Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Reexamination Certificate
2001-05-10
2002-11-26
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
C438S764000, C438S778000, C118S7230AN, C118S7230ER
Reexamination Certificate
active
06486045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for forming functional deposited films and more particularly to an apparatus and method for forming functional deposited films which are suitably usable for preparing an amorphous silicon (hereinafter referred to as “a-Si”) photosensitive member for electrophotograph by using plasma CVD.
2. Related Background Art
There have been proposed amorphous materials such as, for example, amorphous silicon compensated with hydrogen or/and halogen as a device member for use in semiconductor devices, light-receiving members for electrophotograph, line sensors for image-input use, image pickup devices, photovoltaic devices, and other semiconductor devices represented by various electronic devices.
Some of these devices, however, have room for improvement in characteristics and production cost of their production. For example, in the production of light-receiving members for electrophotograph, since deposited films of a relatively large area are required to be formed, formation of such deposited films with uniformity in both thickness and electric characteristics and with less defects becomes difficult. Thus there have been demands for a method for forming deposited films for such use which ensures satisfactory productivity and yield.
The deposited films as described above can be formed by the plasma enhanced CVD process, that is, by decomposing a raw material gas with the aid of direct current or high-frequency microwave glow discharge to deposit a thin film on a substrate consisting of a material such as glass, quartz, heat-resistant synthetic resin film, stainless steel, or aluminum. And there have been proposed various apparatus which enable the formation of deposited films which satisfy the above demands.
The apparatus for forming deposited films as described above have, for example, a configuration shown in the schematic view of
FIGS. 1A and 1B
schematically.
FIG. 1A
is a schematic transverse sectional view of an apparatus for forming deposited films and
FIG. 1B
is a schematic longitudinal sectional view of an apparatus for forming deposited films.
The apparatus for forming deposited films shown in
FIGS. 1A and 1B
includes a reaction vessel
301
having a vacuum air-tight structure. Inside the reaction vessel
301
a plurality of cylindrical substrates
302
for forming deposited films are arranged in such a state that they are mounted on and held by respective substrate holders. Each of the substrate holders for holding the cylindrical substrates
302
can be rotated with a rotating shaft
310
driven by a rotating mechanism
311
consisting of a motor and a gear. Inside the rotating shaft
310
a heater is provided for adjusting the temperature of the cylindrical substrate
302
. Further, inside the reaction vessel
301
electrodes
304
for introducing high-frequency electric power and gas introducing pipes
308
for introducing a raw material gas are disposed. To the electrodes
304
a high-frequency power source
307
is connected via a matching unit
306
. Each of the gas introducing pipes
308
includes a plurality of openings for emitting gas uniformly and is connected to a raw material gas cylinder via a flow rate control portion (not shown in the figure). One end of an exhaust hole
309
is open to the reaction vessel
301
and the other end communicates with an exhauster (not shown in the figure).
The formation of deposited films by using the conventional apparatus for forming deposited films as described above is performed in the following procedure.
First, the cylindrical substrates
302
each mounted on a substrate holder are installed inside the reaction vessel
301
. Then, the reaction vessel
301
is exhausted with a vacuum pump (not shown in the figure) and its internal pressure is decreased to, for example, 10 Pa or less. Then, current is applied to the heater (not shown in the figure) arranged inside each substrate holder to heat each cylindrical substrate
302
to a temperature suitable for depositing films. Once the temperature of the substrates
302
reaches a desired value, a gas for forming a deposited film, such as silane gas, is introduced into the reaction vessel
301
through the gas introducing pipes
308
. At the same time, the high-frequency power source
307
is set at a desired electric power to generate high-frequency energy of, for example, 105 MHZ, and high-frequency electric power is introduced into the reaction vessel
301
through the high-frequency matching unit
306
, so as to allow glow discharge to occur. This discharge energy serves to decompose the raw material gas introduced into the reaction vessel
301
and form a desired deposited film on each substrate
302
. During the formation of deposited films, each rotating shaft
310
is rotated by rotating the rotating mechanism
311
to rotate each substrate
302
. Repeating the same operation a plurality of times allows the formation of light-receiving films having desired multilayer structure.
On the other hand, the manufacturing of a-Si photosensitive members (photosensitive members containing a hydrogen-based amorphous material at least in its photoconductive layer) requires advanced technology. Particularly in the photosensitive members for electrophotograph, they require films of larger area and thickness than those of other devices and accordingly, it is an important element how the uniformity of the films is ensured and how the film is formed at a higher deposition rate. From that viewpoint, there have been proposed various methods of manufacturing high quality a-Si photosensitive members in an industrially stable manner. For example, U.S. Pat. No. 6,145,469 (Japanese Patent Application Laid-Open No. 9-310181) discloses a technique of uniformly plasma-treating a substrate of a relatively large area while speeding up the treatment by constituting a part of a reaction vessel with a dielectric member and generating a plasma between a cathode electrode and its counter electrode which are placed interposing the dielectric vessel part therebetween to plasma-treat the substrate in the vessel.
In recent years, however, with increasing demands for electrophotographic apparatus which allow higher-quality images and speed-up, there have also been increasing demands for an apparatus for forming photosensitive members which meets the above demands and has high productivity. Thus the present inventors have concentrated their energy on investigating a method for forming high-quality deposited films at a higher deposition rate using high-frequency electric power with a frequency band of 50 to 450 MHZ. The film formation at this discharge frequency, however, gives rise to a problem such that plasma tends to be maldistributed, and thereby non-uniform treatment is likely to occur in film thickness and quality. This problem is serious particularly when treating a relatively large area, such as of a photosensitive member for electrophotograph. Furthermore, a problem arises such that plasma discharge is difficult to start and the disorder of plasma at the beginning of discharge can sometimes cause deterioration of the whole film and variation in film quality over the whole film.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and a method for forming a deposited film which allow the formation of a deposited film of a relatively large area at a treatment rate which could not be accomplished by the plasma process of the prior art and allow the stable production of the deposited film without creating variation in the quality.
Another object of the present invention is to provide an apparatus and a method for forming a deposited film, in which the deposited film is formed by providing a dielectric member between at least one high-frequency electrode and a plasma region and applying high-frequency electric power to plasma, whereby a more uniform deposited film can be formed.
Another object of the present invention is to provide an apparatus for forming a
Akiyama Kazuyoshi
Aoike Tatsuyuki
Hosoi Kazuto
Murayama Hitoshi
Otsuka Takashi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Gurley Lynne A.
Niebling John F.
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