JP2000091242A - Manufacture of amorphous silicon thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a thin film with a high throughput by generating a plasma of a process gas and dehydrogenating an amorphous silicon thin film by exposing the surface of the amorphous silicon thin film to the plasma. SOLUTION: When an a-Si thin film is formed to a prescribed thickness, impression of a high-frequency voltage upon a high-frequency electrode 22 and supply of a gaseous starting material to the electrode 22 are stopped without lowering the temperature of a glass substrate 2. When an argon gas is supplied to the electrode 22 from a gas introducing system 27 after the gaseous starting material left in a vacuum tank 20 is evacuated thereafter, the argon gas is discharged into the tank 20. When the impression of the high-frequency voltage upon the electrode 22 is restarted while the argon gas is discharged into the tank 20, an argon gas plasma is generated. When the a-Si thin film on the surface of the glass substrate 2 is exposed to the argon gas plasma, the hydrogen taken in the a-Si thin film is discharged and the thin film is dehydrogenated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the technical field of forming an amorphous silicon thin film.

[0002]

2. Description of the Related Art In the technical field of liquid crystal display panels, in order to improve display speed and display quality, an active matrix drive system using thin film transistors has recently become the mainstream in place of a simple matrix drive system.

A thin film transistor can be formed as an a-Si (amorphous silicon) thin film, a poly-Si (polysilicon) thin film, or a single-crystal Si thin film. However, from the viewpoint of cost and productivity, a thin film transistor is first formed on a substrate. -Si thin film is formed,
After the dehydrogenation treatment is performed in a later step, a technique of changing the a-Si thin film into a poly-Si thin film by laser annealing is employed.

[0004] Reference numeral 101 in FIG.
The apparatus is a thin film forming apparatus and has a transfer chamber 10 around which a charging / discharging chamber 111 and a preheating chamber 112 are provided, and _four reaction chambers 115 _{1 to} 1154 are arranged.

[0005] In this a-Si thin film forming apparatus 101,
When forming the Si thin film, the inside of the transfer chamber 110, the inside of the preheating chamber 112, and the inside of the reaction chambers 115 _{1 to} 115 ₂ are evacuated in advance, and a predetermined number of substrates are mounted in the loading / unloading chamber 111. After that, the substrate is evacuated and evacuated, and one substrate is taken out by the substrate transfer robot 119 arranged in the transfer chamber 110 and is carried into the preheating chamber 112.

The substrate is heated to a predetermined temperature in the preheating chamber 112.
After the temperature is raised, the desired reaction chamber 115 ₁~ 115_FourCarry in
Forming an a-Si thin film by a plasma CVD method,
It is returned to the charging / unloading chamber 111. Installed in the loading / unloading room 111
A-Si thin film is formed on all of the substrates
After returning to the inside of 111, the substrate is large
I take it out in my mind.

[0007] Then, the a-Si thin film is laser-annealed to form a poly-Si thin film. If the a-Si thin film contains a large amount of hydrogen, the a-Si thin film becomes poly-Si thin. Then, hydrogen is blown out, and the surface of the formed poly-Si thin film becomes crater-like.

In order to prevent the above inconveniences,
Generally, the hydrogen concentration in the a-Si thin film is set to 1.0 atomic%.
Degree (Si: 5 × 10 ²² pieces / cm ³ , H: 5 × 10
It is said that it is necessary to reduce it to about ²⁰ / cm ³ ).

Accordingly, the a-Si thin film forming apparatus 101
After forming the a-Si thin film by the above method, the substrate is taken out to the atmosphere, then carried into a heat treatment device (not shown), the substrate is heated to a predetermined temperature, dehydrogenated, and then laser annealing is performed. .

However, when the a-Si thin film is dehydrogenated, the residual hydrogen concentration can be lowered as the a-Si thin film is heated to a higher temperature.
Even if the -Si thin film is partially converted to poly-Si and then laser annealing is performed, a high-quality poly-Si thin film cannot be obtained. Therefore, the temperature of the dehydrogenation process must be lowered, but there is a problem that the dehydrogenation process requires a long time.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art, and has as its object to provide a method of forming an a-Si thin film having a high throughput.

[0012]

Generally, an a-Si thin film is prepared by placing a substrate in a vacuum atmosphere, introducing a source gas such as SiH ₄ gas, Ar gas, H ₂ gas or a diluent gas to generate plasma. It is manufactured by growing a silicon layer on the substrate surface.

An a-Si thin film formed by using such a plasma CVD method contains a large amount of hydrogen. For example, an a-Si thin film formed at 300 ° C. contains 10 to 20 atomic%. In that case, the hydrogen in the a-Si thin film can be reduced by heating the substrate on which the a-Si thin film is formed. When the temperature is raised again to release hydrogen, it is necessary to heat for a long time.

The inventors of the present invention have found that if the surface on which the a-Si thin film is formed is not exposed to the atmosphere and the surface thereof is immediately exposed to an inert gas plasma, the dehydrogenation treatment can be performed in a short time. .

The present invention has been made based on the above findings, and an invention according to claim 1 is a method for producing an amorphous silicon thin film on an amorphous silicon thin film on a substrate surface. To form an amorphous silicon thin film on the surface of the substrate by generating the source gas plasma, and then, in a vacuum atmosphere in which the substrate is placed, an inert gas, or a hydrogen gas, or a hydrogen gas to an inert gas. Is introduced as a processing gas, a plasma of the processing gas is generated, the surface of the amorphous silicon thin film is exposed to the plasma, and dehydrogenation of the amorphous silicon thin film is performed.

According to a second aspect of the present invention, there is provided the method of manufacturing an amorphous silicon thin film according to the first aspect, wherein after forming the amorphous silicon thin film on the surface of the substrate, the dehydrogenation is performed without exposing the substrate to the atmosphere. Processing is performed.

According to a third aspect of the present invention, there is provided the method of manufacturing an amorphous silicon thin film according to any one of the first and second aspects, wherein the formation of the amorphous silicon thin film and the dehydrogenation treatment are performed in the same manner. It is performed in a reaction tank.

The present invention is configured as described above. A source gas is introduced into a vacuum atmosphere in which a substrate is placed, and a source gas plasma is generated to form an a-Si thin film on the substrate surface. An inert gas, a hydrogen gas, or a gas obtained by adding a hydrogen gas to an inert gas is introduced as a processing gas into the atmosphere where the a-Si thin film is placed, and the a-Si thin film surface is exposed to the plasma of the processing gas. , A-Si thin film is dehydrogenated.

In this case, since the a-Si thin film receives energy from the plasma of the processing gas, a sufficient dehydrogenation process can be performed in a short time without heating to a high temperature.

If the substrate after the formation of the a-Si thin film is subjected to the dehydrogenation treatment without exposing the substrate to the atmosphere, the dehydrogenation treatment can be performed with the substrate heated immediately after the formation of the a-Si thin film. Therefore, the time required for heating can be shortened, and the time for dehydrogenation treatment is further reduced.

Generally, when an a-Si thin film is formed by a plasma CVD method, a plasma generator is provided in the reaction chamber. Therefore, after forming the a-Si thin film, the raw material gas is evacuated to vacuum, When an active gas, a hydrogen gas, or a gas obtained by adding a hydrogen gas to an inert gas is introduced to generate plasma, the surface of the a-Si thin film can be easily exposed to the plasma.

[0022]

Embodiments of the present invention will be described with reference to the drawings. 1, reference numeral 1 indicates an a-Si thin film forming apparatus to which the present invention can be applied.

This a-Si thin film forming apparatus 1
Has a 0, to its periphery, around the transfer chamber 10, and one charge ejecting chamber 11 and the preheating chamber 12, four and reaction chamber 15 _{1-15 4} is arranged . Each reaction chamber 15 _{1-15 4} loading ejecting chamber 11 and the transfer chamber 10 is configured so as to be evacuated independently.

When an a-Si thin film is formed using the a-Si thin film forming apparatus 1 having the above-described configuration, each of the chambers 10 to 10 must be prepared in advance.
12, 15 ₁ to 15 ₄ are evacuated. Next, the atmosphere is introduced only into the loading / unloading chamber 11, a predetermined number of large-diameter glass substrates having a plate thickness of about 0.5 to 3 mm are arranged, and the door to the atmosphere is closed.

After the interior of the charging / discharging chamber 11 is evacuated to a predetermined pressure, a partition between the charging chamber 11 and the transfer chamber 10 is opened. Transfer room 10
A substrate transfer robot 19 is disposed in the inside, and one glass substrate in the loading / unloading chamber 11 is taken out, and the pre-heating chamber 1 is taken out.
Carry in 2 The glass substrate was heated in the preliminary heating chamber 12, the temperature was raised to forming temperature of the a-Si film is carried into a desired reaction chamber (here, the reaction chamber indicated at 15 _1).

[0026] The reaction chamber 15 ₁ and the other of the reaction chamber 15 _2-15
4 are the same, and their schematic configuration is indicated by reference numeral 15 in FIG. Referring to FIG. 2, the reaction chamber 15 has a vacuum chamber 20, a hot plate 21 is disposed on an inner bottom wall side, and a high-frequency electrode 22 is disposed on a ceiling side. Lift pins 24 are inserted through the hot plate 21, and the lift pins 24 and the substrate transport robot 19 are operated to place the glass substrate carried into the reaction chamber 15 on the hot plate 21.

Reference numeral 2 in FIG. 2 indicates a glass substrate in that state, and a loading / unloading port 2 between the transfer chamber 10 and the reaction chamber 15.
After closing 5, the glass substrate 2 is heated to a predetermined temperature by a heater provided in the hot plate 21.

A gas introduction system 27 is connected to the high-frequency electrode 22, and a raw material gas (SiH ₄ ,
When Ar, H ₂ ) is supplied, the inside of the high-frequency electrode 22 is filled. A shower nozzle 23 is provided on a surface of the high-frequency electrode 22 facing the glass substrate 2, and gas filled in the high-frequency electrode 22 is discharged into the vacuum chamber 20 in a shower shape.

The high-frequency electrode 22 is connected to a high-frequency power supply 26 while being insulated from the vacuum chamber 20.
When 0 is grounded and a high-frequency voltage is applied to the high-frequency electrode 22, plasma of the source gas is generated, and an a-Si thin film grows on the surface of the glass substrate 2 (plasma CVD method).

When the a-Si thin film is formed to a predetermined thickness,
The application of the high-frequency voltage to the high-frequency electrode 22 and the supply of the source gas are stopped without lowering the temperature of the glass substrate 2. Then, after evacuating the source gas remaining in the vacuum chamber 20 and then supplying argon gas from the gas introduction system 27 to the high-frequency electrode 22, the argon gas is released into the vacuum chamber 20.

In this state, when the application of the high-frequency voltage to the high-frequency electrode 22 is restarted, argon gas plasma is generated.

When the a-Si thin film on the surface of the glass substrate 2 is exposed to argon gas plasma, hydrogen taken into the a-Si thin film is released, and the a-Si thin film is dehydrogenated. It has also been confirmed that dehydrogenation is performed even when hydrogen gas or a mixture of hydrogen gas and inert gas is introduced into plasma.

FIG. 3 is a graph showing the relationship between the discharge time (plasma generation time) and the residual hydrogen concentration when argon gas is introduced into the reaction chamber 15 and plasma is generated in an atmosphere at a pressure of 200 Pa. The case where the input power to the high-frequency electrode 22 is 500 W, 1 kW, and 2 kW is shown. a-S
Since the residual hydrogen concentration in the i-thin film is preferably as low as possible, it is understood that a power input of 2 kW is appropriate for completing the dehydrogenation treatment in a short time.

[0034] After completion of the dehydrogenation process, the glass substrate 2, and unloaded from the reaction chamber 15 ₁ subjected to the processing, transport room 11
Put back inside. If this occurs, and pre-heating of a glass substrate in the pre-heating chamber 12 is completed, and carries the glass substrate into the reaction chamber 15 _1, and formation and dehydrogenation treatment of the a-Si thin film.

[0035] Other reaction chamber 15 _{2-15 4,} likewise carries the glass substrate preheating is completed in the preheating chamber 12, after the formation and dehydrogenation treatment of the a-Si thin film, Return to the loading / unloading room 11.

When all the processing of the glass substrate mounted in the loading / unloading chamber 11 is completed and the glass substrate returns to the loading / unloading chamber 11, the partition between the loading / unloading chamber 11 and the transfer chamber 10 is closed, and the loading / unloading chamber 11 is opened to the atmosphere. And take out the glass substrate, a-Si
The thin film forming operation ends.

[0037] As a comparative example, except replacing one of the reaction chamber 15 _{1-15 4} into the processing chamber of the dehydrogenation treatment only, it was subjected to dehydrogenation treatment of the a-Si thin film at the process chamber. After forming the a-Si thin film, it is carried into the processing chamber without being exposed to the air,
Heated by a hot plate in the nitrogen atmosphere of a.
FIG. 4 is a graph showing the relationship between the dehydrogenation time of the a-Si thin film and the residual hydrogen concentration in that case. Since hydrogen is released from the a-Si thin film only by heating, the processing time is much longer than in the present invention.

As described above, according to the present invention, a
Since the dehydrogenation treatment can be performed without exposing the glass substrate on which the -Si thin film is formed to the atmosphere, the dehydrogenation treatment time does not increase due to a decrease in the substrate temperature.

According to the present invention, the surface of the a-Si thin film is exposed to argon gas plasma, and the a-Si thin film receives energy from the plasma. You can do it.

The above is the description of the reaction chamber 1 in which the a-Si thin film is formed.
5 ₁ were subjected to dehydrogenation treatment at 15 within _4, the four reaction chamber 1
5 _1-15 of _4, or using the first chamber as the reaction chamber of the dehydrogenation process only, the dehydrogenation process chamber dedicated provided, and carries the substrate to a-Si thin film is formed in the other reaction chamber argon Dehydrogenation treatment may be performed by generating gas plasma.

In the above example, the argon gas plasma was generated during the dehydrogenation treatment. However, in addition to rare gases such as helium gas, neon gas, and xenon gas, for example, H ₂ gas,
An inert gas which does not affect the a-Si thin film, such as a mixed gas thereof, can be widely used (however, nitrogen gas is inappropriate).

[0042]

According to the present invention, the processing time of a glass substrate can be greatly reduced. Since dehydrogenation can be performed in the reaction chamber where the a-Si thin film is formed, no special device is required and the cost is low.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of an a-Si thin film manufacturing apparatus to which the present invention can be applied.

FIG. 2 is a schematic configuration diagram of an example of the reaction chamber.

FIG. 3 is a graph showing a relationship between discharge time and residual hydrogen concentration.

FIG. 4 is a graph showing a relationship between a heating time and a residual hydrogen concentration.

FIG. 5 shows an example of a conventional a-Si thin film manufacturing apparatus.

[Explanation of symbols]

1 ... a-Si thin film manufacturing apparatus 2 ... substrate 15 ₁
~ 15 ₄ ...... Reaction chamber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 31/04 H01L 31/04 V (72) Inventor Naoto Tsuji 523 Yokota, Sanmu-cho, Sanmu-gun, Chiba Nihonshin Sora Technology Co., Ltd.Chiba Super Materials Research Laboratory (72) Inventor Taro Morimura 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Prefecture Nippon Masaki Technology Co., Ltd.Chiba Super Materials Research Laboratory (72) Inventor Yoko Koshiba 523 Japan Vapor Technology Co., Ltd.Chiba Super Materials Laboratory (72) Inventor Takaki Yasui 523 Yamatake-cho, Yamatake-gun, Chiba Prefecture Japan Vacuum Technology Co., Ltd.Chiba Super Materials Laboratory (72) Inventor Kazuya Saito Ibaraki 5-9-7 Tokodai, Tsukuba, Japan F-term (reference) in Tsukuba Super Materials Research Laboratory, Japan Vacuum Engineering Co., Ltd. 4G072 AA03 BB09 FF01 GG03 HH0 4 NN13 QQ06 RR01 RR11 RR25 UU30 4K030 AA06 BA30 BB05 CA06 FA01 HA03 LA18 5F045 AA08 AB04 AC01 AC16 AF07 BB08 DP04 DQ17 EB08 EE14 EF05 EH05 EH14 EN04 5F051 AA05 BA14 CA07 CA32 CA32 CA21

Claims (3)

[Claims] An amorphous silicon thin film manufacturing method for forming an amorphous silicon thin film on a substrate surface, comprising introducing a source gas into a vacuum atmosphere and generating the source gas plasma to form an amorphous silicon thin film on the substrate surface. After that, an inert gas, or a hydrogen gas, or a gas obtained by adding a hydrogen gas to an inert gas is introduced as a processing gas into a vacuum atmosphere in which the substrate is placed, and a plasma of the processing gas is generated, and the amorphous gas is generated. A method for manufacturing an amorphous silicon thin film, comprising exposing a surface of a silicon thin film to the plasma and performing a dehydrogenation treatment on the amorphous silicon thin film. 2. The method for producing an amorphous silicon thin film according to claim 1, wherein after the amorphous silicon thin film is formed on the surface of the substrate, the dehydrogenation treatment is performed without exposing the substrate to the atmosphere. 3. The method for producing an amorphous silicon thin film according to claim 1, wherein the formation of the amorphous silicon thin film and the dehydrogenation treatment are performed in the same reaction tank. .