JPS62130277A - Method and apparatus for producing amorphous silicon thin film - Google Patents

Abstract

PURPOSE:To deposit a thin film having uniform film thickness and film quality on a base plate by feeding a gaseous raw material contg. silicon compd. to a reaction chamber of an electrode division type plasma chemical vapor deposition apparatus and impressing uniformly high frequency voltage to the whole electrodes which constitute the vapor deposition apparatus and are divided into plural sections. CONSTITUTION:A plasma chemical vapor deposition apparatus is constituted of a reaction chamber 1, an electric power source 18 and an electric power distributor 30 and e.g. three pieces of division type electrodes 40, 41, 42, a top electrode 12 and a base plate 20 ar arranged in the reaction chamber 1. The introduction ports 3, 4, 5 of a gaseous raw material are provided to the under parts of the division type electrodes and a gas discharge port 16 is provided to the reaction chamber 1. The gaseous raw material contg. silicon compd. is introduced into the inside of the reaction chamber 1 through the introduction ports 3, 4 5 and high frequency voltage is uniformly impressed to three pieces of division type electrodes 40, 41, 42 via the electric power distributor 30 from the electric power source 18. Silicon compd. is decomposed by glow discharge generated between the division type electrodes and the top electrode 12 to deposit a thin film on the base plate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing an amorphous silicon thin film used as a solar cell, etc., and a plasma CVD apparatus for manufacturing the thin film.

More specifically, the present invention relates to a method of introducing a raw material gas into a plasma CVD apparatus and forming a uniform thin film of silicon under specific power conditions, and a plasma CVD apparatus having a split electrode used for this purpose.

(Conventional Technology) In recent years, research has been actively promoted to utilize sunlight as a next-generation energy source in place of fossil fuels such as oil and coal. Among these systems, systems that extract the light energy of sunlight as electrical energy using solar cells have been viewed as extremely promising since the practicality of amorphous silicon batteries, known as photovoltaic power generation, was confirmed.

Amorphous silicon solar cells are made by depositing a thin film of amorphous silicon on a substrate such as glass, stainless steel, or polyimide through a conductive film, and then coating the surface with an antireflection film. The addition controls valence electrons and forms the p layer, 1 layer (containing no impurities), and n layer.

Such an amorphous silicon thin film is generally formed by a method using a plasma CVD apparatus using glow discharge. As the plasma CVD apparatus, a parallel plate type CVD apparatus as shown in FIG. 3 is usually adopted.

That is, the reactor (1) has electrodes (10, 12), a raw material gas inlet (3), a gas outlet (1B), and a power source (1).
8) and is configured to deposit an amorphous silicon thin film onto a substrate (20) attached to an upper electrode (anode).

On the other hand, a plasma CVD apparatus as shown in FIG. 4 has been proposed as an apparatus suitable for forming a single layer of amorphous silicon (Japanese Patent Laid-Open No. 59-213176).

This device has three sets of electrodes (10 and 12) in the reaction chamber (1).
, 11 and 14. and 13 and 15), and the source gas is plasma decomposed by power supplies (18, 19 and 21) connected to each set, and the content of impurities is controlled within a desired range onto the substrate (20) introduced into the device. The purpose is to form an i-layer of silicon efficiently.

This device is used for the purpose of forming three i-layers of different film quality on a substrate by applying different powers from separate power sources to three sets of electrodes.

(Problems to be Solved by the Invention) In the conventional CVD apparatus, the lower electrode (cathode) is
As shown in (D) in the figure, since it is a single continuous flat plate, the applied voltage is uneven, especially in the center and the peripheral edges, and the thin film on the substrate also becomes uneven, causing the problem that the film thickness is not constant. It had been pointed out.

As the demand for solar cells increases, there is also an increasing need to increase the size of the CVD equipment as a whole, but in large CVD equipment, the area of the electrodes becomes larger, so the problem of non-uniform applied voltage as described above can be avoided. This requires technical measures such as flattening the electrodes and adjusting the distance between the electrodes.

However, at present, it is impossible to completely flatten the electrode surface, and furthermore, it is almost impossible to adjust the distance between the electrodes according to the voltage and install the upper and lower electrodes in parallel.

Even if the electrodes are placed accurately in the reaction chamber, repeated deposition of amorphous silicon on the substrate will result in excess thin film being deposited on the electrodes, making the electric field distribution uneven. A phenomenon also occurs in which the film formation becomes non-uniform.

Furthermore, in the CVD apparatus provided with the three sets of electrodes, a voltage is individually applied to each set of electrodes to form the i-layer in three stages, and the thickness of the thin film at each electrode is made uniform. It is not intended for this purpose. That is, according to the above publication, on the substrate introduced into the reaction chamber, 500 i-layers are first formed using electrodes 10 and 12 at a power of 50 W, and then 1000 i-layers are formed using electrodes 11 and 14 at a power of 30 W. is formed, and finally 20W is generated by electrodes 13 and 15.
2,500 i-layers are formed with a power of 2,500 and are sequentially moved from left to right, and the film quality at each stage is not adjusted.

That is, since this device is not intended to produce a homogeneous thin film, it is difficult to obtain a high-performance solar cell.

The purpose of the present invention is to improve the problem of non-uniformity of thin film thickness, which has been pointed out in conventional equipment, and to form a uniform large area amorphous silicon on a substrate, thereby efficiently producing solar cells. It is something to do.

(Means for Solving the Problems) In order to solve the above problems, the present inventors believe that plasma C
In addition to adopting a split type as the electrode structure of the VD device,
The inventors came up with the idea that it would be sufficient to apply a uniform voltage to each of the divided electrodes of such a CVD apparatus, and completed the present invention through extensive research.

That is, the present invention supplies a raw material gas containing a silicon compound into an electrode-divided plasma CVD apparatus, applies an average voltage to all of the electrodes divided into a plurality of sections constituting the CVD apparatus, and generates a glow discharge. The present invention relates to a method for producing an amorphous silicon thin film, which is characterized by depositing a thin film of uniform thickness and quality on a substrate by generating . in a plasma CVD apparatus that applies a high-frequency voltage to at least one of the plate electrodes, the plate electrode for applying high-frequency voltage is divided into a plurality of sections, and the high-frequency voltage applied to each section is separately controlled. The present invention relates to a plasma CVD apparatus for producing an amorphous silicon thin film, characterized in that it is equipped with a power supply device to uniformize the thickness and quality of a coating on a substrate.

The present invention is characterized by a method for producing an amorphous silicon thin film using a plasma CVD apparatus having a specific structure of electrodes and a power supply device, and the plasma CVD apparatus for producing the thin film.

First, an overview of the present invention is shown in FIGS. 1 and 2 (A) to (C).
).

The outline of the plasma CVD apparatus of the present invention is shown in FIG.
0). The reaction chamber is equipped with split electrodes (40,
41 and 42) and the upper electrode (12) and substrate (20
) are arranged, and source gas inlets (3, 4, and 5) and a gas outlet (16) are provided below the split electrode. The split-type electrode is a flat plate electrode placed opposite to the upper electrode, and is characterized in that it is divided into multiple sections with approximately equal areas.

Square and circular flat electrodes are usually used, but square plate electrodes are shown in Figure 2.
It is divided into (A) 9 divisions, (B) 4 divisions, and (C) 16 divisions. Plasma CVD apparatuses include flat plate electrode types, cylindrical electrode types, etc., and the present invention can obtain great effects when the flat plate electrode type electrode is divided.

If the number of divisions is 3 or less, the effect of making the film quality and thickness of the thin film uniform is small, and if it is 16 or more, the device and its manufacturing process become complicated, which is not preferable. Each section is configured to have approximately equal area so that the applied voltages are averaged. An earth shield (50) is provided around the electrode to prevent abnormal discharge.

The power supply device of the present invention is a high frequency oscillator capable of generating a high frequency voltage for decomposing raw material gas by glow discharge, and may be either an AC power source or a DC power source. The power distribution device is composed of a distributor (31) and power amplifiers (35, 36 and 37). The divider averages and distributes the high frequency voltage generated by the power supply to the power amplifier, and the power amplifier applies the high frequency voltage from the divider to each of the divided electrodes. The power source may be configured such that a dedicated power source is installed independently for each divided electrode, or power is supplied to each divided electrode via a distributor and an attenuator.

Next, the method for manufacturing an amorphous silicon thin film of the present invention will be specifically explained.

A silicon compound as a raw material gas is supplied to the reaction chamber through a gas inlet. Between the divided electrodes and the upper electrode, the silicon compound is decomposed by glow discharge generated by the applied high frequency voltage and deposited on the substrate. When the flat plate electrode is square, the electrode is divided into 4 to 16 sections with approximately equal areas, so the high frequency voltage from the power source is applied to each divided electrode on average. For example, the plasma CVD apparatus shown in FIG.
The 9-divided electrode shown in Figure (A) is adopted, and the high-frequency voltage from the power source is supplied to the power amplifier via a distributor at a voltage of 1/9, and the average voltage is applied to the divided electrode.

As a result, even if the substrate has a large area, an amorphous silicon thin film having a constant thickness and good film quality can be deposited on the substrate -1-.

Equal voltage is applied to each divided electrode, but Pradama CV
Depending on the distance between the electrodes of the D device, the angle at which the electrodes are attached, etc., the film thickness may not be uniform between the center and peripheral edges of the substrate.

In this case, it is sufficient to adjust the applied voltage of the power amplifier to change the voltages of the divided electrodes at the central portion and the divided electrodes at the peripheral ends very slightly.

If a plasma CVD device is used for a long period of time, excess amorphous silicon will adhere to the electrode surface, which may cause the applied voltage to become uneven, but in this case, the applied voltage of the power amplifier can be adjusted in the same way. .

Although the case where only a silicon compound is used as a raw material gas for amorphous silicon has been described above, boron or phosphorus can also be added to a silicon compound (silane, disilane, etc.).

In addition, in recent years, in order to mass-produce amorphous silicon thin films, plasma CVD has been installed with multiple high-frequency voltage application electrodes.
Although D devices have appeared, the present invention is equally applicable to such devices.

(Function) Plasma C for manufacturing amorphous silicon thin film of the present invention
In a VD device, the divided electrode has the function of applying an average high frequency voltage from a power source via a distributor and a power amplifier.

The power amplifier has the function of adjusting the voltage applied to each section of the split-type electrode and uniformizing the thickness and quality of the amorphous silicon deposited on the substrate.

(Effects of the Invention) The present invention is a plasma CVD apparatus having a split electrode, and a method for producing an amorphous silicon thin film in which an average voltage is applied to each split electrode using the apparatus. It is extremely useful industrially because it has the following effects: 1. It is possible to stably mass-produce large-area amorphous silicon thin films, and cheap and high-quality solar cells can be manufactured.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a plasma CVD apparatus for producing an amorphous silicon thin film according to the present invention, and FIG.
D is an explanatory diagram of the electrode portion of the device (A to C are the present invention, D and E are the prior art). FIGS. 3 and 4 are explanatory diagrams of a conventional plasma CVD apparatus for producing amorphous silicon thin films. 1 Reaction chamber 3.4.5 Raw material gas inlet 10.11.1
3 Electrode 18 Power supply 20 Substrate 30 Power distribution device 40.41.42 Split type electrode Fig. 1 Fig. 2 Fig. 3
Figure 4 Procedure Amendment
Document 1, Indication of the case 1985 Patent Application No. 175083 2, Title of the invention 3, Representative of the person making the amendment Akira Matsuyama 4, Agent 5, Date of the amendment order Voluntary action 6, Subject of the amendment "Detailed Description Column" and "Drawings" 7, Contents of Amendment (1) The following (Example) on line 20 of No. 1LL''f of the specification:
join. (Example) In a plasma CVD apparatus where both the anode and cathode are approximately 40 x 40 cm, the cathode is approximately 20 x 20 cm.
The uniformity of the film thickness of an amorphous silicon film produced using an apparatus divided into four electrodes of m was investigated. The manufacturing conditions were: distance between electrodes 40III11. Silane (100%) gas was used as a raw material gas at 100 s e c M (
standard cubic cenmeter per minute)
The operating pressure was 0.3 Torr, the input power was 20 W (5 W was applied to each divided electrode), the substrate temperature was 225°C, and the film forming time was 60 minutes. The film thickness distribution on the diagonal line was measured. The results are shown in FIG. In the figure, Ocm indicates the center of the glass. The black circles are the results obtained using the device of the present invention in which the cathode electrode is divided into four parts. The thickness of the amorphous silicon film produced using the conventional apparatus (without dividing the cathode) was as shown in the white circle. From this, it can be said that the film thickness produced by the apparatus of the present invention has excellent uniformity, and is suitable for producing large-area amorphous silicon solar cells. (2) The following sentence is added to the 8th line of page 13 of the specification. "Fig. 5 is a graph showing the film thickness uniformity of the amorphous silicon thin film of the example." (3) Attached drawing, No. 5
Add a diagram. Figure 5 Trap Thick Procedural Sleeve Book December 1986 241” Special, 1'1 Director-General Black 1) Akio Tono 1゛ 11 Indications 2, Name of Invention Method and Apparatus for Manufacturing Amorphous Silicon Thin Film 3, Capture +
Relationship with the case of the person doing E Hande'1 Applicant's address Higashi ni ξ Miyata-ku - Tsuhashi-'' - No. 1 No. 1 Name Toa Fuel Industries Co., Ltd. Representative Akira Matsuyama 4; Agent address: Postal code: 100 Chiyoda-ku, Tokyo - Tsubashi-cho 1'' 1-1-5 Date of amendment order November 250, 1985 (Date of dispatch) 6. Subject of amendment f - Continuation of amendment letter 1988 February 70, 2015 Mr. Michibe Uga, Director General of the Mochiji Office 1, Incident Indication 1985 Patent Application No. 175083 Amorphous Silicon Thin Film Manufacturing Method and Apparatus Address
Chiyoda-ku, Tokyo - Tsuhashi-cho January number 1 Name: Toa Fuel 1-Gyo Co., Ltd. Representative: Akira Matsuyama 4, Agent address: Postal code 100 Chiyoda-ku, Tokyo - Tsuhashi-cho 1] 1-1 No. Toa Fuel Industries Co., Ltd. Tsujiuchi (Telephone number 286-5188) Name Patent attorney (8791) Kubo 1) υ [Heisei 5
, ) + 17 Date of city order Voluntary explanation column" and "Drawings"

Claims (1)

[Scope of Claims] 1) Source gas containing a silicon compound is subjected to electrode split plasma C
A thin film of uniform thickness and quality is deposited on the substrate by supplying it to the reaction chamber of the VD device and applying a high frequency voltage on average to all of the electrodes divided into a plurality of sections constituting the CVD device. A method for producing an amorphous silicon thin film, characterized by: 2) In a plasma CVD apparatus having at least two plate electrodes arranged opposite to each other and applying a high frequency voltage to at least one of the plate electrodes, the plate electrode for applying the high frequency voltage is divided into a plurality of sections. , for manufacturing amorphous silicon, characterized in that the film thickness and film quality of the coating on the substrate can be made uniform by being equipped with a power supply device for separately controlling the high frequency voltage applied to each section. Electrode split type plasma CVD equipment. 3) The device according to claim 2, wherein the high-frequency voltage application flat plate electrode is divided into 4 or more and 16 or less sections. 4) The device according to claim 2 or 3, wherein the power supply device has a distributor between the power source and the flat electrode.