field strength generated between the electrodes is 5.0% or less within the plane electrode surface, and a very homogeneous plasma is generated in the reaction chamber 201. A substrate 205 on which a thin film is to be deposited is placed on the lower plate electrode 203, and a substrate edge 2 mm is pressed by a shadow frame 206.

  In FIG. 2, the shadow film 206 is omitted for easy understanding of the outline of the PECVD apparatus. A heater 207 is provided inside the lower plate electrode 203, and the temperature of the lower plate electrode can be arbitrarily adjusted between 25 ° C and 400 ° C. The temperature distribution in the lower plate electrode 203 excluding the periphery of 5 mm is within ± 1.0 ° C. with respect to the set temperature. Even if the size of the substrate 205 is substantially 400 mm × 500 mm, the temperature deviation in the substrate is 2.0. Can be kept within ℃. For example, when the shadow frame 206 uses a general-purpose glass substrate (for example, # 7059 manufactured by Corning Japan Co., Ltd., OA-2 manufactured by Nippon Electric Glass Co., Ltd., NA35 manufactured by NH Techno Glass Co., Ltd.) as the substrate 205, the substrate becomes the heater 207. The substrate is prevented from being deformed into a concave shape by heat from the substrate and unnecessary thin films are not formed on the edge portion and the back surface of the substrate. A reaction gas comprising a raw material gas and, if necessary, an additional gas is introduced into the upper plate electrode 204 through the pipe 208, and is further rubbed between the gas diffusion plates 209 provided in the upper plate electrode from the entire surface of the upper plate electrode. It flows out into the reaction chamber 201 with a substantially uniform pressure. During film formation, part of the reaction gas is ionized when it exits from the upper plate electrode, and plasma is generated between the parallel plate electrodes. A part or all of the reaction gas is involved in the film formation, and the residual reaction gas that was not involved in the film formation and the product gas generated as a result of the chemical reaction of the film formation are provided as exhaust gas at the upper periphery of the reaction vessel 202. The air is exhausted through the exhaust hole 210 formed.

  The conductance of the exhaust hole 210 is sufficiently larger than the conductance between the parallel plate electrodes, and the value is preferably 100 times or more the conductance between the parallel plate electrodes. Further, the conductance between the parallel plate electrodes is sufficiently larger than the conductance of the gas diffusion plate 209, and the value is preferably 100 times or more the conductance of the gas diffusion plate. With such a configuration, the reaction gas is introduced into the reaction chamber with a substantially uniform pressure from the entire surface of the large upper plate electrode of 410 mm × 510 mm, and at the same time, the exhaust gas is exhausted from the reaction chamber at a uniform flow rate in all directions. The flow rates of the various reaction gases are adjusted to predetermined values by the mass flow controller before being introduced into the pipe 208.

The pressure in the reaction chamber 201 is adjusted to a desired value by a conductance valve 211 provided at the outlet of the exhaust hole. A vacuum exhaust device such as a turbo molecular pump is provided on the exhaust side of the conductance valve 211. In the present invention, an oil-free magnetic levitation turbomolecular pump is used as a part of the vacuum evacuation device, and the degree of background vacuum in a reaction vessel such as a reaction chamber is set to 10 ⁻⁷ torr. In FIG. 2, the outline of the gas flow is shown by arrows. The reaction vessel 202 and the lower plate electrode 203 are at the ground potential, and the upper plate electrode 204 and the upper plate electrode 204 are electrically insulated by the insulating ring 212. When plasma is generated, for example, a 144 MHz VHS wave output from the VHS wave oscillation source 213 is amplified by the amplifier 214 and then applied to the upper plate electrode 204 via the matching circuit 215.

  As described above, the PECVD apparatus used in the present invention is a thin film forming apparatus capable of handling a large substrate of 400 mm × 500 mm by realizing extremely sophisticated interelectrode control and a homogeneous gas flow. However, as long as these basic concepts are followed, it is possible to easily cope with further increase in the size of the substrate, and it is possible to realize an apparatus that can actually handle a larger substrate of 550 mm × 650 mm. In the present invention, a VHS wave having a relatively high frequency of 144 MHz is used. Of course, a VHS wave having another frequency may be used. For example, all VHF waves of about 100 MHz to 1 GHz can be used. On the other hand, if an rf wave having a frequency of about 10 MHz to a VHF wave having a frequency of about several hundreds of MHz, plasma can be generated between parallel plate electrodes, and is an integer multiple of the industrial rf frequency (13.56 MHz) 27. .12 MHz, 40.68 MHz, 54.24 MHz, 67.8 MHz, or the like may be used.

  That is, plasma can be easily generated using an electromagnetic wave having a desired frequency by exchanging the VHS wave oscillation source 213, the amplifier 214, and the matching circuit 215 of the PECVD apparatus used in the present invention. In general, in electromagnetic plasma, when the frequency is increased, the electron temperature in the plasma is increased and the generation of radicals is facilitated. Therefore, even if the substrate surface temperature is as low as about 340 ° C. A poly-Si TFT can be easily manufactured without performing a crystallization process.

(2-12, semiconductor film formation by VHS-PECVD method or microwave PECVD method and gas used in that case)
One of the features of the present invention is that the film (As-deposited film) immediately after deposition is made into a polycrystalline state by the VHS-PECVD method or the microwave PECVD method. Usually, it is very difficult to make an As-deposited film polycrystalline by PECVD. This is because the substrate temperature is as low as less than about 400 ° C., so that the mobility of the raw material such as silane on the growth film surface is reduced, and the selectivity of the raw material to the polycrystalline state with respect to the amorphous state is lost. . The present invention eliminates this drawback in the PECVD method by the method of diluting the source material with a rare gas group element and the use of VHS plasma or microwave plasma capable of increasing the electron temperature. In order to form a polycrystalline film in the As-deposited state, radicals and ions of rare gas group elements such as helium (He), neon (Ne), and argon (Ar) are created without creating radicals and ions of the source material. These require the energy to be transported to the substrate surface. Since radicals and ions of the source material cause a gas phase reaction or react at the moment when the source material arrives at the substrate surface, the loss of selectivity occurs and the polycrystalline growth is inhibited. Therefore, generation of such radicals and ions in the plasma must be avoided as much as possible.

  The raw material is brought to the surface of the growth film in an inactive state, and after adsorbing on the growth film, when energy for reaction is supplied by a diluent gas or the like, a polycrystalline film is formed in an As-deposited state. For this reason, it is required to dilute the source gas, and further, it becomes necessary to select a gas that promotes the reaction of the source material on the substrate surface as the diluted substance. It goes without saying that noble gas group elements consist of simple atoms, and therefore the spectrum of ionization potential is very simple. For example, the monovalent ionization potential of helium is 24.487 eV and the divalent ionization potential is only 54.416 eV. Further, the monovalent ionization potential of neon is 21.564 eV, the divalent ionization potential is 40.62 2 eV, the monovalent ionization potential of argon is 15.759 eV, the divalent ionization potential is 27.629 eV, and the trivalent ionization potential is 40.74 eV. It is.

  Therefore, when a plasma is generated by diluting a small amount of source material in helium, most of the ionized helium is monovalent ions of 24.487 eV, and a plasma is generated by diluting a small amount of source material in neon. In this case, the monovalent ion of neon at 21.564 eV is mainly ionized. In argon, both monovalent ions and divalent ions are dominant, but since the ionization energy is relatively low, argon radicals and ions are effectively generated without diluting the source material with argon in large quantities. On the other hand, in the case of hydrogen, which has been widely used as a conventional dilution gas, there are dozens of different ionization potentials between 15 eV and 18 eV. Therefore, rare gas group elements such as helium form a plasma state with one or two energies (laser light when compared to light), whereas molecular gas such as hydrogen is a plasma state where a lot of energy is mixed ( Compared to light, white light).

  When the source gas is diluted with a rare gas group element so that the laser beam can transport energy more effectively than the white light, the energy is more effectively transferred to the substrate surface. In addition to the rare gas group elements such as helium, neon, and argon, of course, krypton (Kr) or xenon (Xe) may be used as the diluent material during the semiconductor film deposition. On the other hand, since VHS plasma and microwave plasma have a high average electron temperature in the plasma, the radical generation efficiency can be increased at a relatively low output. In other words, since it is not necessary to have a high output, the generation of high-energy ions is small, and therefore the damage to the film due to these is minimized. Furthermore, the high radical generation efficiency also increases the deposition rate. Even if the present invention is carried out with a 13.56 MHz rf plasma that has been widely used in the past, the film formation rate is extremely slow, being several liters / min or less, which is not suitable for practical use, and is too slow. The speed will suffer and the film quality will also be degraded.

  That is, the present invention is achieved only by using VHS plasma or microwave plasma. In that sense, the present invention can be achieved very easily even by a microwave PECVD method that is an integral multiple of a higher frequency of 2.45 GHz. In these systems, the degree of freedom of film forming conditions is greater than that of VHS-PECVD. A good quality crystalline semiconductor film is deposited more easily.

(2-13, optimum film thickness of As-deposited film by VHS-PECVD method or microwave PECVD method)
When the film immediately after deposition (As-deposited film) is made into a polycrystalline state by the VHS-PECVD method or the microwave PECVD method, the film quality is very poor compared with a normal crystallized film when the film thickness is about 0 to 500 mm. . Small crystal grains are scattered like islands in the amorphous sea, the crystallinity is very low, and there are many defects. When the thickness is from 500 to 1000%, the ratio of crystal grains to amorphous increases, and when the film thickness is from about 1000 to 1500 mm, the semiconductor surface is temporarily covered with crystal grains, and the amorphous component on the surface is almost lost. The crystal grain size gradually increases with the film thickness from about 1500 to 2000 mm, and the film grows in substantially the same shape when it reaches 2000 mm or more. The film thickness dependence of transistor characteristics also changes in accordance with the change in film quality with respect to the film thickness. Since the film quality hardly changes at 2000 mm or more (since there is almost no deterioration of the thin film), the thin film effect based on the operation theory works, and the thinner the film, the better the transistor characteristics.

  Thin film degradation starts to work when the film thickness is 2000 to 1500 mm. However, the thin film effect based on the operation theory is still dominant, and it is more gradual than 2000 mm or more. However, the thinner the Yahari film, the better the transistor characteristics. When the film thickness is about 1500 to 200 mm, the thin film theory and the thin film theory based on the operation theory compete, and the on-state transistor characteristic takes the maximum value. If the film thickness is less than 200 mm, the thin film deterioration overcomes the thin film effect based on the theory of operation, and the transistor characteristics deteriorate as the film becomes thinner. That is, in the case of the present invention, the transistor characteristics are best when the semiconductor film thickness is between 200 and 1500 mm, and ideally between 400 and 1300 mm.

  Up to this point, the transistor characteristics have been described as on-state characteristics, but the off-state leakage current also differs depending on the film thickness. The principle of off-leakage in thin film semiconductor devices is not well understood. Although the principle is unknown in the present invention, when the film thickness is 1000 mm or more, the film thickness and off-leakage have a strong positive correlation, and the thicker the film, the larger the off-leakage. When the film thickness is 1000 mm or less, the correlation becomes weak and the off-leakage becomes independent of the film thickness. That is, the off-leakage current value is a minimum value and substantially constant when the film thickness is between 0 and 1000 mm. Therefore, the film thickness with the best transistor characteristics in the on state and the minimum off-leakage is 200 to 1000 mm, and ideally 400 to 1000 mm. When the thin film semiconductor device of the present invention is used for an LCD, it is preferable to consider the influence of off-leakage light irradiation.

  In a thin film semiconductor device, off-leakage current increases due to light irradiation. This is called a light leakage current, and the condition for a good thin film semiconductor device is that the light leakage current is sufficiently small. In the thin film semiconductor device of the present invention, the light leakage current is proportional to the film thickness. From the standpoint of achieving both stable manufacturing and light leakage current, the semiconductor film thickness is preferably about 100 to 800 mm. When off-leakage or light leakage is important, such as when a thin film semiconductor device is used as a pixel switching element of an LCD, the semiconductor film thickness is preferably 100 to 700 mm. When it is necessary to consider the on-current more strongly, the optimum film thickness is about 200 to 800 mm, and the system satisfying all the conditions is 400 to 800 mm, ideally 600 to 800 mm.

  Also, it is usually quite difficult to activate the implanted ions in the source / drain regions at a low temperature of 350 ° C. or lower as in the present invention. Therefore, in order to perform activation stably, a lower limit must be set for the semiconductor film thickness. In the present invention, this value is preferably 300 mm or more. In addition, when the LDD structure is adopted, 500 mm or more is preferable.

(2-14, crystallization of semiconductor film by VHS-PECVD method or microwave PECVD method)
As described in detail in the section (2-12), when the VHS-PECVD method is used, a polycrystalline film can be easily obtained in an As-deposited state, but these are not as excellent in film quality as a crystallized film. On the other hand, it is difficult to crystallize a film usually obtained by PECVD unless hydrogen removal or densification heat treatment is performed. On the other hand, the semiconductor film of the VHS-PECVD method or the microwave PECVD method can be very easily crystallized by the RTA method or the VST-SPC method, or melt crystallized by laser irradiation or the like. This is because most of the crystal is already crystallized in the As-deposited state, and the residual amorphous component is small, so that the residual amorphous is crystallized with a relatively low energy supply. In addition, since the polycrystalline component plays a role in preventing evaporation and scattering of semiconductor atoms when performing melt crystallization at high energy, crystallization proceeds without causing damage, surface roughness, disappearance, etc. of the semiconductor film. It is done.

  After all, the film obtained by the VHS-PECVD method or the microwave PECVD method has a maximum process temperature of about 350 ° C. or less using melt crystallization rather than being an active part of a thin film semiconductor device in the As-deposited state. It can be said that it is more suitable for the first semiconductor film when manufacturing the low temperature poly-Si TFT. That is, a semiconductor film is formed on an insulating material by VHS-PECVD method or microwave PECVD method, and this film is then solid-phase crystallization method such as RTA method or VST-SPC method, or melt crystallization method such as laser irradiation. The high-performance thin film semiconductor device can be easily manufactured by crystallizing the film and the like and setting the subsequent steps to about 350 ° C. or lower.

  A film deposited by the VHS-PECVD method or the microwave PECVD method is closer in quality to a film deposited by the LPCVD method than a film deposited by the conventional PECVD method.

  Therefore, the relationship between the transistor characteristics and the semiconductor film thickness obtained when the thin film semiconductor device is formed by crystallization is also equal to the relationship possessed by the thin film semiconductor device of LPCVD method. However, the semiconductor film formed by the LPCVD method hardly loses before and after crystallization, whereas the VHS-PECVD method or the microwave PECVD method shows a slight film reduction. Therefore, when these films are crystallized to produce a thin film semiconductor device, the film thickness of the semiconductor after the crystallization is made to be the same as the film thickness of the LPCVD method-crystallized film (2-6). We can apply the discussion of the term as it is.

  As described above, according to the present invention, a high-quality semiconductor film made of a polycrystalline silicon film or the like can be easily formed at a low temperature of less than about 450 ° C., and further about 430 ° C. or less. The characteristics have been dramatically improved and stable mass production has been realized. Specifically, the following effects can be obtained.

Effect 1). Since the process temperature is as low as less than about 450 ° C., inexpensive glass can be used, and the product price can be reduced. In addition, distortion due to the weight of the glass itself can be prevented, so that a liquid crystal display (LCD) can be easily enlarged.

Effect 2). Since the process temperature is as low as about 350 ° C. or lower, thermal degradation of the base protective film and the gate insulating film does not occur, and a thin film semiconductor device with high performance and excellent reliability can be easily manufactured.

Effect 3). Laser irradiation can be performed uniformly over the entire substrate. As a result, the uniformity of each lot was improved, and stable production became possible.

Effect 4). It has become remarkably easy to activate a self-aligned TFT in which the source and drain are self-aligned with the gate electrode at an ion doping method and subsequently at a low temperature of about 300 ° C. to 350 ° C. As a result, it became possible to activate stably. Furthermore, a lightly doped drain (LDD) TFT can be formed easily and stably. Since the LDD TFT is realized by a low-temperature process poly-Si TFT, it is possible to miniaturize the TFT element and reduce the off-leakage current.

Effect 5). Conventionally, low-temperature process poly-Si TFTs have shown good transistor characteristics only with SiO ₂ prepared by ECR-PECVD, but a general-purpose PECVD apparatus can be used according to the present invention. Therefore, a practical gate oxide film manufacturing apparatus that can be applied to a large substrate and has high mass productivity can be obtained.

Effect 6). A better thin film semiconductor device having a larger on-current and smaller off-current than the conventional one was obtained. These variations were also reduced.

Effect 7). When inexpensive general-purpose glass or the like is used for the substrate, the base protective film that effectively prevents impurities from entering the semiconductor film can be used as a base protective film for a thin film semiconductor device that exhibits the best electrical characteristics at the same time. It was. Further, it has been avoided that the electrical characteristics of the thin film semiconductor device are deteriorated due to the stress from the base protective film, or that the thin film semiconductor device is cracked.

Effect 8). When the semiconductor film is formed by plasma enhanced chemical vapor deposition (PECVD), it is possible to prevent the constituent elements of the cleaning gas such as fluorine (F) and carbon (C) from entering the semiconductor film. As a result, the amount of impurities mixed between the substrates can always be minimized, and an excellent thin film semiconductor device can be stably manufactured.

Effect 9). Even when a semiconductor film is deposited at a low temperature of less than about 450 ° C. by low-pressure chemical vapor deposition (LPCVD), it is possible to achieve both uniformity and deposition rate within and between substrates. . Therefore, it is possible to cope with an increase in the size of the substrate, and a large LCD can be mass-produced.

Effect 10). In addition to variations within the substrate, there are three types of variations in the electrical characteristics of the thin film semiconductor device: variations between substrates within the same lot and variations between lots. Variations can be controlled. In particular, the variation among lots in the PECVD method was remarkably improved.

Effect 11). Even when the semiconductor film is formed by PECVD, the adhesion between the semiconductor film and the base protective film can be improved. That is, it is possible to avoid a situation in which an infinite number of crater-like holes are generated in the semiconductor film or the film is peeled off.

Effect 12). In particular, a poly-Si TFT can be stably produced on a large-area substrate by a low temperature process of about 350 ° C. or less without performing an extra crystallization process.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A to 1D are element sectional views in respective steps of manufacturing a thin film semiconductor device according to an embodiment of the present invention. FIG. 2 is a diagram showing a PECVD apparatus used in the present invention. FIG. 3 is a view showing the film forming chamber and the inside of the LPCVD apparatus according to the present invention. FIG. 4 is a diagram for explaining the warpage of the substrate due to the thermal environment. FIG. 5 is a diagram for explaining the effect of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the accompanying drawings.

(Example 1)
FIGS. 1A to 1D are cross-sectional views showing a manufacturing process of a thin film semiconductor device for forming a MIS field effect transistor.
In Example 1, 235 mm □ non-alkali glass (Nippon Electric Glass Co., Ltd. OA-2) was used as the substrate 101, but the type and size of the substrate are of course not limited as long as the substrate can withstand the maximum process temperature. Absent. First, a silicon dioxide film (SiO ₂ film) 102 serving as a base protective film is formed on a substrate 101 by an atmospheric pressure chemical vapor deposition method (APCVD method), a PECVD method, or a sputtering method. In the APCVD method, a SiO ₂ film can be deposited using monosilane (SiH ₄ ) or oxygen as a raw material at a substrate temperature of about 250 ° C. to 450 ° C. In the PECVD method or the sputtering method, the substrate temperature can be changed from room temperature to 400 ° C. In Example 1, a 2000 Å SiO ₂ film was deposited at 300 ° C. using SiH ₄ and O ₂ as source gases by the APCVD method.

Next, an intrinsic silicon film, which later becomes an active layer of the thin film semiconductor device, was deposited by about 500 mm. Intrinsic silicon film at a high vacuum type LPCVD apparatus, disilane as a source gas of (Si ₂ H ₆₎ was deposited 58 minutes at 200sccm flow deposition temperature 425 ° C.. The high vacuum type LPCVD apparatus used in Example 1 has a volume of 184.51. The 17 substrates were inserted into a reaction chamber maintained at 250 ° C. with the front side facing down. After inserting the substrate, the operation of the turbo molecular pump was started, and after reaching a steady rotation, a leakage inspection was performed for 2 minutes.

The leakage rate of degassing, etc. at this time was 3.1 × 10 ⁻⁵ torr / min.
Thereafter, the temperature was raised from an insertion temperature of 250 ° C. to a deposition temperature of 425 ° C. over one hour. During the first 10 minutes of temperature increase, no gas was introduced into the reaction chamber and the temperature was increased in vacuum. The minimum background pressure reaching the reaction chamber 10 minutes after the start of temperature increase was 5.2 × 10 ⁻⁷ torr. Further, a nitrogen gas having a purity of 99.9999% or more was continuously supplied for 300 sccm during the remaining 50 minutes. The equilibrium pressure in the reaction chamber at this time was 3.0 × 10 ⁻³ torr. After reaching the deposition temperature, Si ₂ H ₆ as a source gas was flowed at 200 sccm and 1000 sccm of dilution helium (He) having a purity of 99.9999% or more, and a silicon film was deposited for 58 minutes. The pressure immediately after introducing a gas such as Si ₂ H ₆ into the reaction chamber was 767 mtorr, and the pressure 57 minutes after the introduction of these source gases was 951 mtorr. The film thickness of the silicon film thus obtained was 501 mm, and the film thickness fluctuation within a square area of 221 mm □ excluding the peripheral portion of the substrate 7 mm was less than ± 5 mm. In the first embodiment, the silicon film is formed by the LPCVD method in this way, but the forming method is not limited to this, and a PECVD method or a sputtering method may be used. In the PECVD method or the sputtering method, the silicon film formation temperature can be set from room temperature to about 350 ° C.

  The silicon film thus obtained is a high-purity a-Si film. Next, the a-Si film is irradiated with optical energy or electromagnetic wave energy for a short time to crystallize a-Si and modify it into polycrystalline silicon (poly-Si). In Example 1, an excimer laser (wavelength: 308 nm) of xenon chloride (XeCl) was irradiated.

The intensity half width of the laser pulse is 45 ns. Since the irradiation time is such a very short time, the substrate is not heated during the crystallization of a-Si to poly-Si, and therefore the substrate is not deformed. Laser irradiation was performed in air with the substrate at room temperature (25 ° C.). The area of one irradiation of laser irradiation is a square of 8 mm □, and is shifted by 4 mm for each irradiation. After scanning in the horizontal direction (Y direction) first, the vertical direction (X direction) is then shifted by 4 mm, and then the horizontal direction is shifted by 4 mm again. Thereafter, this scanning is repeated and the entire surface of the substrate is repeated for the first time. Perform laser irradiation. This first laser irradiation energy density was 160 mJ / cm ² .

After the first laser irradiation is completed, the second laser irradiation is performed on the entire surface with an energy density of 275 mJ / cm ² . The scanning method is the same as in the first laser irradiation, and an 8 mm square irradiation region is scanned by shifting 4 mm in the Y direction and the X direction. By this two-stage laser irradiation, the entire substrate is crystallized uniformly from a-Si to poly-Si. In the first embodiment, a XeCl excimer laser is used as optical energy or electromagnetic wave energy. However, the energy source is not restricted if the energy irradiation time is within several tens of seconds. For example, ArF excimer laser, XeF excimer laser, KrF excimer laser, YAG laser, carbon dioxide gas laser, Ar laser, dye laser, or other lasers, or lamp light such as arc lamp or tungsten lamp may be irradiated. . In the case of performing arc lamp irradiation, the film quality change from a-Si to poly-Si proceeds by setting the lamp output to about 1 kW / cm ² or more and the irradiation time to about 45 seconds. Even during this crystallization, since the energy irradiation time is short, the substrate is not deformed or cracked by heat. Next, this silicon film was patterned to form a channel portion semiconductor film 103 which becomes an active layer of the transistor. (Fig. 1 (a))
After that, the gate insulating film 104 is formed by ECR-PECVD method or PECVD method. In Example 1, a SiO ₂ film was used as the gate insulating film, and deposited to a thickness of 1200 mm by PECVD. (FIG. 1B) Immediately before the substrate was placed in the PECVD apparatus, the substrate was immersed in a 1.67% hydrofluoric acid aqueous solution for 20 seconds to remove the natural oxide film on the surface of the semiconductor film. The time from removing the oxide film to putting the substrate into the load lock chamber of the PECVD apparatus was about 15 minutes. This time is desired to be as short as possible from the viewpoint of MOS interface cleaning, and is preferably within about 30 minutes at the longest.

In the PECVD method, it was formed at a substrate temperature of 300 ° C. using monosilane (SiH ₄ ) and laughing gas (N ₂ O) as source gases. The plasma was generated under the conditions of an output of 900 W and a degree of vacuum of 1.50 torr by a 13.56 MHz rf wave. The flow rate of SiH ₄ was 250 sccm and the flow rate of N ₂ O was 7000 sccm. The deposition rate of the SiO ₂ film was 48.3 Å / s. Immediately before and immediately after depositing SiO ₂ under these conditions, the silicon film and the formed oxide film were irradiated with oxygen plasma to improve the MOS interface and the oxide film. In the first embodiment, monosilane and laughing gas are used as source gases, but not limited to these, organic silane such as TEOS (Si— (O—CH ₂ —CH ₃ ) ₄ ) and oxidizing gas such as oxygen are used. May be. Further, although a highly versatile PECVD apparatus is used here, it goes without saying that an insulating film may be formed by an ECR-PECVD apparatus. Whatever CVD apparatus or source gas is used, the insulating film formation temperature is preferably 350 ° C. or lower. This is important for preventing thermal deterioration of the MOS interface and the gate insulating film. The same applies to all the following steps. All process temperatures after the formation of the gate insulating film must be kept below 350.degree. This is because a high performance thin film semiconductor device can be manufactured easily and stably.

Subsequently, a thin film to be the gate electrode 105 is deposited by sputtering or vapor deposition. In Example 1, tantalum (Ta) was selected as the gate electrode material, and 5000 liters were deposited by sputtering. The substrate temperature during sputtering was 180 ° C., and argon (Ar) containing 6.7% nitrogen (N ₂ ) was used as the sputtering gas. The optimal nitrogen content in the argon is 5.0% to 8.5%. The crystal structure of the tantalum film obtained under these conditions is mainly an α structure, and its specific resistance is 40 μΩcm. Therefore, the sheet resistance of the gate electrode in Example 1 is 0.8Ω / □.

After depositing a thin film to be a gate electrode, patterning is performed, and subsequently, impurity ion implantation 106 of phosphorus element or the like is performed on the intrinsic silicon film using a bucket-type mass non-separation type ion implantation apparatus (ion doping method). A drain region 107 and a channel region 108 were formed. (FIG. 1 (c)) Since this Example 1 aimed to produce an NMOS TFT, phosphine (PH ₃ ) having a concentration of 5% diluted in hydrogen was used as a source gas, and a high frequency output of 38 W and an acceleration voltage of 80 kV were used. A concentration of × 10 ¹⁵ l / cm ² was driven. As the high-frequency output, an appropriate value of about 20 W to 150 W is used. When making a PMOS TFT, diborane (B ₂ H ₆ ) with a concentration of 5% diluted in hydrogen is used as a source gas, the high frequency output is changed from 20 W to 150 W, the acceleration voltage is 60 kV, and 5 × 10 ¹⁵ l / cm. Type in a density of about ² . When a CMOS TFT is formed, one of NMOS and PMOS is alternately covered with a mask using a suitable mask material such as polyimide resin, and each ion implantation is performed by the above-described method.

Next, 5000 μm of interlayer insulating film 109 is deposited. In Example 1, SiO ₂ was formed by PECVD as an interlayer insulating film. In the PECVD method, TEOS (Si— (O—CH ₂ —CH ₃ ) ₄ ) and oxygen (O ₂ ) were used as source gases at a substrate temperature of 300 ° C. The plasma was generated by a 13.56 MHz rf wave under conditions of an output of 800 W and a degree of vacuum of 8.0 torr. The TEOS flow rate was 200 sccm and the O ₂ flow rate was 8000 sccm. At this time, the deposition rate of the SiO ₂ film was 120 Å / s. After such ion implantation and formation of the interlayer insulating film, heat treatment was performed at 300 ° C. for 1 hour in an oxygen atmosphere to activate the implanted ions and to burn the interlayer insulating film. The heat treatment temperature is preferably 300 ° C to 350 ° C.

  Thereafter, contact holes are opened, and source / drain extraction electrodes 110 are formed by sputtering or the like, thereby completing a thin film semiconductor device. (FIG. 1D) Indium tin oxide (ITO) or aluminum (Al) is used as a source / drain extraction electrode. The substrate temperature during sputtering of these conductors is about 100 ° C. to 250 ° C.

When the transistor characteristics of the thin film semiconductor device manufactured in this way were measured, the source / drain current Ids when the transistor was turned on with the source / drain voltage Vds = 4 V and the gate voltage Vgs = 10 V was defined as the on-current ION. Thus, ION = (23.3 + 1.73, −1.51) × 10 ⁻⁶ A with a 95% reliability coefficient.

The off-state current when the transistor was turned off at Vds = 4 V and Vgs = 0 V was IOFF = (1.16 + 0.38, −0.29) × 10 ⁻¹² A. Here, the measurement was performed at a temperature of 25 ° C. for a transistor having a channel portion length L = 10 μm and a width W = 10 μm. The effective electron mobility (J. Levinson et al. J, Appl, Phys. 53 , 1193'82) obtained from the saturation current region is μ = 50.92 ± 3.26 cm ² / v. sec. On the other hand, in the conventional low-temperature process poly-Si TFT, ION = (18.7 + 2.24, −2.09) × 10 ⁻⁶ A, IOFF = (4.85 + 3.88, −3.27) × 10 ^-12 A. As described above, according to the present invention, a thin film semiconductor device having a high mobility, an Ids changing by 7 digits or more with respect to a modulation of 10 V of the gate voltage, and an extremely excellent and uniform thin film semiconductor device with a small variation is 425 ° C. In the following, it was realized for the first time in a low-temperature process in which the period maintained at the maximum process temperature is within several hours. As described above, the uniformity of laser crystallization has been an important issue regardless of whether in the substrate or between lots.

  However, according to the present invention, both the on-current and the off-current can greatly reduce the variation thereof. In particular, the uniformity of off-current is remarkably improved as compared with the prior art, and when the thin film semiconductor device of the present invention is applied to an LCD, a uniform high image quality can be obtained over the entire LCD screen.

This improvement in uniformity means that the initial silicon film is stable with respect to the variation of the laser source, that is, the present invention has made a significant improvement even with respect to the variation between lots. . As described above, according to the present invention, crystallization of silicon using energy irradiation such as laser irradiation can be performed extremely stably. According to the inventor's experiment, when the initial silicon film is formed at a low temperature of less than 450 ° C. and the deposition rate of the silicon film is set to about 2 Å / min or more, it is stable against the fluctuation of the laser, and the ECR-PECVD apparatus is used. It has been found that a thin-film semiconductor device having good transistor characteristics can be produced even if an SiO ₂ film formed without using it is used as a gate insulating film. Further, the poly-Si film obtained in this way is stable and easy to activate for the formation of a lightly doped drain (LDD) structure by an ion doping method, as will be described later. This is because the a-Si film formed under such conditions has a completely amorphous structure that does not contain fine crystallites, and each component constituting the a-Si film is large. It is far from being made up of lumps. Since the a-Si film does not contain fine crystallites, crystallization accompanying energy irradiation proceeds uniformly in the irradiation region.

  At the same time, since the a-Si film is composed of large lumps, the size of each crystal grain when crystallized increases, and high-performance electrical characteristics can be obtained. That is, an ideal a-Si film can be obtained by optimizing the film formation conditions of the initial a-Si film, and a uniform and high-quality poly-Si film can be obtained by crystallizing these. The a-Si film conforming to the prior art has a deposition temperature of about 550 ° C. by the LPCVD method or the substrate temperature of about 400 ° C. by the PECVD method. The problem as described above was caused because it was not paid.

  Another gist of the present invention is to suppress the process temperature after forming the poly-Si film to 350 ° C. or lower. This is because the MOS interface and the insulating film quality can be stabilized. In that sense, the present invention is particularly effective for an upper gate type TFT as shown in FIG. In the case of the lower gate type TFT, a silicon film is deposited after the gate insulating film is formed, and further crystallization such as laser irradiation is performed. It is exposed to the environment even for a short time. This thermal environment roughens the MOS interface and further changes the chemical composition and bonding state of the insulating film near the MOS interface. As a result, the transistor characteristics are deteriorated and the variation becomes large.

(Example 2)
Another embodiment of the present invention will be described with reference to FIGS. 1 (a) to 1 (d).
In Example 2, 300 mm × 300 mm non-alkali glass (Nippon Electric Glass Co., Ltd. OA-2) and 300 mm × 300 mm crystallized glass (Ohara TRC-5) were used as the substrate 101. The strain point of OA-2 is about 650 ° C., and since TRC-5 is a crystallized glass, the strain point cannot be defined, but if the temperature is up to about 700 ° C., no deformation or distortion of the substrate is recognized at all. The substantial strain point can be said to be about 700 ° C. or higher. First, a silicon oxide film 102 serving as a base protective film was formed on the substrate 101 by PECVD. The conditions for forming the silicon oxide film are the same as those for forming the gate insulating film in the first embodiment. The film thickness of the silicon oxide film is 300 nm, and the surface roughness is 0.98 nm in terms of centerline average roughness. Similar to the gate insulating film of Example 1, oxygen plasma was irradiated for 15 seconds immediately before and immediately after the oxide film formation.

Next, an intrinsic silicon film, which later becomes an active layer of the thin film semiconductor device, was deposited by about 500 mm. The intrinsic silicon film was deposited at a deposition temperature of 425 ° C. and a pressure of 320 mtorr by flowing 400 sccm of disilane (Si ₂ H ₆ ) as a source gas in the high vacuum type LPCVD apparatus described in the section (2-3) as in Example 1. . The deposition rate is 1.30 nm / min. The 35 OA-2 substrates and 35 TRC-5 substrates are in pairs, each with the TRC-5 substrate facing down (the surface of the TRC-5 substrate faces down), and OA-2 The substrates were placed on the upper side (the surface of the OA-2 substrate faced up), and the back surfaces were put together and placed in a film formation chamber maintained at 250 ° C. with a substrate interval of 10 mm. The area of the portion where the semiconductor film is formed in the deposition chamber is 88262 cm ² , and the disilane flow rate per unit area is 4.53 × 10 ⁻³ sccm / cm ² . After the substrate was placed, the temperature was raised from 250 ° C. as the insertion temperature to 425 ° C. as the deposition temperature, and after a heat parallel state was obtained at 425 ° C., a silicon film was deposited for 40 minutes. The pressure during film formation was maintained at 320 mtorr by the pressure regulator of the LPCVD apparatus. The thickness of the silicon film thus deposited was 52.4 nm.

  Next, the a-Si film is irradiated with optical energy or electromagnetic wave energy for a short period of time to melt and crystallize a-Si to be modified into polycrystalline silicon (poly-Si). In Example 2 as well, xenon chloride (XeCl) excimer laser (wavelength: 308 nm) was irradiated. Immediately before laser irradiation, the substrate was immersed in a 1.67% hydrofluoric acid aqueous solution for 20 seconds to remove the natural oxide film on the surface of the semiconductor film. The time from removal of the oxide film to laser irradiation was about 20 minutes. After the crystallization of the semiconductor film was completed, a poly-Si TFT was manufactured by a low-temperature process in exactly the same steps as in Example 1 below.

When the transistor characteristics of the thin film semiconductor device thus fabricated were measured, the on-current was ION = (41.9 + 2.60, −2.25) × 10 ⁻⁶ A with a 95% reliability coefficient. The off-state current was IOFF = (6.44 + 2.11, −1.16) × 10 ⁻¹³ A. Here, the measurement conditions are the same as in Example 1. The effective electron mobility is μ = 90.13 ± 4.61 cm ² / v. A very good thin film semiconductor device was manufactured in a simple process and stably.

(Example 3)
After forming a poly-Si film by the method described in detail in Example 1, a SiO ₂ film corresponding to the gate insulating film described in detail in Example 1 is deposited without patterning the poly-Si film, Impurity ions such as PH ₃ were implanted into the poly-Si film by the ion doping method described in detail in Example 1. The film thickness and film forming conditions of the poly-Si film and the SiO ₂ film are exactly the same as those in the first embodiment. Impurity ion implantation conditions are the same as those in Example 1 ^except that the implantation amount is set to 3 × 10 ¹³ cm ⁻² . The third embodiment corresponds to creating an LDD region with the TFT described in the first embodiment.

  After phosphorus ion implantation, heat treatment was performed at 300 ° C. for one hour in oxygen in the same manner as in Example 1 in which the arrows were formed. Thereafter, the insulating film was peeled off, and the sheet resistance of the n-type poly-Si film containing phosphorus ions was measured. As a result, the sheet resistance value was 95% reliable within a 221 mm square area excluding the peripheral portion of the substrate 7 mm. The coefficient was (14 ± 2.6) kΩ / □. Conventionally, SSDM'93 (sold state Devices and Materials 1993) p. Activation could not be performed without adding a special process such as hydrogen injection as described in 437. Moreover, the sheet resistance at that time was as high as 50 kΩ or more, and the variation was 10 kΩ or more. On the other hand, in the present invention, an LDD region having a low resistance can be easily formed by an ion doping method, and the variation can be reduced to a quarter or less of the conventional one.

Example 4
In Example 4, a base protective film and a semiconductor film are continuously formed by PECVD using 13.56 MHz rf waves, and then crystallized to produce a thin film semiconductor device.

The substrate 101 was made of alkali-free glass having a size of 360 mm × 465 mm × 0.7 mm. Before the glass substrate is placed in the PECVD apparatus, the thin film formed on the front side of the substrate is removed from the deposition chamber. That is, the film forming chamber is cleaned for 15 seconds. The cleaning conditions were an rf output of 1600 W (0.8 W / cm ² ), an interelectrode distance of 40 mm, an NF ₃ flow rate of 3200 sccm, an argon flow rate of 800 sccm, and a pressure of 1.0 torr. Next, after vacuuming for 15 seconds, a silicon nitride film is deposited for 15 seconds as a passivation film in the film formation chamber. Deposition conditions are an rf output of 300 W (0.15 W / cm ² ), a distance between electrodes of 40 mm, a pressure of 1.2 torr, a nitrogen flow rate of 3500 sccm, an ammonia flow rate of 500 sccm, and a monosilane flow rate of 100 sccm. After evacuation for 15 seconds, the substrate is placed in the film formation chamber.

  The time until the substrate prepared in the load lock chamber is installed in the film formation chamber is about 10 seconds. A stabilization period is provided for 30 seconds before the next base protective film deposition. All the process parameters are the same as the deposition conditions of the underlying protective film except that no plasma is generated during the stabilization period. From the base protective film to the semiconductor film formation, the lower plate electrode temperature is 360 ° C. and the substrate surface temperature is about 340 ° C. After the stabilization period, a base protective film is deposited. As the base protective film, a silicon nitride film and a silicon oxide film are laminated. First, a silicon nitride film is deposited for 30 seconds at an rf output of 800 W, an electrode distance of 25 mm, a pressure of 1.2 torr, a nitriding flow rate of 3500 sccm, an ammonia flow rate of 500 sccm, and monosilane of 100 sccm.

Subsequently, a silicon oxide film was deposited for 30 seconds at an rf output of 900 W, a distance between electrodes of 25 mm, a pressure of 1.5 torr, a monosilane flow rate of 250 sccm, and an N ₂ O flow rate of 7000 sccm. After nitriding and the thickness of the oxide film are approximately 150 nm, a base protective film of about 300 nm in total is formed. Oxygen plasma is irradiated for 20 seconds continuously after forming the oxide film. The oxygen plasma irradiation conditions are an rf wave output of 900 W (0.45 W / cm ² ), a distance between electrodes of 12 mm, a pressure of 0.65 torr, and an oxygen flow rate of 3000 sccm. After evacuation for 15 seconds, hydrogen plasma is irradiated for 20 seconds. The hydrogen plasma conditions are an rf output of 100 W (0.05 W / cm ² ), a distance between electrodes of 25 mm, a pressure of 0.5 torr, and a hydrogen flow rate of 1400 sccm. A semiconductor film is deposited for 60 seconds continuously with hydrogen plasma. Deposition conditions are an rf output of 600 W (0.3 W / cm ² ), a distance between electrodes of 35 mm, a pressure of 1.5 torr, an argon flow rate of 14 SLM, and a monosilane flow rate of 200 sccm.

  As a result, an amorphous silicon film of approximately 50 nm is deposited. A vacuum is drawn for 15 seconds after the semiconductor film is deposited, and hydrogen plasma is irradiated for 20 seconds. The hydrogen plasma conditions are the same as the hydrogen plasma conditions before the semiconductor film deposition. Next, after vacuuming for 15 seconds, oxygen plasma is irradiated for 20 seconds. The oxygen plasma conditions are the same as the oxygen plasma conditions after the base protective film except that the distance between the electrodes is 45 mm. Finally, after evacuating for 15 seconds, the substrate is taken out of the film formation chamber in about 10 seconds. According to this process, the base protective film and the semiconductor film can be continuously formed in a tact time of 6 minutes and 10 seconds.

Thereafter, a thin film semiconductor device was formed by the same process as in Example 2.
When the transistor characteristics of the thin film semiconductor device manufactured in this way were measured, the ON current was ION = (19.6 + 1.54, −1.49) × 10 ⁻⁶ A with a 95% reliability coefficient, and the off current Was IOFF = (7.23 + 2.76, -2.72) × 10 ⁻¹³ A. The effective electron mobility is μ = 36.83 ± 2.35 cm ² / v. sec. The measurement conditions are in accordance with Example 1.

(Example 5)
Next, using the PECVD apparatus described in the section (2-11), a low temperature deposition method of about 350 ° C. or lower for a crystalline semiconductor film that does not require crystallization such as laser irradiation, and a thin film semiconductor using the same The method of manufacturing the device and its features will be described in detail. The substrate is prepared by the method described in the section (2-1). As the semiconductor film and the source gas, all the materials described in the section (2-2) are applicable, but here, a silicon film is taken as an example, and monosilane (SiH ₄ ) is used as a source gas.
In the fifth embodiment, 360 mm × 465 mm × 1.1 mm non-alkali glass (Nippon Electric Glass Co., Ltd. OA-2) is used as the substrate 101, and the base protective film is 2000 kg of SiOH using SiH ₄ and O ₂ as source gases by the APCVD method. _Two films were deposited. The substrate temperature was 300 ° C.
Next, an intrinsic silicon film to be an active layer of the thin film semiconductor device was deposited by about 750 mm.

Intrinsic silicon film is supplied with 50 sccm of monosilane (SiH ₄ ) as a source gas and 4800 sccm of argon (Ar), which is a kind of rare gas group element, as an additional gas in the VHS-PECVD apparatus described in (2-11) above. Flowed and deposited. The VHS wave output was 715 W, the reaction chamber pressure was 0.8 torr, the parallel plate electrode distance was 35.0 mm, the lower plate electrode temperature was 400 ° C., and the substrate surface temperature was 340 ° C.

The semiconductor film thus obtained is a high-purity silicon film and is in a polycrystalline state immediately after deposition (As-deposited state). When the crystallization rate was measured by multiwavelength dispersion type spectroscopic ellipsometry, the crystallization rate showed a value of 78%. If the crystallinity obtained by spectroscopic ellipsometry is less than 30%, it is in an amorphous state (amorphous state), and if it is 70% or more, it is in a polycrystalline state (poly-crystalline state), 30% to 70%. If it is between, it is considered to be a mixed crystal state (mixed state). Therefore, the obtained film is clearly in a polycrystalline state in the As-deposited state. In fact, a sharp Raman shift was detected in the wave number region near 520 cm ^−1, which shows the crystalline state, also by Raman spectroscopy, and it was confirmed that the X-ray diffraction method was relatively strongly oriented in the {220} direction.

Next, this silicon film was patterned to form a channel portion semiconductor film 103 which becomes an active layer of the transistor (FIG. 1A). Hereinafter, gate insulating film formation (FIG. 1B), gate electrode formation, source / drain regions and channel formation by ion implantation are performed in exactly the same manner as the manufacturing method of the thin film semiconductor device described in detail in Example 1 (FIG. 1C )), Through the formation of the interlayer insulating film, the activation of the implanted ions and the annealing of the interlayer insulating film, and the formation of the contact hole opening and the source / drain extraction electrode, the thin film semiconductor device is completed (FIG. 1D). ). Therefore, in Example 5, the maximum process temperature after the first process of forming the semiconductor film is 300 ° C.
The temperature of the heat treatment process for forming the gate insulating film and activating the implanted ions and baking the interlayer insulating film must be at most 350 ° C. or less. In other words, as described in detail in (2-10), a thin film semiconductor device excellent in that the process maximum temperature after the first process of forming a semiconductor film is 350 ° C. or less can be uniformly and stably in a large area. Indispensable for manufacturing.

When the transistor characteristics of the thin film semiconductor device fabricated in this way were measured, the source / drain current Ids when the transistor was turned on with the source / drain voltage Vds = 4V and the gate voltage Vgs = 10V was defined as the on-current ION. Thus, ION = (1.22 + 0.11, −0.10) × 10 ⁻⁶ A with a 95% reliability coefficient. The off-state current when the transistor was turned off at Vds = 4 V and Vgs = 0 V was IOFF = (1.18 + 0.35, −0.30) × 10 ⁻¹³ A. Here, the measurement was performed at a temperature of 25 ° C. for a transistor having a channel portion length L = 10 μm and a width W = 10 μm. The effective electron mobility (J. Levinson et al. J, Appl, Phys. 53 , 1193'82) determined from the saturation current region is μ = 3.41 ± 0.22 cm ² / v. sec.

  The maximum process temperature in Example 5 was 400 ° C. of the lower plate electrode temperature when the semiconductor film was formed by the VHS-PECVD apparatus, and the substrate surface temperature at that time was 340 ° C. As shown in this example, a poly-Si TFT, which is a kind of crystalline thin-film semiconductor device, has been successfully produced by a simple manufacturing method that does not require crystallization such as laser irradiation at an extremely low process temperature. The values of on-current and mobility are not far from those of Example 1 using laser irradiation, but are nearly 4 to 10 times that of an a-Si TFT which is conventionally manufactured at a process maximum temperature of about 400 ° C. High value.

  In the fifth embodiment, source / drain regions are formed by ion implantation using the gate electrode as a mask. Moreover, since the implanted ions are activated at a low temperature of 300 ° C. to 350 ° C., the implanted ions from the source / drain regions to the channel region are substantially not diffused at all. Therefore, the overlap between the gate electrode and the source / drain regions is determined by the lateral range deviation during ion implantation, and the value is several hundreds of m or less. That is, a so-called self-aligned structure in which the gate electrode end and the source / drain end are in good agreement. Therefore, the parasitic capacitance between the source and gate and between the drain and gate is extremely small as compared with the a-Si TFT. Due to these two facts, when the thin film semiconductor device of the present invention is used as a pixel switching element of an active matrix type liquid crystal display device (LCD), a high-definition LCD (having the number of pixels which cannot be achieved by conventional a-Si TFTs). Many LCDs), bright LCDs (LCDs with a high aperture ratio with reduced or eliminated additional capacitance) or highly integrated LCDs (LCDs with a large number of pixels per unit area) can be easily realized.

(Example 6)
Next, a microwave PECVD apparatus is used to describe in detail the low-temperature deposition method of a crystalline semiconductor film of about 350 ° C. or lower, which does not require crystallization such as laser irradiation, and the manufacturing method and characteristics of a thin film semiconductor device using the same. To do. The substrate is prepared by the method described in the section (2-1). As the semiconductor film and the source gas, all the materials described in the section (2-2) can be applied. Here, a silicon film is taken as an example, and monosilane (SiH ₄ ) is used as a source gas.

In Example 6, non-alkali glass (Nippon Electric Glass Co., Ltd. OA-2) of 300 mm × 300 mm × 1.1 mm is used as the substrate 101, and the base protective film and the semiconductor film are ECR-PECVD which is a kind of microwave PECVD method apparatus. Continuous film formation was performed at a substrate temperature of 100 ° C. using an apparatus. The microwave used was 2.45 GHz. The silicon oxide film, which is a base protective film, was deposited to 200 nm using SiH ₄ and O ₂ as source gases. The deposition conditions for the undercoat protective film were an oxygen flow rate of 100 sccm, a silane flow rate of 60 sccm, a microwave output of 2250 w, a reaction chamber pressure of 2.35 mtorr, and a deposition rate of 8.0 nm / s. After the formation of the silicon oxide film, supply of silane to the film formation chamber was stopped, and oxygen plasma irradiation was continuously performed for 10 seconds.

The pressure during oxygen plasma irradiation was 1.85 mtorr. Next, after evacuating for 10 seconds, the undercoat protective film was irradiated with hydrogen plasma under the conditions of a hydrogen flow rate of 100 sccm, a microwave output of 2000 w, and a reaction chamber pressure of 1.97 mtorr. Further, an intrinsic silicon film which becomes an active layer of a thin film semiconductor device was continuously deposited to about 75 nm without breaking the vacuum. A source gas, monosilane (SiH ₄ ), was flowed at 25 sccm, and an additional gas, argon (Ar), a kind of rare gas group element, was flowed at 825 sccm for deposition. The microwave output was 2250 W, the reaction chamber pressure was 13.0 mtorr, and the deposition rate was 2.5 nm / s. After the semiconductor film was deposited, hydrogen plasma irradiation and oxygen plasma irradiation were again performed again for the purpose of protecting the surface of the semiconductor film and terminating unreacted pairs in the semiconductor film. Irradiation conditions of hydrogen plasma and oxygen plasma are the same as those applied to the base protective film. The semiconductor film thus obtained is a high-purity silicon film and is in a polycrystalline state immediately after deposition (As-deposited state). When the crystallization rate was measured by multi-wavelength dispersion type spectroscopic ellipsometry, the crystallization rate showed a value of 85%.

  Next, this silicon film was patterned to form a channel portion semiconductor film 103 which becomes an active layer of the transistor (FIG. 1A). Hereinafter, the gate insulating film formation (FIG. 1B), gate electrode formation, source / drain regions and channel formation by ion implantation are performed in exactly the same manner as the method of manufacturing the thin film semiconductor device described in detail in Example 1 (FIG. 1C). )), Through the formation of the interlayer insulating film, the activation of the implanted ions and the annealing of the interlayer insulating film, the formation of the contact hole opening and the source / drain extraction electrode, the thin film semiconductor device is completed (FIG. 1D). ). Therefore, in Example 6, the maximum temperature throughout the entire process is 300 ° C.

When the transistor characteristics of the thin film semiconductor device manufactured in this way were measured, the ON current was ION = (1.71 + 0.13, −0.12) × 10 ⁻⁶ A with a 95% reliability coefficient, and the off current Was IOFF = (1.07 + 0.33, −0.28) × 10 ⁻¹³ A. The effective electron mobility is μ = 4.68 ± 0.20 cm ² / v. sec. The measurement conditions are in accordance with Example 1. According to the present invention, a poly-Si TFT can be manufactured by performing all steps at about 300 ° C. or less without particularly introducing a crystallization step.

(Example 7)
In this embodiment, laser irradiation is performed on a semiconductor film obtained by the VHS-PECVD method to perform melt crystallization to produce a thin film semiconductor device. The manufacturing process is a product obtained by adding a laser irradiation step immediately after the semiconductor film is deposited in Example 5. Further, the laser irradiation method is the laser irradiation method shown in Example 1, in which the first laser irradiation energy density is changed to 130 mJ / cm ² and the second laser irradiation energy density is changed to 240 mJ / cm ^2. is there.

When the transistor characteristics of the thin film semiconductor device manufactured in this way were measured, the ON current was ION = (22.4 + 1.70, −1.55) × 10 ⁻⁶ A with a 95% reliability coefficient, and the off current Was IOF = (1.27 + 0.30, −0.26) × 10 ⁻¹² A. The effective electron mobility is μ = 47.95 ± 3.13 cm ² / v. sec. The measurement conditions are in accordance with Example 1.

(Example 8)
In this embodiment, laser irradiation is performed on a semiconductor film obtained by a microwave-PECVD method to perform melt crystallization to produce a thin film semiconductor device. The manufacturing process is a product obtained by adding a laser irradiation step to Example 6 immediately after the semiconductor film is deposited. Also, the laser irradiation method is the laser irradiation method shown in Example 1, with the first laser irradiation energy density changed to 150 mJ / cm ² and the second laser irradiation energy density changed to 270 mJ / cm ^2. is there.

When the transistor characteristics of the thin film semiconductor device manufactured in this way were measured, the ON current was ION = (39.8 + 2.45, −1.57) × 10 ⁻⁶ A with a 95% reliability coefficient, and the off current Was IOFF = (5.80 + 2.09, −1.26) × 10 ⁻¹³ A. The effective electron mobility is μ = 85.63 ± 4.38 cm ² / v. sec. The measurement conditions are in accordance with Example 1.

Example 9
An active matrix substrate was manufactured using the various thin film semiconductor devices obtained in the above-described embodiments as pixel TFTs and drive circuit TFTs. A liquid crystal panel using the obtained active matrix substrate as one of the substrates was manufactured. When the liquid crystal display module was manufactured together with the external peripheral drive circuit and backlight unit from the obtained liquid crystal panel, the performance of the TFT itself was high, and the manufacturing process was stable. A high liquid crystal display device could be stably manufactured at low cost. In addition, since the TFT performance is extremely high and the necessary drive circuit can be formed on the active matrix substrate (with built-in driver), the mounting structure with the external peripheral drive circuit is simplified, and a small and lightweight liquid crystal display device is obtained. I was able to.

In addition, when such a liquid crystal display device was incorporated into the casing of a full-color notebook PC, a full-color notebook PC having a small size and light weight and good display quality could be manufactured at low cost.
INDUSTRIAL APPLICABILITY As described above, according to the method for manufacturing a thin film semiconductor device of the present invention, a high performance thin film semiconductor device can be manufactured using a low temperature process that allows the use of an inexpensive glass substrate. . Therefore, when the present invention is applied to the production of an active matrix liquid crystal display device, a large and high quality liquid crystal display device can be produced easily and stably. Further, even when applied to the manufacture of other electronic circuits, a high-quality electronic circuit can be easily and stably manufactured.

  Further, since the thin film semiconductor device of the present invention is inexpensive and has high performance, it is optimal as an active matrix substrate for an active matrix liquid crystal display device. In particular, it is optimal as an active matrix substrate with a built-in driver that requires high performance.

Further, since the liquid crystal display device of the present invention is inexpensive and has high performance, it is optimal for various displays including full-color notebook PCs.
In addition, the electronic device of the present invention is generally widely accepted because it is inexpensive and has high performance.

Manufacturing process of thin film semiconductor device of the present invention VHS-plasma chemical vapor deposition apparatus (VHS-PECVD apparatus) used in the present invention Hot wall type vertical LPCVD apparatus used in the present invention Normal hot wall type vertical LPCVD equipment Relationship between the pressure P in the film forming chamber, the exhaust speed S of the film forming chamber, and the gas flow rate Q

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Substrate 102 ... Base protective film 103 ... Semiconductor film 104 ... Gate insulating film 105 ... Gate electrode 106 ... Impurity ion 107 ... Source / drain region 108 ... Channel Region 109 ... Interlayer insulating film 110 ... Source / drain extraction electrode

Claims (64)

A thin film semiconductor device having a substrate provided with a base protective film which is an insulating material on at least a part of the substrate surface, and a semiconductor film formed on the base protective film of the substrate and forming an active layer of a transistor The base protective film has a surface roughness of 3.0 nm or less in terms of center line average roughness. 2. The thin film semiconductor device according to claim 1, wherein the undercoat protective film has a surface roughness of 1.5 nm or less in terms of center line average roughness. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. A step having a first step of forming a semiconductor film on a base protective film having a surface roughness of 1.5 nm or less in terms of center line average roughness, and a second step of melt crystallization of the semiconductor film A method for manufacturing a thin film semiconductor device, comprising: A thin film semiconductor device having a substrate provided with a base protective film which is an insulating material on at least a part of the substrate surface, and a semiconductor film formed on the base protective film of the substrate and forming an active layer of a transistor The undercoat protective film is a laminated film in which at least two different films are laminated, and the uppermost film of the two different films is silicon oxide (SiO _x , 0 <x ≦ 2 A thin film semiconductor device characterized by being a film. 5. The thin film semiconductor device according to claim 4, wherein the lower layer of the two different types of films is a silicon nitride (Si ₃ N _x , 0 <x ≦ 4) film. 6. The thin film semiconductor device according to claim 5, wherein the film thickness of the silicon oxide film is between 100 nm and 500 nm, and the film thickness of the silicon nitride film is between 50 nm and 500 nm. A substrate provided with a base protective film that is an insulating material on at least a part of the substrate surface, a field effect transistor having a semiconductor film, a gate insulating film, and a gate electrode formed on the base protective film of the substrate; In a thin film semiconductor device having an interlayer insulating film that takes electrical insulation between wirings of the field effect transistor, the film thickness of the base protective film, the film thickness of the gate insulating film, and the film of the interlayer insulating film A thin film semiconductor device having a sum of thickness and 2 μm or less. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. A film forming step of continuously forming the base protective film and the semiconductor film by a single PECVD apparatus, the first step removing a thin film adhering to the film forming chamber of the PECVD apparatus; A second step of depositing a passivation film in the deposition chamber; a third step of installing a substrate in the deposition chamber; a fourth step of depositing a base protection film on the substrate; A method of manufacturing a thin film semiconductor device, comprising: a film forming step including: a fifth step of forming a semiconductor film; and a sixth step of taking out the substrate from the film formation chamber. A base protective film which is an insulating material is provided on at least a part of the substrate surface of a substrate having a substrate area (S) of 90000 mm ² or more, and a semiconductor film is formed over the base protective film. In a method of manufacturing a thin film semiconductor device as an active layer, when a plurality of substrates are placed in a film formation chamber of an LPCVD apparatus and the semiconductor film is formed by LPCVD, the substrate interval in the LPCVD apparatus film formation chamber is set to ( d (mm)), a method for manufacturing a thin film semiconductor device, comprising a step of forming a semiconductor film under conditions satisfying a relational expression of d ≧ 0.02 × S ^1/2 . Manufacturing a thin film semiconductor device in which a base protective film which is an insulating material is provided on at least a part of a substrate surface, a semiconductor film containing silicon is formed on the base protective film, and the semiconductor film is used as an active layer of a transistor In the method, the semiconductor film is formed by LPCVD using high order silane (Si _n H _{2n + 2} : n is an integer of 2 or more) as a source gas, and the high order silane flow rate (R) per unit area is 1. A method of manufacturing a thin film semiconductor device comprising a step of forming a semiconductor film under a condition of 1.13 × 10 ⁻³ sccm / cm ² or more. 11. The method of manufacturing a thin film semiconductor device according to claim 10, further comprising a step of forming a semiconductor film under a condition that R is 2.27 × 10 ⁻³ sccm / cm ² or more. Manufacturing a thin film semiconductor device in which a base protective film which is an insulating material is provided on at least a part of a substrate surface, a semiconductor film containing silicon is formed on the base protective film, and the semiconductor film is used as an active layer of a transistor In the method, the semiconductor film is formed by LPCVD using a deposition temperature of less than 450 ° C. and using high-order silane (Si _n H _{2n + 2,} n is an integer of 2 or more) as at least one kind of source gas, In that case, the manufacturing method of the thin film semiconductor device which has the process of forming a semiconductor film on the conditions whose deposition rate (DR) of a semiconductor film is 0.20 nm / min or more. 13. The method of manufacturing a thin film semiconductor device according to claim 12, further comprising a step of forming a semiconductor film under a condition where DR is 0.60 nm / min or more. A thin film semiconductor device having a substrate provided with a base protective film which is an insulating material on at least a part of the substrate surface, and a semiconductor film formed on the base protective film of the substrate and forming an active layer of a transistor The semiconductor film is a semiconductor film formed by being crystallized after being deposited by LPCVD with a deposition temperature of less than 450 ° C. and having a thickness of 10 nm to 140 nm. There is a thin film semiconductor device. In a method of manufacturing a thin film semiconductor device in which a semiconductor film is formed at least on the surface of a glass substrate, and the semiconductor film is used as an active layer of a transistor, the semiconductor film is formed by a hot wall type vertical LPCVD apparatus, In the hot wall type vertical LPCVD apparatus, at least two or more types of glass substrates having different strain points are set as two sets, and the back surfaces thereof are aligned and set substantially horizontally. A method for manufacturing a thin film semiconductor device, comprising: a film forming step of depositing a semiconductor film with a glass substrate having a larger strain point on a lower side of the glass substrate. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. A first step of irradiating the base protective film with oxygen plasma, and a step of continuously forming a semiconductor film on the base protective film without breaking a vacuum. A method for manufacturing a thin film semiconductor device, comprising: a film forming step including two steps. 17. The method for manufacturing a thin film semiconductor device according to claim 16, wherein the film forming chamber is evacuated between the first step and the second step. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. The semiconductor film is formed by a PECVD apparatus, and at that time, the first step of irradiating the base protective film with hydrogen plasma, and the semiconductor film is continuously formed on the base protective film without breaking the vacuum. A method for manufacturing a thin film semiconductor device, comprising: a film forming step including two steps. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. A first step of depositing the semiconductor film with a PECVD apparatus, and irradiating the base protective film with oxygen plasma, and a second step of continuously irradiating the base protective film with hydrogen plasma without breaking the vacuum; And a third step of forming a semiconductor film on the base protective film continuously without breaking a vacuum, and a method of manufacturing a thin film semiconductor device, comprising: 20. The method for manufacturing a thin film semiconductor device according to claim 19, wherein the film forming chamber is evacuated between the first step and the second step. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film soil, and the semiconductor film is used as an active layer of a transistor. A first step of forming the semiconductor film by a PECVD apparatus, and forming a semiconductor film on the underlying protective film soil; and a first step of irradiating the semiconductor film with hydrogen plasma without breaking the vacuum. A method for manufacturing a thin film semiconductor device, comprising: a film forming step including two steps. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film soil, and the semiconductor film is used as an active layer of a transistor. A first step of forming the semiconductor film by a PECVD apparatus, and forming a semiconductor film on the undercoat protective film; and a step of irradiating the semiconductor film with oxygen plasma continuously without breaking a vacuum. A method for manufacturing a thin film semiconductor device, comprising: a film forming step including two steps. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. A first step of forming the semiconductor film by a PECVD apparatus, and forming a semiconductor film on the undercoat protective film, and a first step of irradiating the semiconductor film with hydrogen plasma continuously without breaking a vacuum. A method of manufacturing a thin film semiconductor device, comprising: a film forming step including two steps and a third step of continuously irradiating the semiconductor film with oxygen plasma without breaking a vacuum. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. A first step of forming a semiconductor film on the base protective film; a second step of removing the oxide film from the surface of the semiconductor film; a third step of melt crystallization of the semiconductor film immediately after the removal of the oxide film; A method for manufacturing a thin film semiconductor device, comprising: In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. And a first step of forming a mixed crystal semiconductor film under a condition of a deposition rate of about 0.1 nm / s or more by PECVD, and a second step of melt crystallization of the semiconductor film. A method of manufacturing a thin film semiconductor device. 26. The thin film semiconductor device according to claim 25, wherein the first step is a step of forming a mixed crystal semiconductor film under a condition where the deposition rate is about 3.7 nm / s or more. Manufacturing method. In a method of manufacturing a thin film semiconductor device, a base protective film that is an insulating material is provided on at least a part of a substrate surface, a semiconductor film is further formed on the base protective film, and the semiconductor film is used as an active layer of a transistor. The flow rate ratio of the flow rate of the chemical substance gas containing the constituent elements of the semiconductor film to the flow rate of the inert gas gas is set to 1/33. Manufacturing a thin film semiconductor device comprising: a first step of forming a mixed crystal semiconductor film by PECVD under a condition of less than a second step; and a second step of melt crystallization of the semiconductor film. Method. The first step is a step of forming a mixed crystal semiconductor film by PECVD under a condition in which the flow rate ratio is between 1/124 and 40.67 / 1. 28. A method of manufacturing a thin film semiconductor device according to item 27. A thin film semiconductor device having a substrate provided with a base protective film which is an insulating material on at least a part of the substrate surface, and a semiconductor film formed on the base protective film of the substrate and forming an active layer of a transistor The semiconductor film is a semiconductor film formed by PECVD and then crystallized, and is a semiconductor film having a thickness of 9 nm to 135 nm. apparatus. In a method of manufacturing a thin film semiconductor device, a semiconductor film is formed on an insulating material of a substrate having at least a part of the surface being an insulating material, and the semiconductor film is used as an active layer of a transistor. A first step of depositing a semiconductor film at a deposition temperature of less than 450 ° C. by a method (LPCVD method), and a second step of irradiating the semiconductor film with optical energy or electromagnetic energy, and the second step A method of manufacturing a thin film semiconductor device, wherein the maximum process temperature after the end of the process is 350 ° C. or lower. 31. The method of manufacturing a thin film semiconductor device according to claim 30, wherein the first step is a step of depositing a semiconductor film at a deposition temperature of 430 ° C. or lower. In a method of manufacturing a thin film semiconductor device in which a semiconductor film is formed on an insulating material of a substrate having at least a part of an insulating material, and the semiconductor film is used as an active layer of a transistor, a deposition temperature of 350 ° C. or lower And a second step of irradiating the semiconductor film with optical energy or electromagnetic energy, and a maximum process temperature after the end of the second step is 350 ° C. or lower. A method for manufacturing a thin film semiconductor device, comprising: The method of manufacturing a thin film semiconductor device according to claim 32, wherein the first step is performed by a plasma enhanced chemical vapor deposition method (PECVD method). The method of manufacturing a thin film semiconductor device according to claim 32, wherein the first step is performed by a sputtering method. In a method of manufacturing a thin film semiconductor device in which a semiconductor film is formed on an insulating material of a substrate whose surface is at least a part of an insulating material, and the semiconductor film is used as an active layer of a transistor, a VHF plasma chemical vapor phase A thin-film semiconductor device having a first step of forming a semiconductor film by a deposition method (VHF-PECVD method), and having a maximum process temperature of 350 ° C. or lower after the end of the first step Method. 36. The method of manufacturing a thin film semiconductor device according to claim 35, wherein when the semiconductor film is formed in the first step, the film thickness of the semiconductor film is between 20 nm and 150 nm. 36. When the semiconductor film is formed by the first step, a chemical substance containing a constituent element of the semiconductor film is used as a raw material gas, and a rare gas group element is used as an additional gas. Item 37. A method for manufacturing a thin film semiconductor device according to Item 36. 38. The method of manufacturing a thin film semiconductor device according to claim 37, wherein the chemical substance containing the constituent element of the semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ). 39. A method of manufacturing a thin film semiconductor device according to claim 37 or 38, wherein the rare gas group element is helium (He). 39. A method of manufacturing a thin film semiconductor device according to claim 37 or 38, wherein the rare gas group element is neon (Ne). 39. The method of manufacturing a thin film semiconductor device according to claim 37 or 38, wherein the rare gas group element is argon (Ar). In a method of manufacturing a thin film semiconductor device, a crystalline semiconductor film is formed on an insulating material of a substrate whose surface is an insulating material, and the crystalline semiconductor film is used as an active layer of a transistor. A first step of forming a crystalline semiconductor film by a wave plasma chemical vapor deposition method (microwave-PECVD method), and a maximum process temperature after the first step is 350 ° C. or lower. A method for manufacturing a thin film semiconductor device. 43. The method of manufacturing a thin film semiconductor device according to claim 42, wherein when the crystalline semiconductor film is formed in the first step, the thickness of the crystalline semiconductor film is set between 20 nm and 150 nm. . The crystalline semiconductor film is formed in the first step, a chemical substance containing a constituent element of the crystalline semiconductor film is used as a source gas, and a rare gas group element is used as an additional gas. 44. A method of manufacturing a thin film semiconductor device according to item 42 or 43. 45. The method of manufacturing a thin film semiconductor device according to claim 44, wherein the chemical substance containing the constituent element of the crystalline semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ). Method. 46. The method of manufacturing a thin film semiconductor device according to claim 44, wherein the rare gas group element is helium (He). 46. The method of manufacturing a thin film semiconductor device according to claim 44, wherein the rare gas group element is neon (Ne). 46. The method for manufacturing a thin film semiconductor device according to claim 44, wherein the rare gas group element is argon (Ar). In a method of manufacturing a thin film semiconductor device in which a semiconductor film is formed on the insulating material soil of a substrate whose surface is at least a part of an insulating material, and the semiconductor film is used as an active layer of a transistor, a VHF plasma chemical vapor phase is provided. A first step of forming a semiconductor film by a deposition method (VHF-PECVD method), and a second step of crystallizing the semiconductor film, and a maximum process temperature after the second step is 350 ° C. or lower. A method for manufacturing a thin film semiconductor device, comprising: 50. The method of manufacturing a thin film semiconductor device according to claim 49, wherein the thickness of the semiconductor film crystallized in the second step is between 10 nm and 150 nm. 50. The semiconductor device according to claim 49, wherein when forming the semiconductor film in the first step, a chemical substance containing a constituent element of the semiconductor film is used as a source gas, and a rare gas group element is used as an additional gas. Or the manufacturing method of the thin film semiconductor device of 50th term | claim. Method of manufacturing a thin film semiconductor device according to a range Section 51 claims, characterized in that chemical substances containing the structural element of the semiconductor film is a silane _{(SiH 4, Si 2 H 6} , Si 3 H 8). 53. The method of manufacturing a thin film semiconductor device according to claim 51, wherein the rare gas group element is helium (He). 53. The method of manufacturing a thin film semiconductor device according to claim 51, wherein the rare gas group element is neon (Ne). 53. The method of manufacturing a thin film semiconductor device according to claim 51, wherein the rare gas group element is argon (Ar). In a method of manufacturing a thin film semiconductor device, a crystalline semiconductor film is formed on an insulating material of a substrate whose surface is an insulating material, and the crystalline semiconductor film is used as an active layer of a transistor. A first step of forming a semiconductor film by a microwave plasma chemical vapor deposition method (microwave-PECVD method) and a second step of crystallizing the semiconductor film, and the highest step after the second step A method for manufacturing a thin film semiconductor device, wherein the temperature is 350 ° C. or lower. 57. The method of manufacturing a thin film semiconductor device according to claim 56, wherein the thickness of the semiconductor film crystallized in the second step is between 10 nm and 150 nm. The crystalline semiconductor film is formed in the first step, a chemical substance containing a constituent element of the crystalline semiconductor film is used as a source gas, and a rare gas group element is used as an additional gas. 58. A method of manufacturing a thin film semiconductor device according to item 56 or 57. 59. A method of manufacturing a thin film semiconductor device according to claim 58, wherein the chemical substance containing the constituent element of the crystalline semiconductor film is silane (SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ). . 60. The method of manufacturing a thin film semiconductor device according to claim 58, wherein the rare gas group element is helium (He). 60. The method of manufacturing a thin film semiconductor device according to claim 58 or 59, wherein the rare gas group element is neon (Ne). 60. The method of manufacturing a thin film semiconductor device according to claim 58, wherein the rare gas group element is argon (Ar). A thin film semiconductor device according to any one of claims 1, 2, 4, 5, 6, 7, 14, and 29 is provided. A liquid crystal display device. An electronic apparatus comprising the liquid crystal display device according to claim 63.

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