JPH0274028A - Thin film manufacturing device for amorphous silicon solar cell - Google Patents

Abstract

PURPOSE:To make the device compact further eliminating the removal work of any by-products produced during the filming process, cutting down the manufacturing man-hours and augmenting the rate of operation by a method wherein thin films are formed on the glass substrates comprising the inner wall surfaces of a plasma cracking chamber making use of the plasma cracking chamber composed of a framework and the glass substrates. CONSTITUTION:A space part encircled by a framework 18 and two sheets of glass substrates 19 is formed into a plasma cracking chamber 17 using the glass substrates 19 to form thin films and then the air inside the chamber 17 is exhausted from one end of the framework 18 while filming gas is led in from the other end and the gas is impressed with RF power using a cathode electrode 15 arranged inside the plasma cracking chamber 17 and two anode electrodes 16 arranged near the peripheral parts of the chamber 17 to start the plasma cracking process. The title device is constituted to form transparent electrodes films and amorphous silicon films by cracking the filming gas after heating the glass substrates 19 by a heater 24 provided around the anode electrodes 16. Through these procedures, the whole device can be made compact in high manufacturing efficiency, thus cutting down the manufacturing cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for manufacturing a thin film using a high frequency plasma reaction, which is used in an amorphous silicon solar cell.

(Prior Art) Figure 2 shows a partial cross-sectional perspective view of an amorphous silicon solar cell, and generally has a structure in which unit cells are connected in series on one substrate as shown in Figure 2. It has become.

That is, in FIG. 2, the amorphous silicon solar cell is
Transparent electrodes 112a, 2b, 2c are formed in the shape of strips on a glass substrate 1, and on top of these are amorphous silicon M3a, 3b, 3c, which are photovoltaic force generating parts, and on top of these, a metal electrode film 4a, 4b and 4c are formed so as to be stacked one after another, and for example, the transparent electrode film 2b of a unit cell is electrically connected to the transparent electrodes 1112a and 2c of an adjacent unit cell.

For each thin film that constitutes this solar cell, transparent T8i
Films 2a, 2b, 2c are made by thermal CVD method, amorphous silicon film 3
a, 3b, 3c are plasma CVD metal electrode films 4a, 4
b and 4c are formed by a vapor deposition method, a sputtering method, a printing method, etc., but in order to configure each of these i III as shown in Fig. 2, a processing step using a laser or the like is required between each formation process. It is normal.

Here, an amorphous silicon thin film 3a of a solar cell is shown.

An outline of the plasma CVD apparatus used to form 3b and 3c will be described. Figure 3 is a cross section of the main parts showing the configuration of the device, and the main components of this device are the reaction vessel 5.
1. Exhaust system 61 which evacuates the reaction container 5; Gas supply system 7. which supplies film forming gas into the reaction container 5; Cathode ti8.
RF iJ connected to anode electrode 9 cathode electrode 8
Source 10. Glass substrate 1 located on anode electrode 9. It is located below the anode electrode 9 and includes a heater 12 and a heater TX source 13 for heating the substrate l. In the case of a solar cell, the above-mentioned transparent electrodes 2a, 2b,
2c has already been formed, but is not shown here.

To form an amorphous silicon thin film on such a glass substrate 1 using the above VI setting, first, the reaction vessel 5 is evacuated by the evacuation system 6 until the degree of vacuum is several m Torr or less. A film forming gas such as S i It a containing S i II a or h is supplied from the gas supply system 7 into the reaction chamber 2S5, and is partially evacuated by the vacuum exhaust system 6 to reduce the pressure inside the reaction chamber 5 to I Torr. Keep it at culm level. Thereafter, power is supplied from the RF power source 10 to the cathode bridge 8 and the anode electrode 9 to generate plasma between the picture electrodes 8 and 9. At this time, the substrate l on the anode electrode 9, which is heated to about 200'C by the heater 2 by the power source 13, is heated by the plasma generated between the two electric scrapers 8 and 9, as shown in FIG. It is possible to form a non-crystalline n-silicon thin film.

After forming the amorphous silicon thin film in this way, a portion of it is cut using a laser or the like, and then a metal electrode is attached and processed to form the final amorphous silicon solar cell shown in Figure 2. It becomes.

Plasma C that forms the amorphous silicon film of solar cells
Although I have described an apparatus using the VD method, in principle, the above-mentioned apparatus can be used with yIII! Even if it is possible to form a
Multiple arrangements of electrodes and substrates within one reaction vessel have also been practiced. However, in this case, the reaction vessel, which is a vacuum vessel, must be made larger, and as a result, the structure to provide the necessary pressure resistance to the reaction vessel and the equipment for both sides to increase the gas exhaust capacity become large-scale. This results in a large amount of equipment costs, which does not necessarily lead to increasing mass productivity and reducing the manufacturing cost of solar cells. Furthermore, in the above-mentioned apparatus, amorphous silicon sticks to the wall of the reaction vessel as a reaction byproduct during film formation, and this impedes the solar cell characteristics, so this adhesion must be removed periodically. Since this method requires cleaning of the reaction vessel from time to time, there is a problem in that the operating rate of the apparatus is reduced.

In order to solve these problems, there is a thin film manufacturing apparatus described in Japanese Patent Application No. 63-59867, currently pending by the same applicant, and an outline of this apparatus is shown in FIG. 4 and FIG. 5. This device replaces the reaction vessel, which is a conventional vacuum vessel, with y4
Using the glass base Fi19 forming the membrane, the framework 18 is attached to two glass bases Fi19 with a plurality of supports 23 interposed therebetween.
A space surrounded by a space is formed and used as a plasma decomposition chamber 17, and the gas is evacuated from one end of the framework and a film-forming gas is introduced from the other end. Plasma decomposition is caused by applying RFit force using the cathode in 15 placed inside and the two anode electrodes 16 placed near the outer peripheral surface of the plasma decomposition chamber 17, and the heater 24 placed around the anode electrode 16 causes plasma decomposition to occur. The glass substrate 19 is heated and serves as the inner wall surface of the plasma decomposition chamber 17.
The structure is such that a transparent electrode film and a crystalline silicon film are formed thereon by decomposition of the film-forming gas, and the glass substrate 19 itself on which the thin film is formed becomes the inner wall surface of the plasma decomposition chamber 17. Therefore, even if the area of the thin film increases, there is no need for a large reaction vessel or accompanying capacity-resistant equipment.Moreover, the support body 23 disposed inside the plasma decomposition chamber 17 can be This support body 23 serves as a reinforcement to prevent the glass substrate 19 from being deformed or damaged even when the pressure is reduced.
Since no thin film is formed in the areas in contact with the support 23, it also serves as a mask, and when forming the transparent electrode film and the amorphous silicon film, the support 23 By determining the contact position between the glass substrate 19 and the glass substrate 19, it becomes possible to arrange these thin films produced by decomposition of the film forming gas at desired positions in the form of strips without any post-processing. In this way, we were able to provide a device that has a greater mass production effect than conventional devices and operates more efficiently.

By using the above device for arranging a support in the plasma decomposition chamber, it is effective to prevent the glass substrate from being damaged when the plasma decomposition chamber is depressurized, and a thin film can be formed without post-processing. Low-cost solar cells can be obtained from

[Problems to be Solved by the Invention] However, subsequent research by the present inventors revealed that the following points still need to be solved. During film formation, it is inevitable that amorphous silicon will adhere to the wall surface of the support in the plasma decomposition chamber as a reaction byproduct, and this will impede the solar cell characteristics. Removal of deposits and cleaning of the support wall surface are required.

In addition, in devices that use a glass substrate instead of a reaction vessel that is a vacuum vessel, damage to the glass substrate due to reduced pressure during thin film formation, or S
It cannot be said that there is no leakage of film-forming gases such as a. This impairs workability during the formation of solar cell thin films and reduces the effectiveness of mass production.

The present invention has been made in view of the above points, and its purpose is to improve the airtightness of the plasma decomposition chamber without arranging a support for an apparatus that uses a glass substrate directly as the wall surface of the plasma decomposition chamber. An object of the present invention is to provide a thin film manufacturing apparatus for an improved amorphous silicon solar cell.

[Failure to solve the problem]

In order to solve this problem, the apparatus of the present invention uses a glass substrate on which a thin film is formed in place of the reaction vessel, which is a conventional vacuum vessel, and uses plasma decomposition in a space surrounded by a framework and two glass substrates. The chamber is evacuated from one end of the framework, and the film forming gas is introduced from the other end. At the same time, RFi force is applied to cause plasma decomposition, and the glass substrate is heated by the heater installed around the anode T4h, and the film is heated by the decomposition of the film forming gas on the glass S plate that forms the inner wall of the plasma decomposition chamber. The anode electrode is configured to form a transparent electrode film and an amorphous silicon film, and the anode electrode has a plurality of convex support parts that contact the glass substrate, and an area that is approximately the same as the opening area (film formation area) of the framework. A first vacuum exhaust port communicating with the concave space is provided, and the anode electrode is in close contact with the glass substrate and framework of the plasma decomposition chamber via sealing materials, respectively. A second vacuum exhaust port is provided that communicates with the space formed by the glass substrate, the framework, and the respective sealants.

[Effect]

Since the apparatus of the present invention is configured so that the glass substrate itself on which the thin film is formed becomes the inner wall surface of the plasma decomposition chamber,
The point that even if the area of the thin film increases, there is no need for a large reaction vessel or accompanying equipment, as disclosed in the above-mentioned Japanese Patent Application No. 63-598.
The device is similar to the device disclosed in No. 67, but without providing a plurality of supports, and in addition, when glass 54Fi is attached to the anode electrode and the concave space is reduced to a vacuum,
The convex support plays a reinforcing role to prevent the glass substrate from being deformed or destroyed, and by making the concave space almost the same area as the opening of the framework, it is possible to prevent the inside of the plasma decomposition chamber from forming a thin film. This prevents the glass substrate from deforming or breaking due to the generation of differential pressure when the pressure is reduced.

In addition, the anode electrode is the glass u +1 of the plasma decomposition chamber.
The anode electrode and the plasma decomposition chamber are brought into close contact with each other through the sealant and the glass substrate is vacuum-adsorbed by vacuuming the space formed by the seven-node electrode, the glass substrate, the framework, and the sealant. The plasma decomposition chamber is kept in close contact with the framework via a sealing material.

Also, in the unlikely event that this airtightness cannot be ensured, S i II a
Even if the film-forming gas such as 1 or 1 leaks, the space formed by the anode electrode, glass substrate, framework, and sole material is reduced to a vacuum and evacuated to prevent the film-forming gas from leaking outside the device. It becomes a sealed container with a double sole structure to ensure safety.

〔Example〕

FIG. 1 is a cross-sectional view showing the structure of the thin film manufacturing apparatus for amorphous silicon solar cells of the present invention, and is similar to the above-mentioned FIGS. 4 and 5.
The same reference numerals are used for parts common to the figures. In FIG. 1, two glass substrates 19 are brought into contact with a framework 18 via a sealant 22, and the framework 18 and two glass substrates Fi 19
A plasma decomposition chamber 17 is formed as a space surrounded by. A grid-shaped cathode electrode 15 is arranged inside the plasma decomposition chamber 17, and is connected to the RF power supply 14 via an insulated airtight terminal (not shown) provided on the framework 18.

A gas introduction pipe 20 for introducing a film forming gas is attached to the opposite upper side of the framework 18, and a gas exhaust pipe 21 is attached to the lower side.

Further, two anode electrodes 16 are disposed opposite to each other on both sides of two glass substrates 19 forming the plasma decomposition chamber I7, and are in contact with the glass substrates 19 via a sealing material 22a. Anode electrode 1 in contact with glass substrate 1 19
6 includes a plurality of convex support portions 30 that abut against the glass substrate I9 at a position facing the opening surface of the rectangular frame IJI 18 opening in the width direction, and a plurality of convex support portions 30 having approximately the same area as the opening surface of the frame All 18. A recessed space a, is formed, and the recessed space a, is connected to an evacuation system (not shown) via a first evacuation port 32. The anode electrode 16 is a frame!
18 are in contact with each other via a sealing material 22b, and the anode electrode 16, the framework 18, the glass substrate 19, and the sealing materials 22, 22a, 22b, ! The space surrounded by : communicates with an evacuation system, which is also not shown, via a second evacuation port 33. Furthermore, each glass group Fi
Heaters 24 for heating the electrodes 19 are provided along these T4Fr near the two 7-node electrodes 16, respectively.

The configuration of the thin film manufacturing apparatus of the present invention has been described above, and next, the procedure for assembling this apparatus and forming a thin radius will be described. First, the gas inlet pipe 20 and the gas discharge pipe 21 are attached, and the frame & [118 with the cathode electrode 15 attached inside it]
As shown in the figure, place the sole materials 22 and 22b in the opening grooves on both sides.
Anode electrode shown vertically in the figure]6
The heater 24 is placed horizontally with its long vertical direction and with the convex support portion 30 facing upward. This is because the frame &ll
18. Next, the glass substrate 19 is applied to the sealing material 22a fitted in the groove provided on the outer periphery of the concave space a of the anode electrode 16, and the first evacuation is performed. The glass substrate 19, which evacuates the concave space a communicating with the opening 32, is kept airtight by the sealing material 22a and is fixed to the anode electrode 16 by suction. At this time, 1 kg・f/
CD pressure is applied from the outside, so if this exceeds the glass strength, it will burst. The convex support portions 30 prevent the glass substrate 19 from being deformed or damaged by resisting this external pressure. For example, if the glass substrate 19 has a thickness of 3 mm, the convex support portions 30 are arranged at intervals of a. By forming 30, breakage can be prevented. Next, the unit composed of the anode electrode 16 and the heater 24 is erected vertically as shown in FIG.
It abuts against the framework 18 via. After that, the anode electrode 16, the framework 18, the glass substrate 19, and the sealing material 22
, 22a and 22b is evacuated from the second vacuum exhaust port 33, and the anode electrode 16 and the glass substrate 19 are vacuum-fixed to the frame &g18. As a result, the plasma decomposition chamber 17 is kept airtight by the sealing material 22 fitted in the frame 18 and the glass substrate 19. Next, the plasma decomposition chamber 17 is connected to the gas exhaust pipe 21. After evacuation to several m Torr or less using a vacuum device (not shown), the film forming gas is introduced into the plasma decomposition chamber 17 from the gas introduction pipe 20 by a gas supply system (not shown), and a part of it is passed through the gas exhaust pipe 2.
The plasma decomposition chamber 17 is evacuated at 1 Torr and kept at a pressure of about 1 Torr. After that, high frequency power is applied from the RF power source 14 to the cathode electrode 15 and the anode electrode Bi 16,
By generating a plasma of the film-forming gas inside the plasma decomposition chamber 17, a film formed by the decomposition of the film-forming gas is placed on the glass substrate 19, which is used as the wall surface of the plasma decomposition chamber 17 and is heated to about 200°C by the heater 24. A thin film can be formed.

After removing the glass substrate I9 through the reverse process of the above steps, a portion of the glass substrate I9 is cut using a laser or the like, and then a metal electrode is attached and processed, resulting in the final amorphous structure shown in Figure 2. A high quality silicon solar cell can be obtained.

[Effects of the invention] The thin film manufacturing equipment for amorphous silicon inner corner batteries requires a large reaction vessel in order to achieve mass production efficiency, and requires large-scale ancillary equipment to increase gas exhaust capacity. Although it was expensive, the apparatus of the present invention uses a plasma decomposition chamber consisting of a framework and a glass substrate to form a thin film on the glass substrate that forms the inner wall of the plasma decomposition chamber, as described in the examples. Therefore, the device is not only compact, but also sufficiently compatible with large-area amorphous silicon solar cells. In addition, most of the plasma decomposition chambers where In formation is performed are made of glass substrates and do not use glass substrate supports, which eliminates the need to remove by-products generated during film formation, reducing manufacturing man-hours and increasing operational efficiency. The improvement in the rate is remarkable. Furthermore, since the anode electrode is made into an airtight container with a double seal structure, safety and workability can be significantly improved. That is, when a solar cell is manufactured using the apparatus of the present invention, the entire apparatus becomes compact, which reduces equipment costs, and produces extremely large effects such as high manufacturing efficiency and reduced manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main part of an embodiment of the present invention, FIG. 2 is a sectional view of the main part showing the structure of an amorphous silicon solar cell, FIG. 3 is a sectional view of the main part of a conventional device, and FIG. The figure is a cross-sectional view of the main part of the apparatus according to the prior application, and FIG. 5 is a partial cross-sectional perspective view of the apparatus of FIG. 4 when the cathode electrode is provided inside the plasma decomposition chamber. 1.19...Glass base, 2a, 2b, 2c...
Transparent electrode film, 3a, 3b, 3c...amorphous silicon film, 4a, 4b, 4c...gold r/s electrode film, 5...reaction vessel, 6...exhaust system, 7. ...Gas supply system, 8.1
5... Cathode electrode, 9.16... Anode electrode,
10.14... RFiit source, 12, 24... Heater, 13... Heater 1 as source, 17... Plasma decomposition chamber, 18... Framework, 20... Gas introduction pipe, 21...・
・Gas exhaust pipe, 22.22 a, 22 b...Sealing material, 23...Support, 25...Airtight container, 30.
...Convex support part, a, ...Concave space, 32...First
vacuum exhaust port, 33... second vacuum exhaust port. Figure 29. Herme 1,000 2 seals.

Claims (1)

[Scope of Claims] 1) An apparatus for producing thin films of amorphous silicon solar cells using a plasma CVD method, which comprises: a. a rectangular framework opening in the width direction; and a sealing material on both opening surfaces of the framework. Two parallel glass substrates that are in close contact with each other are arranged parallel to each glass substrate approximately in the center of a box-shaped space surrounded by a frame with these glass substrates, and one end is connected to the outside of the box-shaped space to transmit RF a plasma decomposition chamber including a cathode electrode connected to a power source, a gas inlet pipe and a gas exhaust pipe arranged in the framework; b) a plurality of glass substrates each abutting on the outer surface of each of the two glass substrates forming the box-shaped space; a convex support portion, a concave space having an area approximately the same as the opening area of the framework, a first vacuum exhaust port communicating with the concave space, and a space airtightly formed by each glass substrate, the framework, and a sealing material. two anode electrodes having a communicating second vacuum exhaust port, c, two heaters each disposed near the two anode electrodes and heating each glass substrate in the plasma decomposition chamber via these anode electrodes. 1. A thin film manufacturing apparatus for amorphous silicon solar cells, characterized by comprising: