U.S. patent application number 14/296366 was filed with the patent office on 2014-12-11 for copper electroplating apparatus.
The applicant listed for this patent is EBARA CORPORATION. Invention is credited to Masaaki KIMURA, Junichiro TSUJINO, Mitsutoshi YAHAGI.
Application Number | 20140360865 14/296366 |
Document ID | / |
Family ID | 52004541 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360865 |
Kind Code |
A1 |
KIMURA; Masaaki ; et
al. |
December 11, 2014 |
COPPER ELECTROPLATING APPARATUS
Abstract
A copper electroplating apparatus is disclosed. The copper
electroplating apparatus includes: a plating bath configured to
hold a plating solution therein; a soluble anode of
phosphorus-containing copper; a substrate holder configured to hold
a substrate; an anode bag that surrounds the anode, the anode bag
being formed of mesh; a regulation plate configured to regulate an
electric field, the regulation plate having an opening and being
disposed between the anode and the substrate held by the substrate
holder; and a diaphragm disposed so as to dose the opening of the
regulation plate, the diaphragm being configured to allow
permeation of metal ions therethrough and not allow permeation of
additives contained in the plating solution.
Inventors: |
KIMURA; Masaaki; (Tokyo,
JP) ; YAHAGI; Mitsutoshi; (Tokyo, JP) ;
TSUJINO; Junichiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EBARA CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
52004541 |
Appl. No.: |
14/296366 |
Filed: |
June 4, 2014 |
Current U.S.
Class: |
204/198 |
Current CPC
Class: |
C25D 17/008 20130101;
C25D 3/38 20130101; C25D 17/001 20130101; C25D 17/10 20130101; C25D
17/002 20130101; C25D 17/12 20130101; C25D 21/10 20130101 |
Class at
Publication: |
204/198 |
International
Class: |
C25D 17/12 20060101
C25D017/12; C25D 7/12 20060101 C25D007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 2013 |
JP |
2013-119744 |
Claims
1. A copper electroplating apparatus comprising: a plating bath
configured to hold a plating solution therein; a soluble anode of
phosphorus-containing copper to be immersed in the plating solution
held in the plating bath; a substrate holder configured to hold a
substrate and dispose the substrate at a position opposite the
anode while immersing the substrate in the plating solution held in
the plating bath; a substrate holder transport device configured to
transport the substrate holder holding the substrate; an anode bag
that surrounds the anode, the anode bag being formed of mesh; a
regulation plate configured to regulate an electric field, the
regulation plate having an opening and being disposed between the
anode and the substrate held by the substrate holder; and a
diaphragm disposed so as to close the opening of the regulation
plate, the diaphragm being configured to allow permeation of metal
ions therethrough and not allow permeation of additives contained
in the plating solution.
2. The copper electroplating apparatus according to claim 1,
wherein the anode of phosphorus-containing copper has a phosphorus
concentration in a range of 1800 to 2700 ppm by mass and an average
copper grain size in a range of 15 .mu.m to 45 .mu.m.
3. The copper electroplating apparatus according to claim 2,
wherein the average copper grain size is in a range of 30 .mu.m to
40 .mu.m.
4. The copper electroplating apparatus according to claim 1,
further comprising: a shield box which separates as interior of the
plating bath into an anode chamber in which the anode is disposed
and a cathode chamber in which the substrate, held by the substrate
holder, is disposed, wherein the anode bag and the diaphragm are
disposed in the anode chamber, and the shield box has an opening,
which is closed with the diaphragm, at a position opposite the
opening of the regulation plate.
5. The copper electroplating apparatus according to claim 4,
further comprising: a bubbling device configured to form bubbles in
the plating solution held in the anode chamber.
6. The copper electroplating apparatus according to claim 1,
wherein the diaphragm is formed of a cation exchange membrane or a
porous membrane.
7. A copper electroplating apparatus comprising: a plating bath
configured to hold a plating solution therein; a soluble anode of
phosphorus-containing copper to be immersed in a plating solution
held in the plating bath; a substrate holder configured to hold a
substrate and dispose the substrate at a position opposite the
anode while immersing the substrate in the plating solution held in
the plating bath; a substrate holder transport device configured to
transport the substrate holder holding the substrate; a first anode
bag that surrounds the anode, the first anode bag being formed of
mesh; a second anode bag that surrounds the first anode bag, the
second anode bag being formed of mesh which is finer than the first
anode bag; and a regulation plate configured to regulate an
electric field, the regulation plate having an opening and being
disposed between the anode and the substrate held by the substrate
holder.
8. The copper electroplating apparatus according to claim 7,
further comprising: a shield box which separates an interior of the
plating bath into an anode chamber in which the anode is disposed
and a cathode chamber in which the substrate, held by the substrate
holder, is disposed, wherein the first anode bag and the second
anode bag are disposed in the anode chamber, and the shield box has
an opening, which is closed with a diaphragm, at a position
opposite the opening of the regulation plate.
9. The copper electroplating apparatus according to claim 8,
further comprising: a bubbling device configured to form bubbles in
the plating solution held in the anode chamber.
10. A copper electroplating apparatus comprising; a plating bath
configured to hold a plating solution therein; a soluble anode of
phosphorus-containing copper to be immersed in a plating solution
in the plating bath; a substrate holder configured to hold a
substrate and dispose the substrate at a position opposite the
anode while immersing the substrate in the plating solution in the
plating bath; a substrate holder transport device configured to
transport the substrate holder holding the substrate; a regulation
plate configured to regulate an electric field, the regulation
plate having an opening and being disposed between the anode and
the substrate held by the substrate holder; a diaphragm disposed so
as to dose the opening of the regulation plate, the diaphragm being
configured to allow permeation of metal ions therethrough and not
allow permeation of additives contained in the plating solution; a
shield box which separates an interior of the plating bath into an
anode chamber in which the anode and the diaphragm are disposed and
a cathode chamber in which the substrate, held by the substrate
holder, is disposed, the shield box having an opening, which is
closed with the diaphragm, at a position opposite the opening of
the regulation plate; and a plating solution discharge line
configured to discharge the plating solution from a bottom of the
anode chamber.
11. The copper electroplating apparatus according to claim 10,
wherein the diaphragm is formed of a cation exchange membrane or a
porous membrane.
12. The copper electroplating apparatus according to claim 10,
further comprising: a bubbling device configured to form bubbles in
the plating solution held in the anode chamber.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Japanese Patent
Application No. 2013-119744 filed Jun. 6, 2013, the entire contents
of which are hereby incorporated by reference.
BACKGROUND
[0002] A soluble anode made of phosphorus-containing copper
(hereinafter referred to as "phosphorus-containing copper anode")
is widely used in a known type of copper electroplating apparatus
which performs copper plating of a substrate surface by immersing a
substrate such as a semiconductor wafer, held by a substrate
holder, in a plating solution. When using a phosphorus-containing
copper anode, it is common practice to perform dummy plating by
applying a voltage between a dummy substrate and the
phosphorus-containing copper anode to produce a thin film, called a
black film, uniformly on the surface of the phosphorus-containing
copper anode before applying a voltage between a substrate and the
phosphorus-containing copper anode to perform copper plating of the
substrate surface. This operation can suppress the production of
monovalent copper, thereby preventing formation of sludge.
[0003] When copper plating is performed with the use of the
phosphorus-containing copper anode, a black film may peel off the
surface of the anode during the progress of copper plating and may
be suspended in a plating solution. The black film suspended in the
plating solution, if it is attached to a substrate, may cause a
defect in the substrate.
[0004] To address the problem, an apparatus has been proposed in
which an enclosure is formed by an anode cup and a membrane, and an
anode (ion source material) is disposed in the enclosure (see U.S.
Pat. No. 6,126,798).
[0005] A plating apparatus has been proposed which comprises an
anode chamber and a cathode chamber that are separated by a porous
transmissive bather of a multi-layer structure which allows
permeation of metal ions therethrough but does not allow permeation
of non-ionic organic additives (see U.S. Pat. No. 6,527,920). A
plating apparatus has also been proposed which uses an anode having
an average grain size of at least 50 .mu.m and containing
phosphorus in a concentration of at least 200 ppm, and uses a
membrane which separates an anode chamber and a cathode chamber and
which allows permeation of metal ions therethrough while preventing
permeation of particles larger than 0.05 .mu.m (see U.S. Pat. No.
6,821,407).
[0006] A method for producing an anode which has an average grain
size of not more than 30 .mu.m and can prevent detachment of a
black film has been proposed. This method involves the steps of
subjecting a phosphorus-containing copper ingot, having a copper
purity of at least 99.99%, a phosphorus concentration of 300 to
1000 ppm and an oxygen content of not more than 10 ppm, to hot
forging at an initial temperature of 600 to 900.degree. C. (see
Japanese laid-open patent publication No. 2012-57186). Further, a
technique has been proposed which involves the steps of bubbling an
electrolytic solution in an anode bag, in which an anode is housed,
with air or oxygen gas so as to keep the amount of dissolved oxygen
in the electrolytic solution at a level of not less than 5 ppm,
thereby preventing the growth/detachment of a black film on/from
the surface of the anode (see Japanese laid-open patent publication
No. 201146973).
[0007] It is generally difficult to produce a firm black film in a
manner as not to peel off the underlying surface of the
phosphorus-containing copper anode. Moreover, use of a fairly
complicated construction is generally required in order to prevent
a black film, which has peeled off a phosphorus-containing copper
anode, from adhering to a substrate. In particular, a very
complicated structure will be needed to completely prevent a black
film from adhering to a substrate.
SUMMARY OF THE INVENTION
[0008] It is therefore a first object to provide a copper
electroplating apparatus which can stably retain a black film on a
surface of a soluble anode of phosphorus-containing copper, thereby
minimizing an amount of the black film that peels of the soluble
anode.
[0009] It is a second object to provide a copper electroplating
apparatus which, even if a black film peels off a soluble anode of
phosphorus containing copper, can prevent the black film from being
attached to a substrate more reliably with a relatively simple
construction.
[0010] Embodiments, which will be described below, relates to a
copper electroplating apparatus, and more particularly to a copper
electroplating apparatus in which a substrate such as a
semiconductor wafer, held by a substrate holder, is immersed in a
plating solution to form e.g., connecting bumps or interconnects of
copper on a surface of the substrate, or to perform through-hole
copper plating of the substrate.
[0011] In an embodiment, a copper electroplating apparatus
comprises: a plating bath configured to hold a plating solution
therein; a soluble anode of phosphorus-containing copper to be
immersed in the plating solution held in the plating bath; a
substrate holder configured to hold a substrate and dispose the
substrate at a position opposite the anode while immersing the
substrate in the plating solution held in the plating bath; a
substrate holder transport device configured to transport the
substrate holder holding the substrate; an anode bag that surrounds
the anode, the anode bag being formed of mesh; a regulation plate
configured to regulate an electric field, the regulation plate
having an opening and being disposed between the anode and the
substrate held by the substrate holder; and a diaphragm disposed so
as to close the opening of the regulation plate, the diaphragm
being configured to allow permeation of metal ions therethrough and
not allow permeation of additives contained in the plating
solution.
[0012] Even if a black film peels off the soluble anode of
phosphorus-containing copper (phosphorus-containing copper anode)
and floats in the plating solution, the movement of the black film
toward the substrate can be doubly blocked by the anode bag and the
diaphragm. This makes it possible to substantially completely
prevent the black film from attaching to the surface of the
substrate.
[0013] In an embodiment, the anode of phosphorus-containing copper
has a phosphorus concentration in a range of 1800 to 2700 ppm by
mass and an average copper grain size in a range of 15 .mu.m to 45
.mu.m.
[0014] It has been verified from an experiment that a firm black
film, having a uniform thickness and which hardly peels off, is
produced on the surface of an anode made of phosphorus-containing
copper (or a phosphorus-containing copper anode) when the anode has
a phosphorus concentration in the range of 1800 to 2700 ppm,
preferably in the range of 2000 to 2700 ppm.
[0015] In an embodiment, a copper electroplating apparatus
comprising: plating bath configured to hold a plating solution
therein; a soluble anode of phosphorus-containing copper to be
immersed in a plating solution held in the plating bath; a
substrate holder configured to hold a substrate and dispose the
substrate at a position opposite the anode while immersing the
substrate in the plating solution held in the plating bath; a
substrate holder transport device configured to transport the
substrate holder holding the substrate; a first anode bag that
surrounds the anode, the first anode bag being formed of mesh; a
second anode bag that surrounds the first anode bag, the second
anode bag being formed of mesh which is finer than the first anode
bag; and a regulation plate configured to regulate an electric
field, the regulation plate having an opening and being disposed
between the anode and the substrate held by the substrate
holder.
[0016] Even if a black film peels of the soluble anode of
phosphorus-containing copper (phosphorus-containing copper anode)
and floats in the plating solution, the movement of the black film
toward the substrate can be doubly blocked by the first anode bag
and the second anode bag. This makes it possible to substantially
completely prevent the black film from attaching to the surface of
the substrate.
[0017] In an embodiment, a copper electroplating apparatus
comprising: a plating bath configured to hold a plating solution
therein; a soluble anode of phosphorus-containing copper to be
immersed in a plating solution in the plating bath; a substrate
holder configured to hold a substrate and dispose the substrate at
a position opposite the anode while immersing the substrate in the
plating solution in the plating bath; a substrate holder transport
device configured to transport the substrate holder holding the
substrate; a regulation plate configured to regulate an electric
field, the regulation plate having an opening and being disposed
between the anode and the substrate held by the substrate holder; a
diaphragm disposed so as to close the opening of the regulation
plate, the diaphragm being configured to allow permeation of metal
ions therethrough and not allow permeation of additives contained
in the plating solution; a shield box which separates an interior
of the plating bath into an anode chamber in which the anode and
the diaphragm are disposed and a cathode chamber in which the
substrate, held by the substrate holder, is disposed, the shield
box having an opening, which is closed with the diaphragm, at a
position opposite the opening of the regulation plate; and a
plating solution discharge line configured to discharge the plating
solution from a bottom of the anode chamber.
[0018] Even if a black film peels off the soluble anode of
phosphorus-containing copper (phosphorus-containing copper anode)
and floats in the plating solution, the plating solution,
containing the black film can be discharged from the bottom of the
anode chamber. In addition, the diaphragm can block the floating
black film from moving from the anode chamber into the cathode
chamber. Thus, the black film can be substantially completely
prevented from attaching to the surface of the substrate.
[0019] According to the above-described embodiments, the use of the
anode made of phosphorus-containing copper (phosphorus-containing
copper anode) having a phosphorus concentration of 1800 to 2700
ppm, preferably 2000 to 2700 ppm, makes it possible to produce a
firm black film, having a uniform thickness and which hardly peels
off, on the surface of the anode.
[0020] Even if a black film peels of a soluble anode of
phosphorus-containing copper (phosphorus-containing copper anode),
the copper electroplating apparatus, with a relatively simple
construction, can substantially completely prevent the black film
from adhering to the surface of the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is an overall layout plan view of a copper
electroplating apparatus according to an embodiment;
[0022] FIG. 2 is a schematic perspective view of a substrate holder
shown in FIG. 1;
[0023] FIG. 3 is a plan view of the substrate holder shown in FIG.
1;
[0024] FIG. 4 is a right side view of the substrate holder shown in
FIG. 1;
[0025] FIG. 5 is an enlarged view of a portion A of FIG. 4;
[0026] FIG. 6 is a vertical cross-sectional view of a copper
plating unit provided in the copper electroplating apparatus shown
in FIG. 1;
[0027] FIG. 7 is a plan view of an agitating paddle (an agitating
tool) provided in the copper plating unit shown in FIG. 6;
[0028] FIG. 8 is a cross-sectional view taken along line A-A in
FIG. 7;
[0029] FIG. 9 is a vertical cross-sectional view of a copper
plating unit according to another embodiment;
[0030] FIG. 10 is a vertical cross-sectional view of a copper
plating unit according to yet another embodiment;
[0031] FIG. 11 is a vertical cross-sectional view of a copper
plating unit according to yet another embodiment;
[0032] FIG. 12 is a vertical cross-sectional view of a copper
plating unit according to yet another embodiment;
[0033] FIG. 13 is a vertical cross-sectional view of a copper
plating unit according to yet another embodiment;
[0034] FIG. 14 is a vertical cross-sectional view of a copper
plating unit according to yet another embodiment; and
[0035] FIG. 15 is a vertical cross-sectional view of a copper
plating unit according to yet another embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0036] Embodiments of the present invention will now be described
with reference to the drawings. The same reference numerals are
used in the following figures and description to refer to the same
or like members, components, etc., and a duplicate description
thereof will be omitted.
[0037] FIG. 1 shows an overall layout plan of a copper
electroplating apparatus according to an embodiment. As shown in
FIG. 1, the copper electroplating apparatus includes two cassette
tables 12 on which substrate cassettes 10, each storing therein
substrates, such as semiconductor wafers, are placed, an aligner 14
for aligning an orientation flat or a notch of a substrate in a
predetermined direction, and a spin rinse drier 16 for drying a
plated substrate by rotating it at a high speed. Near the spin
rinse drier 16 is provided a substrate loading unit 20 for placing
a substrate holder 18 thereon and loading the substrate into the
substrate holder 18 and removing the substrate from the substrate
holder 18. Further, in the center of these units 10, 14, 16, and 20
is disposed a substrate transport device 22 constituted by a
transport robot for transporting the substrate between these
units.
[0038] The substrate loading unit 20, a storage vessel 24 for
storing (and temporarily storing) substrate holders 18 therein, a
pre-wetting bath 26 for immersing the substrate in pure water, a
pre-soaking bath 28 for etching away an oxide film formed on a
surface of a conductive layer, such as a seed layer, of the
substrate, a first cleaning bath 30a for cleaning the surface of
the pre-soaked substrate, together with the substrate holder 18,
with a cleaning liquid (e.g., pure water), a blow bath 32 for
removing the cleaning liquid from the cleaned substrate, a second
cleaning bath 30b for cleaning the plated substrate, together with
the substrate holder 18, with a cleaning liquid (e.g., pure water),
and a copper plating unit 34 are arranged in this order. The copper
plating unit 34 includes an overflow bath 36 and a plurality of
plating bath 38 surrounded by the overflow bath 36. Each plating
bath 38 is configured to receive one substrate therein and perform
plating, e.g., copper plating, on the surface of the substrate that
is immersed in a plating solution held in the plating bath 38.
[0039] Located lateral to the above baths, there is provided a
substrate holder transport device 40, driven e.g., by a linear
motor, for transporting the substrate holder 18, together with a
substrate, between the baths. The substrate holder transport device
40 has a first transporter 42 for transporting a substrate between
the substrate loading unit 20, the storage vessel 24, the
pre-wetting bath 26, the pre-soaking bath 28, the first cleaning
bath 30a, and the blow bath 32, and a second transporter 44 for
transporting the substrate between the first cleaning baths 30a,
the second cleaning bath 30b, the blow bath 32, and the copper
plating unit 34. The substrate holder transport device 40 may only
include the first transporter 42, without the second transporter
44.
[0040] Paddle drive devices 46 are provided each for driving a
paddle 232 (shown in FIG. 6) disposed in each plating bath 38 as an
agitator for agitating a plating solution in the plating cell 38.
The paddle drive devices 46 are located beside the overflow bath 36
at the opposite side of the substrate holder transport device
40.
[0041] The substrate loading unit 20 includes a flat stage plate 52
which is laterally slidable along rails 50. Two substrate holders
18, parallel to each other, are placed horizontally on the stage
plate 52. One substrate is transferred between one substrate holder
18 and the substrate transport device 22, and then the stage plate
52 is slid laterally so that the other substrate is transferred
between the other substrate holder 18 and the substrate transport
device 22.
[0042] As shown in FIGS. 2 through 5, the substrate holder 18
includes a first holding member (or a base holding member) 54
having a rectangular plate shape and made of vinyl chloride, and a
second holding member (or a movable holding member) 58 rotatably
coupled to the first holding member 54 through a hinge 56 which
allows the second holding member 58 to open and close with respect
to the first holding member 54. While the second holding member 58
is configured to be openable and closable through the hinge 56 in
this embodiment, it is also possible to dispose the second holding
member 58 opposite to the first holding member 54 and to move the
second holding member 58 away from and toward the first holding
member 54 to thereby open and close the second holding member
58.
[0043] The second holding member 58 includes a base portion 60 and
a ring-shaped seal holder 62. The seal holder 62 is made of vinyl
chloride so as to enable a retaining ring 64, which will be
described later, to slide well. An annular substrate-side sealing
member 66 is fixed to an upper portion of the seal holder 62. This
substrate-side sealing member 66 is placed in pressure contact with
a periphery of the surface of the substrate W to seal a gap between
the substrate W and the second holding member 58 when the substrate
W is held by the substrate holder 18. An annular holder-side
sealing member 68 is fixed to a surface, facing the first holding
member 54, of the seal holder 62. This holder-side sealing member
68 is placed in pressure contact with the first holding member 54
to seal a gap between the first holding member 54 and the second
holding member 58. The holder-side sealing member 68 is located at
the outer side of the substrate-side sealing member 66.
[0044] As shown in FIG. 5, the substrate-side sealing member 66 is
sandwiched between the seal holder 62 and a first mounting ring
70a, which is secured to the seal holder 62 by fastening tools 69a,
such as screws. The holder-side sealing member 68 is sandwiched
between the seal holder 62 and a second mounting ring 70b, which is
secured to the seal holder 62 by fastening tools 69b, such as
screws.
[0045] The seal holder 62 has a stepped portion at a periphery
thereof, and the retaining ring 64 is rotatably mounted to the
stepped portion through a spacer 65. The retaining ring 64 is
inescapably held by an outer peripheral portion of the first
mounting ring 70a. This retaining ring 64 is made of a material
(e.g., titanium) having high rigidity and excellent acid and alkali
corrosion resistance and the spacer 65 is made of a material having
a low friction coefficient, for example PTFE, so that the retaining
ring 64 can rotate smoothly.
[0046] Inverted L-shaped dampers 74, each having an inwardly
projecting portion and located at the outer side of the retaining
ring 64, are provided on the first holding member 54 at equal
intervals along a circumferential direction of the retaining ring
64. The retaining ring 64 has, on its outer circumferential
surface, outwardly projecting portions 64b arranged at positions
corresponding to positions of the dampers 74. A lower surface of
the inwardly projecting portion of each damper 74 and an upper
surface of each projecting portion 64b of the retaining ring 64 are
inclined in opposite directions along the rotational direction of
the retaining ring 64 to form tapered surfaces. A plurality (e.g.,
three) of upwardly projecting protrusions 64a are provided on the
retaining ring 64 at predetermined positions along the
circumferential direction of the retaining ring 64. The retaining
ring 64 can be rotated by pushing and moving each protrusion 64a
from a lateral direction by means of a rotating pin (not
shown).
[0047] With the second holding member 58 open, the substrate W is
inserted into the central portion of the first holding member 54,
and the second holding member 58 is then closed through the hinge
56. Subsequently the retaining ring 64 is rotated clockwise so that
each projecting portion 64b of the retaining ring 64 slides into
the inwardly projecting portion of each damper 74. As a result, the
first holding member 54 and the second holding member 58 are
fastened to each other and locked by engagement between the tapered
surfaces of the retaining ring 64 and the tapered surfaces of the
dampers 74. The lock of the second holding member 58 can be
released by rotating the retaining ring 64 counterclockwise to
disengage the projecting portions 64b of the retaining ring 64 from
the inverted L-shaped dampers 74. When the second holding member 58
is locked in the above-described manner, the downwardly-protruding
portion of the substrate-side sealing member 66 is placed in
pressure contact with the periphery of the surface of the substrate
W. The substrate-side sealing member 66 is pressed uniformly
against the substrate W to thereby seal the gap between the
periphery of the surface of the substrate W and the second holding
member 58. Similarly, when the second holding member 58 is locked,
the downwardly-protruding portion of the holder-side sealing member
68 is placed in pressure contact with the surface of the first
holding member 54. The sealing holder-side sealing member 68 is
uniformly pressed against the first holding member 54 to thereby
seal the gap between the first holding member 54 and the second
holding member 58.
[0048] A protruding portion 82 is formed on the upper surface of
the first holding member 54 so as to protrude in a ring shape with
a size corresponding to a size of the substrate W. The protruding
portion 82 has an annular support surface 80 which contacts a
periphery of the substrate W to support the substrate W. The
protruding portion 82 has recesses 84 arranged at predetermined
positions along a circumferential direction of the protruding
portion 82.
[0049] A pair of outwardly-projecting holder hangers 90 is provided
on the ends of the first holding member 54 of the substrate holder
18. These holder hangers 90 serve as a support when the substrate
holder 18 is transported and when the substrate holder 18 is
supported in a suspended state. A hand lever 92 extends between the
holder hangers 90 on both sides. The substrate holder transport
device 40 is configured to grip the hand lever 92 to thereby hold
the substrate holder 18. In the storage vessel 24, the holder
hangers 90 are placed on an upper surface of a surrounding wall of
the storage vessel 24, whereby the substrate holder 18 is suspended
in a vertical position. When transporting the substrate holder 18
from the storage vessel 24, the holder hangers 90 of the suspended
substrate holder 18 are gripped by the first transporter 42 of the
substrate holder transport device 40. Also in the pre-wetting bath
26, the pre-soaking bath 28, the cleaning baths 30a, 30b, the blow
bath 32, and the copper plating unit 34, the substrate holder 18 is
held in a suspended state with the holder hangers 90 placed on a
surrounding wall of each bath.
[0050] As shown in FIG. 3, a plurality of (e.g., 12 as illustrated)
electrical conductors (electrical contacts) 86 are disposed in the
recesses 84, respectively. These electrical conductors 86 are
coupled respectively to wires extending from connecting terminals
91 provided on the holder hanger 90. The electrical conductors 86
have their end portions, respectively, which are located outwardly
of the periphery of the substrate W so that the electrical
conductors 86 themselves do not contact the substrate W. When the
substrate W is placed on the support surface 80 of the first
holding member 54, the end portions of the electrical conductors 86
spring out around the substrate W to resiliently contact lower
portions of electrical contacts 88 shown in FIG. 5.
[0051] The electrical contacts 88, which are to be electrically
connected to the electrical conductors 86, are secured to the seal
holder 62 of the second holding member 58 by fastening tools 89,
such as screws. Each of the electrical contacts 88 has a leaf
spring-like contact portion located at the outer side of the
substrate-side sealing member 66 and projecting inwardly. This
spring-like contact portion is springy and bends easily. When the
substrate W is held by the first holding member 54 and the second
holding member 58, the contact portions of the electrical contacts
88 come into elastic contact with the peripheral surface of the
substrate W supported on the support surface 80 of the first
holding member 54.
[0052] The second holding member 58 is opened and closed by a
not-shown pneumatic cylinder and by a weight of the second holding
member 58 itself. More specifically, the first holding member 54
has a through-hole 54a, and a pneumatic cylinder is provided so as
to face the through-hole 54a when the substrate holder 18 is placed
on the stage plate 52. The second holding member 58 is opened by
extending a piston rod of the pneumatic cylinder through the
through-hole 54a to push up the seal holder 62 of the second
holding member 58 through a pushing rod. The second holding member
58 is closed by its own weight when the piston rod is
retracted.
[0053] FIG. 6 is a vertical cross-sectional view of the copper
plating unit 34 provided in the copper electroplating apparatus
shown in FIG. 1. As shown in FIG. 6, the plating bath 38 is
configured to hold a predetermined amount of plating solution
therein. A bottom plate 100 is disposed in the plating bath 38,
whereby the interior of the plating bath 38 is separated into an
upper substrate processing chamber and a lower plating solution
distribution chamber 104. The interior of the upper substrate
processing chamber is further separated into an anode chamber 110
and a cathode chamber 112 as described below. A
downwardly-extending shield plate 106 for regulating flow of the
plating solution is mounted to the bottom plate 100.
[0054] A shield box 108 is disposed in the substrate processing
chamber, so that the interior of the substrate processing chamber
is separated into the anode chamber 110 inside the shield box 108
and the cathode chamber 112 outside the shield box 108. The bottom
plate 100 has first plating solution passage openings 100a that
provide fluid communication between the cathode chamber 112 and the
plating solution distribution chamber 104. The bottom plate 100
further has a second plating solution passage opening 100b located
below the anode chamber 110. The shield box 108, at its bottom, has
a plating solution passage opening 108a formed at a position
corresponding to the second plating solution passage opening 100b.
The plating solution distribution chamber 104 communicates with the
anode chamber 110 via the second plating solution passage opening
100b and the plating solution passage opening 108a.
[0055] When a substrate W is held by the substrate holder 18, the
peripheral portion of the substrate W is liquid-tightly sealed with
the sealing members 66, 68, while a front surface (to-be-plated
surface) of the substrate W is exposed. The substrate W, held by
the substrate holder 18, is immersed in the plating solution in the
cathode chamber 112 and set in a vertical position.
[0056] The plating solution used in this embodiment is an acidic
copper sulfate plating solution comprising sulfuric acid, copper
sulfate, a halide ion and the following organic additives: a
plating accelerator comprising SPS (bis(3-sulfopropyl) disulfide);
a suppressor comprising PEG (polyethylene glycol); and a leveler
comprising PEI (polyethylene imine). A chloride ion is preferably
used as the halide ion.
[0057] The overflow bath 36 for receiving the plating solution that
has overflown the edge of the plating bath 38 is provided around
the plating bath 38. One end of a circulation line 122, which is
provided with a pump 120, is coupled to the bottom of the overflow
bath 36, and the other end of the circulation line 122 is coupled
to the bottom of the plating solution distribution chamber 104. The
plating solution that has been collected in the overflow bath 36 is
introduced into the plating solution distribution chamber 104 by
the actuation of the pump 120. A gap is provided between a lower
end of the shield plate 106 and the bottom of the plating solution
distribution chamber 104. Therefore, the flow of the plating
solution, flowing out of the circulation line 122, is divided by
the shield plate 106 into a flow toward the anode chamber 110 and a
flow toward the cathode chamber 112. Thus, a part of the incoming
plating solution passes through the first plating solution passage
openings 100a of the bottom plate 100 and flows into the cathode
chamber 112, while the remainder of the plating solution passes
through the second plating solution passage opening 100b of the
bottom plate 100 and the plating solution passage opening 108a of
the shield box 108 and flows into the anode chamber 110.
[0058] The plating solution that has flowed into the cathode
chamber 112 overflows the edge of the plating bath 38 into the
overflow bath 36. The plating solution that has flowed into the
anode chamber 110 flows out of the shield box 108 through an
opening (not shown) provided at a top portion of a side wall of the
shield box 108, and also flows into the overflow bath 36. The
plating solution in the anode chamber 110 does not directly flow
into the cathode chamber 112.
[0059] Located downstream of the pump 120, a constant-temperature
unit 124 for regulating a temperature of the plating solution at a
predetermined temperature (e.g., 25.degree. C.), and a filter 126
for removing foreign matter (e.g., having a diameter of not less
than 0.1 .mu.n) contained in the plating solution are attached to
the circulation line 122. A drain line 128 is connected to the
bottom of the plating bath 38.
[0060] A disk-shaped soluble anode of phosphorus-containing copper
(hereinafter referred to as "phosphorus-containing copper anode")
130, having approximately the same size as the substrate W and held
by an anode holder 132, is set in a vertical position in the anode
chamber 110. This phosphorus-containing copper anode 130 is
immersed in the plating solution in the anode chamber 110 when the
plating bath 38 is filled with the plating solution. The substrate
W, held by the substrate holder 18, is immersed in the plating
solution held in the cathode chamber 112. The substrate W is
disposed in the cathode chamber 112 such that it faces the
phosphorus-containing copper anode 130.
[0061] In this embodiment a material (phosphorus-containing copper)
having a copper purity of 99.69% by mass and a phosphorus
concentration of 2660 ppm by mass (hereinafter referred to simply
as ppm) is used for the phosphorus-containing copper anode 130. The
phosphorus concentration of the phosphorus-containing copper anode
130 is in the range of 1800 to 2700 ppm, preferably in the range of
2000 to 2700 ppm. The phosphorus-containing copper anode 130 of
this embodiment has a sulfur concentration of 50 ppm and a nickel
concentration of 100 ppm. The average copper grain size of the
phosphorus-containing copper anode 130 is 35 .mu.m in this
embodiment, preferably in the range of 15 .mu.m to 45 .mu.m, more
preferably in the range of 30 .mu.m to 40 .mu.m.
[0062] The copper grain size is preferably not only small but also
uniform. If the grain boundary is large, partial detachment of
grains can occur due to selective or preferential progress of
dissolution of the pain boundary. On the other hand, if the grain
boundary is too small, it is difficult to produce a uniform crystal
structure. From this viewpoint, the average copper grain size of
the phosphorus-containing copper anode 130 is preferably in the
range of 15 .mu.m to 45 .mu.m, more preferably in the range of 30
.mu.m to 40 .mu.m.
[0063] It has been verified from an experiment that a firm black
film, having a uniform thickness and which hardly peels off, is
produced on the surface of the phosphorus-containing copper anode
130 when the anode 130 has a phosphorus concentration in the range
of 1800 to 2700 ppm, preferably in the range of 2000 to 2700
ppm.
[0064] In particular, the experiment was conducted using the
phosphorus-containing copper anode 130 comprising the
above-described components and using two types of plating solutions
(first plating solution and second plating solution) containing
different additives. Dummy plating was carried out for one hour at
a cathode current density of 2 ASD (A/cm.sup.2) to produce a black
film on the surface of the anode. Subsequently, plating was carried
out for two hours at a cathode current density of 3 ASD.
Thereafter, shower rinsing (3.5 L/min) was performed on the black
film on the anode by applying a shower perpendicularly onto the
black film from a shower head disposed at a distance of 30 cm.
During the shower rinsing, the black film was photographed every 10
seconds so that the state of the black film was examined. The
examination results have showed that in both cases of the first
plating solution and the second plating solution, an underlying
material the anode) was not exposed even after the shower rinsing
was carried out for 90 seconds and that no peeling of the black
film from the underlying material (i.e., the anode) was
observed.
[0065] A comparative experiment was conducted in the same manner as
the above-described experiment except for using a
phosphorus-containing copper anode having a phosphorus
concentration of 400 to 500 ppm. As a result, the underlying
material (anode) became exposed after carrying out the shower
rinsing for 30 seconds in the case of using the first plating
solution, and after carrying out the shower rinsing for 20 seconds
in the case of using the second plating solution, and peeling of
the black film from the base (anode) was observed in both cases. An
additional comparative experiment was conducted in the same manner
as the above-described experiment except for using a
phosphorus-containing copper anode having a phosphorus
concentration of 400 to 600 ppm. As a result, the underlying
material (anode) became exposed after carrying out the shower
rinsing for 10 seconds in the case of using the first plating
solution, and 20 seconds in the case of using the second plating
solution, and peeling of the black film from the base (anode) was
observed in both cases.
[0066] A regulation plate 134 for regulating the distribution of
electric potential in the plating bath 38 is disposed in the
plating bath 38. This regulation plate 134 is located between the
phosphorus containing copper anode 130 and the substrate holder 18
disposed in the plating bath 38. In this embodiment the regulation
plate 134 has a cylindrical portion 136 and a rectangular flange
portion 138, with an opening 134a which is formed by an inner
circumferential surface of the cylindrical portion 136. The
regulation plate 134 is made of polyvinyl chloride which is a
dielectric material. The size of the opening 134a, i.e., the
diameter of the inner circumferential surface of the cylindrical
portion 136, is set to be capable of sufficiently restricting
broadening of the electric field. The cylindrical portion 136 has a
predetermined axial length.
[0067] The shield box 108 has an opening 108b at a position
corresponding to the cylindrical portion 136 of the regulation
plate 134. The flange portion 138 of the regulation plate 134 is
located in the anode chamber 110, and the cylindrical portion 136
of the regulation plate 134 is fit into the opening 108b. An
anode-side end of the cylindrical portion 136 lies in the anode
chamber 110. A diaphragm 142 is fixed to the anode-side end of the
cylindrical portion 136 by an annular fixing plate 140. The
diaphragm 142 is disposed so as to entirely cover the inner
circumferential surface of the cylindrical portion 136, i.e., the
opening 134a of the regulation plate 134 in its entirety. The
diaphragm 142 is comprised of a cation exchange membrane or porous
membrane which allows permeation of metal ions therethrough but
does not allow permeation of additives contained in the plating
solution. A commercially-available product "Yumicron" (Yuasa
M&B CO., Ltd.) is an example of such a porous membrane.
[0068] A gap between the flange portion 138 of the regulation plate
134 and the inner surface of the shield box 108, a gap between the
flange portion 138 and the diaphragm 142, and a gap between the
faxing plate 140 and the diaphragm 142 are sealed with sealing
members (not shown), respectively.
[0069] A water-permeable mesh anode bag 144, which surrounds the
phosphorus-containing copper anode 130 and is secured to the
plating bath 38, is disposed in the anode chamber 110. Examples of
the anode bag 144 may include a polypropylene mesh having a
thread-to-thread spacing of 40 .mu.m to 50 .mu.m and a permeability
to a copper sulfate plating solution of 20 mL/cm.sup.2/sec, a
polypropylene mesh having a thread-to-thread spacing of 10 .mu.m to
15 .mu.m and a permeability to a copper sulfate plating solution of
1.25 mL/cm.sup.2/sec, and a polypropylene mesh having a
thread-to-thread spacing of 1 .mu.m and a permeability to a copper
sulfate plating solution of 0.6 mL/cm.sup.2/sec. An upper end of
the anode bag 144 lies at a position higher than the opening for
overflowing the plating solution in the anode chamber 110.
[0070] According to this embodiment, the phosphorus-containing
copper anode 130 is surrounded by the water-permeable mesh anode
bag 144 and, in addition, the anode-side end of the opening 134a of
the regulation plate 134 is entirely covered with the diaphragm
142. Therefore, even if a black film peels of the
phosphorus-containing copper anode 130, the black film does not
enter the cathode chamber 112. Thus, it is possible to
substantially completely prevent the black film from adhering to
the surface of the substrate W.
[0071] The black film that has peeled of the phosphorus-containing
copper anode 130 is suspended in the plating solution in the anode
chamber 110. The movement of the black film into the cathode
chamber 112 can be doubly blocked by the anode bag 144 and the
diaphragm 142. The plating solution in the anode chamber 110,
containing the suspended black film, is delivered via the overflow
bath 36 to the filter 126, where foreign matter including the black
film is removed. The plating solution is then returned to the
cathode chamber 112 and the anode chamber 110.
[0072] The copper plating unit 34 of this embodiment is provided
with a bubbling device 150 for supplying a gas, such as air or an
inert gas (e.g., N.sub.2 gas), into the plating solution in the
anode bag 144 to form bubbles in the plating solution. The bubbling
device 150 includes a bubbling pipe 152 having a large number of
jet ports its an upper area, and a gas supply line 154
communicating with the bubbling pipe 152. The bubbling pipe 152
extends horizontally along the surface of the phosphorus-containing
copper anode 130 and is disposed in the anode bag 144. The gas
supply line 154 is provided with a filter 156 for removing foreign
matter from the gas flowing through the gas supply line 154.
[0073] The bubbling device 150 is provided optionally. The black
film can be made to more hardly peel off the phosphorus-containing
copper anode 130 by supplying, by means of the bubbling device 150,
the gas, such as air or an inert gas (e.g., N.sub.2 gas), into the
plating solution to form the bubbles in the plating solution
existing on the surface of the phosphorus-containing copper anode
130 in the anode bag 144.
[0074] The agitating paddle 232 as an agitating tool for agitating
the plating solution existing between the substrate holder 18 and
the regulation plate 134 is disposed in the cathode chamber 112 of
the plating bath 38. The agitating paddle 232 is located between
the substrate holder 18 and the regulation plate 134, disposed in
the plating bath 38, and extends vertically. By reciprocating the
agitating paddle 232 parallel to the substrate W to agitate the
plating solution during plating of the substrate W, a sufficient
amount of copper ions can be supplied uniformly to the surface of
the substrate W.
[0075] As shown in FIGS. 7 and 8, the agitating paddle 232 is
constituted by a rectangular plate-like member having a uniform
thickness "t" in a range of 3 mm to 5 mm, and has a plurality of
parallel slits 232a that define vertically-extending strip-like
portions 232b. The agitating paddle 232 is formed of, for example,
a resin such as PVC, PP, or FIFE, or SUS or titanium coated with
fluororesin. It is preferred that at least part of the agitating
paddle 232, which contacts the plating solution, be electrically
isolated. A vertical length L.sub.1 of the agitating paddle 232 and
a vertical length L.sub.2 of the slits 232a are sufficiently larger
than the vertical size of the substrate W. Further, the agitating
paddle 232 is designed such that the sum of its lateral length H
and its reciprocation distance (stroke) is sufficiently larger than
the lateral size of the substrate W.
[0076] It is preferred that a Width and the number of slits 232a be
determined such that each strip-shaped portion 232b is as narrow as
possible insofar as it has the necessary rigidity so that the
strip-shaped portions 232b between the slits 232a can efficiently
agitate the plating solution and, in addition, the plating solution
can efficiently pass through the slits 232a.
[0077] The copper plating unit 34 is provided with a plating power
source whose positive electrode is connected via a conducting wire
to the phosphorus-containing copper anode 130 and whose negative
electrode is connected via a conducting wire to the surface of the
substrate W when plating of the substrate W is performed.
[0078] A sequence of plating process steps of performing copper
electroplating of the surface of the substrate W using the copper
electroplating apparatus shown in FIG. 1 will now be described.
[0079] At the start-up of the copper electroplating apparatus,
dummy plating is performed by applying a voltage between a dummy
substrate and the phosphorus-containing copper anode 130 to produce
a black film on the surface of the phosphorus-containing copper
anode 130. As described above, a firm black film, having a uniform
thickness and which hardly peels off, is produced on the surface of
the phosphorus-containing copper anode 130 by performing the dummy
plating with the use of the anode 130 having a phosphorus
concentration in the range of 1800 to 2700 ppm, preferably in the
range of 2000 to 2700 ppm, and an average copper grain size in the
range of 15 .mu.m to 45 .mu.m, preferably in the range of 30 .mu.m
to 40 .mu.m.
[0080] One substrate is taken by the substrate transport device 22
out of the cassette 10 mounted on the cassette table 12, and the
substrate is placed on the aligner 14 that aligns an orientation
flat or a notch in a predetermined direction. After the alignment,
the substrate is transported to the substrate loading unit 20 by
the substrate transport device 22.
[0081] On the other hand, two substrate holders 18 housed in the
storage vessel 24 are simultaneously gripped by the first
transporter 42, and transported to the substrate loading unit 20.
The substrate holders 18 are lowered into a horizontal position and
are simultaneously placed on the stage plate 52 of the substrate
loading unit 20. Then the two air cylinders are actuated to open
the second holding members 58 of the two substrate holders 18.
[0082] The substrate is inserted by the substrate transport device
22 into the substrate holder 18 positioned on the center side, and
the air cylinder is reversely actuated to close the second holding
member 58. The second holding member 58 is then locked by means of
a locking/unlocking mechanism (not shown). After the completion of
loading of the substrate to the one substrate holder 18, the stage
plate 52 is slid laterally, and a substrate is loaded into the
other substrate holder 18 in the same manner. Thereafter, the stage
plate 52 is returned to its original position.
[0083] The substrate W is fixed to the substrate holder 18 with its
front surface (to-be-plated surface) exposed in the opening of the
substrate holder 18. To prevent intrusion of the plating solution
into the internal space of the substrate holder 18, the gap between
the peripheral portion of the substrate W and the second holding
member 58 is sealed with the substrate-side sealing member 66, and
the gap between the first holding member 54 and the second holding
member 58 is sealed with the holder-side sealing member 68. The
substrate W, at a sealed portion not in contact with the plating
solution, is electrically connected with the electrical contacts
88. The conducting wires extending from the electrical contacts 88
are connected to the connecting terminal 91 of the substrate holder
18. Therefore, an electric current can be supplied to a conductive
layer, such as a seed layer, of the substrate W by connecting a
power source to the connecting terminal 91. The substrate loading
unit 20 has a sensor for sensing the electrical contact between the
substrate W, held by the substrate holder 18, and the electrical
contacts 88. The sensor, when it detects poor contact between the
substrate W and the electrical contacts 88, outputs a signal to a
controller (not shown).
[0084] The two substrate holders 18, each holding a substrate, are
transported from the substrate loading unit 20 to the pre-wetting
bath 26 by the first transporter 42 of the substrate holder
transport device 40. The first transporter 42 lowers the substrate
holders 18 to immerse the substrates, together with the substrate
holders 18, in a pre-wetting liquid (e.g., pure water) in the
pre-wetting bath 26.
[0085] Next, the two substrate holders 18 holding the substrates
are transported from the pre-wetting bath 26 to the pre-soaking
bath 28 by the first transporter 42. In the pre-soaking bath 28, a
surface oxide film of each substrate is etched away, thereby
exposing a clean metal surface. Thereafter, the substrate holders
18 holding the substrates are transported to the first cleaning
bath 30a by the first transporter 42. In the first cleaning bath
30a, the substrates and the substrate holders 18 are cleaned with a
cleaning liquid supplied into the first cleaning bath 30a. Pure
water or a chemical solution can be used as the cleaning
liquid.
[0086] The substrate holders 18, holding the cleaned substrates,
are transported from the first cleaning bath 30a to the copper
plating unit 34 by the second transporter 44 of the substrate
holder transport device 40. The substrate holders 18 are lowered by
the second transporter 44 into the plating baths 38, and are
suspended from the tops of the plating baths 38. The second
transporter 44 of the substrate holder transport device 40
sequentially repeats the above operations to sequentially transport
substrate holders 18, each holding a substrate, to the plating
baths 38 of the copper plating unit 34.
[0087] After the substrate holders 18 are set in all the plating
baths 38, copper plating of each substrate is canned out in each
plating bath 38 in the following manner. While circulating the
plating solution between the plating bath 38 and the overflow bath
36 through the circulation line 122, copper plating of the surface
of the substrate is carried out by applying a plating voltage
between the phosphorus-containing copper anode 130 and the
substrate in the plating bath 38. During plating, each substrate
holder 18 is suspended and fixed with the holder hangers 90
supported on the top of the plating bath 38, and an electric
current is supplied from the plating power source to a conductive
layer, such as a seed layer, through the electrical conductors 86
and the electrical contacts 88. During plating of the substrate,
the agitating paddle 232 reciprocates parallel to the surface of
the substrate by means of the paddle drive device 46 and, as
necessary, bubbles are formed in the plating solution by means of
the bubbling device 150.
[0088] Even if, during the copper plating, a black film peels off
the phosphorus-containing copper anode 130 and is suspended in the
plating solution in the anode chamber 110, the movement of the
black film into the cathode chamber 112 is doubly blocked by the
anode bag 144 and the diaphragm 142. The black film can therefore
be substantially completely prevented from adhering to the surface
of the substrate.
[0089] Upon completion of the copper plating, the application of
the plating voltage, the supply of the plating solution, the
reciprocation of the paddle, and the bubbling of the plating
solution are stopped. Thereafter, two substrate holders 18, each
holding a plated substrate, are simultaneously gripped by the
second transporter 44 and are transported to the second cleaning
bath 30b, where the substrate surfaces, together with the substrate
holders 18, are cleaned with a cleaning liquid.
[0090] The substrate holders 18, holding the cleaned substrates,
are transported from the second cleaning bath 30b to the blow bath
32 by the second transporter 44. In the blow bath 32, air or
nitrogen gas blows liquid droplets from the surfaces of the
substrates held by the substrate holders 18, thereby drying the
substrates.
[0091] The two substrate holders 18 after dried in the blow bath 32
are transported to the substrate loading unit 20 by the first
transporter 42, and are placed on the stage plate 52 of the
substrate loading unit 20. The second holding member 58 of the
substrate holder 18 at the center side is unlocked by means of the
locking/unlocking mechanism, and the air cylinder is actuated to
open the second holding member 58. The substrate transport device
22 removes the substrate from the substrate holder 18, and
transports the substrate to the spin rinse drier 16, where the
substrate is spin-dried (drained) by high-speed rotation. The dried
substrate is returned to the cassette 10 by the substrate transport
device 22.
[0092] After or in parallel with the substrate is returned to the
cassette 10, the stage plate 52 is slid laterally and the substrate
is removed from the other substrate holder 18. The substrate is
then spin-dried by the spin rinse drier 16, and the dried substrate
is returned to the cassette 10 by the substrate transport device
22.
[0093] FIG. 9 is a vertical cross-sectional view of a copper
plating unit 34a according to another embodiment, which can be used
in the copper electroplating apparatus shown in FIG. 1. The copper
plating unit 34a of this embodiment differs from the copper plating
unit 34 shown in FIG. 6 in the following respects. The regulation
plate 134 of the copper plating unit 34a of this embodiment is not
provided with the diaphragm 142. Instead, the phosphorus-containing
copper anode 130, disposed in the anode chamber 110, is surrounded
by a first anode bag 162 mounted to the anode holder 132, and the
first anode bag 162 is surrounded by a second anode bag 164 secured
to the plating bath 38. The first anode bag 162 and the second
anode bag 164 are formed of a water-permeable mesh. The bubbling
pipe 152 of the bubbling device 150 is located between the first
anode bag 162 and the second anode bag 164 and disposed
horizontally along a surface of the anode holder 132.
[0094] A polypropylene mesh having a thread-to-thread spacing of 20
.mu.m may be used as the first anode bag 162. A mesh which is finer
than the first anode bag 162, e.g., a polypropylene mesh having a
thread-to-thread spacing of 1 .mu.m, is used as the second anode
bag 164. Upon replacement of the phosphorus-containing copper anode
130, the first anode bag 162, together with the anode holder 132,
is pulled away from the plating bath 38 to be replaced with a new
one.
[0095] According to this embodiment, a relatively large black film
that has peeled of the surface of the phosphorus-containing copper
anode 130 and is floating in the plating solution in the anode
chamber 110, is blocked from passing through the first anode bag
162. A relatively small black film that has passed through the
first anode bag 162 is blocked from passing through the second
anode bag 164. In this manner, a black film suspended in the
plating solution is substantially completely prevented from moving
from the anode chamber 110 into the cathode chamber 112.
[0096] FIG. 10 is a vertical cross-sectional view of a copper
plating unit 34b according to yet another embodiment. The copper
plating unit 34b of this embodiment differs from the copper plating
unit 34 shown in FIG. 6 in the following respects. The copper
plating unit 34b of this embodiment is not provided with the anode
bag 144. Instead, a pre-filter 170 is disposed in the second
plating solution passage opening 100b of the bottom plate 100 and
the plating solution passage opening 108a of the shield box 108,
which provide fluid communication between the plating solution
distribution chamber 104 and the interior of the shield box 108 in
the plating bath 38. A plating solution outlet 172 for discharging
the plating solution from the anode chamber 110 is provided in the
bottom plate 100 and in the bottom of the shield box 108. One end
of a plating solution discharge line 176, which is provided with an
on-off valve 174, is connected to the plating solution outlet 172,
and the other end of the plating solution discharge line 176 is
connected to the circulation line 122 at a point upstream of the
pump 120. The bubbling pipe 152 of the bubbling device 150 is
located near the bottom of the shield box 108 said disposed
horizontally along the back surface of the anode holder 132.
[0097] According to this embodiment, the plating solution flows
into the anode chamber 110 after foreign matter is removed from the
plating solution by the pre-filter 170. A black film that has
peeled off the surface of the phosphorus-containing copper anode
130 and is suspended in the plating solution held in the anode
chamber 110 gradually sinks, due to its own weight, toward the
bottom of the anode chamber 110. The plating solution at the bottom
of the anode chamber 110, containing a considerable amount of black
film, is discharged from the bottom of the anode chamber 110
through the plating solution discharge line 176.
[0098] The circulation line 122 branches, at a point downstream of
the filter 126, into a first branch line 200A and a second branch
line 200B. The first branch line 200A extends into the anode
chamber 110, while the second branch line 200B extends in the
plating solution distribution chamber 104. The pre-filter 170 is
provided in the first branch line 200A, so that foreign matter in
the plating solution flowing in the first branch line 200A is
removed by the pre-filter 170. The plating solution that has passed
through the second branch line 200B is released into the plating
solution distribution chamber 104.
[0099] The plating solution containing a black film joins the
circulation line 122 at the point upstream of the pump 120, and is
sent to the constant-temperature unit 124 and to the filter 126 by
the pump 120. The black film is removed from the plating solution
by the filter 126. In addition, since the plating solution
discharge line 176 for discharging the plating solution from the
anode chamber 110 is separated from the second branch line 200B
extending to the cathode chamber 112, the black film can be
substantially completely prevented from entering the cathode
chamber 112.
[0100] Even if the black film sinks due to its own weight, the
pre-filter 170 can prevent the black film from intruding into the
plating solution distribution chamber 104. Therefore, the black
film does not enter the cathode chamber 112 via the plating
solution distribution chamber 104.
[0101] As with the embodiment shown in FIG. 6, an opening may be
provided at a top portion of the side wall of the shield box 108 in
this embodiment shown in FIG. 10 so that the plating solution in
the anode chamber 110 flows through the opening into the overflow
bath 36. As an alternative, the plating solution may not be allowed
to overflow the anode chamber 110. In that case, the first branch
line 200A is provided with an on-off valve 210 as shown in FIG. 10.
This on-off valve 210 is disposed upstream of the pre-filter 170.
The on-off valves 210, 174 and the liquid pumping rate of the pump
120 are controlled so that the amount of the plating solution in
the anode chamber 110 is kept within a predetermined range.
[0102] This embodiment makes it possible to reduce the amount of
the black film contained in the plating solution in the anode
chamber 110 and prevent the black film suspended in the plating
solution from entering the cathode chamber 112. In order to ensure
appropriate permeability to the plating solution, the pre-filter
170 has a mesh coarser than the diaphragm 142. Instead of the
pre-filter 170, a backflow prevention valve or a check valve may be
used to prevent the plating solution in the anode chamber 110 from
flowing back into the plating solution distribution chamber
104.
[0103] FIG. 11 is a vertical cross-sectional view of a copper
plating unit 34c according to yet another embodiment. The copper
plating unit 34c of this embodiment differs from the copper plating
unit 34b shown in FIG. 10 in that the plating solution discharge
line 176, extending from the plating solution outlet 172, is not
connected to the circulation line 122 and that the plating solution
flowing through the plating solution discharge line 176 is
discarded as liquid waste. This structure can prevent a gradual
increase in an amount of a black film in the plating solution and
clogging of the filters 126, 170. This structure can also prevent
small foreign matter, which cannot be trapped by the filter 126,
from entering the cathode chamber 112.
[0104] FIG. 12 shows a copper plating unit 34d according to yet
another embodiment. The copper plating unit 34d of this embodiment
differs from the copper plating unit 34 shown in FIG. 6 in the
following respects. The copper plating unit 34d of this embodiment
is not provided with the anode bag 144. Furthermore, the bottom
plate 100 is not provided with the second plating solution passage
opening 100b, and the shield box 108 is not provided with the
plating solution passage opening 108a. Instead, the copper plating
unit 34d of this embodiment is provided with a plating solution
supply line 182 which branches of from the circulation line 122 at
a point downstream of the filter 126. The plating solution supply
line 182 is provided with an on-off valve 180. The plating solution
supply line 182 is coupled to the anode chamber 110. A pure water
supply line 184 and a plating solution discharge line 190 are also
coupled to the anode chamber 110. The plating solution discharge
line 190 extends upwardly from the bottom of the anode chamber 110
and is provided with an on-off valve 186 and a pump 188. A liquid
level sensor 192 is provided for detecting a liquid level of the
plating solution in the anode chamber 110. The bubbling pipe 152 of
the bubbling device 150 is located at the bottom of the shield box
108 and disposed horizontally along the back surface of the anode
holder 132.
[0105] In the embodiment shown in FIG. 12, the plating solution in
the anode chamber 110 is not allowed to overflow and is held in a
certain amount in the anode chamber 110. The operations of the
on-off valves 180, 186 and the supply of pure water from the pure
water supply line 184 are controlled so that the liquid level of
the plating solution (i.e., the amount of the plating solution in
the anode 110), detected by the liquid level sensor 192, is kept
within a predetermined range.
[0106] In operation, while the liquid level of the plating solution
in the anode chamber 110 is kept within a predetermined range based
on an output signal of the liquid level sensor 192, the plating
solution is supplied into the anode chamber 110 through the plating
solution supply line 182 which branches of from the circulation
line 122, and pure water is supplied to the plating solution in the
anode chamber 110 through the pure water supply line 184. The
plating solution is discharged from the bottom of the anode chamber
110 through the plating solution discharge line 190.
[0107] Also in this embodiment, a black film floating in the
plating solution in the anode chamber 110 gradually sinks, due to
its own weight, toward the bottom of the anode chamber 110. The
plating solution at the bottom of the anode chamber 110, containing
a considerable amount of the black film, is discharged from the
anode chamber 110 through the plating solution discharge line 190.
This operation can reduce the amount of the black film contained in
the plating solution in the anode chamber 110 and can substantially
completely prevent the black film suspended in the plating solution
from entering the cathode chamber 112.
[0108] FIG. 13 is a vertical cross-sectional view of a copper
plating unit 34e according to yet another embodiment. The copper
plating unit 34e of this embodiment differs from the copper plating
unit 34d shown in FIG. 12 in that the plating solution discharge
line 190 is connected to the bottom of the anode chamber 110 so
that the plating solution, by its own weight, flows into the
plating solution discharge line 190 and is discharged to the
outside. The plating solution discharge line 190 is provided with
an on-off valve 194. This embodiment can thus simplify the
apparatus.
[0109] FIG. 14 is a vertical cross-sectional view of a copper
plating unit 34f according to yet another embodiment. The copper
plating unit 34f of this embodiment differs from the copper plating
unit 34 shown in FIG. 6 in that the phosphorus-containing copper
anode 130 is surrounded by double anode hags 162, 164 and that the
plating solution in the overflow bath 36 is not returned to the
anode chamber 110 while the plating solution is returned to the
cathode chamber 112. Further, the copper plating unit 34f is not
provided with the bubbling device 150.
[0110] The double mesh anode bags are constituted by a coarse first
anode bag 162 and a second anode bag 164 which is finer than the
first anode bag 162. The second anode bag 164 is disposed so as to
surround the first anode bag 162. The anode bags 162, 164 are each
formed of a water-permeable polypropylene mesh. Such double anode
bags 162, 162 can trap both a relatively large black film and a
relatively small black film in two stages, thereby preventing
clogging of the diaphragm 142.
[0111] In this embodiment, the anode chamber 110 is configured to
only hold the plating solution therein and does not basically allow
the plating solution to overflow the anode chamber 110. A relief
shoot 240 is provided on the side wall of the shield box 108 that
defines the anode chamber 110. The relief shoot 240 communicates
with the top area of the anode chamber 110 and extends from the
anode chamber 110 into the overflow bath 36. Even if the plating
solution overflows the anode chamber 110, the plating solution
flows through the relief shoot 240 into the overflow bath 36. Thus,
even if the plating solution flows out of the anode chamber 110,
the plating solution will not directly enter the cathode chamber
112.
[0112] A pure water supply line 184 and a plating solution
discharge line 190 are coupled to the anode chamber 110. The
plating solution discharge line 190 extends downwardly from the
bottom of the anode chamber 110. The plating solution discharge
line 190 is provided with a drain valve 241. When the drain valve
241 is opened, the plating solution in the anode chamber 110 is
discharged through the plating solution discharge line 190. The
plating solution flowing in the plating solution discharge line 190
is not recovered, and is discarded as liquid waste.
[0113] A black film suspended in the plating solution in the anode
chamber 110 gradually sinks due to its own weight toward the bottom
of the anode chamber 110. The plating solution at the bottom of the
anode chamber 110, containing a considerable amount of the black
film, is discharged, due to its own weight, from the anode chamber
110 through the plating solution discharge line 190. This operation
can reduce the amount of the black film contained in the plating
solution in the anode chamber 110 and can prevent the black film
suspended in the plating solution from entering the cathode chamber
112.
[0114] A plating solution supply line 244 is coupled to the top of
the anode chamber 110. This plating solution supply line 244 is not
used to supply the plating solution to the anode chamber 110 during
plating of a substrate, but used solely to initially supply the
plating solution to the anode chamber 110 before the start of
plating, i.e., used solely to prepare the plating bath. The plating
solution supply line 244 is provided with a first supply valve 246
and a second supply valve 247 located downstream of the first
supply valve 246. The circulation line 122 is connected to the
plating solution supply line 244 at a branch point 249 located
between the first supply valve 246 and the second supply valve 247,
so that a part of the plating solution, flowing in the plating
solution supply line 244, flows into the circulation line 122. The
first supply valve 246 and the second supply valve 247 are usually
closed. Only at the time of preparation of the plating bath, the
first supply valve 246 and the second supply valve 247 are opened
to supply the plating solution to the anode chamber 110 through the
plating solution supply line 244 and to also supply the plating
solution to the cathode chamber 112 through the circulation line
122.
[0115] FIG. 15 is a vertical cross-sectional view of a copper
plating unit 34g according to yet another embodiment. The copper
plating unit 34g of this embodiment differs from the copper plating
unit 34f shown in FIG. 14 in that the plating solution supply line
244 is not coupled to the anode chamber 110 and coupled only to the
circulation line 122, and that a connecting line 250 connecting the
circulation line 122 to the plating solution discharge line 190 is
provided. The connecting line 250 is provided with a second supply
valve 247. The first supply valve 246 and the second supply valve
247 are usually closed. Only at the time of preparation of the
plating bath, the first supply valve 246 and the second supply
valve 247 are opened to supply the plating solution to the anode
chamber 110 and the cathode chamber 112 through the plating
solution discharge line 190 and the circulation line 122,
respectively.
[0116] While the embodiments have been described above, it should
be understood that the present invention is not limited to the
embodiments described above, and is capable of various changes and
modifications within the scope of the inventive concept as
expressed herein.
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