U.S. patent application number 10/933353 was filed with the patent office on 2005-03-10 for method and apparatus for controlling electrolytic solution.
Invention is credited to Akahori, Masaji, Hodai, Masao, Ide, Kunihito, Kanda, Hiroyuki, Katsuoka, Seiji, Kinbara, Masaaki, Mishima, Koji, Nakagawa, Sota, Yamamoto, Satoru.
Application Number | 20050051434 10/933353 |
Document ID | / |
Family ID | 34225182 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050051434 |
Kind Code |
A1 |
Mishima, Koji ; et
al. |
March 10, 2005 |
Method and apparatus for controlling electrolytic solution
Abstract
An electrolytic solution control method can control the
composition of an electrolytic solution efficiently with high
precision, and can remove a partially decomposed product of an
organic component from an electrolytic solution. The electrolytic
solution control method includes storing an electrolytic solution
containing an organic component and an inorganic component in an
electrolytic solution storage tank while controlling and keeping
the electrolytic solution at a predetermined composition, adjusting
an inorganic component of the waste electrolytic solution after use
in electrolytic processing in an electrolytic processing apparatus,
and then returning the waste electrolytic solution to the
electrolytic solution storage tank.
Inventors: |
Mishima, Koji; (Tokyo,
JP) ; Hodai, Masao; (Tokyo, JP) ; Kanda,
Hiroyuki; (Tokyo, JP) ; Ide, Kunihito; (Tokyo,
JP) ; Yamamoto, Satoru; (Tokyo, JP) ;
Katsuoka, Seiji; (Tokyo, JP) ; Kinbara, Masaaki;
(Tokyo, JP) ; Akahori, Masaji; (Tokyo, JP)
; Nakagawa, Sota; (Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
34225182 |
Appl. No.: |
10/933353 |
Filed: |
September 3, 2004 |
Current U.S.
Class: |
205/98 ;
204/263 |
Current CPC
Class: |
C25D 21/22 20130101;
C25D 21/12 20130101 |
Class at
Publication: |
205/098 ;
204/263 |
International
Class: |
C25D 021/06; C25C
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2003 |
JP |
2003-314755 |
Claims
What is claimed is:
1. An electrolytic solution control method comprising: storing an
electrolytic solution containing an organic component and an
inorganic component in an electrolytic solution storage tank while
controlling and keeping the electrolytic solution at a
predetermined composition; adjusting an inorganic component of the
waste electrolytic solution after use in electrolytic processing in
an electrolytic processing apparatus; and then returning the waste
electrolytic solution to the electrolytic solution storage
tank.
2. The electrolytic solution control method according to claim 1,
wherein the adjustment of the inorganic component is effected by
electrolytic processing carried out by providing a cathode chamber
and an anode chamber which are separated by an ion exchanger, and
using the waste electrolytic solution as an anode liquid.
3. The electrolytic solution control method according to claim 2,
wherein the ion exchanger is an ion-exchange membrane or
ion-exchange fabric having monovalent cation selectivity.
4. The electrolytic solution control method according to claim 2,
wherein a soluble electrode is used as an anode in the electrolytic
processing of the waste electrolytic solution, and the current
density at the anode is 10 to 100 mA/cm.sup.2.
5. The electrolytic solution control method according to claim 2,
wherein the concentration of metal ions in the waste electrolytic
solution is detected during the electrolytic processing so as to
adjust the amount of electric current in the electrolytic
processing.
6. The electrolytic solution control method according to claim 2,
wherein an inorganic acid is used as a cathode liquid in the
electrolytic processing of the waste electrolytic solution, and the
electric conductivity of the cathode liquid is detected and
adjusted.
7. The electrolytic solution control method according to claim 2,
wherein pure water is used as a cathode liquid in the electrolytic
processing of the waste electrolytic solution, and another ion
exchanger is interposed between the cathode and said ion
exchanger.
8. The electrolytic solution control method according to claim 1,
wherein the electrolytic processing apparatus is a plating
apparatus which uses as an anode an insoluble electrode or an
electrode not containing phosphorus.
9. An electrolytic solution control method comprising: storing an
electrolytic solution containing an organic component and an
inorganic component in an electrolytic solution storage tank while
controlling and keeping the electrolytic solution at a
predetermined composition; removing at least part of the organic
component of the waste electrolytic solution after use in
electrolytic processing in an electrolytic processing apparatus;
and then returning the waste electrolytic solution to the
electrolytic solution storage tank.
10. The electrolytic solution control method according to claim 9,
wherein the organic component is at least one of an organic polymer
compound, a sulfur compound and a nitrogen compound.
11. The electrolytic solution control method according to claim 9,
wherein the removal of the organic component is carried out by
using an adsorbent.
12. The electrolytic solution control method according to claim 9,
wherein the removal of the organic component is carried out
utilizing oxidation and decomposition of the organic component.
13. The electrolytic solution control method according to claim 9,
wherein particles are removed from the waste electrolytic solution
after the removal of the organic component.
14. The electrolytic solution control method according to claim 9,
wherein the electrolytic processing apparatus is a plating
apparatus which uses as an anode an insoluble electrode or an
electrode not containing phosphorus.
15. An electrolytic solution control apparatus comprising: an
electrolytic solution storage tank for storing an electrolytic
solution containing an organic component and an inorganic component
therein while controlling and keeping the electrolytic solution at
a predetermined composition; and an inorganic component adjustment
apparatus for adjusting an inorganic component of the waste
electrolytic solution after use in electrolytic processing in an
electrolytic processing apparatus, and then returning the waste
electrolytic solution to the electrolytic solution storage
tank.
16. The electrolytic solution control apparatus according to claim
15, wherein the inorganic component adjustment apparatus is
designed to supply metal ions to the waste electrolytic solution
utilizing electrolysis.
17. The electrolytic solution control apparatus according to claim
15, further comprising: an inorganic component analyzer for
analyzing the inorganic component of the waste electrolytic
solution introduced into the inorganic component adjustment
apparatus, and feeding back the analytical results to the inorganic
component adjustment apparatus.
18. The electrolytic solution control apparatus according to claim
15, wherein the electrolytic processing apparatus is a plating
apparatus which employs as an anode an insoluble electrode or an
electrode not containing phosphorus.
19. An electrolytic solution control apparatus comprising: an
electrolytic solution storage tank for storing an electrolytic
solution containing an organic component and an inorganic component
therein while controlling and keeping the electrolytic solution at
a predetermined composition; and an organic component removal
apparatus for removing at least part of the organic component of
the waste electrolytic solution after use in electrolytic
processing in an electrolytic processing apparatus, and then
returning the waste electrolytic solution to the electrolytic
solution storage tank.
20. The electrolytic solution control apparatus according to claim
19, wherein the organic component removal apparatus includes an
organic component oxidation/decomposition section for oxidizing and
decomposing the organic component, and an organic component
adsorption/removal section for removing the organic component by
adsorption.
21. The electrolytic solution control apparatus according to claim
19, further comprising: a filter for removing particles, located
downstream of the organic component removal apparatus.
22. The electrolytic solution control apparatus according to claim
19, wherein the electrolytic processing apparatus is a plating
apparatus which employs as an anode an insoluble electrode or an
electrode not containing phosphorus.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method and an apparatus
for controlling electrolytic solution for controlling components of
an electrolytic solution, such as a plating solution for use in the
formation of interconnects by embedding of an interconnect
material, such as copper, by plating into fine interconnect
trenches and holes (via holes) formed in a surface of a substrate,
such as a semiconductor substrate. The present invention is also
applicable to control of an etching solution for etching an
interconnect material by electrolytic etching, a similar
electrolytic technique to plating.
[0003] 2. Description of the Related Art
[0004] In the formation of fine interconnects using electroplating
with copper sulfate for filling-in (embedding) of fine interconnect
trenches and holes formed in the surface of a semiconductor
substrate or the like, a copper sulfate plating solution is widely
used which, in addition to the inorganic base components of copper
sulfate (CuSO.sub.4.5H.sub.2O), sulfuric acid (H.sub.2SO.sub.4),
chlorine (Cl), etc., comprises organic additives, such as an
organic polymer compound as a so-called suppressor, a sulfur
compound as a so-called accelerator, and a nitrogen compound as a
so-called leveler in order to improve the quality of a plated film
and enhance the trench/hole filling (embedding) property.
[0005] The organic components and the inorganic components of such
a plating solution are partly consumed during its use in plating.
Accordingly, in order to recover and reuse the plating solution
(waste plating solution), it is necessary to adjust the components
of the plating solution to a constant composition before reuse of
the plating solution so as to stabilize the plating
performance.
[0006] FIG. 9 schematically shows a conventional plating solution
control system that employs a circulation method. As shown in FIG.
9, the plating solution control system includes a plating solution
storage tank 12 for storing a plating solution 10 while keeping it
at a predetermined composition. The plating solution storage tank
12 is connected to a plating apparatus 14 via a plating solution
supply line 16 and a waste plating solution return line 18, so that
the plating solution is allowed to circulate continuously between
the plating solution storage tank 12 and the plating tank 14.
[0007] To the plating solution storage tank 12 is connected a base
solution supply line 24 extending from a base solution storage tank
22 for storing a base solution 20 comprising a mixture of inorganic
components, such as copper sulfate, sulfuric acid, hydrochloric
acid and water in a predetermined proportion. An organic/inorganic
component supply line 28 extending from an organic/inorganic
component supply apparatus 26 is also connected to the plating
solution storage tank 12. Further, a sampling line 30 for sampling
the plating solution 10 from the plating solution storage tank 12
is connected at one end to the plating solution storage tank 12 and
at the other end to an organic/inorganic component analyzer 32. An
output signal from the organic/inorganic component analyzer 32 is
fed back to the organic/inorganic component supply apparatus
26.
[0008] According to the plating solution control system, the
plating solution 10 comprising a mixture of the base solution 20
with organic components in predetermined amounts is stored in the
plating solution storage tank 12, and the plating solution 10 is
supplied to the plating apparatus 14 to carry out plating. The
organic and inorganic components of the plating solution are partly
consumed during plating, and therefore the plating solution 10 in
the plating solution storage tank 12 gradually runs short of part
of the organic and inorganic components. Accordingly, the plating
solution 10 in the plating solution storage tank 12 is sampled, and
the organic and inorganic components of the plating solution 10 are
analyzed by the organic/inorganic component analyzer 32. Based on
the analytical results, the organic/inorganic component supply
apparatus 26 is actuated to replenish the plating solution 10 with
the shortage of organic/inorganic components so as to keep the
plating solution 10 to be supplied to the plating apparatus 14 at a
constant composition, thereby stabilizing the plating
performance.
[0009] FIG. 10 schematically shows a conventional plating solution
control system that employs a batch circulation method. This system
differs from the system shown in FIG. 9 in that a recovery tank 36
for recovering a waste plating solution through a recovery line 34
connected to a plating apparatus 14, and a waste plating solution
return line 38 connecting the recovery tank 36 and a plating
solution storage tank 12 are provided so that the waste plating
solution is once stored in the recovery tank 36 and the waste
plating solution in the recovery tank 36 is returned intermittently
to the plating solution storage tank 12.
[0010] FIG. 11 shows a conventional plating system which uses a
plating solution in a one-pass manner without return and without
control of the plating solution, that is, the plating solution is
once used and thrown away. According to this system, a
predetermined amount of base solution 20 is supplied from a base
solution storage tank 22 through a base solution supply line 24
into a plating solution storage tank 12, and predetermined amounts
of organic and inorganic components are supplied from an
organic/inorganic component supply apparatus 26 through an
organic/inorganic component supply line 28 into the plating
solution storage tank 12, thereby preparing a plating solution 10
comprising predetermined components. The plating solution 10 in the
plating solution storage tank 12 is supplied through a plating
solution supply line 16 into a plating apparatus 14 to carry out
plating, and the waste plating solution is discharged through a
waste liquid line 40 and is subjected to waste liquid disposal.
[0011] The conventional plating solution control systems rely
largely on organic/inorganic component analyzers that are
complicated and costly, and are not fully satisfactory in analysis
precision. It is, therefore, difficult to control the composition
of a plating solution efficiently with high precision. In addition,
the conventional control systems have the problem that a partially
decomposed product of an organic component can accumulate in a
plating solution.
[0012] Though the one-pass plating system has the advantage of no
need for control of plating solution, such system involves the use
of a larger amount of plating solution, leading to an increased
cost, and also involves an increased amount of waste liquid to be
disposed of.
[0013] While the conventional systems and attendant problems have
been described in terms of a copper sulfate plating solution for
use in plating to effect filling-in (embedding) of fine
interconnect trenches and holes formed in the surface of a
semiconductor substrate or the like, similar problems are involved
in the use of other plating solutions comprising organic and
inorganic components and also in the use of an electrolytic
solution other than a plating solution, for example, an etching
solution for use in etching processing.
SUMMARY OF THE INVENTION
[0014] The present invention has been made in view of the above
situation in the related art. It is therefore an object of the
present invention to provide a method and an apparatus for
controlling an electrolytic solution, which can control the
composition of an electrolytic solution efficiently with high
precision, and can remove a partially decomposed product of an
organic component from an electrolytic solution.
[0015] In order to achieve the above object, the present invention
provides an electrolytic solution control method comprising:
storing an electrolytic solution containing an organic component
and an inorganic component in an electrolytic solution storage tank
while controlling and keeping the electrolytic solution at a
predetermined composition; adjusting an inorganic component of the
waste electrolytic solution after use in electrolytic processing in
an electrolytic processing apparatus; and then returning the waste
electrolytic solution to the electrolytic solution storage
tank.
[0016] With respect to a copper-plating solution, for example, for
use in copper plating in a plating apparatus having an insoluble
anode or an electrolytic copper anode not containing phosphorus,
the metal component (copper ions) of the copper-plating solution
gradually decreases with the progress of plating. In this regard,
an insoluble anode differs from a soluble anode, and cannot
replenish copper ions consumed. In the case of an electrolytic
copper anode, because of a disproportionation reaction caused by
dissolved monovalent copper ions, a sufficient supply of divalent
copper ions is not possible. Accordingly, it is necessary for reuse
of the waste plating solution to replenish the inorganic component,
copper ions. The shortage of copper ions can be inferred precisely
from the integrated amount of electric current in the plating
apparatus. By thus precisely inferring the shortage of copper ions,
replenishing the waste plating solution with the shortage of copper
ions, and returning the waste plating solution to a plating
solution storage tank, it becomes possible to eliminate the use of
an inorganic component analyzer for controlling a proper amount of
copper ions to be replenished, and control copper ions in the
plating solution efficiently with high precision.
[0017] In a preferred embodiment of the present invention, the
adjustment of the inorganic component is effected by electrolytic
processing carried out by providing a cathode chamber and an anode
chamber which are separated by an ion exchanger, and using the
waste electrolytic solution as an anode liquid.
[0018] To a plating liquid, replenishment of inorganic components,
especially a metal component, is important. According to this
embodiment, the replenishment of a metal component is effected by
electrolytic processing utilizing electrolysis (anode dissolution).
Thus, unlike the below-described method of adding metallic
particles, there is no fear of particles or powder remaining in a
plating solution, which particles (powder) are undesirable e.g. for
the production of fine interconnects. Further, a metal component in
a precise amount can be supplied to the waste plating solution. In
the case of a copper-plating solution, for example, it is most
appropriate to use phosphorus-containing copper for the anode. The
phosphorus-containing copper herein refers to electrolytic copper
doped with phosphorus in an amount of about 500 ppm. The use of an
anode made of phosphorus-containing copper has the advantage of not
generating monovalent copper ions that will cause a
disproportionation reaction.
[0019] For replenishment of a metal component, besides the method
that utilizes electrolysis, a method may be considered which
involves dissolving a metal carbonate, a metal hydroxide or fine
particles of a metal. This method, however, lacks reliability of a
means for precisely weighing such metallic power or particles. In
addition, the use of such powder or particles is not suitable for a
plating solution which is employed e.g. for the production of fine
interconnects.
[0020] Preferably, the ion exchanger is an ion-exchange membrane or
ion-exchange fabric having monovalent cation selectivity.
[0021] By thus disposing an ion exchanger having monovalent cation
selectivity, i.e. an ion exchanger, which selectively exchanges
only monovalent cation ions, between a cathode and an anode, metal
ions, such as divalent copper ions, supplied from the anode can be
prevented from moving into the cathode chamber, whereby deposition
of the metal on the cathode can be prevented. An ion-exchange
membrane comprising a dense polymer membrane modified with, for
example, a sulfonic group and also modified in the surface with,
for example, quaternary ammonium, may be exemplified as an
effective ion exchanger. The ion exchanger according to the present
invention is, of course, not limited to such a polymer
membrane.
[0022] When the present method is applied to replenishment of
copper ions for a copper-plating solution, most cations movable to
the cathode are hydrogen ions. Hydrogen ions, which have moved to
the cathode, are converted into hydrogen gas at the cathode
surface.
[0023] Preferably, a soluble electrode is used as an anode in the
electrolytic processing of the waste electrolytic solution, and the
current density at the anode is 10 to 100 mA/cm.sup.2.
[0024] In the case of dissolving an anode, the current density at
the anode is preferably set at a somewhat high value from the
viewpoint of preventing the generation of e.g. monovalent copper
ions. If the current density at the anode is made higher than 100
mA/cm.sup.2, however, the anode dissolution efficiency can decrease
due to generation of oxygen. The use of such a high current density
is thus disadvantageous in the light of energy consumption.
Accordingly, the current density at the anode is preferably within
the range of 10-100 mA/cm.sup.2.
[0025] Preferably, the concentration of metal ions in the waste
electrolytic solution is detected during the electrolytic
processing so as to adjust the amount of electric current in the
electrolytic processing.
[0026] The amount of metal ions to be supplied to the waste
electrolytic solution by electrolytic processing can be controlled
by adjusting the amount of electric current in the electrolytic
processing.
[0027] In a preferred embodiment of the present invention, an
inorganic acid is used as a cathode liquid in the electrolytic
processing of the waste electrolytic solution, and the electric
conductivity of the cathode liquid is detected and adjusted.
[0028] Dilute sulfuric acid is most inexpensive and practical for
use as a cathode liquid. The electrolytic reaction can be
stabilized by detecting and adjusting the electric conductivity of
the cathode liquid used (dilute sulfuric acid).
[0029] In a preferred embodiment of the present invention, pure
water is used as a cathode liquid in the electrolytic processing of
the waste electrolytic solution, and another ion exchanger is
interposed between the cathode and said ion exchanger.
[0030] By interposing another ion exchanger composed of, for
example, ion-exchange fibers between the cathode and the ion
exchanger, it becomes possible to carry out electrolytic processing
at a low voltage even when pure water having a low electric
conductivity is used. Thus, a chemical such as a mineral acid may
not be employed for a cathode liquid. In that case, replenishment
of other inorganic components than a metal component may be
effected by preparing concentrated solutions of, for example,
sulfuric acid and hydrochloric acid, and supplying the solutions in
such amounts as to replenish the shortage of the inorganic
components.
[0031] The present invention also provides another electrolytic
solution control method comprising: storing an electrolytic
solution containing an organic component and an inorganic component
in an electrolytic solution storage tank while controlling and
keeping the electrolytic solution at a predetermined composition;
removing at least part of the organic component of the waste
electrolytic solution after use in electrolytic processing in an
electrolytic processing apparatus; and then returning the waste
electrolytic solution to the electrolytic solution storage
tank.
[0032] In the case of removing part of the organic component, the
main target for removal is a partially decomposed product of the
organic component. The removal of such a partially decomposed
product can avoid accumulation of the product in, for example, a
plating solution which would adversely affect plating processing. A
partially decomposed product generally has a low molecular weight.
It is therefore effective to use an adsorbent having high
low-molecular weight compound removal capability. The residual
organic component remaining in the waste electrolytic solution can
be employed as an effective additive component for e.g. a plating
solution.
[0033] In the case of removing the whole organic component, the
waste electrolytic solution becomes a so-called base solution with
no organic component. Accordingly, when re-adding the organic
component to e.g. a plating solution, the amount of the organic
component to be added can be determined theoretically. Thus, a
predetermined amount of organic component can be added to e.g. the
plating solution by weight control or volume control without
analysis of the organic component of the plating solution with an
organic component analyzer. This enables very accurate addition of
organic component.
[0034] The organic component may be at least one of an organic
polymer compound, a sulfur compound and a nitrogen compound.
[0035] In the case of a copper sulfate plating solution for use,
for example, in the production of fine interconnects by plating,
the organic component to be removed includes an organic polymer
compound as a suppressor, a sulfur compound as an accelerator, and
a nitrogen compound as a leveler, and their decomposition
products.
[0036] The removal of the organic component may be carried out by
using an adsorbent.
[0037] The adsorbent may be exemplified by activated carbon.
Another inorganic adsorbent, such as a zeolite, or an organic
adsorbent may also be used.
[0038] In a preferred embodiment of the present invention, the
removal of the organic component is carried out utilizing oxidation
and decomposition of the organic component.
[0039] The organic component may be oxidized and decomposed, for
example, by adding an oxidizing agent to the waste electrolytic
solution or by an electrolytic method. The major part of the
organic component can be decomposed into carbon dioxide and water,
and the residual organic component can be removed by adsorption.
This manner of removing the organic component, as compared to
removal of the whole organic component by adsorption, has the
advantage of decreasing the amount of a waste adsorbent containing
the organic component as industrial waste.
[0040] Preferably, particles are removed from the waste
electrolytic solution after the removal of the organic
component.
[0041] Particles, such as those coming from the adsorbent used, are
removed so as to prevent the particles from being mixed into e.g. a
plating solution.
[0042] In a preferred embodiment of the present invention, the
electrolytic processing apparatus is a plating apparatus which uses
as an anode an insoluble electrode or an electrode not containing
phosphorus.
[0043] The present invention further provides an electrolytic
solution control apparatus comprising: an electrolytic solution
storage tank for storing an electrolytic solution containing an
organic component and an inorganic component therein while
controlling and keeping the electrolytic solution at a
predetermined composition; and an inorganic component adjustment
apparatus for adjusting an inorganic component of the waste
electrolytic solution after use in electrolytic processing in an
electrolytic processing apparatus, and then returning the waste
electrolytic solution to the electrolytic solution storage
tank.
[0044] Preferably, the inorganic component adjustment apparatus is
designed to supply metal ions to the waste electrolytic solution
utilizing electrolysis.
[0045] The electrolytic solution control apparatus may further
comprise an inorganic component analyzer for analyzing the
inorganic component of the waste electrolytic solution introduced
into the inorganic component adjustment apparatus, and feeding back
the analytical results to the inorganic component adjustment
apparatus.
[0046] The present invention also provides an electrolytic solution
control apparatus comprising: an electrolytic solution storage tank
for storing an electrolytic solution containing an organic
component and an inorganic component therein while controlling and
keeping the electrolytic solution at a predetermined composition;
and an organic component removal apparatus for removing at least
part of the organic component of the waste electrolytic solution
after use in electrolytic processing in an electrolytic processing
apparatus, and then returning the waste electrolytic solution to
the electrolytic solution storage tank.
[0047] In a preferred embodiment of the present invention, the
organic component removal apparatus includes an organic component
oxidation/decomposition section for oxidizing and decomposing the
organic component, and an organic component adsorption/removal
section for removing the organic component by adsorption.
[0048] Preferably, the electrolytic solution control apparatus
further comprises a filter for removing particles, located
downstream of the organic component removal apparatus.
[0049] In a preferred embodiment of the present invention, the
electrolytic processing apparatus is a plating apparatus which
employs as an anode an insoluble electrode or an electrode not
containing phosphorus.
[0050] According to the method and apparatus of the present
invention, the composition of an electrolytic solution, such as a
plating solution, can be controlled efficiently with high
precision. This makes it possible to perform electrolytic
processing with increased productivity and reduced cost. Further,
through regeneration and reuse of a waste electrolytic solution,
such as a waste plating solution, the amount of the electrolytic
solution used can be decreased and also the amount of the waste
liquid can be decreased, whereby the environmental burden of waste
liquid can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a schematic diagram showing a plating solution
control system incorporating a plating solution (electrolytic
solution) control apparatus according to a first embodiment of the
present invention;
[0052] FIG. 2 is a schematic diagram showing an inorganic component
adjustment apparatus provided in the plating solution control
system shown in FIG. 1;
[0053] FIG. 3 is a schematic diagram showing another inorganic
component adjustment apparatus;
[0054] FIG. 4 is a schematic diagram showing a plating solution
control system incorporating a plating solution (electrolytic
solution) control apparatus according to a second embodiment of the
present invention;
[0055] FIG. 5 is a schematic diagram showing an organic component
removal apparatus provided in the plating solution control system
shown in FIG. 4;
[0056] FIG. 6 is a schematic diagram showing another organic
component removal apparatus;
[0057] FIG. 7 is a schematic diagram showing yet another organic
component removal apparatus;
[0058] FIG. 8 is a schematic diagram showing a plating solution
control system incorporating a plating solution (electrolytic
solution) control apparatus according to a third embodiment of the
present invention;
[0059] FIG. 9 is a schematic diagram showing a conventional plating
solution control system that employs a circulation method;
[0060] FIG. 10 is a schematic diagram showing a conventional
plating solution control system that employs a batch circulation
method; and
[0061] FIG. 11 is a schematic diagram showing a conventional
plating system which uses a plating solution in a one-pass
manner.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] Preferred embodiments of the present invention will now be
described with reference to the drawings. The following embodiments
use as an electrolytic solution a copper sulfate plating solution
comprising a base solution, which is a mixture of inorganic
components such as copper sulfate, sulfuric acid, hydrochloric acid
and water in a predetermined proportion, and organic additives such
as an organic polymer compound as a suppressor, a sulfur compound
as an accelerator and a nitrogen compound as a leveler. Further,
the following embodiments use as an electrolytic processing
apparatus a plating apparatus having an insoluble anode or an
electrolytic copper anode not containing phosphorus. In the
following description, the same or equivalent members as or to
those shown in FIGS. 9 through 11 are given the same reference
numerals, and a duplicate description thereof is omitted.
[0063] FIG. 1 schematically shows a plating solution control system
incorporating a plating solution (electrolytic solution) control
apparatus according to a first embodiment of the present invention.
As shown in FIG. 1, the plating solution control system includes an
inorganic component adjustment apparatus 50 for adjusting an
inorganic component of a waste plating solution after use in
plating in a plating apparatus 14. The plating apparatus 14 is
connected to the inorganic component adjustment apparatus 50 via a
waste plating solution supply line 52, and the inorganic component
adjustment apparatus 50 is connected to a plating solution storage
tank 12 via a waste plating solution return line 54.
[0064] A plating solution 10 stored in the plating solution storage
tank 12 is supplied through a plating solution supply line 16 to
the plating apparatus 14, and the waste plating solution after use
in the plating apparatus 14 is supplied through the waste plating
solution supply line 52 to the inorganic component adjustment
apparatus 50. The inorganic component-adjusted plating solution
(waste plating solution) after adjustment of the inorganic
component in the inorganic component adjustment apparatus 50 is
returned through the waste plating solution return line 54 to the
plating solution storage tank 12. The plating solution is
circulated in this manner.
[0065] The system also includes an inorganic component analyzer 58
for sampling the waste plating solution, which has been supplied
into the inorganic component adjustment apparatus 50, through a
sampling line 56 and analyzing the inorganic component of the waste
plating solution. The analytical results are fed back to the
inorganic component adjustment apparatus 50.
[0066] The inorganic component adjustment apparatus 50 according to
this embodiment is designed to replenish and adjust divalent copper
ions as an inorganic component of the waste plating solution. When
copper plating is carried out by the plating apparatus 14 having an
insoluble anode or an electrolytic copper anode not containing
phosphorus, the metal component (divalent copper ions) of the
plating solution gradually decreases with the progress of plating.
In this regard, an insoluble anode differs from a soluble anode,
and cannot replenish copper ions consumed. In the case of an
electrolytic copper anode, because of a disproportionation reaction
caused by dissolved monovalent copper ions, a sufficient supply of
divalent copper ions is not possible. Accordingly, it is necessary
for reuse of the waste plating solution to replenish the inorganic
component, divalent copper ions.
[0067] With respect to the other inorganic and organic components,
as with the above-described conventional system, the plating
solution 10 in the plating solution storage tank 12 is sampled, and
the organic and inorganic components of the plating solution 10 are
analyzed by an organic/inorganic component analyzer 32. Based on
the analytical results, an organic/inorganic component supply
apparatus 26 is actuated to replenish the plating solution 10 with
the shortage of the organic components and/or inorganic
components.
[0068] The shortage of divalent copper ions can be inferred
precisely from the integrated amount of electric current in the
plating apparatus 14. Thus, according to this embodiment, the
shortage of divalent copper ions is inferred precisely from the
integrated amount of electric current in the plating apparatus 14,
the shortage of divalent copper ions is supplied to the waste
plating solution by the inorganic component adjustment apparatus
50, and the waste plating solution is then returned to the plating
solution storage tank 12. This makes it possible to eliminate the
use of a divalent copper ion analyzer for detecting a proper amount
of divalent copper ions to be replenished, and control divalent
copper ions in the plating solution efficiently with high
precision.
[0069] As described above, the inorganic component adjustment
apparatus 50 is to replenish and adjust divalent copper ions in the
waste plating solution. According to this embodiment, the
replenishment of divalent copper ions is effected by electrolytic
processing utilizing electrolysis (anode dissolution) with the
waste plating solution as an anode liquid. According to this
method, unlike the method of adding metallic particles, there is no
fear of particles or powder remaining in a plating solution, which
particles (powder) are undesirable e.g. for the production of fine
interconnects. Further, divalent copper ions in a precise amount
can be supplied to the waste plating solution.
[0070] In particular, as shown in FIG. 2, the inorganic component
adjustment apparatus 50 includes an electrolytic cell 60. At the
both ends of the electrolytic cell 60 are disposed an anode plate
64 to be connected to the anode of a direct-current power source
62, and a cathode plate 66 to be connected to the cathode of the
direct-current power source 62. The interior of the electrolytic
cell 60 is separated by an ion exchanger 68, which is an
ion-exchanger membrane, into an anode chamber 70 in which the anode
plate 64 is located and a cathode chamber 72 in which the cathode
plate 66 is located.
[0071] The waste plating solution is supplied through the waste
plating solution supply line 52 into the anode chamber 70, passed
through the anode chamber 70, and is discharged through the waste
plating solution return line 54. During the passage of the waste
plating solution through the anode chamber 70, divalent copper ions
as an inorganic component are supplied to the waste plating
solution. On the other hand, a cathode liquid 75, for example,
dilute sulfuric acid which is most inexpensive and practical for
use as a cathode liquid, stored in a cathode liquid storage tank
74, is circulated between the cathode chamber 72 and the cathode
liquid storage tank 74. The electrolytic reaction can be stabilized
by detecting and adjusting the electric conductivity of the cathode
liquid (dilute sulfuric acid) 75.
[0072] The anode plate 64 is made of phosphorus-containing copper
which is electrolytic copper doped with phosphorus in an amount of
about 500 ppm. The use of such phosphorus-containing copper for the
anode plate 64 has the advantage of not generating monovalent
copper ions, which will cause a disproportionation reaction, when
the phosphorus-containing copper dissolves.
[0073] An ion-exchange membrane having monovalent cation
selectivity is used as the ion exchanger 68. In particular, the ion
exchanger 68 is an ion-exchange membrane comprising a dense polymer
membrane modified with, for example, a sulfonic group and also
modified in the surface with, for example, quaternary ammonium. The
ion exchanger 64 is, of course, not limited to such a polymer
membrane.
[0074] By thus disposing the ion exchanger 68 having monovalent
cation selectivity, which selectively exchanges only monovalent
cation ions, between the anode plate 64 and the cathode plate 66,
divalent copper ions (Cu.sup.2+), supplied from the anode plate 64,
can be prevented from moving into the cathode chamber 72, whereby
deposition of copper on the cathode plate 66 can be prevented.
Hydrogen ions (H.sup.+) in the anode chamber 70 move through the
ion exchanger 68 into the cathode chamber 72, thus passing
electricity. The hydrogen ions, which have moved into the cathode
chamber 72, are converted into hydrogen gas at the surface of the
cathode plate 66 and the hydrogen gas is discharged out of the
electrolytic cell 60. On the other hand, divalent sulfate ions
(SO.sub.4.sup.2-) in the cathode chamber 72 are shut off by the ion
exchanger 68, not moving into the anode chamber 70. Accordingly,
the sulfate ion concentration of the waste plating solution in the
anode chamber 70 does not change.
[0075] According to this embodiment, while introducing the waste
plating solution into the anode chamber 70 and introducing the
cathode liquid of dilute sulfuric acid into the cathode chamber 72,
a voltage is applied from the direct-current power source 62 to
between the anode plate 64 and the cathode plate 66, thereby
dissolving the anode plate 64 and supplying divalent copper ions to
the waste plating solution introduced into the anode chamber 70.
The current density at the anode plate 64 is preferably set at a
somewhat high value from the viewpoint of preventing the generation
of monovalent copper ions. If the current density at the anode
plate 64 is made higher than 100 mA/cm.sup.2, however, the anode
plate dissolution efficiency can decrease due to generation of
oxygen. The use of such a high current density is thus
disadvantageous in the light of energy consumption. Accordingly,
the current density at the anode plate 64 is preferably within the
range of 10-100 mA/cm.sup.2.
[0076] According to this embodiment, a copper ion concentration
detector for detecting the divalent copper ion concentration of the
waste plating solution in the anode chamber 70 is used as the
inorganic component analyzer 58. The divalent copper ion
concentration of the waste plating solution in the anode chamber 70
is detected with the inorganic component analyzer (copper ion
concentration detector) 58, and based on the analytical results,
the amount of the electric current flowing between the anode plate
64 and the cathode plate 66 is adjusted so as to control the amount
of divalent copper ions to be supplied to the waste plating
solution by the electrolytic processing.
[0077] FIG. 3 shows another inorganic component adjustment
apparatus 50. This apparatus differs from the apparatus shown in
FIG. 2 in that pure water is employed as a cathode liquid flowing
in the cathode chamber 72, and that another ion exchanger 76
composed of, for example, ion-exchange fibers is interposed between
the cathode plate 66 and the ion exchanger 68. The other
construction is the same as the apparatus shown in FIG. 2.
[0078] According to this apparatus 50, it is possible to carry out
electrolytic processing at a low voltage even when pure water
having a low electric conductivity is used. Thus, a chemical such
as a mineral acid may not be employed as the cathode liquid. In
that case, replenishment of other inorganic components than a metal
component may be effected by preparing concentrated solutions of,
for example, sulfuric acid and hydrochloric acid, and supplying the
solutions in such amounts as to replenish the shortage of the
inorganic components.
[0079] FIG. 4 schematically shows a plating solution control system
incorporating a plating solution (electrolytic solution) control
apparatus according to a second embodiment of the present
invention. According to this embodiment, an organic component
removal apparatus 80 for removing at least part of the organic
component of the waste plating solution is interposed in the waste
plating solution return line 54, connecting the inorganic component
adjustment apparatus 50 and the plating solution storage tank 12,
of the preceding embodiment shown in FIG. 1. Thus, the inorganic
component-adjusted plating solution (waste plating solution), whose
inorganic component (divalent copper ions) has been adjusted in the
inorganic component adjustment apparatus 50, is introduced into the
inorganic component removal apparatus 80, where at least part of
the organic component of the waste plating solution is removed, and
then the waste plating solution is returned to the plating solution
storage tank 12.
[0080] According to this embodiment, the organic component to be
removed with the organic component removal apparatus 80 includes an
organic polymer compound as a suppressor, a sulfur compound as an
accelerator, and a nitrogen compound as a leveler, and their
decomposition products.
[0081] In the case of removing part of the organic component with
this organic component removal apparatus 80, the main target for
removal is a partially decomposed product of the organic component.
The removal of such a partially decomposed product can avoid
accumulation of the product in the plating solution, which would
adversely affect plating processing. A partially decomposed product
generally has a low molecular weight. It is therefore effective to
use as the below-described adsorbent 82 an adsorbent having high
low-molecular weight compound removal capability. The residual
organic component remaining in the waste plating solution can be
employed as an effective additive component for the plating
solution.
[0082] In the case of removing the whole organic component, on the
other hand, the waste plating solution becomes a so-called base
solution with no organic component. Accordingly, when re-adding the
organic component to the plating solution, the amount of the
organic component to be added can be determined theoretically.
Thus, a predetermined amount of organic component can be added to
the plating solution by weight control or volume control without
analysis of the organic component of the plating solution with an
organic component analyzer. This enables very accurate addition of
organic component.
[0083] FIG. 5 schematically shows the organic component removal
apparatus 80. The organic component removal apparatus 80 includes
an organic component adsorption/removal section 86 comprising a
container 84 packed with an adsorbent 82 such as activated carbon.
According to the organic component removal apparatus 80, at least
part of the organic component of the inorganic component-adjusted
plating solution (waste plating solution), which has been
replenished with divalent copper ions as an inorganic component in
the inorganic component adjustment apparatus 50, is adsorbed onto
the adsorbent 82 and thus removed from the waste plating solution,
and the waste plating solution after the removal of organic
component is returned to the plating solution storage tank 12.
[0084] Besides activated carbon, another inorganic adsorbent, such
as a zeolite, or an organic adsorbent may also be used as the
adsorbent 82.
[0085] According to this embodiment, a filter 88 for removing
particles from the waste plating solution after the removal of
organic component is provided downstream of the organic component
adsorption/removal section 86. Particles, such as those coming from
the adsorbent 82 such as activated carbon, can be removed by the
filter 88, thus preventing the particles from being mixed into the
plating solution.
[0086] FIG. 6 schematically shows another organic component removal
apparatus 80. This organic component removal apparatus 80
additionally includes an organic component oxidation/decomposition
section 94, comprising an oxidizing agent tank 92 for storing an
oxidizing agent 90, located upstream of the above-described organic
component adsorption/removal section 86 shown in FIG. 5. According
to this removal apparatus 80, the waste plating solution, whose
inorganic component (divalent copper ions) has been adjusted in the
inorganic component adjustment apparatus 50, is first introduced
into the oxidizing agent tank 92 and passed through the oxidizing
agent in the oxidizing agent tank 92 to thereby oxidize and
decompose the organic component of the waste plating solution. The
major part of the organic component is thus decomposed into carbon
dioxide and water. Thereafter, the residual organic component
remaining in the waste plating solution is removed by adsorption in
the organic component adsorption/removal section 86.
[0087] This manner of removing the organic component, as compared
to the removal of the whole organic component by adsorption, has
the advantage of decreasing the amount of a waste adsorbent
containing the organic component as industrial waste.
[0088] FIG. 7 schematically shows another organic component removal
apparatus 80. According to this organic component removal apparatus
80, the organic component oxidation/decomposition section 94 is
comprised of an electrolytic apparatus 96 for electrolytically
oxidizing and decomposing the organic component of the waste
plating solution. The other construction is the same as the
apparatus shown in FIG. 6. As with the above removal apparatus, the
major part of the organic component is decomposed into carbon
dioxide and water, and only the residual organic component is
removed by adsorption.
[0089] FIG. 8 schematically shows a plating solution control system
incorporating a plating solution (electrolytic solution) control
apparatus according to a third embodiment of the present invention.
This embodiment differs from the embodiment shown in FIG. 4 in that
instead of providing the organic component removal apparatus 80 in
the waste plating solution return line 54 connecting the inorganic
component adjustment apparatus 50 and the plating solution storage
tank 12, the organic component removal apparatus 80 is provided in
the waste plating solution supply line 52 connecting the plating
apparatus 14 and the inorganic component adjustment apparatus 50.
Thus, at least part of the organic component of the waste plating
solution is first removed by the organic component removal
apparatus 80, and then the inorganic component (divalent copper
ions) of the waste plating solution is adjusted by the inorganic
component adjustment apparatus 50, and the waste plating solution
is then returned to the plating solution storage tank 12.
[0090] The inorganic component adjustment apparatus 50 and the
organic component removal apparatus 80 may thus be arranged in a
desired order.
[0091] Although the present invention has been described in the
context of control of a copper sulfate plating solution for use in
plating to effect filling-in (embedding) of fine interconnect
trenches and holes formed in the surface of e.g. a semiconductor
substrate, the invention is also applicable to control of other
plating solutions comprising organic and inorganic components, and
an electrolytic solution other than a plating solution, for
example, an etching solution for use in etching processing.
[0092] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
* * * * *