JPS60190562A - Method and device for forming thin film - Google Patents

Abstract

PURPOSE:To grow a thin film at a high rate and to prevent damage to the thin film by subjecting gaseous raw materials to glow discharge decomposition in the presence of a magnetic field between electrodes for maintaining the electric discharge and disposing an intermediate electrode between said electrodes. CONSTITUTION:A high frequency is thrown between an electrode 21 for maintaining electric discharge and a base body 3 as a counter electrode from a high- frequency power source 8 to induce glow discharge and further many permanent magnets 6 are disposed to close the generated plasma by the magnetic field so as to increase density and to accelerate the growing rate of a thin film with a vessel 1 which is provided with a gas supply system 11 and a gas discharge system 15 and grows the thin film on the cylindrical base body 3 by the glow discharge decomposition of the gaseous raw materials maintained under prescribed pressure. An intermediate electrode 5 such as a meshed electrode or the like is provided between the above-mentioned electrode 21 for maintaining the discharge and the base body 3 and a variable DC voltage 7 is impressed thereto to relieve ion bombardment and the prevent the damage by the ion bombardment. The body 3 is preferably rotated in an arrow (a) direction and is moved relatively with the magnets 6 to make the thin film uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field Unpublished II relates to a thin film forming method and apparatus for forming a photoconductor layer made of, for example, amorphous silicon on the surface of a substrate by a glow discharge decomposition method.

Prior art and its problems Amorphous silicon (hereinafter referred to as a-
A photoconductor layer using Si (abbreviated as si) has been proposed (Japanese Patent Application Laid-open No. 78135/1983), and has recently attracted attention as an alternative to conventional selenium and CDS, and is being put into practical use.

This is because a-si is excellent in pollution-free properties, heat resistance, surface hardness, abrasion resistance, etc.

However, this plasma CVD method is
The disadvantage is that the growth rate is slow at about 5 people/second.

For example, when making an electrophotographic photoreceptor, the thickness of the A-SI film must be 15 to 20 gm5 degrees, and this 11! The time required to form a film up to J thickness is about 10 hours, and it is desired to improve the film formation speed.

To increase the rate of film formation, increase the reactant gas;
Alternatively, methods such as increasing the high frequency power; and further increasing the temperature of the substrate can be considered. However, although these methods increase the production rate, they have the drawback of affecting the hydride quality of the produced film.

Therefore, attempts have been made to perform glow discharge in the presence of a magnetic field and confine the generated plasma in the magnetic field to enhance the plasma capture effect, increase the density of the plasma, and increase the rate of thin film formation (Japanese Patent Laid-Open No. 1983-1992). -73428, JP 56-121629, JP 57-1610
No. 57, JP-A-58-132920, etc.).

However, this attempt focuses only on the plasma supplementation effect caused by the magnetic field, and does not take into account the damage caused by ion bombardment to the φ and V films produced.

For this reason, for example, an a-'si thin film photoreceptor has a drawback that a desired photocurrent cannot be changed.

II. Purpose of the Invention The present invention was made in view of the above-mentioned circumstances, and its main purpose is to provide a force D and an apparatus for growing a thin film at high speed while preventing damage to the thin film. .

Such objects are achieved by the invention described below.

That is, the first invention provides a method for forming a thin film on a substrate by injecting a high frequency between electrodes for sustaining discharge to decompose raw material gas by glow discharge.
An intermediate electrode is disposed between the discharge sustaining electrodes to reduce damage by ion bombardment of source gas ions, and the glow discharge is performed in the presence of a magnetic field≠
8 and 11XA formation method.

A second invention provides an apparatus for forming a thin film on a substrate by glow discharge decomposition of raw material gas by applying high frequency waves between the discharge sustaining electrodes, in which an intermediate electrode is disposed between the discharge sustaining electrodes. This is a thin film forming apparatus that reduces damage caused by ion bombardment of source gas ions, and that performs glow discharge in the presence of a magnetic field by installing a permanent magnet near one electrode of the glow discharge.

■Specific structure of the invention Hereinafter, the specific configuration of the present invention will be explained in detail.

1, 2 and 3 each show a different embodiment of the invention.

Tank 1 for glow discharge decomposition in Figures 1 and 3
has a cylindrical shape, and is connected to a gas exhaust system 15 and a gas supply system 11 so that a predetermined gas voltage can be set. In this case, the tank 1 does not necessarily have to be cylindrical, it may be rectangular, or it may take any other shape.

An electrode 21 is installed in the tank to form an electric field for generating and maintaining a glow discharge. In this case, as a counter electrode to the discharge holding electrode 21, as shown in FIG.
5, or one electrode may be provided as a base 3 as shown in FIGS. 1 and 3.

When one electrode is used as a base, gas efficiency is improved because source gas is prevented from adhering to unnecessary parts.

A substrate 3 on which a thin film is to be deposited is placed in the tank l.

In FIG. Further, as shown in FIG. 3, the base body may be a plurality of drum-shaped base bodies 3.

A heater 4 is arranged near the substrate 3 to maintain or heat the substrate at a predetermined temperature during film formation. The heater may be built into the discharge holding electrode 25 as shown in FIG. 2, or may be installed separately as shown in FIGS. 1 and 3. good.

Between the electrodes 21 and 25 for discharge holding (one of which is the base 3 in some cases), there is an intermediate electrode 5 for buffering ion street shock.
will be installed. This intermediate electrode 5 is a discharge holding electrode 21
．． 25.

This intermediate electrode 5 may have any structural shape, but is preferably formed into a mesh shape.

By making the DC voltage applied to the intermediate electrode 5 variable as shown in the figure, the glow discharge state determined by the device shape can be selected in accordance with the optimal conditions for desired film quality and growth rate. ↓In the vicinity of the base body 3, a large number or multi-pole magnetized permanent magnets 6 are installed, and the magnetic field formed by the permanent magnets 6 allows plasma to be efficiently and uniformly concentrated in a predetermined spatial area. Moreover, by selecting the voltage of the intermediate electrode 5, it is possible to set the voltage to the optimum state.

Note that although it is desirable that the magnetic field direction be orthogonal to the electrolytic field, it is not necessarily necessary that the magnetic field direction be orthogonal. The strength of the magnetic field is several 10 to several 100
It should be about G.

The base body 3 is installed so as to be movable relative to the permanent magnet 6.

In FIG. 1, the base 3 to the permanent magnet 6 rotate (rotate) in the circumferential direction (in the direction of arrow a in the figure).

In FIG. 2, one side is vibrated parallel to the base 3 (in the direction of the arrow in the figure). These may move the permanent magnet 6 or the base body 3.

In FIG. 3, the base drum 3 rotates on its own axis (in the direction of arrow °d in the figure) and revolves in the circumferential direction (in the direction of arrow C in the figure). The relative movement between the permanent magnets 6 and the substrate 3 makes the film formation uniform, allowing high-speed film formation with rough film quality.

Under this premise, the high frequency power source 8 applied to the discharge holding electrodes 21, 25, etc. during plasma decomposition is 400 KHz.
~30MHz, input power 100W-1000W
degree.

Further, the voltage applied to the intermediate electrode 6 is a DC potential, and -
The positive potential is about 300 to +300V, preferably 100V or less.

All known raw material gases used for forming the a-si layer can be used.

In addition, the operating pressure inside the reaction tank 1 is usually about 0.5 to 2 Torr, and according to the usual glow discharge decomposition method, the resonance vibration mile is about 100 W to several KW, and the frequency is 1 to 10 MHz.
It is sufficient to input a certain amount of power and perform glow discharge decomposition.

In this case, the substrate on which the A-SI layer is applied is 50 to 350°
It is preferable to maintain the temperature at about C.

In this way, the A-Si layer and the like are formed at a deposition rate of about 10 to 2000 people/m'in.

The thickness of the a-si layer is generally between 5 and 60 lm, especially between 10 and 3 m.
The distance should be approximately 0 lm.

Note that aluminum or the like is generally used as the material of the base.

Further, the a-si layer may be formed by laminating a plurality of layers having different impurity concentrations or many types of impurities.

The A-SI thin film produced as described above is directly used as a photosensitive layer or protective layer of an electrophotographic photoreceptor,
Used in ordinary copiers, laser printers, etc.

Indirectly, it is also used for solar cells, image sensor-1 imaging devices, and the like.

Further, the thin n-forming method of the present invention can also produce Si3N4M, amorphous DPIIQ, amorphous B501li, etc. by selecting the raw material gas.

■Specific effects of the invention According to the present invention, a permanent magnet is arranged on the substrate side on which a film is to be formed during glow discharge, and a mesh-like electrode for ion impact buffering is arranged independently of the discharge holding electrode, Since it utilizes the electron trapping effect of a magnetic field, there is no deterioration in the physical properties of the film, and the decomposition efficiency of reactive forces increases, making it possible to deposit a DA film even during low-input mode glow discharge, which normally does not cause film deposition. Become.

By making the voltage applied to this ion impact buffering mesh electrode variable, high-speed deposition of the a-Si thin film can be selectively performed under optimal conditions.

Furthermore, it is possible to shorten the preheating time of the base.

As described above, according to the present invention, it is possible to perform glow discharge in a low-power mode, reduce damage caused by ion bombardment during high-speed growth of an A-SI thin film, and obtain an electrophotographic photoreceptor with high photoconductivity. can.

The present invention group conducted various experiments in order to confirm the effects of the present invention.

An example is shown below.

Experimental Example 5 Glow group electrolysis was carried out in accordance with a conventional method using the apparatus shown in FIG. 1 using B2 as a source and a carrier.

That is, the operating pressure in the reactor was set to I Torr, and a power of 500 W and 13.56 MHz was applied to the resonant vibration coil.

A 30V DC power source was applied to the intermediate electrode.

A mesh-like electrode was used as the intermediate electrode, and was placed in the same rtB at a distance of 1.5 cm from the substrate, which is one electrode.

The strength of the magnetic field was 300G, and discharge was performed using the base as one electrode. Substrate temperature t±300'C! rotated in the circumferential direction.

When the SiH4 feed rate was 3505C:CM and the film was formed for 60 minutes, the film thickness was 17p.m.

On the other hand, in the method using only a magnetic field (without providing an intermediate electrode), the thickness of the formed film was 13 pm.

Further, in the conventional method in which neither a magnetic field nor an intermediate electrode is provided, the thickness of the 11A was 1-i 4 pm under the same conditions and for the same time as above.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are schematic diagrams for explaining the present invention in detail, respectively. 21.25...Discharge holding electrode 3...Base 5...Intermediate electrode 6...Permanent magnet Fig. 2 6

Claims (10)

[Claims] (1) When a high frequency is applied between the discharge sustaining electrodes to decompose the raw material gas by glow discharge to form a thin film on the substrate, an intermediate electrode is placed between the discharge sustaining electrodes to ionize the raw gas. Reduces damage from ion bombardment,
and a method for forming a thin film, characterized in that the glow discharge is performed in the presence of a magnetic field. (2) The thin film forming method according to claim 1, wherein the fijJ thin film is amorphous silicon. (3) The thin film forming method according to claim 1 or 2, wherein one of the discharge holding electrodes is the substrate. (4) The thin film forming method according to any one of claims 1 to 3, wherein the base body moves relative to the magnetic field. (5) The thin film forming method according to any one of claims 1 to 4, wherein the intermediate electrode is a mesh electrode. (6) In an apparatus in which a high frequency is applied between the discharge holding electrodes to decompose the raw material gas by glow discharge to form a thin film on the substrate, an intermediate electrode is placed between the discharge holding electrodes, and the raw material gas is decomposed by glow discharge. A thin film forming apparatus characterized by reducing damage caused by ion bombardment and performing the glow discharge in the presence of a magnetic field. (7) The thin film forming apparatus according to claim 6, wherein the thin film is amorphous silicon. (8) The thin film forming apparatus according to claim 6 or 7, wherein one of the discharge holding electrodes is the substrate. (9) The thin film forming apparatus according to any one of claims 6 to 8, wherein the magnetic field and the base body move relative to each other. (10) The thin film forming apparatus according to any one of claims 6 to 9, wherein the intermediate electrode is a mesh electrode.