Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1999-08-05
2001-09-18
Beck, Shrive P. (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S571000, C427S248100, C427S294000, C216S067000, C216S071000
Reexamination Certificate
active
06291029
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma processing apparatus and a plasma processing method which can be suitably used as, e.g., a plasma CVD apparatus useful to semiconductor devices such as an electrophotographic photosensitive device, an image input line sensor, an image pickup device, and a photovoltaic device, a sputtering apparatus for forming, e.g., insulating films and metal interconnecting lines as semiconductor devices and optical elements, and an etching apparatus for semiconductor devices and the like.
2. Related Background Art
In the fabrication of semiconductors and the like devices, various plasma processing methods and apparatuses are used in accordance with the intended uses. For example, apparatuses and methods using the characteristics of plasma are used in, e.g., the formation of oxide films, nitride films, and amorphous silicon semiconductor films using a plasma CVD process, the formation of metal interconnecting layers using a sputtering process, and the fine processing techniques using etching. Also, as demands on the film quality and the performance are increasing recently, various improvements are being examined. In particular, a plasma process using high frequency power is extensively used because of the advantages that 1) discharge is stable, and 2) process can be applied to insulating materials such as an oxide film and a nitride film.
As one example of a plasma CVD apparatus generally used in the formation of deposited films,
FIG. 1
shows a plasma processing apparatus as a film formation apparatus for an amorphous silicon film (to be referred to as an a-Si film hereinafter) for a cylindrical electrophotographic photosensitive body.
In
FIG. 1
, the apparatus comprises a reaction vessel
201
which can be evacuated. This reaction vessel
201
is connected to an evacuating means
209
for evacuating the vessel and a gas supply means
210
for supplying a gas into the vessel.
In the reaction vessel
201
, a cylindrical cathode electrode
202
electrically insulated from the reaction vessel
201
by an insulating material
211
is arranged. Additionally, a cylindrical film formation substrate
203
is arranged as a counter electrode inside the cathode electrode
202
. The film formation substrate
203
is held by a substrate holder
204
having a rotating mechanism driven by a motor
212
. A heater
205
is positioned in the internal space of the film formation substrate
203
. The film formation substrate
203
can be heated to a predetermined temperature from the inside by the heater
205
arranged in the internal space. The cathode electrode
202
is connected to a high frequency power supply
207
for discharge via a matching circuit
208
.
Note that the oscillation frequency of a discharge high frequency power supply used in a plasma process such as plasma CVD is commonly 13.56 MHz. The oscillation frequency of the high frequency power supply
207
is also 13.56 MHz.
An a-Si film formation method using this plasma processing apparatus will be described below.
First, the reaction vessel
201
is evacuated to a high vacuum by the evacuating means
209
. Thereafter, the gas supply means
210
supplies a source gas such as silane gas, disilane gas, methane gas, or ethane gas and a doping gas such as diborane gas to maintain the pressure at several tens of millitorr to a few torr. Subsequently, the high frequency power supply
207
supplies high frequency power of 13.56 MHz to the cathode electrode
202
to generate a plasma between the cathode electrode
202
and the film formation substrate
203
, thereby decomposing the source gas. Consequently, an a-Si film is deposited on the film formation substrate
203
heated to about 200° C. to 350° C. by the heater
205
.
In the above apparatus using the 13.56-MHz high frequency power, even the maximum deposition rate at which a-Si films meeting the performance of a recent electrophotographic photosensitive body can be formed is at most about 6 (&mgr;m/hour). If the deposition rate is further increased, it is sometimes impossible to obtain satisfactory characteristics as a photosensitive body. Generally, when an a-Si film is used as an electrophotographic photosensitive body, a film thickness of at least 20 to 30 &mgr;m is necessary to obtain charging power. Accordingly, a long processing time is required to manufacture an electrophotographic photosensitive body meeting the required performance.
As a method of increasing the deposition rate, a plasma CVD process (Plasma Chemistry and Plasma Processing, Vol. 7, No. 3, (1987) pp. 267-273) is reported. This technique suggests that the deposition rate can be increased without lowering the performance of the deposited film by increasing the discharge frequency to be higher than 13.56 MHz by using a high frequency power supply with a frequency higher than 13.56 MHz. This method of increasing the discharge frequency is performed in the field of sputtering and the like and has been extensively studied.
As described above, the conventional plasma processing apparatus has the drawback that a long processing time is required to manufacture an electrophotographic photosensitive body and the like. Therefore, it is necessary to decrease the deposition time without lowering the performance of the deposited film.
Unfortunately, it is found that if a frequency higher than 13.36 MHz, e.g., a high frequency of 100 MHz, is directly applied to the conventional apparatus, the deposition rate of the deposited film varies, or etching cannot be evenly performed. That is, it turns out that it is difficult to perform uniform plasma processing or film deposition on a substrate with a relatively large area.
This degrades various characteristics of the deposited film. The conventional plasma processing apparatus has many problems to be solved in order to form a deposited film having uniform characteristics at a uniform deposition rate.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above conventional problems and provide a plasma processing apparatus and a plasma processing method capable of evenly performing plasma processing on a substrate having a relatively large area at a processing rate which cannot be achieved by any conventional plasma processing apparatus.
It is another object of the present invention to provide a plasma processing apparatus and a plasma processing method capable of forming a deposited film having uniform or substantially uniform characteristics in its entirety.
It is still another object of the present invention to provide a plasma processing apparatus and a plasma processing method capable of forming a deposited film at a uniform or substantially uniform deposition rate regardless of the position on a substrate where the film is deposited.
It is still another object of the present invention to provide a plasma processing apparatus and a plasma processing method capable of performing etching processing uniformly or substantially uniformly for an object to be etched.
It is still another object of the present invention to provide a plasma processing apparatus or method capable of generating a plasma uniformly or substantially uniformly.
The present invention provides a plasma processing apparatus comprising a reaction vessel having a dielectric member in a portion thereof, capable of accommodating a film formation substrate or an object to be processed, and capable of being evacuated, gas supply means for supplying a predetermined gas into the reaction vessel, a cathode electrode provided outside the reaction vessel and arranged in a position where the cathode electrode opposes the film formation substrate or the object to be processed accommodated in the reaction vessel via the dielectric member, and high frequency power supply means for supplying high frequency power of 30 MHz to 300 MHz to the cathode electrode.
The present invention also provides a plasma processing method performed in a plasma processing apparatus comprising a reaction vessel having a dielectric member
Okamura Nobuyuki
Takaki Satoshi
Yamagami Atsushi
Barr Michael
Beck Shrive P.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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