Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2001-07-06
2004-07-13
Hassanzadef, P. (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
Reexamination Certificate
active
06761128
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma treatment method and a plasma treatment apparatus which are used when material gases are decomposed by utilizing the phenomenon of discharge, to form deposited films on substrates or to etch or surface-modify the deposited films formed on substrates. More particularly, this invention relates to a plasma treatment method and a plasma treatment apparatus which are to form on substrates deposited films, in particular, functional deposited films, especially amorphous semiconductors used in semiconductor devices, electrophotographic light-receiving members, image input line sensors, imaging devices, photovoltaic devices and so forth.
2. Related Background Art
As device members used in semiconductor devices, electrophotographic light-receiving members, image input line sensors, imaging devices, photovoltaic devices and other various electronic devices and optical devices, non-single-crystal deposited films such as amorphous silicon as exemplified by amorphous silicon compensated with hydrogen and/or halogen (e.g., fluorine or chlorine) or crystalline deposited films such as diamond thin films have been proposed, some of which have been put into practical use. Such deposited films are formed by plasma CVD (chemical vapor deposition), i.e., a process in which material gases are decomposed by glow discharge produced by high-frequency or microwave power, to form deposited films on substrates made of stainless steel, aluminum or the like. Treatment methods and treatment apparatus therefor are also proposed in variety.
As an example of such apparatus,
FIGS. 12A and 12B
diagrammatically illustrates an example of the construction of a conventional apparatus for producing electrophotographic light-receiving members by high-frequency plasma CVD.
FIG. 12A
is its vertical cross-sectional view, and
FIG. 12B
, a transverse cross-sectional view along the line
12
B—
12
B in FIG.
12
A.
This apparatus is constituted basically of a deposition system
1001
having a reactor
1004
formed of a cylindrical dielectric member, a feed system
1002
for feeding material gases into the reactor
1004
, and an evacuation system
1030
for evacuating the inside of the
1004
.
The deposition system
1001
has a first space
1005
formed inside the reactor
1004
and a second space
1006
formed between the reactor
1004
and a shield wall
1017
. Cylindrical substrates
1010
, members on which deposited films are formed, are each set to a substrate holder
1012
and is placed in the first space
1005
. Also, in the first space
1005
, a heater
1016
for heating each substrate from its interior and a material gas feed pipe
1015
are provided. Meanwhile, in the second space
1006
, cathode rodlike electrodes
1011
are provided in substantially parallel to the sidewall of the reactor
1004
, and a high-frequency power source
1040
is connected thereto via a high-frequency matching device
1041
. The material gas feed system
1002
has cylinders (not shown) individually holding therein material gases such as SiH
4
, GeH
4
, H
2
, CH
4
, B
2
H
6
and PH
3
, valves (not shown) and mass flow controllers (not shown). The individual material gas cylinders are connected to the material gas feed pipe
1015
leading to the inside of the reactor
1004
via a valve
1026
.
Using such a deposited film formation apparatus, deposited films are formed on the cylindrical substrates
1010
in the following way, for example.
First, the cylindrical substrates
1010
, having been precisely cleaned in a dust-controlled environment such as a clean room, are each set to the substrate holder
1012
and disposed in the reactor
1004
. Then, the inside of the reactor
1004
is evacuated by means of the evacuation system
1030
.
Subsequently, a substrate-heating gas for heating the cylindrical substrates
1010
is fed into the reactor
1004
via the material gas feed pipe
1015
. Next, by means of a mass flow controller (not shown), the substrate-heating gas is regulated so as to flow at a prescribed flow rate. To do so, the extent of opening of an evacuation valve
1031
is so regulated, watching a vacuum gauge (not shown), that the internal pressure of the reactor
1004
may come to be a prescribed pressure of, e.g., 133 Pa or below. At the time the internal pressure of the reactor
1004
has become stable, the temperature of each cylindrical substrate
1010
is controlled by the substrate heater
1016
to a prescribed temperature of from 50° C. to 450° C.
At the time the cylindrical substrates
1010
have come to have a prescribed temperature, material gases are fed into the reactor
1004
regulating each material gases so as to flow at a prescribed flow rate by means of mass flow controllers (not shown). To do so, the extent of opening of the evacuation valve
1031
is so regulated, watching a vacuum gauge (not shown), that the internal pressure of the reactor
1004
may come to be a prescribed pressure of, e.g., 133 Pa or below.
At the time the internal pressure of the reactor
1004
has become stable, the high-frequency power source
1040
having a frequency of, e.g., 105 MHz is set at a prescribed power and the high-frequency power is supplied into the reactor
1004
through the high-frequency matching device
1041
to cause glow discharge to take place. By the energy of this discharge, the material gases fed into the reactor
1004
are decomposed, so that the desired deposited films composed chiefly of silicon are formed on the cylindrical substrates
1010
.
After the deposited films have come to have the desired layer thickness, the supply of high-frequency power and flowing of material gases into the reactor
1004
are stopped to finish the formation of deposited films.
Then, the like procedure may be repeated a plurality of times to form light-receiving layers having the desired multi-layer structure.
Here, needless to say, valves other than those for necessary gases are closed when respective layers are formed. Also, the operation to full open the evacuation valve
1031
to once evacuate the inside of the system to a high vacuum is optionally made in order to avoid the respective gases from remaining in the reactor
1004
and in the piping which leads to the reactor
1004
. Also, during the formation of deposited films, the cylindrical substrates
1010
are rotated by driving a motor
1020
.
In the case where plasma treatment is made in this way, the impedance on the load side and the impedance on the high-frequency power source side are matched by means of the high-frequency matching device
1041
. The impedance on the load side involves a stray capacitance component, an inductance component and a resistance component, and hence may greatly change depending on the conditions for plasma treatment and the shape of the apparatus for making the plasma treatment. Hence, the regulation of impedance requires specific values for each apparatus or for each plasma treatment condition.
As a method for matching impedances, it is common to match impedances by changing the capacitance of variable capacitors in a &pgr;-type or T-type circuit provided in the matching device. Also, when it is insufficient to regulate the impedance only in the matching device, as disclosed in, e.g., Japanese Patent Application Laid-Open No. 9-310181, capacitors are attached individually to a plurality of cathode electrodes so that the distance between the matching device and the cathode electrodes can be made larger whereby any changes in the induction component can be cancelled to match impedances. As also disclosed in Japanese Patent Application Laid-Open No. 8-253862, the length of an electrode lead-in shaft connected to a plasma-generating electrode and that of a coaxial cylindrical earth shield are set variable so as to enable adaptation to a variety of power source frequencies.
Such conventional methods and apparatus have attained a good state of matching. However, there is further room for improvement when it is intended to form deposited films in a good eff
Abe Yukihiro
Akiyama Kazuyoshi
Aoike Tatsuyuki
Hosoi Kazuto
Murayama Hitoshi
Crowell Michelle
Hassanzadef P.
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