JPH01243413A - Thin film forming equipment - Google Patents

Abstract

PURPOSE:To prevent the deterioration of interface characteristics, and improve element characteristics, by installing, in the vicinity of a grid, a shutter whose potential is kept equal to the grid, and which is maintained in a closed state until glow discharge is stabilized, and turned into an open state after the glow discharge has been stabilized. CONSTITUTION:A grid 8 is arranged between a cathode 2 and an anode 3, and grounded. A shutter 10, which is arranged in the vicinity of the grid 8 and grounded, is provided with a plurality of thin metal plate 11 of continuous length in a rectangular direction to each wire 9. The shutter 10 is closed; high frequency voltage is applied between the cathode 2 and the grid 8 by a power supply 6; RF glow discharge is generated between the cathode 2 and the grid 8. After the discharge is stabilized, the shutter is opened, and a thin film is formed on the substrate 4. Thereby high energy particles are prevented from colliding against the substrate 4, so that the deterioration of film quality can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides plasma C by radio frequency (RF) glow discharge.
The present invention relates to a thin film forming apparatus that forms a thin film such as a semiconductor thin film on a substrate by a VD method.

[Conventional technology]

In general, a plasma CVD method using RF glow discharge is known as a method for forming thin films such as amorphous silicon thin films.This method generates RF glow discharge between a cathode and an anode arranged in a reaction chamber, This RF
A glow discharge generates plasma of a reactive gas, and a thin film is formed on a thin film forming substrate mounted and held on an anode.

However, in this case, high-energy particles such as electrons and ions generated by discharge during film formation collide with the substrate and the thin film on the substrate, causing a disadvantage in that the quality of the thin film formed on the substrate deteriorates. .

Conventionally, the Third Symposium on Plasma
Processing, 1981, “Analysis of
Silan Glow Discharge Bimas Nubectroscopy J (Third Symposium
Plasma Processing, 1981
, [ANALYSIS 0FSILANE OL
□'tlV DISCI(AI[E BY MASS
SPP；CT'RO8COPY J (Herl)e
A mesh-like grid is provided between the cathode and the anode as reported in rt A, Weakliem). Collisions of high-energy particles during film formation are suppressed by employing the so-called triode method.

By the way, an apparatus used in such a triode-type forced glow discharge plasma CVD method is configured as shown in FIG. 2).

(31 is a flat cathode and anode arranged in parallel to the reaction chamber (11), (41 is a thin film forming substrate attached to the anode (3), (5) is between the cathode 12+ and the anode C31) (6) is a high-frequency power source that applies high-frequency voltage between the cathode (2) and the grid (5) to generate a glow discharge; (7) is a direct current to the anode (3); This is a bias power supply that applies a bias voltage.

When forming a thin film using the apparatus shown in FIG.
A high frequency voltage is applied between the power supply (6), the cathode C2), and the grid (5), and a glow discharge is generated.
, the reaction gas is defsumed and film-forming radicals are generated, and a thin film is formed by the film-forming radicals on the substrate (4).A bias voltage is applied to the anode (31) by the bias power supply (7), and the earth potential is grid r5)
Therefore, high-energy particles such as electrons and ions generated by the F glow discharge are relaxed, and collision of high-energy particles with the thin film formed on the substrate (41 or substrate +41) is suppressed.

[Problem to be solved by the invention]

However, at the beginning of the RF glow discharge, there are a large number of high-energy particles, and these high-energy particles also include neutral particles, so simply providing the grid r51 as described above will not work. , it is not possible to sufficiently suppress the collision of high-density, high-energy particles including neutral particles on the substrate (41) immediately after the discharge occurs, thereby preventing deterioration of the film quality of the thin film formed on the substrate (4). The problem is that it cannot be done.

Furthermore, when creating a device with a layered structure, the impact of high-energy particles immediately after the RF glow discharge occurs during the formation of each layer affects the underlying layer, for example, Technical Digest Op First International
Photovoltaic Science and Engineering Conference, +984, pp. 719-72
2 (Technical Digestof is
International Photovol
taic 5science and F; ngi-
Neering Conference, 1984
, p. 719-722].
This causes deterioration of the interfacial characteristics of each layer, causing deterioration of device characteristics.

Therefore, the present invention has been made with the above-mentioned points in mind. When forming a thin film by a triode type F glow discharge plasma CVD method, a substrate or a substrate of high energy particles containing neutral particles immediately after generation of RF glow discharge. The purpose is to prevent collisions with the grown thin film above and to prevent deterioration of the quality of the resulting thin film.

[Failure to solve the problem]

Next, means for achieving the above object will be explained using FIG. 1 which corresponds to an embodiment.

That is, in the present invention, a reaction chamber (
1), a flat cathode (2) and an anode (3) arranged in parallel to the reaction chamber (1), and a thin film forming substrate (41) attached to the anode (3).
a grid r81 disposed between the cathode (2) and the anno-toy 31; and a high frequency power supply r61 that applies a high frequency voltage between the cathode (2) and the grid 181 to generate glow discharge. ,
a bias power source c which applies a bias voltage to the anode (3); and a bias power source C provided near the grid (8) at the same potential as the grid (8) and maintained in a closed state until the glow discharge is stabilized; A technical measure is taken to include a shutter aO that is opened after the glow discharge is stabilized.

[Effect]

Therefore, according to the present invention, until the R I/glow discharge generated between the cathode (2) and the grid (8) is stabilized, the shutter 00 is held in the closed state.
Immediately after the start of the F glow discharge, high-energy particles including neutral particles are prevented from colliding with the substrate (4), and the quality of the thin film grown on the substrate (4) is prevented from deteriorating.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 to 4 showing an embodiment thereof.

In FIG. 1 showing the overall configuration, the same symbols as in FIG. 5 indicate the same or equivalent parts, and in FIG.
8) is a grid formed by arranging a plurality of wires (9) at equal intervals (2 MM), and is disposed between the cathode (21) and the anode (31) and is grounded.

Furthermore, the shutter is a grounded shutter provided near the bottom of the grid (8), and each wire (a thin metal plate O1 long in the direction perpendicular to the direction of 91) (width 1.5 am)
is formed by arranging a plurality of
).

As shown in (b), each metal plate 0 is sequentially arranged to shield between the cathode C21 and the anode R31, and in the open state, as shown in 3(2)(A) and (b), The metal plates til+, which are divided into several groups, are superposed one by one, and the cathode C2) and anode (3) are opened.

At this time, the opening and closing of the shutter α0 is performed by an external operation. For example, each set of operating wires is engaged with each metal plate 011, and each operating wire is connected from outside the reaction chamber (1) manually or mechanically. By pulling the
The metal plate 0υ of each group is moved, and Nyatsuta αG is opened.
It is set to be closed.

When forming a thin film on the substrate (4), the shutter flG is first closed, and the power source (61) is connected to the cathode (
A high frequency voltage is applied between the cathode (2I) and the grid +81 to generate an RF glow discharge between the cathode (2I) and the grid +81.
a).

The cathode (2) is held in the closed state as shown in (b);
7 nodes (shielding between 31 nodes.

Next, after the time from the occurrence of the RF glow discharge until the discharge becomes stable, the shutter a1 is opened as shown in Fig. 3(a).
, as shown in (b), the film formation radicals generated by the RF glow discharge can reach the substrate (41), and a thin film is formed on the substrate (4).

In this way, by keeping the shutter aO closed until the RF glow discharge stabilizes, high-energy particles including neutral particles are prevented from colliding with the substrate (4). ) Deterioration of the film quality of the thin film grown on the film is prevented.

By the way, using the above-mentioned apparatus, the reaction conditions shown in the table below were prepared using Ni.
Created an n-structured amorphous silicon fat pond,
The collection efficiency of the obtained solar cell was measured, and the results were as shown by the solid line in FIG.

However, in this case, a glass substrate with a transparent conductive oxide film formed on its upper surface is used as the substrate (4), and an aluminum vapor-deposited film is used as the back electrode.

As described above, when forming each of the p, i, and n layers, the shutter (11) is closed until the RF glow discharge stabilizes, and then the shutter 00 is opened after stabilization.

For comparison, the collection efficiency of an amorphous silicon solar cell produced using the conventional apparatus shown in FIG. 5 was also measured under the same reaction conditions as described above, and this is shown by the broken line in FIG. 4.

In this way, as is clear from FIG. 4, the solar cell produced by the apparatus of the embodiment of the present invention shown in FIG.
300 to 60 compared to solar cells made using conventional equipment.
The collection efficiency on the short wavelength side of 0 nm is increased,
An improvement in short-wavelength sensitivity was observed, and this is due to the fact that the damage to the underlying p-layer during the i-layer formation can be reduced compared to conventional equipment due to the provision of a shutter function. As a result, the deterioration of the film quality of one layer could not be prevented.

Therefore, according to the embodiment, the shutter aO is kept closed until the F glow discharge is stabilized, and the RF
By opening the shutters all after the glow discharge has stabilized, the shutter aO can prevent high-energy particles including neutral particles from colliding with the substrate (4) immediately after the start of the discharge. When creating photovoltaic elements with a laminated structure such as amorphous thin film solar cells, it is possible to prevent deterioration of the film quality of the thin film that grows.
It becomes possible to prevent deterioration of the interface characteristics of each layer and improve the device characteristics.

Further, in the embodiment, the shutter (10) is formed of a conductive material, and the shutter (00) is formed of a grid (8).
By placing them close to each other and at the same potential, it is possible to prevent disturbances in the discharge, and it is possible to obtain stable RF glow discharge as before, maintaining the same reproducibility, yield, and uniformity as before. be able to.

It goes without saying that the configurations of the grid C8) and the shutter I'1G are not limited to those described above.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

Immediately after the start of 1'LF glow discharge, high-energy particles including neutral particles can be prevented from colliding with the substrate, making it possible to prevent the deterioration of the film quality of the thin film grown on the substrate. Compared to conventional methods, when creating photovoltaic elements with a stacked structure such as crystalline thin-film solar cells,
It becomes possible to prevent deterioration of the interface characteristics of each layer and improve the device characteristics, and the effect is extremely large.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the thin film forming apparatus of the present invention, FIG. 1 is a front view, FIGS. 2(a) and 2(h) are a bottom view and a front view of the shutter in the closed state, Figure 3 (
EL), (b) is a bottom view and a front view of the shutter in an open state, FIG. 4 is a collection efficiency characteristic diagram, and FIG. 5 is a front view of a conventional example. +11...Reaction chamber, C2)...Cathode, C3)・
... Anode, (4) ... Substrate, (6) ... High frequency power supply, (7) ... Bias power supply, C81 ... Grid, aO ... Shutter.

Claims (1)

[Claims] (1) A reaction chamber to which a reaction gas is supplied, a flat cathode and an anode arranged in parallel to the reaction chamber, a thin film forming substrate attached to the anode, and a connection between the cathode and the anode. a high-frequency power source that applies a high-frequency voltage between the cathode and the grid to generate glow discharge; a bias power source that applies a bias voltage to the anode; a grid disposed in the vicinity of the grid; set at the same potential,
A thin film forming apparatus comprising: a shutter that is held in a closed state until the glow discharge is stabilized, and is opened after the glow discharge is stabilized.