U.S. patent application number 10/548764 was filed with the patent office on 2006-06-15 for pump.
This patent application is currently assigned to Tadahiro Ohmi. Invention is credited to Masafumi Kitano, Tadahiro Ohmi, Yasuyuki Shirai.
Application Number | 20060127245 10/548764 |
Document ID | / |
Family ID | 32984544 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127245 |
Kind Code |
A1 |
Ohmi; Tadahiro ; et
al. |
June 15, 2006 |
Pump
Abstract
A vacuum pump having a high corrosion resistance is disclosed. A
member constituting the vacuum pump is composed of aluminum or an
aluminum alloy, and the surface of the member is subjected to a
plasma oxidation treatment such as an oxidation treatment using
oxygen radicals, so that a dense and smooth aluminum oxide coating
film is formed thereon.
Inventors: |
Ohmi; Tadahiro; (Miyagi,
JP) ; Shirai; Yasuyuki; (Miyagi, JP) ; Kitano;
Masafumi; (Miyagi, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
Tadahiro Ohmi
|
Family ID: |
32984544 |
Appl. No.: |
10/548764 |
Filed: |
March 5, 2004 |
PCT Filed: |
March 5, 2004 |
PCT NO: |
PCT/JP04/02858 |
371 Date: |
September 9, 2005 |
Current U.S.
Class: |
417/410.2 |
Current CPC
Class: |
F04C 18/16 20130101;
F04C 2230/92 20130101; F05C 2201/903 20130101; F05C 2203/0869
20130101; F04C 2280/04 20130101; F04C 2220/12 20130101 |
Class at
Publication: |
417/410.2 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2003 |
JP |
2003-66689 |
Claims
1. A pump having an inlet port for a gas to be exhausted and a
discharge port for said gas, wherein a member exposed to said gas
is made of aluminum or an aluminum alloy and said member has, as a
surface layer, an oxide coating film oxidized by a plasma
treatment.
2. A pump having an inlet port for a medium to be exhausted and a
discharge port for said medium, wherein a member exposed to said
medium is made of aluminum or an aluminum alloy and said member has
as a surface layer an oxide coating film oxidized by oxygen
radicals.
3. A pump according to claim 1 or 2, wherein said surface layer is
specified by the oxide coating film of the aluminum or aluminum
alloy containing a very small amount of a noble gas component.
4. A pump according to claim 3, wherein said noble gas component is
krypton or xenon.
5. A pump having an inlet port for a gas to be exhausted and a
discharge port for said gas, wherein a member exposed to said gas
is made of an aluminum alloy containing at least one selected from
the group consisting of magnesium, strontium, barium, zirconium,
and hafnium, said member has an oxide coating film as a surface
layer of a portion exposed to said gas, and said oxide coating film
contains an oxide of aluminum.
6. A pump according to claim 5, wherein said oxide coating film
further contains at least one oxide among respective oxides of
magnesium, strontium, barium, zirconium, and hafnium.
7. A pump having an inlet port for a gas to be exhausted and a
discharge port for said gas, wherein a member exposed to said gas
is made of an aluminum alloy and said member has, as a surface
layer, an oxide coating film oxidized by a plasma treatment, said
aluminum alloy containing 0.01 wt % or less of each of Fe, Mn, Cr,
and Zn.
8. A vacuum pump for use in a vacuum processing system, wherein a
member exposed to a medium to be exhausted from said vacuum
processing system is made of aluminum or an aluminum alloy and,
further, has as a surface layer an oxide coating film oxidized by a
plasma treatment at a portion exposed to said medium.
9. A vacuum pump for use in a vacuum processing system, wherein a
member exposed to a medium to be exhausted from said vacuum
processing system is made of aluminum or an aluminum alloy and,
further, has as a surface layer an oxide coating film oxidized by
oxygen radicals at a portion exposed to said medium.
10. A vacuum pump according to claim 8 or 9, wherein said surface
layer is the oxide coating film of the aluminum or aluminum alloy
containing a very small amount of a noble gas component.
11. A vacuum pump according to claim 10, wherein said noble gas
component is krypton or xenon.
12. A vacuum pump for use in a vacuum processing system, at least
portion of which is exposed to a medium to be exhausted from said
vacuum processing system, wherein the portion exposed to said
medium is made of an aluminum alloy containing at least one
selected from the group consisting of magnesium, strontium, barium,
zirconium, and hafnium and further includes an oxide of aluminum as
a surface layer.
13. A vacuum pump according to claim 12, wherein said surface layer
contains at least one oxide selected from the group consisting of
magnesium, strontium, barium, zirconium, and hafnium.
14. A vacuum pump according to claim 12, wherein said aluminum
alloy contains 0.01 wt % or less of each of Fe, Mn, Cr, and Zn.
15. A vacuum pump according to claim 8 or 9, wherein said vacuum
processing system is a plasma processing system that performs a
plasma treatment.
16. A vacuum pump according to claim 8 or 9, wherein said medium is
a reactive gas or chemical liquid.
17. A pump having an inlet port for a medium to be exhausted and a
discharge port for said medium, wherein a pump member exposed to
said medium has a base material formed of iron containing aluminum
and has as a surface layer a coating film of an oxide of said
aluminum oxidized by a plasma treatment.
18. A pump comprising an inlet port for a medium to be exhausted
and a discharge port for said medium, wherein a member exposed to
said medium has a base material formed of iron containing aluminum
and has as a surface layer a coating film of an oxide of said
aluminum oxidized by oxygen radicals.
19. A pump according to claim 17 or 18, wherein said base material
is a stainless steel containing 3 to 7 wt % aluminum.
20. A pump according to claim 17 or 18, wherein said surface layer
is the coating film of the oxide of the aluminum containing a very
small amount of a noble gas component.
21. A pump according to claim 17 or 18, wherein said coating film
of the oxide of the aluminum is formed on a surface of at least a
portion exposed to said medium.
22. A vacuum pump for use in a vacuum processing system wherein a
member at least part of which is exposed to a medium to be
exhausted from said vacuum processing system has a base material
composed of iron containing aluminum and has as a surface layer a
coating film of an oxide of said aluminum oxidized by a plasma
treatment.
23. A vacuum pump for use in a vacuum processing system wherein a
member at least part of which is exposed to a medium to be
exhausted from said vacuum processing system has a base material
formed of iron containing aluminum and has as a surface layer a
coating film of an oxide of said aluminum oxidized by oxygen
radicals.
24. A vacuum pump according to claim 22 or 23, wherein said base
material is a stainless steel containing 3 to 7 wt % aluminum.
25. A vacuum pump according to claim 22 or 23, wherein said surface
layer is the coating film of the oxide of the aluminum containing a
very small amount of a noble gas component.
26. A vacuum pump according to claim 22 or 23, wherein said coating
film of the oxide of the aluminum is formed on a surface of at
least a portion exposed to said medium.
27. A vacuum pump comprising a base material composed of iron
containing aluminum and a surface layer formed by a coating film of
an oxide of said aluminum oxidized by oxygen radicals.
28. A vacuum pump according to claim 27, wherein said coating film
of the oxide of the aluminum is formed on a surface of at least a
portion exposed to said medium.
Description
TECHNICAL FIELD
[0001] This invention relates to a pump and, in particular, relates
to a vacuum pump for use in a vacuum processing system and a
manufacturing method thereof.
BACKGROUND ART
[0002] Generally, vacuum processing systems for use in
manufacturing semiconductor devices or the like include a cluster
type system and an in-line type system and these systems each
comprise a plurality of chambers and a transfer mechanism for
transferring processing members (wafers, glass substrates). In
these vacuum processing systems, various treatments such as various
film formation and etching are applied to a processing member in
each chamber in a state lower than the atmospheric pressure (i.e.
vacuum state). In this connection, each chamber constituting the
vacuum processing system is provided with a plurality of vacuum
pumps for evacuating the chamber. Further, it is a recent trend
that members or objects to be processed, such as wafers and glass
substrates, become large in size and the vacuum processing systems
are also increased in size with an increase of the objects to be
processed. As a result, the vacuum processing systems tend to have
a heavy weight such that they are too heavy to be transported by
normal transportation means.
[0003] Recently, a plasma processing system has been proposed that
performs plasma oxidation or oxygen radical oxidation in a
particular chamber. This plasma processing system is implemented by
a cluster type vacuum processing system. In such a plasma
processing system, since a gas or the like that is a medium to be
exhausted is highly reactive, a vacuum pump itself should be formed
by a material that is strong against corrosion due to the reactive
medium.
[0004] The processing system of this type uses, as evacuation
vacuum pumps, a wide variety of pumps such as a turbomolecular
pumps, cryopumps, booster pumps, dry pumps, and scroll pumps. These
vacuum pumps each include vacuum pump members, such as rotors,
blades, shafts, and gears which are accommodated in a casing
provided with an inlet port and a discharge port.
[0005] Normally, the vacuum pump members or articles constituting
the vacuum pump are each made of an aluminum alloy such as
duralumin, a stainless steel, or the like. In view of lightening
the vacuum pump in weight, the aluminum alloy is preferable.
[0006] However, even if the aluminum alloy would be used in a
vacuum pump in the plasma processing system, the inner walls of the
vacuum pump is corroded by media such as ions and other active
species generated upon dissociation of various gases due to a
plasma and corrosive gases. Therefore, the aluminum alloy cannot be
used in the plasma processing system.
[0007] On the other hand, if the stainless steel would be also used
in the vacuum pump made, it is not possible to obtain sufficient
corrosion resistance against the media such as the active species.
These problems are not limited to the vacuum pumps in the plasma
processing system but shall apply to the whole range of pumps that
discharge corrosive media.
[0008] There has been a proposal for applying an anodic oxidation
treatment shown in Japanese Unexamined Patent Application
Publication (JP-A) No. H7-216589 (patent document 1) to a vacuum
pump to thereby form a corrosion resistant alumina film
(Al.sub.2O.sub.3) on the surface of a member made of aluminum or an
aluminum alloy.
[0009] Actually, Japanese Unexamined Patent Application Publication
(JP-A) No. 2003-21062 (patent document 2) describes a cryopump
having an anodically oxidized cryopanel.
[0010] However, an Al.sub.2O.sub.3 coating film formed by anodic
oxidation is basically a porous film and the surface thereof is
also rough. Therefore, the anodically oxidized Al.sub.2O.sub.3
coating film is very low in corrosion resistance against a reactive
gas or chemical liquid such as, for example, a Cl-based gas, a
F-based gas, HCl, H.sub.2SO.sub.4, or HF.
[0011] Further, a post treatment of the the anodically oxidized
Al.sub.2O.sub.3 coating film is also performed by applying a
high-temperature steam to the coating film and by thereby sucking
up molecules into the coating film to expand it. As a result, voids
are filled with the above-mentioned method.
[0012] Herein, it is assumed that the anodically oxidized aluminum
alloy subjected to the foregoing post treatment is used for gas
exhaust vacuum pump members for the plasma system. In this event,
it is to be noted that processing in such a plasma system is
generally carried out at a high degree of pressure-reduction. Under
the circumstances, it takes much time to reach a predetermined
degree of pressure-reduction when the above-mentioned anodically
oxidized aluminum alloy is used in the plasma system.
[0013] This is because, since the oxide coating film at the surface
of the anodically oxidized aluminum alloy is primarily porous, it
takes an unnecessarily long time to evacuate to the predetermined
degree of the pressure-reduction due to a problem of outgassing and
the presence of the voids formed and remaining in the film.
[0014] Further, when electroless nickel plating is applied to an
aluminum alloy, nickel serves as a catalyst to decompose, for
example, a SiH.sub.4, B.sub.2H.sub.8, PH.sub.3, AsH.sub.3, or
ClF.sub.3 gas and, as a result, accelerates generation of corrosive
gas and product.
DISCLOSURE OF THE INVENTION
[0015] It is therefore an object of this invention to provide a
vacuum pump that is usable against a corrosive gas in a vacuum
processing system.
[0016] It is another object of this invention to provide a vacuum
pump that is small in size and light in weight.
[0017] It is still another object of this invention to provide a
pump having high corrosion resistance against a reactive gas or
chemical liquid.
[0018] A pump of this invention is characterized in that a portion
exposed to an exhausted medium is made of aluminum or an aluminum
alloy and, further, has an oxide coating film oxidized by a plasma
treatment.
[0019] As the oxide coating film oxidized by the plasma treatment,
it is possible to cite, for example, an oxide coating film oxidized
by oxygen radicals produced by plasma.
[0020] According to researches by the present inventors, it has
been confirmed that an oxide coating film formed on the surface of
aluminum or an aluminum alloy by a plasma treatment, for example,
by oxygen radicals produced by a plasma, is extremely dense with
the surface thereof being flat and, further, has almost no voids
existing in the film. Further, it has been found that such an oxide
coating film is strong and has an improved corrosion
resistance.
[0021] Therefore, it has been found that, by using a member having
such a coating film as a pump member, particularly a pump member
that contacts a reactive medium, a time required for evacuation to
a predetermined degree of pressure-reduction can be shortened than
conventional and the corrosion resistance is also improved. The
oxidation by oxygen radicals is implemented by transforming an
oxygen-containing gas into plasma to thereby apply a plasma
treatment to the aluminum or aluminum alloy surface in a manner to
be described later.
[0022] A pump member of this invention may be made of aluminum or
an aluminum alloy and the surface of the vacuum pump member has a
coating film of an oxide of aluminum or an aluminum alloy
containing a very small amount of a noble gas component.
[0023] By the addition of the noble gas, the film stress is
suppressed to improve adhesion and reliability. As the noble gas, a
krypton (Kr) gas or a xenon (Xe) gas is particularly
preferable.
[0024] Further, it may be configured such that a pump member of
this invention is made of an aluminum alloy containing at least one
of magnesium, strontium, and barium in aluminum, the surface of the
vacuum pump member has an oxide coating film, and the oxide coating
film contains an oxide of aluminum and at least one oxide among
respective oxides of magnesium, strontium, and barium. Such a
member for a plasma processing system has a further improved
corrosion resistance.
[0025] The aluminum alloy may contain at least zirconium or at
least hafnium. When it is contained, the mechanical strength is
improved.
[0026] Further, the content of each of Fe, Mn, Cr, and Zn in the
aluminum alloy is preferably 0.01 wt % or less. This is because the
corrosion resistance is degraded when the above-mentioned metals
are contained.
[0027] In the foregoing, the description has been made about the
case where the aluminum or aluminum alloy is used as a base
material of the vacuum pump member. However, this invention is not
limited thereto at all. The surface of a base material formed by
iron containing aluminum may be processed by a plasma oxidation
treatment or an oxygen radical oxidation treatment to form an
aluminum oxide coating film on the surface of the base material. In
this case, use may be made of a technique that selectively oxidizes
aluminum contained in the base material by the plasma treatment to
thereby form an aluminum oxide film on the surface. As such a base
material containing aluminum, there is a stainless steel or the
like.
[0028] As a method of forming an aluminum oxide coating film on the
surface of a necessary portion of a pump member by a plasma
treatment or the like, it is possible to apply a plasma processing
method described in Patent Application No. 2003-028476
Specification.
[0029] According to this invention, as compared with the
conventional anodic oxidation treatment, there is formed a coating
film that is dense and has a flat surface and further the corrosion
resistance is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a block diagram showing an evacuation system for
carrying out an embodiment of this invention.
[0031] FIG. 2 shows a back pump of the evacuation system in FIG. 1,
wherein (a) is one sectional view and (b) is another sectional
view.
[0032] FIG. 3 is a schematic sectional view showing a plasma
processing system that is used for the processing of this
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0033] Hereinbelow, an embodiment of this invention will be
described. Referring to FIG. 1, a cluster type vacuum processing
system is shown as a vacuum processing system applicable to a
vacuum pump according to this invention. This vacuum processing
system comprises a plurality of reaction chambers (vacuum
containers) 10, 11, and 12, two load lock chambers 13 and 14, and a
transfer chamber 15.
[0034] Further, in order to bring the inside of each of the
reaction chambers (vacuum containers) 10, 11, and 12 into a
pressure-reduced or vacuum state, the reaction chambers (vacuum
containers) 10, 11, and 12 are coupled with high vacuum pumps 1, 2,
and 3, one or more pumps per chamber. Booster pumps 4a, 5a, and 6a
and back pumps (dry pumps) 4b, 5b, and 6b are arranged at
subsequent stages of the high vacuum pumps, respectively, In the
illustrated example, booster pumps 7a, 8a, and 9a and back pumps
7b, 8b, and 9b are connected to the load lock chambers 13 and 14
and the transfer chamber 15, respectively. Further, valves 22, 23,
and 24 are provided between the high vacuum pumps 1, 2, and 3 and
the booster pumps 4a, 5a, and 6a, respectively.
[0035] This invention may be applicable to various pumps that may
be, for example, a turbomolecular pump (thread groove pump), a
cryopump, a mechanical booster pump, a dry pump (back pump), and a
scroll pump. Hereinbelow, the back pump (FIG. 2) will be described
as an example.
[0036] Herein, at first, description will be made about operation
of the vacuum processing system shown in FIG. 1. Processing objects
such as wafers are brought or carried into the load lock chamber 13
and then the processing objects brought into the load lock chamber
13 are transferred into the reaction chambers 10, 11, and 12
through the transfer chamber 15 provided therein with a robot
(transfer apparatus) that transfers the processing objects. After
the processing objects are processed into processed objects in the
reaction chambers 10, 11, and 12, the processed objects are
transferred from the reaction chambers 10, 11, and 12 into the load
lock chamber 14 through the transfer chamber 15.
[0037] Further, although not illustrated, the reaction chambers
(vacuum containers) 10, 11, and 12 are each provided with a gas
inlet and heating means such as a heater to thereby carry out
predetermined processing, such as film formation, while a
predetermined gas is being introduced for heating. A plasma
oxidation treatment or an oxidation treatment using oxygen radicals
is executed in at least one of the reaction chambers 10, 11, and
12. When such an oxidation treatment is carried out, the gas is
decomposed into a corrosive gas in the reaction chamber and this
corrosive gas is successively exhausted by the illustrated vacuum
pumps of the plurality of the stages.
[0038] In FIG. 1, A1 denote pipes between the high vacuum pumps 1,
2, and 3 and the booster pumps 4a, 5a, and 6a, respectively, while
A2 denote pipes between the reaction chambers (vacuum containers)
10, 11, and 12 and the high vacuum pumps 1, 2, and 3, respectively.
Further, in the figure, R denotes a clean room.
[0039] The illustrated vacuum processing system is first put on a
standby state. In this standby state, the transfer chamber 15 and
the reaction chambers (vacuum containers) 10, 11, and 12 are each
held in a pressure-reduced or vacuum state.
[0040] In this state, a cassette with a plurality of processing
objects such as wafers placed therein is brought into the load lock
chamber 13 from the outside of the vacuum processing system kept in
an atmosphere and the load lock chamber 13 is evacuated.
[0041] Subsequently, a gate valve (not illustrated) between the
load lock 1S chamber 13 and the transfer chamber 15 is opened and
the processing object transfer robot extends its transfer arm to
pick up one of the processing objects from the cassette and moves
it into the transfer chamber 15.
[0042] Thereafter, a gate between the reaction chamber (vacuum
container) 10 and the transfer chamber 15 is opened and the
processing object is placed on a stage in the reaction chamber
(vacuum container) 10 by the use of the transfer arm. After the
predetermined processing such as film formation, the processed
object is transferred into the other reaction chamber 11 or 12 or
the load lock chamber 14 by the use of the transfer arm. After the
processing, the processed object is finally transferred to the
exterior from the load lock chamber 14.
[0043] Among the foregoing reaction chambers 10, 11, and 12, at
least one chamber is used to form an oxide layer on the processing
object by plasma oxidation or oxygen radicals and to discharge the
reactive gas to the back pump through the high vacuum pump and the
booster pump. Although this invention may be applied only to the
vacuum pumps that exhaust the reactive gas, description will be
made on the assumption that this invention is applied to all of the
pumps, such as the high vacuum pumps 1, 2, and 3 provided for all
the reaction chambers 1, 2, and 3, the booster pumps 4a to 9a, and
the back pumps (dry pumps) 4b to 9b.
[0044] Referring to FIG. 2, (a) and (b), the vacuum pump of this
invention will be described that is exemplified by the back pumps
4b to 9b. The illustrated vacuum pump comprises a screw pump body A
and the body A has a pair of screw rotors 25 and 26 having a
plurality of helical ridge portions and groove portions and adapted
to rotate about two substantially parallel axes with both screw
rotors engaged with each other.
[0045] The screw rotors 25 and 26 are housed in a casing 27 and
rotatably supported by bearings 35 at one-side ends of shafts 28
supporting the screw rotors 25 and 26. Timing gears 30 are attached
to the shafts 28 at one-end portions thereof while a motor (not
illustrated) is coupled to the other end of the shaft 28. When the
shaft 28 is rotated by the motor, the pair of screw rotors 25 and
26 are synchronously rotated through the timing gears 30.
[0046] An inlet port 31 is formed on a one-end side of the casing
27 housing therein both screw rotors 25 and 26 while a discharge or
an outlet port 32 (FIG. 2, (b)) is formed on the other-end side of
the casing 27. In this example, the inlet port 31 is connected to
the chamber side while the discharge port 32 is coupled to the
atmosphere. When the screw rotors 25 and 26 are synchronously
rotated by the motor, a gas from the chamber side is sucked through
the inlet port 31 and discharged through the discharge port 32 and,
as a result, the gas in the chamber is exhausted.
[0047] On the discharge port 32 side of the illustrated casing 27,
a jacket 33 is formed which has a cavity portion and which can
circulate cooling water through the cavity portion. This structure
makes it possible on the discharge port 32 side to particularly
cool heat generation caused by compression operation of a gas.
[0048] At the other-end portion of the casing 27 having both screw
rotors 25 and 26 housed therein, a cover 34 is attached and the
shaft 28 supporting the screw rotor 26 projects from the cover 34
so as to be directly coupled to a rotation shaft of the
later-described motor. Further, seal members 29 are provided
between the bearings 35 and the screw rotors 25 and 26,
respectively.
[0049] Let all the members of the back pump (dry pump) shown in
FIG. 2 be made of aluminum or an aluminum alloy as a base material.
Among them, the rotors 25 and 26, the casing 27, the seal members
29, the inlet port 31, the discharge port 32, and so on (also the
shafts 28 as the case may be) are exposed to a corrosive gas or
chemical liquid while exhausting such a corrosive gas or chemical
liquid. In this case, as the reactive gas or chemical liquid, there
is cited, for example, a Cl-based gas, a F-based gas, HCl,
H.sub.2SO.sub.4, or HF.
[0050] By applying the treatment according to this invention to all
the members constituting the back pump, the whole back pumps can
have corrosion resistance. However, plasma oxidation or oxygen
radical oxidation according to this invention may be executed only
at least those surfaces of the members to be exposed to the
corrosive gas, i.e. the rotors 25 and 26, the casing 27, the seal
members 29, the inlet port 31, and the discharge port 32. As shown
by thick lines in FIG. 2, (a) and (b), aluminum oxide coating films
are therefore formed on the surfaces of the respective members. The
aluminum oxide film formed by the plasma oxidation treatment or the
oxidation treatment using oxygen radicals has a feature that it has
no voids and is extremely dense and the surface thereof is flat.
Therefore, it is possible to maintain high corrosion resistance
against the reactive gas and so on.
[0051] Referring to FIG. 3, description will be made about a method
of forming the foregoing aluminum oxide coating film on a vacuum
pump member by the use of a plasma processing system 1. It is
assumed that the illustrated plasma processing system 1 performs
processing of a vacuum pump member 40 shown in a rectangular shape.
The plasma processing system 1 comprises a process container 2 with
a cylindrical bottom and an open upper portion. The process
container 2 is made of, for example, an aluminum alloy. The process
container 2 is grounded. A susceptor 3 for placing thereon the
vacuum pump member 40 is provided at the bottom of the process
container 2. The susceptor 3 is made of, for example, an aluminum
alloy. By power feed from an AC power supply 4 provided outside the
process container 2, a heater 5 of the susceptor 3 is heated so
that the vacuum pump member 40 on the susceptor 3 is heated to
300.degree. C.
[0052] An evacuation device 41, such as a turbomolecular pump, Is
connected to bottom portions of the process container 2 through
exhaust pipes 42 so that the inside of the process container 2 is
evacuated by the evacuation device 41. Further, a supply pipe 44 is
extended through an inner wall of the process container 2 so as to
supply a process gas from a process gas supply source 43. In this
embodiment, the process gas supply source 43 is connected to supply
sources 45 and 46 of an oxygen gas (O.sub.2) and an argon (Ar) gas
being an inert gas.
[0053] At the upper opening of the process container 2, a
dielectric window 22 made of, for example, a quartz glass is
mounted on a seal member 21, such as an O-ring for ensuring
airtightness. By this dielectric window 22, a process space S is
formed in the process container 2.
[0054] An antenna member 51 is provided above the dielectric window
22. In this example, the antenna member 51 comprises, for example,
a radial slot antenna 52 located on the bottommost position, a
wave-shortening plate or a wave retardation plate 53 located at an
upper portion thereof, and an antenna cover 54 covering the
wave-shortening plate 53 to protect and cool it.
[0055] The radial slot antenna 52 is in the form of a thin disk
made of a conductive material such as copper and the disk is formed
with pairs of slits concentrically arranged wherein each pair of
slits form an acute angle approximate to a right angle.
[0056] At the center of the wave-shortening plate 53 is disposed a
bump 55 which is made of a conductive material such as a metal and
which forms a part of a conical shape. This bump 55 is electrically
connected to an inner conductor 56a of a coaxial waveguide 56
composed of the inner conductor 56a and an outer pipe 56b. The
coaxial waveguide 56 is configured so that a microwave of, for
example, 2.45 GHz produced by a microwave supply device 57 is
propagated to the antenna member 51 through a load matching device
58 and the coaxial waveguide 56.
[0057] Next, description will be made about a plasma processing
method implemented in the illustrated vacuum processing system 1.
At first, the vacuum pump member 40 formed by aluminum or an
aluminum alloy is placed on the susceptor 3. In this state, the
oxygen gas containing krypton is supplied from the supply source 45
and plasma is produced in the process container 2. In this case,
the vacuum pump member 40 is maintained at a temperature of
450.degree. C. or less (preferably 150.degree. C. to 250.degree.
C.). It is to be noted that even in the state where the vacuum pump
member 40 was maintained at a room temperature (e.g. 23.degree.
C.), it was possible to generate plasma in the process container
2.
[0058] When the plasma was generated, oxygen radicals were produced
in the process container 2 and thus the surface of the vacuum pump
member 40 was oxidized by the oxygen radicals so that an oxide
coating film was formed.
[0059] It was confirmed that the oxide coating film produced by the
oxidation treatment using the oxygen radicals was an
Al.sub.2O.sub.3 coating film that had no voids and was extremely
dense and flat on its surface. This is because the aluminum or
aluminum alloy surface was reformed or modified in properties due
to the oxygen radicals.
[0060] A reaction formula in this case is as follows.
2Al+3O*.fwdarw.Al.sub.2O.sub.3
[0061] Further, when the vacuum pump member 40 was formed by an
aluminum alloy containing magnesium (Mg), an oxide coating film
(Al.sub.2O.sub.3) containing much MgO was able to be formed on the
aluminum alloy surface due to oxygen radicals. The oxide coating
film containing MgO in this manner can improve the strength. In
this case, the content of magnesium is preferably 0.5 wt % to a
solid-solution maximum amount (about 6.0 wt %). When an oxygen gas
containing krypton was transformed into a plasma to produce oxygen
radicals, an oxide coating film containing MgO was able to be
obtained even with an extremely small content of magnesium like 0.5
wt % to 1.0 wt %.
[0062] As the aluminum alloy, use can be made of an aluminum alloy
containing, other than magnesium as described above, strontium,
barium, zirconium, or hafnium. By forming an oxide coating film
containing much SrO or BaO on the aluminum alloy surface, it was
possible to improve the corrosion resistance and strength of the
vacuum pump member 40.
[0063] Further, when use was made of an aluminum alloy containing
about 0.1 to 0.15 wt % zirconium, it was possible to provide the
vacuum pump member 40 with high corrosion resistance and mechanical
strength by suppressing the growth of alloy particles. Further,
also when use was made of an aluminum alloy containing 0.1 to 0.15
wt % hafnium, it was confirmed that the vacuum pump member with
high corrosion resistance and mechanical strength was obtained by
suppressing the grain growth of the aluminum alloy.
[0064] On the other hand, the aluminum alloy often contains Fe, Mn,
Cr, and Zn but, since they reduce the corrosion resistance of the
aluminum alloy, the content of each of them is preferably 0.01 wt %
or less. Fe, Mn, Cr, and Zn in the aluminum alloy can be removed by
hydrogen reduction of the vacuum pump member 40 at a temperature of
450.degree. C. or less prior to the oxidation treatment.
[0065] The description has been made about the case where krypton
(Kr) was added to the oxygen-containing gas to produce the plasma
so as to generate oxygen radicals by the plasma. This is because,
by the addition of the krypton gas, krypton excited to a high
energy state collides with an oxygen molecule so that two oxygen
radicals can be easily generated.
[0066] Further, when producing oxygen radicals, oxygen plasma may
be generated by the use of a gas obtained by adding an argon (Ar)
gas to an oxygen-containing gas. When the argon gas is used, since
the argon gas is easy to handle and is inexpensive, the vacuum pump
member 40 can be easily and inexpensively processed actually.
[0067] As described above, when the plasma oxidation treatment such
as the oxidation treatment using oxygen radicals is performed by
generating the plasma by the use of the noble gas, such as krypton
or argon, the produced oxide coating film contains a very small
amount of the noble gas component, This noble gas component serves
to suppress a film stress of the oxide coating film to improve
adhesion and reliability thereof.
[0068] As the plasma source for generating the oxygen plasma, use
was made of the 2.45 GHz frequency microwave plasma in the
foregoing plasma processing system 1. Since the microwave plasma is
highly dense and is not so strong with a relatively low Vdc, the
oxide coating film can be formed by the radical oxidation of the
surface of the vacuum pump member 40 without giving damage to the
aluminum or aluminum alloy surface.
[0069] Further, in the foregoing examples, the description has been
made only about the case where the vacuum pump member 40 is made of
aluminum or the aluminum alloy. However, this invention is not
limited thereto at all. A similar effect was obtained in the case
of forming an aluminum oxide coating film on the surface of a
vacuum pump member formed by a stainless steel containing
aluminum.
[0070] Further, the pump to which this invention is applicable is
not limited to that shown in FIG. 2. This invention is generally
applied to a pump that is exposed to a highly corrosive gas or
chemical liquid, and Is particularly effective by applying a
coating film containing an aluminum oxide to the surface of a
member that contacts such a gas or chemical liquid.
INDUSTRIAL APPLICABILITY
[0071] A pump according to this Invention can be used as a vacuum
pump for evacuating the inside of a chamber in a vacuum processing
system for use In manufacturing semiconductor devices or the
like.
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