U.S. patent application number 11/826275 was filed with the patent office on 2008-02-14 for cleaning method and cleaning apparatus for porous member.
Invention is credited to Hiroyuki Kanda, Natsuki Makino, Kazufumi Nomura.
Application Number | 20080035171 11/826275 |
Document ID | / |
Family ID | 39049389 |
Filed Date | 2008-02-14 |
United States Patent
Application |
20080035171 |
Kind Code |
A1 |
Kanda; Hiroyuki ; et
al. |
February 14, 2008 |
Cleaning method and cleaning apparatus for porous member
Abstract
A porous member cleaning method enables effective cleaning of
the interior of a porous member even when it has a small pore size,
a high density and a large volume. The porous member cleaning
method includes: disposing a porous member in a hermetic space, and
cleaning the interior of the porous member with a pressurized
cleaning liquid passing through the interior of the porous member;
and then disposing the porous member in said hermetic space or in a
different hermetic space, and supplying pressurized pure water to
the interior of the porous member so that the pure water passes
through the interior of the porous member.
Inventors: |
Kanda; Hiroyuki; (Tokyo,
JP) ; Makino; Natsuki; (Tokyo, JP) ; Nomura;
Kazufumi; (Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
39049389 |
Appl. No.: |
11/826275 |
Filed: |
July 13, 2007 |
Current U.S.
Class: |
134/3 ; 118/500;
134/95.1 |
Current CPC
Class: |
B08B 3/12 20130101; B08B
7/00 20130101 |
Class at
Publication: |
134/003 ;
118/500; 134/095.1 |
International
Class: |
C23G 1/02 20060101
C23G001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2006 |
JP |
2006-194361 |
Claims
1. A porous member cleaning method comprising: disposing a porous
member in a hermetic space, and cleaning the interior of the porous
member with a pressurized cleaning liquid passing through the
interior of the porous member; and then disposing the porous member
in said hermetic space or in a different hermetic space, and
supplying pressurized pure water to the interior of the porous
member so that the pure water passes through the interior of the
porous member.
2. The porous member cleaning method according to claim 1, wherein
the cleaning liquid and/or pure water in the hermetic space is
bubbled with a gas.
3. The porous member cleaning method according to claim 1, wherein
the cleaning liquid is sulfuric acid, nitric acid, hydrofluoric
acid, hydrochloric acid, a hydrogen peroxide solution, pure water,
or a mixed solution thereof, an alkaline cleaning liquid or a
neutral detergent, or a combination thereof.
4. The porous member cleaning method according to claim 1, wherein
the porous member is composed of a porous ceramic comprising
silicon carbide, alumina, aluminum nitride, zirconia or vanadium
oxide, or a porous resin.
5. The porous member cleaning method according to claim 1, wherein
the porous member has a porosity of not more than 40% and a pore
size of not more than 100 .mu.m.
6. The porous member cleaning method according to claim 1, wherein
the temperature of the cleaning liquid and the temperature of the
pure water are each 20 to 120.degree. C.
7. A porous member cleaning apparatus comprising: a hermetic vessel
for mounting a porous member and forming a hermetic space in the
vessel; a pressurized fluid injection section, connected to the
hermetic vessel, for selectively injecting one of a pressurized
cleaning liquid and pressurized pure water into the hermetic vessel
so that the cleaning liquid or pure water passes through the
interior of the porous member; and a fluid discharge section for
discharging the cleaning liquid or pure water which has passed
through the interior of the porous member.
8. The porous member cleaning apparatus according to claim 7
further comprising a gas supply section for supplying a gas for
bubbling to the cleaning liquid and/or pure water which has been
injected into the hermetic vessel.
9. A plating apparatus comprising: a substrate holder for holding a
substrate; a cathode section including a sealing member for contact
with a peripheral portion of a surface of the substrate held by the
substrate holder to water-tightly seal the peripheral portion, and
a cathode contact for contact with the substrate to feed
electricity to the substrate; and an anode section movable between
a processing position above the substrate holder and a porous
member cleaning position lateral to the processing position,
including an anode which, when the anode section is located in the
processing position, is disposed opposite the substrate held by the
substrate holder, and a porous member disposed between the anode
and the substrate, wherein a porous member cleaning section for
sequentially introducing a cleaning liquid and pure water into the
interior of the porous member of the anode section to clean the
interior of the porous member with the cleaning liquid and to
replace the cleaning liquid in the interior of the porous member
with pure water, is provided in the porous member cleaning
position.
10. The plating apparatus according to claim 9, wherein the porous
member cleaning section is provided in association with a plating
solution tray, disposed lateral to the substrate holder, for
storing a plating solution for use in idling.
11. A method for cleaning a porous member in a plating apparatus,
comprising: moving an anode section to a porous member cleaning
position lateral to a substrate holder, said anode section
including an anode which, when the anode section is located in a
processing position, is disposed opposite a substrate held by the
substrate holder, and a porous member disposed between the anode
and the substrate; and then introducing a cleaning liquid and pure
water into the interior of the porous member of the anode section,
located in the porous member cleaning position, to clean the
interior of the porous member with the cleaning liquid and to
replace the cleaning liquid in the interior of the porous member
with pure water.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a cleaning method and a
cleaning apparatus for porous members, and more particularly to a
cleaning method and a cleaning apparatus which are useful for
cleaning a porous member provided in an electroplating apparatus
for forming interconnects by filling an interconnect material, such
as copper, into fine interconnect patterns (recesses) formed in a
surface of a substrate, such as a semiconductor wafer, or a porous
member for use in a CMP apparatus or a cleaning apparatus, and to a
plating apparatus provided with the cleaning apparatus.
[0003] 2. Description of the Related Art
[0004] The applicant has proposed a plating apparatus (electrolytic
processing apparatus) in which a porous member (high-resistance
structure) is disposed between a substrate and an anode, and the
porous member is impregnated with a plating solution so as to make
the electrical resistivity of the porous member impregnated with
the plating solution higher than the electrical resistivity of the
plating solution, thereby making the influence of the surface sheet
resistance of the substrate as small as negligible and making it
possible to form a plated film having a more uniform thickness over
an entire surface of the substrate (see, for example, Japanese
Patent Laid-Open Publication No. 2002-235192).
[0005] Cutting debris, an organic material, etc., produced by
processing, adhere to a surface and the interior (interior surfaces
of pores) of such a porous member. It is therefore necessary to
pre-clean the porous member before incorporating and using it in a
plating apparatus. Further, there are cases where pores of a porous
member are clogged, e.g., with a black film which was formed on a
soluble anode and fell from the anode into the pores of the porous
member in a non-plating time, or with a secondary product with an
additive contained in a plating solution. The porous member
therefore needs to be cleaned periodically or according to
necessity.
[0006] Cleaning of such a porous member has conventionally been
carried out by ultrasonic cleaning in substantially the same manner
as cleaning for a common substrate, in particular, by a method
which, as illustrated in FIG. 15, comprises disposing a porous
member 302 in a cleaning vessel 300 and immersing the porous member
302 in a cleaning liquid 302, which is introduced into the cleaning
vessel 300 from its bottom and is allowed to overflow into an
overflow tank 306, while applying ultrasonic waves from an
ultrasonic oscillator 308 to the cleaning liquid 304 in the
cleaning vessel 300, thereby cleaning the porous member 302, and
then introducing pure water as a rinsing liquid into the cleaning
vessel 300 to rinse the cleaned porous member 302 with pure
water.
SUMMARY OF THE INVENTION
[0007] It has generally been difficult with ultrasonic cleaning of
a porous member to fully clean the interior of the porous member.
Thus, it takes a long time to fully clean the interior of a porous
member especially when the porous member has a large volume and
small-sized pores. There is recently a demand for the formation of
a plated film having a more uniform thickness over an entire
surface of a substrate. In order to meet the demand, it is
necessary to supply a plating solution through a porous member more
uniformly to a substrate. This requires stricter specifications for
the porosity and the pore size of the porous member, making it more
difficult to uniformly clean the interior of the porous member.
[0008] The present invention has been made in view of the above
situations. It is therefore an object of the present invention to
provide a cleaning method and a cleaning apparatus for porous
members, which enable effective cleaning of the interior of a
porous member even when it has a small pore size, a high density
and a large volume, and a plating apparatus provided with the
cleaning apparatus.
[0009] In order to achieve the above object, the present invention
provides a porous member cleaning method comprising: disposing a
porous member in a hermetic space, and cleaning the interior of the
porous member with a pressurized cleaning liquid passing through
the interior of the porous member; and then disposing the porous
member in said hermetic space or in a different hermetic space, and
supplying pressurized pure water to the interior of the porous
member so that the pure water passes through the interior of the
porous member.
[0010] The interior of a porous member can be cleaned more
effectively by thus directly cleaning the interior (interior
surfaces of pores) of the porous member with a cleaning liquid
passing through the interior, without using an external force as in
ultrasonic cleaning. Further, by replacing the cleaning liquid,
remaining in the interior of the porous member, with pure water,
adverse effects of the cleaning liquid on processing, such as
plating, can be prevented.
[0011] Preferably, the cleaning liquid and/or pure water in the
hermetic space is bubbled with a gas.
[0012] By thus allowing a cleaning liquid and/or pure water,
bubbled with a gas, to pass through the interior of a porous
member, particles, etc. adhering to the interior of the porous
member, i.e., the interior surfaces of pores, can be securely
peeled off and removed from the interior pore surfaces. An inert
gas, such as N.sub.2, may be used for the bubbling.
[0013] The cleaning liquid is, for example, sulfuric acid, nitric
acid, hydrofluoric acid, hydrochloric acid, a hydrogen peroxide
solution, pure water, or a mixed solution thereof, an alkaline
cleaning liquid or a neutral detergent, or a combination
thereof.
[0014] The porous member is composed of, for example, a porous
ceramic comprising silicon carbide, alumina, aluminum nitride,
zirconia or vanadium oxide, or a porous resin.
[0015] In a preferred aspect of the present invention, the porous
member has a porosity of not more than 40% and a pore size of not
more than 100 .mu.m.
[0016] The temperature of the cleaning liquid and the temperature
of the pure water are preferably each 20 to 120.degree. C.
[0017] The present invention provides a porous member cleaning
apparatus comprising: a hermetic vessel for mounting a porous
member and forming a hermetic space in the vessel; a pressurized
fluid injection section, connected to the hermetic vessel, for
selectively injecting one of a pressurized cleaning liquid and
pressurized pure water into the hermetic vessel so that the
cleaning liquid or pure water passes through the interior of the
porous member; and a fluid discharge section for discharging the
cleaning liquid or pure water which has passed through the interior
of the porous member.
[0018] The porous member cleaning apparatus preferably further
comprises a gas supply section for supplying a gas for bubbling to
the cleaning liquid and/or pure water which has been injected into
the hermetic vessel.
[0019] The present invention provides a plating apparatus
comprising: a substrate holder for holding a substrate; a cathode
section including a sealing member for contact with a peripheral
portion of a surface of the substrate held by the substrate holder
to water-tightly seal the peripheral portion, and a cathode contact
for contact with the substrate to feed electricity to the
substrate; and an anode section movable between a processing
position above the substrate holder and a porous member cleaning
position lateral to the processing position, including an anode
which, when the anode section is located in the processing
position, is disposed opposite the substrate held by the substrate
holder, and a porous member disposed between the anode and the
substrate, wherein a porous member cleaning section for
sequentially introducing a cleaning liquid and pure water into the
interior of the porous member of the anode section to clean the
interior of the porous member with the cleaning liquid and to
replace the cleaning liquid in the interior of the porous member
with pure water, is provided in the porous member cleaning
position.
[0020] By thus incorporating the porous member cleaning section for
cleaning a porous member integrally into the plating apparatus
having the porous member, the porous member can be cleaned
periodically or according to necessity without each taking the
porous member out of the plating apparatus.
[0021] In a preferred aspect of the present invention, the porous
member cleaning section is provided in association with a plating
solution tray, disposed lateral to the substrate holder, for
storing a plating solution for use in idling.
[0022] By thus providing the porous member cleaning section in
association with the plating solution tray for storing a plating
solution for use in idling, a significant increase in the size of
the plating apparatus can be avoided.
[0023] The present invention provides a method for cleaning a
porous member in a plating apparatus, comprising: moving an anode
section to a porous member cleaning position lateral to a substrate
holder, said anode section including an anode which, when the anode
section is located in a processing position, is disposed opposite a
substrate held by the substrate holder, and a porous member
disposed between the anode and the substrate; and then introducing
a cleaning liquid and pure water into the interior of the porous
member of the anode section, located in the porous member cleaning
position, to clean the interior of the porous member with the
cleaning liquid and to replace the cleaning liquid in the interior
of the porous member with pure water.
[0024] According to the present invention, the interior of a porous
member can be cleaned more effectively by directly cleaning the
interior (interior surfaces of pores) of the porous member with a
cleaning liquid passing through the interior. The present invention
thus enables effective cleaning of the interior of a porous member
even when it has a high density and a large volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is an overall plan view of a substrate processing
apparatus provided with a plating apparatus according to an
embodiment of the present invention;
[0026] FIG. 2 is a plan view of the plating apparatus shown in FIG.
1;
[0027] FIG. 3 is an enlarged cross-sectional view of a substrate
holder and a cathode section of the plating apparatus shown in FIG.
1;
[0028] FIG. 4 is a front view of a pre-coating/recovery arm of the
plating apparatus shown in FIG. 1;
[0029] FIG. 5 is a plan view of the substrate holder of the plating
apparatus shown in FIG. 1;
[0030] FIG. 6 is a cross-sectional view taken along line B-B of
FIG. 5;
[0031] FIG. 7 is a cross-sectional view taken along line C-C of
FIG. 5;
[0032] FIG. 8 is a plan view of the cathode section of the plating
apparatus shown in FIG. 1;
[0033] FIG. 9 is a cross-sectional view taken along line D-D of
FIG. 8;
[0034] FIG. 10 is a plan view of an electrode arm section of the
plating apparatus shown in FIG. 1;
[0035] FIG. 11 is a schematic cross-sectional diagram showing the
main portion of the plating apparatus shown in FIG. 1 when plating
is performed;
[0036] FIG. 12 is a schematic cross-sectional diagram showing the
main portion of the plating apparatus shown in FIG. 1 when a porous
member is cleaned;
[0037] FIG. 13 is a schematic diagram showing a porous member
cleaning apparatus according to an embodiment of the present
invention;
[0038] FIG. 14 is a schematic diagram showing a porous member
cleaning apparatus according to another embodiment of the present
invention; and
[0039] FIG. 15 is a schematic diagram showing a conventional porous
member cleaning apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] Preferred embodiments of the present invention will now be
described in detail with reference to the drawings.
[0041] FIG. 1 is an overall plan view showing a substrate
processing apparatus provided with a plating apparatus according to
an embodiment of the present invention. As shown in FIG. 1, this
substrate processing apparatus is provided with a rectangular
facility which houses therein two loading/unloading units 10 for
housing a plurality of substrates W therein, two plating
apparatuses 12 for performing plating process, a transfer robot 14
for transferring substrates W between the loading/unloading units
10 and the plating apparatuses 12, and plating solution supply
equipment 18 having a plating solution tank 16.
[0042] The plating apparatus 12, as shown in FIG. 2, is provided
with a substrate processing section 20 for performing plating
process and processing incidental thereto, and a plating solution
tray 22 for storing a plating solution for use in idling is
disposed adjacent to the substrate processing section 20. There is
also provided an electrode arm section 30 having an anode section
28 which is held at the front end of an arm 26 swingable about a
rotating shaft 24 and which moves between the substrate processing
section 20 and the plating solution tray 22. Furthermore, a
pre-coating/recovering arm 32, and fixed nozzles 34 for ejecting
pure water or a chemical liquid such as ion water, and further a
gas or the like toward a substrate are disposed laterally of the
substrate processing section 20. In this embodiment, three of the
fixed nozzles 34 are disposed, and one of them is used for
supplying pure water.
[0043] The substrate processing section 20, as shown in FIG. 3, has
a substrate holder 36 for holding a substrate W with its surface
(surface to be plated) facing upwardly, and a cathode section 38
located above the substrate holder 36 so as to surround a
peripheral portion of the substrate holder 36. Further, a
substantially cylindrical bottomed cup 40 surrounding the periphery
of the substrate holder 36 for preventing scatter of various
chemical liquids used during processing is provided so as to be
vertically movable by an air cylinder (not shown).
[0044] The substrate holder 36 is adapted to be raised and lowered
by the air cylinder 44 between a lower substrate transfer position
A, an upper plating position B, and a pretreatment/cleaning
position C intermediate between these positions. The substrate
holder 36 is also adapted to rotate at an arbitrary acceleration
and an arbitrary velocity integrally with the cathode section 38 by
a rotating motor and a belt (not shown). Substrate carry-in and
carry-out openings (not shown) are provided in confrontation with
the substrate transfer position A in a side panel of the plating
apparatus 12 facing the transfer robot 14. When the substrate
holder 36 is raised to the plating position B, a sealing member 90
and cathode contacts 88 (to be described below) of the cathode
section 38 are brought into contact with the peripheral portion of
the substrate W held by the substrate holder 36. On the other hand,
the cup 40 has an upper end located below the substrate carry-in
and carry-out openings, and when the cup 40 ascends, the upper end
of the cup 40 reaches a position above the cathode section 38
closing the substrate carry-in and carry-out openings, as shown by
imaginary lines in FIG. 3.
[0045] The plating solution tray 22 serves to store a plating
solution for performing idling (replacement of plating solution and
deforming) while wetting a porous member 110 and an anode 98 (to be
described later on) of the electrode arm section 30 with the
plating solution, when plating has not been performed. The plating
solution tray 22 is set at a size in which the porous member 110
can be accommodated, and the plating solution tray 22 has a plating
solution supply port and a plating solution drainage port (not
shown). A photo-sensor is attached to the plating solution tray 22,
and can detect brimming with the plating solution in the plating
solution tray 22, i.e., overflow, and drainage.
[0046] The electrode arm section 30 is vertically movable by a
vertical movement motor, which is a servomotor, and a ball screw,
and swingable between an idling position above the plating solution
tray 22 and a processing position above the substrate processing
section 20 by a swing motor, as described bellow. A compressed
actuator may be used.
[0047] As shown in FIG. 4, the pre-coating/recovering arm 32 is
coupled to an upper end of a vertical support shaft 58. The
pre-coating/recovering arm 32 is swingable by a rotary actuator 60
and is also vertically moveable by an air cylinder (not shown). The
pre-coating/recovering arm 32 supports a pre-coating nozzle 64 for
discharging a pre-coating liquid, on its free end side, and a
plating solution recovering nozzle 66 for recovering the plating
solution, on a portion closer to its proximal end. The pre-coating
nozzle 64 is connected to a syringe that is actuatable by an air
cylinder, for example, for intermittently discharging a pre-coating
liquid from the pre-coating nozzle 64. The plating solution
recovering nozzle 66 is connected to a cylinder pump or an
aspirator, for example, to draw the plating solution on the
substrate from the plating solution recovering nozzle 66.
[0048] As shown in FIGS. 5 through 7, the substrate holder 36 has a
disk-shaped substrate stage 68 and six vertical support arms 70
disposed at spaced intervals on the circumferential edge of the
substrate stage 68 for holding a substrate W in a horizontal plane
on respective upper surfaces of the support arms 70. A positioning
plate 72 is mounted on an upper end of one of the support arms 70
for positioning the substrate by contacting the end face of the
substrate. A pressing finger 74 is rotatably mounted on an upper
end of the support arm 70, which is positioned opposite to the
support arm 70 having the positioning plate 72, for abutting
against an end face of the substrate W and pressing the substrate W
to the positioning plate 72 when rotated. Chucking fingers 76 are
rotatably mounted on upper ends of the remaining four support arms
70 for pressing the substrate W downwardly and gripping the
circumferential edge of the substrate W.
[0049] The pressing finger 74 and the chucking fingers 76 have
respective lower ends coupled to upper ends of pressing pins 80
that are normally urged to move downwardly by coil springs 78. When
the pressing pins 80 are moved downwardly, the pressing finger 74
and the chucking fingers 76 are rotated radially inwardly into a
closed position. A support plate 82 is disposed below the substrate
stage 68 for engaging lower ends of the opening pins 80 and pushing
them upwardly.
[0050] When the substrate holder 36 is located in the substrate
transfer position A shown in FIG. 3, the pressing pins 80 are
engaged and pushed upwardly by the support plate 82, so that the
pressing finger 74 and the chucking fingers 76 rotate outwardly and
open. When the substrate stage 68 is elevated, the opening pins 80
are lowered under the resiliency of the coil springs 78, so that
the pressing finger 74 and the chucking fingers 76 rotate inwardly
and close.
[0051] As shown in FIGS. 8 and 9, the cathode section 38 comprises
an annular frame 86 fixed to upper ends of vertical support columns
84 mounted on the peripheral portion of the support plate 82 (see
FIG. 7), a plurality of, six in this embodiment, cathode contacts
88 attached to a lower surface of the annular frame 86 and
projecting inwardly, and an annular sealing member 90 mounted on an
upper surface of the annular frame 86 in covering relation to upper
surfaces of the cathode contacts 88. The sealing member 90 is
adapted to have an inner peripheral edge portion inclined inwardly
downwardly and progressively thin-walled, and to have an inner
peripheral end suspending downwardly.
[0052] When the substrate holder 36 has ascended to the plating
position B, as shown FIG. 3, the cathode contacts 88 are pressed
against the peripheral portion of the substrate W held by the
substrate holder 36 for thereby allowing electric current to pass
through the substrate W. At the same time, an inner peripheral end
portion of the sealing member 90 is brought into contact with an
upper surface of the periphery of the substrate W under pressure to
seal its contact portion in a watertight manner. As a result, the
plating solution supplied onto the upper surface (surface to be
plated) of the substrate W is prevented from seeping from the end
portion of the substrate W, and the plating solution is prevented
from contaminating the cathode contacts 88.
[0053] In this embodiment, the cathode section 38 is vertically
immovable, but rotatable in a body with the substrate holder 36.
However, the cathode section 38 may be arranged such that it is
vertically movable and the sealing member 90 is pressed against the
surface, to be plated, of the substrate W when the cathode section
38 is lowered.
[0054] As shown in FIGS. 10 and 11, the anode section 28 of the
electrode arm section 30 includes a housing 94 which is coupled via
a ball bearing to the free end of the pivot arm 26, and a porous
member 110 which is disposed such that it closes the bottom opening
of the housing 94. The housing 94 has at its lower end an
inwardly-projecting portion 94a, while the porous member 110 has at
its top a flange portion 110a. The porous member 110 is secured to
the housing 94 in such a state that a seal ring (not shown) is
interposed between the inwardly-projecting portion 94a and the
flange portion 110a. Thus, a hollow plating solution chamber 100 is
defined between the porous member 110 sealed its periphery with the
seal ring and the inner surface of the housing 94.
[0055] The porous member 110 is composed of porous ceramics such as
silicon carbide, alumina, SiC, mullite, zirconia, titania,
cordierite, aluminum nitride or vanadium oxide or a porous resin
such as a sintered compact of polypropylene or polyethylene, or a
sponge. A porosity of the porous member 110 is preferably not more
than 40%, and an average pore diameter is preferably not more than
100 .mu.m. A thickness of the porous member 110 is generally 1 to
20 mm, preferably 5 to 20 mm, more preferably 8 to 15 mm. The
porous member 110, in this embodiment, is constituted of porous
ceramics of alumina having a porosity of not more than 30%, and an
average pore diameter of not more than 100 .mu.m. The porous
ceramic plate per se is an insulator, but the porous member 110 is
constituted so as to have a smaller conductivity than the plating
solution by causing the plating solution to enter its interior
complicatedly and follow a considerably long path in the thickness
direction.
[0056] The porous member 110 is disposed in the plating solution
chamber 100 such that the porous member 110 has a high resistance.
Hence, the influence of the surface sheet resistance of the
substrate becomes a negligible degree. Consequently, the difference
in current density over the surface of the substrate due to
electrical resistance on the surface of the substrate W becomes
small, and the uniformity of the plated film over the surface of
the substrate improves.
[0057] In the plating solution chamber 100, an anode 98 is disposed
above the porous member 110, and a plating solution introduction
pipe 104 is disposed above the anode 98. The plating solution
introduction pipe 104 has a plating solution introduction port 104a
connected to a plating solution supply pipe 102 which extends from
the plating solution supply unit 18 (see FIG. 1). A plating
solution discharge port 94b provided in an upper plate of the
housing 94 is connected to a plating solution discharge pipe
106.
[0058] A manifold structure is employed for the plating solution
introduction pipe 104 so that the plating solution can be supplied
uniformly onto the surface to be plated of the substrate. In
particular, a large number of narrow tubes 112, communicating with
the plating solution introduction pipe 104, are connected to the
pipe 104 at predetermined positions along the long direction of the
pipe 104. Further, small holes are provided in the anode 98 and the
porous member 110 at positions corresponding to the narrow tubes
112. The narrow tubes 112 extend downwardly in the small holes and
reach the lower surface or its vicinity of the porous member
110.
[0059] Thus, the plating solution, introduced from the plating
solution supply pipe 102 into the plating solution introduction
pipe 104, passes through the narrow tubes 112 and reaches the
bottom of the porous member 110, and pass through the porous member
110 and fills the plating solution chamber 100, whereby the anode
98 is immersed in the plating solution. The plating solution is
discharged from the plating solution discharge pipe 106 by
application of suction to the plating solution discharge pipe
106.
[0060] In order to suppress slime formation, the anode 98 is made
of copper (phosphorus-containing copper) containing 0.03 to 0.05%
of phosphorus. It is also possible to use an insoluble material for
the anode 98.
[0061] The cathode contacts 88 are electrically connected to the
negative pole of a plating power source, and the anode 98 is
electrically connected to the positive pole of the plating power
source.
[0062] When carrying out electroplating, the substrate holder 36 is
positioned at the plating position B (see FIG. 3). The anode
section 28 is lowered until the processing position where the
distance between the substrate W held by the substrate holder 36
and the porous member 110 becomes, e.g., about 0.1 to 3 mm. A
plating solution is supplied from the plating solution supply pipe
102 to the upper surface (surface to be plated) of the substrate W
while impregnating the porous member 110 with the plating solution
and filling the plating solution chamber 100 with the plating
solution. Then, the cathode contacts 88 are electrically connected
to the negative pole of a plating power source and the anode 98 is
electrically connected to the positive pole of the plating power
source so as to carry out plating of the surface to be plated of
the substrate W.
[0063] As shown in FIG. 12, a porous member cleaning section 120
for cleaning the porous member 110 of the anode section 28 is
provided in association with the plating solution tray 22. In this
embodiment, a hermetic space is formed in the plating solution tray
22 by covering the opening of the plating solution tray 22 with the
anode section 28, and the porous member 110, defining the hermetic
space, is cleaned with a cleaning liquid supplied from the porous
member cleaning section 120 into the plating solution tray 22 and,
in addition, the cleaning liquid remaining in the porous member 110
is replaced with pure water (rinsing liquid) supplied from the
porous member cleaning section 120 into the plating solution tray
22.
[0064] In particular, a flange portion 94c is provided at the top
of the housing 94 of the anode section 28, while a seal ring 122 is
provided in the upper surface of the plating solution tray 22 at a
position to be in contact with the flange portion 94c. When the
anode section 28 is lowered, the flange portion 94c comes into
pressure contact with the seal ring 122 in the upper surface of the
plating solution tray 22, whereby the plating solution tray 22 is
sealed by the seal ring 122, forming a hermetic space.
[0065] The porous member cleaning section 120 includes a cleaning
liquid tank 126 for storing a cleaning liquid 124 which is, for
example, sulfuric acid, nitric acid, hydrofluoric acid,
hydrochloric acid, a hydrogen peroxide solution, pure water, or a
mixed solution thereof, an alkaline cleaning liquid or a neutral
detergent, or a combination thereof, a cleaning liquid supply pipe
128 for supplying the cleaning liquid 124 in the cleaning liquid
tank 126 to the plating liquid tray 22, and a cleaning liquid
discharge pipe 130, which is to be connected selectively to the
plating solution introduction inlet 104a or to the plating solution
discharge outlet 94b, for discharging the cleaning liquid or the
like in the housing 94. The cleaning liquid supply pipe 128 is
provided with a squeeze pump 132 and a filter 134, and the cleaning
liquid discharge pipe 130 is provided with a liquid feeding pump
136.
[0066] An overflow tank 22b, defined by an overflow weir 22a, is
provided in the plating solution tray 22. The cleaning liquid,
which has flowed into the overflow tank 22b, is either returned,
via a three-way valve 138a and a return pipe 140, to the cleaning
liquid tank 126 or discharged out via the three-way valve 138a and
a waste liquid pipe 142. Similarly, the cleaning liquid flowing in
the cleaning liquid discharge pipe 130 is either returned, via a
three-way valve 138b and a return pipe 144, to the cleaning liquid
tank 126 or discharged out via the three-way valve 138b and a waste
liquid pipe 146. The cleaning liquid supply pipe 128 is selectively
connected, via a three-way valve 138c upstream of the squeeze pump
132, to a pure water pipe 148 for supplying pure water as a rinsing
liquid, and is selectively connected, via a three-way valve 138d
downstream of the filter 134, to a waste liquid pipe 150. When pure
water is used as a cleaning liquid for the porous member, the
cleaning operation can be carried out solely with the pure water
pipe 148 without the above switching of pipes.
[0067] The operation of the porous member cleaning section 120 upon
cleaning of the porous member 110 of the anode section 28 will now
be described.
[0068] First, the anode section 28 is positioned at the idling
position above the plating solution tray 22. The anode section 28
is then lowered to bring the flange portion 94c of the anode
section 28 into pressure contact with the seal ring 122 in the
upper surface of the plating solution tray 22, thereby sealing the
peripheral portion of the plating solution tray 22 with the seal
ring 122. The plating solution tray 22 has previously been emptied
of the plating solution, and the plating solution introduction
inlet 104a and the plating solution discharge outlet 94b have been
connected to the cleaning liquid discharge pipe 130.
[0069] Next, the squeeze pump 132 is driven to pressurize the
cleaning liquid 124 and supply the cleaning liquid 124 from the
cleaning liquid tank 126 to the plating solution tray 22, and the
liquid feeding pump 136 is driven, for example, at a time point
when the plating solution tray 22 has become filled with the
cleaning liquid, to discharge the cleaning liquid, initially
containing a plating solution, from the housing 94. Thus, the
pressurized cleaning liquid 124, which has flowed into the plating
solution tray 22, is allowed to pass through the interior of the
porous member 110 and flow into the housing 94, thereby cleaning
the interior (interior surfaces of pores) of the porous member 110
with the cleaning liquid 124. By thus directly cleaning the
interior (interior surfaces of pores) of the porous member 110 with
the cleaning liquid 124 passing through the interior, the interior
of the porous member 110 can be cleaned with good efficiency even
when the porous member 110 has a high density and a large volume.
According to the present invention, it is also possible to apply
ultrasonic waves to at least one of the porous member 110, the
cleaning liquid 124 and the porous member cleaning section 120,
during cleaning of the porous member 110 with the pressurized
cleaning liquid 124, so as to increase the cleaning efficiency.
[0070] When the cleaning liquid, discharged through the cleaning
liquid discharge pipe 130, contains a plating solution, the
cleaning liquid is discharged out via the three-way valve 138b and
the waste liquid pipe 146 and, when the cleaning liquid has come to
contain no plating solution, the cleaning liquid is returned, via
the three-way valve 138b and the return pipe 144, to the cleaning
liquid tank 126 and is allowed to circulate. The flow rate of the
cleaning liquid during the cleaning is, for example, 10 to 20
L/min.
[0071] After cleaning the porous member 110 with the cleaning
liquid 124 for a predetermined time, the supply of the cleaning
liquid 124 to the plating solution tray 22 is stopped. The cleaning
time is, for example, about 3 hours when sulfuric acid is used as
the cleaning liquid. Thereafter, the cleaning liquid remaining in
the plating solution tray 22 is withdrawn from the tray 22 through
the cleaning liquid supply pipe 128 and the waste liquid pipe 150,
while the cleaning liquid in the overflow tank 22b is returned
through the return pipe 140 to the cleaning tank 126.
[0072] Next, the pure water pipe 148 is connected via the three-way
valve 138c to the cleaning liquid supply pipe 128. The squeeze pump
132 is driven to supply pressurized pure water as a rinsing liquid
into the plating solution tray 22, and the liquid feeding pump 136
is driven, for example, at a time point when the plating solution
tray 22 has become filled with pure water, to discharge pure water,
initially containing the cleaning liquid, from the housing 94. At
the same time, pure water, which has been supplied into the plating
solution tray 22 and passed through the interior of the porous
member 110, and pure water, which has flowed into the overflow tank
22b, are discharged as waste through the waste liquid pipes 142,
146.
[0073] Thus, the pressurized pure water, which has flowed into the
plating solution tray 22, is allowed to pass through the interior
of the porous member 110 and flow into the housing 94, thereby
replacing the cleaning liquid, remaining in the interior of the
porous member 110, with pure water. By thus replacing the cleaning
liquid, remaining in the interior of the porous member 110, with
pure water, adverse effects of the cleaning liquid on plating can
be prevented.
[0074] During the pure water rinsing (pure water replacement), the
electric conductivity of pure water that has passed through the
interior of the porous member 110 is monitored and, when the
electric conductivity has reached a predetermined value, the supply
of pure water to the plating solution tray is stopped, thereby
terminating the replacement operation. Thereafter, pure water,
remaining in the plating solution tray 22, is withdrawn from the
tray 22 through the cleaning liquid supply pipe 128 and the waste
liquid pipe 150. It is also possible to terminate the replacement
operation after elapse of a predetermined time period determined,
e.g., by experiment.
[0075] Next, ordinary idling is carried out. In particular, while
introducing a plating solution into the plating solution tray 22
and keeping the porous member 110 immersed in the plating solution
in the plating solution tray 22, the plating solution in the
housing 94 is withdrawn and circulated, thereby carrying out
replacement of the plating solution in the housing 94 and defoaming
of the plating solution.
[0076] By incorporating the porous member cleaning section 120 for
cleaning the porous member 110 integrally into the plating
apparatus 12 having the porous member 110, according to this
embodiment, the porous member 110 can be cleaned periodically or
according to necessity without taking the porous member 110 out of
the plating apparatus 12. Further, by carrying out cleaning of the
porous member 110 at the idling position with the cleaning liquid
supplied to the plating solution tray 22 for storing a plating
solution for use in idling, a significant increase in the size of
the plating apparatus can be avoided.
[0077] It is also possible to separately provide a cleaning liquid
tray, e.g., beside the plating solution tray, to move the anode
section to above the cleaning liquid tray and then lower the anode
section so as to cover the opening of the cleaning liquid tray with
the anode section, thereby forming a hermetic space in the cleaning
liquid tray, and to carry out cleaning of the porous member of the
anode section, in substantially the same manner as described above,
by sequentially supplying a pressurized cleaning liquid and
pressurized pure water (rinsing liquid) to the cleaning liquid
tray. A pure water rinsing tray may also be provided separately
from the cleaning liquid tray for cleaning in order to save time
taken for replacing a chemical solution with pure water in the
cleaning liquid tray and save the amount of liquid supplied, or to
facilitate reuse of the cleaning liquid.
[0078] The operation of the above-described substrate processing
apparatus will now be described.
[0079] First, a substrate W to be plated is taken out from one of
the loading/unloading units 10 by the transfer robot 14, and
transferred, with a surface to be plated facing upwardly, through
the substrate carry-in and carry-out opening defined in the side
panel, into one of the plating apparatuses 12. At this time, the
substrate holder 36 is in the lower substrate transfer position A.
After the hand of the transfer robot 14 has reached a position
directly above the substrate stage 68, the hand of the transfer
robot 14 is lowered to place the substrate W on the support arms
70. The hand of the transfer robot 14 is then retracted through the
substrate carry-in and carry-out opening.
[0080] After the hand of the transfer robot 14 is retracted, the
cup 40 is elevated. Then, the substrate holder 36 is lifted from
the substrate transfer position A to the pretreatment/cleaning
position C. As the substrate holder 36 ascends, the substrate W
placed on the support arms 70 is positioned by the positioning
plate 72 and the pressing finger 74, and then reliably gripped by
the chucking fingers 76.
[0081] On the other hand, the anode section 28 of the electrode arm
section 30 is in the idling position over the plating solution tray
22 now, and the porous member 110 and the anode 98 is positioned in
the plating solution tray 22. At the same time that the cup 40
ascends, the plating solution starts being supplied to the plating
solution tray 22 and the anode section 28. Until the step of
plating the substrate W is initiated, the new plating solution is
supplied, and the plating solution discharge pipe 106 is evacuated
to replace the plating solution in the porous member 110 and remove
air bubbles (idling) from the plating solution in the porous member
110. When the ascending movement of the cup 40 is completed, the
substrate carry-in and carry-out openings in the side panel are
closed by the cup 40, isolating the atmosphere in the side panel
and the atmosphere outside of the side panel from each other.
[0082] When the cup 40 is elevated, the pre-coating step is
initiated. Specifically, the substrate holder 36 that has received
the substrate W is rotated, and the pre-coating/recovering arm 32
is moved from the retracted position to a position confronting the
substrate W. When the rotational speed of the substrate holder 36
reaches a preset value, the pre-coating nozzle 64, mounted on the
tip end of the pre-coating/recovering arm 32, intermittently
discharges a pre-coating liquid which comprises a surface active
agent, for example, toward the surface to be plated of the
substrate W. At this time, since the substrate holder 36 is
rotating, the pre-coating liquid spreads all over the surface to be
plated of the substrate W. Then, the pre-coating/recovering arm 32
is returned to the retracted position, and the rotational speed of
the substrate holder 36 is increased to spin the pre-coating liquid
off and dry the surface to be plated of the substrate W.
[0083] After the completion of the pre-coating step, the plating
step is initiated. First, the substrate holder 36 is stopped
against rotation, or the rotational speed thereof is reduced to a
preset rotational speed for plating. In this state, the substrate
holder 36 is lifted to the plating position B. When the peripheral
portion of the substrate W is brought into contact with the cathode
contacts 88, it is possible to pass an electric current, and at the
same time, the sealing member 90 is pressed against the upper
surface of the peripheral portion of the substrate W, thus sealing
the peripheral portion of the substrate W in a watertight
manner.
[0084] Based on a signal indicating that the pre-coating step for
the loaded substrate W is completed, the electrode arm section 30
is swung in a horizontal direction to displace the anode section 28
from a position over the plating solution tray 22 to a position
over the plating processing position. After the anode section 28
reaches this position, the anode section 28 is lowered toward the
cathode section 38. At this time, the porous member 110 does not
contact with the surface to be plated of the substrate W, but is
held closely to the surface to be plated of the substrate W at a
distance ranging from 0.1 mm to 3 mm. When the descent of the anode
section 28 is completed, the cathode contacts 88 are connected to
the negative pole of the plating power source and the anode 98 is
connected to the positive pole of the plating power source so as to
initiate the plating process. The substrate holder 36 may be
rotated at low speed during plating, if necessary.
[0085] When the plating process is completed, the electrode arm
section 30 is raised and then swung to return the anode section 28
to the position above the plating solution tray 22 and to lower to
the idling position. Then, the pre-coating/recovering arm 32 is
moved from the retreat position to the position confronting to the
substrate W, and lowered to recover the remainder of the plating
solution on the substrate W by a plating solution recovering nozzle
66. After recovering of the remainder of the plating solution is
completed, the pre-coating/recovering arm 32 is returned to the
retreat position, and pure water is supplied from the fixed nozzle
34 for supplying pure water toward the central portion of the
substrate W for rinsing the plated surface of the substrate. At the
same time, the substrate holder 36 is rotated at an increased speed
to replace the plating solution on the surface of the substrate W
with pure water. Rinsing the substrate W in this manner prevents
the splashing plating solution from contaminating the cathode
contacts 88 of the cathode section 38 during descent of the
substrate holder 36 from the plating position B.
[0086] After completion of the rinsing, the washing with water step
is initiated. That is, the substrate holder 36 is lowered from the
plating position B to the pretreatment/cleaning position C. Then,
while pure water is supplied from the fixed nozzle 34 for supplying
pure water, the substrate holder 36 and the cathode section 38 are
rotated to perform washing with water. At this time, the sealing
member 90 and the cathode contacts 88 can also be cleaned,
simultaneously with the substrate W, by pure water directly
supplied to the cathode section 38, or pure water scattered from
the surface of the substrate W.
[0087] After washing with water is completed, the drying step is
initiated. That is, supply of pure water from the fixed nozzle 34
is stopped, and the rotational speed of the substrate holder 36 and
the cathode section 38 is further increased to remove pure water on
the surface of the substrate W by centrifugal force and to dry the
surface of the substrate W. The sealing member 90 and the cathode
contacts 88 are also dried at the same time. Upon completion of the
drying, the rotation of the substrate holder 36 and the cathode
section 38 is stopped, and the substrate holder 36 is lowered to
the substrate transfer position A. Thus, the gripping of the
substrate W by the chucking fingers 76 is released, and the
substrate W is just placed on the upper surfaces of the support
arms 70. At the same time, the cup 40 is also lowered.
[0088] All the steps including the plating step, the pretreatment
step accompanying to the plating step, the cleaning step, and the
drying step are now finished. The transfer robot 14 inserts its
hand through the substrate carry-in and carry-out opening into the
position beneath the substrate W, and raises the hand to receive
the plated substrate W from the substrate holder 36. Then, the
transfer robot 14 returns the plated substrate W received from the
substrate holder 36 to one of the loading/unloading units 10.
[0089] The porous member 110 of the anode section 28 is cleaned by
using the porous member cleaning section 120 either periodically or
after processing a predetermined number of substrates, for example.
In particular, after the completion of the plating process, the
electrode arm section 30 is raised and pivoted to return the anode
section 28 to above the plating solution tray 22. The anode section
28 is then lowered to below the idling position so as to seal the
peripheral portion of the anode section 28 with the seal ring 122.
The plating solution has previously been withdrawn from the plating
solution tray 22. A high-pressure cleaning liquid and high-pressure
pure water are sequentially introduced into the plating solution
tray 22 form the porous member cleaning section 120 in the
above-described manner, thereby cleaning the interior of the porous
member 110 of the anode section 28 and replacing the cleaning
liquid remaining in the interior of the porous member 110 with pure
water (rinsing liquid). After completion of the cleaning of the
porous member 110, the next plating processing will be started.
[0090] FIG. 13 schematically shows a porous member cleaning
apparatus according to an embodiment of the present invention,
which can be used to clean, e.g., the porous member 110 provided in
the plating apparatus 12 after taking the porous member 110 out of
the plating apparatus 12. The porous member cleaning apparatus
includes an upwardly-open hermetically-sealable hermetic vessel
200, a ring-shaped holder member 202 attached to an upper portion
of the hermetic vessel 200, and a lid 204 which is detachable or
openable/closable and water-tightly covers the top of the hermetic
vessel 200.
[0091] The holder member 202 is to hold the porous member 110 by
dropping it into the opening of the holder member 202 and to close
an opening of the hermetic vessel 200 with the porous member 110. A
seal ring 206 is mounted to the upper surface of the holder member
202 at a position where the seal ring 206 surrounds the porous
member 110. The cleaning apparatus also includes a ring-shaped
retainer plate 208 having such a width as to cover the seal ring
206 and a peripheral region of the porous member 110 held by the
holder member 202. After dropping the porous member 110 into the
opening of the holder member 202, the retainer plate 208 is brought
into pressure contact with the peripheral region of the upper
surface of the porous member 110 while squashing the seal ring 206
by the retainer plate 208, and the retainer plate 208 is fixed to
the holder member 202 by a fixture 210, such as a bolt. A hermetic
space peripherally sealed with the seal ring 206, with the opening
closed with the porous member 110, is thus formed in the hermetic
vessel 200.
[0092] To the bottom of the hermetic vessel 200 is connected a
cleaning liquid supply pipe 216 as a pressurized fluid injection
section, extending from a cleaning liquid tank 214 for storing
therein a cleaning liquid 212. The cleaning liquid supply pipe
(pressurized fluid injection section) 216 is provided with a
squeeze pump 218 and a filter 220. The cleaning liquid supply pipe
216 is capable of being selectively connected to a pure water pipe
224 via a three-way valve 222a upstream of the squeeze pump 218. To
the bottom of the hermetic vessel 200 is also connected a gas
supply pipe 226 for supplying an inert gas, such as N.sub.2, to a
liquid (cleaning liquid and/or pure water) in the hermetic vessel
200 for bubbling of the liquid.
[0093] A cleaning liquid discharge pipe 228 as a fluid discharge
section is connected to the lid 204. The cleaning liquid discharge
pipe (fluid discharge section) 228 is to be selectively connected
via a three-way valve 222b to one of a waste liquid pipe 232 and a
return pipe 230 connected to the cleaning liquid tank 214.
[0094] The operation of the porous member cleaning apparatus upon
cleaning of the porous member 110 will now be described.
[0095] First, with the lid 204 detached or open, the porous member
110 is dropped into the opening of the holder member 202 and the
retainer plate 208 is fixed to the holder member 202 by the fixture
210, thereby forming a hermetic space peripherally sealed with the
seal ring 206, with the opening closed with the porous member 110,
in the hermetic vessel 200. The lid 204 is then attached or
closed.
[0096] Thereafter, the squeeze pump 218 is driven to pressurize the
cleaning liquid 212 and feed the liquid sequentially from the
cleaning liquid tank 214 into the hermetic vessel 200. As with the
above-described embodiment, the flow rate of the cleaning liquid
is, for example, 10 to 20 L/min. At the same time, an inert gas,
such as N.sub.2, is supplied from the gas supply pipe 226 into the
cleaning liquid, which has been fed into the hermetic vessel 200,
to bubble the liquid. The pressurized cleaning liquid is thus
allowed to pass through the interior of the porous member 110 and
reach to above the porous member 110, thereby cleaning the interior
of the porous member 110 with the cleaning liquid. Specially, by
allowing the cleaning liquid, which is bubbled with the gas, to
pass through the interior of the porous member 110, according to
this embodiment, particles, etc. adhering to the interior of the
porous member 110, i.e., the interior surfaces of pores, can be
securely peeled off and removed from the interior pore
surfaces.
[0097] During the cleaning, the cleaning liquid, which has reached
to above the porous member 110 and has accumulated inside the lid
204, is discharged through the cleaning liquid discharge pipe 228.
When the cleaning liquid, discharged through the cleaning liquid
discharge pipe 228, contains a plating solution, the cleaning
liquid is discharged out via the three-way valve 222b and the waste
liquid pipe 232 and, when the cleaning liquid has come to contain
no plating solution, the cleaning liquid is returned, via the
three-way valve 222b and the return pipe 230, to the cleaning
liquid tank 214 and is allowed to circulate. After cleaning the
porous member 110 with the cleaning liquid 212 for a predetermined
time, the supply of the cleaning liquid 212 to the hermetic vessel
200 is stopped.
[0098] Next, the pure water pipe 224 is connected via the three-way
valve 222a to the cleaning liquid supply pipe 216, and pressurized
pure water as a rinsing liquid is supplied into the hermetic vessel
200 at a flow rate of 10 to 20 L/min, so that the pressurized pure
water is allowed to pass through the interior of the porous member
110 and reach to above the porous member 110, thereby replacing the
cleaning liquid remaining in the interior of the porous member 110
with pure water. As with the cleaning liquid, the pure water, which
has been supplied into the hermetic vessel 200, may be bubbled with
an inert gas, such as N.sub.2, supplied from the gas supply pipe
226. The liquid discharged out of the lid 204 during the pure water
replacement is discharged to the outside from the waste liquid pipe
146.
[0099] After completion of the pure water replacement operation,
the driving of the squeeze pump 218 is stopped, and the liquid
remaining inside the lid 204 is removed. The lid 204 is then either
detached or opened. Thereafter, the retainer plate 208 is detached,
and the porous member 110 after cleaning is taken out of the holder
member 202 to reuse the porous member 110 in, e.g., a plating
apparatus.
[0100] FIG. 14 shows a porous member cleaning apparatus according
to another embodiment of the present invention. This embodiment
differs from the embodiment shown in FIG. 13 in that the cleaning
liquid supply pipe (pressurized fluid supply section) 216 is
connected to the lid 204 and the cleaning liquid discharge pipe
(fluid discharge section) 228 is connected to the hermetic vessel
200, so that a pressurized cleaning liquid and pressurized pure
water are sequentially supplied into the region (hermetic space)
surrounded by the porous member 110, the holder member 202 and the
lid 204 and are passed through the interior of the porous member
110, and the cleaning liquid or pure water, which has passed
through the interior of the porous member 110 and accumulated
inside the lid 200, is either discharged as waste or reused. The
other construction of this embodiment is substantially the same as
the embodiment shown in FIG. 13, hence a description thereof is
omitted.
[0101] While the present invention has been described with
reference to the preferred embodiments thereof, it is understood
that the present invention is not limited to the particular
embodiments, but various modifications may be made therein within
the technical concept of the invention.
* * * * *