U.S. patent application number 11/432164 was filed with the patent office on 2007-11-15 for reactors, systems, and methods for electroplating microfeature workpieces.
This patent application is currently assigned to Semitool, Inc.. Invention is credited to Rajesh Baskaran, Kyle M. Hanson, Paul R. McHugh, Gregory J. Wilson.
Application Number | 20070261964 11/432164 |
Document ID | / |
Family ID | 38684089 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070261964 |
Kind Code |
A1 |
Wilson; Gregory J. ; et
al. |
November 15, 2007 |
Reactors, systems, and methods for electroplating microfeature
workpieces
Abstract
Reactors, systems and methods for electroplating and/or
electro-etching microfeature workpieces. Reactors in accordance
with the invention have a first chamber configured to direct a
first processing solution to a processing zone, a second chamber
configured to contain a second processing solution different than
the first processing solution, and an ion exchange membrane between
the first chamber and the second chamber. The reactors also include
(a) a support member in the first chamber that contacts the ion
exchange membrane across the surface of the membrane, and (b) a
counter electrode in the second chamber. The ion exchange membrane
enables a low conductivity catholyte to be used in the first
chamber and an inert counter electrode in the second chamber. More
specifically, the ion exchange membrane prevents nascent oxygen
that evolves from the inert counter electrode from reaching the
catholyte to reduce oxidation of constituents of the catholyte,
consumption of organic additives in the anolyte, and/or
accumulation of bubbles and particulates at the workpiece.
Inventors: |
Wilson; Gregory J.;
(Kalispell, MT) ; McHugh; Paul R.; (Kalispell,
MT) ; Hanson; Kyle M.; (Kalispell, MT) ;
Baskaran; Rajesh; (Kalispell, MT) |
Correspondence
Address: |
PERKINS COIE LLP/SEMITOOL
PO BOX 1208
SEATTLE
WA
98111-1208
US
|
Assignee: |
Semitool, Inc.
Kalispell
MT
|
Family ID: |
38684089 |
Appl. No.: |
11/432164 |
Filed: |
May 10, 2006 |
Current U.S.
Class: |
205/148 ;
204/263 |
Current CPC
Class: |
C25D 17/002 20130101;
C25D 5/08 20130101 |
Class at
Publication: |
205/148 ;
204/263 |
International
Class: |
C25D 5/20 20060101
C25D005/20; C25B 9/00 20060101 C25B009/00 |
Claims
1. A reactor for electrochemical processing of microfeature
workpieces, comprising: a vessel; a workpiece holder having an
electrical contact to apply an electrical potential to a workpiece,
wherein the workpiece holder is configured to position a workpiece
in a processing zone relative to the vessel; a first chamber in the
vessel configured to direct a first processing solution to the
processing zone; an inlet at the first chamber; a second chamber in
the vessel configured to contain a second processing solution
different than the first processing solution; an ion exchange
membrane between the first chamber and the second chamber, the ion
exchange membrane having a first surface facing the first chamber
and a second surface facing the second chamber; a support member in
the first chamber at the inlet, wherein the support member contacts
the ion exchange membrane across the first surface of the ion
exchange membrane and directs a flow of the first processing
solution from the inlet toward the processing zone; and an
electrode in the second chamber.
2. The reactor of claim 1 wherein the support member comprises a
flow distributor having plate, standoffs projecting from the plate
and contacting the first surface of the ion exchange membrane, and
openings through the plate.
3. The reactor of claim 2 wherein the standoffs and the openings
are configured to direct a flow of the first processing solution
across the first surface of the ion exchange membrane and upwardly
through the openings.
4. The reactor of claim 2 wherein the plate has a first region and
a second region, and wherein the openings include first openings in
the first region and second openings in the second region that are
configured to provide a first electrical field component relative
to the first region and a second electrical field component
relative to the second region.
5. The reactor of claim 1 wherein the support member spans across
the first surface of the ion exchange membrane, and wherein the
support member has a plenum over the first surface of ion exchange
membrane and outlets above the plenum through which a flow of the
first processing solution passes toward the workpiece processing
zone.
6. The reactor of claim 1 wherein the support member comprises a
plate having a first side contacting the first surface of the ion
exchange membrane to control a profile of the ion exchange membrane
across the vessel and a second side facing the processing zone.
7. The reactor of claim 6 wherein the plate has lands with bearing
surfaces at the first side in contact with the ion exchange
membrane and a flow channel configured to distribute a flow of the
first processing solution across the first surface of the ion
exchange membrane.
8. The reactor of claim 1 wherein the electrode in the second
chamber comprises an inert anode.
9. The reactor of claim 1 wherein the electrode in the second
chamber has a planar upper region and a curved central region with
a slope that provides at least a substantially constant area of
electrode surface relative to a radial position across the
processing zone.
10. The reactor of claim 1, further comprising a seal encompassing
a peripheral edge of the ion exchange membrane.
11. The reactor of claim 10 wherein the seal comprises a ring
having a C-shaped cross-section with a slot configured to receive a
peripheral portion of the ion-exchange membrane.
12. The reactor of claim 11, further comprises a clamp engaged with
the seal to press a first portion of the seal against the first
surface of the ion exchange membrane and a second portion of the
seal against the second surface of the ion exchange membrane.
13. The reactor of claim 1, further comprising a flow diffuser
around the perimeter of the electrode.
14. The reactor of claim 13, further comprising a dielectric strap
between the perimeter of the electrode and the flow diffuser.
15. The reactor of claim 1 wherein the first chamber comprises a
catholyte compartment and the second chamber comprises an anolyte
compartment.
16. The reactor of claim 1 wherein the ion exchange membrane
comprise at least one of an anion exchange membrane and a cation
exchange membrane.
17. The reactor of claim 1 wherein the first chamber has a first
depth between the ion exchange membrane and the processing zone of
approximately 0.5 inch to 6 inches and the second chamber has a gap
between a perimeter portion of the electrode and the ion exchange
membrane of approximately 0.05 inch to 2 inches.
18. The reactor of claim 1 wherein: the plate has lands with
bearing surfaces at the first side in contact with the ion exchange
membrane and a flow channel configured to distribute a flow of the
first processing solution across the first surface of the ion
exchange membrane; the electrode in the second chamber comprises an
inert anode; and the first chamber comprises a catholyte
compartment and the second chamber comprises an anolyte
compartment.
19. The reactor of claim 1 wherein: the support member spans across
the first surface of the ion exchange membrane, and wherein the
support member has a plenum over the first surface of ion exchange
membrane and outlets above the plenum through which a flow of the
first processing solution passes toward the workpiece processing
zone; the electrode in the second chamber comprises an inert anode;
and the ion exchange membrane comprise at least one of an anion
exchange membrane and a cation exchange membrane.
20. The reactor of claim 1 wherein: the support member spans across
the first surface of the ion exchange membrane, and wherein the
support member has a plenum over the first surface of ion exchange
membrane and outlets above the plenum through which a flow of the
first processing solution passes toward the workpiece processing
zone; the electrode in the second chamber comprises an inert anode;
the ion exchange membrane comprise at least one of an anion
exchange membrane and a cation exchange membrane; and the first
chamber has a first depth between the ion exchange membrane and the
processing zone of approximately 0.5 inch to 6 inches and the
second chamber has a gap between a perimeter portion of the
electrode and the ion exchange membrane of approximately 0.05 inch
to 2 inches.
21. A reactor for electrochemical processing of microfeature
workpieces, comprising: a vessel; a workpiece holder having an
electrical contact to apply an electrical potential to a workpiece,
wherein the workpiece holder is configured to position a workpiece
in a processing zone relative to the vessel; a first chamber in the
vessel configured to direct a first processing solution to the
processing zone; a second chamber in the vessel configured to
contain a second processing solution different than the first
processing solution; an ion exchange membrane between the first
chamber and the second chamber, the ion exchange membrane having a
first surface facing the first chamber and a second surface facing
the second chamber; a flow director in the first chamber juxtaposed
to the first surface of the ion exchange membrane, the flow
director being configured to (a) distribute the first processing
solution across the first surface of the ion exchange membrane and
(b) direct the first processing fluid to the processing zone; and
an electrode in the second chamber.
22. The reactor of claim 21 wherein the flow director comprises
support member having plate, standoffs projecting from the plate
and contacting the first surface of the ion exchange membrane, and
openings through the plate.
23. The reactor of claim 22 wherein the standoffs and the openings
are configured to direct a flow of the first processing solution
across the first surface of the ion exchange membrane and upwardly
through the openings.
24. The reactor of claim 22 wherein the plate has a first region
and a second region, and wherein the openings include first
openings in the first region and second openings in the second
region that are configured to provide a first electrical field
component relative to the first region and a second electrical
field component relative to the second region.
25. The reactor of claim 22 wherein the flow director comprises a
support member that spans across the first surface of the ion
exchange membrane, and wherein the support member has a plenum over
the first surface of ion exchange membrane and outlets above the
plenum through which a flow of the first processing solution passes
toward the workpiece processing zone.
26. The reactor of claim 21 wherein the flow director comprises a
plate having a first side contacting the first surface of the ion
exchange membrane to control a profile of the ion exchange membrane
across the vessel and a second side facing the processing zone.
27. A reactor for electrochemical processing of microfeature
workpieces, comprising: a workpiece holder having an electrical
contact to apply an electrical potential to a workpiece, wherein
the workpiece holder is configured to position a workpiece in a
processing zone; an ion exchange membrane having a first side and a
second side; a first flow cell on the first side of the ion
exchange membrane configured to contain a first processing fluid,
the first flow cell having a first inlet through which the first
processing solution can flow; a first flow distributor in the first
flow cell configured to (a) direct a flow of the first processing
solution from the inlet to the first side of the ion exchange
membrane and (b) shape the first side of the ion exchange membrane;
a second flow cell on the second side of the ion exchange membrane
configured to contain a second processing solution separately from
the first processing solution; and an electrode in the second flow
cell, wherein the electrode is spaced apart from the ion exchange
membrane by a gap through which a flow of the second processing
solution can move radially outwardly across the second side of the
ion exchange membrane.
28. The reactor of claim 27, further comprising a flow diffuser
around the perimeter of the electrode.
29. The reactor of claim 28, further comprising a dielectric strap
between the perimeter of the electrode and the flow diffuser.
30. The reactor of claim 27 wherein the first flow cell comprises a
catholyte compartment and the second flow cell comprises an anolyte
compartment.
31. The reactor of claim 27 wherein the ion exchange membrane
comprise at least one of an anion exchange membrane and a cation
exchange membrane.
32. The reactor of claim 27 wherein the first flow cell has a first
depth between the ion exchange membrane and the processing zone of
approximately 0.5 inch to 6 inches and the gap between the
electrode and the ion exchange membrane is approximately 0.05 inch
to 2 inches.
33. An apparatus for electrochemically processing a seed layer on a
microfeature workpiece, comprising: a vessel; a workpiece holder
having an electrical contact to apply an electrical potential to a
workpiece, wherein the workpiece holder is configured to position a
workpiece in a processing zone relative to the vessel; a first
chamber in the vessel configured to direct a first processing
solution to the processing zone; a second chamber in the vessel
configured to contain a second processing solution different than
the first processing solution; an ion exchange membrane between the
first chamber and the second chamber, the ion exchange membrane
having a first surface facing the first chamber and a second
surface facing the second chamber; and an inert electrode in the
second chamber, wherein the electrode is spaced apart from the
processing zone by a distance to provide a sufficient electrical
field in a high pH processing solution suitable for seed layer
processing using 120V power.
34. The apparatus of claim 33 wherein the distance between the
electrode and the processing zone is approximately 1 inch to 6
inches.
35. The apparatus of claim 33 wherein the distance between the
electrode and the processing zone is approximately 1.5-4
inches.
36. An apparatus for electrochemically processing a microfeature
workpiece, comprising: a vessel; a workpiece holder having an
electrical contact to apply an electrical potential to a workpiece,
wherein the workpiece holder is configured to position a workpiece
in a processing zone relative to the vessel; a first chamber in the
vessel configured to direct a first processing solution to the
processing zone; a second chamber in the vessel configured to
contain a second processing solution different than the first
processing solution; an ion exchange membrane between the first
chamber and the second chamber, the ion exchange membrane having a
first surface facing the first chamber and a second surface facing
the second chamber; and a seal encompassing a peripheral edge of
the ion exchange membrane.
37. The apparatus of claim 36 wherein the seal comprises a ring
having a C-shaped cross-section with a slot configured to receive a
peripheral portion of the ion-exchange membrane.
38. The apparatus of claim 36, further comprising a clamp engaged
with the seal to press a first portion of the seal against the
first surface of the ion exchange membrane and a second portion of
the seal against the second surface of the ion exchange
membrane.
39. A method of electrochemically processing microfeature
workpieces, comprising: directing a flow of a first processing
solution across a first surface of an ion exchange membrane and to
a workpiece processing zone in a first flow cell of a vessel;
directing a flow of a second processing solution across a second
surface of the ion exchange membrane facing a second flow cell of
the vessel, wherein the first processing solution is different than
the second processing solution; and supporting a middle portion of
the first surface of the ion exchange membrane while directing the
flow of the second processing solution across the second surface of
the ion exchange membrane.
40. The method of claim 39, further comprising providing a support
member extending across the first flow cell, wherein the support
member has a first side contacting a middle portion of the first
surface of the ion exchange membrane and a flow channel through
which the flow of first processing solution flows across the first
surface of the ion exchange membrane.
41. The method of claim 40, wherein the support member further
comprises openings facing the processing zone, and wherein
directing the flow of the first processing solution comprises
passing the first processing solution through the openings to the
workpiece processing zone.
42. The method of claim 39 wherein the first processing solution
comprises a catholyte and the second processing solution comprises
an anolyte.
43. The method of claim 42, further comprising passing an
electrical current between an electrode in the second flow cell and
a workpiece at the processing zone in the first flow cell.
44. The method of claim 42, further comprising passing an
electrical current between an inert electrode in the second flow
cell and a workpiece at the processing zone in the first flow
cell.
45. The method of claim 44, further comprising using the first
processing solution for more than 2,000 Amp-minutes before changing
out the first processing solution.
46. The method of claim 44, further comprising using the first
processing solution for more than 8,000 Amp-minutes before changing
out the first processing solution.
47. The method of claim 39, further comprising: raising the second
processing solution to contact the second surface of the ion
exchange membrane; passing an electrical current between an inert
electrode in the second flow cell and a workpiece at the processing
zone in the first flow cell while the second processing solution
contacts the second surface of the ion exchange membrane; and
lowering the second processing solution from the second surface of
the ion exchange membrane after processing a surface of the
workpiece.
48. The method of claim 39, further comprising: providing a first
processing solution comprising a low conductivity, high pH
catholyte; passing an electrical current between an inert electrode
in the second flow cell and a workpiece at the processing zone in
the first flow cell while the second processing solution contacts
the second surface of the ion exchange membrane; and lowering the
second processing solution from the second surface of the ion
exchange membrane after processing a surface of the workpiece.
49. The method of claim 48, further comprising using the first
processing solution for more than 2,000 Amp-minutes before changing
out the first processing solution.
50. The method of claim 48, further comprising using the first
processing solution for more than 8,000 Amp-minutes before changing
out the first processing solution.
51. The method of claim 48, further comprising plating material
onto an ultra-thin seed layer while passing the electrical current
between the inert electrode and the workpiece.
52. The method of claim 48, further comprising plating material
onto an ultra-thin seed layer and exposed portions of a barrier
layer under the seed layer while passing the electrical current
between the inert electrode and the workpiece.
53. The method of claim 48, further comprising plating material
directly onto a barrier layer while passing the electrical current
between the inert electrode and the workpiece.
54. The method of claim 39 wherein the first processing solution
comprises a catholyte and the second processing solution comprises
an anolyte, and wherein the method further comprises using the
second processing solution for a cycle period before changing out
the second processing solution such that a desired conductivity and
ion concentration gradient are maintained in the first processing
solution.
55. The method of claim 39 wherein the first processing solution
comprises a catholyte and the second processing solution comprises
an anolyte, and wherein the method further comprises using the
second processing solution for at least 400 Amp-minutes before
changing out the second processing solution.
Description
TECHNICAL FIELD
[0001] This application relates to reactors, systems, and methods
for electroplating microfeature workpieces having a plurality of
microdevices integrated in and/or on the workpieces. Particular
aspects of the present invention are directed toward electroplating
workpieces using a low-profile reactor.
BACKGROUND
[0002] Microfeature devices, such as semiconductor devices,
imagers, displays, and micromechanical components, are generally
fabricated on and/or in microfeature workpieces using a number of
machines that deposit and/or etch materials from the workpieces.
Many current microfeature devices have interconnects and other very
small sub-micron sized features (e.g., 45-110 nanometers) formed by
depositing materials into small trenches or holes. One particularly
useful process for depositing materials into small trenches and/or
vias is electroplating. Typical electroplating techniques include
plating processes that deposit copper, solder, permalloy, gold,
silver, platinum, electrophoretic resist, and other materials onto
the workpieces.
[0003] One challenge of plating metals into narrow, deep trenches
or holes is that it is very difficult to completely fill the very
small features without creating voids or other non-uniformities in
the metal. For example, an ultra thin seed layer must be used to
deposit a metal into a trench having a dimension of 45 nm to 250 nm
so that the trench has sufficient vacant space for the subsequently
plated metal. Ultra thin seed layers, however, are problematic
because they may not cover the workpiece uniformly. For example,
ultra thin seed layers may have voids or other non-uniform physical
properties that can result in non-uniformities in the plated
material. This is particularly common on the side walls of such
small features. These challenges can be overcome by plating onto
the seed layers or plating a seed layer directly on a barrier layer
to provide competent seed layers that are well-suited for bulk
plating metals into trenches or holes with small critical
dimensions. One particularly useful method is to plate a material
using a processing solution with a low conductivity. Suitable
electrochemical processes for forming competent seed layers are
disclosed in U.S. Pat. No. 6,197,181, which is herein incorporated
by reference.
[0004] One problem with low conductivity baths, however, is that
they require more power to plate the material onto the workpieces
compared to acidic plating solutions with high conductivities. As a
result, conventional reactors require larger power supplies to
operate with the low conductivity baths used for plating onto seed
layers or plating directly onto barrier layers. This increases the
operating costs of conventional reactors because they consume more
power, and it may be inconvenient because the facility may need to
be renovated to provide high-voltage power outlets. Another
challenge of using low conductivity baths is that they are
generally more sensitive to shielding and geometries of the system.
As such, non-uniformities in the electrical field near the anode
are more likely to cause non-uniformities on the workpiece compared
to highly conductive baths.
[0005] Plating onto seed layers or plating materials directly onto
barrier layers in high pH processing solutions presents additional
challenges. For example, inert anodes are generally required in
high pH processing solutions because the high pH passivates
consumable copper anodes. This generally produces copper hydroxide
particles and/or flakes that may create defects on the wafer.
However, one drawback of using inert anodes is that the deposited
material exhibits a significant increase in resistivity over a
relatively small number of plating cycles (e.g., short bath life).
The resistivity of the deposited layers can be maintained in a
desired range by frequently changing the processing solution, but
this increases the operating costs of electrochemically processing
seed layers and/or depositing materials directly onto barrier
layers.
[0006] As a result, there is a need for a reactor that reduces
power consumption, enables the use of inert anodes in low
conductivity processing solutions, and enables use of high pH
processing solutions.
SUMMARY OF THE INVENTION
[0007] The present invention provides electroplating reactors for
processing seed layers, depositing materials directly onto barrier
layers, and/or depositing materials onto microfeature workpieces in
other applications. The reactors enable the use of an inert anode
and a low conductivity processing solutions so that the reactors of
the invention are not plagued by the flaking problems associated
with using consumable anodes in high pH solutions. The reactors
achieve this result by significantly reducing or eliminating
oxidation of certain constituents of the processing solution to
prolong its operating life. This reduces the operating costs of
using the reactor because the tool does not need to be frequently
shut down to change out the processing solution. A further benefit
of reactors in accordance with the invention is that they are
designed to operate within conventional power consumption ranges
and still plate a uniform layer of material on a seed layer or
directly on a barrier layer. The reactors also enable the use of
high pH processing solutions in the same system. As a result,
reactors in accordance with the invention are expected to further
reduce the operating costs of electroplating seed layers,
depositing materials directly onto barrier layers using low
conductivity processing solutions, and/or using high pH processing
solutions.
[0008] One aspect of reactors in accordance with the invention is
that they have a first chamber configured to direct a first
processing solution to a processing zone, a second chamber
configured to contain a second processing solution different than
the first processing solution, and an ion exchange membrane between
the first chamber and the second chamber. The reactors also include
(a) a support member in the first chamber that contacts the ion
exchange membrane across the surface of the membrane, and (b) a
counter electrode in the second chamber. The ion exchange membrane
enables a low conductivity catholyte to be used in the first
chamber and an inert counter electrode in the second chamber. More
specifically, the ion exchange membrane prevents nascent oxygen
that evolves from the inert counter electrode from reaching the
catholyte. This reduces oxidation of constituents of the catholyte,
which results in good quality deposits over a long bath life. The
ion exchange membrane is also quite useful in applications that use
a low conductivity, high pH catholyte. Therefore, reactors of the
invention provide a platform for using inert counter electrodes for
precision plating processes.
[0009] The support member provides several advantages for using a
low-profile reactor. The support member contacts the ion exchange
membrane to impart the desired contour or profile to the membrane.
This prevents the membrane from having a shape that disturbs the
electrical field or traps bubbles. The support member also directs
a flow of the first processing solution over the ion exchange
membrane and toward the processing zone, and the support member
configures the electrical field in the first chamber. The support
member enables the reactors to reduce the distance between the
processing zone and the electrode in the second chamber so that
less power is required to establish a sufficient electrical field
compared to conventional reactors. Reactors in accordance with the
invention accordingly enable the use of low conductivity, high pH
processing solutions with conventional power supplies that are
already widely used in plating tools.
[0010] Several other features of the reactors in accordance with
the invention enhance the uniformity of the layers deposited onto
the workpieces. For example, the electrode in the second chamber
can be shaped to further enhance the uniformity of the electrical
field at the processing zone. Therefore, several embodiments of
reactors in accordance with the invention also enable the uniform
deposition of materials onto workpieces using low conductivity,
high pH processing solutions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic illustration of a reactor for
electrochemically processing microfeature workpieces in accordance
with an embodiment of the invention.
[0012] FIG. 2 is a schematic diagram illustrating the operation of
a reactor in accordance with an embodiment of the invention.
[0013] FIG. 3 is a graph illustrating the resistivity of deposited
layers as a function of bath age using a conventional reactor and a
reactor in accordance with an embodiment of the invention.
[0014] FIG. 4 is a schematic illustration showing the operation of
a reactor in accordance with another embodiment of the
invention.
[0015] FIG. 5 is a cross-sectional view of a specific embodiment of
a reactor for electrochemically processing microfeature workpieces
in accordance with the invention.
[0016] FIG. 6 is a cross-sectional view illustrating a portion of
the reactor shown in FIG. 5.
[0017] FIG. 7A is a cross-sectional view of a support member for
use in a reactor in accordance with an embodiment of the
invention.
[0018] FIG. 7B is a bottom plan view of the support member shown in
FIG. 7A.
[0019] FIG. 7C is a detail view of a portion of the support member
shown in FIG. 7B.
[0020] FIG. 8 is a cross-sectional view of a counter electrode for
use in a reactor in accordance with an embodiment of the
invention.
[0021] FIG. 9 is an isometric view of a seal for use in a reactor
in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
[0022] FIGS. 1-9 illustrate several embodiments of reactors,
methods, and systems for electrochemically processing seed layers,
plating directly onto barrier layers, and depositing materials in
other applications. Several specific details of the invention are
set forth in the following description and in FIGS. 1-9 to provide
a thorough understanding of certain embodiments of the invention.
One skilled in the art, however, will understand that the present
invention may have additional embodiments, or that other
embodiments of the invention may be practiced without several of
the specific features explained in the following description.
[0023] FIG. 1 schematically illustrates a reactor 100 for plating
onto seed layers, directly onto barrier layers, or otherwise
depositing other materials onto workpieces. The reactor 100
includes a vessel 102, a first chamber 110 configured to direct a
flow of first processing solution to a processing zone 112, and a
second chamber 120 configured to contain a second processing
solution separate from the first processing solution. An ion
exchange membrane 130 separates the first processing solution in
the first chamber 110 from the second processing solution in the
second chamber 120, but selected ions can pass through the ion
exchange membrane 130. The ion exchange membrane 130 may be an
anion selective membrane in applications in which it is desirable
to allow anions to pass between the first and second chambers 110
and 120, or the ion exchange membrane 130 may be a cation selective
membrane in applications in which it is desirable to allow cations
to move between the first and second chambers 110 and 120. The ion
exchange membrane 130 enables the use of an inert counter electrode
with an anolyte in the second chamber 120 and a catholyte in the
first chamber 110. More specifically, because the ion exchange
membrane 130 prevents oxygen that evolves from an inert electrode
from affecting the conductivity of the catholyte in the first
chamber 110, counter electrode 160 may be an inert electrode.
Moreover, the ion exchange membrane 130 also prolongs bath life and
prevents bubbles from accumulating at the wafer. The reactor 100,
therefore, reduces the operating costs associated with using an
inert counter electrode because the inert counter electrode does
not affect the operating life of the catholyte in the first chamber
110.
[0024] The reactor 100 further includes a workpiece holder 140
having a plurality of electrical contacts 142 for applying an
electrical potential to a workpiece W mounted to the workpiece
holder 140. The workpiece holder 140 can be a movable head
configured to position the workpiece W in the processing zone 112
of the first chamber 110, and the workpiece holder 140 can further
be configured to rotate the workpiece W in the processing zone 112.
Suitable workpiece holders are disclosed in U.S. Pat. Nos.
6,080,291; 6,309,520; 6,527,925; 6,773,560; and U.S. patent
application Ser. No. 10/497,460; all of which are incorporated
herein by reference. In applications that use low conductivity
baths, it is expected that "dry" contact assemblies that seal
against the perimeter of the workpiece are efficacious. Suitable
dry contact assemblies are disclosed in U.S. Pat. Nos. 6,773,560
and 6,309,520. Such dry contact assemblies are also useful for
plating onto high resistance layers (e.g., seed layer enhancement
or direct-on-barrier plating).
[0025] The reactor 100 further includes (a) a support member 150 in
the first chamber 110 that contacts a first surface 132 of the
membrane 130, and (b) a counter electrode 160 in the second chamber
120. The support member 150 spaces the ion exchange membrane 130
apart from the workpiece processing zone 112 by a controlled
distance. This feature provides better control of the electrical
field at the processing zone 112 because the distance between the
ion exchange membrane 130 and the workpiece processing zone 112
affects the electrical field at the processing zone 112. The
support member 150 generally contacts the first surface 132 of the
ion exchange membrane 130 such that the distance between the first
surface 132 and the processing zone 112 is substantially the same
across the first chamber 110. Another feature of the support member
150 is that it also shapes the ion exchange membrane 130 so that
bubbles do not collect along a second side 134 of the membrane 130.
The support member 150 can also be configured to impart a slanted
or non-planar contour to the ion exchange membrane 130 for
increasing/decreasing the strength of the electrical field in local
regions of the processing zone 112 or providing additional bubble
control.
[0026] The support member 150 is further configured to direct a
flow F.sub.1 of the first processing solution laterally across the
first surface 132 of the ion exchange membrane 130 and vertically
to the processing zone 112. The support member 150 accordingly
controls the flow F.sub.1 of the first processing solution in the
first chamber 110 to provide the desired mass-transfer
characteristics in the processing zone 112. The support member 150
also shapes the electrical field in the first chamber 110. The
upper surface of the support member 150, for example, can be
contoured to shape the electrical field within the reactor or
otherwise control the electrical field of the workpiece. These
features of the support member 150 enable the reactor 100 to
provide good electrical and mass-transfer properties at the
processing zone 112 with a relatively short distance D.sub.1
between the processing zone 112 and the counter electrode 160. As a
result, the reactor 100 is particularly well suited for use with
low conductivity processing solutions because less power is
required to establish the desired electrical field at the
processing zone 112 over the relatively short distance D.sub.1
compared to conventional reactors in which the space in between the
workpiece W and the counter electrode is significantly larger.
[0027] The counter electrode 160 is spaced apart from the second
surface 134 of the ion exchange membrane 130 by a gap distance
D.sub.2 such that a flow F.sub.2 of the second processing solution
moves radially outward across the second surface 134 of the ion
exchange membrane 130 at a relatively high velocity. The flow
F.sub.2 of the second processing solution accordingly sweeps oxygen
bubbles and/or particles from the ion exchange membrane 130. The
short distance D.sub.2 also limits the volume of the second
processing solution in the second chamber 120 so that the second
processing solution can be quickly withdrawn from the second
chamber 120. The reactor 100 further includes a flow restrictor 170
around the counter electrode 160. The flow restrictor 170 is a
porous material that creates a back pressure in the second chamber
120 to provide a uniform flow between the counter electrode 160 and
the second surface 134 of the ion exchange membrane 130. As a
result, the electrical field can be consistently maintained because
the flow restrictor 170 mitigates velocity gradients in the second
processing solution where bubbles and/or particles can collect. The
configuration of the counter electrode 160 and the flow restrictor
170 also maintains a pressure in the second chamber during plating
that presses the ion exchange membrane 130 against the support
member 150 to impart the desired contour to the ion exchange
membrane 130.
[0028] The reactor 100 operates by positioning the workpiece W in
the processing zone 112, directing the flow F.sub.1 of the first
processing solution through the first chamber 110, and directing
the flow F.sub.2 of the second processing solution through the
second chamber 120. As the first and second processing solutions
flow through the reactor 100, an electrical potential is applied to
the workpiece W via the electrical contacts 142 and the counter
electrode 160 to establish an electrical field in the first and
second chambers 110 and 120. When the counter electrode 160 is
inert, the ion exchange membrane 130 prevents bubbles and particles
from entering the first chamber 110. As such, the bubbles that
evolve from the counter electrode 160 are carried out of the second
chamber 120 by the flow F.sub.2 of the second processing
solution.
[0029] The reactor 100 enables the efficient use of inert
electrodes and/or low conductivity solutions for several reasons.
First, the ion exchange membrane 130 mitigates oxidation of
constituents in the first processing solution(e.g., chelating
agents or other organic/inorganic species). Second, the total
distance D.sub.1 between the workpiece W and the counter electrode
160 is significantly less than conventional reactors. This reduces
the power necessary to establish the requisite electrical field
through low conductivity processing solutions, which reduces the
operating costs of the reactor 100 compared to conventional
reactors. Third, the support member 150 controls the shape of the
ion exchange membrane 130 and the flow F.sub.1 of the first
processing solution in the first chamber to provide the desired
electrical field and mass-transfer characteristics in the
processing zone 112. The support member 150 enables the total
distance D.sub.1 between the processing zone 112 and the counter
electrode 160 to be relatively short without unduly sacrificing the
desired electrical and mass-transfer properties at the processing
zone 112.
[0030] The reactor 100 illustrated in FIG. 1 is particularly useful
for processing ultra thin seed layers and/or plating materials
directly on barrier layers because it is well suited for using an
inert anode and a low conductivity, high pH processing solution
that provides the necessary nucleation for seed layer processing
and direct-on-barrier plating. More specifically, the ion exchange
membrane allows an inert anode to be used because the membrane
prevents nascent oxygen produced by inert anodes in such solutions
from oxidizing constituents in the catholyte and/or accumulating at
the workpiece. This arrangement accordingly improves the bath life
of the catholyte to improve the operating costs of the reactor. The
support member enhances control of the catholyte flow and the
electrical field near the workpiece processing zone so that the low
conductivity of the processing solution does not affect the quality
of the plated layer. The reactor 100 is accordingly well suited for
plating onto ultra-thin seed layers and/or directly onto a barrier
layer.
[0031] Furthermore, gold plating or plating other precious metal or
other metals that depend on use of an inert anode are plating
processes that are candidates for membrane reactors employing an
anion exchange membrane because the anodic process can be separated
from the catholyte by the ion exchange membrane. Properties of gold
deposits (such as roughness) will be fairly constant over the bath
life. The bath stability and bath life of these plating processes
can be greatly improved by isolating the plating species from the
rest of the bath solutions. The anodic oxidation reaction in the
anolyte of these plating baths does not influence the chelating
agents or other organic agents for precious metal plating in the
catholyte. The reactor can be operated in a continuous fashion
indefinitely with no anode maintenance as the metal salt is added
as a solution to the catholyte side and the metal ions are plated.
The counter ions move across the membrane and pass into solution in
the anolyte--where hydroxyl ions are lost due to the inert anodic
reaction of oxygen production.
[0032] Furthermore, there are advantages in using an anion exchange
membrane reactor plating for Sn (and other metals with multiple
valence states). Any metal with multiple valence states can be
plated from most of their stable states. Since the charge required
to deposit any metal is directly proportional to the electrons
required for their reduction, metals in their valence states
closest to their neutral states consume less energy for reduction
to metal. However most of the metals in their closest state with
their valence are inherently unstable, and therefore production
worthy plating is not feasible. With the reactor of this invention
inherently unstable plating solutions can still be applied for a
production worthy process because the separation of the anodic and
cathodic process results in lesser oxidation of the inherently
unstable metal species.
[0033] Most Sn--Ag--Cu alloy plating solutions prefer Sn(II) as the
species for Sn plating. For such alloy plating systems, the control
of Sn, Ag and Cu ions needs to be tight and the use of Sn, Ag, Cu
as an anode is ruled out. These anode systems could not only cause
stability issues by plating/reacting with the anodes, but also pose
a problem for uniform metal replenishment. The use of inert anodes,
however, causes nascent oxygen which not only oxidizes any organics
in the plating bath, but also oxidizes Sn(II) to a stable Sn((V)
ion. To prevent problems from occurring in such baths, the use of
an inert anode anionic membrane reactor in accordance with this
invention can greatly simplify replenishment schemes, and does not
oxidize any organic agents or any metal species. This separation
between catholyte and anolyte is ideal to solve such problems
encountered in plating baths. The baths are relatively more stable,
and the bath life can be extended.
[0034] Furthermore, for systems that use chelated baths, high pH,
or other systems where inert anodes are used, the reactor of this
invention can be very beneficial. First and foremost the advantages
of using the membrane reactor of this invention for a high pH Cu
bath with a chelating agent are: (a) the conductivity and pH of the
catholyte is fairly constant; (b) the properties of deposit (eg.
resistivity) are constant with bath age; (c) the chelating agent is
not oxidized at the inert anode; (d) bubbles from the inert anode
reaction are removed and therefore do not cause problems to the
cathode; and (e) changes in the conductivity and pH of the anolyte
are isolated from the catholyte and therefore the impact of such
changes on the catholyte are minimized.
[0035] FIG. 2 schematically illustrates an example of the operation
of the reactor 100 using an anion exchange membrane in a high pH
environment suitable for processing seed layers and/or plating
directly onto barrier layers. In this example, the first processing
solution in the first chamber 110 is a catholyte having a low
concentration of copper ions (e.g., copper sulfate-CuSO.sub.4), a
complexing agent (e.g., ethylenediamine-En) chelated with the
copper ions, boric acid (H.sub.2BO.sub.3.sup.-) as a pH buffer, and
tetramethylammonium hydroxide (TMAH) to adjust the pH of the
solution to be alkaline (e.g., approximately 9-10). The second
processing solution in the second chamber 120 is an anolyte. The
anolyte has a pH approximately equal to the catholyte (e.g., 9-10),
and the anolyte includes H.sub.2BO.sub.3.sup.-, TMAH, and other
constituents.
[0036] During a plating cycle, the second processing chamber 120 is
filled with the anolyte and an electrical potential is applied to
the workpiece W and the counter electrode 160. As the copper ions
are removed from the catholyte and plated onto the workpiece,
sulfate ions SO.sub.4.sup.2- accumulate in the catholyte near the
first surface 132 of the ion exchange membrane 130. Additionally,
the positively charged counter electrode 160 causes hydroxyl ions
OH.sup.- at the inert counter electrode 160 to liberate oxygen and
produce water. This creates a charge gradient that causes the
negatively charged sulfate ions to move from the first surface 132
to the second surface 134 of the ion exchange membrane 130. The
transfer of negatively charged sulfate ions from the catholyte to
the anolyte during a plating cycle maintains the charge and mass
balance of the system. Additionally, to maintain the concentration
of boric acid in the catholyte during plating, the concentration of
boric acid in the anolyte is significantly greater than that of the
catholyte to prevent the boric acid in the catholyte from moving to
the anolyte during plating. It should be noted that during an idle
state the anolyte level is dropped to separate the anolyte from the
ion exchange membrane to prevent boric acid from crossing the ion
exchange membrane 130. The hydroxyl ions could also move from the
catholyte to the anolyte during plating, but they are inhibited
from moving by maintaining the at least approximately the same pH
level in both solutions.
[0037] The operation of the reactor 100 in the example set forth in
FIG. 2 significantly increases the operating life of the catholyte
compared to conventional reactors without the ion exchange membrane
130. FIG. 3 is a graph illustrating test results showing the
resistivity of several 20 nanometer seed layers deposited using a
conventional reactor (line A) and the reactor 100 (line B) relative
to the bath age measured in Amp-minutes. As shown in FIG. 3, the
resistivity of seed layers deposited using a reactor without the
ion exchange membrane 130 (line A) increases rapidly with the age
of the bath. The example shown in FIG. 3 indicates that the bath
life in reactors without the ion exchange membrane is less than
2000 Amp-minutes. The resistivity of seed layers deposited in the
reactor 100 with the ion exchange membrane 130 (line B), however,
only increases gradually over time such that little change was
observed even at 10,000 Amp-minutes. These results can be achieved
with the reactor 100 because the nascent oxygen generated at the
inert anode in the second chamber 120 is prevented from passing to
the first chamber 110 where it can oxidize the ethylenediamine.
Moreover, because the ethylenediamine does not cross the ion
exchange barrier 130, there is no oxidation of this complexing
agent in the anolyte. As a result, the pre-anneal resistivity of
electrochemically deposited films using the reactor 100 is only
minimally affected by using an inert anode in a high pH solution.
The significant increase in the operating life of the anolyte and
the catholyte compared to reactors without an ion exchange membrane
reduces the operating costs of the reactor 100 because the reactor
does not need to be removed from production to frequently change
the processing solution.
[0038] Another feature of the operation of the reactor 100 in the
example illustrated in FIG. 2 is that pH does not drop
significantly in the catholyte solution. As a result,
tetramethylammonium hydroxide is not added to the catholyte, and
therefore tetramethylammonium hydroxide does not accumulate in the
catholyte. This simplifies the maintenance of both the catholyte
and the anolyte to further prolong the operational life of the
first and second processing solutions. Therefore, the reactor 100
maintains the catholyte composition, eliminates oxidation problems
associated with using an inert anode, and maintains consistent
electrical properties of the deposited layer over a long bath
life.
[0039] FIG. 4 illustrates an example of the operation of the
reactor 100 using a cation membrane. In this embodiment, the
anolyte has a low pH (e.g., 1.4) and the catholyte has a high pH
(e.g., 9.5). This causes proton migration (H.sup.+) from the
anolyte to the catholyte through the ion exchange membrane 130. The
protons replace the charge of the copper cations that are plated
from the catholyte to the workpiece. The reaction at the counter
electrode produces the protons by evolving oxygen via the
consumption of water. To maintain the high pH in the catholyte,
tetramethylammonium hydroxide is added to the catholyte. The cation
exchange membrane used in the example of FIG. 4 also prevents
oxygen produced at the counter electrode from oxidizing
constituents (e.g., ethylenediamine) in the catholyte to provide a
suitably long bath life in a manner similar to that described above
with reference to FIGS. 2 and 3. However, tetramethylammonium
(TMA.sup.+) and sulphate ions (SO.sub.4) build up in the catholyte
as the bath ages. This can limit the life of the bath to a certain
extent, but by no means to the extent caused by oxidation of the
ethylenediamine in the catholyte. Therefore, the reactor 100 with a
cation exchange membrane is also advantageous compared to reactors
without an ion exchange membrane.
[0040] FIG. 5 is a cross-sectional view illustrating a reactor 500
in accordance with a specific embodiment of the invention. The
reactor 500 is similar to the reactor 100, and thus it is
particularly well suited for operating with inert anodes. The
reactor 500 includes a vessel 502, a first chamber 510 for
containing a first processing solution, and a second chamber 520
for containing a second processing solution. The reactor 500
further includes the ion exchange membrane 130 between the first
chamber 510 and the second chamber 520, a support member 550 in the
first chamber 510, and a counter electrode 560 in the second
chamber 520. The first processing solution can be a catholyte and
the second processing solution can be an anolyte to achieve the
results explained above with reference to the reactor 100.
Additional aspects of the reactor 500 are further directed toward
specific embodiments of components that provide the desired
electrical field and/or mass transfer properties at the workpiece
processing zone in a low-profile reactor. Therefore, in addition to
providing a prolonged bath life for applications using an inert
electrode, the reactor 500 further provides good electrical and
mass transfer properties at the processing zone in low-profile
reactors that consume less power.
[0041] The first chamber 510 illustrated in FIG. 5 has an inner
vessel 512 within the vessel 502, and the inner vessel 512 has an
inner wall 513 and a rim 514 at the top of the wall. The wall 513
guides the flow F.sub.1 of the first processing solution to a
workpiece processing zone near the rim 514 and shapes the perimeter
of the electrical field. In the reactor 500 shown in FIG. 5, the
wall 513 defines an opening slightly smaller than the diameter of
the workpiece to shield a peripheral portion of the workpiece from
the electrical field.
[0042] FIG. 6 is a detailed cross-sectional view of the portion of
the reactor 500 identified in FIG. 5. The inner vessel 512 can
further include an inlet 516 through which the first processing
solution flows into the first chamber 510. The inlet 516 of the
first chamber initially passes upwardly through the inner vessel
512 and then flows downwardly toward the support member 550. The
inner vessel 512 can also include a vent 517 near the apex of the
inlet 516 for venting bubbles in the flow F.sub.1 of the processing
solution. As explained in more detail below with reference to the
support member 550, the support member 550 directs or otherwise
distributes the flow relative to the ion exchange membrane 130
and/or a processing zone near the rim 514. The support member 550,
for example, can distribute the flow F.sub.1 of the first
processing solution across the first surface of the ion exchange
membrane 130 and direct the flow F.sub.1 upwardly through the inner
vessel 512 toward the processing zone. The flow F.sub.1 of the
first processing solution proceeds to pass over the rim 514 and
exit through a chamber 518 between the inner vessel 512 and the
vessel 502. In low profile applications for plating onto ultra-thin
seed layers and/or directly onto barrier layers, the depth of the
first chamber between the upper surface of the ion exchange
membrane 130 and the processing zone is approximately 1 inch to 6
inches. Other depths, however, may be used in other applications.
For applications using low conductivity processing solutions, the
depth and geometry of the processing chamber is desirably
configured to use relatively low cell potentials. In a specific
example, the depth and geometry of the processing chamber can be
configured so that a cell potential of less than approximately 20V
can be used with processing solutions having conductivities of
about 0.5 mS/cm to about 50 mS/cm, or more specifically about 3
mS/cm to about 10 mS/cm, or still more specifically about 5 mS/cm.
The chamber, however, need not be limited for use with such low
cell potentials and low conductivity solutions in many
applications.
[0043] FIG. 7A is a cross-sectional view of the support member 550,
FIG. 7B is a bottom plan view of the support member 550, and FIG.
7C is a detailed view of a portion of FIG. 7B. Referring to FIGS.
5-7C together, the support member 550 is a dielectric member
defining a flow director that receives the flow F.sub.1 of the
first processing fluid from the inlet 516 (shown in FIG. 6). The
support member 550 includes a plurality of standoffs 552 that
contact the upper surface of the ion membrane 130 to impart the
desired contour to the ion membrane 130 during processing. The
standoffs 552, for example, can be lands with bearing surfaces that
contact the upper surface of the ion exchange membrane 130 to
control the profile of the ion exchange membrane 130. The standoffs
552 are spaced apart from one another to form a plenum 554 in a
lower portion of the support member 550 through which the flow
F.sub.1 of the first processing solution passes across the upper
surface of the ion membrane 130. One aspect of the support member
550 is that the plenum 554 provides a desired flow distribution
across the ion membrane 130. For example, the standoffs 552 can be
posts arranged such that the plenum 554 provides a flow across the
upper surface of the ion exchange membrane 130. The standoffs 552
can be arranged to restrict the flow through selected regions of
the plenum 554 in other embodiments to provide different flow rates
across in different areas of the support member 550.
[0044] The support member 550 further includes a plurality of
openings 556 that direct the flow F.sub.1 of the first processing
solution upwardly toward a processing zone near the rim 514 of the
inner vessel 512. The openings 556 are generally arranged in a
pattern to provide a generally uniform flow of the first processing
solution in a direction normal to a plane at the rim 514 of the
inner vessel 512, but the openings 556 can be arranged to provide a
non-uniform flow toward the workpiece. For example, the openings
556 can have a uniform size and distribution across the support
member 550, or the support member 550 can have a first region with
first openings and a second region with second openings that are
configured to provide different flow rates and/or different field
components of the electric field. The first and second openings can
have different sizes and/or be arranged in different patterns. The
openings 556 also act as virtual electrodes that define the shape
of the electrical field in the lower portion of the inner vessel
512. To avoid creating high magnitude points in the electrical
field at the processing zone, the spacing between the openings 556
can be correlated with the distance to the processing zone. For
example, the distance to the processing zone can be at least the
distance between the openings 556. In operation, the workpiece
holder (not shown in FIGS. 5-7B) rotates the workpiece in the
processing zone to mitigate the affect of local non-uniformities in
the flow and the electric field.
[0045] In an alternative embodiment, the support member in the
first chamber 510 is a porous material that provides a highly
uniform distribution of the electrical field and the flow of the
first processing solution. The porous material can be a porous
ceramic, a porous plastic, or any other suitable porous material.
Although porous support members may provide a highly controlled
distribution of the processing solution in the electrical field,
they may also be a source of particles that can contaminate the
workpiece. In still additional embodiments of the support member,
the upper surface of the support member 550 can be contoured to
shape the electrical field in the first chamber 510. For example,
the center of the support member 550 can have a thickness that is
less than the thickness at the perimeter to provide a higher
current at the center of the wafer relative to the perimeter. This
may enable more uniform plating on high resistance seed layers or
allow a desired non-uniform plating shape (e.g., a dome or dish)
for subsequent chemical-mechanical planarization. Additional
embodiments of the support member 550 can include a non-uniform
pattern of openings 556 to provide different flow rates and current
densities in the first chamber 510. For example, the density or
size of the openings can be greater at a center region of the
support member 550 than at a perimeter region to increase the
deposition rate at the center of the region relative to the
perimeter region.
[0046] Referring back to FIGS. 5 and 6, the second chamber 520 is
under the ion membrane 130, and the counter electrode 560 in the
second chamber 520 is spaced apart from the ion membrane 130 by a
small gap to provide a small channel for the flow F.sub.2 of the
second processing solution (as shown in FIG. 6). More specifically,
the flow F.sub.2 enters the second chamber 560 through an inlet 563
(FIG. 5) and progresses radially outwardly through a small gap 564
(FIG. 6) between an upper surface of the counter electrode 560 and
the lower surface of the ion exchange membrane 130 (FIG. 6). The
flow F.sub.2 of the second processing solution also passes through
an annular flow restrictor 570 around the perimeter of the counter
electrode 560 and into a channel in the lower part of the second
chamber 520. The flow restrictor 570 is a ring of a porous
polymeric material or other porous dielectric material. Referring
to FIG. 6, the counter electrode 560 is surrounded by a dielectric
strap 568 to electrically separate the counter electrode 560 from
the flow restrictor 570. This provides better control of the shape
of the electrical field at the counter electrode 560. The depth of
the second chamber 520 can be less than that of the first chamber
510. For example, in applications for plating onto ultra-thin seed
layers and/or directly onto barrier layer, the gap between the ion
exchange membrane 130 and the upper surface of the counter
electrode 560 can be approximately 0.05 inch to 2 inches. This gap,
however, is not limited to these dimensions in other
applications.
[0047] In operation, the second processing solution level can be
lowered during an idle state to separate the second processing
solution from the ion exchange membrane so that ions do not pass
through the ion exchange membrane. For example, when the reactor
500 is operated using an anion membrane as described above with
reference to FIG. 2, the anolyte is lowered so that
H.sub.2BO.sub.3.sup.- ions do not pass from the anolyte to the
catholyte. During a plating cycle, the flow F.sub.2 of the second
processing solution passes through the gap 564 (FIG. 6) so that the
anolyte in the second processing chamber 520 is at a higher
pressure than the catholyte in the first processing chamber 510.
This drives the ion exchange membrane 130 against the standoffs 552
of the support member 550 to impart the desired contour to the ion
exchange membrane 130 during a plating cycle. The small volume of
anolyte in the gap 564 allows the second chamber 520 to be quickly
drained/filled so that only a short period of time is spent
transitioning between the idle state and a plating cycle.
[0048] FIG. 8 is a cross-sectional view of an embodiment of the
counter electrode 560 used in the second chamber 520 of the reactor
500 shown in FIG. 5. The counter electrode 560 can have an exposed
surface 565 with a curved central region 567a and a generally
planer upper region 567b. The curved central region 567a has a
slope that avoids flow separation as the flow turns from an axial
flow to a radial flow and along at least a portion of the radial
flow. The curved region 567a also provides added electrical current
flow in the region of the opening. This feature, for example,
reduces the impacton the electrical field caused by having a
central inlet through the counter electrode. The counter electrode
can alternatively have conventional shapes with straight side walls
at the inlet and a planer upper region in other embodiments.
[0049] Referring to FIGS. 5 and 6, the reactor 500 further includes
a seal 900 for sealing the ion exchange membrane 130 in a manner
that prevents leakage between the first and second processing
solutions. FIG. 9 is an isometric view illustrating the seal 900 in
greater detail. The seal 900 can have a C-shape with a slot 910
between a lower flange 912 and an upper flange 914. Referring to
FIG. 6, the perimeter of the ion exchange membrane 130 is received
in the slot 910 and a lock-ring 920 with teeth 922 is pressed
against the seal 900 to clamp the ion exchange membrane 130 in the
slot 910. The seal 900 is expected to provide significant
advantages over using conventional O-ring seals because many types
of ion exchange membranes wick fluids to the perimeter region of
the membranes. The seal 900 captures fluids that wick through the
ion exchange membrane 130 in the slot 910 when the teeth 922 of the
lock-ring 920 are pressed against the seal 900. As a result, the
seal 900 prevents leakage between the first and second processing
solutions that occurs in conventional systems with O-ring
seals.
[0050] The term "microfeature workpiece" is used throughout to
include substrates upon which and/or in which microelectronic
devices, micromechanical devices, data storage elements,
micro-optics, and other features are fabricated. For example,
microfeature workpieces can be semiconductor wafers, glass
substrates, dielectric substrates, or many other types of
substrates. Microfeature workpieces generally have at least several
features with critical dimensions less than or equal to one micron,
and in many applications the critical dimensions of the smaller
features on microfeature workpieces are less than 0.25 micron or
even less than 100 nanometers. Furthermore, the terms
"electrochemical processing" and "electrochemical deposition"
include both electroplating processes and electroless plating
processes. Where the context permits, singular or plural terms may
also include the plural or singular term, respectively. Moreover,
unless the word "or" is expressly limited to mean only a single
item exclusive from other items in reference to a list of at least
two items, then the use of "or" in such a list is to be interpreted
as including (a) any single item in the list, (b) all of the items
in the list, or (c) any combination of the items in the list.
Additionally, the term "comprising" is used throughout to mean
including at least the recited feature(s) such that any greater
number of the same features and/or types of other features and
components are not precluded.
[0051] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
For example, the reactors and systems disclosed herein are not
limited for use with low conductivity, high pH solutions. In many
applications, the processing solution can have only a low
conductivity, only a high pH, or neither a low conductivity nor a
high pH. Accordingly, the invention is not limited except as by the
appended claims.
* * * * *