JPH07169689A - Crystallization method for semiconductor film - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a method for crystallizing a semiconductor film which can be crystallized or recrystallized in a temperature condition below the melting point without taking a long time. [Structure] An amorphous Si (silicon) film (semiconductor film) 30 formed on a base material 3 by a plasma CVD method is carried into a crystallization apparatus via a conveyor belt 4 and is guided to a guide plate 5. A method of crystallizing the amorphous Si film 30 by applying heat to the amorphous Si film 30 from the attached ultrasonic vibrator 6 while applying ultrasonic vibration energy to the amorphous Si film 30 at a temperature not higher than the melting point of Si. According to this method, even if a crystal grain size is small in the crystallization process in the polycrystalline Si film or a portion where the bond between Si atoms is broken or the bond distance is irregular such that the crystallinity is not good, Compared to a good part, the part having poor crystallinity is more likely to be broken by the action of ultrasonic vibration energy, and the broken parts are subjected to heat energy from the surroundings to promote recrystallization. Therefore, the crystallinity can be improved.

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 film applied to a thin film transistor, a solar cell, etc., and particularly to a semiconductor film formed on a substrate by heat treatment to crystallize or recrystallize the film. The present invention relates to improvement of a crystallization method for performing crystallization.

[0002]

2. Description of the Related Art As a semiconductor film of this type, a polycrystalline silicon film formed on a substrate by a film forming means such as a CVD (chemical vapor deposition) method or a sputtering method has been widely used. However, since the polycrystalline silicon film manufactured by such a method has a small crystal grain size and insufficient electric characteristics, recently, an amorphous silicon film is once formed on a heat-resistant base material, Crystallization methods for semiconductor films have been attempted, such as heating and melting to crystallize, or once forming a polycrystalline silicon film on the heat-resistant substrate and then heating and melting to recrystallize the semiconductor film.

[0003]

By the way, although it is possible to obtain a semiconductor film having a large crystal grain size by adopting such a crystallization method, on the other hand, in the conventional crystallization method, a film is once formed. Since it is necessary to heat-treat the formed semiconductor film to a temperature above its melting point, there is a problem that heat resistance is required for the base material and the selection range of the material is narrowed. When melted,
There is a problem that impurities contained in the base material are likely to be thermally diffused in the crystallized or recrystallized semiconductor film.

Incidentally, as a method for solving such a problem,
Also proposed is a method (solid-phase growth method) in which an amorphous semiconductor film is once formed on a substrate and heat-treated at a temperature below the melting point of the semiconductor material forming the semiconductor film to crystallize the semiconductor film. Has been done.

However, this method of crystallizing a semiconductor film under the temperature condition below the melting point has a problem that the productivity is poor because the temperature condition is low and it takes a long time to crystallize. It took about 40 hours to crystallize the amorphous silicon film at a temperature of 550 ° C.
On the other hand, when the temperature condition for crystallization is increased in order to improve the productivity, there is a problem that the crystallinity of the obtained semiconductor film is easily disturbed.

The present invention has been made by paying attention to such a problem, and its object is to crystallize or recrystallize a semiconductor film at a temperature below the melting point and without requiring a long time. Another object of the present invention is to provide a method for crystallizing a semiconductor film capable of achieving the above.

[0007]

That is, in the invention according to claim 1, the amorphous or crystalline semiconductor film formed on the substrate is heat-treated to crystallize or recrystallize it. Assuming a method for crystallizing a semiconductor film, a temperature not higher than the melting point of the semiconductor material forming the semiconductor film while applying ultrasonic vibration energy to the amorphous or crystalline semiconductor film formed on the substrate. It is characterized in that the heat treatment is performed under the conditions.

According to the method for crystallizing a semiconductor film of the present invention, the ultrasonic vibration energy is applied to the amorphous or crystalline semiconductor film formed on the substrate. Heat treatment has been performed, and the crystallinity is not good, such as in the part where the crystal grain size is small in the semiconductor film during crystallization or recrystallization, or in the part where the bonds of semiconductor material atoms are broken or the bond distance is irregular. Even if a part is generated, a part having poor crystallinity is more likely to be broken by the action of the ultrasonic vibration energy than a good part, and the broken part is heat energy and the above from the surroundings. Recrystallization is promoted by the action of ultrasonic vibration energy, so even if the heat treatment temperature is set below the melting point of the semiconductor material, a semiconductor film with a large crystal grain size can be formed in a short time. Rukoto is possible.

That is, according to the invention of claim 1,
Due to the action of the ultrasonic vibrational energy, the unification of the crystal grains in the semiconductor film during the crystallization or recrystallization, the expansion of the crystal grain size as a result and the reduction of lattice defects and the like can be achieved, so that the crystallization or the recrystallization is performed. Even if the required heating condition is set to be equal to or lower than the melting point of the semiconductor material, a semiconductor film having a large crystal grain size and good crystallinity can be obtained in a short time.

Therefore, as compared with the conventional crystallization method in which the heating temperature is set to be higher than the melting point of the semiconductor material, the applicable range of the base material is expanded, and the impurities contained in the base material are thermally diffused into the semiconductor film. It is also possible to prevent deterioration of semiconductor characteristics due to impurity diffusion, and to reduce the time required for crystallization as compared with the conventional solid-phase growth method in which the heating temperature is set below the melting point of the semiconductor material. Can be shortened,
Moreover, the crystallinity can be greatly improved.

In the case of crystallizing an amorphous semiconductor film formed on a substrate, the ultrasonic wave has the poorer crystallinity than the case of recrystallizing a crystalline semiconductor film. Since the defective crystal region is more easily broken by the vibration energy than the latter, it is possible to relax the heating conditions required for the crystallization treatment.

Here, as the base material applicable to the present invention, the heat resistant base material applied in the conventional method can be used as it is, and the base material whose heat resistant temperature is lower than the melting point of the semiconductor material can also be applied. Is possible. Then, in consideration of wettability with the semiconductor material to be formed into a film, for example, when the semiconductor material is silicon, a silicon plate, a graphite plate, a carbon-carbon composite material (for example, carbon fiber and a carbonized resin component are used). Etc.), carbon-based materials such as carbon fiber woven cloth, ceramic base materials such as alumina and zirconia, and heat-resistant glass-based base materials such as quartz base materials. , SUS, inconel, molybdenum, titanium, tungsten and the like can be applied.

Examples of the semiconductor material applicable to the present invention include silicon, germanium, silicon carbide, silicon germanium alloy, silicon germanium carbide and the like.

As a means for forming an amorphous or crystalline semiconductor film on the above-mentioned substrate, there is a method of adjusting the crystallinity of the semiconductor film by crystallizing or recrystallizing the film once formed. Therefore, as in the conventional case, any film forming means can be applied. For example, a CVD (chemical vapor deposition) method such as plasma CVD, thermal CVD, or photo CVD, a vacuum vapor deposition method, a sputtering method, an ion plating method. PVD (Physical Vapor Deposition) method and the like.

[0015]

According to the first aspect of the present invention, the amorphous or crystalline semiconductor film formed on the base material is supplied with ultrasonic vibration energy while being equal to or lower than the melting point of the semiconductor material forming the semiconductor film. The heat treatment is performed under the temperature condition of 1., and the crystal grains in the semiconductor film are coalesced during the crystallization or recrystallization by the action of the ultrasonic vibration energy described above, thereby increasing the crystal grain size and reducing the lattice defects. Therefore, even if the heating condition required for crystallization or recrystallization is set to be equal to or lower than the melting point of the semiconductor material, a semiconductor film having a large crystal grain size and good crystallinity can be obtained in a short time.

[0016]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 shows a conceptual diagram of the structure of a crystallization apparatus applied in this embodiment.
A pair of rotating rollers 1, 2, an endless conveyor belt 4 for conveying the base material 3 wound around the rotating rollers 1, 2 and having the amorphous or crystalline semiconductor coating 30 formed thereon, and the endless conveyor belt 4. A guide plate 5 is provided on the upper rear side of the conveyor belt 4 so as to be slidable with the rear surface of the conveyor belt 4 and has a width dimension wider than the width dimension of the conveyor belt 4, and is attached to an end portion in the width direction of the guide plate 5. The ultrasonic transducer 6 provided therein, an oscillator 7 connected to the ultrasonic transducer 6 to oscillate ultrasonic vibration energy from the ultrasonic transducer 6, and the conveyor belt 4 provided above the endless conveyor belt 4. The main part is constituted by the oven 8 for heating the amorphous or crystalline semiconductor coating 30 on the base material 3 which is conveyed by. [Example 1] A carbon sheet having a thickness of 1 mm as the above-mentioned base material 3 (trade name glassy carbon manufactured by Tokai Carbon Co., Ltd.)
And an amorphous silicon film 30 having a film thickness of 3 μm was formed on the base material 3 by the plasma CVD method. still,
The conditions for forming the amorphous silicon film 30 are as follows. (Film forming conditions) Type of reaction gas; SiH ₄ reaction gas supply rate; 20 SCCM reaction gas pressure; 200 mTorr discharge power; 20 W Heating temperature of base material 3; 250 ° C. Next, the amorphous silicon film 30 is formed. The film-formed base material 3 was carried into the crystallization apparatus through the endless conveyor belt 4, and the amorphous silicon film 30 was heat-treated under the following crystallization conditions to obtain a polycrystalline silicon film. The heating time is set by adjusting the speed of the endless conveyor belt 4. (Crystallization conditions) Heating temperature: 600 ° C. Heating time: 4 hours Power input to the ultrasonic oscillator: 1.0 kW About the polycrystalline silicon film thus obtained TE
As a result of M observation, it was confirmed that the crystal grain size reached about 5 μm and the film characteristics were also uniform.

Regarding the film forming conditions, a polycrystalline silicon film having substantially the same characteristics can be obtained even if the film forming conditions are changed within the following range.

Reaction gas supply rate (5 SCCM-100
SCCM) Pressure of reaction gas; (50 mTorr to 1 Torr) Discharge power; (5 W to 100 W) Heating temperature of base material 3; (100 ° C. to 300 ° C.) [Comparative Example 1] Ultrasonic vibration energy is applied in the above crystallization apparatus. The amorphous silicon film was crystallized under substantially the same conditions as in Example 1 except that it was not heated and the heating condition was 1430 ° C.

TEM observation of this polycrystalline silicon film revealed that the crystal grain size was about 3 μm. [Comparative Example 2] Crystallization treatment of an amorphous silicon film under substantially the same conditions as in Example 1 except that ultrasonic vibration energy was not applied in the above crystallization apparatus and that the heating time was 40 hours. I went.

TEM observation of this polycrystalline silicon film revealed that the crystal grain size was about 4 μm, and many twins were found in the crystal grains. [Example 2] Carbon fiber cloth (trade name CFS 1140) manufactured by Arisawa Manufacturing Co., Ltd., the characteristics of which are shown in Table 1 below, was applied as the base material 3, and the following product was formed on the base material 3. Film thickness of 5 by thermal CVD method depending on film conditions
A polycrystalline silicon film 30 having a thickness of 0 μm was formed, and the polycrystalline silicon film 30 was heat-treated and recrystallized under the following recrystallization conditions.

[0022]

[Table 1] (Film forming conditions) Kind of reaction gas; SiH ₄ + H ₂ (SiH ₄ : 1%) Supply rate of reaction gas; 1 SLM Reaction gas pressure; 10 Torr Base material 3 heating temperature; 900 ° C. (recrystallization condition) Heating temperature; 1300 ° C. Heating time; 30 minutes Power input to ultrasonic transducer; 1.0 kW Polycrystalline silicon film thus obtained TE
As a result of M observation, it was confirmed that the crystal grain size reached about 100 μm and the film characteristics were also uniform.

Regarding the above film forming conditions and recrystallization conditions, polycrystalline silicon films having substantially the same characteristics are obtained even if the conditions are changed within the ranges shown below. (Film Forming Conditions) Reaction Gas Supply Rate (0.1 SLM to 5 SLM) Reaction Gas Pressure; (1 Torr to 100 Torr) Heating Temperature of Base Material 3; (850 ° C. to 1000 ° C.) (Recrystallization Conditions) Heating Temperature; (1250 ° C. to 1400 ° C.) Heating time; (10 minutes to 120 minutes) Input power to ultrasonic transducer; (0.3 kW to 2.0 k
W) [Example 3] An amorphous silicon film 30 having a film thickness of 2 µm was formed on the base material 3 made of the above carbon sheet by the photo CVD method under the following film forming conditions, and the same as in Example 1. The amorphous silicon film 30 was crystallized under the crystallization conditions. (Film forming conditions) Kind of reaction gas: Si ₂ H ₆ + H ₂ (Si ₂ H ₆ : 1
%) Reaction gas supply rate; 100 SCCM Reaction gas pressure; 10 Torr UV light irradiation light source; Hg lamp Base material 3 heating temperature; 250 ° C. Polycrystalline silicon film thus obtained TE
As a result of M observation, it was confirmed that the crystal grain size reached about 5 μm and the film characteristics were uniform, as in Example 1. [Embodiment 4] Amorphous silicon film 3 having a film thickness of 3 μm is formed on substrate 3 made of the above carbon sheet by sputtering.
The amorphous silicon film 30 was crystallized under the same crystallization conditions as in Example 1.

TEM observation of the thus-obtained polycrystalline silicon film revealed that the crystal grain size reached about 4.5 μm and the film characteristics were uniform as in Example 1. Was confirmed. [Embodiment 5] A polycrystalline silicon film 30 having a film thickness of 50 μm is formed on the base material 3 made of the carbon sheet by the ion plating method under the following film forming conditions, and the same recrystallization as in Embodiment 2 is performed. According to the conversion conditions, the polycrystalline silicon film 30
Was heated to recrystallize it. (Film forming conditions) Pressure in the film forming chamber; 5 mTorr target; Si target Power input to RF coil; 100 W Heating temperature of base material 3; 700 ° C. Polycrystalline silicon film thus obtained TE
As a result of M observation, it was confirmed that the crystal grain size reached about 100 μm and the film characteristics were uniform, as in Example 2.

Regarding the above film forming conditions, a polycrystalline silicon film having substantially the same characteristics is obtained even if the conditions are changed within the following range. (Film forming conditions) Pressure in film forming chamber; (1 to 10 mTorr) Input power to RF coil; (50 to 200 W) [Example 6] Glass is applied as the base material 3, and
An amorphous germanium film 30 having a film thickness of 3 μm was formed on the base material 3 by the plasma CVD method. The conditions for forming the amorphous germanium film 30 are as follows. (Film forming conditions) Kind of reaction gas; GeH ₄ reaction gas supply rate; 20 SCCM reaction gas pressure; 200 mTorr discharge power; 20 W heating temperature of base material 3; 250 ° C. Next, the amorphous germanium film 30 The film-formed base material 3 is carried into the crystallization apparatus through the endless conveyor belt 4, and the amorphous germanium film 30 is heat-treated according to the following crystallization conditions to obtain a polycrystalline germanium film. It was (Crystallization conditions) Heating temperature: 500 ° C. Heating time: 4 hours Power applied to the ultrasonic oscillator: 1.0 kW TEM observation was performed on the polycrystalline germanium film thus obtained, and its crystal grains were found. It was confirmed that the diameter reached about 5 μm and the film characteristics were uniform. Example 7 A polycrystalline germanium film 30 having a film thickness of 30 μm was formed on the substrate 3 made of the carbon sheet by the thermal CVD method under the following film forming conditions, and the polycrystal was formed according to the following recrystallization conditions. The germanium film 30 was heat-treated to recrystallize it. (Film forming conditions) Kind of reaction gas; GeH ₄ + H ₂ (GeH ₄ : 1%) Reaction gas supply rate; 1 SLM Reaction gas pressure; 10 Torr Substrate 3 heating temperature; 700 ° C. (recrystallization condition) Heating temperature: 900 ° C. Heating time: 30 minutes Input power to ultrasonic transducer: 1.0 kW When the polycrystalline germanium film thus obtained was observed by TEM, its crystal grain size reached about 50 μm. It was also confirmed that the film characteristics were uniform.

Regarding the above film forming conditions and recrystallization conditions, a polycrystalline germanium film having substantially the same characteristics can be obtained even if the conditions are changed within the ranges shown below. (Film Forming Conditions) Reaction Gas Supply Rate (0.1 SLM to 5 SLM) Reaction Gas Pressure; (1 Torr to 100 Torr) Heating Temperature of Base Material 3; (550 ° C. to 800 ° C.) (Recrystallization Conditions) Heating Temperature; (850 ° C. to 950 ° C.) Heating time; (10 minutes to 120 minutes) Input power to ultrasonic transducer; (0.3 kW to 2.0 k
W) [Embodiment 8] A film thickness of 10 μm was formed on the base material 3 made of the carbon sheet by the plasma CVD method under the following film forming conditions.
m of polycrystalline silicon germanium alloy film 30 is formed,
In addition, the polycrystalline silicon germanium alloy film 30 was heat-treated and recrystallized under the following recrystallization conditions. (Film forming conditions) Type of reaction gas: SiH ₄ + GeH ₄ + H ₂ (5%: 5
%: 90%) Reaction gas supply rate; 100 SCCM Reaction gas pressure; 200 mTorr Discharge power; 50 W Heating temperature of base material 3; 600 ° C. (recrystallization condition) Heating temperature; 1100 ° C. Heating time; 30 minutes Ultrasonic vibration When the TEM observation was conducted on the polycrystalline silicon germanium alloy film thus obtained, the crystal grain size reached about 15 μm and the film characteristics were uniform. It has been confirmed that

Regarding the above film forming conditions and recrystallization conditions, a polycrystalline silicon germanium alloy film having substantially the same characteristics can be obtained even if the conditions are changed within the following range. (Film forming conditions) Reaction gas supply rate (20 SCCM to 200 SCCM) Reaction gas pressure; (50 mTorr to 300 mTorr
r) Discharge power; (20W to 100W) Heating temperature of the base material 3; (450 ° C to 800 ° C) (recrystallization condition) Heating temperature; (1000 ° C to 1150 ° C) Heating time; (10 minutes to 120 minutes) Input power to ultrasonic transducer; (0.3kW-2.0k
W)

[0028]

According to the first aspect of the present invention, the crystal grains in the semiconductor film are coalesced during the crystallization or recrystallization by the action of the ultrasonic vibration energy, and thereby the crystal grain size is enlarged and the lattice defect is generated. Therefore, even if the heating condition required for crystallization or recrystallization is set to be equal to or lower than the melting point of the semiconductor material, a semiconductor film having a large crystal grain size and good crystallinity can be obtained in a short time.

Therefore, compared with the conventional crystallization method in which the heating temperature is set to be equal to or higher than the melting point of the semiconductor material, the applicable range of the base material can be expanded, and the impurities contained in the base material can be thermally diffused into the semiconductor film. It is also possible to prevent deterioration of semiconductor characteristics because it is suppressed, and the time required for crystallization or recrystallization can be shortened as compared with the conventional crystallization method in which the heating temperature is set to the melting point of the semiconductor material or lower. In addition, the crystallinity can be significantly improved.

[Brief description of drawings]

FIG. 1 is a structural conceptual diagram of a crystallization device applied in an example.

[Explanation of symbols]

 3 Base Material 4 Conveyor Belt 5 Guide Plate 6 Ultrasonic Transducer 7 Oscillator 8 Oven 30 Semiconductor Coating

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/324 Z 29/786 21/336 31/04

Claims (1)

[Claims] 1. A method for crystallizing a semiconductor film, which comprises subjecting an amorphous or crystalline semiconductor film formed on a substrate to heat treatment to crystallize or recrystallize the same. Crystallization of a semiconductor film, characterized in that the amorphous or crystalline semiconductor film formed is subjected to heat treatment under a temperature condition below the melting point of the semiconductor material forming the semiconductor film while applying ultrasonic vibration energy. Method.