JP3141909B2 - Semiconductor device manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device such as a TFT provided on an insulating substrate.

[0002]

2. Description of the Related Art A large number of TFTs are formed on a glass substrate,
Active type liquid crystal display devices using these TFTs for driving pixels, image sensors using TFTs on a glass substrate, and the like are known.

In general, a thin film silicon semiconductor is used for a TFT (insulating gate type field effect transistor using a thin film semiconductor) used in these devices. It is common to use amorphous silicon (a-Si), which can be relatively easily formed by a gas phase method, as a thin-film silicon semiconductor. It is useful to use a silicon semiconductor thin film having the following. Known crystalline silicon semiconductor thin films include polycrystalline silicon, microcrystalline silicon, amorphous silicon containing a crystalline component, and semi-amorphous silicon having an intermediate state between crystalline and amorphous.

As a method of obtaining a silicon semiconductor in the form of a thin film having crystallinity, (1) a film having crystallinity is directly formed at the time of film formation. (2) An amorphous semiconductor film is formed in advance, and crystallinity is imparted by laser light energy. (3) An amorphous semiconductor film is formed and crystallinity is imparted by applying thermal energy. The methods taken are known. However, the method (1) has a problem in that a film having good physical properties is uniformly formed.In addition, since the film formation temperature is as high as 600 ° C. or more, there is a problem in forming a film on a glass substrate. there were. Further, the method (2) has a problem in productivity because the irradiation area of the laser beam is small, and also has a problem that it cannot cope with a large-area substrate. In addition, the method (3) has the advantage that it can be applied to a large area.However, it is necessary to set the heating temperature to 600 ° C or higher. It was necessary to lower the temperature. Furthermore, since the heating time is several tens of hours or more, it is necessary to further shorten the time.

[0005]

In view of the above problems, the present invention provides: In the method of crystallization by heating, the heating temperature is reduced and the heating time is shortened. 2. A crystalline silicon semiconductor thin film having good electrical characteristics is obtained. It is an object to obtain a silicon semiconductor thin film having crystallinity satisfying the above.

Background of the Invention The present inventors form an amorphous silicon semiconductor film by a CVD method or a sputtering method and crystallize the film by heating as described in the section of the prior art. The method was considered as follows.

First, as an experimental fact, an amorphous silicon film is formed on a glass substrate, and the mechanism of crystallizing the film by heating is examined. The crystal growth starts from the interface between the glass substrate and the amorphous silicon. It is recognized that the particles progress in a column shape perpendicular to the substrate surface.

The above phenomenon is considered to be due to the existence of crystal nuclei (seeds serving as a base for crystal growth) at the interface between the glass substrate and the amorphous silicon film. It is considered that such crystal nuclei include a metal element present in a trace amount on the substrate surface and a crystal component on the glass surface (as is called crystallized glass, a crystal component of silicon oxide exists on the glass substrate surface). Is considered to be).

On the other hand, the surface is etched so that no crystal nuclei are present on the substrate, and furthermore, an amorphous silicon oxide substrate is used in which attention is paid to the contamination of the surface. When crystalline silicon is formed and the film is crystallized by heating, crystallization can be performed in a short time or at a low temperature as compared with the case where the film is formed on an ordinary glass substrate. A crystalline silicon film having high properties and excellent electrical characteristics was obtained.

When an amorphous silicon film formed by plasma CVD on a substrate (Corning 9059) on which no processing is performed is crystallized by heating in a nitrogen atmosphere, the heating temperature is set to 600 ° C. , Heating time as 10
Although a longer time was required, a similar crystallization state could be obtained by heating for about 4 hours when using the amorphous silicon oxide substrate that had been subjected to the above treatment. The crystallization at this time was determined using Raman spectroscopy.

When a glass substrate was used with a heating time of 10 hours, there was almost no change at 580 ° C., but when the amorphous silicon substrate was used, the heating time was 10 hours. Was able to be crystallized. However, the experiment using the amorphous silicon oxide substrate was performed with great care so as to prevent impurities from being present on the surface, and is not practical.

Considering the above experimental facts, the crystal component of the substrate material and the crystal component in the semiconductor film existing in the substrate and near the interface of the semiconductor film can serve as nuclei for crystal growth. In order to do so, it can be considered that it acts as a negative factor. In other words, it can be considered that it is not preferable that a crystal component is present in advance in crystallization.

According to the present invention, based on the above experimental results, when an amorphous silicon semiconductor film on a substrate is crystallized by heating, a component serving as a crystal nucleus is present at an interface between the substrate and the amorphous silicon film;
In particular, a crystalline component in the vicinity of the substrate surface or a crystalline component in the amorphous silicon film near the interface with the substrate (even though it is an amorphous matter, the crystalline component may be observed when observed in detail. ) Need to be absent.

[0014]

Means for Solving the Problems [First invention] According to a first invention, as described in claim 1, a step of forming a non-single-crystal semiconductor film on a substrate; A step of implanting inactive element ions from the semiconductor film toward the substrate such that a region where the distribution of the ions has a maximum value is present in the substrate; and a non-single crystal into which the ions are implanted. And a step of crystallizing the semiconductor film by heating.

In the first aspect, the substrate may be
Examples of the insulating substrate include a glass substrate and a quartz substrate, which are insulating substrates, and a semiconductor substrate. As the non-single-crystal semiconductor film, amorphous, microcrystalline,
Semiconductors such as polycrystalline and semi-amorphous can be given. Furthermore, other semiconductor materials can be used.

An inert element refers to an element that does not adversely affect a non-single-crystal semiconductor film into which ions are implanted. For example, when an amorphous silicon semiconductor film is used as the non-single-crystal semiconductor film, silicon or germanium is used as the inactive element, and silicon such as phosphorus or boron is used if the semiconductor film is allowed to be of one conductivity type. On the other hand, an element giving one conductivity type can be used.

The vicinity of the interface between the substrate and the semiconductor film is defined as
This means the region adjacent to the interface between the substrate and the semiconductor film on the substrate, on both sides thereof, that is, the region near the substrate and the semiconductor film on the interface.

Amorphizing a semiconductor film by implanting ions of an inert element into the semiconductor film is generally well known in the art. This utilizes the phenomenon of crystallinity. Since the amorphization also has the meaning of further promoting the amorphization, an effect of amorphizing a crystal component in the amorphous semiconductor film by performing it on the amorphous semiconductor film is given. Has. (In general, a crystalline component and a microcrystal structure are present in a film formed by a vapor phase method or the like as an amorphous semiconductor film.)

Heating and crystallizing the semiconductor film means that heat energy is applied to the amorphous semiconductor film to promote crystallization and produce a semiconductor film having a crystalline component or crystallinity. To do. When general amorphous silicon is crystallized by heating, at least 60
It has been experimentally found that heating at a temperature of about 0 ° C. for 24 to 48 hours is necessary. However, in the present invention, when amorphous silicon is used as the non-single-crystal semiconductor, 550
By heating at 5 ° C. for 5 hours, crystallization similar to the above-described conventional case can be performed.

[0020]

In the first aspect of the present invention, the meaning that the ions of the inactive element are implanted mainly in the substrate will be described below. Generally, when ions are implanted into the material by ion implantation, the implanted ions exist with a certain distribution in the depth direction. This distribution is called a range distribution. The first invention is characterized in that the ions are implanted such that the maximum value of the distribution of the implanted ions is present in the substrate.

FIG. 2 shows an example of this. In FIG. 2, the left side of the dotted line is the substrate side, and the right side of the dotted line is the semiconductor film side into which ions are implanted. The vicinity of both sides of the dotted line is the vicinity of the interface between the substrate and the semiconductor film. In this case, the maximum value of the range distribution of the implanted ions (the region where the most implanted ions exist) is in the substrate. That is, a state where ions are implanted mainly in the substrate is shown.

[Second Invention] According to a second invention, as described in claim 2, a step of forming a non-single-crystal semiconductor film on a substrate; Implanting ions of selectively inactive elements in the substrate such that a region where the distribution of the ions has the maximum value is present in the substrate; and heating, the inactivation of the non-single-crystal semiconductor film. Forming a region into which ions of an element are implanted from a region into which ions of an inert element are not implanted.

According to the second aspect of the present invention, the non-single-crystal semiconductor film is selectively implanted with inactive ions to perform heat treatment when the ion-implanted region is made amorphous. Crystal growth from the non-amorphized region (even if formed as an amorphous semiconductor film, a crystalline component remains unless amorphization by ion implantation is performed) Occurs toward the amorphized region, and a crystalline semiconductor film can be obtained in which the crystal is grown in the planar direction of the film.

[Third invention] According to a third invention, a first invention is provided.
In the second invention, the ions of the inert element are implanted mainly in the substrate, and the dose is 3 × 10 ¹⁴ cm ^{−2 to} 3 × 10 ¹⁵ cm ^−2. It is an abstract.

[0026]

Note that the present invention improves the effect of crystallization by heating by eliminating crystal components near the interface between the substrate and the semiconductor film. Also, after eliminating the crystal component near the interface between the substrate and the semiconductor film, a material that becomes a crystal growth nucleus is artificially introduced,
A method of growing crystals using the material as a nucleus may be used.

[0028]

By making the surface of the glass substrate amorphous, it is possible to eliminate a crystal component that hinders uniform crystal growth, and to form a crystalline semiconductor thin film that satisfies electrical characteristics by crystallization by heating. You can get it. Further, the heating temperature during crystallization can be reduced, and the heating time can be shortened.

[0029]

[Embodiment 1] This embodiment is an embodiment of the first invention, in which an N-channel TFT or a P-type TFT is formed on a glass substrate (Corning 7059).
This is an example of a case where a channel type TFT is formed. This embodiment can be applied to a liquid crystal display device and an image sensor using a TFT formed on a glass substrate, and further to an integrated circuit formed on an insulating substrate.

The manufacturing process of this embodiment will be described with reference to FIGS. In FIG. 1, (11) is a Corning 70 which is an insulating substrate.
59 glass substrates. First, a silicon oxide film (12) is formed as a base oxide film on a glass substrate to a thickness of 3000 mm by a sputtering method. Of course, the underlying silicon oxide film (12) may not be provided. Next, the amorphous silicon film (13) is
The film is formed to a thickness of 1500 mm by the method. The film formation method may be a thermal CVD method or a sputtering method. Further, a film having crystallinity, for example, a microcrystalline silicon film or a polycrystalline silicon film may be formed as the amorphous silicon film (13).

Since the amorphous silicon film (13) is crystallized by heating later, it is important to minimize the incorporation of an oxygen element which is an element that inhibits crystallization during film formation.

Next, a silicon ion (Si ⁺ ), which is an electrically inactive element, is ion-implanted into the silicon semiconductor by an ion implantation method, and the amorphous silicon semiconductor film (13) is made amorphous. (It can also be said to promote amorphization).
At this time, the acceleration voltage and dose for implanting silicon ions are determined as follows.

First, the implantation of silicon ions causes the vicinity of the surface of the glass substrate (11) and the underlying silicon oxide film (12) to become amorphous, and there exists a crystal component which is considered to inhibit crystallization in these regions. It is something not to do. That is,
Focusing on the fact that crystal growth by heating occurs from the interface between the substrate (in this case, including the underlying silicon oxide film) and the semiconductor film to be crystallized, the crystallinity of which is uniform and has excellent electrical characteristics In order to obtain a semiconductor film, a crystal component near the interface, which acts as a negative factor in crystallization, is removed. The crystal component that inhibits the crystallization is a crystal component of silicon oxide present in the glass substrate (11), a crystal component of silicon oxide present in the base silicon oxide film (12), an amorphous semiconductor film ( 13) Refers to the crystal components present in

The conditions for implanting silicon ions were such that the dose was as shown in FIG. FIG. 2 shows the dose amount on the vertical axis and the position of the implanted ions (the position in the depth direction of the ions from the implanted surface) on the horizontal axis, and the substrate ( 11) side (silicon oxide film (12)
The right side of the dotted line is the side of the amorphous silicon film (13) which is the starting film. In this embodiment, the dose is set to 5 × 10 ¹⁴ cm ⁻² , but 3 × 10 ¹⁴ cm ^{−2 to} 3 × 10 ^15.
It is possible in the range of cm ^-2 . Of course, it seems that other values are possible.

Amorphization near the interface between the substrate and the semiconductor to be crystallized is necessary for good crystal growth. In addition, as a result of the implantation of silicon ions, no crystal component was observed over the entire thickness direction of the amorphous silicon film (13), and it was confirmed that the entire film was amorphous.

Next, at 550 ° C. and 5 ° C. in a nitrogen atmosphere at atmospheric pressure.
The amorphous silicon film (13) was crystallized by heating for a time.
By this crystallization step, a crystalline silicon semiconductor film could be obtained. The heating temperature in the above-mentioned crystallization step is generally the crystallization temperature of amorphous silicon (according to experiments, it has been found that 600 ° C. or more is necessary if heating is performed for about 10 hours). Can be performed at the following temperature, and the heating time can be shortened.

Using the crystalline silicon semiconductor film formed on the glass substrate as described above, an N-channel TFT and a P-channel TFT were manufactured. The fabrication method was based on a conventional method. With an N-channel TFT, a mobility of 70 cm ² / Vs or more could be obtained, and even with a P-channel TFT, a mobility of 30 cm ² / Vs or more could be obtained. This is the same result as the case of using a crystalline silicon semiconductor film crystallized by heating at 600 ° C. for 24 hours without performing the amorphization treatment by silicon ions. That is, the effect obtained by heating at 600 ° C for 24 hours is 55%.
It was obtained by heating at 0 ° C. for 5 hours.

[Embodiment 2] This embodiment is an embodiment of the second invention, in which a crystal growth direction of a crystallized semiconductor material formed on a glass substrate is set in a direction parallel to the substrate. By doing so, it is proposed to improve the electrical characteristics in the direction parallel to the substrate.

FIG. 3 shows a manufacturing process of this embodiment. In FIG. 3, components having the same reference numerals as those in FIG.
This is the same as that described in the first embodiment. First, a base silicon oxide film is formed on a glass substrate (Corning 7059) in the same manner as in Example 1, and thereafter, a silicon semiconductor film (13) having crystallinity is formed. In this embodiment, the microcrystalline silicon semiconductor film (13) is deposited by a thermal CVD method at a temperature of 550 ° C.
The film is formed to a thickness of Å. As a method for forming the silicon semiconductor film having crystallinity, a known plasma CVD method can be used.

In the above structure, the microcrystalline silicon semiconductor film (1
The reason for forming 3) is to perform crystal growth later using the crystal component in this film as a crystal nucleus. Of course, even in the case of a normal amorphous silicon semiconductor film, it is considered that a crystal component (a minute region in which order is recognized) exists as a matter of degree. An amorphous semiconductor film may be used.

After the structure shown in FIG. 3A is obtained as described above, a metal mask (15) is provided as shown in FIG. 3B. Next, silicon ions (14) are implanted in the same steps as in the first embodiment, and silicon ions are implanted into portions not covered with the metal mask. As a result, the region into which the silicon ions have been implanted is centered on the vicinity of the interface between the semiconductor film (13) and the substrate (here, the combination of the base silicon oxide film (12) and the substrate (11)). Then, it is made amorphous.

Thereafter, as in the first embodiment, the semiconductor film (13) in the amorphous region (6) is crystallized by heating at 550 ° C. for 5 hours in a nitrogen atmosphere. At this time, crystallization is also performed in a region where silicon ions are not implanted (region other than (6) ). However, since the crystallization speed in this region is low, the crystallization is selectively performed in the region (6). Will be performed. What is important here is that the crystal growth proceeds from the region where the amorphization has not been performed by the implantation of silicon ions (14) as indicated by the arrow (17), and the crystallinity is promoted in the direction parallel to the substrate surface. Is to be done.

The above phenomenon is based on the same principle as the phenomenon in which the crystal component of the substrate surface is used as a crystal nucleus to cause the crystal growth of the amorphous semiconductor film in the direction perpendicular to the substrate surface.

By adopting the configuration of this embodiment, the electrical characteristics of a semiconductor device such as a TFT using carrier conduction in the planar direction of the crystalline silicon semiconductor film (corresponding to the direction (17) in FIG. 3). Can be improved.

[0045]

[Effect] By amorphizing the vicinity of the interface between the substrate surface and the non-single-crystal semiconductor by injecting inert ions, crystallization can be performed by heating at a lower temperature and for a shorter time than before, and A crystalline semiconductor film having electrical characteristics comparable to those of a crystalline semiconductor film obtained by a conventional method was obtained.

[Brief description of the drawings]

FIG. 1 shows an outline of an embodiment.

FIG. 2 shows a state of implantation of silicon ions in the embodiment.

FIG. 3 shows an outline of an embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Glass substrate 12 Underlying silicon oxide film 13 Semiconductor film 14 Silicon ion 15 Metal mask 6 Region into which silicon ion was implanted 17 Direction of crystal growth

Claims (5)

(57) [Claims] A step of forming a non-single-crystal semiconductor film over a substrate , wherein ions of an inactive element from the non-single-crystal semiconductor film toward the substrate have a maximum value of the distribution of the ions. Territory
A method for manufacturing a semiconductor device, comprising: a step of implanting a region so as to exist in a substrate; and a step of crystallizing the non-single-crystal semiconductor film into which the ions have been implanted by heating. To 2. A substrate forming a non-single crystal semiconductor film, toward said substrate from the said non-single crystal semiconductor film, an ion selective inert element, the maximum of the distribution of the ion value
A step of implanting such that a region to be present is present in the substrate, and heating the region of the non-single-crystal semiconductor film into which the ions of the inert element have been implanted, in which the ions of the inert element have not been implanted. Forming a crystal from a region. 3. An apparatus according to claim 1 or claim 2, the dose of ion-inert ^{elements, 3 × 10 14 cm - 2} ~3 ×
A method for manufacturing a semiconductor device, comprising ^: 10 ¹⁵ cm -2. Te wherein any one smell of claims 1 to 3 <br/>, inert element, the semiconductor device manufacturing method which is characterized in that an element of the material constituting the non-single crystal semiconductor film . Te wherein any one smell of claims 1 to 4 <br/>, substrate, a semiconductor device manufacturing which is a glass substrate a glass substrate or top silicon oxide film, is formed Method.