JPH1167662A - Manufacture of semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a polycrystal silicon thin film with a high carrier mobility even when using as its substrate a quartz one with a low purity, by projecting an energy beam on an amorphous silicon thin film to crystallise it, and by applying thereafter to the intermediate thereof a short-time heat treatment at a medium temperature. SOLUTION: By a CVD method, an amorphous silicon thin film is formed on a quartz substrate. Then, while when an energy beam is projected on this amorphous silicon thin film to crystallise it, it can be changed into a polycrystal silicon thin film of a good quality at a low temperature, the polycrystal silicon thin film contain a large amount of crystal defects in its crystal grain. In order to eliminate these crystal defects, a short-time heat treatment is applied to it at a medium temperature. Hereupon, the medium temperature means, e.g. a temperature within the scope of 850-950 deg.C, and the short time means, e. g. a time within the scope not shorter than five minutes and not longer than fifteen minutes. When performing its short-time heat treatment at the medium temperature in this way, reducing the pollutions of impurities mixed into it from the substrate, thus, a cheap quartz substrate can be used.

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 suitable for forming a polycrystalline silicon thin film having a higher carrier mobility than an ordinary polycrystalline silicon on an insulating layer.

[0002] In general, a polycrystalline silicon thin film formed on an insulating layer is used for a semiconductor device, an LCD (liquid).
Although it is used in many fields such as crystal display and solar cells, it is necessary to improve the carrier mobility if formed by ordinary means, and it is necessary to improve the carrier mobility. Is disclosed.

[0003]

2. Description of the Related Art In general, a high-performance polycrystalline silicon thin film having high carrier mobility uses quartz as a substrate material and forms an amorphous silicon thin film grown on the substrate at a temperature of, for example, about 600 ° C. 20 [hours]-30 [hours]
It is made by performing a degree of heat treatment and polycrystallizing.

[0004] Using the polycrystalline silicon thin film thus obtained, for example, a TFT (thinfilm tran)
In order to create a cistor, a high-temperature process of 1000 ° C. or more is required.

[0005] The reason of going through the process of exposing to such a high temperature is as follows.
This is due to the fact that the carrier mobility in the crystal is increased, and that the process is stable in terms of reproducibility, manufacturing yield, and the like.

At present, the need for a TFT is, of course,
In the field of CDs, in this case, in order to perform the heat treatment of the polycrystalline silicon thin film at the high temperature as described above, a high-purity quartz substrate is necessary in order to suppress the inflow of impurities from the transparent substrate. Such a quartz substrate is difficult to enlarge and very expensive.

[0007]

SUMMARY OF THE INVENTION In the present invention, a thin film of polycrystalline silicon having a high carrier mobility can be formed while using an inexpensive quartz substrate containing many impurities and low purity. And other semiconductor devices.

[0008]

According to the present invention, an amorphous silicon thin film is irradiated with an energy beam to be crystallized, and then has a lower temperature than a heat treatment temperature received during a semiconductor device manufacturing process. That is, it is fundamental to eliminate the intragranular defects by performing a heat treatment at a medium temperature for a short time.

In general, when an amorphous silicon thin film is crystallized by irradiating it with an energy beam, high-quality polycrystal can be obtained at a low temperature. However, crystal defects contain a large amount of crystal defects. .

In order to eliminate the crystal defects, a short-time heat treatment is applied at an intermediate temperature. Here, the medium temperature is, for example,
The temperature is 850 ° C. to 950 ° C., and the short time is, for example, a range from 5 minutes to 15 minutes.

As described above, when the heat treatment is performed at a medium temperature for a short time, impurity contamination from the substrate is small.
Inexpensive quartz can be used, and the cost can be reduced.

The reason why the intermediate temperature heat treatment is performed before the semiconductor device manufacturing process is to avoid depositing another film on the surface of the polycrystalline silicon thin film.

When another film is deposited on the polycrystalline silicon thin film, the components of the film penetrate into the polycrystalline silicon thin film, and the components are gettered as impurities by crystal defects in the polycrystalline silicon thin film. Defects are less likely to disappear. Further, when another film is deposited on the polycrystalline silicon thin film, recrystallization of the crystal grains of the polycrystalline silicon is hindered by the deposited film, and it is difficult to change to large crystal grains. For these reasons, it is necessary to perform the intermediate temperature heat treatment before the semiconductor device manufacturing process.

As described above, in the method of manufacturing a semiconductor according to the present invention, there are provided (1) a step of forming a silicon thin film on a transparent insulating substrate and then irradiating it with an energy beam to form a polycrystalline silicon thin film; The temperature is set to 850 before a semiconductor device is manufactured using the polycrystalline silicon thin film.
[° C] to 950 [° C], and the time is 5
Or a step of performing a heat treatment as a range of not less than [minutes] and not more than 15 [minutes], or

(2) In the above (1), the energy beam is a laser beam, or

(3) In the above (1) or (2),
The thickness of the silicon thin film is 30 [nm] to 100 [nm]
It is characterized by being.

By adopting the above-mentioned means, it becomes possible to form a polycrystalline silicon thin film having a high carrier mobility on an inexpensive quartz substrate containing a large amount of impurities. LCD devices using high-performance TFTs can be manufactured at low cost, and the heat treatment temperature for obtaining polycrystalline silicon thin films with high carrier mobility is low, so use large quartz substrates. Therefore, the present invention can be applied to a direct-view LCD device.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For example, CVD (chemical
By applying a vapor deposition method, an amorphous silicon thin film having a thickness of, for example, 50 nm is formed on a quartz substrate.
The silicon thin film was irradiated with a laser beam to form a polycrystalline silicon thin film, and this polycrystalline silicon thin film was subjected to a heat treatment at a medium temperature. The thickness of the amorphous silicon thin film can be selected in the range of 30 [nm] to 100 [nm]. When the thickness is out of this range, that is, less than 30 [nm], the contact of the source and the drain is reduced. The resistance becomes large, the state is out of the standard range currently used in practical use of this kind of semiconductor device, and
If it exceeds [nm], the leak current becomes large and the state is out of the standard range as described above, and the product is treated as a defective product.

FIG. 1 is a diagram showing Raman scattering observation results for a polycrystalline silicon thin film subjected to a heat treatment while changing the temperature. The horizontal axis represents the heat treatment temperature, the left vertical axis represents the half width at half maximum, The right vertical axis shows the peak position.
The heat treatment time was set at 5 minutes at each temperature.

As shown in the figure, the heat treatment temperature is 850 ° C.
Above this, crystallization becomes good and the peak position is 520
Since the temperature is approaching [cm ^-1 ], the polycrystalline silicon thin film crystallized by laser irradiation can be changed to a high quality crystal by heat treatment at a temperature exceeding 850 [° C.].

It can be seen that the above tendency is maintained up to around 950 ° C., and that the half-width is reduced when the heat treatment is performed at 950 ° C.

It is apparent that the quality of the crystal is further improved when the heat treatment is performed at a temperature of 1000 ° C. or more, but this temperature region is a region where a polycrystalline silicon thin film is formed by the high-temperature heat treatment. As a result, a high-purity quartz substrate is required, and the cost increases.

FIG. 2 is a diagram showing Raman scattering observation results for a polycrystalline silicon thin film subjected to heat treatment with changing time, wherein the horizontal axis represents the heat treatment time, the left vertical axis represents the half-width at half maximum, The right vertical axis shows the peak position.
The heat treatment temperature is fixed at 950 ° C. for each time.

From the figure, it can be clearly seen that the half-width at half-maximum is reduced and the peak position approaches the peak position of the single crystal by performing the heat treatment for 15 [minutes].

As described above, when the polycrystalline silicon thin film crystallized by laser is used as the initial film, the quality can be easily improved by the short-time heat treatment in the medium temperature region.

FIG. 3 is a diagram showing electrical characteristics obtained by subjecting a laser-crystallized polycrystalline silicon thin film to a short-time heat treatment in an intermediate temperature region. The horizontal axis represents the heat treatment temperature, and the vertical axis represents the carrier. Each mobility is taken.

This data shows that a polycrystalline silicon thin film subjected to a heat treatment at a changed temperature has a hole (HALL).
It is the result of measuring the carrier mobility using the effect,
The heat treatment time was 15 minutes at each temperature.

As is apparent from FIG.
[° C.], heat treatment for 15 minutes, 80 [cm ² / V]
S].

In the present invention, the present invention is not limited to the above embodiment, and many other modifications can be realized. For example, a general sapphire substrate used in the semiconductor field has the above-described structure. Since a problem similar to that of the quartz substrate exists, a similar effect can be obtained even when the present invention is applied to a sapphire substrate.

[0030]

According to the method of manufacturing a semiconductor of the present invention,
A silicon thin film is formed on a transparent insulating substrate and then irradiated with an energy beam to form a polycrystalline silicon thin film. At a stage before a semiconductor device is formed using the polycrystalline silicon thin film, the temperature is 850 ° C. to 950 ° ° C] and the time is in the range of 5 minutes to 15 minutes.

By adopting the above configuration, it becomes possible to form a polycrystalline silicon thin film having a high carrier mobility on an inexpensive quartz substrate containing a large amount of impurities by using the quartz substrate. LCD devices using high-performance TFTs can be manufactured at low cost, and the heat treatment temperature for obtaining polycrystalline silicon thin films with high carrier mobility is low, so use large quartz substrates. Therefore, the present invention can be applied to a direct-view LCD device.

[Brief description of the drawings]

FIG. 1 is a diagram showing Raman scattering observation results of a polycrystalline silicon thin film subjected to a heat treatment while changing a temperature.

FIG. 2 is a diagram showing Raman scattering observation results of a polycrystalline silicon thin film subjected to a heat treatment with changing time.

FIG. 3 is a diagram showing electrical characteristics obtained by subjecting a laser-crystallized polycrystalline silicon thin film to a short-time heat treatment in an intermediate temperature region.

Claims (3)

[Claims] A step of forming a silicon thin film on a transparent insulating substrate and then irradiating an energy beam to form a polycrystalline silicon thin film; and a step of forming a semiconductor device using the polycrystalline silicon thin film in a temperature step. A temperature in the range of 850 ° C. to 950 ° C. and a time in the range of 5 minutes to 15 minutes, and performing a heat treatment. 2. The method according to claim 1, wherein the energy beam is a laser beam. 3. The silicon thin film has a thickness of 30 nm to 1 nm.
3. The method according to claim 1, wherein the value is 00 [nm].
The manufacturing method of the semiconductor of the description.