JPS63187619A - Plasma cvd system - Google Patents

Abstract

PURPOSE:To supply uniform gas flow to all over the surface of an electrode and to form a homogeneous thin film, by providing one of the counter electrodes with a plate having gas inlet holes and with a gas distributing plate in which gas distribution holes are formed such that smaller gas flow is formed in the central region and larger gas flow is formed in the peripheral region. CONSTITUTION:Plane-parallel-plate-type electrodes 2 and 3 are opposed to each other so that a thin film is formed by using glow discharge. One of the electrodes, the electrode 3 for example is provided with a plate 9 having gas inlet holes and with a gas distributing plate 11 in which gas distribution holes 12, 12' are formed such that smaller gas flow is formed in the central region and larger one in the peripheral region thereof. The gas distribution holes 12, 12' may be provided at a lower density in the central region and at a higher density in the peripheral region. Alternatively, the gas distributions holes smaller in size are provided in the central region and larger holes are provided in the peripheral region at an equal density in both of the regions. In this manner, uniform gas flow can be supplied to all over the surface of the electrode and a homogeneous thin film can be formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasma CVD apparatus that forms a thin film using glow discharge, and in particular to improvement of the electrode shape in order to obtain a film with a homogeneous and uniform thickness. Regarding.

[Conventional technology]

In semiconductor technology, the chemical vapor deposition method is used to form thin films such as silicon oxide, silicon nitride, and polycrystalline silicon.
cal vapor deposition (hereinafter abbreviated as CVD method) is often used. Among the CVD methods, the plasma CVD method, in which the energy required for the CVD reaction is obtained using glow discharge plasma, has the advantage that film growth occurs at a low temperature of about 300°C and the film is strong, so it is particularly suitable for semiconductor thin films. It is very useful for forming.

This device usually has a structure as shown in FIGS. 3 and 4. That is, in the figure, 1 is the reaction chamber, 2 is the substrate side electrode (
33 is a high frequency electrode (cathode), 4 is a heater for heating the substrate, 5 is a substrate to which a thin film is deposited, 6 is a high frequency power source, 7.37 is a gas inlet, 8.38 is a gas exhaust port It is.

Inside the reaction chamber 1, parallel plate electrodes 2 and 3. Alternatively, 2 and 33 may be placed opposite each other, and a high frequency power source 6 may be used between the opposing electrodes.
A high-frequency electric field is applied to generate a glow discharge. A reactive gas is introduced between the electrodes, activated by discharge plasma, and a thin film is formed on the surface of the substrate 5 placed on the substrate side electrode 2 heated by the substrate heating heater 4 due to the plasma reaction. 0 Here, in the case of the one shown in FIG. 3, a gas inlet 37 is provided at one place on the side of the reaction chamber 1, and a gas exhaust port 38 is provided on the opposite side. The reactant gas introduced therein is activated by plasma while flowing between the opposing electrodes 2 and 33 to form a film on the substrate, and the remaining gas is exhausted from the exhaust port 38. Therefore, a gas concentration distribution occurs in the gas flow direction, and the gas concentration in a portion near the gas inlet 37 between the opposing electrodes is higher than in the other portions. In general, the growth rate and characteristics of the film formed on the substrate 5 change depending on the amount of gas and the 4A degree, and in this case, the quality of the film (the film is thicker on the gas inlet 37 side) is not uniform.

The one in FIG. 4 is intended to improve this point, and a gas introduction lower is provided inside the cathode side electrode 3.

A large number of gas introduction holes 1 are provided on the anode-side surface of the electrode 3 facing the electrode 2.
A plate 9 with gas introduction holes in which the numbers 0 are evenly arranged, and a gas distribution plate 41 in which gas distribution holes 42 having the same size and a small number of holes as the gas introduction holes are evenly provided therebelow. Deploy. FIG. 4(b) shows a plan view of the gas dispersion plate 41, and the gas dispersion holes 42 are uniform in size and arrangement on the surface of the plate 410.

A gas dispersion plate 41 having dispersion holes of this shape. A reactive gas is introduced between the opposing electrodes through the plate 9 with gas introduction holes, activated, and a thin film is grown on the substrate.

The remaining reaction gas is exhausted from the gas exhaust port 8 below the cathode side electrode 3.

According to this structure, it is possible to introduce the reaction gas from the center of one electrode in the reaction chamber 1 while dispersing it over the entire electrode surface. A homogeneous film can be formed on the substrate 5.

[Problem that the invention seeks to solve]

・However, although this structure improves the uniformity of the film compared to the structure shown in FIG. 3, the reaction gas is more concentrated near the center of the gas dispersion plate 41 near the gas introduction lower than in the periphery. When the flow rate is large, there is a problem in that the thin film formed on the substrate 5 becomes thicker in the center.

Therefore, in the present invention, the gas concentration distribution between the opposing electrodes in the reaction chamber is made uniform in the plasma CVD apparatus.

The present invention provides a plasma CVD apparatus capable of forming a thin film of uniform quality and thickness on a substrate.

[Means and effects for solving the problems] In the present invention, the cathode side electrode is placed under the plate with gas introduction holes. The arrangement density of the gas distribution holes in the gas distribution plate that disperses the gas flow rate is υ, where the center of the distribution plate is coarse and the peripheral area is dense.
The spacing of the gas distribution holes makes the density even and its size smaller in the center.

It is configured to have a large peripheral area, or a configuration that is a mixture of these.

With this configuration, the flow rate of the reaction gas introduced between the opposing electrodes is uniform over the entire electrode surface, and therefore the quality and thickness of the thin film formed on the substrate are also uniform.

〔Example〕

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

In FIG. 1, 1 is a reaction chamber, 2 is an anode electrode on the substrate side, 3 is a high frequency cathode side electrode, 4 is a heater for heating the substrate,
5 is a substrate, 6 is a high frequency power source, 7 is a gas inlet, 8 is a gas exhaust port, 9 is a plate with gas inlet holes, and 11 is a gas dispersion plate.

The basic structure inside the reaction chamber 1 is the same as the conventional example shown in Figure 3.
Its operation is the same as that in 2 reaction chambers 1, for example, silane (S
A reaction gas consisting of iH4) is introduced from the gas introduction lower,
Plasma is generated by applying a high frequency voltage of 13.degree. 56 MHz from a high frequency power source 6 between a parallel plate type substrate side electrode 2 and a cathode side electrode 3. The reactive gas is decomposed and reacted in this plasma to form an amorphous silicon film, which is a semiconductor film, on the surface of the substrate 5. At this time, during the film forming process, excess reaction gas is exhausted from the exhaust port 8, and the substrate 5 is heated to 150 to 350°C by the heater 4. Here, the gas introduction lower is formed inside the high frequency electrode 3 on the cando side, and the cathode A large number of gas introduction holes 10 are arranged at equal intervals on the plate 9 with gas introduction holes on the side electrode 3 facing the substrate side electrode 2, and below the gas introduction holes 10, gas is introduced from the gas introduction lower. A gas distribution plate 11 provided with a large number of gas distribution holes 12 and 12' is disposed so that the gas is evenly distributed over the surface of the electrode 3.

In this embodiment, the arrangement density of the gas dispersion holes provided in the gas dispersion plate 11 is made coarser near the center to prevent gas from passing through, and denser at the periphery of the plate 1 to allow gas to easily pass through. be. As a result, the gas introduction holes 10 of the plate 9 with gas introduction holes
The flow rate of the reaction gas introduced into the reaction chamber 1 can be adjusted to a nearly uniform amount. FIG. 1(b) is a plan view of the gas dispersion plate 11 of this embodiment, in which the number of dispersion holes 12 at the center thereof is smaller than the number of dispersion holes 12' at the periphery. Therefore, the flow rate of the reaction gas introduced from the gas introduction lower is uniformly introduced into the reaction chamber 1 through the gas introduction hole when passing through the gas distribution plate 11, without being concentrated only in the center.

Here, the gas introduction hole plate 9 acts as an electrode during discharge and directly affects the discharge state, so if the shape of this electrode becomes uneven, the discharge will also become unbalanced! It is necessary to make the shape of the poles uniform. Therefore, the gas introduction holes 10 are arranged evenly and the condition of the holes 12 in the gas distribution plate 11 below them is changed to make the gas flow rate uniform.

Another embodiment of the present invention will be explained with reference to FIG.

In FIG. 2, the sizes of the holes formed in the gas dispersion plate 11 are shown in different sizes. It is also possible to make the gas flow uniform by forming a small hole 22-1 in the center near the gas introduction lower and sequentially forming larger holes 22-2 and 22-3 in the surrounding area. Instead of sequentially forming larger holes, larger holes may be formed only in the peripheral portion.

Of course, in the present invention, the number of holes may be made non-uniform between the center and the periphery, and the size of the pores may also be made non-uniform between the center and the periphery. It can be applied not only to the production of , but also to the formation of any thin film as long as it is formed by the plasma CVD method.

[Effects of the Invention] According to the present invention, the gas flow rate introduced into the reaction chamber 1 through the gas introduction hole can be adjusted to a nearly uniform amount, and the gas flow rate can be adjusted to be nearly uniform over a larger area on the surface of the opposing substrate 5 than before. A film with good thickness and quality could be obtained.

[Brief explanation of the drawing]

1 and 2 are detailed explanatory diagrams of the present invention. FIGS. 3 and 4 are explanatory diagrams of conventional examples. 1...Reaction chamber. 2... Substrate side electrode (anode). 3...High frequency electrode (cathode). 4... Heater for heating the substrate. 5... Board. 6...High frequency power supply. 7...Gas inlet. 8...Gas exhaust port. 9...Plate with gas introduction holes. 10...Gas introduction hole. 11...Gas dispersion plate. 12, 12'... Gas distribution hole. 22-1 to 22-3...Gas distribution holes.

Claims (3)

[Claims] (1) In a plasma CVD apparatus that is equipped with parallel plate-type counter electrodes and forms thin films using glow discharge, one electrode is equipped with a plate with gas introduction holes, and the gas flow is small in the center and small in the periphery. Plasma CVD characterized by disposing a gas dispersion plate in which large gas dispersion holes are formed.
Device. (2) The plasma CVD apparatus according to claim 1, wherein the gas dispersion plate is provided with gas dispersion holes such that the density of gas dispersion holes is higher in the peripheral portion than in the central portion. (3) The plasma CVD apparatus according to claim 1, wherein the gas dispersion plate is formed so that the size of the gas dispersion holes is smaller in the center portion and larger in the peripheral portion.