JPS59219927A - Plasma cvd device - Google Patents

Abstract

PURPOSE:To remove in a short time a reaction product adhered on mutually facing electrodes in a reaction chamber without opening the reaction chamber by a method wherein two rolls are used respectively as the delivery roll and the wind- up roll of a thin belt to shield the second electrode in electrically insulated condition passing nearby the second electrode on the first electrode side. CONSTITUTION:The titled device is so constructed as to make a thin belt 20 wound on a roll 21 to be wound up by a roll 22 passing between a first electrode 3 to be used both as a susceptor and a facing electrode 4, and the plane of the high polymeric thin belt 20 is formed according to tension between both the rolls thereof. The rolls 21, 22 may be constructed of a metal or an insulator, and made to have the same electric potential with the facing electrode 8. The insulating belt 20 is made to approach the electrode 4 as much as possible to reduce the quantity to be deposited on the facing electrode 4. When a-Si deposited on the thin belt 20 exceeds the prescribed film thickness, the roll 22 is wound to supply the insulating belt of a fresh surface. The deposited a-Si is wound up together in the roll 22 according to winding up thereof. After winding up is finished, by performing plasma etching of the reaction chamber, cleaning is attained without exposing the reaction chamber to the open air.

Description

[Detailed Description of the Invention] [Technical Field to Which the Invention Pertains] The present invention involves generating a glow discharge by applying a voltage between a first electrode that also serves as a support for a substrate and a second electrode that is placed opposite to the first electrode. plasma CV, which decomposes reactive gases and deposits thin films of amorphous semiconductors or insulators on substrates.
Regarding D device.

[Prior art and its problems]

Amorphous conductor solar cells using amorphous semiconductors, particularly amorphous silicon, are being researched and developed as a promising candidate for the low cost ratio of solar cells that directly convert light into electrical energy. An amorphous silicon (hereinafter referred to as a-8i) solar cell is made of a p-type layer, a non-doped a-8i layer, and a non-doped a-8i layer on a conductive substrate such as metal or a transparent insulating substrate such as glass with a transparent conductive film on the upper surface. The a-Si layer having a pin junction is formed as a photovoltaic layer by forming an 8i layer and an n-type a-8i layer with a thickness of a few hundred^, a few μm, and a few hundred and several hundred layers, respectively. In each of these layers, it is also well known that the efficiency can be improved by using an a-8iC layer with good light transmittance or a microcrystalline a-8i layer with high conductivity as a p-type layer and an n-type layer. It is.

A capacitively coupled glow discharge device shown in FIG. 1 is known as a device for forming this a-8i layer. Coupled glow discharge devices are suitable for manufacturing large area solar cells. An electrode 3 equipped with a heater 2 is attached to the inside of the bell jar 1, and an electrode 4 is arranged opposite to the lower surface of the electrode 3. a- The substrate 5 on which another layer is formed is attached to the upper electrode 3 and kept at a temperature of 200 to 300'O by the heater 2. The internal space of the bell jar 1 is a gas introduction pipe 6
It is connected to a gas supply line via a gas supply line, and to an exhaust system via an exhaust pipe 7. For example, when forming a p-type A-81 layer, mix appropriate amounts of silane gas and diporane gas,
Introduce it to the bell jar through the system, and balance it with the exhaust system.
Maintain at 10 Torr. Using a high frequency power source 8 from the outside, high frequency power is applied between both opposing electrodes 3 and 4 to decompose the internal gas and deposit a p-type a-Si layer on the substrate 5. Non-doped layer, n-type a-8! In forming the layer, a gas of an appropriate composition is decomposed by glow discharge and deposited in a similar manner.

FIGS. 2(a), 2(b) show enlarged views of the upper electrode.

(a) is a view of the upper electrode 3 holding the substrate 5 viewed from below.

The electrode 3 is attached to the support to which the heater 2 is built in by the support claw 9, as shown in (a) and the cross-sectional view (b). It is supported by

The substrate 5 is fitted into a hole made in the electrode 3, and in order to improve electrical contact and thermal contact between the substrate 5 and the electrode 3, a metal plate is held down from above the substrate 111 and fixed. has been done. The surface of the substrate faces the electrode 4 and is exposed to the electrode 4. When a high frequency voltage is applied between the electrode 3 and the electrode 4 to generate a glow discharge, the electrode 3 and the substrate 5
Furthermore, a-8i adheres to the counter electrode 4 and other parts of the vessel wall.

If this a-S i adheres to a part other than the substrate, as the film continues to be formed, the film will peel off from this part, the inside of the glow discharge device will become dirty, pinholes will appear in the a-8i film, and a- The quality of the 8+ film deteriorated and the efficiency of the solar cell decreased. There is no problem because the electrode 3 is taken out and cleaned after each growth process, but the electrode 4, support 10, support claw 9, or vessel wall often gets stuck.
It is necessary to remove it and carry out cleaning work. In this case, not only does the film growth work have to be interrupted, but it also takes time to lower the temperature of the furnace, and the furnace itself is exposed to unfavorable conditions such as wiping and air exposure. It was necessary to take measures such as burning, and there were many problems in terms of the stability and operation rate of the equipment.

FIG. 3 shows an example of another device. This device is p-type, non-doped, and n-type a-8! By forming the layers in different reaction chambers and suppressing the effects of forming other layers during the growth of each layer,
The aim is to improve the controllability of the membrane. Before and after the three reaction chambers 11, 12, and 13, there is a front chamber 1 for mounting the substrate on the susceptor 3, and a rear chamber 15 for taking out the substrate on which the pin layer has been formed. It is connected to the exhaust system via the pulp 16. The susceptor 3 has a hole 31, as shown enlarged in FIG. 4, into which the substrate 5 is dropped. The holes 31 are arranged as shown in FIG. 2(a) when viewed from below. Board 5
The susceptor 3 equipped with the susceptor 3 is placed into the front chamber 14 by opening a gate valve (not shown).

The susceptor 3 is carried in by moving it on the wheels 17 that are lined up. When the susceptor 3 reaches a predetermined position in the front chamber 14, the gate valve is closed and the chamber 14 is evacuated via the valve 16. Next, the susceptor 3 is heated in the front chamber 14 so that the temperature of the substrate is 200 to 300'O. After the temperature stabilizes at 200 to 300° C., a gate valve (not shown) between the front chamber 14 and the reaction chamber 110 is opened, and the susceptor 3 is carried into the chamber 11 as the wheels 17 are driven. When the predetermined position is reached, the gate valve between the chambers 14 and 11 is closed, and a gas containing a mixture of silane and diborane is introduced into the reaction chamber 11.
Glow discharge decomposition is performed by a high-frequency electric field applied between the susceptor 3 and the counter electrode 4 under a condition of ~10 Torr, and a PMA-81 layer is deposited on the substrate 5 mounted on the susceptor 3. When the deposition of a predetermined film thickness is completed, the reaction chamber 11 is evacuated, the gate valve between the reaction chambers 11 and 12 is opened, and the susceptor 3 is moved to the reaction chamber 12. Thereafter, each a-8i layer is deposited in the same manner. N layer a-8 in room 13! Once formed, the susceptor 3 enters the chamber 15 through the gate valve between the reaction chamber 13 and the rear chamber 150. Here susceptor 3
After cooling to a certain temperature, for example, 100°C or less,
N2 gas is introduced into the tank to bring it to normal pressure, the gate valve is opened, and the susceptor 3 is taken out.

In the reaction chambers 11 to 13, a susceptor 3 and a counter electrode 4
The distance between 0 and 0 is the closest, which is 40 to 100.

Other distances, such as the distance between the susceptor 3 and the wall of the reaction chamber, the distance between the wheel 17 and the chamber wall, and the distance between the wheel 17 and the counter electrode 4,
and the distance between the counter electrode 4 and the counter electrode 4, for example, 1.
It has five times the distance. Therefore, it faces the susceptor 3'
Even if a high-frequency electric field is applied between the electrode 4 and a discharge is caused, the electric field is concentrated between these two electrodes, and most of the decomposed a-8i adheres. Since the susceptor 3 is taken out together with the substrate 5, processing such as cleaning can be performed at that time, but a large amount of a-8+ will accumulate on the counter electrode 4 in the reaction chamber, and if the amount becomes large, it will peel off and glow. It scatters during discharge and gets trapped on the substrate, causing pinhole formation or film quality deterioration. Therefore, until now, when the amount of deposition on the counter electrode exceeds a certain amount, the film formation operation is interrupted for cleaning.
The interior of the reaction chamber was then cleaned by introducing a gas such as CF4 and using means such as plasma etching. However, initial attempts to perform plasma etching required a long time, and the removed portions varied, making it impossible to perform an efficient cleaning operation.

Furthermore, when the reaction chamber is opened, there are problems such as the inner walls of the reaction chamber being contaminated with outside air, and there are also problems in terms of operating efficiency because the work is interrupted for a long time.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma CVD apparatus that can remove reaction products deposited on a counter electrode in a reaction chamber in a short time without opening the reaction chamber.

[Key points of the invention]

Two rolls are provided on both sides of a second electrode placed opposite to a first electrode that also serves as a support for the substrate, and each of the rolls passes near the second electrode side of the second electrode to electrically connect the second electrode. The above object is achieved by having a ribbon delivery roll and take-up roll that are insulated and shielded from each other.

[Embodiments of the invention]

FIG. 5 shows a first embodiment of the present invention. A thin strip made of a polymer film such as Teflon, polyimide, polyamideimide, polybismaleimide, etc., which is wound around a roll 21, passes between the first electrode 3, which also serves as a susceptor, and the counter electrode 40, and is wound around a roll 22. It is designed so that it can be taken. A flat surface of the polymer ribbon 20 is formed by the tension between the two rolls. The distance between electrode 3 and electrode 4 is 4
When the angle is 0 to 100, the distance between the ribbon 20 and the counter electrode 4 is 3
It was set to within 0. FIG. 5 is a sectional view of the apparatus shown in FIG. 4 in a direction perpendicular to the plane of the paper. Therefore, the susceptor 3 moves in a direction perpendicular to the paper plane of FIG.

Low/l'2L, 22 may be made of either metal or an insulator, and is made to have the same potential as the counter electrode 8.

A voltage was applied using a high frequency power source 8 in a gas atmosphere of 1 to 10 Torr in the reaction chamber to perform glow discharge decomposition.

A-81 was formed on the susceptor, the substrate mounted on the susceptor, the counter electrode 4, and the insulating band weight. Since the distance between the counter electrode 4 and the ribbon side was small, the amount deposited on the surface of the counter electrode 4 was small compared to the amount deposited on the ribbon side. In order to reduce the amount deposited on the counter electrode 4, it is necessary to place the insulating layer as close to the electrode 4 as possible.

When the a-8+ deposited on the ribbon exceeded a predetermined film thickness, the roll 22 was wound to supply a fresh surface insulation strip. The a-8i deposited by this winding is all rolled into the roll 22.
Caught inside. It is desirable that the width of the ribbon 20 in the roll length direction is larger than the width of the electrode 4, and by increasing the width by 5 cIn or more, the amount of a-8iO adhering to the counter electrode 4 could be reduced. After winding up with the roll 22, the reaction chamber was plasma etched using a gas such as CF4, thereby making it possible to clean the reaction chamber without exposing it to the outside air.

FIG. 6 shows a second embodiment, in which rows #21 and #22 are arranged on the opposite side of the counter electrode 40 with respect to the susceptor 3. This is constructed as shown using deflection rolls 23,24. With this configuration, it was possible to reduce the amount of a-8l adhering to the roll 21 where the clean band was wound, and it was possible to form an insulating band with less adhesion of a-8+ during winding by the roll 22. .

FIG. 7 shows a third embodiment, in which a susceptor 3 and a counter electrode 4 are configured as shown in the figure in a reaction chamber 1B, and an insulated take-up roll 22 is installed in an exhaust port 7 connected to an exhaust system. It is something. Therefore, even if the a-8+ film was slightly splashed due to winding, the inside of the reaction chamber 18 was not contaminated.

FIG. 8 shows a fourth embodiment, in which two direction changing rolls 2. Since a-8+ is peeled off a little each time it passes through L and 25, reduce the direction change roll and further roll 2.
4' and the take-up roll 22 are both installed in the exhaust lower. Also, regarding the roll 21 wrapped with a new insulating band, four bodies are covered with the cover 26, excluding the pull-out hole 27.
The cover 26 and the roll 21 were held at the same potential as the electrode 4. For this reason, the newly drawn insulation band 20
There is no longer any case that A-8i is attached to the surface.

In any of the above cases, the distance between the susceptor 3 and the counter electrode 4 is kept at a minimum, and each roll, etc. that has the same potential as the counter electrode 4 is kept at a sufficient distance from the susceptor or the chamber wall (the distance between the susceptor 3 and the counter electrode 40 is .5 times or more).

FIG. 9 shows a fifth embodiment, in which the wheels 1 for transporting the susceptor 3
7 exists, the relationship between the susceptor 3 and the counter electrode 4, as well as the rolls, etc., and the distances between the wheel 17 and the counter electrode 4, roll n, 24, etc.
The distance between the

In FIG. 10, a direction changing roll %29 is fixed to the counter electrode 4. In this case as well, it is desirable to configure the position of the roll gauge 29 so that the insulating band does not come into close contact with the counter electrode 4.

In the above embodiments, a polymer film is used for the ribbon 20, but the same effect could be obtained by using a conductive foil instead of the polymer film. However, in this case, it was necessary to keep the conductor parts such as the conductor foil and the roll supporting it insulated from the first electrode and the counter electrode.

〔Effect of the invention〕

The present invention covers the surface of the opposing electrode, which does not support the substrate, of the two electrodes for generating glow discharge in a plasma CVD apparatus, with a thin strip that is insulated from the electrode and passes near the electrode, and the thin strip is sent out. It emerges from the roll and is wound onto a take-up roll. This allows a
By depositing the reaction products such as -8i on the thin strip instead of the counter electrode and winding up the thin strip, the reaction products can be quickly removed without opening the reaction chamber, and the reaction chamber can be vented to the outside air. It is now possible to clean without exposing it. As a result, a-8! used especially for solar cells! The effects of the present invention are extremely significant, since the film can be formed stably, and the characteristics of solar cells and production yields can be improved, or the operating rate of plasma CVD equipment can be improved.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional plasma CVD apparatus, and Figure 2 (
a) I (b) shows the susceptor and heater part, (
a) is a plan view, (b) is a sectional view, FIG. 3 is a sectional view of another conventional plasma CVD apparatus, and FIG. 4 is an enlarged view of the main parts thereof,
FIG. 5 is a cross-sectional view of one embodiment of the present invention, and FIGS. 6 to 10 are different cross-sectional views of the actual and flow sides. 3... Susceptor counter electrode, 18... Reaction chamber,
Add...Thin strip, 21...Feeding roll, 22...
Take-up roll. Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1) In a device that decomposes a reactive gas by applying a voltage between a first electrode that also serves as a support for the substrate and a second electrode placed opposite to it to generate a glow discharge, the second electrode A ribbon delivery roll and a take-up roll comprising two rolls on both sides, each of which passes near the first electrode side of the second electrode and shields the second electrode in an electrically insulated state. Plasma CVD with
Device.