JPS6140771Y2 - - Google Patents

Description

[Detailed description of the invention] The invention can be applied, for example, to the production of solar cells etc. by forming an amorphous silicon film (hereinafter referred to as "a-Si film") on the surface of a substrate. The present invention relates to plasma CVD equipment.

Conventionally, this type of plasma CVD apparatus includes a reduced pressure vessel in which a plasma discharge field is provided, a substrate placed in the reduced pressure vessel with the film forming surface facing the plasma discharge field, and a source gas that is connected to the plasma. Some devices include a gas supply line for supplying gas to the substrate via a discharge field. That is, in this device, raw material gas is continuously introduced into the reduced pressure container from the gas supply system, the gas is caused to plasma decompose by passing through the plasma discharge field, and the decomposed gas is heated. is guided to the film-forming surface of the substrate, and an amorphous thin film is produced on this film-forming surface.

However, with just this, it is not possible to set the distribution of gas flow rate and flow velocity distribution to each part of the film-forming surface of the substrate, so it is necessary to generate a homogeneous amorphous thin film on a particularly large substrate. The disadvantage is that it is difficult to

One way to deal with this inconvenience is to arrange a flow regulator made of porous material before the plasma discharge field, and introduce the raw material gas to the plasma discharge field after passing through the flow regulator. It will be done. However, a fluid regulating device made of a porous material has problems in that it is difficult to control the distribution, and it is difficult to clean the inside even if clogging occurs due to reaction products and the like during use.

The present invention was developed by focusing on these circumstances, and by making the flow regulator disposed in the front stage of the plasma discharge field consist of a large number of balls gathered together in a lump, the above-mentioned problem can be achieved. An object of the present invention is to provide a plasma CVD apparatus that can eliminate inconveniences.

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

A reduced pressure container 2 is provided which forms a reduced pressure space 1 therein, and a common electrode 3 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 first electrode 4 is provided at a portion facing the upper surface of the common electrode 3 in the decompression container 2, and a second electrode 5 is provided at a portion facing the lower surface of the common electrode 3. . Then, the common electrode 3 is connected to, for example, a high frequency power source 6, and the first and second electrodes 4 and 5 are connected to predetermined DC power sources 7 and 8, respectively, so that the first electrode 4 and the A first plasma discharge field 11 is formed between the common electrode 3 and a second plasma discharge field 1 is formed between the second electrode 5 and the common electrode 3.
2 is formed. The first electrode 4 is made of a good heat conductive material and also serves as a heat receiving plate, and a substrate 13 is attached to the lower surface of the electrode 4. And this board 1
3 and the electrode 4 are held substantially parallel to the common electrode 3 by a holder 14. Further, a heating plate 15 for heating the substrate 13 via the electrode 4 is disposed near the upper side of the electrode 4 . On the other hand, the second electrode 5 has a net or comb shape similar to the common electrode 3. A rectifier 16 is disposed below the second electrode 5. The flow regulator 16 is made up of a large number of balls 19 gathered together in a mass between two holding plates 17 and 18 made of a net or a perforated plate. The raw material gas G can flow through the gap between the two. A gas supply line 21 is connected to the lower end of the decompression vessel 2, and an exhaust line 23 including a vacuum pump 22 is connected to the upper end.

Next, the operation of this device will be explained.

First, the vacuum pump 22 is operated and the reduced pressure container 2 is
After reducing the pressure inside to about 10 ^-3 Torr or less, the raw material gas is introduced into the decompression vessel 2 by adjusting the inflow and outflow valves.
While maintaining the internal and external pressure of 1 Torr and the necessary gas flow rate, the heater in the heating plate 15 is energized to heat the substrate 13 set on the lower surface of the first electrode 4. Further, by applying a predetermined voltage to each electrode 3, 4, and 5, a glow discharge is generated between the first electrode 4 and the common electrode 3 and between the second electrode 5 and the common electrode 3. A first plasma discharge field 11 and a second plasma discharge field 12 which are adjacent to each other above and below through the common electrode 3 are formed. In this state, when a raw material gas G such as monosilane (SiH ₄ ) is sequentially supplied from the gas supply line 21 into the decompression vessel 2, this raw material gas G passes through the rectifier 16 and the second electrode 5 to the It flows into the second plasma discharge field 12 and then passes through the common electrode 3 and is introduced into the first plasma discharge field 11. As a result, this source gas G is plasma decomposed as it sequentially passes through each of the plasma discharge fields 12 and 11, and the decomposed gas is sequentially supplied to the film forming surface 13a of the heated substrate 13. is applied to the film forming surface 13a.
-Amorphous thin films such as Si films are produced. Then, the gas that is no longer needed is discharged to the outside of the decompression vessel 2 through the exhaust system path 23.

In this way, a desired amorphous thin film can be formed on the film-forming surface 13a of the substrate 13. In this apparatus, the plasma discharge fields 11, 12
A rectifier 16 is provided at the front stage of the rectifier 16, and the raw material gas G passed through the rectifier 16 is guided to the plasma discharge field 12, so that the flow rate of the gas supplied to each part of the film-forming surface 13a of the substrate 13, etc. can be controlled to a desired value, and a homogeneous amorphous thin film can be produced on the film-forming surface 13a. Furthermore, since the flow regulator 16 is made up of a large number of balls 19..., the ventilation resistance of each part can be freely changed depending on how the balls 19... are piled up. Therefore, there is an advantage that the gas flow rate can be made uniform and the distribution can be adjusted very easily. Moreover, if the balls 19 become clogged with reaction products after being used for a certain period of time, all you have to do is take them apart and wash them.
Unlike fluid regulators made of porous materials that are difficult to clean internally, there is no uneconomical need to replace them every time a blockage occurs.

Note that the configuration of the flow regulator is of course not limited to that of the illustrated embodiment. For example, when the flow regulator is arranged horizontally as in the illustrated embodiment, the retaining plate on the upper surface side may be omitted. Good too. Further, the ball may be made of a conductive material so that the rectifying fluid itself also functions as an electrode.

Further, in the above embodiment, the case where the plasma discharge field is formed in two stages has been described, but it goes without saying that the present invention can also be applied to an apparatus having only a single plasma discharge field. Note that when the plasma discharge field is provided in multiple stages, the raw material gas can be sufficiently plasma decomposed, so there is an advantage that a high-quality amorphous thin film can be produced in a short time.

Furthermore, although not shown, there is also a modified embodiment in which two levers that can be operated from outside the decompression vessel are provided to sandwich the upper and lower surfaces of the regulating fluid, and the distance between the two levers is adjusted to adjust the gas distribution conditions. Conceivable.

As explained above, in the present invention, a rectifier made of a large number of balls gathered in a lump is provided in the front stage of the plasma discharge field, so that it can be supplied to the film-forming surface of the substrate by a simple adjustment operation. By making the gas uniform, it is possible to generate a homogeneous amorphous thin film on the film-forming surface of a relatively large substrate or multiple substrates arranged over a relatively wide area. It is possible to provide a plasma CVD apparatus that can easily and economically deal with clogging.

[Brief explanation of the drawing]

The drawing is a schematic sectional view showing an embodiment of the present invention. 2...Reduced pressure container, 3, 4, 5... Electrode, 11,
12... Plasma discharge field, 13... Substrate, 13a
. . . Film forming surface, 16 . . . Fluid regulator, 17, 18 .

Claims (1)

[Scope of utility model registration request] A reduced-pressure container with a plasma discharge field provided therein, a substrate disposed in the reduced-pressure container with its film-forming surface facing one end of the plasma discharge field, and a large number of balls assembled in a lump form the plasma. A plasma characterized by comprising a flow regulator provided at the other end of the discharge field, and a gas supply line for supplying raw material gas to the plasma discharge field through the flow regulator.
CVD equipment.