U.S. patent application number 15/426631 was filed with the patent office on 2017-08-10 for apparatus and method for supplying plating solution to plating tank, plating system, powder container, and plating method.
The applicant listed for this patent is EBARA CORPORATION. Invention is credited to Yuji ARAKI, Chunhui DOU, Jumpei FUJIKATA, Yoshitaka MUKAIYAMA, Masashi SHIMOYAMA.
Application Number | 20170226656 15/426631 |
Document ID | / |
Family ID | 59498160 |
Filed Date | 2017-08-10 |
United States Patent
Application |
20170226656 |
Kind Code |
A1 |
DOU; Chunhui ; et
al. |
August 10, 2017 |
APPARATUS AND METHOD FOR SUPPLYING PLATING SOLUTION TO PLATING
TANK, PLATING SYSTEM, POWDER CONTAINER, AND PLATING METHOD
Abstract
An improved apparatus for adding powder comprising at least a
metal, such as copper, to a plating solution, and supplying the
plating solution to a plating tank is disclosed. The apparatus
includes a hopper having an inlet which is connectable to a powder
conduit of a powder container holding the powder therein, a feeder
which communicates with a bottom opening of the hopper, a motor
coupled to the feeder, and a plating-solution tank coupled to an
outlet of the feeder and configured to dissolve the powder in the
plating solution.
Inventors: |
DOU; Chunhui; (Tokyo,
JP) ; MUKAIYAMA; Yoshitaka; (Tokyo, JP) ;
ARAKI; Yuji; (Tokyo, JP) ; SHIMOYAMA; Masashi;
(Tokyo, JP) ; FUJIKATA; Jumpei; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EBARA CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
59498160 |
Appl. No.: |
15/426631 |
Filed: |
February 7, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 17/001 20130101;
C25D 17/02 20130101; C25D 21/18 20130101; C25D 3/38 20130101; C25D
17/00 20130101; C25D 21/14 20130101; C25D 21/10 20130101 |
International
Class: |
C25D 21/14 20060101
C25D021/14; C25D 3/38 20060101 C25D003/38; C25D 17/00 20060101
C25D017/00; C25D 17/02 20060101 C25D017/02; C25D 21/18 20060101
C25D021/18 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2016 |
JP |
2016-023224 |
Nov 11, 2016 |
JP |
2016-220952 |
Claims
1. An apparatus for supplying a plating solution, in which powder
comprising at least a metal to be used in plating has been
dissolved, to a plating tank, comprising: a hopper having an inlet
which is connectable to a powder conduit of a powder container
holding the powder therein; a feeder which communicates with a
bottom opening of the hopper; a motor coupled to the feeder; and a
plating-solution tank coupled to an outlet of the feeder and
configured to dissolve the powder in the plating solution.
2. The apparatus according to claim 1, further comprising: a weight
measuring device configured to measure a weight of the hopper and
the feeder; and an operation controller configured to control an
operation of the motor based on a change in a measured value of the
weight.
3. The apparatus according to claim 2, wherein the operation
controller is configured to calculate an amount of the powder added
to the plating solution from a change in the measured value of the
weight, and instruct the motor to operate until the amount of the
added powder reaches a target value.
4. The apparatus according to claim 1, wherein the inlet of the
hopper has a connecting seal whose inner diameter gradually
decreases with a distance from a distal end of the inlet.
5. The apparatus according to claim 4, wherein the connecting seal
is composed of an elastic material.
6. The apparatus according to claim 1, further comprising: an
airtight chamber in which the inlet of the hopper is located, the
airtight chamber including a door which allows the powder container
to be carried into the airtight chamber, and a glove which
constitutes part of a wall of the airtight chamber.
7. The apparatus according to claim 6, wherein the airtight chamber
further includes an exhaust port for connecting an interior space
to a negative-pressure source.
8. The apparatus according to claim 6, wherein a vibrating device
capable of vibrating the powder container is disposed in the
airtight chamber.
9. The apparatus according to claim 6, wherein a vacuum clamp
capable of holding the powder container is disposed in the airtight
chamber.
10. The apparatus according to claim 1, wherein the
plating-solution tank includes an agitation device for agitating
the plating solution.
11. The apparatus according to claim 10, wherein the
plating-solution tank includes an agitation tank in which the
agitation device is disposed, and an overflow tank coupled to a
through-hole formed in a lower portion of the agitation tank.
12. The apparatus according to claim 11, wherein the
plating-solution tank further includes a detour passage located
adjacent to the overflow tank.
13. The apparatus according to claim 11, wherein the
plating-solution tank further includes a plurality of baffle plates
disposed in the overflow tank, the plurality of baffle plates being
staggered.
14. The apparatus according to claim 1, further comprising: an
enclosure cover that surrounds connection portions of the feeder
and the plating-solution tank; and an inert-gas supply line which
communicates with an interior of the enclosure cover.
15. A plating system comprising: a plurality of plating tanks each
for plating a substrate; a plating-solution supply apparatus
including (i) a hopper having an inlet which is connectable to a
powder conduit of a powder container holding therein powder
comprising at least a metal to be used in plating of the substrate,
(ii) a feeder which communicates with a bottom opening of the
hopper, (iv) a motor coupled to the feeder, and (v) a
plating-solution tank coupled to an outlet of the feeder and
configured to dissolve the powder in a plating solution; and a
plating-solution supply pipe extending from the plating-solution
supply apparatus to the plating tanks.
16. The plating system according to claim 15, further comprising: a
plating-solution return pipe extending from the plating tanks to
the plating-solution supply apparatus.
17. A method of supplying powder, comprising at least a metal to be
used in plating, to a plating solution, comprising: coupling a
powder conduit of a powder container, holding the powder therein,
to an inlet of a hopper; supplying the powder from the powder
container to the hopper; operating a feeder which communicates with
a bottom opening of the hopper while measuring a weight of the
feeder and the hopper in which the powder is stored; and adding the
powder to the plating solution by the feeder based on a change in a
measured value of the weight.
18. The method according to claim 17, further comprising: agitating
the plating solution to which the powder has been added.
19. The method according to claim 17, further comprising:
calculating an amount of the powder added to the plating solution
from a change in the measured value of the weight; and operating
the feeder until the amount of the added powder reaches a target
value.
20. A powder container for holding powder comprising at least a
metal to be used in plating, comprising: a container body capable
of holding the powder therein; a powder conduit coupled to the
container body; and a valve attached to the powder conduit.
21. The powder container according to claim 20, wherein a distal
end of the powder conduit has a shape of a truncated cone.
22. A method of plating a substrate, comprising: delivering a
plating solution from a plating tank to a plating-solution tank;
calculating an amount of powder to be added to the plating solution
held in the plating-solution tank based on a metal ion
concentration in the plating solution in the plating tank, the
powder comprising at least a metal to be used in plating; supplying
the powder to the plating solution held in the plating-solution
tank; dissolving the powder in the plating solution held in the
plating-solution tank; supplying the plating solution, in which the
powder has been dissolved, from the plating-solution tank to the
plating tank; bringing a substrate into contact with the plating
solution held in the plating tank; and causing an electrochemical
reaction in the plating solution held in the plating tank to
deposit the metal on a surface of the substrate.
23. The method according to claim 22, wherein the plating tank
comprises a plurality of plating tanks, and wherein the plating
solution is supplied from the plating-solution tank to each of the
plating tanks while controlling a flow rate of the plating
solution.
24. The method according to claim 22, wherein: the plating tank
comprises a plurality of plating tanks, and a metal ion
concentration in the plating solution in the plurality of plating
tanks is continually monitored; and when the metal ion
concentration has become lower than a predetermined value, the
plating solution in the plating tanks is delivered to the
plating-solution tank, while the plating solution in the
plating-solution tank is supplied to one of the plurality of
plating tanks.
25. A non-transitory computer-readable storage medium that stores a
computer program for performing a method of electroplating a
substrate, the method comprising: delivering a plating solution
from a plating tank to a plating-solution tank; supplying powder to
the plating solution held in the plating-solution tank, the powder
comprising at least a metal to be used in plating; dissolving the
powder in the plating solution held in the plating-solution tank;
supplying the plating solution, in which the powder has been
dissolved, from the plating-solution tank to the plating tank;
bringing a substrate into contact with the plating solution held in
the plating tank; and causing an electrochemical reaction in the
plating solution held in the plating tank to deposit the metal on a
surface of the substrate.
26. A non-transitory computer-readable storage medium that stores a
computer program for performing a method of electroplating a
substrate, the method comprising: monitoring whether a
concentration of metal ions contained in a plating solution in a
plating tank is lower than a predetermined value; calculating an
amount of powder to be added to the plating solution when the
concentration of metal ions is lower than the predetermined value,
the powder comprising at least a metal; delivering the plating
solution from the plating tank to a plating-solution tank;
supplying the powder to the plating solution held in the
plating-solution tank until an amount of the added powder reaches
the calculated amount; dissolving the powder in the plating
solution held in the plating-solution tank; supplying the plating
solution, in which the powder has been dissolved, from the
plating-solution tank to the plating tank; bringing a substrate
into contact with the plating solution held in the plating tank;
and causing an electrochemical reaction in the plating solution
held in the plating tank to deposit the metal on a surface of the
substrate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This document claims priorities to Japanese Patent
Application Number 2016-023224 filed Feb. 10, 2016 and Japanese
Patent Application Number 2016-220952 filed Nov. 11, 2016, the
entire contents of which are hereby incorporated by reference.
BACKGROUND
[0002] The present invention relates to an apparatus and a method
for supplying a plating solution to a plating tank. The present
invention also relates to a plating system having such an
apparatus. The present invention also relates to a powder container
for holding metal powder to be used in plating. Further, the
present invention relates to a method of plating a substrate using
a plating solution to which metal powder for use in plating has
been added.
[0003] As electronics are becoming smaller in size, higher speed,
and less power consumption, interconnect patterns in a
semiconductor device are becoming finer and finer. With the
progress toward finer interconnect patterns, materials used for
interconnects are changing from conventional aluminum and aluminum
alloys to copper and copper alloys. The resistivity of copper is
1.67 .mu..OMEGA.cm, which is about 37% lower than the resistivity
(2.65.mu..OMEGA.cm) of aluminum. Therefore, compared to aluminum
interconnects, copper interconnects can not only reduce power
consumption, but can also be made finer with the same interconnect
resistance. In addition, because of the lower resistance, copper
interconnects have the advantage of reduced signal delay.
[0004] Filling of copper into trenches is generally performed by
electroplating which can form a film faster than PVC or CVD. In the
electroplating, a voltage is applied between a substrate and an
anode in the presence of a plating solution to deposit a copper
film on a low-resistance seed layer (or a feeding layer) which has
been formed in advance on the substrate. Such a seed layer is
generally comprised of a thin copper film (copper seed layer)
formed by, for example, PVD. Since there is a demand for a thinner
seed layer with the progress toward finer interconnects, the
thickness of the seed layer, which is generally of the order of 50
nm, is expected to decrease to not more than 10 nm to 20 nm in the
future.
[0005] The applicant has proposed a plating apparatus that uses a
plurality of concentrically-divided separate anodes which are
individually connected to a plating power source (see Japanese
Patent Laid-Open Publication No. 2002-129383). According to this
plating apparatus, a current density of a centrally-located
separate anode is made higher than an outer separate anode for a
certain period of time when an initial plating film is formed on a
substrate, thereby preventing a plating current from concentrating
in the peripheral portion of the substrate, and allowing the
plating current to flow also in the central portion of the
substrate. This makes it possible to form a plating film having a
uniform thickness even when a sheet resistance is high. The
applicant has also proposed a plating technique that uses an
insoluble anode (see Japanese Patent Laid-Open Publication No.
2005-213610 and Japanese Patent Laid-Open Publication No.
2008-150631). An anode holder for holding the insoluble anode is
provided with a plating-solution discharge section for sucking and
discharging a plating solution out of an anode chamber, and is also
provided with a plating-solution injection section connected to a
plating-solution supply pipe extending from a plating-solution
supply apparatus.
[0006] In order to meet the recent demand for a smaller circuit
system using semiconductors, implementation of semiconductor
circuits in a package having approximately the same size as a chip
has come into practical use. A packaging method called wafer level
package (WLP) has been proposed as a method to perform
implementation of semiconductor circuits in such a package. The
wafer level package is generally classified into fan-in technique
(also called WLCSP (Wafer-Level Chip-Scale Package)) and fan-out
technique. The fan-in WLP is a technique for providing external
electrodes (external terminals) in a chip-size area. The fan-out
WLP, on the other hand, is a technique for providing external
terminals in an area larger than a chip, for example, forming a
re-distribution layer and external electrodes on a substrate formed
of an insulating resin in which a plurality of chips are embedded.
An electroplating technique is sometimes used for forming a
re-distribution layer, an insulating layer, etc. on a wafer, and is
expected to be applied also in the fan-out WLP. A higher level of
technique, especially in control of a plating solution, is required
in order to apply the electroplating technique in the fan-out WLP
or the like for which finer pitches are strongly required.
[0007] With a view to performing so-called bottom-up plating, the
applicant has proposed a method of plating a substrate, such as a
wafer, while preventing a generation of an electrolyte component
which inhibits bottom-up plating (see Japanese Patent Laid-Open
Publication No. 2016-074975). This method involves bringing an
insoluble anode and a substrate into contact with a copper sulfate
plating solution containing additives, and applying a predetermined
plating voltage from a plating power source to between the
substrate and the insoluble anode to plate the substrate.
[0008] On the other hand, in order to replenish a plating solution
with objective metal ions in a plating apparatus which uses an
insoluble anode as described above, it is conceivable to use a
method in which a powdery metal salt is fed into a circulation tank
or a method in which metal pieces are dissolved in a separate tank
for replenishment. When the powdery metal salt is supplied into a
plating solution, fine particles increases in the plating solution
and may cause a defect in a surface of a plated substrate. In view
of this, the applicant has proposed a technique which can keep
concentrations of components of a plating solution constant over a
long period of time in a plating apparatus that uses an insoluble
anode (see Japanese Patent Laid-Open Publication No. 2007-051362).
This technique, which involves circulating and reusing a plating
solution while recovering the plating solution, can minimize the
amount of the plating solution used. Further, the use of an
insoluble anode can eliminate the need for replacement of the
anode, thereby facilitating maintenance and management of the
anode. Furthermore, the concentration of a component(s) of the
plating solution, which changes with the circulation and reuse of
the plating solution, can be maintained within a certain range by
supplying a replenishing solution, containing the plating solution
component(s) at a concentration high than the plating solution, to
the plating solution.
[0009] When plating of a substrate with copper is performed using
an insoluble anode, copper ions in a plating solution decrease
gradually. It is therefore necessary for a plating-solution supply
apparatus to adjust the copper ion concentration in the plating
solution. One possible method to replenish the plating solution
with copper is to add copper oxide powder to the plating solution.
However, if the powder scatters in a semiconductor manufacturing
plant, it will cause pollution of a clean room. Further, the
plating-solution supply apparatus is required to add a necessary
amount of copper oxide powder to the plating solution without
decreasing the throughput. In addition, there is an increasing
demand for a plating technique which can form a higher-quality
copper film on a substrate with use of such a plating solution to
which copper oxide has been added.
SUMMARY OF THE INVENTION
[0010] In one embodiment, there is provided an improved apparatus
and method for adding powder comprising at least a metal, such as
copper, to a plating solution, and supplying the plating solution
to a plating tank. In one embodiment, there is provided a plating
system including such an apparatus. In one embodiment, there is
provided a powder container for holding therein powder comprising
at least a metal, such as copper, to be used in the above-described
apparatus. In one embodiment, there is provided a plating method
which can form a higher-quality metal film on a substrate with use
of a plating solution to which powder comprising at least a metal,
such as copper, has been added.
[0011] According to an embodiment, there is provided an apparatus
for supplying a plating solution, in which powder comprising at
least a metal to be used in plating has been dissolved, to a
plating tank, comprising: a hopper having an inlet which is
connectable to a powder conduit of a powder container holding the
powder therein; a feeder which communicates with a bottom opening
of the hopper; a motor coupled to the feeder; and a
plating-solution tank coupled to an outlet of the feeder and
configured to dissolve the powder in the plating solution.
[0012] In an embodiment, the apparatus further comprises: a weight
measuring device configured to measure a weight of the hopper and
the feeder; and an operation controller configured to control an
operation of the motor based on a change in a measured value of the
weight.
[0013] In an embodiment, the operation controller is configured to
calculate an amount of the powder added to the plating solution
from a change in the measured value of the weight, and instruct the
motor to operate until the amount of the added powder reaches a
target value.
[0014] In an embodiment, the inlet of the hopper has a connecting
seal whose inner diameter gradually decreases with a distance from
a distal end of the inlet.
[0015] In an embodiment, the connecting seal is composed of an
elastic material.
[0016] In an embodiment, the apparatus further comprises an
airtight chamber in which the inlet of the hopper is located, the
airtight chamber including a door which allows the powder container
to be carried into the airtight chamber, and a glove which
constitutes part of a wall of the airtight chamber.
[0017] In an embodiment, the airtight chamber further includes an
exhaust port for connecting an interior space to a
negative-pressure source.
[0018] In an embodiment, a vibrating device capable of vibrating
the powder container is disposed in the airtight chamber.
[0019] In an embodiment, a vacuum clamp capable of holding the
powder container is disposed in the airtight chamber.
[0020] In an embodiment, the plating-solution tank includes an
agitation device for agitating the plating solution.
[0021] In an embodiment, the plating-solution tank includes an
agitation tank in which the agitation device is disposed, and an
overflow tank coupled to a through-hole formed in a lower portion
of the agitation tank.
[0022] In an embodiment, the plating-solution tank further includes
a detour passage located adjacent to the overflow tank.
[0023] In an embodiment, the plating-solution tank further includes
a plurality of baffle plates disposed in the overflow tank, the
plurality of baffle plates being staggered.
[0024] In an embodiment, the apparatus further comprises: an
enclosure cover that surrounds connection portions of the feeder
and the plating-solution tank; and an inert-gas supply line which
communicates with an interior of the enclosure cover.
[0025] According to one embodiment, there is provided a plating
system comprising: a plurality of plating tanks each for plating a
substrate; a plating-solution supply apparatus including (i) a
hopper having an inlet which is connectable to a powder conduit of
a powder container holding therein powder comprising at least a
metal to be used in plating of the substrate, (ii) a feeder which
communicates with a bottom opening of the hopper, (iv) a motor
coupled to the feeder, and (v) a plating-solution tank coupled to
an outlet of the feeder and configured to dissolve the powder in a
plating solution; and a plating-solution supply pipe extending from
the plating-solution supply apparatus to the plating tanks.
[0026] In an embodiment, the plating system further comprises a
plating-solution return pipe extending from the plating tanks to
the plating-solution supply apparatus.
[0027] According to one embodiment, there is provided a method of
supplying powder, comprising at least a metal to be used in
plating, to a plating solution, comprising: coupling a powder
conduit of a powder container, holding the powder therein, to an
inlet of a hopper; supplying the powder from the powder container
to the hopper; operating a feeder which communicates with a bottom
opening of the hopper while measuring a weight of the feeder and
the hopper in which the powder is stored; and adding the powder to
the plating solution by the feeder based on a change in a measured
value of the weight.
[0028] In an embodiment, the method further comprises agitating the
plating solution to which the powder has been added.
[0029] In an embodiment, the method further comprises: calculating
an amount of the powder added to the plating solution from a change
in the measured value of the weight; and operating the feeder until
the amount of the added powder reaches a target value.
[0030] According to one embodiment, there is provided a powder
container for holding powder comprising at least a metal to be used
in plating, comprising: a container body capable of holding the
powder therein; a powder conduit coupled to the container body; and
a valve attached to the powder conduit.
[0031] In an embodiment, a distal end of the powder conduit has a
shape of a truncated cone.
[0032] According to one embodiment, there is provided a method of
plating a substrate, comprising: delivering a plating solution from
a plating tank to a plating-solution tank; calculating an amount of
powder to be added to the plating solution held in the
plating-solution tank based on a metal ion concentration in the
plating solution in the plating tank, the powder comprising at
least a metal to be used in plating; supplying the powder to the
plating solution held in the plating-solution tank; dissolving the
powder in the plating solution held in the plating-solution tank;
supplying the plating solution, in which the powder has been
dissolved, from the plating-solution tank to the plating tank;
bringing a substrate into contact with the plating solution held in
the plating tank; and causing an electrochemical reaction in the
plating solution held in the plating tank to deposit the metal on a
surface of the substrate.
[0033] In an embodiment, the plating tank comprises a plurality of
plating tanks, and wherein the plating solution is supplied from
the plating-solution tank to each of the plating tanks while
controlling a flow rate of the plating solution.
[0034] In an embodiment, the plating tank comprises a plurality of
plating tanks, and a metal ion concentration in the plating
solution in the plurality of plating tanks is continually
monitored; and when the metal ion concentration has become lower
than a predetermined value, the plating solution in the plating
tanks is delivered to the plating-solution tank, while the plating
solution in the plating-solution tank is supplied to one of the
plurality of plating tanks.
[0035] According to one embodiment, there is provided a
non-transitory computer-readable storage medium that stores a
computer program for performing a method of electroplating a
substrate, the method comprising: delivering a plating solution
from a plating tank to a plating-solution tank; supplying powder to
the plating solution held in the plating-solution tank, the powder
comprising at least a metal to be used in plating; dissolving the
powder in the plating solution held in the plating-solution tank;
supplying the plating solution, in which the powder has been
dissolved, from the plating-solution tank to the plating tank;
bringing a substrate into contact with the plating solution held in
the plating tank; and causing an electrochemical reaction in the
plating solution held in the plating tank to deposit the metal on a
surface of the substrate.
[0036] According to one embodiment, there is provided a
non-transitory computer-readable storage medium that stores a
computer program for performing a method of electroplating a
substrate, the method comprising: monitoring whether a
concentration of metal ions contained in a plating solution in a
plating tank is lower than a predetermined value; calculating an
amount of powder to be added to the plating solution when the
concentration of metal ions is lower than the predetermined value,
the powder comprising at least a metal; delivering the plating
solution from the plating tank to a plating-solution tank;
supplying the powder to the plating solution held in the
plating-solution tank until an amount of the added powder reaches
the calculated amount; dissolving the powder in the plating
solution held in the plating-solution tank; supplying the plating
solution, in which the powder has been dissolved, from the
plating-solution tank to the plating tank; bringing a substrate
into contact with the plating solution held in the plating tank;
and causing an electrochemical reaction in the plating solution
held in the plating tank to deposit the metal on a surface of the
substrate.
[0037] The above-described embodiments can provide an apparatus and
a method which can add the powder to a plating solution and
dissolve the powder in the plating solution while preventing
scattering of the powder. Further, according to the above-described
embodiments, a high-quality metal film (e.g. copper film) can be
formed on a substrate using a plating solution to which powder
comprising at least a metal, such as copper, has been added.
[0038] The powder container, the plating system, and the plating
method described above can be used also when a substrate is to be
plated with a metal species such as indium, nickel, cobalt, or
ruthenium, other than copper. Examples of powders usable in such a
case may include: sulfates such as indium sulfate, nickel sulfate
and cobalt sulfate; sulfamates such as nickel sulfamate and cobalt
sulfamate; halides such as nickel bromide, nickel chloride and
cobalt chloride; and indium oxide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a schematic overall view of a plating system
according to a first embodiment;
[0040] FIG. 2 is a side view of a powder container capable of
holding copper oxide powder therein;
[0041] FIG. 3 is a view showing the powder container with a cap off
and a valve open;
[0042] FIG. 4 is a perspective view of an airtight chamber;
[0043] FIG. 5 is a view showing the interior of the airtight
chamber;
[0044] FIG. 6 is a view showing a distal end of a powder conduit of
the powder container and an inlet of a hopper;
[0045] FIG. 7 is a view showing the distal end of the powder
conduit of the powder container and the inlet of the hopper when
they are in tight contact with each other;
[0046] FIG. 8 is a flow chart showing processes of supplying copper
oxide powder from the powder container to the hopper;
[0047] FIG. 9 is a side view showing the hopper and a feeder;
[0048] FIG. 10 is a perspective view of a plating-solution
tank;
[0049] FIG. 11 is a plan view of the plating-solution tank;
[0050] FIG. 12 is a vertical cross-sectional view of the
plating-solution tank as viewed in a direction of arrow A shown in
FIG. 11;
[0051] FIG. 13 is a schematic view of another embodiment of a
plating-solution tank;
[0052] FIG. 14 is a schematic view of yet another embodiment of a
plating-solution tank;
[0053] FIG. 15 is a diagram showing results of an experiment which
was conducted to examine the influence of the number of baffle
plates on dissolution of copper oxide powder;
[0054] FIG. 16 is a schematic overall view of a plating system
according to a second embodiment;
[0055] FIG. 17 is a flow chart showing a control sequence for
adding copper oxide powder to a plating solution in the plating
system according to the first embodiment; and
[0056] FIG. 18 is a flow chart showing a control sequence for
adding copper oxide powder to a plating solution in the plating
system according to the second embodiment.
DESCRIPTION OF EMBODIMENTS
[0057] Embodiments will now be described with reference to the
drawings. FIG. 1 is a schematic overall view of a plating system
according to a first embodiment. The plating system includes a
plating apparatus 1 installed in a clean room, and a
plating-solution supply apparatus 20 installed in a downstairs
room. In this embodiment, the plating apparatus 1 is an
electroplating unit for electroplating a substrate (e.g., a wafer)
with copper, and the plating-solution supply apparatus 20 is a
plating-solution supply unit for supplying powder, comprising at
least copper, into a plating solution to be used in the plating
apparatus 1. In this embodiment, copper oxide powder is used as the
powder comprising at least copper, while it is also possible to use
pelletized materials comprising at least copper. In this
embodiment, an average particle size of the copper oxide powder is
in the range of 10 micrometers to 200 micrometers, more preferably
in the range of 15 micrometers to 50 micrometers. If the average
particle size is too small, the powder is likely to scatter as
dust. On the other hand, if the average particle size is too large,
the solubility of the powder, when fed into a plating solution, may
be poor.
[0058] In this specification, the term "powder" or "particles"
herein encompasses solid particles, shaped granular materials,
pelletized solid materials, small-diameter solid copper balls, a
strip-shaped material obtained by shaping solid copper into a
ribbon-like or tape-like shape, or a combination thereof.
[0059] The plating apparatus 1 has four plating tanks 2. Each
plating tank 2 includes an inner tank 5 and an outer tank 6. An
insoluble anode 8, held by an anode holder 9, is disposed in the
inner tank 5. Further, in the plating tank 2, a neutral membrane
(not shown) is disposed around the insoluble anode 8. The inner
tank 5 is filled with a plating solution, which is allowed to
overflow the inner tank 5 into the outer tank 6. The inner tank 5
is also provided with a agitation paddle (not shown) comprised of a
rectangular plate-like member having a constant thickness of 3 mm
to 5 mm, made of a resin such as PVC, PP or PTFE, or a metal, such
as stainless steel or titanium, coated with a fluororesin or the
like. The agitation paddle reciprocates parallel to a substrate W
to agitate the plating solution, so that sufficient copper ions and
additives can be supplied uniformly to a surface of the substrate
W.
[0060] The substrate W, such as a wafer, is held by a substrate
holder 11 and is immersed, together with the substrate holder 11,
in the plating solution held in the inner tank 5 of the plating
tank 2. The substrate W, as an object to be plated, may be a
semiconductor substrate, a printed circuit board, etc. In the case
of using a semiconductor substrate as the substrate W, the
semiconductor substrate is flat or substantially flat (a substrate
having a groove(s), a tube(s), a resist pattern(s), etc. is herein
regarded as substantially flat). When plating such a flat object,
it is necessary to control a plating condition over time in
consideration of the in-plane uniformity of a plating film formed
on the substrate, while preventing a deterioration in the quality
of the film.
[0061] The insoluble anode 8 is electrically connected via the
anode holder 9 to a positive pole of a plating power source 15,
while the substrate W held by the substrate holder 11 is
electrically connected via the substrate holder 11 to a negative
pole of the plating power source 15. When a voltage is applied from
the plating power source 15 between the insoluble anode 8 and the
substrate W that are both immersed in the plating solution, an
electrochemical reaction occurs in the plating solution held in the
plating tank 2, whereby copper is deposited on the surface of the
substrate W. In this manner, the surface of the substrate W is
plated with copper. The plating apparatus 1 may have less than four
or more than four plating tanks 2.
[0062] The plating apparatus 1 includes a plating controller 17 for
controlling the plating process of the substrate W. The plating
controller 17 has a function of calculating a concentration of
copper ions contained in the plating solution in each plating tank
2 from a cumulative value of electric current that has flowed in
the substrate W. Copper in the plating solution is consumed as the
substrate W is plated. The consumption of copper is proportional to
the cumulative value of electric current that has flowed in the
substrate W. The plating controller 17 can therefore calculate the
copper ion concentration in the plating solution in each plating
tank 2 from the cumulative value of electric current.
[0063] The plating-solution supply apparatus 20 includes an
airtight chamber 24 into which a powder container 21, holding
copper oxide powder therein, is to be carried, a hopper 27 for
storing the copper oxide powder supplied from the powder container
21, a feeder 30 which communicates with a bottom opening of the
hopper 27, a motor 31 coupled to the feeder 30, a plating-solution
tank 35 coupled to an outlet of the feeder 30 and configured to
dissolve the copper oxide powder in a plating solution, and an
operation controller 32 for controlling the operation of the motor
31. The feeder 30 is actuated by the motor 31. An acidic copper
sulfate plating solution containing sulfuric acid, copper sulfate,
halogen ions, and organic additives, in particular a plating
accelerator e.g. comprising SPS (bis(3-sulfopropyl) disulfide), a
suppressor e.g. comprising PEG (polyethylene glycol) and a leveler
e.g. comprising PEI (polyethylenimine), may be used as the plating
solution. Chloride ions are preferably used as the halogen
ions.
[0064] The plating apparatus 1 and the plating-solution supply
apparatus 20 are coupled to each other by a plating-solution supply
pipe 36 and a plating-solution return pipe 37. More specifically,
the plating-solution supply pipe 36 extends from the
plating-solution tank 35 to a bottom of the inner tank 5 of each
plating tank 2. The plating-solution supply pipe 36 is divided into
four branch pipes 36a, which are coupled to the bottoms of the
inner tanks 5 of the four plating tanks 2, respectively. The four
branch pipes 36a are provided with respective flow meters 38 and
respective flow control valves 39. The flow meters 38 and the flow
control valves 39 are coupled to the plating controller 17. The
plating controller 17 is configured to control a degree of opening
of each flow control valve 39 based on a flow rate of the plating
solution measured by the flow meter 38. Therefore, the flow rates
of the plating solutions supplied to the plating tanks 2 through
the four branch pipes 36a are regulated by the flow control valves
39, provided upstream of the plating tanks 2, so that the flow
rates are kept substantially the same. The plating-solution return
pipe 37 extends from the bottom of the outer tank 6 of each plating
tank 2 to the plating-solution tank 35. The plating-solution return
pipe 37 has four discharge pipes 37a coupled to the bottoms of the
outer tanks 6 of the four plating tanks 2, respectively.
[0065] The plating-solution supply pipe 36 is provided with a pump
40 for delivering the plating solution, and a filter 41 disposed
downstream of the pump 40. The plating solution that was been used
in the plating apparatus 1 is delivered through the
plating-solution return pipe 37 to the plating-solution supply
apparatus 20. The plating solution to which the copper oxide powder
has been added in the plating-solution supply apparatus 20 is fed
through the plating-solution supply pipe 36 to the plating
apparatus 1. The pump 40 may continually circulate the plating
solution between the plating apparatus 1 and the plating-solution
supply apparatus 20, or may intermittently deliver a predetermined
amount of the plating solution from the plating apparatus 1 to the
plating-solution supply apparatus 20, and may intermittently return
the plating solution, to which the copper oxide powder has been
added, from the plating-solution supply apparatus 20 to the plating
apparatus 1.
[0066] In order to replenish the plating solution with pure water
(DIW), a pure-water supply line 42 is coupled to the
plating-solution tank 35. This pure-water supply line 42 is
provided with an on-off valve 43 (which is usually open) for
stopping the supply of pure water when the operation of the plating
apparatus 1 is stopped, a flow meter 44 for measuring a flow rate
of the pure water, and a flow control valve 47 for controlling a
flow rate of the pure water. The flow meter 44 and the flow control
valve 47 are coupled to the plating controller 17. The plating
controller 17 is configured to control a degree of opening of the
flow control valve 47 to supply the pure water into the
plating-solution tank 35 in order to dilute the plating solution
when the copper ion concentration in the plating solution has
exceeded a set value.
[0067] The plating controller 17 is coupled to the operation
controller 32 of the plating-solution supply apparatus 20. The
plating controller 17 is configured to send a signal indicating a
replenishment demand value to the operation controller 32 of the
plating-solution supply apparatus 20 when the copper ion
concentration in the plating solution has become lower than a set
value. Upon receipt of the signal, the plating-solution supply
apparatus 20 adds the copper oxide powder to the plating solution
until the amount of the added copper oxide powder reaches the
replenishment demand value. Although in this embodiment the plating
controller 17 and the operation controller 32 are constructed as
separate devices, in one embodiment the plating controller 17 and
the operation controller 32 may be constructed as one controller.
In that case, the controller may be a computer that operates in
accordance with a program. The program may be stored in a storage
medium.
[0068] The plating apparatus 1 may include concentration measuring
devices 18a each for measuring the copper ion concentration in the
plating solution. The concentration measuring devices 18a are
attached to the four discharge pipes 37a of the plating-solution
return pipe 37, respectively. A measured value of the copper ion
concentration obtained by each concentration measuring device 18a
is sent to the plating controller 17. The plating controller 17 may
compare the above-described set value with a copper ion
concentration in the plating solution calculated from the
cumulative value of electric current as discussed previously, or
may compare the above-described set value with a copper ion
concentration measured by the concentration measuring device(s)
18a. The plating controller 17 may correct the calculated value of
the copper ion concentration based on a comparison of a copper ion
concentration in the plating solution, calculated from the
cumulative value of electric current (i.e., calculated value of the
copper ion concentration), with a copper ion concentration measured
by the concentration measuring device(s) 18a (i.e. measured value
of the copper ion concentration). For example, the plating
controller 17 may determine a correction factor by dividing a
measured value of the copper ion concentration by a calculated
value of the copper ion concentration, and correct a calculated
value of the copper ion concentration by multiplying the calculated
value by the correction factor. The correction factor may
preferably be updated periodically.
[0069] The plating-solution supply pipe 36 may have a branch pipe
36b, which is provided with a concentration measuring device 18b to
monitor the copper ion concentration in the plating solution. The
branch pipe 36b may be further provided with an analyzer(s) (e.g. a
CVS device or a colorimeter) to perform quantitative analysis and
monitoring of the concentration of a dissolved chemical
component(s) in addition to the copper ion. Such a construction
makes it possible to analyze the concentration of the chemical
component, e.g. an impurity, in the plating solution existing in
the plating-solution supply pipe 36 before the plating solution is
supplied to the plating tanks 2. This can prevent the dissolved
impurity from affecting the plating performance and can more ensure
highly-precise plating. Only one of the concentration measuring
devices 18a, 18b may be provided.
[0070] With the above-described construction, the plating system
according to the first embodiment can replenish the plating
solution with copper while keeping the copper ion concentration in
the plating solution substantially equal among the plating tanks
2.
[0071] FIG. 2 is a side view of the powder container 21 capable of
holding copper oxide powder therein. As shown in FIG. 2, the powder
container 21 includes a container body 45 capable of holding copper
oxide powder therein, a powder conduit 46 coupled to the container
body 45, and a valve 48 attached to the powder conduit 46. The
container body 45 is composed of a synthetic resin, such as
polyethylene. The container body 45 has a handle 49 so that a
worker can grip the handle 49 to carry the powder container 21.
While there is no particular limitation on the volume of the powder
container 21, the volume should be such that a worker can carry the
powder container 21 filled with the copper oxide powder. In one
example, the volume of the powder container 21 is 4 L. Not only
non-shaped copper oxide powder but pellets (granules) that have
been shaped from copper oxide powder can also be used as copper
oxide to be filled into the powder container 21. The use of the
pelletized copper oxide powder can more effectively prevent
scattering of dust.
[0072] The powder conduit 46 has been joined to the container body
45 by a joining technique, such as welding. The powder conduit 46
is comprised of a pipe that allows the copper oxide powder to pass
therethrough. The powder conduit 46 is inclined at an angle of
about 30 degrees with respect to the vertical direction. The copper
oxide powder can pass through the powder conduit 46 when the valve
48, mounted to the powder conduit 46, is open, while the copper
oxide powder cannot pass through the powder conduit 46 when the
valve 48 is closed. FIG. 2 shows the powder conduit 46 with the
valve 48 closed. A cap (or lid) 50 is attached to a distal end 46a
of the powder conduit 46.
[0073] FIG. 3 is a view showing the powder container 21 with the
cap 50 off and the valve 48 open. The copper oxide powder is fed
through the powder conduit 46 into the powder container 21 in the
state shown in FIG. 3. After the completion of feeding of the
copper oxide powder, the valve 48 is closed, and the cap 50 is
mounted on the distal end 46a of the powder conduit 46 (see FIG.
2). The powder container 21 with the valve 48 closed, filled with
the copper oxide powder, is carried into the airtight chamber 24
shown in FIG. 1.
[0074] FIG. 4 is a perspective view of the airtight chamber 24. In
this embodiment, the airtight chamber 24 is a rectangular box
capable of forming a hermetically-space therein. The airtight
chamber 24 includes a door 55 which allows the powder container 21
to be carried into the interior space of the airtight chamber 24,
and two gloves 56 which constitute part of a wall of the airtight
chamber 24. A mount frame on which the door 55 is mounted is
comprised of a member having a sealing function, such as a rubber,
so that the interior of the airtight chamber 24 can be hermetically
sealed. Each of the gloves 56 is comprised of a membrane formed by
a flexible material (e.g. synthetic rubber, such as polyvinyl
chloride) which can deform so as to follow a shape of a worker's
hand, and is configured to be able to project into the airtight
chamber 24 so that a worker can conduct operations inside the
airtight chamber 24. The two gloves 56 are located at both sides of
the door 55. The airtight chamber 24 has an exhaust port 58 for
connecting the interior space of the airtight chamber 24 to a
negative-pressure source. The negative-pressure source is, for
example, a vacuum pump. A negative pressure is created in the
airtight chamber 24 through the exhaust port 58.
[0075] FIG. 5 is a view showing the interior of the airtight
chamber 24. In the airtight chamber 24 are disposed a vacuum clamp
61 for holding the powder container 21 by vacuum suction, a
vibrating device 65 for vibrating the powder container 21, and a
pedestal 66 for supporting the powder container 21. The powder
container 21, with its powder conduit 46 facing downward, is set on
the vacuum clamp 61 and the pedestal 66. The vacuum clamp 61 is
secured to a frame 68, and the vibrating device 65 is secured to
the vacuum clamp 61. The vacuum clamp 61 has a vibration-proof
rubber 61a which is to make contact with the powder container 21.
The vibration-proof rubber 61a has a through-hole (not shown) in
which a vacuum is to be created. The operations of the vibrating
device 65 and the vacuum clamp 61 are controlled by the operation
controller 32 shown in FIG. 1.
[0076] The vacuum clamp 61 is coupled to an ejector 70 which is a
vacuum creating device. The ejector 70 and the vibrating device 65
are coupled to a compressed-air supply pipe 72. The compressed-air
supply pipe 72 is divided into two pipes; one is coupled to the
ejector 70, and the other is coupled to the vibrating device 65.
When compressed air is fed into the ejector 70, the ejector 70
creates a vacuum in the vacuum clamp 61, so that the powder
container 21 can be held on the vibration-proof rubber 61a of the
vacuum clamp 61 by vacuum suction. The vibrating device 65 is
configured to operate by the compressed air. The vibrating device
65 transmits the vibration to the powder container 21 through the
vacuum clamp 61, thereby vibrating the powder container 21 held by
the vacuum clamp 61. A frequency of vibration of the vibrating
device 65 is controlled by a vibration controller (not shown) of
the plating-solution supply apparatus 20. The vibration controller
may be comprised of the operation controller 32. The vibrating
device 65 may directly contact the side surface of the powder
container 21. In an embodiment, the vibrating device 65 may be an
electric vibrating device.
[0077] An inlet 26 of the hopper 27, which is connectable to the
powder container 21, is located in the airtight chamber 24. The
distal end 46a (see FIG. 3) of the powder conduit 46 of the powder
container 21 is inserted into the inlet 26 of the hopper 27 (see
FIGS. 6 and 7), whereby the distal end 46a of the powder conduit 46
of the powder container 21 is coupled to the inlet 26 of the hopper
27. When the valve 48 is opened after the powder conduit 46 and the
inlet 26 are coupled (see FIG. 7), the copper oxide powder in the
powder container 21 flows through the powder conduit 46 into the
inlet 26, and finally falls into the hopper 27.
[0078] A bridge phenomenon of copper oxide powder may occur in the
powder container 21 in the vicinity of the powder conduit 46. The
bridge phenomenon is a phenomenon in which the powder container 21
is clogged with the copper oxide powder due to an increase in the
density of the powder. In order to prevent such bridge phenomenon,
the vibrating device 65 vibrates the powder container 21, thereby
fluidizing the copper oxide powder in the powder container 21. The
frequency of the vibration of the vibrating device 65 may be in the
range of 1000 to 10000 per minute, more preferably 7000 to 8000 per
minute.
[0079] The powder conduit 46 is fixed at such a position on the
powder container 21 that the entirety of the powder container 21,
with its powder conduit 46 coupled to the inlet 26 of the hopper
27, is inclined. In particular, when the powder conduit 46 is
connected to the inlet 26 of the hopper 27, one side of the powder
container 21 is inclined at an angle of 50 to 70 degrees with
respect to a horizontal plane, while other side is inclined at an
angle of 20 to 40 degrees with respect to the horizontal plane. In
this manner, when the powder conduit 46 is coupled to the inlet 26
of the hopper 27, the right and left sides of the powder container
21 are inclined toward the powder conduit 46 at different angles.
Accordingly, the pressure of powder, which concentrates in the
vicinity of the powder conduit 46, differs between the right and
left sides of the powder conduit 46, thereby effectively preventing
the occurrence of the bridge phenomenon. Consequently, the copper
oxide powder can be quickly discharged and, in addition, is
unlikely to remain in the powder container 21.
[0080] FIG. 6 is a view showing the distal end 46a of the powder
conduit 46 of the powder container 21 and the inlet 26 of the
hopper 27. The distal end 46a of the powder conduit 46 has a shape
of a truncated cone. The inlet 26 of the hopper 27 has a shape
corresponding to the shape of the distal end 46a of the powder
conduit 46. More specifically, the inlet 26 of the hopper 27 has a
connecting seal 28 whose inner diameter gradually decreases with a
distance from a distal end (upper end) of the inlet 26. The
connecting seal 28 is composed of an elastic material, such as
rubber. As shown in FIG. 7, when the distal end 46a of the powder
conduit 46 is inserted into the inlet 26 of the hopper 27, the
distal end 46a of the powder conduit 46 comes into tight contact
with the connecting seal 28 of the inlet 26, so that a gap between
the distal end 46a of the powder conduit 46 and the inlet 26 of the
hopper 27 is sealed by the connecting seal 28. Scattering of the
copper oxide powder can therefore be prevented.
[0081] The operation of supplying the copper oxide powder from the
powder container 21 to the hopper 27 will now be described with
reference to FIG. 8. In step 1, the powder container 21, filled
with the copper oxide powder, is prepared. In step 2, the door 55
of the airtight chamber 24 is opened, and in step 3, the powder
container 21 is carried into the airtight chamber 24. The door 55
is closed in step 4 and, in step 5, a worker wears the gloves 56
and takes off the cap 50 of the powder container 21 in the airtight
chamber 24. In step 6, the powder conduit 46 of the powder
container 21 is coupled to the inlet 26 of the hopper 27, and in
step 7, the valve 48 of the powder container 21 is opened, and in
step 8 the powder container 21 is vibrated by the vibrating device
65 while the powder container 21 is held on the vacuum clamp 61.
The copper oxide powder in the powder container 21 is supplied
through the inlet 26 into the hopper 27. Upon completion of the
feeding of the copper oxide powder, the vibration of the powder
container 21 is stopped in step 9, the valve 48 is closed in step
10, and the vacuum suction of the powder container 21 by the vacuum
clamp 61 is stopped in step 11. In step 12, the powder container 21
is removed from the vacuum clamp 61 and the pedestal 66, and in
step 13 the cap 50 is attached to the powder conduit 46. In step
14, the door 55 is opened, and in step 15 the powder container 21
is taken out of the airtight chamber 24.
[0082] All the above steps 1 to 15 are performed while a negative
pressure is produced in the interior of the airtight chamber 24.
The powder container 21 is in the airtight chamber 24 from when the
valve 48 is opened to when the valve 48 is closed. Therefore, even
if the copper oxide powder spills from the powder container 21, the
copper oxide powder does not leak from the airtight chamber 24. A
volume of the hopper 27 is several times larger than the volume of
the powder container 21; therefore, the above steps 1 to 15 are
repeated until a sufficient amount of copper oxide powder is stored
in the hopper 27.
[0083] The hopper 27 and the feeder 30 will now be described. FIG.
9 is a side view showing the hopper 27 and the feeder 30. The
hopper 27 is a powder reservoir (or pellet reservoir) in which
copper oxide powder supplied from the powder container 21 is to be
stored. A lower half of the hopper 27 has a shape of a truncated
cone so that the copper oxide powder can flow downward smoothly. A
top opening of the hopper 27 is covered with a lid 74. The inlet
26, which is to be coupled to the powder conduit 46 of the powder
container 21, is secured to the lid 74. Further, an exhaust pipe 75
is secured to the lid 74. This exhaust pipe 75 communicates with
the interior space of the hopper 27, and further communicates with
a not-shown negative-pressure source. Therefore, a negative
pressure is created in the interior space of the hopper 27 through
the exhaust pipe 75.
[0084] The feeder 30 communicates with the bottom opening of the
hopper 27. In this embodiment, the feeder 30 is a screw feeder
having a screw 30a. The motor 31 is coupled to the feeder 3, so
that the feeder 30 is actuated by the motor 31. The hopper 27 and
the feeder 30 are secured to a bracket 73. This bracket 73 is
supported by a weight measuring device 80. The weight measuring
device 80 is configured to measure the total weight of the hopper
27, the feeder 30, the motor 31, and the copper oxide powder
present in the hopper 27 and the feeder 30.
[0085] The outlet 30b of the feeder 30 is coupled to the
plating-solution tank 35. When the motor 31 actuates the feeder 30,
the copper oxide powder in the hopper 27 is fed by the feeder 30
into the plating-solution tank 35. An enclosure cover 81, which
surrounds connection portions of the feeder 30 and the
plating-solution tank 35, is secured to the plating-solution tank
35. The outlet 30b of the feeder 30 is located inside the enclosure
cover 81. An inert-gas supply line 83 is coupled to the enclosure
cover 81, and communicates with the interior of the enclosure cover
81. The inert-gas supply line 83 supplies an inert gas, such as
nitrogen gas, into the enclosure cover 81 to fill the interior of
the enclosure cover 81 with the inert gas.
[0086] The inert gas is supplied into the enclosure cover 81 for
the following reason. The plating-solution tank 35 may be operated
such that the plating solution in the plating-solution tank 35 is
maintained at a high temperature. In such a case, a vapor generates
from the plating solution. The vapor rises and reaches the
connection portions of the feeder 30 and the plating-solution tank
35, and intrudes through the outlet 30b into the feeder 30. When
the vapor is adsorbed onto the copper oxide powder existing in the
feeder 30, the copper oxide powder can agglomerate and may clog the
feeder 30. In order to avoid this, the inert gas, such as nitrogen
gas, is injected into the enclosure cover 81 so as to expel the
vapor downward, thereby preventing the vapor from intruding into
the feeder 30.
[0087] The weight measuring device 80 is coupled to the operation
controller 32, which controls the operation of the motor 31. A
measured value of the weight outputted from the weight measuring
device 80 is sent to the operation controller 32. The operation
controller 32 receives the signal indicating the replenishment
demand value that has sent from the plating apparatus 1 (see FIG.
1), and instructs the motor 31 to operate until an amount of the
copper oxide powder, which has been added to the plating solution
in the plating-solution tank 35, reaches the replenishment demand
value, while calculating the amount of the added copper oxide
powder from a change in the measured value of the weight outputted
from the weight measuring device 80. The motor 31 actuates the
feeder 30, which adds the copper oxide powder, in the amount
corresponding to the replenishment demand value, to the plating
solution in the plating-solution tank 35. The replenishment demand
value is a value that varies depending on the copper ion
concentration in the plating solution so as to reflect the
consumption of copper ions in the plating solution held in the
plating tanks 2. The replenishment demand value is a target value
of an amount of copper oxide powder to be added to the plating
solution held in the plating-solution tank 35.
[0088] The plating controller 17 is configured to calculate the
replenishment demand value from the copper ion concentration in the
plating solution in the plating tanks 2 when the copper ion
concentration in the plating solution in the plating tanks 2 has
become lower than a set value. As described above, the copper ion
concentration in the plating solution in the plating tanks 2 may be
the copper ion concentration calculated from the cumulative value
of the electric current, or the copper ion concentration measured
by the concentration measuring device(s) 18a and/or the
concentration measuring device 18b.
[0089] If a large amount of copper oxide powder is added to the
plating solution in a short time, the copper oxide powder may
agglomerate before it is dissolved in the plating solution, and as
a result, the copper oxide powder may not be fully dissolved.
Moreover, if a rotational speed of the screw 30a of the feeder 30
is too high, the copper oxide powder may agglomerate in the feeder
30 and may form lumps which are hardly soluble in the plating
solution. In order to prevent the formation of such agglomerates
and lumps of the copper oxide powder, it is preferred to set an
upper limit of the rotational speed of the screw 30a. More
specifically, the operation controller 32 preferably controls the
motor 31 so that the screw 30a rotates at a rotational speed not
more than the preset upper limit.
[0090] The operation controller 32 may preferably issue an alarm
when an amount of copper oxide powder stored in the hopper 27 has
become small. More specifically, the operation controller 32 may
preferably issue an alarm when the measured value of the weight
outputted from the weight measuring device 80 has become lower than
a lower limit.
[0091] The plating-solution tank 35 will now be described. FIG. 10
is a perspective view of the plating-solution tank 35, FIG. 11 is a
plan view of the plating-solution tank 35, and FIG. 12 is a
vertical cross-sectional view of the plating-solution tank 35 as
viewed in a direction of arrow A shown in FIG. 11. The
plating-solution tank 35 includes an agitation tank 91 in which an
agitation device 85 is disposed, and an overflow tank 92 coupled to
a through-hole 95 formed in a lower portion of the agitation tank
91. The overflow tank 92 communicates with the agitation tank 91
through the through-hole 95. The plating-solution return pipe 37,
which is coupled to the plating tanks 2 as shown in FIG. 1, is
coupled to the agitation tank 91. Thus, the plating solution used
in the plating apparatus 1 of FIG. 1 is returned to the agitation
tank 91.
[0092] The outlet 30b of the feeder 30 is located above the
agitation tank 91, and the copper oxide powder is fed from the
feeder 30 into the agitation tank 91. The agitation device 85
includes agitating blades 86 disposed in the agitation tank 91, and
a motor 87 coupled to the agitating blades 86. The copper oxide
powder can be dissolved in the plating solution by the agitating
blades 86 which are rotated by the motor 87. The operation of the
agitation device 85 is controlled by the operation controller 32.
The overflow tank 92 is located adjacent to the agitation tank 91.
The plating solution to which the copper oxide powder has been
added flows from the agitation tank 91 into the overflow tank 92
through the through-hole 95. The through-hole 95 may be provided
with a filter to prevent passage of undissolved copper oxide
powder.
[0093] A detour passage 93 is provided adjacent to the overflow
tank 92. The plating solution overflows the overflow tank 92 into
the detour passage 93. The detour passage 93 in this embodiment is
a tortuous or meandering passage formed by a plurality of baffle
plates 88. Each baffle plate 88 has a cutout portion 88a formed in
one end. The cutout portions 88a of two adjacent baffle plates 88
are located at different positions with respect to a longitudinal
direction of the baffle plates 88. Accordingly, as illustrated by
arrows in FIG. 11, the flow of the plating solution to which the
copper oxide powder has been added meanders through the detour
passage 93. In one embodiment, the detour passage 93 may be formed
by a plurality of baffle plates 88 which are staggered and have no
cutout portions 88a.
[0094] The detour passage 93 is provided in order to ensure a
sufficient time for the copper oxide powder to be dissolved in the
plating solution. The time required for the plating solution to
pass through the detour passage 93 is preferably not less than 10
seconds. Such detour passage 93 enables the copper oxide powder to
be fully dissolved in the plating solution.
[0095] FIG. 13 is a schematic view of another embodiment of the
plating-solution tank 35. In this embodiment, baffle plates 88 are
installed in the overflow tank 92, and are staggered in the
vertical direction. A detour passage 93 for the plating solution is
formed by these baffle plates 88.
[0096] FIG. 14 is a schematic view of yet another embodiment of the
plating-solution tank 35. In this embodiment, an agitation tank 91
in which an agitation device 85 is disposed is installed in the
center of the plating-solution tank 35. An overflow tank 92 is
disposed outside the agitation tank 91 and communicates with a
through-hole 95 formed in the lower end of the agitation tank 91. A
detour passage 93 is provided adjacent to the overflow tank 92 and
is coupled to the plating-solution supply pipe 36. The detour
passage 93 is located outside the agitation tank 91 and the
overflow tank 92. In this embodiment, the detour passage 93 is a
spiral passage that extends spirally. The plating solution flows
from the agitation tank 91 into the overflow tank 92 through the
through-hole 95, and overflows the overflow tank 92 into the detour
passage 93. The plating solution that has flowed through the detour
passage 93 flows into the plating-solution supply pipe 36. The
detour passage 93 in a spiral shape, i.e., in a circular shape,
enables the plating solution to stay for a long time in the
plating-solution tank 35 without use of the baffle plates 88.
Further, there is no corner in the plating-solution tank 35. Thus,
there is no sedimentation of powder in a corner where the plating
solution is likely to stagnate. Furthermore, the plating-solution
tank 35 can be made compact.
[0097] In both the embodiment shown in FIGS. 11 and 12 and the
embodiment shown in FIG. 13, the time it takes for the plating
solution to pass through the detour passage 93 can be increased by
increasing the number of baffle plates 88. In the case of the
embodiment shown in FIG. 14 in which no baffle plate is provided,
the time it takes for the plating solution to pass through the
detour passage 93 can be increased by increasing the length of the
detour passage 93 as well.
[0098] FIG. 15 is a diagram (SEM diagram) showing results of an
experiment which was conducted to examine an influence of the
number of baffle plates on dissolution of copper oxide powder under
a room-temperature condition. In this experiment, a solution to
which copper oxide powder had been added was passed through the
detour passage 93 in which zero, one, two, or three baffle plates
were provided. After the passage of the solution, sediment of
copper oxide powder on the bottom of the detour passage 93 was
collected and microphotographed. FIG. 15 shows SEM images at
magnifications of 50 times, 100 times, and 150 times.
[0099] In view of a friction loss in the plating-solution supply
pipe 36 and a loss by a valve, a meter, a pipe joint, etc., the
flow velocity of the plating solution flowing in the
plating-solution tank 35 needs to be high to a certain degree in
order to increase the copper ion concentration in the plating
solution in the plating tanks 2. On the other hand, if the flow
velocity of the plating solution is too high, the copper oxide
powder may not be completely dissolved in the plating solution.
[0100] As can be seen from the experimental results shown in FIG.
15, almost no copper oxide powder remained in the detour passage 93
in the case of three baffle plates, whereas some copper oxide
powder remained in the detour passage 93 in the case of zero baffle
plate. These results show that the dissolution of copper oxide film
is improved as the number of baffle plates increases. The time it
takes for the plating solution to pass through the detour passage
93 was about 4 seconds in the case of zero baffle plate, about 8
seconds in the case of one baffle plate, about 12 seconds in the
case of two baffle plates, and about 16 seconds in the case of
three baffle plates.
[0101] These experimental results indicate that the time required
for the plating solution to pass through the detour passage 93
should be more than 10 seconds corresponding to the use of
one-and-a-half baffle plates, preferably more than about 12 seconds
corresponding to the use of two baffle plates, and more preferably
more than 16 seconds corresponding to the use of three baffle
plates.
[0102] While the influence of the number of baffle plates on the
dissolution of copper oxide powder has been described, an approach
to promote the dissolution of copper oxide powder is not limited to
the adjustment of the number of baffle plates. For example, it is
possible to install a heater in the plating-solution tank 35, e.g.
in the agitation tank 91, to promote the dissolution of copper
oxide powder in the plating solution. However, if the plating
solution is heated to a too high temperature, then coexisting
components, such as additives, in the plating solution can be
decomposed and deactivated. From this viewpoint, it is preferred to
set an upper limit of the temperature of the plating solution in
the agitation tank 91 to be not more than 50 C.degree. so as not to
cause decomposition of the additive(s). In the case of installing
such a heater for heating the plating solution, only one baffle
plate may be installed in the detour passage 93 so that it takes at
least about 8 seconds for the plating solution to pass through the
detour passage 93, or no baffle plate may be installed in the
plating-solution tank 35. The heater installed in the agitation
tank 91 makes it possible to fully dissolve the copper oxide powder
in the plating solution when the plating solution is merely passing
through the plating-solution tank 35.
[0103] A plating system according to a second embodiment will now
be described with reference to FIG. 16. The plating system
according to the second embodiment differs from the plating system
according to the first embodiment in that the four plating tanks 2
are coupled in series. More specifically, the outer tank 6 and the
inner tank 5 of each plating tank 2 are coupled to the inner tank 5
and the outer tank 6 of the adjacent plating tank 2 by a first
connection pipe 110 and a second connection pipe 112, respectively.
The first connection pipes 110 and the second connection pipes 112
are provided with pumps 113, respectively, for delivering the
plating solution.
[0104] The plating-solution supply pipe 36 is coupled to the inner
tank 5 of one of the four plating tanks 2, and the plating-solution
return pipe 37 is coupled to the outer tank 6 of another one of the
four plating tanks 2. The plating-solution supply pipe 36 is
provided with a flow meter 38 and a flow control valve 39, and the
plating-solution return pipe 37 is provided with a flow meter 115
and a plating-solution discharge valve 116. A concentration
measuring device 118 for measuring the copper ion concentration in
the plating solution is coupled to the outer tank 6 to which the
plating-solution return pipe 37 is coupled. The same reference
numerals are used for the same elements in the first embodiment,
and duplicate descriptions thereof are omitted.
[0105] The plating system according to the second embodiment
automatically measures the copper ion concentration in the plating
solution while keeping the copper ion concentration in the plating
solution substantially equal among the plating tanks 2. When it is
necessary to replenish the plating solution with copper, the
plating solution is delivered from the plating apparatus 1 to the
plating-solution supply apparatus 20, while the plating solution
containing copper in a relatively high concentration is supplied
from the plating-solution supply apparatus 20 in the downstairs
room to the plating apparatus 1.
[0106] A control sequence for adding copper oxide powder to the
plating solution in the plating system according to the first
embodiment will be described with reference to FIG. 17, and a
control sequence for adding copper oxide powder to the plating
solution in the plating system according to the second embodiment
will be described with reference to FIG. 18. In the plating system
according to the first embodiment, as shown in FIG. 17, in step 1,
when the copper ion concentration in the plating solution has
become lower than a set value, the plating controller 17 sends the
signal indicating the replenishment demand value to the operation
controller 32. In step 2, upon receipt of the signal, the operation
controller 32 instructs the motor 31 to operate until the amount of
copper oxide powder added to the plating solution reaches the
replenishment demand value, so that the feeder 30 adds the copper
oxide powder to the plating solution in the plating-solution tank
35 by the amount corresponding to the replenishment demand
value.
[0107] In step 3, the operation controller 32 activates the
agitation device 85, which agitates the plating solution to which
the copper oxide powder has been added. The operation controller 32
stops the agitating operation of the agitation device 85 when a
preset time has elapsed. In step 4, the plating solution to which
the copper oxide powder has been added flows through the overflow
tank 92 and the detour passage 93, while the copper oxide powder is
dissolved in the plating solution. In step 5, the plating solution
in which the copper oxide powder has been dissolved is supplied to
the plating tanks 2 of the plating apparatus 1 through the
plating-solution supply pipe 36. In this manner, the copper ion
concentration in the plating solution used in the plating apparatus
1 is maintained at a set value. According to this embodiment, a
necessary amount of copper oxide powder can be automatically added
to and dissolved in the plating solution, and a predetermined
amount of the plating solution can be supplied to each plating tank
2. Therefore, the copper ion concentration in the plating solution
in each plating tank 2 can be regulated and maintained at a
predetermined value without decreasing the throughput of the
plating apparatus 1.
[0108] In the plating system according to the second embodiment,
copper oxide powder is added to the plating solution in the
following manner. The copper ion concentration in the plating
solution held in the plating tanks 2 is continually measured by the
concentration measuring device 118, and the measured value of the
copper ion concentration is monitored by the plating controller 17.
As shown in FIG. 18, in step 1, when the copper ion concentration
in the plating solution in the plating tanks 2 has become lower
than a set value, the plating controller 17 sends the signal
indicating the replenishment demand value to the operation
controller 32 of the plating-solution supply apparatus 20. In step
2, the plating-solution discharge valve 116 for discharging the
plating solution from the plating tanks 2 is opened to deliver the
plating solution from the plating tanks 2 to the plating-solution
tank 35. This plating-solution discharge valve 116 is kept open for
a predetermined period of time so that the plating solution is
delivered in an amount of not more than the maximum volume of the
plating-solution tank 35.
[0109] In step 3, upon receipt of the above signal, the operation
controller 32 instructs the motor 31 to operate until the amount of
copper oxide powder added to the plating solution reaches the
replenishment demand value, so that the feeder 30 adds the copper
oxide powder, in an amount corresponding to the replenishment
demand value, to the plating solution in the plating-solution tank
35. Step 2 and step 3 may be performed simultaneously, or step 3
may be performed prior to step 2. In step 4, the operation
controller 32 activates the agitation device 85, which agitates the
plating solution to which the copper oxide powder has been added.
The operation controller 32 stops the agitating operation of the
agitation device 85 when a preset time has elapsed.
[0110] In step 5, the plating solution to which the copper oxide
powder has been added flows through the overflow tank 92 and the
detour passage 93, while the copper oxide powder is dissolved in
the plating solution. In step 6, the plating solution in which the
copper oxide powder has been dissolved is supplied to one of the
plating tanks 2 of the plating apparatus 1 through the
plating-solution supply pipe 36. The plating tanks 2 communicate
with each other through the first connection pipes 110 and the
second connection pipes 112, and the plating solution circulates
through all of the plating tanks 2 by the operations of the pumps
113 attached to the first connection pipes 110 and the second
connection pipes 112 that couple the plating tanks 2 to each other.
In this manner, the copper ion concentration in the plating
solution used in the plating apparatus 1 is maintained at a set
value.
[0111] As shown in FIG. 1, in the plating system according to the
first embodiment, the plating-solution supply pipe 36 has the
branch pipes 36a coupled to the plating tanks 2, respectively, and
the plating solutions having the same concentration are supplied to
the plating tanks 2. In the plating system according to the second
embodiment, the plating tanks 2 communicate with each other and the
plating-solution supply pipe 36 is coupled to one of the plating
tanks 2. Therefore, in both of these embodiments, the concentration
of the plating solution in the plating tanks 2 can be kept uniform.
According to these embodiments, a quality of a copper film formed
by plating can be improved and, in addition, a variation in the
results of plating among the plating tanks 2 can be prevented.
[0112] The average particle size of copper oxide powder (as
measured by a laser diffraction/scattering method) is preferably in
the range of 10 micrometers to 200 micrometers, more preferably in
the range of 20 micrometers to 100 micrometers. If the average
particle size is too small, copper oxide powder can scatter in the
air during the supply of the powder. If the average particle size
is too large, the powder may not be quickly dissolved in the
solution.
[0113] A plating method capable of forming a higher-quality copper
film on a substrate can be provided by using a plating solution to
which pelletized solid materials comprising metal copper have been
added. The use of such pelletized solid materials comprising metal
copper allows copper powder containing few impurities to coexist
with copper oxide powder, leading to an enhanced plating film
quality. Further, the use of such pellets can more effectively
prevent scattering of powder upon the supply of the powder.
[0114] While an alkali metal in a powder form is generally at risk
for firing or explosion, powder of metal copper is at low risk for
firing or explosion. Powder of metal copper can therefore be shaped
into pellets. As described above e.g. with reference to FIG. 1,
instead of or together with copper oxide powder, such pelletized
solid materials comprising metal copper can be supplied to the
plating-solution tank 35. It is also possible to use pellets of
metal copper together with pellets of copper oxide.
[0115] If the pelletized solid materials are too hard, such
materials can cause a trouble in the plating-solution supply
apparatus 20. If the pelletized solid materials are too soft, it is
possible that scattering of powder may not be effectively
prevented. Thus, it is preferred to use pellets having an
appropriate hardness.
[0116] While the pelletized solid materials have been described, it
is also possible for copper plating to use small-diameter solid
copper balls or a strip-shaped material, obtained by shaping solid
copper into a ribbon-like or tape-like shape. In that case, a shaft
of the feeder 30 may have a function of crushing such solid
materials.
[0117] While the powder container, the plating-solution supply
apparatus, etc. have been described with reference to the case of
plating a substrate with copper, the powder container, the plating
system and the plating method described above can be used also in a
case of plating a substrate with other metal such as indium.
[0118] The previous description of embodiments is provided to
enable a person skilled in the art to make and use the present
invention. Moreover, various modifications to these embodiments
will be readily apparent to those skilled in the art, and the
generic principles and specific examples defined herein may be
applied to other embodiments. Therefore, the present invention is
not intended to be limited to the embodiments described herein but
is to be accorded the widest scope as defined by limitation of the
claims.
* * * * *