U.S. patent application number 10/784191 was filed with the patent office on 2004-08-26 for method of supplying solution for electrochemical processes from double-cavity electrode housing.
This patent application is currently assigned to NuTool Inc.. Invention is credited to Basol, Bulent M., Talieh, Homayoun, Uzoh, Cyprian E..
Application Number | 20040163963 10/784191 |
Document ID | / |
Family ID | 25294798 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040163963 |
Kind Code |
A1 |
Uzoh, Cyprian E. ; et
al. |
August 26, 2004 |
Method of supplying solution for electrochemical processes from
double-cavity electrode housing
Abstract
An anode assembly by which a solution can be supplied to a
surface of a semiconductor substrate includes a housing defining an
internal housing volume into which the solution can flow. A closure
is provided for the internal housing volume, and the solution can
be discharged from the internal housing volume through the closure
towards the surface of the semiconductor substrate. A filter
divides the internal housing volume into a first chamber and a
second chamber located between the first chamber and the closure.
During supply of the solution to the surface, a flow of the
solution into the second chamber occurs at a higher rate than a
flow of the solution into the first chamber, and the flows are
blended in the second chamber.
Inventors: |
Uzoh, Cyprian E.; (Milpitas,
CA) ; Talieh, Homayoun; (San Jose, CA) ;
Basol, Bulent M.; (Manhattan Beach, CA) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
NuTool Inc.
|
Family ID: |
25294798 |
Appl. No.: |
10/784191 |
Filed: |
February 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10784191 |
Feb 24, 2004 |
|
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09845262 |
May 1, 2001 |
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6695962 |
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Current U.S.
Class: |
205/98 ; 205/133;
257/E21.175; 257/E21.303; 257/E21.309 |
Current CPC
Class: |
H01L 21/32115 20130101;
C25D 17/001 20130101; C25D 7/12 20130101; H01L 21/32134 20130101;
C25D 5/08 20130101; H01L 21/2885 20130101; C25F 7/00 20130101 |
Class at
Publication: |
205/098 ;
205/133 |
International
Class: |
C25D 005/08 |
Claims
We claim:
1. An anode assembly by which a solution can be supplied to a
surface of a substrate comprising: a housing defining an internal
housing volume into which the solution can flow, a closure for said
internal housing volume through which the solution can be
discharged from said internal housing volume towards the surface of
said substrate, and a filter by which said internal housing volume
can be divided into a first chamber and a second chamber
located-between the first chamber and the closure, wherein, during
supply of said solution to said surface, a flow of the solution
into said second chamber occurs at a higher rate than a flow of the
solution into said first chamber, and said flows are blended in
said second chamber.
2. The anode assembly of claim 1, wherein said housing includes at
least one primary flow channel through which the solution can pass
directly into said second chamber and at least one secondary flow
channel through which the solution can pass directly into said
first chamber.
3. The anode assembly of claim 2, wherein said primary and
secondary flow channels are independent of each other.
4. The anode assembly of claim 2, wherein said secondary flow
channel taps into said primary flow channel.
5. The anode assembly of claim 4, wherein said secondary flow
channel is adapted to divert a portion of the solution which flows
through said primary flow channel to said first chamber.
6. The anode assembly of claim 1, wherein said closure is a plate
which can cover said internal housing volume.
7. The anode assembly of claim 6, and further comprising a pad
through which said solution can flow overlying said plate.
8. The anode assembly of claim 1, and further comprising a second
filter which can be provided between said second chamber and said
closure.
9. The anode assembly of claim 1, wherein said substrate comprises
a semiconductor.
10. The anode assembly of claim 1, and further comprising a drain
by which sludge can be removed from said first chamber.
11. The anode assembly of claim 1, and further comprising an
external filter which can pre-filter the solution before it enters
the housing.
12. The anode assembly of claim 11, wherein said housing is an
upper housing, and further comprising a lower housing, to which
said external filter can be mounted, adapted to receive at least
part of said upper housing in a volume defined thereby.
13. The anode assembly of claim 12, wherein a fluid inlet chamber
is defined between said lower housing and said upper housing when
the lower housing receives said at least part of said upper
housing.
14. The anode assembly of claim 1, and further comprising an anode
which can be received within said first chamber.
15. The anode assembly of claim 14, wherein said anode is a soluble
anode.
16. The anode assembly of claim 1, wherein said solution is an
electrolyte solution out of which a conductive film can be
deposited onto said surface of the substrate.
17. The anode assembly of claim 1, wherein at least one orifice is
used to remove air bubbles in the first chamber.
18. The anode assembly of claim 1, wherein at least one orifice is
used to remove air bubbles in the second chamber.
19. The anode assembly of claim 1, wherein at least one orifice in
the first chamber and at least one orifice in the second chamber
are used to de-bubble the solution or prevent air bubble
accumulation in the anode assembly.
20. The anode assembly of claim 19, wherein the air bubble
accumulation is reduced by way of a controlled leak between
flanges.
21. A process of supplying a solution to a surface of a substrate
received in an anode assembly comprising: providing a housing
having an internal volume divided by a filter into a first chamber
and a second chamber located between the first chamber and said
surface, supplying the solution to said housing, dividing the
solution supplied to the housing into one flow passing directly
into said second chamber and another flow passing into said second
chamber through said first chamber, blending the flows together in
said second chamber, and discharging said solution from said
housing towards said surface.
22. The process of claim 21, wherein said solution is an
electrolyte solution out of which a conductive film can be
deposited onto said surface of the substrate.
23. The process of claim 21, wherein an anode is received within
said first chamber.
24. The process of claim 23, wherein said anode is a soluble
anode.
25. The process of claim 21, wherein at least one orifice is used
to remove air bubbles in the first chamber.
26. The process of claim 21, wherein at least one orifice is used
to remove air bubbles in the second chamber.
27. The process of claim 21, wherein at least one orifice in the
first chamber and at least one orifice in the second chamber are
used to debubble the solution or prevent air bubble accumulation in
the anode assembly.
28. The process of claim 27, wherein the air bubble accumulation is
reduced by way of a controlled leak between flanges.
29. The process of claim 21, wherein said substrate includes a
semiconductor.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to an apparatus and a method to
deposit, polish, or electro-polish metal films on a substrate, or
to remove such metal films from such a substrate. The unique anode
assembly is particularly suitable for providing planar metal
deposits on damascene-type interconnect and packaging
structures.
[0002] Multi-level integrated circuit manufacturing requires many
steps of metal and insulator film depositions followed by
photoresist patterning and etching or other means of material
removal. After photolithography and etching, the resulting wafer or
substrate surface is non-planar and contains many features such as
vias, lines or channels. Often, these features need to be filled
with a specific material, such as a metal, a dielectric, or both.
For high performance applications, the wafer topographic surface
needs to be planarized, making it ready again for the next level of
processing, which commonly involves deposition of a material, and a
photolithographic step. It is most preferred that the substrate
surface be flat before the photolithographic step so that proper
focusing and level-to-level registration or alignment can be
achieved. Therefore, after each deposition step that yields a
non-planar surface on the wafer, there is often a step of surface
planarization.
[0003] Electrodeposition is a widely accepted technique used in IC
manufacturing for the deposition of a highly conductive material
such as copper (Cu) into the features such as vias and channels
opened in an insulating layer on the semiconductor wafer
surface.
[0004] Electrodeposition is commonly carried out cathodically in a
specially formulated electrolyte solution containing copper ions as
well as additives that control the texture, morphology and plating
behavior of the copper layer. A proper,electrical contact is made
to the seed layer on the wafer surface, typically along the
circumference of the round wafer. A consumable Cu or inert anode
plate is placed in the electrolyte solution. Deposition of Cu on
the wafer surface can then be initiated when a cathodic potential
is applied to the wafer surface with respect to an anode, i.e.,
when a negative voltage is applied to the wafer surface with
respect to an anode plate.
[0005] The importance of overcoming the various deficiencies of the
conventional electrodeposition techniques is evidenced by
technological developments directed to the deposition of planar
copper layers. For example, U.S. Pat. No. 6,176,992 to Talieh,
entitled METHOD AND APPARATUS FOR ELECTROCHEMICAL MECHANICAL
DEPOSITION, commonly owned by the assignee of the present
invention, describes in one aspect an electro chemical mechanical
deposition technique (ECMD) that achieves deposition of the
conductive material into the cavities on the substrate surface
while minimizing deposition on the field regions by polishing the
field regions with a pad as the conductive material is deposited,
thus yielding planar copper deposits.
[0006] U.S. application Ser. No. 09/740,701 entitled PLATING METHOD
AND APPARATUS THAT CREATES A DIFFERENTIAL BETWEEN ADDITIVE DISPOSED
ON A TOP SURFACE AND A CAVITY SURFACE OF A WORKPIECE USING AN
EXTERNAL INFLUENCE; also assigned to the same assignee as the
present invention, describes in one aspect a method and apparatus
for plating a conductive material onto the substrate by creating an
external influence, such as causing relative movement between a
workpiece and a mask, to cause a differential in additives to exist
for a period of time between a top surface and a cavity surface of
a workpiece. While the differential is maintained, power is applied
between an anode and the substrate to cause greater relative
plating of the cavity surface than the top surface.
[0007] U.S. application Ser. No. 09/735,546 entitled METHOD AND
APPARATUS FOR MAKING ELECTRICAL CONTACT TO WAFER SURFACE FOR
FULL-FACE ELECTROPLATING OR ELECTROPOLISHING, filed on Dec. 14,
2000, describes in one aspect a technique for providing full face
electroplating or electropolishing. U.S. application Ser. No.
09/760,757, entitled METHOD AND APPARATUS FOR ELECTRODEPOSITION OF
UNIFORM FILM WITH MINIMAL EDGE EXCLUSION ON SUBSTRATE, filed on
Jan. 17, 2001, describes in one aspect a technique for forming a
flat conductive layer on a semiconductor wafer surface without
losing space on the surface for electrical contacts.
[0008] In such above-mentioned processes, a pad or a mask can be
used during at least a portion of the electrodeposition process
when there is physical contact between the workpiece surface and
the pad or the mask. The physical contact or the external influence
affects the growth of the metal by reducing the growth rate on the
top surface while effectively increasing the growth rate within the
features.
[0009] In a metal deposition process using a soluble anode, it is
necessary to minimize contamination of the deposited metal with
anode sludge or anode fines. Typically, an anode bag is wrapped
around the soluble anode to minimize this sort of contamination. In
a conventional manner of copper electrodeposition for interconnect
or packaging applications, as shown in FIG. 1, an anode bag or
filter 150 is wrapped around an anode 152. A suitable space
separates the anode 152 from the cathode 154 in the deposition cell
156. Agitation, recirculation or even filtration of the electrolyte
solution 160 may be provided. During routine plating operations,
anode sludge builds up in the anode sludge cavity 158 formed by the
space between the anode 152 and the bag 150. In the case of Cu
plating, excessive anode sludge build-up affects the quality of the
deposited metal on the cathode 154 in an adverse manner. In
particular, the uniformity of the deposited metal becomes poorer
because of changes in the electric field distribution. In addition,
the plating voltage increases because of anode polarization. The
copper ions are unable to diffuse fast enough through the sludge
layer to meet the requirements of the cathode. Moreover, the
resulting loss in plating efficiency may cause hydrogen to be
plated or evolve at the cathode. For routine maintenance, the anode
152 is removed from the deposition cell 156 and cleaned or
desludged before replacement.
[0010] A general depiction of a plating and planarization apparatus
in which improved anode assemblies such as those of the present
invention can be used is shown in FIG. 2. The carrier head 10 holds
a round semiconductor wafer 16 and, at the same time, provides an
electrical lead 7 connected to the conductive lower surface of the
wafer. The head can be rotated about a first axis 10b. The head can
also be moved in the x and y directions represented in FIG. 2. An
arrangement which provides movement in the z direction may also be
provided for the head.
[0011] Certain embodiments of a carrier head that may be used to
hold the wafer 16 form the subject matter of co-pending U.S. patent
application Ser. No. 09/472,523, titled WORK PIECE CARRIER HEAD FOR
PLATING AND POLISHING, filed Dec. 27, 1999, the disclosure of which
is incorporated herein by reference as non-essential subject
matter. Certain embodiments of anode assemblies with anode bags
which are useable in conjunction with such a carrier head form the
subject matter of co-pending U.S. patent application Ser. No.
09/568,584, filed May 11, 2000, titled ANODE ASSEMBLY FOR PLATING
AND PLANARIZING A CONDUCTIVE LAYER, the disclosure of which is also
incorporated herein by reference as non-essential subject
matter.
[0012] A pad 8 is provided on top of a round anode assembly 9
across from the wafer surface. The pad 8 may have designs or
structures such as those forming the subject matter of co-pending
U.S. patent application Ser. No. 09/511,278, titled PAD DESIGNS AND
STRUCTURES FOR A VERSATILE MATERIALS PROCESSING APPARATUS, filed
Feb. 23, 2000. The disclosure of this co-pending application is
also incorporated by reference herein as non-essential subject
matter, Co-pending U.S. patent application Ser. No. 09/621,969,
titled PAD DESIGNS AND STRUCTURES WITH IMPROVED FLUID DISTRIBUTION,
filed Jul. 21, 2000, also relates to such pad designs and
structures. The disclosure of application Ser. No. 09/621,969 is
also incorporated by reference herein as non-essential subject
matter.
SUMMARY OF THE INVENTION
[0013] The anode assemblies which are about to be described have
the ability to rotate at controlled speeds in both directions and
the mechanical strength to support a pad against which the wafer
surface can be pushed with controlled force. They have the
capability of receiving, containing, delivering, and distributing
process fluids. The assemblies can be used for an electrodeposition
process, as well as for a plating and planarization process or an
ECMD process. The assemblies may even be used in a CMP tool.
[0014] This invention provides further improved anode designs and
assemblies meeting the requirements of high quality metal plating
and deposition of super-planar films. The special attributes of
these further improved anode designs and assemblies are discussed
below.
[0015] In each embodiment of the invention, an anode assembly by
which a solution can be supplied to a surface of a semiconductor
substrate includes a housing defining an internal housing volume
into which the solution can flow. Each assembly also has a closure
for the internal housing volume through which the solution can be
discharged from the volume towards the substrate surface. A filter,
by which the internal housing volume can be divided into a first
chamber and a second chamber, is located between the first chamber
and the closure. When the solution is being supplied to the
surface, a flow of the solution into the second chamber occurs at a
higher rate than a flow of the solution into the first chamber, and
the flows are blended in the second chamber.
[0016] The housing includes at least one primary flow channel,
through which the solution can pass directly into the second
chamber, and at least one secondary flow channel, through which the
solution can pass directly into the first chamber. In one
embodiment, the primary and secondary flow channels are independent
of each other. In an alternative embodiment, the secondary flow
channel taps into the primary flow channel, and the secondary flow
channel is adapted to divert a portion of the solution which flows
through the primary flow channel to the first chamber.
[0017] The closure for the internal housing volume is a plate which
can cover the volume. A pad through which the solution can flow
lies over the plate.
[0018] A second filter can be provided between the second chamber
and the closure. The second filter can have smaller pores than the
first filter by which the internal housing volume can be divided
into the first and second chambers.
[0019] In one embodiment of the invention, a drain by which sludge
can be removed from the first chamber is provided. In a modified
construction, an external filter, which pre-filters the solution
before it enters the housing, can be utilized. In this case, the
housing mentioned above is an upper housing, and the assembly
further includes a lower housing, to which the external filter can
be mounted, adapted to receive at least part of the upper housing
in a volume defined thereby. In this construction, a fluid inlet
chamber is defined between the lower housing and the upper housing
when the lower housing receives this part of the upper housing.
[0020] An anode, usually a soluble anode, is typically received
within the first chamber. The solution used, moreover, is typically
an electrolyte solution out of which a conductive film can be
deposited onto the surface of the semiconductor substrate.
[0021] According to another aspect of the invention, a process of
supplying a solution to a surface of the semiconductor substrate
received in the anode assembly includes providing the housing which
has an internal volume. This volume is divided by a filter into a
first chamber and a second chamber located between the first
chamber and the surface. The solution is supplied to the housing,
and is then divided into one flow passing directly into the second
chamber and another flow passing into the second chamber through
the first chamber. The flows are blended together in the second
chamber, and the solution is then discharged from the housing
towards the surface.
[0022] According to yet another aspect of the invention, at least
one orifice can be used to remove air bubbles in the first chamber,
in the second chamber, or in both the first and second chambers. At
least one orifice in the first chamber and at least one orifice in
the second chamber could be used to de-bubble the solution or
prevent air bubble accumulation in the anode assembly. Air bubble
accumulation may be reduced by way of a controlled leak between
flanges.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 illustrates a conventional conductive material
electrodeposition apparatus.
[0024] FIG. 2 is a schematic illustration of an overall apparatus
in which an anode assembly according to the present invention can
be used.
[0025] FIG. 3 is a schematic sectional view of an anode assembly
according to the present invention in which a first anode housing
embodiment is used.
[0026] FIG. 4 is a schematic sectional view of a second anode
housing embodiment which can be used in the anode assembly.
[0027] FIG. 5 is a schematic sectional view of a third anode
housing embodiment which can be used in the anode assembly.
[0028] FIG. 6 is view similar to FIG. 3 but illustrating the
provision of a pre-filtering arrangement which may be utilized.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Each of the anode assemblies discussed below is particularly
adapted to be used with a soluble, i.e. consumable, anode. However,
it is contemplated that the anode assemblies could utilize or be
utilized as inert anodes and that the anode assemblies could be
used in etching applications as well as metal deposition
applications.
[0030] According to the invention, multiple anode filters, disposed
at several locations within the anode housing, are used. Filters
with different pore sizes are provided. Filters can also be
laminated between two porous sheets. FIG. 3 shows an anode assembly
9 with multiple filters and vertically configured primary and
secondary fluid delivery channels. In this anode configuration, a
primary anode filter 162 is disposed, by way of a filter mount 163,
within the anode chamber and essentially isolates the anode 164
from the rest of the anode chamber. The primary anode filter 162
may, for example, consist of one or multiple layers of napped
polypropylene cloth, or a polyethylene, polysulfone, hydrophilic
PVDF, or PFTE filter, with a particle or pore size of less than 1.0
micron, average, in diameter. The filter 162 entombs anode sludge
around the anode 164. Disposed away from the primary anode filter
162 is an upper anode filter 166. The pore size of the upper anode
filter 166 is preferably between 30 microns and 0.1 micron in
diameter. The upper anode filter 166 is secured in place in such a
way that it is effective in filtering the electrolyte solution or
fluid that communicates with the cathode.
[0031] A cavity A, within the anode housing 168, separates the
primary anode filter element or elements 162 and the upper or
secondary anode filter 166. The cavity or chamber A may be referred
to as an inter-filter blending chamber. In this chamber A, the
solution emanating from a lower anode chamber B blends or is mixed
with solution form at least one primary flow channel 170. Together,
the chambers A and B form an internal housing volume into which the
electrolyte solution can flow. The filter 162 thus divides the
internal housing volume into the lower anode chamber B and the
inter-filter blending chamber A, which is located between the lower
anode chamber and a top anode plate 174. In the embodiment
illustrated in FIG. 14, and in each of the embodiments shown in
FIGS. 15-17 which will be described, the blending of electrolyte
solution in the chamber A and the higher velocity, or rate of flow,
of the solution flowing from the primary flow channel enhance the
migration of copper or other metal ions from the lower anode
chamber B into the blending chamber A. This enhanced ion migration,
in other words, is provided by the blending which occurs in the
chamber A and because a flow of the electrolyte solution into the
blending chamber A occurs at a higher rate than a flow of the
solution into the anode chamber B. The dynamic mixing and migration
reduce the copper ion concentration difference between the lower
anode chamber B and the upper inter-filter blending chamber A, thus
reducing cell polarization due to any large ion concentration
differences in the cell.
[0032] The primary flow channel may be a vertical channel providing
for electrolyte solution or fluid communication and can be
incorporated into the anode housing. The primary and secondary flow
channels can both be formed as apertures within the wall of the
cell, as shown in FIG. 14. The primary flow channels 170 transfer
the bulk of the solution, more than 60%, directly into the
inter-filter blending chamber A. The solution is then filtered by
the very fine upper anode filter 166, which has apertures that,
typically, are less than 10.0 .mu.m, and preferably 0.02-0.5 .mu.m,
in average diameter. The filtered solution then is transferred to
the cathode via channels 172 in the anode top plate 174 and
channels 176 in a pad or pad assembly 178. The top anode plate 174
forms a closure for the internal housing volume and is secured to a
flange 175 defined at an upper end of the anode housing in any
appropriate way such as, for example, by bolts. The solution can
thus be discharged from the internal housing volume towards the
surface of a semiconductor substrate through the channels 172 in
the top plate 174 and through the channels 176 in the pad or pad
assembly. An O-ring seal 182 may be provided between an underside
of the top anode plate 174 and the flange 175 to prevent leakage of
plating or plating/planarization solution. The 0-ring may be
omitted to allow for controlled fluid leakage between the flanges.
Controlled leakage may be used to remove bubbles in the mixing
chamber. The top anode plate 174 may have essentially the same
construction as the pad support plate 22 of co-pending U.S. patent
application Ser. No. 09/568,584 mentioned earlier, while the pad or
pad assembly 178 may have essentially the same structure as the pad
8 of the same earlier mentioned application.
[0033] The secondary flow channels 180 convey the balance of the
electrolyte into the lower anode chamber or space B surrounding the
anode 164. The solution emanating from the lower anode chamber B is
filtered by the primary anode filter 162 before entering and mixing
with the solution in the inter-filter blending chamber A.
[0034] In other cell configurations, another, external, filter, or
a set of additional external filtering elements, may be provided.
FIG. 6 shows one such cell configuration, in which an external
filter 472 is disposed below an upper anode housing 468. This
external or "inter-bowl" filter 472 may be used to pre-filter the
electrolyte solution flowing in from a fluid inlet 474. The cell
configuration of FIG. 6 also includes an anode 464 disposed in a
lower anode chamber B which is separated from an inter-filter
blending chamber A by a primary anode filter 462. As in the
embodiment shown in FIG. 3, the primary anode filter 462 may
consist of one or multiple layers of filters or a filter cartridge
assembly with a particle or pore size between 1 and 5 microns in
diameter. The primary anode filter 462 entombs anode sludge around
the anode 464.
[0035] An upper anode filter (not shown in FIG. 6) is disposed away
from the primary anode filter 462, and it is to be understood that
a top anode plate (not shown in FIG. 6) is mounted to a flange 475
of upper anode bowl or housing 468, similar to the way in which the
top anode plate 174 is mounted to the flange 175 in the embodiment
shown in FIG. 3, thereby forming the inter-filter blending chamber
A.
[0036] The upper anode bowl 468 includes primary flow channels 470
and secondary flow channels 480 having the same configurations and
functions as the primary and secondary flow channels 170 and 180
shown in FIG. 3
[0037] A mentioned above, the external or inter-bowl filter 472 is
disposed below the upper anode housing 468. This external filter
can be mounted, e.g. by an appropriate filter mount, to a lower
anode housing or bowl 495, and pre-filters the solution before it
passes into the chambers A and B. The lower anode housing or bowl
495 defines a flange 497 which is connected, e.g. by bolts, to the
flange 475 of the upper anode bowl or housing 468. An additional
o-ring seal 492 can be disposed between facing surfaces of the
flanges 475 and 497 to provide sealing. In all other aspects, the
anode configuration of FIG. 6 is constructed in the same way as
that shown in FIG. 3.
[0038] FIG. 5 illustrates the incorporation of an anode sludge
drain 376 into another anode configuration. Anode sludge is
drained, at routine intervals or as needed, through the opening
provided by the anode sludge drain. Any practical device may be
used to suck or evacuate the lower anode chamber B during routine
wafer or workpiece processing or at any other suitable time. Thus,
it is not necessary to disassemble the anode housing 368 and remove
the primary anode filter 362 to de-sludge or clean the anode
chamber B, as is typical in prior art operations. The in situ anode
drain 376 improves plating cell utilization, because the need for
routine anode service is eliminated. The in situ de-sludge
operations also enhance the life of the lower anode filter.
[0039] In all other aspects, the anode configuration of FIG. 5 is
constructed in the same way as that shown in FIG. 3.
[0040] In other arrangements, the secondary flow to the lower anode
chamber B may be tapped from the primary flow channel orifices as
shown in FIG. 4. Here, apertures narrower than those of the primary
flow channels 270 form the secondary flow channels 280 and are used
to partition or divert a portion of the fluid in the primary
channels 270 into the lower anode chamber B of the housing 268
surrounding the anode 264. In all other aspects, the anode
configuration of FIG. 15 is constructed in the same way as that
shown in FIG. 14.
[0041] Besides the flow channels described above, an additional
small orifice (b), as indicated in FIGS. 3 and 4, or multiple
additional orifices (not shown) may be provided to allow the
electrolyte to leak out from the lower anode chamber B to the
outside of the anode housing 168, 268, 368, or 468. At least one of
these orifices is preferably provided to remove any bubbles that
may be trapped between the anode upper surface and the primary
anode filter. Similar air bleeder holes (a), as indicated in FIG.
3, may be incorporated in the top anode plate or in the upper walls
of the anode housing. When the bleeder holes are absent, a
de-gassing filtering element (not shown) may be used to de-gas the
solution before the solution is transferred to the plating cell.
For effective bubble removal, it is imperative that the filters
162, 262, 166, 462 and 362 be slanted or disposed at angles in the
range of 1 to 30 degrees with respect to the horizon with the bleed
hole disposed at the highest regions just below the filter.
[0042] In other operations, the lower anode chamber B may also be
activated as needed to remove any large bubbles that may be trapped
below the primary anode filter 162, 262, 362, or 462. The solution
can be drained, filtered, and returned to the solution
reservoir.
[0043] A similar draining arrangement may be incorporated in upper
regions of the anode housing 168, 268, 368, or 468. This will be
used to remove any large trapped air bubbles in chamber A, just
beneath the upper anode filter.
[0044] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *