JPS58193361A - Plasma chemical vapor deposition apparatus - Google Patents

Abstract

PURPOSE:To form an amorphous thin film with good quality within a short time, by a method wherein electrodes forming plural plasma discharge fields due to glow discharge are provided in a reduced pressure space and a stock material gas is supplied to these plasma discharge fields. CONSTITUTION:A plasma CVD apparatus is constituted from a reduced pressure chamber 2 having a reduced pressure space 1 formed to the interior thereof, a common electrode 3 having gas permeability arranged in said container 2, a first electrode 4 arranged to a part opposed to one surface of the common electrode 3 and forming a first plasma discharge field 11 in the space with the common electrode 3, a second electrode 5 arranged to a part opposed to the other surface of the common electrode 3 and forming a second plasma discharge field 12 in the space with the common electrode 3, a substrate 13 arranged to the side of the first electrode 4 so as to oppose the film forming surface 13a thereof to the first plasma discharge field 11 and a gas supply line 16 for supplying a stock material gas to the second plasma discharge field 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable, for example, to the production of solar cells etc. by producing amorphous silicon film II (hereinafter referred to as "a-8i film") on the surface of a substrate. Conventionally, in this type of plasma CVD, 101 types or several types of raw material gases are continuously introduced into a reduced pressure space.
This raw material gas is passed through a plasma discharge field formed in the reduced pressure space to undergo plasma decomposition, and the decomposed gas is guided to the film formation surface of the heated substrate to form an amorphous thin film. There is something I did. However, conventionally, after passing the raw material gas through a single plasma discharge field,
Since the film is immediately directed to the film-forming surface of the substrate, there is a problem in that it is difficult to form a high-quality amorphous thin film on a relatively large substrate in a short time. As an apparatus, the one shown in Fig. 1 or Fig. 2 is known. Electrodes c and d are placed opposite each other to form a plasma discharge field C in the lower half b+, and a film forming surface is placed in the plasma discharge field e in the first half b! of the reduced pressure vessel. A substrate f facing each other, a heat receiving plate g attached to the back surface i of the substrate f,
A heating plate that heats the substrate f via this heat receiving plate g is used. The raw material gas introduced into the vacuum vessel from the lower end of the vacuum vessel can be guided to the film-forming surface of the substrate through the plasma discharge field e. However, with such a configuration, when the reduced pressure vessel is increased in size, the distance between the electrodes C%d8 increases accordingly, making it difficult to perform uniform discharge. Therefore, there is a problem that it cannot cope with an increase in the size of the substrate. -10, The device shown in Fig. 2 has a pair of electrodes C' and d' disposed in a reduced pressure vessel i/)j3 in a manner substantially parallel to each other to form a plasma discharge field 6/. Then, a heating plate h' is placed on the -10,000 electrode CI side.
A substrate fl heated by +z is disposed, and the other electrode d7 is made of a type having air permeability. Then, the raw material gas i' introduced into the reduced pressure vessel b' is passed through the electrode dI and guided into the plasma discharge field C', and the plasma-decomposed scum is passed through the plasma discharge field e'. It is polished so as to be supplied in the film forming direction of the substrate fI. With such a configuration, it is possible to enlarge the plasma discharge field e' by increasing the size of both electrodes, so that it is possible to cope with the increase in the size of the substrate E. However, in order to ensure a uniform discharge state in each part, the distance between the picture electrodes llIC/1d/ cannot be made too thick.

Therefore, there is a certain limit to increasing the thickness of the plasma discharge field e'. Therefore, it is difficult to ensure a sufficient distance for the source gas to pass through the plasma discharge field 61, and gas that is insufficiently plasma decomposed tends to be supplied to the substrate. As a result, there are problems in that the amount of impurities contained in the produced film increases and that it takes a long time to produce the film. As described above, conventional apparatuses, regardless of their type, have certain disadvantages, and at the same time, there is a need to be able to produce a high-quality amorphous thin film on a relatively large substrate in a short time. I can't satisfy you.

Therefore, with conventional equipment, there is a problem in that it is difficult to efficiently produce large quantities of products such as amorphous 11-inch solar cells.

The present invention was made with attention to such circumstances, and
By providing electrodes to form multiple plasma discharge fields by echo-glow discharge within a reduced-pressure space and supplying raw material gas to these plasma discharge fields, it is possible to The purpose of the present invention is to provide a plasma CVD apparatus capable of producing a high-quality amorphous thin film in a short period of time on a substrate or the like.

An embodiment of the present invention will be described below with reference to FIG.

! @8 Figure is a schematic cross-sectional view of a plasma CVD apparatus according to the present invention. This device is provided with a reduced pressure container 2 that forms a reduced pressure space 1 therein, and a common electrode 8 having air permeability in the form of a net or comb is disposed approximately horizontally at a middle position within the reduced pressure container 2. Further, a 1 liter electrode 4 is provided at a portion opposite to the upper surface of the common electrode 8 in the decompression vessel 2, and a second electrode 5 is provided at a portion opposite to the lower surface of the common electrode 8. There is. Then, when the common electrode 8 is connected to the high frequency power source 6, the first and second electrodes 4.5 are connected to a predetermined direct current. [7.8 tons are connected,
The space between the first electrode 4 and the common electrode 8 forms a first plasma discharge field 11, and the space between the second electrode 5 and the common electrode 8 forms a second plasma discharge field. 1
2 is formed. The first electrode 4 is made of a good heat conductive material and serves as a heat receiving plate, and a substrate 18 is attached below the electrode 4 (iH).The substrate 18 and the electrode 4 are connected to a holder 14. The electrode 4 is held substantially parallel to the common electrode 3 by a heating plate 1 for heating the substrate 13 via the electrode 4.
5 are arranged. - The second electrode 5 is in the form of a perforated plate having a large number of small holes 6a, and is arranged so that the raw material gas G can pass through the electrode 5.

A gas supply line 16 is connected to the lower end of the decompression vessel 2, and an exhaust line 18 including a vacuum pump 17 is connected to the 1c1JH end.

Next, the operation of the plasma CVD apparatus according to the present invention will be explained.

First, operate the vacuum pop 17 to reduce the inside of the vacuum container 2.
After reducing the pressure to below Q Torr, adjust the inflow and outflow valves for the raw material gas into the decompression vessel 2 from iζ to l T
While maintaining the internal and external pressures and the necessary gas flow rate, electricity is supplied to the heater in the heating plate 15 to heat the substrate 13 set on the lower surface of the first electrode 4. Also, a predetermined voltage is applied to each electrode 8.4.5tζ, and the common l! A glow discharge is generated between the pole 3 and between the second electrode 5 and the common electrode 3, and the adjacent first plasma discharge field 11 and the first plasma discharge field 2 plasma discharge fields 12 are formed.

This soft part connects the gas supply line 16 to the inside of the reduced pressure vessel 2.
, monolan (8iL(4), etc.) When the raw material containing soot G is sequentially supplied, the soot G from this raw material flows into the small hole 5 of the second electrode 5.
The second plasma discharge field 12+ flows in through a, and then passes through the common electrode 8 and is introduced into the first plasma discharge field 11+. However, this raw material is
When sequentially passing through each of the plasma discharge fields 12.11,
This is plasma decomposed, and the decomposed gas is successively supplied to the film-forming surface 13a of the heated substrate 13, thereby producing an amorphous thin film such as the film-forming surface 18a+Co-Si film. Then, the gas that is no longer needed is passed through the exhaust system line 18. 1. The bell is discharged outside.

In this way, the desired amorphous film dr+13a+isy of the substrate 13 can be produced.
However, since the plasma CVD apparatus according to the present invention is designed to cause a glow discharge between the opposing surfaces of the electrodes and form a plasma discharge field 11.12, the discharge does not occur. No inconvenience caused by uniformity 1
This plasma family [1ulL12] can be expanded. That is, if the area of each electrode is increased in accordance with the enlargement of the substrate 18, the large size of the Eζ substrate 13 can be dealt with without the above inconvenience. Moreover, in the multistage plasma discharge field arrangement, the raw material gas G is guided through each of these plasma discharge fields 11.12+c sequentially, so it is possible to plasma decompose 0 of the gas in 1 minute. , it becomes possible to produce a high-quality amorphous thin film with few impurities in a short time.

In addition, two plasma discharge fields 11.12 are sandwiched between the common electrode 8, which has air permeability, and the raw material gas G is supplied to each of these plasma discharge fields 11.12. Plasma CVD can be performed easily and reliably using a minimum number of components. Furthermore, when the electrode 8.4.5 and the substrate 18 are combined as in the present device, the discharge area can be limited to the effective range, so power can be saved. It is possible to reduce the
By comparison, the device can be made smaller.

In addition, in the case of this device, the distance between the electrodes (i.e., the distance between the common electrode 3 and the first Wli 4, the distance between the common electrode 8 and the second electrode 5),
(or both of the If it is set smaller than the size, it is also possible to prevent invalid (or harmful) discharge in the power introduction section 1.

f, cJ-, s, this Qmei 1 series plasma cvp device 1
In this case, each plasma discharge field is formed not only from a plate-shaped WCa+ which is a continuous component, but also from an aggregate of unit ft poles divided into a plurality of parts. There may be.

It goes without saying that the present invention is not limited to the first embodiment; for example, modifications such as those shown in FIGS. 4, 5, and 6 may be considered. Figure 4 ja), (b),
(C) shows the common electrode and the first . This figure shows a modification related to the second 110 connection. In the figure, 21 is a power supply that connects a high frequency power source and a DC power source. In addition, FIG. 5 shows a curved common electrode 3' having a common center of curvature, the first . Second electrode 4/, 5/ and substrate 18
'i). Furthermore, FIG. 6 shows several sets of common electrodes 3II... in a common vacuum container.
The first and second electrodes 4, 5''... and the substrate 13''...
. . . is arranged in a golden ring shape, and in the figure 22 . . .
is a heater for heating each of the substrates 13I'. In this case, the first rD electrodes 4'... and the substrate 13
″... are placed inside the common electrode 3″..., and the second
Place 1 outside of # energizing th3''... on mrei 5"...1 & L, but leave. In the above example,
Although the second electrode is also made to have air permeability and the raw material gas is transmitted through the second electrode and guided to the 1@2 plasma discharge field, the present invention does not necessarily require such a configuration. Of course, it is not limited to
For example, the second electrode may be made of a non-permeable material, or the material gas may be supplied from the side to the second plasma discharge field.Furthermore, the substrate may be made of an insulating material. Alternatively, it may be made of a conductive material.

Since the present invention has the above-described configuration, the present invention is a plasma CVD method that can generate a high-quality amorphous thin film in a short time on a relatively large substrate or a plurality of substrates arranged over a relatively wide area. equipment can be provided.

[Brief explanation of drawings]

1 and 2 are schematic sectional views showing a conventional example. 8th
The figure is a schematic sectional view showing one embodiment of the present invention. 4(a), (b), and (e) are circuit diagrams showing other embodiments of the present invention, FIG. 5 is a partial sectional view showing another embodiment of the present invention, and FIG. 6 is a circuit diagram showing other embodiments of the present invention. FIG. 7 is a schematic cross-sectional plan view showing still another embodiment of the present invention. 1... Decompression space 2... Decompression container 8.8', a''
-, common electrode 4.4', 4'-'pl electrode 5
．． 5', 8''-1, 2 (Dllll pole 11-...First plasma discharge field 12...Second plasma discharge field 13...Substrate 18&...Film forming agent Patent attorney Akazawa- Hiroshi 1

Claims (1)

[Claims] a decompression vessel forming an internal decompression space; a common electrode with air permeability disposed within the decompression vessel; a first t-pole forming a first plasma discharge field between the electrodes and a portion opposite to the other surface of the common electrode in the reduced pressure vessel; a second electrode forming the second plasma discharge field; a substrate disposed on the first electrode side with its film-forming surface facing the first plasma discharge field;
A plasma CVD device (1) characterized in that it is equipped with a gas supply line for supplying raw material gas to a plasma discharge field of