Deposited film forming apparatus

Details Deposited film forming apparatus Deposited film forming apparatus

2002-01-16

2004-03-09

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

With treating means

C118S7230AN

Reexamination Certificate

active

06702898

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deposited film forming apparatus (a plasma CVD apparatus etc.) and a deposited film forming method for forming a deposited film, particularly a functional deposited film (for example, an amorphous semiconductor used for semiconductor devices, electrophotographic photosensitive members, photovoltaic devices, and so on) or the like, on a substrate.
2. Related Background Art
Suggested as device materials used for the semiconductor devices, electrophotographic photosensitive members, photovoltaic devices, and various other electronic devices are non-monocrystalline deposited films such as amorphous silicon, for example, typified by amorphous silicon compensated by hydrogen or/and halogen (for example, fluorine, chlorine, etc.) (which will hereinafter be abbreviated as “a-Si:H,X”), or crystalline deposited films such as thin films of diamond, and some of them are used in practice. These deposited films are formed, for example, by the plasma CVD method, i.e., by a method for decomposing a source gas by a glow discharge induced by direct current, high-frequency wave, or microwave and forming a deposited film on such a substrate as glass, quartz, a heat-resistant synthetic resin film, stainless steel, or aluminum, and a variety of devices for carrying out the method are also suggested.
An example of such a forming apparatus and forming method of deposited film is one briefly described below.
FIG.
1
A and
FIG. 1B
are schematic structural diagrams to show an example of an apparatus for producing an electrophotographic photosensitive member by the high-frequency plasma CVD method. The structure of the production apparatus illustrated in
FIGS. 1A and 1B
is as follows.
This apparatus is generally composed of a deposition system
1100
, a source gas supply system
1200
, and an exhaust system (not illustrated) for reducing the pressure inside a reaction vessel
1111
. Inside the reaction vessel
1111
in the deposition system
1100
there are cylindrical substrates
1112
, heaters
1114
for heating the respective substrates, source gas inlet pipes
1115
, and a cathode electrode
1116
, and a high-frequency power supply
1117
and a high-frequency matching box
1118
are connected to the cathode electrode
1116
.
The source gas supply system
1200
has cylinders
1221
to
1226
for supplying respective source gases of SiH
4
, GeH
4
, H
2
, CH
4
, B
2
H
6
, PH
3
, etc., valves
1231
to
1236
, and mass flow controllers
1211
to
1216
, and the cylinder of each source gas is connected via an auxiliary valve
1260
to the gas inlet pipes
1115
in the reaction vessel
1111
.
Formation of a deposited film using the deposited film forming apparatus described above is carried out, for example, as described below.
First, cylindrical substrates
1112
as substrates for forming the deposited film thereon are set in the reaction vessel
1111
by use of substrate holding means
1113
and the inside of the reaction vessel
1111
is evacuated by the unrepresented exhaust device (for example, a vacuum pump). Subsequently, the temperature of the cylindrical substrates
1112
is set to a predetermined temperature in the range of 200 to 450° C. by the heaters
1114
for heating the respective substrates.
For letting the source gases for formation of the deposited film into the reaction vessel
1111
, after confirming that the valves
1231
to
1236
of the gas cylinders are closed and that the inflow valves
1241
to
1246
, outflow valves
1251
to
1256
, and auxiliary valve
1260
are opened, an exhaust valve (not illustrated) is first opened to evacuate the inside of the reaction vessel
1111
and the gas pipe
1119
.
When the vacuum gauge (not illustrated) reaches about 6.7×10
−4
Pa, the auxiliary valve
1260
and outflow valves
1251
to
1256
are closed. Thereafter, the cylinder valve
1231
to
1236
are opened to introduce each gas from the corresponding gas cylinder
1221
to
1226
and the pressure of each gas is adjusted to about 2 kg/cm
2
by pressure regulator
1261
to
1266
. Then the inflow valve
1241
to
1246
are gradually opened to introduce each gas into the mass flow controller
1211
to
1216
.
After completion of the preparation for film formation as described above, formation of each layer is carried out according to the following procedures. When the cylindrical substrates
1112
reach a predetermined temperature, necessary valves out of the outflow valves
1251
to
1256
, and the auxiliary valve
1260
are gradually opened to introduce predetermined gases from the corresponding gas cylinders
1221
to
1226
through the gas inlet pipe
1115
into the reaction vessel
1111
. Then each source gas is adjusted to a predetermined flow rate by the corresponding mass flow controller
1211
to
1216
. On that occasion, the aperture of the exhaust valve (not illustrated) is adjusted with observing the vacuum gauge (not illustrated) so that the pressure inside the reaction vessel
1111
is not more than 1.3×10
2
Pa. When the internal pressure becomes stable, the high-frequency power supply
1117
, for example, of the frequency 13.56 MHz is set to a desired power and the high-frequency power is supplied via the high-frequency matching box
1118
and cathode electrode
1116
into the reaction vessel
1111
, thereby inducing the glow discharge. The source gases introduced into the reaction vessel
1111
are decomposed by this discharge energy to form a predetermined deposited film having the matrix of silicon on the cylindrical substrates
1112
. After the film is formed in a desired thickness, the supply of the high-frequency power is stopped and the outflow valves are closed to stop the flow of the gases into the reaction vessel
1111
, thereby completing the formation of the deposited film.
A photosensitive layer can be formed in a multilayer structure by repeating the above-described operation.
Multiple layers may be formed continuously to gradually change the high-frequency power, gas flow rates, and pressure to their set values for the next layer in a fixed time after completion of formation of one layer.
It is needless to mention that all the outflow valves other than those for necessary gases are closed during the formation of each layer. In addition, an operation for closing the outflow valves
1251
to
1256
, opening the auxiliary valve
1260
, and fully opening the exhaust valve (not illustrated) to evacuate the inside of the system once to a high vacuum is carried out as needed in order to prevent the gases from remaining inside the reaction vessel
1111
and inside the pipe from the outflow valves
1251
to
1256
to the reaction vessel
1111
. During the formation of the deposited film, a motor
1120
is driven to rotate a rotational shaft
1122
via gears
1121
and in turn rotate each cylindrical substrate
1112
, whereby the deposited film is formed throughout the entire circumference of the surface of each cylindrical substrate
1112
.
Although good a-Si base electrophotographic photosensitive members are formed by the above-stated apparatus and method, the above apparatus and method require further improvement in order to enhance the overall characteristics.
Particularly, the increase in the speed of the electrophotographic apparatus is advancing rapidly and there are demands for further enhancement of electrical characteristics of the electrophotographic photosensitive members.
As the performance of the main body of copiers is rapidly improving and as digital copiers and color copiers have spread in recent years, the electrophotographic photosensitive members are required to implement further enhancement of image characteristics such as higher quality of image or higher quality of product than heretofore.
Further, as the size of copying machines is decreasing and as the demand for light receiving members such as printers is increasing, the demand for the electrophotographic photosensitive members of smaller diameters is also increasing. Development is

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