JPS61295374A - Formation apparatus for accumulated film by glow discharge decomposition method - Google Patents

Abstract

PURPOSE:To form stably an accumulated film which is uniform and homogeneous by providing a coaxial cylindrical anodic electrode between a cylindrical cathodic electrode and a coaxial cylindrical base material and separating a reaction chamber into a plasma discharge space and a film formation space. CONSTITUTION:A coaxial cylindrical anode electrode 11 is provided between a cylindrical base body 6 and a cathodic electrode 3. When impressing the high frequency voltage between the cathodic electrode 3 and the anodic electrode 11, the plasma discharge is caused in a plasma discharge space C between both electrodes 3, 11. The introduced gaseous silane is decomposed in the plasma discharge space C to produce an ionic particle and a neutral radical particle or the like. Among the produced ionoic particles, a negative ionic particle is flown to the anodic electrode 11 side and a positive ionic particle is flown to the cathodic electrode 3 side. The negative ionic particle and electron are caught on the anodic electrode 11 and only the neutral particle is introduced into a film formation space D through a drawing-out port 11a. The introduced particle flows toward and exhaust port 9 and a semiconductor film is accumulated on the surface of a base material 6.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to a film deposited on a substrate, particularly a functional film, particularly a semiconductor device, a photosensitive device for electrophotography, a line sensor for image input, an imaging device, and a photosensitive device. The present invention relates to an apparatus for forming an amorphous semiconductor film used in power devices and the like.

[Description of prior art]

Conventionally, semiconductor devices, photosensitive devices for electrophotography,
For example, amorphous silicon (hereinafter referred to as RA-8iJ), hydrogenated amorphous silicon (hereinafter referred to as Deposited films of amorphous semiconductors such as ra-3i (referred to as HJ) have been proposed, and some of them have been put into practical use. And, these deposited films are
It is known that it is formed by the glow discharge decomposition method, that is, a method in which raw material gas is decomposed by direct current or high-frequency glow discharge to form a thin deposited film on a substrate such as glass, quartz, or stainless steel. Various devices have also been proposed.

As an example of a conventional apparatus for forming a deposited film using the glow discharge decomposition method, there is a known apparatus for forming a deposited film, as shown in FIG. 2, which can efficiently form a deposited film on a cylindrical substrate.

FIG. 2 is a schematic cross-sectional view showing an example of a conventional apparatus for forming a deposited film on a cylindrical substrate.

In the figure, 1 is a cylindrical reaction vessel, which is sealed by a soil wall 1 surrounding wall and a bottom wall to form a reaction chamber, and a coaxial cylindrical base 6 is installed inside. Insulating rings 2a and 2b are disposed at the upper and lower ends of the peripheral wall of the reaction vessel 1, and a double-walled cathode electrode 3 is provided between the upper and lower insulating rings 2a and 2b. That is, among the walls that have a double wall structure.

The outer wall 6a is connected to an electrically grounded high frequency power source 4 via a conductive wire. The inner wall 3b is electrically connected to the outer wall 3a, and a plurality of gas discharge ports 6C for blowing out raw material gas into the reaction vessel 1 are provided on the wall surface. Reference numeral 5 denotes a raw material gas supply pipe, which is provided to penetrate the outer wall 6a of the cathode electrode 3, one end of which opens into the space A formed by the outer wall 3a and the inner wall 3b, and the other end of which is connected to the raw material gas supply source. (not shown). The cylindrical base 6 is made of metal such as aluminum, and is electrically grounded to serve as an anode electrode.
A high frequency voltage is applied between the cathode electrode 5 and the cylindrical substrate (anode electrode) 6 to generate plasma discharge. A heater 7 is built into the cylindrical substrate 6 to heat the substrate 6 to an optimum temperature for forming a deposited film. 8 is a motor for rotating the cylindrical support. Reference numeral 9 denotes an exhaust port provided on the bottom wall of the reaction vessel 1, and a valve means 10 is provided to evacuate the inside of the reaction vessel 1.
It is connected to an exhaust system (not shown) via an exhaust pipe equipped with an exhaust pipe.

An amorphous semiconductor film is deposited on the surface of a cylindrical substrate B using the above-described deposited film forming apparatus as follows.

That is, a part of the gas inside the reaction vessel 1 is evacuated from the exhaust port 9 by an exhaust device (not shown), and the cylindrical substrate 6 is
is heated to and maintained at 200 to 300°C by heater 7,
The motor 8 is driven and rotated. Next, a source gas such as silane gas is introduced into the space A from the source gas supply pipe 5, for example, in the case of forming an amorphous silicon deposited film. The raw material gas introduced into the space A passes through a large number of gas discharge ports 3C provided on the wall surface of the inner wall 3b of the cathode electrode, and passes through the reaction chamber surrounded by the inner cathode wall 3b and the cylindrical substrate (anode electrode) 6. It is released into space B.

Next, one frequency 13.56M) (z high frequency voltage is
When an electric current is applied to the cathode electrode 3, electrons are emitted from the inner wall 3b of the cathode electrode toward the cylindrical substrate (anode electrode) B. The emitted electrons collide with molecules such as silane gas, decompose the gas molecules, and generate ion particles, neutral radical particles, and the like. These electrons are on the surface of the cylindrical substrate 6.

Although ion particles and neutral radical particles fly in, it is mainly the neutral radical particles that contribute to the deposition of the amorphous semiconductor film. , or as a result of a complex reaction between neutral radical particles and the substrate surface, the substrate 6
It is considered that a deposited film is formed thereon. On the other hand, electrons and ion particles collide with the deposited film during or after formation, which can increase the density of structural defects that are undesirable for amorphous semiconductor films, such as dumping bonds, voids, and SiH2 bonds. It's clear.

In other words, in the conventional apparatus for forming a deposited film using the glow discharge decomposition method, the structure is such that the substrate installed inside is directly exposed to a plasma atmosphere, so there is no risk of degrading the various properties of the deposited film that is formed. Many, high quality, uniform and homogeneous.

It is difficult to efficiently and always stably obtain a deposited film having excellent desired properties.

In addition, although there are factors that influence the formation of the deposited film, such as source gas concentration, gas pressure, gas flow rate, input power, etc., in the conventional apparatus, the thickness distribution of the deposited film formed on the surface of the base 6 is In order to make it uniform, the distribution of the raw material gas discharge ports 6C was adjusted. However, in the gas decomposition process, the plasma intensity distribution depends on the cathode shape, potential drop, and
Or the cathode electrode 3 and the cylindrical substrate (anode electrode)
Since the film thickness distribution is strongly affected by the spacing between the gas discharge ports 5C and the like, it is difficult to make the film thickness distribution uniform by adjusting only the distribution of the gas discharge ports 5C.

Furthermore, the cathode electrode material is sputtered by positive ion particles generated by the plasma and flies onto the surface of the cylindrical substrate 6, which causes it to be mixed into the deposited film as impurities, which causes deterioration of various properties of the deposited film. There is also the problem of becoming one.

[Purpose of the invention]

The present invention overcomes the problems in conventional devices as described above, and provides semiconductor devices, photosensitive devices for electrophotography, line sensors for image input, imaging devices, photovoltaic devices, various other electronic devices, optical devices, etc. It is an object of the present invention to provide an apparatus capable of regularly and stably forming a deposited film as an element member used in a device using a glow discharge decomposition method.

That is, one main object of the present invention is to provide a glow discharge that can eliminate damage to a deposited film caused by plasma bombardment, make it uniform and homogeneous, and constantly and stably form a deposited film of good quality and excellent desired characteristics. An object of the present invention is to provide an apparatus for forming a deposited film using a decomposition method.

Another object of the present invention is to provide a glow that can easily control the thickness and quality of the deposited film to be formed, and can form a deposited film with a uniform thickness distribution and uniform quality. An object of the present invention is to provide an apparatus for forming a deposited film using a discharge decomposition method.

[Structure of the invention]

The present invention provides an apparatus for forming a deposited film using a glow discharge decomposition method that can achieve the above-mentioned objects.

In order to overcome the above-mentioned problems in the conventional apparatus, the present inventor continued intensive research and found that in order to prevent the substrate from being directly exposed to the plasma atmosphere, it was found that We obtained the knowledge that it is sufficient to separate the plasma discharge space and the film formation space. After further research.

By installing a coaxial cylindrical anode electrode between the cylindrical cathode electrode 3 and the coaxial cylindrical substrate 6, one reaction chamber is separated into a plasma discharge space and a film forming space, and the cylindrical anode electrode is connected to the plasma discharge It has been found that in addition to the function as a counter electrode for plasma generation, it is sufficient to have a function as a plasma shielding plate to prevent the base 6 from being directly exposed to a plasma atmosphere.

The apparatus of the present invention was completed based on this knowledge, and includes a cylindrical reaction vessel equipped with a reaction chamber surrounded and sealed by an upper wall, a side wall, and a lower wall, and a raw material gas introduced into the reaction chamber. and a means for evacuating the inside of the reaction chamber.
In an apparatus for forming a deposited film by a glow discharge decomposition method on a coaxial cylindrical substrate placed in a reaction vessel, a cylindrical cathode electrode also serves as a side wall of the reaction vessel.

A cylindrical anode electrode is coaxially arranged inside the cylindrical cathode electrode, and the cylindrical base body is coaxially arranged inside the anode electrode. The cylindrical cathode electrode and the cylindrical anode electrode are kept at a distance that allows glow discharge to occur, thereby forming a plasma discharge space, and the wall surface of the cylindrical anode electrode contains ion particles and electrons generated by glow discharge decomposition. It is characterized by having a plurality of openings shaped to block passage of the gas and selectively allow only neutral radical particles and undecomposed reaction gas to pass through.

The coaxial cylindrical anode electrode in the device of the present invention has a function as a shielding plate to prevent the cylindrical substrate from being bombarded by electrons and ion particles as described above.
It also has the function of a shielding plate that prevents electrode material ejected by sputtering of positive ion particles in plasma from reaching the surface of the cylindrical substrate. Furthermore, by adjusting the shape 6 distribution of the neutral radical particle outlet opened in the cylindrical anode electrode, it is possible to adjust the concentration distribution of neutral radical particles that contribute to film deposition, and the resulting deposit In addition to being able to control the film thickness distribution, it is not susceptible to changes in neutral radical particle concentration due to changes in plasma intensity distribution, unlike conventional devices.

As a result, a deposited film with uniform film quality and uniform thickness distribution can be formed with good reproducibility.

DETAILED DESCRIPTION OF THE INVENTION The apparatus for forming a deposited film by the glow discharge decomposition method having the above-mentioned structure of the present invention will be explained in more detail with reference to the embodiments of the drawings, but the present invention is not limited thereto. 1st
The figure is a schematic cross-sectional view of an apparatus according to one preferred embodiment of the present invention.

In the figure, the same symbols as in FIG. 2 are used for parts having the same functions as those of the conventional device described above. That is, 1 is a reaction vessel, 2a and 2b are insulating rings.

3 is a cathode electrode, 3a is its outer wall, 3b is its inner wall, 3c is a gas discharge port provided in 3b, 4 is a high frequency power source, 5 is a raw material gas supply pipe, 6 is a coaxial cylindrical base, 7 is a heater , 8 is a motor, 9 is an exhaust port, and 10 is a valve. 11 is similarly electrically grounded. When high frequency power is applied between the cathode electrode 5 and the coaxial anode electrode 11, plasma discharge is generated in the space C formed between the cathode electrode inner wall 3b and the anode electrode 11. The anode electrode 11 has plasma discharge,
It functions as a plasma shielding plate to prevent leakage into the film forming space formed between the anode electrode 11 and the cylindrical substrate B, and also directs neutral particles generated in the plasma discharge space C into the film forming space. An anode is preferred so that it can be introduced into the By providing the anode electrode 11 between the cylindrical substrate 6 and the cathode electrode inner wall 3b, electrons and negative ion particles generated in the plasma discharge space C are captured by the anode electrode 11.

It becomes possible to introduce only neutral particles such as neutral radical particles and undecomposed gas into the film forming space.

Note that since the anode electrode 11 and the cylindrical substrate 6 are electrically grounded and maintained at the same potential, the structure is such that no plasma discharge occurs between them.

A deposited film is formed using the above-described apparatus of the present invention as follows.

For example, when manufacturing an amorphous silicon (hereinafter referred to as RA-8iJ) semiconductor film as a photosensitive device for electrophotography, an aluminum drum is used as a cylindrical substrate, and a silane gas such as SiH4, Si2H6, etc. is used as a raw material gas, or Use halogenated silane gas, etc.

These raw material gases may be used alone or in combination of two or more, and may be diluted with an inert gas such as He or Ar. Furthermore, a-8i
For this purpose, the deposited film can be doped with n-type impurities, p-type impurities, and other atoms.

Raw material gases capable of supplying n-type impurity atoms, p-type impurity atoms, and other atoms can be used alone or in combination with the aforementioned raw material gases.

First, the pulp 10 is opened and the gas inside the reaction vessel is evacuated through the exhaust port 9 using a vacuum exhaust device (not shown) to reduce the pressure inside the reaction vessel to preferably 5 x 1Q-'To.
rr or less, preferably from the 1× tube 5 into the interior A of the cathode electrode 6 having a cylindrical double wall structure. The source gas is discharged into the plasma discharge space C from a gas discharge port 3C opened in the inner wall 3b of the cathode electrode. Adjust the valve 11 so that the pressure inside the reaction vessel when the gas is introduced is preferably 1 x 10-2 to 100 Torr, more preferably 1 x 10''-2 to 1 Torr. The aluminum drum is heated to 30 to 450°C, preferably 200 to 300°C, by the heater 7, and the motor 8 is driven to rotate it.

At this point, the cathode electrode 3 and the anode electrode 11
When a high frequency voltage is applied from the high frequency power supply 4 between the cathode electrode 3 and the anode electrode 11, a plasma discharge is generated in the plasma discharge space C between the cathode electrode 3 and the anode electrode 11. Plasma discharge space C
Then, the introduced silane gas is decomposed and ionic particles, neutral radical particles, etc. are generated. Here, anode electrode 1
1 is grounded and has a positive potential, whereas the cathode electrode 5 has a negative potential, and the negative ion particles and electrons among the generated ion particles go to the anode electrode 11 side. Positive ion particles fly toward the cathode electrode 3 side. Negative ion particles and electrons are captured by the anode electrode 11, and only neutral particles such as neutral radical particles and undecomposed gas are introduced into the film forming space through the neutral particle outlet 11a.

The neutral radical particles introduced into the film forming space flow toward the exhaust port 9 along the surface of the aluminum drum heated by the heater 7, and deposit an A-8I semiconductor film on the surface of the aluminum substrate 6. . Neutral radical particles and undecomposed gases that did not contribute to the deposition are removed from the deposition film forming apparatus by an exhaust device (not shown) through exhaust ports 9 provided at the upper and lower ends of the cylindrical substrate B in the central axis direction. is exhausted.

[Summary of effects of the invention]

In the device of the present invention, a coaxial cylindrical anode electrode having a neutral radical particle extraction port is provided between a cylindrical cathode electrode and a coaxial cylindrical base inside the cathode electrode, so that the coaxial cylindrical anode electrode can discharge plasma. In addition to serving as a counter electrode for plasma generation, the film being deposited on the cylindrical substrate also functions as a plasma shielding plate to prevent the cylindrical substrate from being directly exposed to plasma. It is possible to efficiently and stably obtain a deposited film that is not damaged by the impact of negative ion particles, has an extremely low density of structural defects, and has good desired properties.

Further, in the device of the present invention, the cylindrical anode electrode serves as a shielding plate that prevents electrode material ejected by positive ion particles in the plasma from sputtering on the cylindrical cathode electrode surface from reaching the cylindrical substrate surface. Therefore, it is possible to prevent the cathode electrode material from being mixed into the deposited film, acting as an impurity, and deteriorating the semiconductor properties.

Furthermore, the device of the present invention can adjust the concentration distribution of neutral radical particles contributing to the formation of a deposited film by adjusting the shape and distribution of the neutral radical particle outlet provided in the cylindrical anode electrode. It is something. Therefore, it is possible to reproducibly produce a deposited film with uniform thickness and quality distribution without being affected by changes in neutral radical particle concentration due to changes in plasma intensity distribution, unlike in the case of conventional deposition film forming equipment using the glow discharge method. It can be formed easily and efficiently.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a conventional apparatus for forming a deposited film using a glow discharge method.

Claims (7)

[Claims] (1) In an apparatus for forming a deposited film using a glow discharge decomposition method, a cylindrical anode electrode is arranged coaxially inside a cylindrical cathode electrode that also serves as a reaction vessel, and a deposited film is placed inside the cylindrical anode electrode. A deposited film forming apparatus characterized in that cylindrical substrates for forming a deposited film are arranged coaxially. (2) What is a cylindrical cathode electrode and a cylindrical anode electrode?
The deposited film forming apparatus according to claim 1, wherein the deposited film forming apparatus is electrically isolated by an insulating material. (3) A cylindrical cathode electrode and a cylindrical anode electrode,
The apparatus for forming a deposited film according to claim 1, wherein a plasma discharge space is formed by maintaining an interval at which a glow discharge can occur. (4) Multiple opening holes in the wall of the cylindrical anode electrode are shaped to block the passage of ion particles and electrons generated by glow discharge decomposition, and selectively allow only neutral radical particles and undecomposed reaction gas to pass through. An apparatus for forming a deposited film according to claim (1), characterized in that the apparatus comprises: (5) Claim (1) characterized in that exhaust ports for evacuating the inside of the reaction vessel are arranged at the upper and lower ends of the central axis of the space formed by the cylindrical anode electrode and the cylindrical base. An apparatus for forming a deposited film as described in the item. (6) Item (1) of the claim, characterized in that the cylindrical substrate is made of a metal such as aluminum and is electrically grounded so that it is maintained at the same potential as the cylindrical anode electrode. An apparatus for forming the deposited film described above. (7) Claim (1) characterized in that a heating means for heating the cylindrical base is disposed inside the cylindrical base.
) The deposited film forming apparatus described in the item.