JPH01185915A - Formation of thin film - Google Patents

Abstract

PURPOSE:To restrain an electron from being diffused to a cathode and an anode, to increase an electron density and to enhance a film-formation speed by a method wherein a magnetic field whose magnetic field intensity in the direction parallel to the cathode and the anode near the cathode and the anode becomes larger than the magnetic field intensity in the vertical direction is formed between the cathode and the anode. CONSTITUTION:A magnetic field whose magnetic field intensity in the direction parallel to a cathode 4 and an anode 5 near the cathode 4 and the anode 5 becomes larger than the magnetic field intensity in the vertical direction is formed between the cathode 4 and the anode 5. Accordingly, a small angle formed by the direction of the magnetic field and an electrode face is smaller than 45 deg. near both electrodes of the cathode 4 and the anode 5; the direction of the magnetic field near both electrodes becomes nearly parallel to both electrode faces. By this setup, it is possible to restrain an electron from being diffused to the anode and the cathode, to increase an electron density and to enhance a film-formation speed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to amorphous semiconductor thin films used in solar cells, thin film transistors, photoreceptors, etc., and crystalline semiconductors with a thickness of I! The present invention relates to a method for forming a thin film such as an insulator thin film or the like.

[Conventional technology]

Generally, a plasma CVD method using parallel plate glow discharge is known as a method for forming an amorphous semiconductor thin film, and for example, an apparatus as shown in FIG. 4 is used.

In FIG. 4, (1) is a reaction chamber, (2),
(3) represents the reaction gas supply port and exhaust port formed in the reaction chamber (1), (4) and (5) represent the reaction chamber (
1) A flat cathode and an anode arranged in parallel within the interior, (6) a semiconductor substrate for thin film formation attached to the anode (5), (7) a high frequency power supply, and a positive output terminal. It is grounded together with the anode (5), and its negative output terminal is connected to the cathode (4).

For example, when forming an amorphous silicon thin film,
The high frequency voltage from the power source (7) is applied to the cathode (4).

A reactive gas such as a silicon-containing silicone gas applied between the anodes (5) and supplied into the reaction chamber (1) is turned into plasma by glow discharge, and the plasmatized silicon is deposited on the semiconductor substrate (6). Then, an amorphous silicon thin film is epitaxially grown.

However, in the case of such plasma CVD method using glow discharge, there is a problem in terms of film formation speed, so for example, the Proceedings of the 34th Applied Physics Association Conference (1987
The magnetron discharge method, as described in "High Speed Deposition of A-8i Film by R29P-F-1 Magnetron Discharge Method" on page 246 (2011), p. 246, aims to improve the film deposition speed, improve throughput, and Efforts are being made to reduce costs.

By the way, this magnetron discharge method is a method in which a magnetic field is used in combination with the above-described plasma CVD method using glow discharge, and an apparatus shown in FIG. 5 is used. In FIG. 5, the same symbols as in FIG. 4 indicate the same or corresponding parts, and N and S in FIG. 5 indicate the magnetic poles of the magnet (8).

And, as shown in FIG. 5, the cathode (4).

A high-frequency voltage is applied by forming a magnetic field between the cathode (4) and the anode (5) through a magnet (8) such as an electromagnet or a permanent magnet placed on the opposite side of the anode (5). of electrons generated by glow discharge.

Diffusion in the direction perpendicular to the direction of the magnetic field can be suppressed, making it possible to improve the film formation rate.

Furthermore, in detail, since the electrons generated during glow discharge move in a cyclotron along the lines of magnetic force shown by the dashed-dotted line in FIG. 5, the diffusion of the electrons in the direction perpendicular to the direction of the magnetic field is suppressed. As a result, the diffusion of electrons to the anode (5) holding the substrate (6) and the side wall of the reaction chamber (1) is reduced, and a reduction in the electron density that turns the reaction gas into plasma is prevented. Compared to the plasma CVD method shown in the figure, the electron density in the plasma increases, and by confining the plasma locally using the formed magnetic field to increase the density of the frisma, the density of the film forming species increases. It is possible to increase the film formation rate, improve throughput, and reduce costs.

[Problem to be solved by the invention]

However, in the case of Fig. 5, the direction of the magnetic field near the cathode (4) is close to perpendicular to the surface of the cathode (4), so the diffusion of electrons to the cathode (4) cannot be suppressed, and the electrons There is a problem that there is a limit to increasing the density, and there is also a limit to increasing the film forming rate.

Therefore, an object of the present invention is to suppress the diffusion of electrons to the picture electrodes of the cathode and anode, increase the electron density, and further improve the film formation rate.

[Means to solve the problem]

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

That is, a cathode (4) and an anode (5) are arranged in parallel in a reaction chamber (1) to which a reaction gas is supplied, a thin film forming substrate (6) is attached to the anode (5), and the A high frequency power source (
In the thin film forming method according to 7), the reaction gas is turned into plasma by applying a high frequency voltage, and a thin film made of the reaction gas component turned into plasma is formed on the substrate (6), in the present invention, the cathode (4) , a magnetic field between the anodes (5) in which the magnetic field strength in the direction parallel to the cathode (4) and the anode (5) is greater than the magnetic field strength in the perpendicular direction in the vicinity of the cathode (4) and the anode (5), respectively. We are taking technical measures to form a

[For production]

Therefore, according to the present invention, a magnetic field in which the magnetic field strength in the direction parallel to the cathode (4) and the anode (5) in the vicinity of the cathode (4) and the anode (5) is larger than the magnetic field strength in the perpendicular direction, Since it is formed between the cathode (4) and the anode (5), the cathode (4) and the anode (
5) In the vicinity of each picture electrode, the small angle between the direction of the magnetic field and the electrode surface is smaller than 45° υ, and the direction of the magnetic field in the vicinity of each picture electrode is almost parallel to the picture electrode surface, which is different from the conventional method. As shown in the figure, diffusion of electrons not only to the anode (5) but also to the cathode (4) is suppressed, the electron density can be increased, and a further improvement in the film formation rate can be expected.

At this time, looking at the relationship between the direction of the magnetic field and the electron diffusion coefficient, the diffusion coefficient Dv in the direction perpendicular to the direction of the magnetic field is the diffusion coefficient Do when the magnetic field is zero.

If the elementary charge is e, the electron mass is m, the magnetic field strength is B, and the average collision time is τ, then Dv=Do/(1+(air)'').Here, ω is the cyclotron frequency.

ω=- and the mean free path of the electron! , where the velocity of the electron is V, it is expressed as τ=l/v.

On the other hand, the diffusion coefficient Dp in the direction parallel to the direction of the magnetic field is Dp = Do...■, so for example, B = 500 (Gauss),
Under the condition of r=10 (nsec, :], the above ■, ■
The equation is υDp/Dv; 10', and the electron diffusion coefficient in the direction parallel to the magnetic field is much larger than in the perpendicular direction. The more parallel you are, the more
The diffusion of electrons to the cathode (4) and anode (5) is further suppressed.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 to 3 showing embodiments thereof.

(Example 1) First, FIG. 1 and FIG. 2 showing Example 1 will be explained. Note that in FIG. 1, the same symbols as in FIG. 5 indicate the same or corresponding items.

As shown in FIG. 1, a plurality of energizing wires are placed approximately in the center between the cathode (4) and the anode (5) at predetermined intervals in parallel to the entire surface of the cathode (4) and the anode (5). (9), a current is passed through each wire (9) as shown by the X mark in the figure, and the cathode (4) is connected to the cathode (4).
, a magnetic field is formed between the anodes (5) as shown by the one-dot chain arrow in the figure.

At this time, as shown in Figure 2(a), if the magnetic field B is parallel to the anode (5), the electrons will be parallel to the anode (5) as shown by the dashed line in Figure 2(a). magnetic field B
K? Even with the cyclotron movement, the electrons reach the anode (5) and the number of electrons that diffuse to the anode (5) is extremely small.The same applies to the cathode (4).

On the other hand, as shown in Fig. 2('b), when the magnetic field B is not parallel to the anode (5), the magnetic field B is connected to the anode (5).
Dividing into a component Bp parallel to Bp and a component By perpendicular to Bp
By satisfying the condition of The same applies to the cathode (4).

Therefore, at least the cathode (4), the anode (5)
) The number and spacing of each wire (9) are set so that the magnetic field strength in the direction parallel to the cathode (4) and the anode (5) is greater than the magnetic field strength in the perpendicular direction in each vicinity. By doing so, it is possible to form a magnetic field almost parallel to the cathode (4) and anode (5).
Compared to the magnetron discharge method shown in the figure, the cathode (
4) and the diffusion of electrons to the anode (5) can be reduced.

Regarding the diffusion of electrons to the side wall of the reaction chamber (1) (hereinafter referred to as chamber wall), it is desirable that the magnetic field formed by each wire (9) be parallel to the chamber wall.
Due to the strong magnetic field B in the plasma existing region between the cathode (4) and anode (5) cross-hatched in Figure 2 (C), the diffusion of electrons to the chamber wall is suppressed. Therefore, the magnetic field strength near the chamber wall should be such that the magnetic field strength in the direction perpendicular to the chamber wall is smaller than 172, which is the maximum strength of the magnetic field B formed by each wire (9). good.

Thus, according to the embodiment, the cathode (4).

Between the anode (5), the cathode (4), the anode (5)
By energizing each wire (9) arranged parallel to A magnetic field that is stronger than the magnetic field strength in the direction is created between the cathode (4) and anode (5), suppressing the diffusion of electrons not only to the anode (5) as in the conventional case but also to the cathode (4). It is possible to increase the electron density, efficiently confine the plasma of the reactant gas and increase the density of the plasma, and increase the density of the film-forming species to further improve the film-forming speed compared to conventional methods. can do.

(Example 2) Next, FIG. 3 showing the second embodiment will be explained.

In Fig. 3, the same symbols as in Fig. 1 indicate the same or corresponding parts, and the difference from Fig. 1 is that the reaction chamber (
1) Two cathodes (4) are disposed close to each other in parallel approximately in the center of the reaction chamber (1).
Two anodes (5) are arranged in parallel to face each other, a substrate (6) is attached to both anodes (5), and a plurality of energizing wires 00 are arranged between both power swords (4). A current is passed through each wire αO as shown by the X mark in the same figure, and a magnetic field is formed around the double-force sword (4) as shown by the dashed-dotted line arrow in the same figure. This is the point. Note that αη in FIG. 3 is a holder for the double-handed sword (4).

At this time, the two-power sword (4) is formed to have a slightly smaller dimension than both the anodes (5).

Therefore, according to the above embodiment, by energizing each wire aO disposed between the double power swords (4), the double power swords (4) are energized.
4) Two anodes (5) A magnetic field in which the magnetic field strength in the direction parallel to the cathode (4) and the anode (5) is larger than the magnetic field strength in the perpendicular direction near each of the cathode (4) and the anode (5) between and the other cathode (
4), it can be formed between the anodes (5), and not only can the same effects as in Example 1 described above be obtained, but also thin films can be formed on two substrates (6) at the same time.

Note that the thin film formed on the substrate (6) is not limited to a semiconductor thin film, but may be an insulating thin film.

〔Effect of the invention〕

As described above, according to the thin film forming method of the present invention, a magnetic field in which the magnetic field intensity in the direction parallel to the cathode and the anode is larger than the magnetic field intensity in the perpendicular direction near the cathode and the anode, respectively, is applied to the cathode.

Since it is formed between the anodes, it is possible to suppress the diffusion of electrons not only to the anode but also to the cathode as in the past, increasing the electron density, and efficiently confining the plasma of the reaction gas. Figure out the densification of
By increasing the density of film-forming species, the film-forming speed can be further improved compared to the conventional method.

[Brief explanation of the drawing]

1 to 3 show examples of the thin film forming method of the present invention, FIG. 1 is a partially cutaway front view of Example 1, and FIG.
) to (C) are operation explanatory diagrams of FIG. 1, FIG. 3 is a partially cutaway front view of the second embodiment, and FIGS. 4 and 5 are a front view and partially cutaway front view of the conventional example, respectively. . (1)...Reaction chamber, (4)...Cathode, (
5)... Anode, (6)... Substrate, (7)...
High frequency power supply.

Claims (1)

[Claims] (1) A cathode and an anode are arranged in parallel in a reaction chamber supplied with a reaction gas, a thin film forming substrate is attached to the anode, and a high frequency voltage from a high frequency power source is applied to the cathode and anode to remove the reaction gas. In the thin film forming method of forming a thin film on the substrate made of the reactive gas component which has been turned into plasma, the cathode is placed between the cathode and the anode and in the vicinity of each of the cathode and the anode;
A method for forming a thin film, characterized in that a magnetic field is formed in which the magnetic field strength in the direction parallel to the anode is greater than the magnetic field strength in the perpendicular direction.