U.S. patent application number 09/842154 was filed with the patent office on 2002-03-14 for vacuum processing methods.
Invention is credited to Abe, Yukihiro, Akiyama, Kazuyoshi, Aoike, Tatsuyuki, Hosoi, Kazuto, Murayama, Hitoshi, Ohtsuka, Takashi, Shirasuna, Toshiyasu, Tazawa, Daisuke.
Application Number | 20020029818 09/842154 |
Document ID | / |
Family ID | 18649183 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020029818 |
Kind Code |
A1 |
Murayama, Hitoshi ; et
al. |
March 14, 2002 |
Vacuum processing methods
Abstract
For making it feasible to suit to vacuum processing utilizing a
system consisting of an exhaust section and a separable vacuum
processing vessel section, to ensure flexibility of production, to
prevent dust from attaching onto an article, so as to achieve
increase in non-defective percentage of vacuum-processed articles,
and also to suppress variability in vacuum processing
characteristics among lots, an article is loaded into a movable
vacuum processing vessel section, the vacuum processing vessel
section is preliminarily pressure-reduced and moved, the vacuum
processing vessel section is connected to an exhaust section, and
communication is established between the vacuum processing vessel
section and the exhaust section to perform vacuum processing. A
first opening provided in the vacuum processing vessel section is
connected to a second opening provided in the exhaust section and a
vacuum seal valve of the first opening which is openable and
closable, is opened. When opening the valve, the internal pressure
of the vacuum processing vessel under reduced pressure is set
higher than the pressure of another pressure-reduced space to be
brought into communication therewith by the opening of the
valve.
Inventors: |
Murayama, Hitoshi;
(Shizuoka-ken, JP) ; Aoike, Tatsuyuki;
(Mishima-shi, JP) ; Shirasuna, Toshiyasu;
(Mishima-shi, JP) ; Akiyama, Kazuyoshi;
(Mishima-shi, JP) ; Ohtsuka, Takashi; (Susono-shi,
JP) ; Tazawa, Daisuke; (Mishima-shi, JP) ;
Hosoi, Kazuto; (Mishima-shi, JP) ; Abe, Yukihiro;
(Shizuoka-ken, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
18649183 |
Appl. No.: |
09/842154 |
Filed: |
April 26, 2001 |
Current U.S.
Class: |
141/65 ;
141/98 |
Current CPC
Class: |
H01L 21/67017 20130101;
H01L 21/67126 20130101 |
Class at
Publication: |
141/65 ;
141/98 |
International
Class: |
B65B 001/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2000 |
JP |
2000-142162 |
Claims
What is claimed is:
1. A vacuum processing method comprising placing an article in a
vacuum processing vessel and subjecting the article to at least one
vacuum processing step therein with the vacuum processing vessel
communicating with a pressure-reduced space different therefrom
under reduced pressure, wherein the vacuum processing vessel has at
least a first openable/closable opening, wherein the
pressure-reduced space different from the vacuum processing vessel
has at least a second opening, wherein the communication between
the vacuum processing vessel and the pressure-reduced space
different therefrom is established when, after closely connecting
the first opening and the second opening to each other, the first
openable/closable opening is brought into an open state, wherein
for the connection, the vacuum processing vessel having the article
placed therein is moved to locate the first opening and the second
opening at closely connectable positions, and the first and second
openings are connected to each other, and during the movement and
connection, the first opening is kept in a closed state and the
interior of the vacuum processing vessel is kept in a
pressure-reduced state, wherein, for carrying out the at least one
vacuum processing step, the communication between the different
pressure-reduced space and the vacuum processing vessel with their
respective openings being connected to each other is established by
opening the first opening kept in the closed state during the
connection, in a state in which the interior of the different
pressure-reduced space is also kept in a pressure-reduced state,
and wherein the internal pressure of the vacuum processing vessel
kept in the pressure-reduced state during the movement and
connection is set higher than the internal pressure of the
different pressure-reduced space kept in the pressure-reduced
state, when opening the first opening to establish the
communication.
2. The vacuum processing method according to claim 1, wherein the
internal pressure of the vacuum processing vessel kept in the
pressure-reduced state during the movement and connection is not
more than 1.times.10.sup.3 Pa.
3. The vacuum processing method according to claim 1, wherein the
internal pressure of the vacuum processing vessel kept in the
pressure-reduced state during the movement and connection is not
more than 1.times.10.sup.2 Pa.
4. The vacuum processing method according to claim 1, wherein when
P1 (Pa) represents the internal pressure of the vacuum processing
vessel in the pressure-reduced state and P2 (Pa) represents the
internal pressure of the different pressure-reduced space kept in
the pressure-reduced state, which are brought into communication
with each other by opening the first opening after the connection,
the difference between P2 and P1 upon the communication satisfies
the following relation:P1-P2.gtoreq.0.1 Pa.
5. The vacuum processing method according to claim 4, wherein the
difference between P2 and P1 satisfies the following
relation:P1-P2.gtoreq.1 Pa.
6. The vacuum processing method according to claim 1, comprising
varying an exhaust resistance between the different
pressure-reduced space and the vacuum processing vessel to be
brought into communication with each other, after opening the first
opening to establish the communication.
7. The vacuum processing method according to claim 6, comprising
continuously or stepwise decreasing the exhaust resistance between
the different pressure-reduced space and the vacuum processing
vessel to be brought into communication with each other, after
opening the first opening to establish the communication.
8. The vacuum processing method according to claim 1, wherein the
at least one vacuum processing step, to which the article is
subjected in the mutually communicating state of the different
pressure-reduced space and the vacuum processing vessel, comprises
a deposited film forming step.
9. The vacuum processing method according to claim 8, wherein the
deposited film forming step as the at least one vacuum processing
step comprises the step of forming a deposited film having a
plurality of regions which are different at least in composition
from each other.
10. The vacuum processing method according to claim 8, wherein the
deposited film forming step is at least one step of formation of a
deposited film for producing an electrophotographic photosensitive
member.
11. A vacuum processing method comprising the steps of effecting
interconnection and disconnection between the interior of a
pressure-reduced vacuum processing vessel and a pressure-reduced
space, and subjecting an article housed in the vacuum processing
vessel to a vacuum processing, wherein the interconnection is
effected in a state such that at least the pressure inside the
vacuum processing vessel is higher than the pressure of the
pressure-reduced space.
12. The vacuum processing method according to claim 11, wherein
before the interconnection or after the disconnection the pressure
inside the vacuum processing vessel is set to not more than
1.times.10.sup.3 Pa.
13. The vacuum processing method according to claim 11, wherein
before the interconnection or after the disconnection the pressure
inside the vacuum processing vessel is set to not more than
1.times.10.sup.2 Pa.
14. The vacuum processing method according to claim 11, wherein
when P1 (Pa) represents the pressure inside the vacuum processing
vessel in the pressure-reduced state before the interconnection and
P2 (Pa) represents the pressure of the pressure-reduced space, the
pressure difference between the pressures P1 and P2 satisfies the
following relation:P1-P2.gtoreq.0.1 Pa.
15. The vacuum processing method according to claim 14, wherein the
difference between P2 and P1 satisfies the following
relation:P1-P2.gtoreq.1 Pa.
16. The vacuum processing method according to claim 11, wherein the
pressure-reduced space is an exhaust path and the exhaust
resistance of the exhaust path is varied after the
interconnection.
17. The vacuum processing method according to claim 16, wherein the
exhaust resistance of the exhaust path is decreased continuously or
stepwise after establishing communication between the interior of
the vacuum processing vessel and the exhaust path.
18. The vacuum processing method according to claim 11, comprising
forming a deposited film in the vacuum processing vessel which is
in interconnection with the pressure-reduced space.
19. The vacuum processing method according to claim 11, wherein the
pressure-reduced space comprises an exhaust path.
20. The vacuum processing method according to claim 18, wherein the
deposited film comprises a semiconductor film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to vacuum processing methods
and, more particularly, to vacuum processing methods of carrying
out some processing of an article in a reaction vessel (or
container) kept in a pressure-reduced state. More specifically, the
invention concerns methods of subjecting an article in a reaction
vessel kept in a pressure-reduced state to such processing as
deposited film formation, etching, and so on, which is used in
steps of producing semiconductor devices, photosensitive members
for electrophotography, line sensors for image inputting, image
pickup devices, photovoltaic devices, and so on. Further, the
invention relates to methods of producing the semiconductor
devices, photosensitive members for electrophotography, line
sensors for image inputting, image pickup devices, photovoltaic
devices, etc. by making use of the aforementioned vacuum processing
method in steps thereof.
[0003] 2. Related Background Art
[0004] Conventionally, a number of methods are known as vacuum
processing methods used in the steps of producing the semiconductor
devices, photosensitive members for electrophotography, line
sensors for image inputting, image pickup devices, photovoltaic
devices, other various electronic devices, optical elements, and so
on; e.g., vacuum evaporation, sputtering, ion plating, thermal CVD,
photo CVD, plasma CVD, plasma etching, and so on. In addition,
systems for carrying out the methods are also put into practical
use.
[0005] For example, the plasma CVD methods, i.e., methods of
decomposing a source gas by a dc or high frequency or microwave
glow discharge to form a thin deposited film on a substrate, are
practically used as favorable deposition forming means for
production of various electron devices. For example, they are
utilized in formation of a deposited film of hydrogenated amorphous
silicon (hereinafter referred to as "a-Si:H") for
electrophotography, or the like, and various systems for them have
been also proposed heretofore.
[0006] It is possible to perform desired vacuum processing or to
form a deposited film with desired characteristics by use of the
systems proposed heretofore. For a vacuum processing method
including the steps of preparing a vacuum processing system
constructed of a reaction vessel and an exhauster separable from
each other, connecting the reaction vessel to the exhauster for
every lot, and thereafter carrying out vacuum processing, there are
also proposals of apparatus having both high system operation
efficiency and flexibility in production. Utilizing this advantage,
improvement has been vigorously made recently, particularly, in
vacuum processing methods suitable for multi-product
production.
[0007] However, the market demand level has been becoming higher
day after day, not only for the improvement in productivity, but
also for the performance of products made by such vacuum processing
methods. In order to meet this demand, therefore, there is a
continuing need for development of a vacuum processing method that
permits production of products with higher quality and that has a
high productivity.
[0008] For example, in the case of the electrophotographic
photosensitive members produced by plasma CVD, since digital,
electrophotographic systems and color electrophotographic systems
under spectacular spread in recent years are frequently operated to
make copies of photographs, pictures, design graphics, etc. and
output images, as well as letter documents, the demand level is
very high for the quality of images formed thereby. It is thus of
urgent necessity to provide electrophotographic apparatus adaptable
for these requirements for high image quality. Technical studies
have been done toward improvement in the quality of copied images
from various aspects including investigation of the image forming
process itself, and among others, the improvement in the
characteristics of the photosensitive members for
electrophotography is an inevitable subject. For accomplishing this
subject, there are strong demands for achievement of a method of
forming a photosensitive member for electrophotography capable of
achieving improvement in vacuum processing characteristics and also
capable of maintaining a high non-defective unit percentage (simply
referred to as "non-defective percentage"), based on stable
processing characteristics.
[0009] Under such circumstances, it is the present status that the
conventional vacuum processing methods described above are still
susceptible to improvement. In the vacuum processing method using
the vacuum processing system in the structure wherein the reaction
vessel and exhauster are separable from each other, as described
above, the flexibility of production is improved. In this method,
since the reaction vessel is moved with a substrate to be processed
being placed inside prior to vacuum processing, there remains the
subject of how dust is effectively prevented from attaching onto
the substrate during the movement. One of countermeasures against
it is a method of, prior to placement of the substrate in the
reaction vessel, connecting the reaction vessel to the exhauster
and then placing the substrate in the reaction vessel in that
state. For adopting this substrate placement method, however, it
becomes necessary to employ a new means for carrying the substrate
into the reaction vessel while preventing the attachment of dust.
Further, the vacuum processing cannot be started during the period
between the placement of the substrate and completion of a
pressure-reducing step of evacuating the interior of the reaction
vessel and the time necessary for this evacuation is not so short,
which thus leads to time loss in production tact.
[0010] In this vacuum processing method there readily occur
variability in the vacuum processing characteristics among lots and
thus there remains the subject of how the variability among lots
are to be suppressed.
SUMMARY OF THE INVENTION
[0011] The present invention has been accomplished to solve the
above subjects and an object of the invention is to provide a
vacuum processing method that permits execution of stable vacuum
processing and that permits deposited films to be formed without
variability in quality.
[0012] Another object of the present invention is to provide a
vacuum processing method of moving a vacuum processing vessel
having an article placed therein, connecting the vacuum processing
vessel to a pressure-reduced space different therefrom, and
thereafter carrying out at least one vacuum processing step, which
comprises novel means that enables attainment of improvement in
non-defective percentage of vacuum-processed articles without
degrading the flexibility of production while preventing the
attachment of dust onto the articles and that also enables
attainment of suppression of the variability of the vacuum
processing characteristics among lots.
[0013] Still another object of the present invention is to provide
a vacuum processing method capable of preventing the attachment of
dust onto an article in a step of moving a vacuum processing vessel
having the article placed therein and connecting the vacuum
processing vessel to a pressure-reduced space different
therefrom.
[0014] Another object of the present invention is to provide a
vacuum processing method that excludes factors to cause the
variability in the vacuum processing characteristics among lots and
has a step configuration also excellent in the flexibility of
production.
[0015] According to an aspect of the present invention, there is
provided a vacuum processing method which comprises placing an
article in a vacuum processing vessel and subjecting the article to
at least one vacuum processing step therein with the vacuum
processing vessel communicating with a pressure-reduced space
different therefrom under reduced pressure,
[0016] wherein the vacuum processing vessel has at least a first
openable/closable opening,
[0017] wherein the pressure-reduced space different from the vacuum
processing vessel has at least a second opening,
[0018] wherein the communication between the vacuum processing
vessel and the pressure-reduced space different therefrom is
established when, after closely connecting the first opening and
the second opening to each other, the first openable/closable
opening is brought into an open state,
[0019] wherein for the connection, the vacuum processing vessel
having the article placed therein is moved to locate the first
opening and the second opening at closely connectable positions,
and the first and second openings are connected to each other, and
during the movement and connection, the first opening is kept in a
closed state and the interior of the vacuum processing vessel is
kept in a pressure-reduced state,
[0020] wherein, for carrying out the at least one vacuum processing
step,
[0021] the communication between the different pressure-reduced
space and the vacuum processing vessel with their respective
openings being connected to each other is established by opening
the first opening kept in the closed state during the connection,
in a state in which the interior of the different pressure-reduced
space is also kept in a pressure-reduced state, and
[0022] wherein the internal pressure of the vacuum processing
vessel kept in the pressure-reduced state during the movement and
connection is set higher than the internal pressure of the
different pressure-reduced space kept in the pressure-reduced
state, when opening the first opening to establish the
communication.
[0023] According to another aspect of the present invention, there
is provided a vacuum processing method comprising the steps of
effecting interconnection and disconnection between the interior of
a pressure-reduced vacuum processing vessel and a pressure-reduced
space, and subjecting an article housed in the vacuum processing
vessel to a vacuum processing, wherein the interconnection is
effected in a state such that at least the pressure inside the
vacuum processing vessel is higher than the pressure of the
pressure-reduced space.
[0024] The present invention is based on the results of intensive
and extensive research to accomplish the above objects, i.e., based
on such finding that it is feasible to accomplish the above objects
by, during movement of the vacuum processing vessel having the
article placed therein, maintaining the pressure inside the vacuum
processing vessel within an appropriate range and connecting the
vacuum processing vessel in this state with another
pressure-reduced space different therefrom.
[0025] The invention will be described hereinafter with examples of
a deposited film forming apparatus.
[0026] Apparatus and methods of forming a deposited film involve
those schematically described below.
[0027] FIG. 1 shows an example of vacuum processing apparatus
applied to the vacuum processing methods. Namely, FIG. 1 is a view
schematically showing one configuration example of the deposited
film forming apparatus by RF plasma CVD (hereinafter abbreviated as
"RF-PCVD") using a frequency in the RF band as a power supply,
specifically, an RF-PCVD system applied to formation of a
light-receiving member for electrophotography. The structure of the
forming apparatus illustrated in FIG. 1 is as follows.
[0028] The RF-PCVD system illustrated in this FIG. 1 is generally
comprised of three sections; specifically, a deposition system
2100, a source gas supply system 2200, and an exhaust system (not
shown) for evacuating the interior of a reaction vessel 2101. In
the deposition system 2100 the reaction vessel 2101 houses a
cylindrical substrate 2112, a substrate support 2113 incorporating
a heater for heating the substrate, and source gas inlet pipes
2114. Further, a high frequency matching box 2115 is connected to a
cathode electrode 2111 making a part of the reaction vessel 2101.
The cathode electrode 2111 is electrically insulated from the earth
potential by insulators 2120, while the cylindrical substrate 2112
is maintained at the earth potential through the substrate support
2113, thus also serving as an anode electrode. A high frequency
voltage can be placed between the cathode electrode 2111 and the
cylindrical substrate 2112.
[0029] The source gas supply system 2200 has source gas cylinders
2221 to 2226 storing respective gases of SiH.sub.4, GeH.sub.4,
H.sub.2, CH.sub.4, B.sub.2H.sub.6, PH.sub.3, etc., valves 2231 to
2236, 2241 to 2246, 2251 to 2256, and mass flow controllers 2211 to
2216. Each of the source gas cylinders is connected via a valve
2260 to the gas inlet pipes 2114 inside the reaction vessel
2101.
[0030] The formation of a deposited film using the RF-PCVD system
illustrated in this FIG. 1 can be carried out, for example,
according the following procedures.
[0031] First, the cylindrical substrate 2112 is placed in the
reaction vessel 2101 and the interior of the reaction vessel 2101
is evacuated by the unrepresented exhaust system (e.g., a vacuum
pump). Then, the temperature of the cylindrical substrate 2112 is
controlled to a predetermined temperature of 200.degree. C. to
350.degree. C. by the substrate-heating heater built in the
substrate support 2113.
[0032] For flowing the source gas for formation of the deposited
film from the source gas supply system 2200 into the reaction
vessel 2101, for example, the following procedures are carried
out.
[0033] First, it is confirmed that the valves 2231 to 2237 of the
gas cylinders and a leak valve 2117 of the reaction vessel are
closed and also that the gas inlet valves 2241 to 2246, outlet
valves 2251 to 2256, and auxiliary valve 2260 are opened. Then, a
main valve 2118 is opened to evacuate the interior of the reaction
vessel 2101 and the interior of gas pipe 2116.
[0034] When the reading of a vacuum gauge 2119 reaches about
7.times.10.sup.-4 Pa, the auxiliary valve 2260 and outlet valves
2251 to 2256 are closed.
[0035] After that, the valves 2231 to 2236 are opened to introduce
the respective gases from the gas cylinders 2221 to 2226 and a
pressure of each gas is controlled to a predetermined pressure,
e.g., to 2 kg/cm.sup.2 by pressure regulators 2261 to 2266. Then,
the inlet valves 2241 to 2246 are gradually opened to introduce the
respective gases into the mass flow controllers 2211 to 2216.
[0036] After completion of the above preparation operation to
complete preparation for deposition, each of layers is formed
according to the following procedures.
[0037] When the cylindrical support 2112 reaches a predetermined
temperature, one or some needed out of the outlet valves 2251 to
2256, and the auxiliary valve are gradually opened to introduce
predetermined gas from the gas cylinders 2221 to 2226 through the
gas inlet pipes 2114 into the reaction vessel 2101. Then, each
source gas is regulated to a predetermined flow rate by the mass
flow controller 2211 to 2216. On that occasion, the aperture of the
main valve 2118 is adjusted so as to control the pressure in the
reaction vessel 2101 to a predetermined value while monitoring the
vacuum gauge 2119. After the internal pressure becomes stable, the
RF power supply (not shown), for example, of the frequency of 13.56
MHz, is set to a desired power to introduce the RF power through
the high frequency matching box 2115 and the cathode 2111 into the
reaction vessel 2101 whereby glow discharge occurs with the
cylindrical substrate 2112 acting as an anode. This discharge
energy decomposes the source gas introduced into the reaction
vessel and a deposited film comprising prescribed silicon as a
matrix is formed on the cylindrical substrate 2112. The formation
of the deposited film is carried on for a predetermined time. When
the deposited film is formed in a desired thickness, the supply of
RF power is stopped and the outlet valves are closed to stop the
flow of gas into the reaction vessel, thus terminating the
formation of the deposited film.
[0038] Similar operation is carried out a desired number of times,
e.g., several times, thereby forming deposited films in desired
multi-layer structure, e.g., a light-receiving layer.
[0039] It is needless to mention that in the production of the
deposited films in the multi-layer structure described above, the
outlet valves other than those of necessary gases are all closed
during formation of each of the layers. In order to prevent the gas
utilized in formation of a previous layer from remaining in the
reaction vessel 2101 and in the pipe from the outlet valves 2251 to
2256 to the reaction vessel 2101, an operation of closing the
outlet valves 2251 to 2256, opening the auxiliary valve 2260, and
fully opening the main valve 2118 to evacuate the interior of the
system once to a high vacuum, is carried out before formation of a
next layer as occasion may demand.
[0040] In order to uniformize the film formed, it is also effective
to rotate the cylindrical substrate 2112 at a predetermined speed
by a driving unit (not shown) during formation of the layers.
[0041] Further, it is needless to mention that the gas species and
valve operations described above are subject to change according to
production conditions of the respective layers.
[0042] In addition to the deposited film forming apparatus and
forming methods by the RF plasma CVD method using the frequency in
the RF band, which have been commonly used heretofore, the VHF
plasma CVD (hereinafter abbreviated as "VHF-PCVD") using the high
frequency power in the VHF band is drawing attention in recent
years. Further, development is also active in formation of various
deposited films by this VHF plasma CVD method. The reason is that
the VHF-PCVD method has the advantages of a high film deposition
rate and capability of providing the deposited film with high
quality and is thus expected as means capable of simultaneously
attaining cost reduction and high quality of products. For example,
U.S. Pat. No. 5,534,070 (Japanese Patent Application Laid-Open No.
6-287760) discloses the apparatus and method that are applicable to
formation of a-Si based light-receiving members for
electrophotography.
[0043] In addition, development is also under way to develop a
deposited film forming apparatus capable of housing a plurality of
substrates, as illustrated in FIGS. 2A and 2B, which permits
simultaneous formation of a plurality of light-receiving members
for electrophotography and which has an extremely high
productivity.
[0044] FIGS. 2A and 2B are views showing one configuration example
of the deposited film forming apparatus capable of housing a
plurality of substrates, in which FIG. 2A is a schematic, sectional
view and FIG. 2B a schematic, sectional view along a cut line 2B-2B
of FIG. 2A.
[0045] An exhaust duct 311 is integrally formed on a side face of a
reaction vessel 301 and the other end of the exhaust duct 311 is
connected to an exhaust system (not shown). Six cylindrical
substrates 305 to be subjected to the formation of a deposited film
are placed in parallel to each other so as to surround the central
part of the reaction vessel 301. Each cylindrical substrate 305 is
held on a rotation shaft 308 and is arranged to be heated by a
heater 307. When each motor 309 is actuated, the rotation shaft 308
is rotated via a reduction gear 310, so that the cylindrical
substrate 305 rotates about the center axis along the direction of
a generator thereof.
[0046] Source gases are supplied through a source gas supply means
312 into a deposition space 306 surrounded by the six cylindrical
substrates 305. The VHF power is supplied from a VHF power supply
303 via a matching box 304 and a cathode electrode 302 to the
deposition space 306. In this system, the cylindrical substrates
305 are also maintained at the earth potential through the rotation
shafts 308 and thus act as anode electrodes.
[0047] The formation of deposited films using this system
illustrated in FIGS. 2A and 2B, is carried out according to the
procedures schematically described below.
[0048] First, the cylindrical substrates 305 are placed in the
reaction vessel 301 and the interior of the reaction vessel 301 is
evacuated through the exhaust duct 311 by the unrepresented exhaust
system. Then, the cylindrical substrates 305 are heated and
controlled to a predetermined temperature of about 200.degree. C.
to 300.degree. C. by the heaters 307.
[0049] When the cylindrical substrates 305 reach the predetermined
temperature, the source gas is introduced through the source gas
supply means 312 into the reaction vessel 301. After it is
confirmed that the flow rate of the source gas reaches a set value
and the pressure in the reaction vessel 301 becomes stable, the
predetermined VHF power is supplied from the high frequency power
supply 303 via the matching box 304 to the cathode electrode 302.
This places the VHF power between the cathode electrode 302 and the
cylindrical substrates 305 also serving as anode electrodes,
whereby glow discharge occurs in the deposition space 306
surrounded by the cylindrical substrates 305. This glow discharge
excites and dissociates the source gas to form deposited films on
the cylindrical substrates 305.
[0050] After formation of the films in a desired thickness, the
supply of the VHF power is stopped and the supply of the source gas
is also stopped, thereby ending the formation of deposited films.
Like operation is carried out several times to form deposited films
in desired multi-layer structure, e.g., light-receiving layers.
[0051] During the formation of deposited films the cylindrical
substrates 305 are rotated at a predetermined speed through the
rotation shafts 308 by the motors 309 whereby the deposited films
are formed across the entire periphery of the surfaces of the
cylindrical substrates. In addition, this uniformizes the deposited
films obtained.
[0052] Japanese Patent Application Laid-Open No. 8-253865 discloses
the technology of simultaneously forming deposited films on a
plurality of substrates by use of plural electrodes. It describes
that the simultaneous formation of the deposited films on the
plural substrates by use of the plural electrodes permits
attainment of effects of improving the productivity and of
improving uniformity of characteristics of deposited films. The
formation of deposited films in this form can be realized, for
example, by use of a system having the structure as illustrated in
FIGS. 3A and 3B.
[0053] FIGS. 3A and 3B show an example of apparatus employing a
method of simultaneously forming deposited films on plural
substrates by use of plural electrodes, in which FIG. 3A is a
schematic, vertical, sectional view and FIG. 3B a schematic,
horizontal, sectional view. An exhaust duct 405 is integrally
formed on a top surface of a reaction vessel 400 and the other end
of the exhaust duct 405 is connected to an exhaust system (not
shown). Inside the reaction vessel 400, a plurality of cylindrical
substrates 401 to be subjected to the formation of deposited films
are placed in parallel to each other. Each cylindrical substrate
401 is held on a shaft 406 and is arranged to be heated by a heater
407. Each cylindrical substrate 401 is rotated through the shaft
406 by a driving means such as a motor or the like (not shown), as
occasion may demand.
[0054] The VHF power is supplied from a VHF power supply 403 via a
matching box 404 and cathode electrodes 402 into the reaction
vessel 400. In this system, the cylindrical substrates 401 are also
maintained at the earth potential through the shafts 406 and thus
act as anode electrodes.
[0055] Source gases are supplied through unrepresented source gas
supply means set in the reaction vessel 400, into the reaction
vessel 400.
[0056] The formation of deposited films by use of this system in
the structure illustrated in FIGS. 3A and 3B can also be carried
out according to similar procedures to those by the deposited film
forming system described above referring to FIGS. 2A and 2B.
[0057] Meanwhile, a wide variety of products are made today by
making use of such vacuum processing systems and vacuum processing
methods and different vacuum processing systems are often used
depending upon the various products. This diversity results from
application of vacuum processing systems of sizes, materials, etc.
optimal to respective types of products. For example, in the case
of production of photosensitive members for electrophotography, it
is sometimes necessary to change the vacuum processing systems
used, more specifically, the dimensions of the deposited film
forming apparatus, particularly, the cathode sizes, according to
the diameters of the electrophotographic, photosensitive members to
be produced.
[0058] Under the circumstances of the increasing diversity of
products to be produced, when the products are made using the
vacuum processing system consisting of the aforementioned reaction
vessel and exhauster substantially integrated with each other, a
new production line also including another exhauster must be added
in order to newly produce different products, or an existing
production line must be modified to replace the existing reaction
vessel with a new reaction vessel. Naturally, new equipment
investment becomes necessary for the addition of the new production
line. For replacing the existing reaction vessel with a new
reaction vessel, the equipment investment is lower, but production
efficiency also becomes lower, because the production line cannot
be used during the modification.
[0059] Further, in order to produce the conventional products and
new products in parallel, individual production lines have to be
prepared. If there will be change in necessary numbers of
respective products in future, conversion of the systems will be
implemented by modification, but the modification will require a
considerable time, thus failing to adjust the ratio of numbers of
production lines instantly.
[0060] For the purpose of quickly implementing the conversion of
apparatus, attention is recently focused on a type in which the
vacuum processing apparatus is constructed of the reaction vessel
and exhauster separable from each other and in which a reaction
vessel optimal for necessary products is connected to the exhauster
to perform vacuum processing, according to a production plan. This
type of the disconnectable configuration of the reaction vessel and
exhauster has high flexibility in production and makes it feasible
to achieve increase of production efficiency and decrease of
production cost. In this disconnectable system configuration, where
the reaction vessel is arranged movable, the loading of the
substrate into the reaction vessel in the preparation step can be
carried out by moving the reaction vessel to a stage for substrate
loading. Accordingly, the reaction vessel in the fixed structure
required use of a large-scale substrate carrier in order to carry
and load the substrate into each reaction vessel, whereas the
reaction vessel in the movable structure obviates the need for use
of the large-scale substrate carrier and permits simplification of
the production system.
[0061] Therefore, the method of constructing the vacuum processing
apparatus of the reaction vessel and exhauster separable from each
other, connecting the reaction vessel suitable for necessary
products to the exhauster, and then performing vacuum processing,
has many merits and is thus drawing particular attention in recent
years.
[0062] The schematic structure of the system comprised of the
reaction vessel and exhauster in the separable configuration is,
for example, one as illustrated in an example of FIG. 4. FIG. 4
shows an example of the structure in which the reaction vessel and
exhauster are separable from each other and, particularly, in which
the reaction vessel is movable. Numeral 501 designates a movable
reaction vessel section, which consists of a reaction vessel 506, a
vacuum seal valve 508, a connection flange 504, and a carriage 513
on which the reaction vessel 506 is mounted, thereby permitting
movement thereof. Numeral 502 denotes an exhaust section, which
consists of an exhaust means 507, a vacuum seal valve 509, and a
connection flange 505. Numeral 503 represents a connection section
for connection between the reaction vessel section 501 and the
exhaust section 502.
[0063] The structure inside the reaction vessel 506 can be
constructed, for example, in the structure as illustrated in FIGS.
5A and 5B. FIGS. 5A and 5B are schematic views showing an example
of the reaction vessel section in the deposited film forming
apparatus for forming the photosensitive members for
electrophotography. FIG. 5A is a schematic, sectional view and FIG.
5B a schematic, sectional view along a cut line 5B-5B of FIG.
5A.
[0064] An exhaust duct 611 is formed on a side face of a reaction
vessel 601 and the other end of the exhaust duct 611 is connected
to the vacuum seal valve 508 in FIG. 4. An unrepresented conductive
mesh is set in the opening of the exhaust duct in order to prevent
leakage of a high frequency power guided into the reaction vessel,
to the exhaust means side. Cylindrical substrates 605 to be
subjected to the formation of deposited films are placed at equal
intervals and in parallel to each other on a common circle. Each
substrate 605 is held on a rotation shaft 608 and a motor 609
connected thereto is actuated to rotate the rotation shaft 608
through a reduction gear 610, whereby the cylindrical substrate 605
rotates about the center axis along the direction of a generator
thereof. The cylindrical substrates 605 can be heated by respective
heaters 607.
[0065] The high frequency power outputted from a high frequency
power supply 603 is supplied through a matching box 604 and a high
frequency power supply cable 615 and via cathode electrodes 602
into the reaction vessel 601 serving as a deposition space. A
cathode electrode 606 is also placed inside the placement circle of
the cylindrical substrates 605 and the high frequency power
outputted from a high frequency power supply 614 is supplied
through a matching box 613 and a high frequency power supply cable
615 and via the cathode electrode 606 into the reaction vessel
601.
[0066] Source gas supply means 612 are placed inside the reaction
vessel 601 and desired source gas is supplied therethrough into the
reaction vessel 601.
[0067] The vacuum processing using the vacuum processing system
illustrated in the example of FIG. 4 can be carried out according
to the procedures schematically described below, for example, when
the reaction vessel of the movable type is the deposition forming
reaction vessel for formation of photosensitive members for
electrophotography shown in the example of FIGS. 5A and 5B.
[0068] First, the movable reaction vessel section 501 is
disconnected from the exhaust section 502, the connection flange
504 is connected to another exhaust system for loading of
substrates (not shown), and in the thus connected state cylindrical
substrates 605 are loaded into the reaction vessel 601. Then, the
interior of the reaction vessel 601 is evacuated through the
exhaust duct 611 by the exhauster for loading of substrates. It is
needless to mention that the exhaust seal valve 508 is opened
during this evacuation period. After the interior of the reaction
vessel 601 is evacuated to a desired pressure, the vacuum seal
valve 508 is closed and then the connection flange 504 is
disconnected from the substrate-loading exhauster. Then, the
movable reaction vessel section 501 is moved to the placement site
of the exhaust section 502 and the connection flange 504 is brought
into contact with the exhaust-side connection flange 505 through a
vacuum seal and connected therewith. After the connection, the
connection section 503 is fixed by fixing means such as screws,
clamps, etc. as occasion demands.
[0069] After it is confirmed that the movable reaction vessel
section 501 is connected to the exhaust section 502, the
exhaust-side vacuum seal valve 509 is first opened, the interior of
the pipe on the exhaust means 507 side with respect to the
reaction-vessel-side vacuum seal valve 508 is evacuated by the
exhaust means 507, and the reaction-vessel-side vacuum seal valve
508 is then opened to evacuate the interior of the reaction vessel
506.
[0070] This preparation step, i.e., the stage of loading the
substrates into the reaction vessel 506, the stage of moving the
reaction vessel section 501, and the stage of connecting the
reaction vessel section 501 to the exhaust section 502, may also be
carried out, for example, according to procedures of loading the
substrates, thereafter moving the reaction vessel section 501
without evacuating the interior of the reaction vessel 506, and
then connecting the reaction vessel section 501 to the exhaust
section 502, different from the procedures described above. With
those different procedures, a necessary condition is that
evacuation is completed in the reaction vessel 506 etc. to
establish a processable state before a start of an actual vacuum
processing step with the reaction vessel section 501 being
connected to the exhaust section 502. Accordingly, specific
procedures in this preparation step can be adequately determined in
consideration of work efficiency, productivity, etc. in each of
production steps.
[0071] After the interior of the reaction vessel 506 is evacuated
by the exhaust means 507 in this way, the cylindrical substrates
605 are heated and controlled to a predetermined temperature by the
heaters 607 as occasion demands. When the cylindrical substrates
605 reach the predetermined temperature, the source gas is
introduced through the source gas supply means 612 into the
reaction vessel 601. After it is confirmed that the flow rate of
the source gas reaches a set flow rate and the pressure inside the
reaction vessel 601 becomes stable, the predetermined high
frequency power is supplied from the high frequency power supplies
603, 614 via the matching boxes 604, 613 to the cathode electrodes
602, 606. The high frequency power thus supplied induces glow
discharge in the reaction vessel 601 and the glow discharge excites
and dissociates the source gas, whereby deposited films are formed
on the cylindrical substrates 605.
[0072] After the deposited films are formed in a desired thickness,
the supply of a high frequency power is stopped and the supply of
source gas is also stopped, thus terminating the formation of
deposited films. For forming the deposited films in the multi-layer
structure, similar operation is repeated several times. In this
case, the multiple layers may be formed according to procedures of
completely terminating discharge once at the time of completion of
formation of one layer as described above, between two layers,
changing the setting to a gas flow rate and a pressure for a next
layer, and thereafter again inducing discharge to form the next
layer, or the multiple layers may be continuously formed according
to procedures of, after completion of formation of one layer,
gradually varying the gas flow rate, pressure, and high frequency
power to set values for the next layer in a fixed period.
[0073] During the formation of deposited films, the cylindrical
substrates 605 are preferably rotated through the rotation shafts
608 at a predetermined speed by the motors 609 as occasion may
demand. By rotating the cylindrical substrates 605, the deposited
films are formed under the same conditions across the entire
periphery of the surfaces of the cylindrical substrates, thus
achieving better uniformization of the deposited films
obtained.
[0074] After completion of the deposited film forming step in this
way, the source gas in the reaction vessel 506 is adequately purged
or preferably replaced with inert gas, and thereafter the vacuum
seal valves 508, 509 are closed. Then, the connection section 503
is disconnected to bring the reaction vessel section 501 into the
movable state. In this state, the reaction vessel section 501 is
moved to a substrate unloading site.
[0075] As occasion may demand, the substrates 605 are cooled to a
desired temperature, and thereafter an inert gas or the like is
introduced via an unrepresented leak valve into the reaction vessel
506, so as to bring the interior of the reaction vessel 506 into
the atmospheric pressure. After the interior of the reaction vessel
506 reaches the atmospheric pressure, the substrates 605 with the
deposited films thereon are taken out of the reaction vessel
506.
[0076] After that, the components in the reaction vessel 506 are
subjected to replacement, cleaning, etc. to recover the reaction
vessel 506 into a state in which the deposited films can be formed
again. Then, the reaction vessel 506 is again subjected to the
aforementioned substrate loading procedure.
[0077] In the vacuum processing operation of carrying out the three
divisional steps of substrate loading, formation of deposited
films, and substrate unloading at the respective, separate sites,
it is preferable in terms of efficiency to prepare and use a
plurality of reaction vessel sections 501. Namely, in the series of
steps described above, at the stage when, after completion of
formation of deposited films with a reaction vessel section 501
connected to the exhaust section 502, the reaction vessel section
501 is disconnected from the exhaust section 502, another reaction
vessel section 501 already having passed through the preliminary
preparation step of substrate loading is connected to the exhaust
section and the step of formation of deposited films can be started
subsequent thereto. This decreases a wait time and permits
efficient operation as a whole of the apparatus.
[0078] The above described the examples of the apparatus and
methods of forming the electrophotographic, photosensitive members,
and it is noted that similar techniques can also be applied to
other vacuum processing steps, e.g., etching, ion implantation,
etc., or to other vacuum processing methods, e.g., sputtering,
thermal CVD, etc., in addition to the above.
[0079] The above-stated conventional methods can be used to perform
the vacuum processing with desired characteristics, for example, to
form the deposited film well. Among others, the method employing
the vacuum processing system in the separable configuration of the
reaction vessel and exhauster and carrying out the vacuum
processing after connection of the reaction vessel to the exhauster
for every lot, has the flexibility in production, in addition to
the high system operation efficiency. Utilizing this advantage,
improvement has been energetically made particularly in recent
years, as a vacuum processing method suitable for multi-product
production.
[0080] However, as described previously, there are demands for
further improvement in the performance of products made by this
vacuum processing method, as well as improvement in productivity,
in recent years, so that the market demand level is becoming higher
day after day. Accordingly, there are desires for development of a
vacuum processing method that permits the production of products
with high quality and that has a high productivity, in order to
meet the above demand.
[0081] For example, in the case of the electrophotographic,
photosensitive members produced by the plasma CVD method, not only
the letter documents, but also graphics including photographs,
pictures, design images, etc. are frequently copied in the recently
quickly spreading, digital, electrophotographic systems and color
electrophotographic systems and thus the demand level for the
quality of copied images is becoming very high, e.g., much higher
resolution, high quality of output of halftone images like
photographs, suppression of variability among photosensitive
members or variability in characteristics in one photosensitive
member, which can be the cause of irregular color or chromatic
deviation with formation of color images, and so on. It is thus of
urgent necessity to provide the electrophotographic apparatus
adaptable for these demands for high image quality. Technological
studies toward improvement in quality of copied images has been
conducted from various aspects including the research of image
forming process itself, and among others, the improvement in the
characteristics of the photosensitive members for
electrophotography is an essential subject. For accomplishing this
subject, there are strong needs for attainment of the method of
forming the photosensitive member for electrophotography, which can
accomplish the improvement in the characteristics of vacuum
processing and which is also stable in the processing
characteristics to be able to maintain a high non-defective
percentage. Then, there are earnest hopes for the vacuum processing
method capable of producing the electrophotographic, photosensitive
members with such high quality on a stable basis.
[0082] The present invention has been accomplished in view of this
point and with focus on such knowing that, on the occasion of
carrying out the vacuum processing by use of the processing system
in which the vacuum processing vessel can be moved with the article
being placed in the vacuum processing vessel, the pressure in the
vacuum processing vessel is controlled in the appropriate range and
in this state the vacuum processing vessel is connected to another
pressure-reduced space different therefrom, whereby the vacuum
processing, e.g., formation of a deposited film of a semiconductor
or the like, can be performed at extremely high efficiency and with
extremely high quality.
[0083] Namely, a vacuum processing method of the present invention
is a vacuum processing method in which, in a state where an article
is placed in a vacuum processing vessel and where under reduced
pressure the vacuum processing vessel communicates with another
pressure-reduced space different therefrom, the article is
subjected to at least one step of vacuum processing steps, wherein
the vacuum processing vessel comprises at least a first
openable/closable opening; the pressure-reduced space different
from the vacuum processing vessel comprises at least a second
opening; the communication between the vacuum processing vessel and
the pressure-reduced space different therefrom is established on
the occasion of, after close connection between the first opening
and the second opening, bringing the first openable/closable
opening into an opened state; during execution of the connection,
the vacuum processing vessel with the article being placed therein
is moved to a position where the first opening and second opening
can be closely connected to each other, and the openings are then
connected; during execution of the movement and connection, the
first opening is kept in a closed state and the interior of the
vacuum processing vessel is kept in a pressure-reduced state;
during execution of at least one step of the vacuum processing
steps, the communication between the pressure-reduced space and the
vacuum processing vessel with their openings being connected to
each other is established by opening the first opening kept closed
during the connection, while the interior of the pressure-reduced
space is also kept in a pressure-reduced state; an internal
pressure of the vacuum processing vessel kept in the
pressure-reduced state during the movement and connection is set
higher than an internal pressure of the pressure-reduced space kept
in the pressure-reduced state, on the occasion of opening the first
opening to establish the communication.
[0084] In the vacuum processing method of the present invention, it
is desirable to set the internal pressure of the vacuum processing
vessel kept in the pressure-reduced state during the movement and
connection, preferably to not more than 1.times.10.sup.3 Pa and
more preferably to not more than 1.times.10.sup.2 Pa.
[0085] On the other hand, when P1 [Pa] and P2 [Pa] represent the
internal pressure of the vacuum processing vessel in the
pressure-reduced state and the internal pressure of the
pressure-reduced space in the pressure-reduced state, which are
made to communicate with each other by opening the first opening
after the connection, a difference between P2 and P1 preferably
satisfies the following relation on the occasion of the
communication:
P1-P2.gtoreq.0.1 Pa.
[0086] Further, the difference between P2 and P1 preferably
satisfies the following relation on the occasion of the
communication:
P1-P2.gtoreq.1 Pa.
[0087] In addition, the vacuum processing method of the present
invention preferably comprises an operation of varying exhaust
resistance between the pressure-reduced space and the vacuum
processing vessel communicating with each other, after the first
opening is opened to establish the communication. On that occasion,
the exhaust resistance between the pressure-reduced space and the
vacuum processing vessel communicating with each other is
preferably decreased continuously or stepwise after the first
opening is opened to establish the communication.
[0088] In the vacuum processing method of the present invention,
the at least one of the vacuum processing steps, which is performed
on the article with the pressure-reduced space and the vacuum
processing vessel communicating with each other, may comprise a
deposited film forming step. In this case, the deposited film
forming step as the at least one of the vacuum processing steps may
comprise a step of forming a deposited film having a plurality of
regions different at least in composition. For example, the vacuum
processing steps comprising the deposited film forming step as at
least one step thereof are preferably formation of a deposited film
for producing an electrophotographic photosensitive member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0089] FIG. 1 is a schematic view showing an example of a system
for producing a light-receiving member for electrophotography by
the RF plasma CVD method using the frequency in the RF band (a
vacuum processing system for formation of deposited film);
[0090] FIGS. 2A and 2B are views schematically showing an example
of a system for producing light-receiving members for
electrophotography by the VHF plasma CVD method using the frequency
in the VHF band (a vacuum processing system for formation of
deposited films), in which FIG. 2A is a vertical, sectional view
and FIG. 2B a horizontal, sectional view;
[0091] FIGS. 3A and 3B are views schematically showing another
example of a configuration of a system for producing
light-receiving members for electrophotography by the VHF plasma
CVD method using the frequency in the VHF band, in which FIG. 3A is
a vertical, sectional view and FIG. 3B a horizontal, sectional
view;
[0092] FIG. 4 is a view schematically showing an example of a
vacuum processing system having a movable vacuum processing vessel
and an exhauster;
[0093] FIGS. 5A and 5B are views schematically showing the
principal structure of an example of a vacuum processing vessel of
the movable type, excluding the connection section to the exhaust
section, in which FIG. 5A is a vertical, sectional view and FIG. 5B
a horizontal, sectional view;
[0094] FIG. 6 is a view schematically showing a vacuum processing
system having a plurality of movable vacuum processing vessels and
an exhaust section;
[0095] FIG. 7 is a drawing showing an example of variation of an
exhaust resistance; and
[0096] FIG. 8 is a drawing showing another example of variation of
an exhaust resistance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0097] In the vacuum processing method of the present invention, an
article is loaded in the vacuum processing vessel and the vacuum
processing vessel is evacuated and moved in the pressure-reduced
state. Then, the second opening provided in another
pressure-reduced space different from the vacuum processing vessel
is connected to the first opening provided in the vacuum processing
vessel thus moved. This first opening is of openable/closable
structure and is kept closed during the movement. After completion
of the connection, the first opening is opened whereby the vacuum
processing vessel and the pressure-reduced space different
therefrom are made to communicate with each other under reduced
pressure. At this time, the pressure in the vacuum processing
vessel is set higher than the pressure in the pressure-reduced
space communicating therewith.
[0098] By carrying out the steps of the loading of the article, the
movement of the vacuum processing vessel, and the connection
thereafter as described above, it becomes feasible to effectively
prevent dust from attaching onto the article before vacuum
processing. The loading of article into the vacuum processing
vessel is carried out at a site different from the site where the
vacuum processing itself is carried out, and thereafter the vacuum
processing vessel is moved; this construction allows the system to
maintain the flexibility of production. In addition, the interior
of the vacuum processing vessel is preliminarily pressure-reduced,
which largely decreases the time necessary for bringing the vacuum
processing vessel into a desired pressure-reduced state after the
connection. Accordingly, these successfully accomplish the
effective operation of the vacuum processing system itself or the
decrease of loss in production tact.
[0099] In addition, dust is prevented from attaching onto the
article, so that increase in non-defective percentage of
vacuum-processed articles is also accomplished. Cleanliness of the
article in the step before vacuum processing is maintained with
good repeatability and the exclusion of the factors to cause
degradation of the vacuum processing characteristics is also
achieved with high certainty during vacuum processing; therefore,
it becomes feasible to achieve suppression of variability in the
vacuum processing characteristics among lots.
[0100] The action and construction of the present invention will be
detailed below.
[0101] In the vacuum processing method of the present invention,
the interior of the vacuum processing vessel is preliminarily
evacuated prior to the movement of the vacuum processing vessel so
that the pressure therein becomes a reduced pressure. By
maintaining the interior of the vacuum processing vessel under
reduced pressure, dust is prevented from floating in the vacuum
processing vessel even if vibration is encountered during the
movement. Since there is thus no floating dust itself in the vacuum
processing vessel, the dust is prevented surer from attaching onto
the article, for example, onto a substrate. This results in greatly
reducing defects of the vacuum processing characteristics due to
the dust attaching onto the article, which achieves increase in
non-defective percentage.
[0102] In addition, in the vacuum processing method of the present
invention, as well as the above-stated point that the interior of
the vacuum processing vessel is pressure-reduced during the
movement of the vacuum processing vessel, the pressure inside the
vacuum processing vessel is set higher than the pressure in the
pressure-reduced space to be connected with the vacuum processing
vessel after the movement. This provision of the difference between
the internal pressures improves the vacuum processing
characteristics and also decreases the variability in the vacuum
processing characteristics among lots. Although the inventors
haven't completely elucidated the mechanism for achieving this
effect yet, we speculate that it is achieved according to the
mechanism schematically described below, based on the research
conducted toward completion of the present invention.
[0103] For example, in the vacuum processing method using the
vacuum processing system wherein the reaction vessel and exhauster
are of the separable structure, the article after completion of
vacuum processing is taken out of the reaction vessel disconnected
from the exhauster, after the vacuum processing. After that, where
the interior of the reaction vessel is contaminated with execution
of vacuum processing, the interior of the vessel and others are
cleaned by cleaning means such as dry etching, wet etching, etc.
according to the degree of contamination at a point of time after
vacuum processing for every lot or after a predetermined number of
vacuum processes. Therefore, it is feasible to maintain the
interior of the reaction vessel in desired cleanliness.
[0104] On the other hand, concerning the exhauster connected to the
reaction vessel, maintenance thereof is carried out at need. As a
part of the maintenance, cleaning or the like of the interior is
carried out at regular intervals. However, the frequency of the
cleaning of the interior in the exhauster is much smaller than the
frequency of the cleaning of the interior of the reaction vessel.
Accordingly, with increase in the number of processes, by-products
and the like produced during the vacuum processing will be
accumulated therein and cleanliness levels inside the exhauster
will become heavily different between immediately after maintenance
and immediately before next maintenance.
[0105] When the reaction vessel with a clean article being placed
therein is connected to the exhauster with accumulated
contamination therein to communicate therewith, if the internal
pressure of the exhauster were higher than the internal pressure of
the reaction vessel the gas would flow from the exhauster to the
reaction vessel immediately after the connection. With this gas
flow, the contaminants accumulated inside the exhauster would also
flow more or less from the exhauster to the reaction vessel. If the
contaminants flowing back from the exhauster should attach the
clean article they could be the cause of inducing deficiencies of
the vacuum processing characteristics.
[0106] As another possibility, the by-products and the like
entering the interior of the reaction vessel are decomposed and
activated by the energy guided into the reaction vessel during
vacuum processing, e.g., by heat, by high frequency power, or by
energy of plasma used during vacuum processing, to be absorbed as
impurities into the surface of the vacuum-processed article. As a
consequence, they could be the cause of inducing degradation of the
vacuum processing characteristics.
[0107] In addition, since the amount of the aforementioned
contaminants flowing back from the exhauster is dependent upon the
degree of contamination accumulated inside the exhauster, the
amount will tend to increase with increase in the number of
processes. Therefore, the amount of mixed impurities is not
constant from lot to lot and thus there are variability in the
amount of impurities among processing lots. This would result in
characteristic variability among vacuum processing lots.
Particularly, in the case wherein the exhauster is shared and a
plurality of reaction vessels are alternately used, the total
number of processes will be large and the variability will become
larger. In addition, in the case wherein the common exhauster is
used for a variety of vacuum processes, the difference among the
vacuum processes will often cause much larger variability.
[0108] In addition to the above-stated direct influence, indirect
influence can also be encountered. For example, the by-products and
the like entering the interior of the reaction vessel can also be
decomposed and activated by the energy guided into the reaction
vessel during vacuum processing, e.g., by heat, by high frequency
power, or by energy of plasma used during vacuum processing, to be
accumulated on the internal wall of the reaction vessel and on the
components in the reaction vessel, e.g., on the surfaces of the
electrodes, gas inlet tubes, etc. or to modify these surfaces. Most
of these contaminants remaining in the reaction vessel can be
cleaned by cleaning after vacuum processing, but it is not always
easy in certain cases to restore the reaction vessel into the
initial state, depending upon the types of by-products, and/or the
materials of the internal wall of the reaction vessel and the
components in the reaction vessel. When the complete removal is
hard as in these cases, the surface conditions and compositions of
the internal wall of the reaction vessel and the components in the
reaction vessel can vary with a lapse of time and it can also
result in change in the vacuum processing characteristics with a
lapse of time.
[0109] In contrast with it, since the vacuum processing method of
the present invention utilizes the vacuum processing vessel having
the first openable/closable opening, it is feasible to maintain the
interior of this vacuum processing vessel in desired cleanliness by
the cleaning means of dry etching, wet etching, or the like optimal
for the details of vacuum processing at a point of time after
vacuum processing for every processing lot or after a predetermined
number of vacuum processes.
[0110] The vacuum processing method of the present invention also
makes use of the pressure-reduced space different from the vacuum
processing vessel, e.g., the exhauster or the like, which is made
to communicate with the vacuum processing vessel. Inside this
different pressure-reduced space, e.g., inside the exhauster, the
contaminants such as the by-products and the like produced and the
vacuum processing will have been accumulated, because a plurality
of vacuum processing vessels will be connected in succession to
perform vacuum processing. Accordingly, the cleanliness inside the
different pressure-reduced space, for example, inside the exhauster
is inferior to that inside the vacuum processing vessels subjected
to maintenance thereof.
[0111] If during the movement of the vacuum processing vessel the
pressure in the vacuum processing vessel is lower than the pressure
inside the different pressure-reduced space, e.g., inside the
exhauster to be connected after the movement, the by-products and
the like of vacuum processing accumulated inside the different
pressure-reduced space, e.g., inside the exhauster communicating
with the vacuum processing vessel will readily enter the interior
of the vacuum processing vessel through the first opening. Since in
the method of the present invention the pressure in the vacuum
processing vessel is set higher than the pressure inside the
different pressure-reduced space, e.g., inside the exhauster to be
made to communicate therewith, the gas flow caused by the
difference between the internal pressures is directed from the
vacuum processing vessel toward the different pressure-reduced
space, e.g., toward the exhauster upon establishment of the
communication. This flow caused by the difference between the
internal pressures effectively acts to prevent the phenomenon that
the by-products and the like of vacuum processing accumulated
inside the separate pressure-reduced space, e.g., inside the
exhauster enter the interior of the vacuum processing vessel.
[0112] Although the interior of the vacuum processing vessel itself
is normally maintained in desired cleanliness, a small amount of
remaining dust can be scattered because of fine mechanical
vibration or the like occurring inevitably during the movement. As
another possibility, particles, films, etc. of the by-products of
vacuum processing, which adhere relatively stably to the internal
wall surface and the like without great mechanical vibration, can
also be peeled off and scattered by mechanical vibration caused
accidentally during the movement. Since in the method of the
present invention the movement and connection are carried out while
keeping the interior of the vacuum processing vessel itself under
reduced pressure, the accident of fine dust floating in the vessel
can be avoided even with occurrence of peeling. Therefore, the
method of the invention can prevent the particles and films of the
by-products of vacuum processing, remaining in small amount on the
internal wall of the vacuum processing vessel itself and the like,
from floating and attaching onto the clean article placed
therein.
[0113] In the present invention, the interior of the vacuum
processing vessel is maintained under reduced pressure during the
movement thereof to prevent the dust from attaching onto the
article (e.g., a substrate to be subjected to vacuum processing)
and this action can be made surer by setting the pressure during
the movement of the vacuum processing vessel preferably to not more
than 1.times.10.sup.3 Pa and more preferably to not more than
1.times.10.sup.2 Pa. When the internal pressure is set in this
range, the pressure inside the vacuum processing vessel also needs
to be set higher than the pressure in the different
pressure-reduced space to be connected after the movement.
[0114] On the other hand, there are no specific restrictions on the
lower limit of the pressure in the vacuum processing vessel as long
as the pressure in the vacuum processing vessel is set in the range
higher than the vacuum (pressure) achieved in the different
pressure-reduced space to be connected after the movement. From the
aspect of providing the pressure difference described below, it is
desirable to set the pressure inside the vacuum processing vessel
preferably to not less than 0.1 Pa and more preferably to not less
than 1 Pa. If during reduction of pressure inside the vacuum
processing vessel a vacuum degree higher than necessary is selected
as the pressure (vacuum) therein, an evacuation time necessary for
arrival at the selected high vacuum will become longer and thus it
can be a new factor of degrading workability.
[0115] In addition, during the movement of the vacuum processing
vessel the interior of the vacuum processing vessel is preferably
filled with a desired gas under a predetermined reduced pressure.
For example, the interior of the vacuum processing vessel is
evacuated once to a pressure sufficiently lower than the
predetermined pressure (vacuum), and thereafter the desired gas is
introduced to be filled under the predetermined pressure (vacuum).
Alternatively, the atmosphere in the vacuum processing vessel is
preliminarily replaced with the desired gas and thereafter the
pressure is reduced to the predetermined pressure (vacuum) so as to
fill the vessel with the gas. The filling gas contains little
water, different from the atmosphere, so as to promote evaporation
of water adsorbing to the wall surface of the vacuum processing
vessel and the like thus more effectively achieve the evaporative
removal of water adsorbing to the wall surface and the like during
the movement of the vacuum processing vessel. After that, the
vacuum processing vessel is connected to the exhaust section and
the desired gas filled therein is evacuated to expel the
evaporatively removed water to the outside of the vacuum processing
vessel system, whereby the water remaining inside is reduced prior
to execution of vacuum processing, so as to greatly relieve the
influence of the remaining water on the vacuum processing. The
desired gas to be filled for the above purpose is a gas having a
low water content, the selected gas itself not producing a film
attaching on the internal wall surface of the vacuum processing
vessel and the like and not causing corrosion of the internal wall
surface of the vacuum processing vessel and the like, either.
Specifically, the filling gas can be preferably selected from the
inert gases such as Ar, He, Ne, Xe, and Kr, or H.sub.2, N.sub.2,
and so on, which are easy to handle.
[0116] In the method of the present invention, the internal
pressure difference, which is utilized in preventing the
by-products and the like of vacuum processing from the different
pressure-reduced space from mixing into the vacuum processing
vessel, is preferably determined so that the pressure P1 (Pa)
during the movement of the vacuum processing vessel and the
pressure P2 (Pa) of the different pressure-reduced space to be
connected after the movement satisfy the following relation:
P1-P2.gtoreq.0.1 Pa;
[0117] further, the internal pressure difference is more preferably
set larger so that the pressures P1 and P2 satisfy the following
relation:
P1-P2.gtoreq.1 Pa.
[0118] This internal pressure difference is determined with the
intention of forming a weak gas flow from the vacuum processing
vessel toward the different pressure-reduced space, e.g., toward
the exhauster and thus makes it feasible to prevent the migration
of the by-products and the like of vacuum processing from the
different pressure-reduced space, e.g., from the exhauster into the
vacuum processing vessel, which readily occurs particularly
immediately after opening of the first opening.
[0119] The problem avoided by the action of the present invention
described above is the problem intrinsic to the vacuum processing
in which the vacuum processing vessel is movable, the vacuum
processing vessel is moved with the article being placed therein,
the first opening is connected to the second opening provided in a
communicable state in the pressure-reduced space different from
this vacuum processing vessel, and thereafter the first opening is
opened to carry out at least one step of the vacuum processing
steps. For example, in the system illustrated in FIG. 4 in which
the vacuum vessel and exhauster are of the separable structure, the
problem solved by the present invention will not appear noticeable
if the vacuum processing is carried out in the state in which the
movable reaction vessel section 501 is always connected to the
exhaust section 502. Namely, during the period in which the
reaction vessel and exhauster are always connected, the step of
cleaning the interior of the reaction vessel 506 by dry etching or
the like is carried out at stages where the cleanliness in the
reaction vessel 506 becomes below a desired level. During this
cleaning step, the interior of the exhaust pipe of the exhaust
section 502 is also cleaned by etching gas or active species
thereof, at the same time as the cleaning of the interior of the
reaction vessel 506. As a result, the cleanliness in the exhaust
pipe of the exhaust section 502 also recovers at the same frequency
as the reaction vessel 506. Accordingly, the by-products and the
like of vacuum processing are inherently not accumulated in the
exhaust pipe of the exhaust section 502 and thus the migration of
the by-products of vacuum processing into the reaction vessel as
described above is originally suppressed to a very small
amount.
[0120] On the other hand, the vacuum processing method of the
present invention exhibits the prominent effect, for example, when
favorably utilized in alternately and incessantly carrying out
vacuum processing in such a manner that a plurality of vacuum
processing vessels are prepared, a vacuum processing vessel is
moved with an article being placed therein, the vacuum processing
vessel is connected to a pressure-reduced space different
therefrom, and thereafter at least one step of vacuum processing
steps is carried out. Namely, the vacuum processing method of the
present invention presents the outstanding effect particularly in
the case of use of the common pressure-reduced space (e.g., exhaust
means) to a plurality of vacuum processing vessels, applicable to
processing with flexibility; therefore, the method can effectively
suppress the migration of the impurities such as the dust produced
during the movement of the vacuum processing vessel and the
by-products of vacuum processing into the vacuum processing vessel
and also suppress the degradation of the vacuum processing
characteristics and the variability in the vacuum processing
characteristics among lots.
[0121] It can be speculated that the migration of the dust and
impurities into the vacuum processing vessel can be also suppressed
to some extent by methods other than the approach of the present
invention, for example, by such a modification of the system
illustrated in FIG. 4 that the length of the pipe is set long
between the first opening 504 provided in the vacuum processing
vessel 501 and the main body 506 of the vacuum processing vessel.
However, when the pipe length is set long between the main body of
the vacuum processing vessel and the first opening, the entire
apparatus of the vacuum processing vessel 501 becomes larger. For
this reason, the movement of the movable reaction vessel section
501 becomes hard, operability of replacement and mounting works
becomes worse, and productivity can be lowered in certain cases.
The method of the present invention makes it feasible to present
the above effect without causing the increase in the scale of the
apparatus, the deterioration of workability and operability, or the
drop of productivity.
[0122] In the vacuum processing method of the present invention, a
more outstanding effect can be achieved by carrying out an
operation of, after opening the first opening to establish the
communication, varying the exhaust resistance between the vacuum
processing vessel and the different pressure-reduced space provided
with the second opening. This variation of the exhaust resistance
controls the flow of gas from the vacuum processing vessel toward
the second opening, thereby suppressing occurrence of rapid gas
flow. As a result, it becomes feasible to more effectively suppress
the floating of dust in the vacuum processing vessel or the
migration of the floating by-products and the like of vacuum
processing into the vacuum processing vessel, which can be readily
caused by the rapid gas flow. This operation of changing the
exhaust resistance is preferably control of continuously and/or
stepwise reducing the exhaust resistance between the vacuum
processing vessel and the different pressure-reduced space provided
with the second opening. Namely, when the difference between the
pressure in the vacuum processing vessel and the pressure in the
different pressure-reduced space, i.e., the internal pressure
difference is relatively large, the exhaust resistance is
maintained high, so as to suppress the rapid flow of gas from the
vacuum processing vessel into the different pressure-reduced space
provided with the second opening. At the stage when the internal
pressure difference is reduced to a relatively small value
thereafter, the exhaust resistance is lowered according to the
decrease of the internal pressure difference. As a result, the
exhaust capability inside the vacuum processing vessel, which is
evacuated via the different pressure-reduced space, is enhanced to
a desired level. By adding this changing operation of exhaust
resistance, it becomes feasible to efficiently perform the exhaust
operation inside the vacuum processing vessel while enjoying the
noticeable effect of the present invention.
[0123] The vacuum processing method of the present invention
demonstrates its effects particularly noticeable when the vacuum
processing includes at least a deposited film forming step. When
the vacuum processing includes the deposited film forming step, a
coating of deposited film, i.e., attachment of by-products occurs,
in addition to the internal wall of the vacuum processing vessel,
near the second opening communicating therewith and also in the
different pressure-reduced space provided with the second opening.
The by-products and the like adhering and accumulated readily
produce flakes because of peeling and thus migrate as dust and
impurities into the vacuum processing vessel. Since the vacuum
processing method of the present invention effectively suppresses
the phenomenon that the by-products and the like accumulated near
the second opening and in the different pressure-reduced space
provided with the second opening migrate as dust and impurities
into the vacuum processing vessel, its effects become noticeable
particularly in the vacuum processing including the deposited film
forming step.
[0124] When the vacuum processing includes a step of forming
deposited films having a plurality of regions of different
compositions among those of forming deposited films, the method of
the present invention becomes more effective. For example, in the
case of the vacuum processing of forming two layers of different m
compositions, with progress of the vacuum processing step, the
by-products produced during formation of the first layer and the
by-products produced during formation of the second layer are
successively deposited near the second opening or in the
pressure-reduced space provided with the second opening. For the
vacuum processing of the next cycle, the vacuum processing vessel
with a new article being placed therein is connected. On this
occasion, the by-products produced during the previous formation of
the second layer attach near the second opening and on the
outermost surface of the internal wall of the different
pressure-reduced space provided with the second opening and they
are impurities easiest to migrate into the vacuum processing
vessel. If the next formation of the deposited film of the first
layer should be carried out under the situation in which the
by-products produced during the previous formation of the second
layer are in the vacuum processing vessel, since the by-products
produced during the formation of the second layer normally contain
elements different from those in the deposited film of the
objective first layer, the elements would be included as impurities
in the first layer. It can often result in considerable degradation
of the characteristics or variability in the characteristics among
lots. Since the vacuum processing method of the present invention
effectively suppresses the migration of the impurities originating
in the depositions near the second opening and on the internal wall
of the different pressure-reduced space provided with the second
opening, its effects become more noticeable, particularly, when the
vacuum processing includes the step of forming the deposited films
having the plural regions of different compositions.
[0125] Accordingly, the vacuum processing method of the present
invention is particularly effective when the vacuum processing is
formation of deposited films for forming a photosensitive member
for electrophotography. Since the photosensitive member for
electrophotography to be produced is normally constructed utilizing
the structure in which deposited films of different compositions
are stacked, it is a typical example of the aforementioned vacuum
processing including the step of forming the deposited films having
the plural regions of different compositions. In addition, since
the deposited films themselves are normally formed as deposited
films having the total thickness of several ten .mu.m, the amount
of the by-products near the second opening or on the internal wall
of the different pressure-reduced space provided with the second
opening becomes very large per deposition step. As a result, as
described above, the system is in such a state that the dust and
impurities originating in the by-products attaching there are
easier to migrate into the vacuum processing vessel. By applying
the vacuum processing method of the present invention, even in such
cases, the method effectively suppresses the migration of the dust
and impurities into the vacuum processing vessel and the mixing of
the foreign elements into the deposited film along therewith, thus
exhibiting the noticeable effects.
[0126] An embodiment of the vacuum processing method of the present
invention presenting such effects will be described below in more
detail with reference to the drawings.
[0127] FIG. 6 is a schematic view showing an example of vacuum
processing apparatus capable of favorably carrying out the vacuum
processing method of the present invention. This vacuum processing
system of FIG. 6 is constructed in the structure in which an
exhaust section 102 and reaction vessel sections are separable from
each other. In the separated state, the reaction vessel section is
arranged as movable. In FIG. 6, numeral 101 designates a first
movable reaction vessel section, which consists of a reaction
vessel 106, a vacuum seal valve 108, and a connection flange 104
and which is movable. Numeral 102 denotes an exhaust section, which
consists of an exhaust means 107, vacuum seal valves 109, and
connection flanges 105. Numeral 103 represents a connection section
for connection between the reaction vessel section 101 and the
exhaust section 102. Numeral 110 indicates a second movable
reaction vessel section, which has the structure similar to that of
the first movable reaction vessel section 101.
[0128] The first movable reaction vessel section 101 and the second
movable reaction vessel section 110 can be connected each to the
exhaust section 102 at respectively different connection sections.
They can be arranged so that the vacuum processing is carried out
simultaneously and in parallel therein or so that the vacuum
processing is carried out alternately in each of them. The
structure in the reaction vessel 106 is constructed so as to
properly match the purpose of use, according to the objective
vacuum processing. For example, for the purpose of forming
deposited films on plural substrates by the plasma CVD method, the
structure illustrated in FIGS. 5A and 5B can be used, for example.
Numeral 113 denotes an auxiliary exhauster, which is used for
evacuating pipes 115 between the reaction-vessel-side vacuum seal
valve 108 and the exhaust-section-side vacuum seal valve 109 after
the connection of the reaction vessel sections 101 and 110 to the
exhaust section 102. The auxiliary exhauster 113 is arranged to be
able to start or stop the evacuation through valves 111 and 112.
Numeral 114 represents a conductance varying valve, by which the
exhaust resistance can be varied on the occasion of evacuating the
interior of the reaction vessel 106 by the exhaust means 107.
[0129] When in this system as illustrated in FIG. 6 the reaction
vessels 106 are of the structure illustrated in FIGS. 5A and 5B,
the vacuum processing method of the present invention can be
carried out, for example, according to the procedures described
below.
[0130] First, the movable reaction vessel section 101, in the
disconnected state from the exhaust section 102, is connected to an
exhauster for loading of substrate (not shown), by use of the
connection flange 104. In this state, cylindrical substrates 605
are loaded into the reaction vessel 601. Then, the interior of the
reaction vessel 601 is evacuated through the exhaust duct 611
linking to the vacuum seal valve 108, using the substrate-loading
exhauster connected thereto. During execution of this evacuation,
the vacuum seal valve 108 is kept open. The evacuation of the
interior of the reaction vessel 601 is terminated by closing the
vacuum seal valve 108 under such a condition that the pressure
inside the reaction vessel 601 is in a pressure-reduced state and
that, on the occasion of thereafter connecting the reaction vessel
section 101 to the exhaust section 102 and then opening the vacuum
seal valve 108 to establish the communication between them, the
pressure inside the reaction vessel 601 becomes higher than the
pressure on the exhaust section side.
[0131] The exhaust-section-side pressure P2 and the pressure P1 in
the reaction vessel 601 are normally preliminarily selected in such
a range that the pressure difference P1-P2 becomes not less than
the predetermined value and that P1 itself becomes not more than a
predetermined degree of pressure reduction (pressure), on the
occasion of connecting the vacuum vessel section 101 to the exhaust
section 102 and thereafter opening the vacuum seal valve 108 to
establish the communication.
[0132] Alternatively, the reaction vessel section 101 can also be
carried with the reaction vessel 601 being filled with desired gas,
to the exhaust section 102. In this case, the cylindrical
substrates 605 are loaded into the reaction vessel 601 and
thereafter the interior of the reaction vessel 601 is fully
evacuated once through the exhaust duct 611 by the
substrate-loading exhauster. Then, the desired gas is introduced
through the source gas supply means 612 into the reaction vessel
601. On this occasion, it can also be contemplated that the gas is
introduced with the vacuum seal valve 108 being kept in the open
state, the gas is flowed for a desired period, and thereafter the
vacuum seal valve is closed whereby the interior of the reaction
vessel 601 is set in the aforementioned pressure range. As another
approach, the interior of the reaction vessel 601 may also be set
in the aforementioned pressure range by preliminarily closing the
vacuum seal valve 108 after the evacuation and introducing the
desired gas through the source gas supply means 612 into the
reaction vessel 601. In a further applicable method, the gas is
introduced through the source gas supply means 612 into the
reaction vessel 601 to fill the interior of the reaction vessel 601
with the desired gas to a predetermined pressure, thereafter the
vacuum seal valve 108 is again opened to reduce the pressure to a
desired pressure, and then the vacuum seal valve 108 is closed.
[0133] In either case of the above procedures, the pressure inside
the reaction vessel 601 is maintained in the pressure-reduced state
before completion of the movement of the reaction vessel section
101 to the exhaust section 102 and the pressure inside the reaction
vessel 601 is kept in the higher state than the
exhaust-section-side pressure upon opening of the vacuum seal valve
108 after the connection of the reaction vessel section 101 to the
exhaust section 102. Accordingly, the method may also be arranged,
for example, to heat the cylindrical substrates 605 to a
predetermined temperature by the heaters 607 and thereafter carry
out either of the aforementioned procedures to set the interior of
the reaction vessel 601 to the predetermined pressure.
[0134] After the pressure in the reaction vessel 601 reaches the
predetermined value and the vacuum seal valve 108 is then closed,
the connection flange 104 is disconnected from the
substrate-loading exhauster. Then, the movable reaction vessel
section 101 is moved to the installation site of the exhaust
section 102 and the connection flange 104 is connected through a
vacuum seal material to the exhaust-section-side connection flange
105.
[0135] After the connection, in order to make the connection
section airtight, the flanges are fixed to each other, using such
fixing means as screws, clamps, or the like provided at need in the
apparatus per se. After it is confirmed that the movable reaction
vessel section 101 is connected to the exhaust section 102, the
pipes 115 between the exhaust-section-side vacuum seal valve 109
and the reaction-vessel-side vacuum seal valve 108 are evacuated. A
specific evacuation procedure may be a method of opening the valve
112 to evacuate the pipes to a predetermined pressure by the
auxiliary exhauster 113, or a method of roughly reducing the
pressure by the auxiliary exhauster 113 and thereafter opening the
exhaust-section-side vacuum seal valve 109 to evacuate the pipes by
the exhaust means 107. The evacuation decreases the pressure inside
the pipes 115 to below the pressure inside the reaction vessel 601
and the evacuation is switched to that by the exhaust means 107.
After it is confirmed that the pressure is lowered to a
predetermined exhaust-section-side pressure, the
reaction-vessel-side vacuum seal valve 108 is opened.
[0136] Accordingly, in the case wherein the evacuation of the pipes
115 between the exhaust-section-side vacuum seal valve 109 and the
reaction-vessel-side vacuum seal valve 108 is carried out by the
auxiliary exhauster 113, the valve 112 is closed and the
exhaust-section-side vacuum seal valve 109 is opened. On the
occasion of opening the exhaust-section-side vacuum seal valve 109,
the pressure on the exhaust means 107 side is preferably set lower
than the pressure in the part of pipes 115. For selecting a
procedure of opening the vacuum seal valve 109 at the stage when
there is no difference between them or when the pressure in the
part of pipes 115 is lower, the exhaust pipe is constructed in so
long length between the exhaust-section-side vacuum seal valve 109
and the connection flange 105 that the dust and impurities flying
from the exhaust means 107 are prevented from migrating over the
joint part, for example, up to the position of the
reaction-vessel-side vacuum seal valve 108. The migration of the
dust and impurities into the reaction vessel 106 can be prevented
surer by also employing the procedure and the configuration of the
exhaust section 102 for suppressing the back flow of the dust and
impurities from the exhaust section side toward the reaction vessel
on the occasion of opening the exhaust-section-side vacuum seal
valve 109.
[0137] On the occasion of opening the exhaust-section-side vacuum
seal valve 109, the conductance varying valve 114 is preferably
controlled so that the exhaust resistance is high in the initial
stage of evacuation and then the exhaust resistance is gradually
decreased, from the aspect of preventing the rapid gas flow.
Likewise, on the occasion of opening the reaction-vessel-side
vacuum seal valve 108, the conductance varying valve 114 is also
preferably controlled so that the exhaust resistance is high in the
initial stage of evacuation and then the exhaust resistance is
gradually lowered, from the aspect of preventing the rapid gas
flow.
[0138] After completion of the above preparation, the vacuum
processing steps are initiated. For example, when the vacuum
processing is a process of preparing a cylindrical substrate as an
article and forming a deposited film on this substrate by the
plasma CVD method, the vacuum processing steps can be carried out
according to the procedures described below, in the structure of
the reaction vessel 106 as illustrated in FIG. 6.
[0139] After completion of the connection and communication
operation between the movable reaction vessel section 101 and the
exhaust section 102, substrates are placed in the reaction vessel
106 and the interior of the reaction vessel 106 is in the evacuated
state by the exhaust means 107. In this state, the cylindrical
substrates 605 are heated and controlled to a predetermined
temperature by the heaters 607. When the cylindrical substrates 605
reach the predetermined temperature, the source gas is introduced
through the source gas supply means 612 into the reaction vessel
601. After the flow rate of the source gas reaches a set flow rate,
the exhaust resistance of the conductance varying valve 114 is
adjusted to set the pressure in the reaction vessel 601 to a
predetermined value. After it is confirmed that the source gas flow
rate and the pressure become stable at their respective values by
this adjustment operation, the predetermined high frequency power
is supplied from the high frequency power supplies 603 and 614
through the respective matching boxes 604, 613 to the cathode
electrodes 602, 606. The high frequency power thus supplied brings
about glow discharge in the reaction vessel 601 to excite and
dissociate the source gas, thereby forming deposited films on the
cylindrical substrates 605. After the deposited films are formed in
desired thickness, the supply of a high frequency power is
terminated and then the supply of source gas is also terminated,
thereby completing the formation of first deposited films.
[0140] The series of operations described above are carried out
several times by selecting deposition conditions according to
objective deposited films, thereby forming the multi-layer
deposited films used in the photosensitive members for
electrophotography consisting of a plurality of layers. Between
layers, the operations may also be carried out in such a manner
that the discharge is once stopped completely at the time of
completion of formation of one layer, the setting of the gas flow
rate and pressure is modified according to the deposition
conditions of a next layer, and thereafter discharge is again
induced for formation of the next layer. In another applicable
method, the multiple layers may be continuously formed by gradually
changing the set values of the gas flow rate, pressure, and high
frequency power within a fixed period according to the deposition
conditions of the next layer without interruption after completion
of formation of one layer. During the formation of the deposited
films, the cylindrical substrates 605 may be rotated at a
predetermined speed at need through the rotation shafts 608 by the
motors 609.
[0141] After completion of the deposited film forming step in this
way, the source gas in the reaction vessel 106 and in the exhaust
pipes are fully purged or preferably replaced with inert gas. Then,
the reaction-vessel-side vacuum seal valve 108 and the
exhaust-section-side valve 109 are closed. After that, the part
between the exhaust-section-side vacuum seal valve 109 and the
reaction-vessel-side vacuum seal valve 108, i.e., the part of pipes
115 is opened to the atmosphere and the connection section 103 is
disconnected. After disconnected, the movable reaction vessel
section 101 becomes movable and then the movable reaction vessel
section 101 is moved to the substrate unloading site.
[0142] As the need arises, the substrates 605 are cooled to a
desired temperature and then the inert gas or the like is
introduced through the unrepresented leak valve into the reaction
vessel 106, thereby returning the internal pressure of the reaction
vessel 106 to the atmospheric pressure. After the interior of the
reaction vessel 106 reaches the atmospheric pressure, the
substrates 605 with the deposited films thereon are taken out of
the reaction vessel 106.
[0143] After that, the components in the reaction vessel 106 are
subjected to replacement, cleaning, etc., whereby the reaction
vessel 106 is recovered into the state permitting the formation of
deposited films. For the next vacuum processing, the reaction
vessel 106 is again transferred to the above-stated substrate
loading process.
[0144] In the series of vacuum processing steps as described above,
the vacuum processing can be carried out more efficiently by
provision of a plurality of movable reaction vessel sections and,
for example, by simultaneous and parallel execution of vacuum
processing in the reaction vessel section 101 and in the reaction
vessel section 110. In another applicable method, at the stage when
the reaction vessel section 101 is disconnected from the exhaust
section 102 after completion of the formation of deposited films in
the reaction vessel section 101 connected to the exhaust section
102, the reaction vessel section 110 is connected to the exhaust
section 102 and the formation of deposited films is then carried
out in similar fashion.
[0145] In the process of using both the reaction vessel section 101
and the reaction vessel section 110 and sequentially carrying out
the vacuum processing steps therein, for example, during the period
in which the exhaust-section-side vacuum seal valve 109
communicating with one reaction vessel section 101 is opened, the
exhaust-section-side vacuum seal valve communicating with the other
reaction vessel section 110 is kept in the closed state.
EXAMPLES
[0146] The present invention will be described below in further
detail with examples thereof. It is noted that these examples are
intended to provide examples of best embodied forms of the present
invention but the present invention is by no means intended to be
limited to these examples.
Example 1
[0147] Deposited films were formed on cylindrical substrates,
specifically, on cylindrical aluminum cylinders 605 having the
diameter of 80 mm and the length of 358 mm, by the plasma CVD
method, using the vacuum processing system illustrated in FIG. 6
and using the reaction vessels for production of photosensitive
members for electrophotography, illustrated in FIGS. 5A and 5B, as
the reaction vessels 106. The a-Si deposited films were formed
under the deposition conditions presented in Table 1, while setting
the oscillation frequency of the high frequency power supplies 603
and 614 to 100 MHz. In Table 1, the power indicates the total of
the powers supplied from the high frequency power supply 603 and
from the high frequency power supply 614. For the purpose of use in
evaluation of film quality of the deposited films, particularly,
for use in evaluation of the electric characteristics, a Corning
#7059 glass substrate having a comb-shaped electrode of Cr with
gaps of 250 .mu.m evaporated thereon was placed as an electric
characteristic evaluating substrate in the axial center on the
surface of each of the six cylindrical substrates. The cathode
electrodes 602, 606 were SUS cylinders having the diameter of 20 mm
and constructed in structure where the outside was covered by an
alumina pipe having the inside diameter of 21 mm and the outside
diameter of 24 mm. The alumina pipes were processed by blasting so
that the surface roughness thereof, Rz, was 20 .mu.m on the basis
of the reference length of 2.5 mm.
[0148] The source gas supply means 612 were alumina pipes having
the inside diameter of 10 mm and the outside diameter of 13 mm and
were constructed in such structure that their ends were sealed and
a lot of gas outlets having the diameter of 1.2 mm were provided on
the pipes so as to be able to uniformly supply the source gas in
the circumferential direction. The surfaces of the source gas
supply means 612 were also processed by blasting so that the
surface roughness thereof, Rz, was 20 .mu.m on the basis of the
reference length of 2.5 mm.
[0149] The deposited film forming steps were carried out according
to the procedures schematically described below, using the
deposited film forming apparatus described above.
[0150] First, the movable reaction vessel sections 101, 110 were
connected through their connection flanges 104 to the
substrate-loading exhauster (not shown), and at the same time, Ar
supplying pipes (not shown), and power supply lines to the reaction
vessel sections 101, 110 were also connected. In this state, the
cylindrical substrates 605 were loaded into each reaction vessel
601 (106). Then, the vacuum seal valve 108 was opened to evacuate
the interior of the reaction vessel 601 through the exhaust duct
611 by the substrate-loading exhauster. After confirming that the
interior of the reaction vessel 601 (106) was evacuated to below
1.times.10.sup.-3 Pa, Ar was supplied at the flow rate of 500 sccm
through the source gas supply means 612 into the reaction vessel
601 (106). While the pressure in the reaction vessel was maintained
at 70 Pa by an unrepresented pressure regulating valve, the
cylindrical substrates 605 were heated and controlled to
250.degree. C. by the heaters 607. The heating state of the
substrates under this pressure-reduced Ar atmosphere was maintained
for two hours. During this period the cylindrical substrates 605
were rotated at the speed of 10 rpm via the rotation shafts 608 and
gears 610 by the motors 609. During the Ar supply start period the
flow rate of Ar was linearly increased from 0 sccm to 500 sccm in 5
minutes.
[0151] Then, the supply of Ar was stopped, and at the time when the
internal pressure of the reaction vessel 601 (106) became 60 Pa,
the vacuum seal valve 108 was closed and the heating of the
substrates 605 by the heaters 607 was terminated. After that, the
connection flange 104 was disconnected from the substrate-loading
exhauster, and the Ar supplying pipe (not shown) connected to the
source gas supply means 612, and the power supply lines to the
reaction vessel 601 were also disconnected. By the above operation,
the interior of the movable reaction vessel sections 101, 110 was
filled with Ar gas and maintained in the pressure-reduced state of
the internal pressure of 60 Pa.
[0152] After the above operation, the movable reaction vessel
sections 101 and 110 were moved to the installation site of the
exhaust section 102 and their connection flanges 104 were connected
through a Viton O-ring (vacuum seal) to the exhaust-side connection
flanges 105. After that, the connection sections 103 were fixed by
clamps. The source gas supply pipes (not shown) were connected to
the source gas supply means 612, and the power supply lines and
high frequency power supply cables were further connected to the
reaction vessel sections 101 and 110.
[0153] After completion of these connection operations, the
exhaust-side vacuum seal valves 109 were first opened to evacuate
the interior of the pipes 115 by the exhaust means 107. When the
pressure in the pipes 115 reached 6 Pa, the reaction-vessel-side
vacuum seal valves 108 were opened to evacuate the interior of the
reaction vessels 106 to below 1.times.10.sup.-3 Pa. On this
occasion, the conductance varying valves 114 were kept in the full
open state.
[0154] In the next place, while the cylindrical substrates 605 were
rotated at the speed of 10 rpm via the rotation shafts 608 and
gears 610 by the motors 609, Ar was supplied at the flow rate of
500 sccm through the source gas supply means 612 into the reaction
vessels 601 and the pressure in the reaction vessels was adjusted
to 70 Pa by the conductance varying valves 114. While the internal
pressure was maintained in the reduced pressure of 70 Pa, the
cylindrical substrates 605 were again heated and controlled to
250.degree. C. by the heaters 607 and that state was maintained for
20 minutes. During the Ar supply start period, the flow rate of Ar
was linearly increased from 0 sccm to 500 sccm in 5 minutes.
[0155] After that, the supply of Ar was stopped and the source gas
under the condition presented in Table 1 was introduced through the
source gas supply means 612. After the flow rate of the source gas
reached the set flow rate, the conductance varying valves 114 were
adjusted to set the pressure in the reaction vessels to the
condition of Table 1. After confirming that the pressure in the
reaction vessels 601 (106) became stable, the total output of the
high frequency power supplies 603 and 614 was set to the power
presented in Table 1 and the high frequency power was supplied
through the matching boxes 604 and 613 to the cathode electrodes
602 and 606. The high frequency power radiated from the cathode
electrodes 602 and 606 into the reaction vessels 601 (106) induced
plasma discharge to excite and dissociate the source gas, thereby
depositing the a-Si deposited films on the cylindrical substrates
605. After that, the supply of the high frequency power was
terminated when the deposited films had the thickness of 1 .mu.m.
Then, the supply of the source gas was terminated to end the
formation of deposited films. (The end of deposition can be
determined, for example, by monitoring the thickness of the
deposited films and defining the end at a desired thickness, 1
.mu.m herein, or by preliminarily measuring a deposition rate per
unit time and defining the end at a deposition forming time
corresponding to a desired thickness.)
[0156] After completion of the deposited film forming step in this
way, the source gas inside the reaction vessels 601 (106) and in
the source gas supply pipes was fully purged and then the vacuum
seal valves 108 and 109 were closed. Then, He was introduced into
the reaction vessels 601 (106) thus hermetically closed, up to the
internal pressure of 1000 Pa. After that, the connection sections
103 were disconnected and the source gas supply pipes, power supply
lines, and high frequency power supply cables were also
disconnected, thus bringing the reaction vessel sections 101 and
110 into the movable state.
[0157] Then, the reaction vessel sections 101 and 110 were moved to
the substrate unloading site and the substrates 605 were cooled to
room temperature. Then, nitrogen was introduced through the
unrepresented leak valves into the reaction vessels 601 (106)
before the interior of the reaction vessels 601 (106) reached the
atmospheric pressure. After the interior of the reaction vessels
601 (106) reached the atmospheric pressure, the substrates 605 with
the deposited films thereon were taken out of the interior of the
reaction vessels 601 (106).
[0158] After that, the reaction vessels 601 (106) after completion
of the series of a-Si deposited film forming steps were restored by
exchange of the internal components thereof whereby the reaction
vessels 601 (106) were again brought into the deposition film
formable state.
[0159] Five lots of a-Si deposited films were formed under the
conditions presented in Table 1 as described above, thereby
obtaining totally sixty samples for evaluation of the electric
characteristics.
Comparative Example 1
[0160] The a-Si deposited films were made under the conditions
presented in Table 1 in much the same manner as in Example 1 except
that, after the connection between the reaction vessel sections 101
and 110 and the exhaust section 102, the exhaust-side vacuum seal
valves 109 were opened to evacuate the interior of the pipes by the
exhaust means 107 and the reaction-vessel-side vacuum seal valves
108 were then opened at the point when the pressure in the pipes
115 became 600 Pa. In this Comparative Example 1, five lots of
deposited films were formed, thereby obtaining totally sixty
samples for evaluation of electric characteristics.
[0161] The electric characteristic evaluating samples obtained in
Example 1 and Comparative Example 1 were evaluated as follows and
their characteristics were compared with each other.
[0162] (Evaluation of Density-of-states)
[0163] The density-of-states was measured in the range from the
valence band edge to 0.8 eV above the valence band edge (on the
conduction band side) by CPM (Constant Photocurrent Method).
Therefore, the smaller the value of density-of-states, the better
the characteristics of deposited film.
[0164] From the results of the evaluation of density-of-states, the
sixty electric characteristic evaluating samples obtained in
Example 1 all were able to be evaluated, whereas seven out of the
sixty electric characteristic evaluating samples obtained in
Comparative Example 1 were unable to be evaluated. For the seven
samples that were unable to be evaluated, their deposited films
were observed with an optical microscope and it was found that
contamination adhered to the gap portions of the comb-shaped
electrodes.
[0165] Concerning the density-of-states of the evaluable samples,
the average density-of-states of Comparative Example 1 was three
times greater than that of Example 1. Concerning variability of
density-of-states among the samples, Comparative Example 1
demonstrated greater variability.
[0166] It was verified from the above comparison results that
application of the vacuum processing method of the present
invention presented the effect of suppressing the dust attachment
to the vacuum-processed articles and the effect of improvement in
the vacuum processing characteristics.
1 TABLE 1 Gas species and flow rate SiH.sub.4: 500 sccm Substrate
temperature 250.degree. C. Internal pressure of 1.3 Pa reaction
vessel High frequency power 800 W Film thickness 1 .mu.m
Example 2
[0167] Deposited films were formed on cylindrical substrates,
specifically, on cylindrical aluminum cylinders 605 having the
diameter of 80 mm and the length of 358 mm, by the plasma CVD
method, using the vacuum processing system illustrated in FIG. 6
and using the reaction vessels for production of photosensitive
members for electrophotography, illustrated in FIGS. 5A and 5B, as
the reaction vessels 106. The a-Si based deposited films
(photosensitive members) were formed under the deposition
conditions presented in Table 2, while setting the oscillation
frequency of the high frequency power supplies 603 and 614 to 100
MHz. In Table 2, the power indicates the total of the powers
supplied from the high frequency power supply 603 and from the high
frequency power supply 614. The cathode electrodes 602, 606 were
SUS cylinders having the diameter of 20 mm and constructed in
structure where the outside was covered by an alumina pipe having
the inside diameter of 21 mm and the outside diameter of 24 mm. The
alumina pipes were processed by blasting so that the surface
roughness thereof, Rz, was 20 .mu.m on the basis of the reference
length of 2.5 mm.
[0168] The source gas supply means 612 were alumina pipes having
the inside diameter of 10 mm and the outside diameter of 13 mm and
were constructed in such structure that their ends were sealed and
a lot of gas outlets having the diameter of 1.2 mm were provided on
the pipes so as to be able to uniformly supply the source gas in
the circumferential direction. The surfaces of the source gas
supply means 612 were also processed by blasting so that the
surface roughness thereof, Rz, was 20 .mu.m on the basis of the
reference length of 2.5 mm.
[0169] The deposited film forming steps were carried out according
to the procedures schematically described below, using the
deposited film forming apparatus described above. In the present
example, the deposited films consisting of a charge injection
blocking layer, a photoconductive layer, and a surface layer were
sequentially formed under the deposition conditions presented in
Table 2.
[0170] First, the movable reaction vessel sections 101, 110 were
connected through their connection flanges 104 to the
substrate-loading exhauster (not shown), and the Ar supplying pipes
(not shown), and the power supply lines to the reaction vessel
sections 101, 110 were also connected. In this state, the
cylindrical substrates 605 were loaded into the reaction vessels
601 (106). Then, each vacuum seal valve 108 was opened to evacuate
the interior of the reaction vessel 601 through the exhaust duct
611 by the substrate-loading exhauster. After confirming that the
interior of the reaction vessels 601 (106) was evacuated to below
1.times.10.sup.-3 Pa, Ar was supplied at the flow rate of 500 sccm
through the source gas supply means 612 into the reaction vessels
601 (106). While the pressure in the reaction vessels was
maintained at 70 Pa by the unrepresented pressure regulating
valves, the cylindrical substrates 605 were heated and controlled
to 250.degree. C. by the heaters 607. The heating state of the
substrates under this pressure-reduced Ar atmosphere was maintained
for two hours. During this period the cylindrical substrates 605
were rotated at the speed of 10 rpm via the rotation shafts 608 and
gears 610 by the motors 609. During the Ar supply start period the
flow rate of Ar was linearly increased from 0 sccm to 500 sccm in 5
minutes.
[0171] Next, the vacuum seal valves 108 were closed, the supply of
Ar was stopped, and the reaction vessels 601 (106) were
hermetically sealed in the pressure-reduced state. On that
occasion, the interior of the reaction vessels 601 (106) was
hermetically sealed under the pressure-reduced conditions below by
adjusting the closing timing of the vacuum seal valves 108 and the
stopping timing of the Ar supply, and thereafter the heating of the
substrates 605 by the heaters 607 was terminated. The pressure in
the reaction vessels 601 (106) in the pressure-reduced state as
filled with Ar was either of seven conditions of 4.times.10.sup.3
Pa, 1.times.10.sup.3 Pa, 4.times.10.sup.2 Pa, 1.times.10.sup.2 Pa,
4.times.10.sup.1 Pa, 1.times.10.sup.1 Pa, and 4 Pa. After that, the
connection flanges 104 were disconnected from the substrate-loading
exhauster, and the Ar supplying pipes (not shown) are disconnected
from the source gas supply means 612, and the power supply lines to
the reaction vessels 601 were also disconnected.
[0172] After the above operation, the movable reaction vessel
sections 101 and 110 were moved to the installation site of the
exhaust section 102 and the connection flanges 104 were connected
through the Viton O-ring (vacuum seal) to the exhaust-side
connection flanges 105. After that, the connection sections 103
were fixed by clamps. The source gas supply pipes (not shown) were
connected to the source gas supply means 612 and the power supply
lines and high frequency power supply cables were further connected
to the reaction vessel sections 101 and 110.
[0173] After completion of these connection operations, the
exhaust-side vacuum seal valves 109 were first opened to evacuate
the interior of the pipes 115 by the exhaust means 107. When the
pressure in the pipes 115 became 0.1 times the pressure in the
reaction vessels 601 (106), the reaction-vessel-side vacuum seal
valves 108 were opened to evacuate the interior of the reaction
vessels 106 to below 1.times.10.sup.-3 Pa. On this occasion, the
conductance varying valves 114 were kept in the full open
state.
[0174] In the next place, while the cylindrical substrates 605 were
rotated at the speed of 10 rpm via the rotation shafts 608 and
gears 610 by the motors 609, Ar was supplied at the flow rate of
500 sccm through the source gas supply means 612 into the reaction
vessels 601 and the pressure in the reaction vessels was adjusted
to 70 Pa by the conductance varying valves 114. While reducing the
internal pressure to 70 Pa, the cylindrical substrates 605 were
again heated and controlled to 250.degree. C. by the heaters 607
and that state was maintained for 20 minutes. During the Ar supply
start period, the flow rate of Ar was linearly increased from 0
sccm to 500 sccm in 5 minutes.
[0175] After completion of the reheating of the substrates, the
supply of Ar was stopped and the source gases under the conditions
for the charge injection blocking layer presented in Table 2 were
introduced through the source gas supply means 612. After the flow
rates of the source gases reached the set flow rates, the
conductance varying valves 114 were adjusted to set the pressure in
the reaction vessels to the condition in Table 2. After confirming
that the pressure in the reaction vessels 601 (106) became stable,
the total output of the high frequency power supplies 603 and 614
was set to the power presented in Table 2 and the high frequency
power was supplied through the matching boxes 604 and 613 to the
cathode electrodes 602 and 606. The high frequency power radiated
from the cathode electrodes 602 and 606 into the reaction vessels
601 (106) induced the plasma discharge to excite and dissociate the
source gases, thereby starting formation of the charge injection
blocking layers on the cylindrical substrates 605. After that, at
the point of time when the charge injection blocking layers were
formed in the thickness presented in Table 2, the supply of the
high frequency power was stopped and then the supply of the source
gases was also stopped, thereby terminating the formation of the
charge injection blocking layers. After that, similar operation was
repeated to form the photoconductive layer and surface layer
sequentially, thereby obtaining layered structures.
[0176] After completion of the formation of the a-Si based
photosensitive members in this way, the source gas inside the
reaction vessels 601 (106) and in the source gas supply pipes was
fully purged and then the vacuum seal valves 108 and 109 were
closed. Then, He was introduced into the reaction vessels 601 (106)
thus hermetically closed, up to the internal pressure of 1000 Pa.
After that, the connection sections 103 were disconnected and the
source gas supply pipes, power supply lines, and high frequency
power supply cables were also disconnected, thus bringing the
reaction vessel sections 101 and 110 into the movable state.
[0177] Then, the reaction vessel sections 101 and 110 were moved to
the substrate unloading site and the substrates 605 were cooled to
room temperature. Then, nitrogen was introduced through the
unrepresented leak valves into the reaction vessels 601 (106)
before the interior of the reaction vessels 601 (106) reached the
atmospheric pressure. After the interior of the reaction vessels
601 (106) reached the atmospheric pressure, the substrates 605 with
the deposited films thereon were taken out of the interior of the
reaction vessels 601 (106).
[0178] After that, the reaction vessels 601 (106) after completion
of the series of a-Si deposited film forming steps were restored by
exchange of the internal components thereof whereby the reaction
vessels 601 (106) were again brought into the deposition formable
state.
[0179] In this way, using the two reaction vessel sections 101 and
110, three lots of a-Si based photosensitive members, i.e., 36
members, were formed under the conditions presented in Table 2, for
each of the above-stated seven conditions.
Comparative Example 2
[0180] The a-Si based photosensitive members were produced under
the conditions presented in Table 2 in much the same manner as in
Example 2 except that, after the connection of the reaction vessel
sections 101 and 110 to the exhaust section, the exhaust-side
vacuum seal valves 109 were opened to evacuate the interior of the
pipes by the exhaust means 107 and the reaction-vessel-side vacuum
seal valves 108 were then opened when the pressure in the pipes
became ten times the pressure in the reaction vessels 601 (106). In
this Comparative Example 2, three lots of a-Si based photosensitive
members, i.e., 36 members were formed for each of the
aforementioned seven conditions, using the two reaction vessel
sections 101 and 110.
[0181] With the a-Si based photosensitive members produced in
Example 2 and in Comparative Example 2, each a-Si based
photosensitive member was set in a copying machine (trade name:
NP-6750; mfd. by CANON Inc.) modified for tests and evaluation was
conducted as to each of items, "optical memory," "characteristic
variability," and "image defects" described below. The evaluation
methods of the respective items will be described below in
detail.
[0182] "Optical Memory"
[0183] The electric current of the main charger was adjusted so
that the dark potential at the position of the developing unit
became a predetermined value, and image exposure intensity was then
adjusted so that the bright potential for an original of a
predetermined white sheet became a predetermined value. In this
state a ghost test chart (part number: FY9-9040; mfd. by CANON
Inc.) provided with glued black dots having the reflection density
of 1.1 and the diameter of 5 mm was placed on the original stage
and a halftone chart mfd. by CANON Inc. was laid thereon. In this
state copy images were obtained and evaluation thereof was
conducted by measuring the difference between reflection density of
the halftone portions and reflection density of 5 mm-diameter black
dots of the ghost chart recognized on the halftone copies.
[0184] For each of the photosensitive members, the optical memory
was measured across the entire region in the direction along the
generator of the photosensitive member and a maximum reflection
density difference among measurements was employed as an index of
the evaluation. The evaluation was conducted for all the
photosensitive members produced under the same conditions and an
average thereof was employed as an evaluation result of optical
memory.
[0185] "Characteristic Variability"
[0186] From the maximum reflection density differences of the
respective photosensitive members measured in the above evaluation
of "optical memory," a maximum and a minimum were extracted from
those in all the photosensitive members produced under the same
conditions. Then, a ratio of (maximum)/(minimum) was calculated and
employed as an index of characteristic variability. Accordingly,
smaller values indicate better results of small characteristic
variability.
[0187] "Image Defects"
[0188] A halftone chart (part number: FY9-9042; mfd. by CANON Inc.)
was placed on the original stage and copied. White dots having the
diameter of not less than 0.1 mm were counted in a fixed area of
the copy images obtained. The image defects were evaluated using
the number of white dots as an index. Accordingly, smaller values
indicate better results.
[0189] Table 3 presents the evaluation results. Table 3 shows the
results of relative evaluation in five levels on the basis of the
results in the condition that the pressure in the reaction vessels
106 was 4.times.10.sup.3 Pa, in Comparative Example 2.
[0190] "Optical memory" was evaluated by the classification of the
following five levels:
[0191] .circle-w/dot. improvement of not less than 20%;
[0192] .smallcircle. improvement of not less than 10% but less than
20%;
[0193] .DELTA. improvement of not less than 5% but less than
10%;
[0194] .tangle-solidup. improvement of less than 5% or degradation
of less than 5%;
[0195] x degradation of not less than 5%.
[0196] "Characteristic variability" were evaluated by the
classification of the following five levels:
[0197] .circle-w/dot. improvement of not less than 40%;
[0198] .smallcircle. improvement of not less than 20% but less than
40%;
[0199] .DELTA. improvement of not less than 10% but less than
20%;
[0200] .tangle-solidup. improvement of less than 10% or degradation
of less than 10%;
[0201] x degradation of not less than 10%.
[0202] "Image defects" were evaluated by the classification of the
following five levels:
[0203] .circle-solid. improvement of not less than 80%;
[0204] .smallcircle. improvement of not less than 40% but less than
80%;
[0205] .DELTA. improvement of not less than 20% but less than
40%;
[0206] .tangle-solidup. improvement of less than 20% or degradation
of less than 20%;
[0207] x degradation of not less than 20%.
[0208] From the results presented in Table 3, when comparison is
made between the results under the same conditions of the internal
pressure during the movement of the reaction vessels, a definite
difference is seen between Example 2 and Comparative Example 2.
Therefore, this result ensures the effects of the present invention
owing to the setting in which the internal pressure of the reaction
vessels is set higher than the pressure of the exhaust section
during the connection between the movable reaction vessel sections
and the exhaust section. The effects of the present invention
appear more prominent when the pressure in the reaction vessels 106
is not more than 1.times.10.sup.3 Pa during the movement of the
movable reaction vessel sections 101 and 110 to the installation
site of the exhaust section 102. Particularly, it was verified that
the effects became further prominent at the pressures of not more
than 1.times.10.sup.2 Pa.
[0209] The electrophotographic images formed using the
electrophotographic, photosensitive members produced in Example 2
were extremely excellent without image smearing or the like.
2 TABLE 2 Charge injection Photo- blocking conductive Surface layer
layer layer Gas species/ flow rate: SiH.sub.4 200 sccm 300 sccm 20
sccm H.sub.2 200 sccm 1000 sccm B.sub.2H.sub.6 1000 ppm 1.2 ppm
(over SiH.sub.4) (over SiH.sub.4) CH.sub.4 100 sccm NO 10 sccm
Substrate 250.degree. C. 250.degree. C. 250.degree. C. temperature
Internal 1.3 Pa 1.3 Pa 1.3 Pa pressure of reaction vessel High
frequency 900 W 1800 W 750 W power Film thickness 3 .mu.m 30 .mu.m
0.5 .mu.m
[0210]
3 TABLE 3 Example 2 Comparative Example 2 Internal Charac- Charac-
pressure Optical teristic Image Optical teristic Image (Pa) memory
variability defects memory variability defects 4 .times. 10.sup.3
.smallcircle. .smallcircle. .DELTA. -- -- -- 1 .times. 10.sup.3
.circleincircle. .circleincircle. .smallcircle. .tangle-solidup.
.tangle-solidup. .tangle-solidup. 4 .times. 10.sup.2
.circleincircle. .circleincircle. .smallcircle. .tangle-solidup.
.tangle-solidup. .tangle-solidup. 1 .times. 10.sup.2
.circleincircle. .circleincircle. .circleincircle. .tangle-solidup.
.tangle-solidup. .DELTA. 4 .times. 10.sup.1 .circleincircle.
.circleincircle. .circleincircle. .DELTA. .DELTA. .DELTA. 1 .times.
10.sup.1 .circleincircle. .circleincircle. .circleincircle. .DELTA.
.DELTA. .DELTA. 4 .circleincircle. .circleincircle.
.circleincircle. .DELTA. .DELTA. .DELTA.
Example 3
[0211] Using the vacuum processing system illustrated in FIG. 6,
the a-Si based photosensitive members were formed under the
conditions presented in Table 2, on cylindrical aluminum cylinders
605 having the diameter of 80 mm and the length of 358 mm in much
the same manner as in Example 2, except for the following
operations.
[0212] In the present example, during the movement of the movable
reaction vessel sections 101 and 110 to the installation site of
the exhaust section 102, the pressure P1 (Pa) in the reaction
vessels 106 was set to 1.times.10 Pa. After the connection between
the movable reaction vessel sections 101 and 110 and the exhaust
section 102, the reaction-vessel-side vacuum seal valves 108 were
opened when the pressure P2 (Pa) in the pipes 115 evacuated by the
exhaust section 102 was measured relative to the pressure P1 (Pa)
in the reaction vessels 106 so that the difference P1-P2 between
them was either of the five conditions of 4 Pa, 1 Pa,
4.times.10.sup.-1 Pa, 1.times.10.sup.-1 Pa, and 4.times.10.sup.-2
Pa. Using the two reaction vessel sections 101 and 110, three lots
of a-Si based photosensitive members, i.e., 36 members were made
under each of the five conditions.
[0213] Just as in Example 2, each of the a-Si based photosensitive
members produced in the present example was also set in a copying
machine (trade name: NP-6750; mfd. by CANON Inc.) modified for the
tests and evaluated as to the three items of "optical memory,"
"characteristic variability," and "image defects" in accordance
with the aforementioned evaluation methods.
[0214] Table 4 presents the evaluation results. Just as in Table 3,
Table 4 also shows the results of relative evaluation in five
levels on the basis of the results in the condition that the
pressure in the reaction vessels 106 was 4.times.10.sup.3 Pa, in
Comparative Example 2.
[0215] "Optical memory" was evaluated by the classification of the
following five levels:
[0216] .circle-w/dot. improvement of not less than 20%;
[0217] .smallcircle. improvement of not less than 10% but less than
20%;
[0218] .DELTA. improvement of not less than 5% but less than
10%;
[0219] .tangle-solidup. improvement of less than 5% or degradation
of less than 5%;
[0220] x degradation of not less than 5%.
[0221] "Characteristic variability" were evaluated by the
classification of the following five levels:
[0222] .circle-w/dot. improvement of not less than 40%;
[0223] .smallcircle. improvement of not less than 20% but less than
40%;
[0224] .DELTA. improvement of not less than 10% but less than
20%;
[0225] .tangle-solidup. improvement of less than 10% or degradation
of less than 10%;
[0226] x degradation of not less than 10%.
[0227] "Image defects" were evaluated by the classification of the
following five levels:
[0228] .circle-w/dot. improvement of not less than 80%;
[0229] .smallcircle. improvement of not less than 40% but less than
80%;
[0230] .DELTA. improvement of not less than 20% but less than
40%;
[0231] .tangle-solidup. improvement of less than 20% or degradation
of less than 20%;
[0232] x degradation of not less than 20%.
[0233] The results of evaluation ensured the effects of the present
invention and verified that the effects of the present invention
appeared prominent, particularly, when the pressure P1 (Pa) during
the movement of the vacuum processing vessels and the pressure P2
(Pa) of the space to communicate therewith upon opening of the
first opening, satisfied the following relation:
P1-P2.gtoreq.0.1 Pa;
[0234] and further verified that the effects became more prominent
when the pressures satisfied the following relation:
P1-P2.gtoreq.1 Pa.
[0235] The electrophotographic images formed using the
electrophotographic, photosensitive members produced in Example 3
were extremely excellent without image smearing or the like.
4 TABLE 4 Internal pressure difference Example 3 P1-P2 Optical
Characteristic Image (Pa) memory variability defects 4
.circleincircle. .circleincircle. .circleincircle. 1
.circleincircle. .circleincircle. .circleincircle. 4 .times.
10.sup.-1 .smallcircle. .circleincircle. .circleincircle. 1 .times.
10.sup.-1 .smallcircle. .circleincircle. .circleincircle. 4 .times.
10.sup.-2 .smallcircle. .smallcircle. .smallcircle.
Example 4
[0236] Using the vacuum processing system illustrated in FIG. 6,
the a-Si based photosensitive members were formed under the
conditions presented in Table 2, on cylindrical aluminum cylinders
605 having the diameter of 80 mm and the length of 358 mm in much
the same manner as in Example 2, except for the following
operations.
[0237] In the present example, during the movement of the movable
reaction vessel sections 101 and 110 to the installation site of
the exhaust section 102, the pressure P1 (Pa) in the reaction
vessels 106 was set at 1.times.10.sup.3 Pa. After the connection of
the movable reaction vessel sections 101 and 110 to the exhaust
section 102, the reaction-vessel-side vacuum seal valves 108 were
opened under the condition that the pressure P2 (Pa) in the pipes
115 evacuated by the exhaust section 102 was 0.1 times the pressure
P1 (Pa) in the reaction vessels 106, i.e., 1.times.10.sup.2 Pa. In
addition, after the opening of the reaction-vessel-side vacuum seal
valves 108, the aperture rate of the conductance varying valves was
continuously changed so as to linearly decrease the exhaust
resistance as illustrated in FIG. 7. Using the two reaction vessel
sections 101 and 110, three lots of a-Si based photosensitive
members, i.e., 36 members were formed according to the
aforementioned operation procedures.
[0238] Just as in Example 2, each of the a-Si based photosensitive
members produced in the present example was also set in a copying
machine (trade name: NP-6750; mfd. by CANON Inc.) modified for the
tests and evaluated as to the three items of "optical memory,"
"characteristic variability," and "image defects" in accordance
with the aforementioned evaluation methods.
[0239] Table 5 presents the evaluation results. Just as in Table 3,
Table 5 also shows the results of relative evaluation in five
levels on the basis of the results in the condition that the
pressure in the reaction vessels 106 was 4.times.10.sup.3 Pa, in
Comparative Example 2.
[0240] "Optical memory" was evaluated by the classification of the
following five levels:
[0241] .circle-w/dot. improvement of not less than 20%;
[0242] .smallcircle. improvement of not less than 10% but less than
20%;
[0243] .DELTA. improvement of not less than 5% but less than
10%;
[0244] .DELTA. improvement of less than 5% or degradation of less
than 5%;
[0245] x degradation of not less than 5%.
[0246] "Characteristic variability" were evaluated by the
classification of the following five levels:
[0247] .circle-w/dot. improvement of not less than 40%;
[0248] .smallcircle. improvement of not less than 20% but less than
40%;
[0249] .DELTA. improvement of not less than 10% but less than
20%;
[0250] .tangle-solidup. improvement of less than 10% or degradation
of less than 10%;
[0251] x degradation of not less than 10%.
[0252] "Image defects" were evaluated by the classification of the
following five levels:
[0253] .circle-w/dot. improvement of not less than 80%;
[0254] .smallcircle. improvement of not less than 40% but less than
80%;
[0255] .DELTA. improvement of not less than 20% but less than
40%;
[0256] .tangle-solidup. improvement of less than 20% or degradation
of less than 20%;
[0257] x degradation of not less than 20%.
[0258] The results of the present example shown in Table 5 were
compared with the results of the samples made in such a manner that
upon opening of the reaction-vessel-side vacuum seal valves 108
under the condition of P1=1.times.10.sup.3 Pa and
P2=1.times.10.sup.2 Pa, the conductance varying valves were
preliminarily fully opened (where the exhaust resistance was
equivalent to the value indicated by 30 in FIG. 7) and thereafter
the evacuation was continued at the constant exhaust resistance
without change of the aperture rate, in Example 2. The both
examples demonstrated prominent improvements in all the three items
of "optical memory," "characteristic variability," and "image
defects," and the present example exhibited the better result in
"image defects." This verified that the vacuum processing method of
the present invention demonstrated the more prominent effects of
the present invention by employing such procedures that during the
period of, after the connection between the reaction vessel
sections 101 and 110 with the substrates therein, and the exhaust
section 102, opening the reaction-vessel-side vacuum seal valves
108 to establish the communication between the reaction vessel
sections and the exhaust section, the exhaust resistance was first
set large to limit the exhaust quantity of the exhaust section and
thereafter the exhaust resistance was continuously decreased with
progress of evacuation.
[0259] The electrophotographic images formed using the
electrophotographic, photosensitive members produced in Example 4
were extremely excellent without image smearing or the like.
5 TABLE 5 Internal Example 4 pressure Optical Characteristic Image
P1 (Pa) memory variability defects 1 .times. 10.sup.3
.circleincircle. .circleincircle. .circleincircle.
Example 5
[0260] Using the vacuum processing system illustrated in FIG. 6,
the a-Si based photosensitive members were formed under the
conditions presented in Table 2, on cylindrical aluminum cylinders
605 having the diameter of 80 mm and the length of 358 mm in much
the same manner as in Example 4, except for the following
operations.
[0261] In Example 4, after the opening of the reaction-vessel-side
vacuum seal valves 108, the aperture rate of the conductance
varying valves was varied so as to linearly decrease the exhaust
resistance as illustrated in FIG. 7, whereas in the present example
the aperture rate of the conductance varying valves was changed
stepwise to decrease the exhaust resistance stepwise as illustrated
in FIG. 8. Using the two reaction vessel sections 101 and 110,
three lots of a-Si based photosensitive members, i.e., 36 members
were made according to the aforementioned operation procedures.
[0262] Just as in Example 2, each of the a-Si based photosensitive
members produced in the present example was also set in a copying
machine (trade name: NP-6750; mfd. by CANON Inc.) modified for the
tests and evaluated as to the three items of "optical memory,"
"characteristic variability," and "image defects" in accordance
with the aforementioned evaluation methods.
[0263] Table 6 presents the evaluation results. Just as in Table 3,
Table 6 also shows the results of relative evaluation in five
levels on the basis of the results in the condition that the
pressure in the reaction vessels 106 was 4.times.10.sup.3 Pa, in
Comparative Example 2.
[0264] "Optical memory" was evaluated by the classification of the
following five levels:
[0265] .circle-w/dot. improvement of not less than 20%;
[0266] .smallcircle. improvement of not less than 10% but less than
20%;
[0267] .DELTA. improvement of not less than 5% but less than
10%;
[0268] .tangle-solidup. improvement of less than 5% or degradation
of less than 5%;
[0269] x degradation of not less than 5%.
[0270] "Characteristic variability" were evaluated by the
classification of the following five levels:
[0271] .circle-w/dot. improvement of not less than 40%;
[0272] .smallcircle. improvement of not less than 20% but less than
40%;
[0273] .DELTA. improvement of not less than 10% but less than
20%;
[0274] .tangle-solidup. improvement of less than 10% or degradation
of less than 10%;
[0275] x degradation of not less than 10%.
[0276] "Image defects" were evaluated by the classification of the
following five levels:
[0277] .circle-w/dot. improvement of not less than 80%;
[0278] .smallcircle. improvement of not less than 40% but less than
80%;
[0279] .DELTA. improvement of not less than 20% but less than
40%;
[0280] .tangle-solidup. improvement of less than 20% or degradation
of less than 20%;
[0281] x degradation of not less than 20%.
[0282] The results of the present example shown in Table 5 were
compared with the results of the samples made in such a manner that
upon opening of the reaction-vessel-side vacuum seal valves 108
under the condition of P1=1.times.10.sup.3 Pa and
P2=1.times.10.sup.2 Pa, the conductance varying valves were
preliminarily fully opened (where the exhaust resistance was
equivalent to the value indicated by 30 in FIG. 8) and thereafter
the evacuation was continued at the constant exhaust resistance
without change of the aperture rate, in Example 2. The both
examples demonstrated prominent improvements in all the three items
of "optical memory," "characteristic variability," and "image
defects," and the present example exhibited the better result in
"image defects." This better improvement in the "image defects" is
comparable to that in aforementioned Example 4.
[0283] Accordingly, it was verified that the vacuum processing
method of the present invention demonstrated the more prominent
effects of the invention by employing such procedures that during
the period of, after the connection between the reaction vessel
sections 101 and 110 with the substrates therein, and the exhaust
section 102, opening the reaction-vessel-side vacuum seal valves
108 to make the communication between the reaction vessel sections
and the exhaust section, the exhaust resistance was first set large
to limit the exhaust quantity of the exhaust section and thereafter
the exhaust resistance was gradually decreased with progress of
evacuation. It is also seen that the mode of decrease in exhaust
resistance can be any mode of gradually decreasing the exhaust
resistance according to the progress of evacuation, without any
essential difference in the effect; e.g., not only the continuous
change as in Example 4, but also the stepwise change as in the
present embodiment.
[0284] The electrophotographic images formed using the
electrophotographic, photosensitive members produced in Example 5
were extremely excellent without image smearing or the like.
6 TABLE 6 Internal Example 5 pressure Optical Characteristic Image
P1 (Pa) memory variability defects 1 .times. 10.sup.3
.circleincircle. .circleincircle. .circleincircle.
Example 6
[0285] Using a system having the structure similar to the system
used in Example 2, deposited films were formed by the plasma CVD
method, on cylindrical aluminum cylinders 605 having the diameter
of 80 mm and the length of 358 mm. The high frequency power
supplies 603 and 614 were set to the oscillation frequency of 100
MHz and the a-Si deposited films were formed under the deposition
conditions presented in Table 2.
[0286] In the present example, during the connection between the
movable reaction vessel sections and the exhaust section, the
interior of the pipes 115 between the vacuum seal valves 108 and
the vacuum seal valves 109 was evacuated by the auxiliary exhauster
113. The final pressure was 4.0 Pa in the pipes 115 evacuated by
the auxiliary exhauster 113.
[0287] The procedures of formation of the a-Si deposited films in
the present example will be described below.
[0288] First, the movable reaction vessel sections 101, 110 were
connected through their connection flanges 104 to the
substrate-loading exhauster (not shown), and the Ar supplying pipes
(not shown), and the power supply lines to the reaction vessel
sections 101, 110 were also connected. In this state, the
cylindrical substrates 605 were loaded into the reaction vessels
601 (106). Then, the vacuum seal valves 108 were opened to evacuate
the interior of the reaction vessels 601 through the exhaust ducts
611 by the substrate-loading exhauster. After confirming that the
interior of the reaction vessels 601 (106) was evacuated to below
1.times.10.sup.-3 Pa, Ar was supplied at the flow rate of 500 sccm
through the source gas supply means 612 into the reaction vessels
601 (106). While the pressure in the reaction vessels was
maintained at 70 Pa by the unrepresented pressure regulating
valves, the cylindrical substrates 605 were heated and controlled
to 250.degree. C. by the heaters 607. The heating state of the
substrates under this pressure-reduced Ar atmosphere was maintained
for two hours. During this period the cylindrical substrates 605
were rotated at the speed of 10 rpm via the rotation shafts 608 and
gears 610 by the motors 609. During the Ar supply start period the
flow rate of Ar was linearly increased from 0 sccm to 500 sccm in 5
minutes.
[0289] Next, the vacuum seal valves 108 are closed, the supply of
Ar was stopped, and the reaction vessels 601 (106) were
hermetically sealed in the pressure-reduced state. On that
occasion, the supply of Ar was first stopped and the vacuum seal
valves 108 were closed at the internal pressure of 6.times.10.sup.1
Pa in the reaction vessels 601 (106), and the heating of the
substrates 605 by the heaters 607 was terminated. After that, the
connection flanges 104 were disconnected from the substrate-loading
exhauster and the Ar supplying pipes (not shown) connected to the
source gas supply means 612, and the power supply lines to the
reaction vessels 601 were also disconnected.
[0290] After the above operation, the movable reaction vessel
sections 101 and 110 were moved to the installation site of the
exhaust section 102 and the connection flanges 104 were connected
through the Viton O-ring (vacuum seal) to the exhaust-side
connection flanges 105. After that, the connection sections 103
were fixed by clamps. The source gas supply pipes (not shown) were
connected to the source gas supply means 612 and the power supply
lines and high frequency power supply cables were further connected
to the reaction vessel sections 101 and 110.
[0291] After completion of these connections, the interior of the
pipes 115 was first evacuated by the auxiliary exhauster 113.
During the connection of the movable reaction vessel section 101,
it was confirmed that the valve 111 was closed, and thereafter the
valve 112 was opened to evacuate the interior of the pipes 115 by
the auxiliary exhauster 113. When the pressure in the pipes 115
reached 4.5 Pa, the reaction-vessel-side vacuum seal valve 108 was
opened to preliminarily evacuate the interior of the reaction
vessel 106 by the auxiliary exhauster 113. When the pressure in the
reaction vessel 601 (106) reached 4.2 Pa, the valve 112 was then
closed and the exhaust-side vacuum seal valve 109 was opened. On
this occasion, the pressure on the exhaust section side of the
exhaust-side vacuum seal valve 109 was 1.times.10.sup.-4 Pa. The
conductance varying valve 114 was kept in the flow open state.
[0292] In the next place, while the cylindrical substrates 605 were
rotated at the speed of 10 rpm via the rotation shafts 608 and
gears 610 by the motors 609, Ar was supplied at the flow rate of
500 sccm from the source gas supply means 612 into the reaction
vessel 601 and the pressure in the reaction vessel was adjusted to
70 Pa by the conductance varying valve 114. While reducing the
internal pressure to 70 Pa, the cylindrical substrates 605 were
again heated and controlled to 250.degree. C. by the heaters 607
and that state was maintained for 20 minutes. During the Ar supply
start period, the flow rate of Ar was linearly increased from 0
sccm to 500 sccm in 5 minutes.
[0293] After completion of the reheating of the substrates, the
supply of Ar was stopped and the source gases under the conditions
for the charge injection blocking layer presented in Table 2 were
introduced through the source gas supply means 612. After the flow
rates of the source gases reached the set flow rates, the
conductance varying valve 114 was adjusted to set the pressure in
the reaction vessel to the condition in Table 2. After confirming
that the pressure in the reaction vessel 601 (106) became stable,
the total output of the high frequency power supplies 603 and 614
was set to the power presented in Table 2 and the high frequency
power was supplied through the matching boxes 604 and 613 to the
cathode electrodes 602 and 606. The high frequency power radiated
from the cathode electrodes 602 and 606 into the reaction vessel
601 (106) induced the plasma discharge to excite and dissociate the
source gases, thereby starting formation of the charge injection
blocking layers on the cylindrical substrates 605. After that, at
the point of time when the charge injection blocking layers were
formed in the thickness presented in Table 2, the supply of the
high frequency power was stopped and then the supply of the source
gases was also stopped, thereby terminating the formation of the
charge injection blocking layers. After that, similar operation was
repeated to form the photoconductive layer and surface layer
sequentially, thereby obtaining the layered structures.
[0294] After completion of the formation of the a-Si based
photosensitive members in this way, the source gas inside the
reaction vessels 601 (106) and in the source gas supply pipes was
fully purged and then the vacuum seal valves 108 and 109 were
closed. Then, He was introduced into the reaction vessel 601 (106)
thus hermetically closed, up to the internal pressure of 1000 Pa.
After that, the connection section 103 was disconnected and the
source gas supply pipes, power supply lines, and high frequency
power supply cables were also disconnected, thus bringing the
reaction vessel section 101 into the movable state.
[0295] Then, the reaction vessel section 101 was moved to the
substrate unloading site and the substrates 605 were cooled to room
temperature. Then, nitrogen was introduced through the
unrepresented leak valve into the reaction vessel 601 (106) before
the interior of the reaction vessel 601 (106) reached the
atmospheric pressure. After the interior of the reaction vessel 601
(106) reached the atmospheric pressure, the substrates 605 with the
deposited films thereon were taken out of the interior of the
reaction vessel 601 (106).
[0296] After that, the reaction vessel 601 (106) after completion
of the series of a-Si deposited film forming steps was restored by
exchange of the internal components thereof whereby the reaction
vessel 601 (106) was again brought into the deposition formable
state.
[0297] On the other hand, subsequent to the deposited film forming
step by use of the reaction vessel section 101, the reaction vessel
section 110 was also moved to the exhaust section 102, connected to
the exhaust section 102, and subjected to the deposited film
forming steps according to similar procedures. After completion of
the deposited film forming steps and completion of the substrate
unloading, the reaction vessel section 110 was also subjected to
the exchange of internal components thereof according to similar
procedures, whereby the reaction vessel section 110 was brought
again into the deposition formable state and was again used in the
steps of forming the photosensitive members for
electrophotography.
[0298] As described above, the reaction vessel section 101 and the
reaction vessel section 110 were sequentially connected to the
exhaust section 102 in order, and three lots of photosensitive
members for electrophotography, 36 members in total, were made by
each of the reaction vessel sections.
Comparative Example 3
[0299] In this Comparative Example, the deposited films were formed
on the cylindrical aluminum cylinders 605 having the diameter of 80
mm and the length of 358 mm by the plasma CVD method in much the
same manner as in Example 6, except that, during the movement of
the reaction vessel sections 101 and 110 to the exhaust section 102
after the loading of the substrates 605 into the reaction vessel
sections 101 and 110, the pressure in the reaction vessels 601
(106) was set at 6.times.10.sup.-1 Pa. Using the two reaction
vessel sections 101 and 110, three lots of photosensitive members
for electrophotography, totally 36 members, were made by each of
them.
[0300] In this comparative example, therefore, the pipes 115 were
also evacuated by the auxiliary exhauster 113 during the connection
of the reaction vessel sections 101 and 110 to the exhaust section
102 and the reaction-vessel-side vacuum seal valve 108 was opened
at the point when the internal pressure of the pipes 115 reached
4.5 Pa. Since during the movement the pressure in the reaction
vessel 601 (106) was kept at 6.times.10.sup.-1 Pa, the opening of
the vacuum seal valve 108 caused the residual gas to flow backward
from the pipes 115 to the interior of the reaction vessel 601
(106). Consequently, after increase of pressure in the reaction
vessel 601 (106) due to the back flow, the operation was carried
out according to procedures of first closing the valve 112,
disconnecting the auxiliary exhauster 113, and opening the
exhaust-side vacuum seal valve 109.
[0301] Just as in Example 2, the a-Si based photosensitive members
produced in Example 6 and in Comparative Example 3 were also
evaluated as to the three items of "optical memory,"
"characteristic variability," and "image defects," according to the
evaluation methods described in Example 2.
[0302] Table 7 presents the evaluation results. Table 7 describes
the results of relative evaluation in five levels on the basis of
the results of Comparative Example 3.
[0303] "Optical memory" was evaluated by the classification of the
following five levels:
[0304] .circle-w/dot. improvement of not less than 20%;
[0305] .smallcircle. improvement of not less than 10% but less than
20%;
[0306] .DELTA. improvement of not less than 5% but less than
10%;
[0307] .tangle-solidup. improvement of less than 5% or degradation
of less than 5%;
[0308] x degradation of not less than 5%.
[0309] "Characteristic variability" were evaluated by the
classification of the following five levels:
[0310] .circle-w/dot. improvement of not less than 40%;
[0311] .smallcircle. improvement of not less than 20% but less than
40%;
[0312] .DELTA. improvement of not less than 10% but less than
20%;
[0313] .tangle-solidup. improvement of less than 10% or degradation
of less than 10%;
[0314] x degradation of not less than 10%.
[0315] "Image defects" were evaluated by the classification of the
following five levels:
[0316] .circle-w/dot. improvement of not less than 80%;
[0317] .smallcircle. improvement of not less than 40% but less than
80%;
[0318] .DELTA. improvement of not less than 20% but less than
40%;
[0319] .tangle-solidup. improvement of less than 20% or degradation
of less than 20%;
[0320] x degradation of not less than 20%.
[0321] It is apparent from Table 7 that the photosensitive members
for electrophotography produced in Example 6 were clearly superior
in all the three items of "optical memory," "characteristic
variability," and "image defects," to those produced in Comparative
Example 3. It was also verified from this comparison that the
effects of the present invention were attained by such setting that
on the occasion of linkage between the movable reaction vessel
sections and the exhaust section, the first openable/closable
opening provided in the movable reaction vessel section, i.e., the
reaction-vessel-side vacuum seal valve 108 in this example was
opened under the condition that the internal pressure of the
reaction vessel was set higher than the pressure of the exhaust
duct 115 communicating therewith. Namely, it was ensured that when
the internal pressure of the reaction vessel was set higher than
the pressure of the exhaust duct 115 communicating therewith, the
by-products and the like accumulated in the exhaust duct 115 during
the vacuum processing heretofore were effectively prevented from
entering the interior of the reaction vessel.
[0322] The electrophotographic images formed using the
electrophotographic, photosensitive members produced in Example 6
were extremely excellent without image smearing or the like.
7TABLE 7 Example 6 Optical Characteristic Image memory variability
defects .circleincircle. .circleincircle. .circleincircle.
[0323] As described above, according to the vacuum processing
method of the present invention, it is possible to carry out a
stable vacuum processing and a vacuum processing such as formation
of a deposited film and the like without variability in
quality.
[0324] In addition, according to the present invention, it is
feasible to prevent a dust from attaching onto an article in a step
of moving a vacuum processing vessel with the article being placed
therein and connecting the vacuum processing vessel to a
pressure-reduced space different therefrom.
[0325] Further, according to the present invention, in a vacuum
process in which a vacuum processing vessel is moved with an
article being placed therein, the vacuum processing vessel is
connected to a pressure-reduced space different therefrom, and
thereafter at least one of vacuum processing steps is carried out;
by keeping the vacuum processing vessel in a pressure-reduced state
during the movement, and on the occasion thereafter of, after the
connection to the different pressure-reduced space, opening an
openable/closable opening provided in the vacuum processing vessel
to establish communication between them, by setting the internal
pressure of the vacuum processing vessel higher than the pressure
of the different pressure-reduced space communicating therewith, it
is possible to prevent a dust from attaching onto the article and
achieve increase in non-defective percentage of articles to be
subjected to the vacuum process.
[0326] In addition, the present invention also makes it feasible to
achieve improvement in the vacuum processing characteristics and
suppression of variability among lots. Particularly, since the
present invention permits selection of operation conditions, it
does not degrade the flexibility of production, ensures excellent
vacuum processing characteristics of vacuum-processed articles, and
also ensures the uniformity in each lot, of course, and high
repeatability among lots.
[0327] Namely, the present invention provides a vacuum processing
method of a step configuration that is free from the factors to
cause variability in the vacuum processing characteristics among
lots and is also excellent in the flexibility of production.
* * * * *