U.S. patent application number 10/158220 was filed with the patent office on 2003-02-27 for methods and systems for controlling current in electrochemical processing of microelectronic workpieces.
Invention is credited to Gibbons, Kenneth, McHugh, Paul R., Wilson, Gregory J..
Application Number | 20030038035 10/158220 |
Document ID | / |
Family ID | 26854842 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030038035 |
Kind Code |
A1 |
Wilson, Gregory J. ; et
al. |
February 27, 2003 |
Methods and systems for controlling current in electrochemical
processing of microelectronic workpieces
Abstract
A method and system for electrolytically processing a
microelectronic workpiece. In one embodiment, the method includes
contacting the workpiece with an electrolytic fluid, positioning
one or more electrodes in electrical communication with the
workpiece, directing an electrical current through the electrolytic
fluid from the electrodes to the workpiece or vice versa, and
actively changing a distribution of the current at the workpiece
during the process. For example, the current can be changed such
that a current ratio of at least one electrical current to the sum
of the electrical currents shifts from a first current ratio value
to a second current ratio value. Accordingly, the current applied
to the workpiece can be adjusted to achieve a target shape for a
conductive layer on the workpiece, or to account for temporally
and/or spatially varying characteristics of the electrolytic
process.
Inventors: |
Wilson, Gregory J.;
(Kalispell, MT) ; Gibbons, Kenneth; (Kalispell,
MT) ; McHugh, Paul R.; (Kalispell, MT) |
Correspondence
Address: |
PERKINS COIE LLP
PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Family ID: |
26854842 |
Appl. No.: |
10/158220 |
Filed: |
May 29, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60294690 |
May 30, 2001 |
|
|
|
Current U.S.
Class: |
205/96 ;
205/118 |
Current CPC
Class: |
C25D 17/008 20130101;
C25D 17/10 20130101; C25D 7/123 20130101; C25D 5/18 20130101; C25D
5/611 20200801; C25D 17/001 20130101 |
Class at
Publication: |
205/96 ;
205/118 |
International
Class: |
C25D 005/00; C25D
005/02 |
Claims
I/We claim:
1. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting the microelectronic workpiece
with an electrolytic fluid; positioning at least one electrode in
electrical communication with the electrolytic fluid; directing at
least one electrical current through the at least one electrode to
produce a first current distribution in the electrolytic fluid; and
actively changing the first current distribution to produce a
second current distribution in the electrolytic fluid while the
microelectronic workpiece is in contact with the electrolytic
fluid, the second current distribution being different than the
first current distribution.
2. The method of claim 1 wherein the at least one electrode is one
of a plurality of electrodes and wherein directing at least one
electrical current includes directing a plurality of currents
through the plurality of electrodes.
3. The method of claim 1 wherein directing at least one electrical
current includes directing a plurality of electrical currents
through a plurality of electrodes with a current ratio of the at
least one of the electrical current to a sum of all of the
electrical currents having a first current ratio value, and wherein
actively changing the first current distribution includes directing
the plurality of electrical currents through the plurality of
electrodes with the current ratio having a second current ratio
value.
4. The method of claim 1 wherein the microelectronic workpiece has
an exposed layer of conductive material that is initially generally
uniformly thick from a central region of the microelectronic
workpiece to a peripheral region of the microelectronic workpiece,
and wherein the method further comprises adding conductive material
to the layer to increase a thickness of the layer at the central
region by a first amount and increase the thickness of the layer at
the peripheral region by a second amount greater than the first
amount.
5. The method of claim 1 wherein the microelectronic workpiece has
an exposed layer of conductive material that is initially generally
uniformly thick from a central region of the microelectronic
workpiece to a peripheral region of the microelectronic workpiece,
and wherein the method further comprises adding conductive material
to the layer to increase a thickness of the layer at the central
region by a first amount and increase the thickness of the layer at
the peripheral region by a second amount less than the first
amount.
6. The method of claim 1 wherein the microelectronic workpiece has
an exposed layer of conductive material that initially has a
thickness with a first uniformity, and wherein the method further
comprises adding conductive material to the layer to increase a
thickness of the layer and increase a uniformity of the thickness
from the first uniformity to a second uniformity.
7. The method of claim 1 wherein the microelectronic workpiece has
a layer of conductive material, the layer having topographical
features, and wherein the method further comprises directing the at
least one electrical current to produce the first current
distribution while the topographical features are being filled with
conductive material, and directing the at least one electrical
current to produce the second current distribution while conductive
material is applied to the filled topographical features.
8. The method of claim 1 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises providing to a first portion of the
microelectronic workpiece current at a first current density and
providing to a second portion of the microelectronic workpiece
current at a second current density, the first current density
being at least approximately the same as the second current
density, the first and second current densities being at least
approximately equal to each other before and after actively
changing the first current distribution.
9. The method of claim 1 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises: filling features on the surface of
the microelectronic workpiece by applying a negative potential to
the microelectronic workpiece while directing the electrical
currents through the plurality of electrodes; and building a layer
of conductive material on the microelectronic workpiece after the
features have been filled by applying a negative potential to the
microelectronic workpiece, wherein a current density distribution
across a surface of the microelectronic workpiece is approximately
the same while filling the features and while building the layer of
conductive material.
10. The method of claim 1, wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises: filling features on the surface of
the microelectronic workpiece by providing to the microelectronic
workpiece current at an approximately constant current density over
the surface of the microelectronic workpiece; and applying current
to the microelectronic workpiece at a spatially varying current
density to form a conductive layer having a selected shape.
11. The method of claim 1, wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises: filling features on the surface of
the microelectronic workpiece by providing to the microelectronic
workpiece current at an approximately constant current density over
the surface of the microelectronic workpiece; and applying current
to the microelectronic workpiece at a spatially varying current
density to form a conductive layer having a generally concave
profile, a generally convex profile or a generally flat
profile.
12. The method of claim 1 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
directing at least one electrical current includes providing a
first electrical current to an inner portion of the microelectronic
workpiece at a first current density that is at least approximately
constant with time, and providing a second electrical current to an
outer portion of the microelectronic workpiece at a second current
density that is at least approximately constant with time and that
is at least approximately the same as the first current
density.
13. The method of claim 1, further comprising positioning a shield
adjacent to the least one electrode while the microelectronic
workpiece contacts the electrolytic fluid, and wherein actively
changing the first current distribution includes changing a
configuration and/or relative position of the shield while the
first microelectronic workpiece is in contact with the electrolytic
fluid.
14. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting the microelectronic workpiece
with an electrolytic fluid; positioning a plurality of electrodes
in electrical communication with the electrolytic fluid; directing
a plurality of electrical currents through the plurality of
electrodes with a current ratio of at least one of the electrical
currents to a sum of all of the electrical currents having a first
current ratio value; and directing the plurality of electrical
currents through the plurality of electrodes with the current ratio
having a second current ratio value.
15. The method of claim 14 wherein the plurality of electrodes
includes four electrodes, and wherein the method further comprises
changing a current passing through each of the four electrodes
while the electrodes are in fluid and electrical communication with
the microelectronic workpiece.
16. The method of claim 14 wherein the microelectronic workpiece
has an exposed layer of conductive material that is initially
generally uniformly thick from a central region of the
microelectronic workpiece to a peripheral region of the
microelectronic workpiece, and wherein the method further comprises
adding conductive material to the layer to increase a thickness of
the layer at the central region by a first amount and increase the
thickness of the layer at the peripheral region by a second amount
greater than the first amount.
17. The method of claim 14 wherein the microelectronic workpiece
has an exposed layer of conductive material that is initially
generally uniformly thick from a central region of the
microelectronic workpiece to a peripheral region of the
microelectronic workpiece, and wherein the method further comprises
adding conductive material to the layer to increase a thickness of
the layer at the central region by a first amount and increase the
thickness of the layer at the peripheral region by a second amount
less than the first amount.
18. The method of claim 14 wherein the microelectronic workpiece
has an exposed layer of conductive material that initially has a
thickness with a first uniformity, and wherein the method further
comprises adding conductive material to the layer to increase a
thickness of the layer and increase a uniformity of the thickness
from the first uniformity to a second uniformity.
19. The method of claim 14 wherein the microelectronic workpiece
has a layer of conductive material, the layer having topographical
features, further comprising selecting the current ratio to have
the first current ratio value while the topographical features are
being filled with conductive material, and selecting the current
ratio to have the second current ratio value while conductive
material is applied to the filled topographical features, the first
current ratio value being different than the second current ratio
value.
20. The method of claim 14 wherein directing the plurality of
electrical currents with the current ratio having a second current
ratio value includes changing the current ratio while the
microelectronic workpiece is in electrical communication with the
plurality of electrodes.
21. The method of claim 14 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises providing to a first portion of the
microelectronic workpiece current at a first current density and
providing to a second portion of the microelectronic workpiece
current at a second current density, the first current density
being at least approximately the same as the second current
density.
22. The method of claim 14 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises: filling features on a surface of the
microelectronic workpiece by applying a negative potential to the
microelectronic workpiece while directing the electrical currents
through the plurality of electrodes; and building a layer of
conductive material on the microelectronic workpiece after the
features have been filled by applying a negative potential to the
microelectronic workpiece, wherein a current density distribution
across a surface of the microelectronic workpiece is approximately
the same while filling the features and while building the layer of
conductive material.
23. The method of claim 14, wherein current density is equivalent
to current per unit area of the microelectronic workpiece, and
wherein the method further comprises: filling features on a surface
of the microelectronic workpiece by providing to the
microelectronic workpiece current at an approximately constant
current density over the surface of the microelectronic workpiece;
and applying current to the microelectronic workpiece at a
spatially varying current density to form a conductive layer having
a selected shape.
24. The method of claim 14, wherein current density is equivalent
to current per unit area of the microelectronic workpiece, and
wherein the method further comprises: filling features on a surface
of the microelectronic workpiece by providing to the
microelectronic workpiece current at an approximately constant
current density over the surface of the microelectronic workpiece;
and applying current to the microelectronic workpiece at a
spatially varying current density to form a conductive layer having
a generally concave profile, a generally convex profile or a
generally flat profile.
25. The method of claim 14 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
directing a plurality of electrical currents includes providing a
first electrical current to an inner portion of the microelectronic
workpiece at a first current density that is at least approximately
constant with time, and providing a second electrical current to an
outer portion of the microelectronic workpiece at a second current
density that is at least approximately constant with time and that
is at least approximately the same as the first current
density.
26. The method of claim 14, further comprising changing the current
ratio in a generally monotonic, incremental manner between the
first current ratio value and the second current ratio value.
27. The method of claim 14 wherein the plurality of electrodes
includes a first electrode in electrical communication with a first
portion of the microelectronic workpiece and a second electrode in
electrical communication with a second portion of the
microelectronic workpiece positioned outwardly from the first
portion, and wherein the method further comprises decreasing an
electrical current applied to the first electrode relative to an
electrical current applied to the second electrode and/or
increasing an electrical current applied to the second electrode
relative to an electrical current applied to the first
electrode.
28. The method of claim 14, further comprising applying a copper
material to the microelectronic workpiece in an electrolytic
deposition process.
29. The method of claim 14, further comprising applying to the
microelectronic workpiece at least one of a metal and a metal alloy
in an electrolytic deposition process.
30. The method of claim 14 wherein the plurality of electrodes
function as anodes and wherein the microelectronic workpiece
functions as a cathode, and wherein the method further comprises
adding electrically conductive material to the microelectronic
workpiece.
31. The method of claim 14 wherein the plurality of electrodes
function as cathodes and wherein the microelectronic workpiece
functions as an anode, and wherein the method further comprises
removing electrically conductive material from the microelectronic
workpiece.
32. The method of claim 14 wherein directing the electrical
currents through the electrolytic fluid includes directing the
electrical currents through an electrolytic fluid having a
conductivity of from about 5 mS/cm to about 500 mS/cm.
33. The method of claim 14 wherein the microelectronic workpiece is
a first microelectronic workpiece, and wherein the method further
comprises changing a conductivity of the electrolytic fluid after
contacting the first microelectronic workpiece with the
electrolytic fluid and before contacting a second microelectronic
workpiece with the electrolytic fluid.
34. The method of claim 14 wherein the microelectronic workpiece is
a first microelectronic workpiece, and wherein the method further
comprises: positioning a shield adjacent to at least one of the
electrodes while the first microelectronic workpiece contacts the
electrolytic fluid; and changing a configuration and/or relative
position of the shield after contacting the first microelectronic
workpiece with the electrolytic fluid and before contacting a
second microelectronic workpiece with the electrolytic fluid.
35. The method of claim 14 wherein the sum of the electrical
currents remains constant as the current ratio changes.
36. The method of claim 14 wherein the sum of the electrical
currents changes as the current ratio changes.
37. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting the microelectronic workpiece
with an electrolytic fluid; positioning a plurality of electrodes
and electrical communication with the electrolytic fluid, the
plurality of electrodes including a first electrode and a second
electrode; directing a first electrical current through the first
electrode and a first portion of the microelectronic workpiece;
directing a second electrical current through the second electrode
and a second portion of the microelectronic workpiece while the
first electrical current is directed through the first electrode
and the first portion of the microelectronic workpiece, wherein a
first current ratio of the first electrical current to a sum of the
first and second electrical currents has a first value, and wherein
a second current ratio of the second electrical current to a sum of
the first and second electrical currents has a second value;
changing the first current ratio from the first value to a third
value and directing the first electrical current at the third
value; and changing the second current ratio from the second value
to a fourth value and directing the second electrical current at
the fourth value.
38. The method of claim 37 wherein the microelectronic workpiece
has a layer of conductive material, the layer having topographical
features, and wherein changing the first current ratio includes
selecting the first current ratio to have the first value while the
topographical features are being filled with conductive material,
and selecting the first current ratio to have the third value while
conductive material is applied to the filled topographical
features, the first value being different than the third value.
39. The method of claim 37, further comprising: directing a fifth
electrical current through the electrolytic fluid between a third
electrode and a third portion of the microelectronic workpiece
while directing the first and second electrical currents; and
directing a sixth electrical current through the electrolytic fluid
between a fourth electrode and a fourth portion of the
microelectronic workpiece while directing the first and second
electrical currents.
40. The method of claim 37 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the method further comprises providing to the first portion of the
microelectronic workpiece current at a first current density and
providing to the second portion of the microelectronic workpiece
current at a second density, the first current density being at
least approximately the same as the second current density.
41. The method of claim 37 wherein the second portion of the
microelectronic workpiece is positioned outwardly from the first
portion of the microelectronic workpiece, and wherein changing the
first current ratio includes decreasing an electrical current
applied to the first electrode relative to an electrical current
applied to the second electrode and/or increasing an electrical
current applied to the second electrode relative to an electrical
current applied to the first electrode.
42. The method of claim 37 wherein directing the first electrical
current through the electrolytic fluid includes directing the first
electrical current through an electrolytic solution having a
conductivity of from about 5 mS/cm to about 500 mS/cm.
43. The method of claim 37 wherein directing the first electrical
current through the electrolytic fluid includes directing the first
electrical current through an electrolytic fluid having a
conductivity of about 5 mS/cm or less to about 500 mS or more.
44. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting a surface of the microelectronic
workpiece with an electrolytic fluid; positioning a plurality of
electrodes in electrical communication with the microelectronic
workpiece, the plurality of electrodes including at least a first
electrode and a second electrode; directing a first electrical
current through the electrolytic fluid between the first electrode
and a first portion of the microelectronic workpiece; directing a
second electrical current through the electrolytic fluid between
the second electrode and a second portion of the microelectronic
workpiece while the first electrical current is directed between
the first electrode and the first portion of the microelectronic
workpiece; varying the first and second electrical currents as a
function of time while directing the first and second electrical
currents and while the microelectronic workpiece contacts the
electrolytic fluid; while the first electrical current varies with
time, providing the first electrical current at a current density
per unit area of the microelectronic workpiece that varies by less
than about 10% of a 3.sigma. value over the surface of the
microelectronic workpiece; and while the second electrical current
varies with time, providing the second electrical current at a
current density per unit area of the microelectronic workpiece that
varies by less than about 10% of a 3.sigma. value over the surface
of the microelectronic workpiece.
45. The method of claim 44 wherein providing the first electrical
current includes providing the first electrical current at a
current density per unit area of the microelectronic workpiece that
varies by less than about 5% of a 3.sigma. value over the surface
of the microelectronic workpiece, and wherein providing the second
electrical current includes providing the second electrical current
at a current density per unit area of the microelectronic workpiece
that varies by less than about 5% of a 3.sigma. value over the
surface of the microelectronic workpiece.
46. The method of claim 44 wherein the second portion of the
microelectronic workpiece is disposed outwardly from the first
portion, and wherein varying the first electrical current as a
function of time includes changing a ratio of the first electrical
current to a sum of the first and second electrical currents,
further wherein varying the second electrical current as a function
of time includes changing a ratio of the second current to a sum of
the first and second electrical currents.
47. The method of claim 44 wherein varying the first and second
electrical currents as a function of time includes temporally
changing a ratio of the first electrical current to a sum of
electrical currents passing through all electrodes in fluid and
electrical communication with the microelectronic workpiece and
temporally changing a ratio of the second electrical current to the
sum electrical currents passing through all electrodes in fluid and
electrical communication with the microelectronic workpiece.
48. The method of claim 44 wherein the microelectronic workpiece
has a layer of conductive material, the layer having topographical
features, the layer having a thickness that is different at an
inner portion of the microelectronic workpiece than at an outer
portion of the microelectronic workpiece, and wherein varying the
first and second electrical currents as a function of time includes
selecting a ratio of the first electrical current to a first sum of
all electrical currents passing through the microelectronic
workpiece to have a first value while the topographical features
are being filled with conductive material, and selecting a ratio of
the first electrical current to a second sum of all electrical
currents passing through the microelectronic workpiece to have a
second value while conductive material is applied to the filled
topographical features, the first value being different than the
second value.
49. The method of claim 44 wherein varying the first and second
electrical currents as a function of time includes applying to the
first electrode a current at a first value while filling features
on a surface of the microelectronic workpiece, and applying to the
first electrode a current at a second value while building a layer
of conductive material on the microelectronic workpiece after the
features have been filled.
50. The method of claim 44, further comprising: directing a third
electrical current through the electrolytic fluid between a third
electrode and a third portion of the microelectronic workpiece;
directing a fourth electrical current through the electrolytic
fluid between a fourth electrode and a fourth portion of the
microelectronic workpiece; and varying the third and fourth
electrical currents as a function of time while directing the third
and fourth electrical currents and while the microelectronic
workpiece contacts the electrolytic fluid.
51. The method of claim 44 wherein the first and second portions of
the microelectronic workpiece are disposed outwardly from a third
and fourth portion of the microelectronic workpiece, and wherein a
third electrode is positioned in fluid and electrical communication
with the third portion, further wherein a fourth electrode is
positioned in fluid and electrical communication with the fourth
portion, and wherein the method further comprises providing to the
first and second portions of the microelectronic workpiece current
at a first current per unit area of the microelectronic workpiece
and providing to the fourth portion of the microelectronic
workpiece current at a second current per unit area of the
microelectronic workpiece, the first current per unit area being at
least approximately constant while the first and second electrodes
are in electrical communication with the microelectronic workpiece,
the second current per unit area temporally varying while the
fourth electrode is in electrical communication with the
microelectronic workpiece.
52. The method of claim 44, further comprising: filling features on
a surface of the microelectronic workpiece by applying a negative
potential to the microelectronic workpiece while directing the
first and second currents; and building a layer of conductive
material on the microelectronic workpiece after the features have
been filled by applying a negative potential to the microelectronic
workpiece while directing the first and second currents, wherein a
current per unit area of the of the microelectronic workpiece is
approximately the same while filling the features and while
building the layer of conductive material.
53. The method of claim 44 wherein directing the first electrical
current through the electrolytic fluid includes directing the first
electrical current through an electrolytic solution having a
conductivity of about 5 mS/cm to about 500 mS/cm.
54. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting a surface of the microelectronic
workpiece with an electrolytic fluid; positioning a plurality of
electrodes in electrical communication with the microelectronic
workpiece, the plurality of electrodes including at least a first
electrode and a second electrode; directing a first electrical
current through the electrolytic fluid between a first electrode
and a first portion of the microelectronic workpiece; directing a
second electrical current through the electrolytic fluid between a
second electrode and a second portion of the microelectronic
workpiece while the first electrical current is directed between
the first electrode and the first portion of the microelectronic
workpiece; applying the first electrical current at a first value
while filling features of the microelectronic workpiece with
conductive material, then applying the first electrical current at
a second value different than the first value while applying
conductive material to the filled features; and applying the second
electrical current at a first value while filling features of the
microelectronic workpiece with conductive material, then applying
the second electrical current at a second value while applying
conductive material to the filled features, wherein a ratio of the
first value of the first current to a sum of the first values of
the first and second currents is different than a ratio of the
second value of the first current to a sum of the second values of
the first and second currents.
55. The method of claim 54, further comprising changing a ratio of
the first electrical current to the sum of the first and second
electrical currents as a function of time and changing a ratio of
the second electrical current to the sum of the first and second
electrical currents as a function of time.
56. The method of claim 54 wherein the first electrode is in
electrical communication with a first portion of the
microelectronic workpiece and the second electrode is in electrical
communication with a second portion of the microelectronic
workpiece positioned outwardly from the first portion, and wherein
the method further comprises decreasing an electrical current
applied to the first electrode relative to an electrical current
applied to the second electrode and/or increasing an electrical
current applied to the second electrode relative to an electrical
current applied to the first electrode.
57. The method of claim 54 wherein directing the first electrical
current through the electrolytic fluid includes directing the first
electrical current through an electrolytic solution having a
conductivity of from about 5 mS/cm to about 500 mS/cm.
58. The method of claim 54 wherein directing the first electrical
current through the electrolytic fluid includes directing the first
electrical current through an electrolytic fluid having a
conductivity of about 5 mS/cm or less to about 500 mS/cm or
more.
59. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting the microelectronic workpiece
with an electrolytic fluid, the microelectronic workpiece having an
inner region, an outer region disposed outwardly from the inner
region, and a conductive layer disposed on the inner region and the
outer region; removing conductive material from the conductive
layer in the outer region cover zero or non-zero; and after
removing conductive material from the conductive layer in the outer
region, simultaneously adding conductive material to the conductive
layer in both the outer region and the inner region.
60. The method of claim 59 wherein removing conductive material
from the conductive layer in the outer region includes removing
conductive material at a first rate, and wherein the method further
comprises removing conductive material from the conductive layer in
the inner region at a second rate less than the first rate.
61. The method of claim 59, further comprising adding conductive
material to the conductive layer in the inner region and the outer
region prior to removing conductive material from the conductive
layer.
62. The method of claim 59, further comprising positioning first
and second electrodes in electrical communication with the
microelectronic workpiece, the first electrode being disposed
inwardly from the second electrode, and wherein removing conductive
material in the outer region while adding conductive material to
the conductive layer in the inner region includes removing material
to the second electrode and adding conductive material from the
first electrode.
63. The method of claim 59 wherein simultaneously adding conductive
material to the conductive layer in both the outer region and the
inner region includes directing a first current through the
electrolytic fluid between a first electrode and the inner region
and directing a second current through the electrolytic fluid
between a second electrode and the outer region.
64. The method of claim 59 wherein simultaneously adding conductive
material to the conductive layer in both the outer region and the
inner region includes directing a first current through the
electrolytic fluid between a first electrode and the inner region,
directing a second current through the electrolytic fluid between a
second electrode and the outer region, and varying the first and
second currents over time while the microelectronic workpiece
contacts the electrolytic fluid.
65. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting the microelectronic workpiece
with an electrolytic fluid, the microelectronic workpiece having an
inner region, an outer region disposed outwardly from the inner
region, and a conductive layer disposed on the inner region and the
outer region; directing conductive material from a first electrode
toward the microelectronic workpiece; attracting to a second
electrode spaced apart from the first electrode and the
microelectronic workpiece at least a portion of the conductive
material in the electrolytic fluid that would otherwise attach to
the microelectronic workpiece; while attracting at least a portion
of the conductive material to the second electrode, adding at least
a portion of the conductive material to the conductive layer in at
least the inner region; changing a current applied to the first
electrode as a function of time; and after attracting at least a
portion of the conductive material to the second electrode,
simultaneously adding conductive material to the conductive layer
in both the outer region and the inner region.
66. The method of claim 65 wherein attracting to the second
electrode at least a portion of the conductive material includes
changing a rate at which at least a portion of the conductive
material is attracted to the second electrode.
67. The method of claim 65 wherein simultaneously adding conductive
material to the conductive layer in both the outer region and the
inner region includes directing a first current through the
electrolytic fluid between a first electrode and the inner region,
directing a second current through the electrolytic fluid between a
second electrode and the outer region, and varying the first and
second currents over time while the microelectronic workpiece
contacts the electrolytic fluid.
68. The method of claim 65 wherein simultaneously adding conductive
material in both the outer region and the inner region includes
applying a first electrical current to the first electrode and
applying a second electrical current to the second electrode, and
wherein changing a current applied to the first electrode includes
changing a ratio of the first electrical current to a sum of the
first and second electrical currents as a function of time.
69. A method for electrolytically processing a microelectronic
workpiece, comprising: contacting a surface of a microelectronic
workpiece with an electrolytic fluid; directing a plurality of
electrical currents from a corresponding plurality of electrodes
through the electrolytic fluid and to a corresponding plurality of
portions of the microelectronic workpiece; for each electrical
current, varying a ratio of the electrical current to a sum of
electrical currents applied to the microelectronic workpiece; and
for each portion of the microelectronic workpiece at any point in
time, maintaining a current density per unit area of the
microelectronic workpiece at approximately the same value while the
microelectronic workpiece contacts the electrolytic fluid.
70. The method of claim 69, further comprising maintaining
approximately the same current density per unit area of the
microelectronic workpiece while features are being filled and while
the conductive material is applied to the filled features.
71. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and at least one electrode
configured to be in electrical communication with the
microelectronic workpiece to produce a first current distribution
at a surface of the microelectronic workpiece; and a device
operatively coupled to the processing station to actively change
the first current distribution and produce a second current
distribution at the surface of the microelectronic workpiece while
the microelectronic workpiece is in contact with the electrolytic
fluid, the second current distribution being different than the
first current distribution.
72. The system of claim 71 wherein the at least one electrode is
one of a plurality of electrodes and wherein the device includes a
controller having a computer operable medium with contents capable
of: directing a plurality of electrical currents through the
plurality of electrodes, with a current ratio of at least one of
the electrical currents to a sum of all of the electrical currents
having a first current ratio value; and changing the current ratio
from the first current ratio value to a second current ratio value
and directing the at least one electrical current at the second
current ratio value through one of the electrodes.
73. The system of claim 71 wherein the microelectronic workpiece
has a layer of conductive material, the layer having topographical
features, and wherein the at least one electrode is one of a
plurality of electrodes, further wherein the at least one electrode
is one of a plurality of electrodes and wherein the device includes
a controller having a computer operable medium with contents
capable of: directing a plurality of electrical currents through
the plurality of electrodes, with a current ratio of at least one
of the electrical currents to a sum of all of the electrical
currents having a first current ratio value; and changing the
current ratio from the first current ratio value to a second
current ratio value and directing the at least one electrical
current at the second current ratio value through one of the
electrodes with the current ratio of the at least one electrical
current having the first value while the topographical features are
being filled with conductive material, and having the second value
while conductive material is applied to the filled topographical
features, the first value being different than the second
value.
74. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and a plurality of electrodes,
all configured to be in electrical communication with the
microelectronic workpiece; and a controller having a computer
operable medium with contents capable of: directing a plurality of
electrical currents through the plurality of electrodes, with a
current ratio of at least one of the electrical currents to a sum
of all of the electrical currents having a first current ratio
value; and changing the current ratio from the first current ratio
value to a second current ratio value and directing the at least
one electrical current at the second current ratio value through
one of the electrodes.
75. The system of claim 74 wherein the plurality of electrodes
includes four electrodes, and wherein the computer operable medium
has contents capable of changing a current passing through each of
the four electrodes while the electrodes are in electrical
communication with the microelectronic workpiece.
76. The system of claim 74 wherein the microelectronic workpiece
has a layer of conductive material, the layer having topographical
features, and wherein the computer operable medium has contents
capable of directing the electrical currents with the current ratio
of the at least one electrical current having the first value while
the topographical features are being filled with conductive
material, and having the second value while conductive material is
applied to the filled topographical features, the first value being
different than the second value.
77. The system of claim 74 wherein the computer operable medium is
capable of changing the current ratio in a generally monotonic,
incremental manner between the first current ratio value and the
second current ratio value.
78. The system of claim 74 wherein computer operable medium is
capable of maintaining the sum of the electrical currents constant
as the current ratio changes.
79. The system of claim 74 wherein the computer readable medium is
capable of changing the sum of the electrical currents as the
current ratio changes.
80. The system of claim 74 wherein the computer readable medium is
capable of directing the plurality of electrical currents to fill
features on a surface of the microelectronic workpiece by providing
to the microelectronic workpiece current at an approximately
constant current density over the surface of the microelectronic
workpiece and apply current to the microelectronic workpiece at a
spatially varying current density to form a conductive layer having
a selected shape.
81. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and a plurality of electrodes,
all configured to be in electrical communication with the
microelectronic workpiece; and a controller having a computer
operable medium with contents capable of: directing a first
electrical current through first electrode and a first portion of
the microelectronic workpiece; directing a second electrical
current through the second electrode and a second portion of the
microelectronic workpiece while the first electrical current is
directed through the first electrode and the first portion of the
microelectronic workpiece, wherein a first current ratio of the
first electrical current to a sum of the first and second
electrical currents has a first value, and wherein a second current
ratio of the second electrical current to a sum of the first and
second electrical currents has a second value; changing the first
current ratio from the first value to a third value and directing
the first electrical current at the third value; and changing the
second current ratio from the second value to a fourth value and
directing the second electrical current at the fourth value.
82. The system of claim 81 wherein the microelectronic workpiece
has a layer of conductive material, the layer having topographical
features, and wherein the computer operable medium is capable of
directing current with the first current ratio having the first
value while the topographical features are being filled with
conductive material, and having the third value while conductive
material is applied to the filled topographical features, the first
value being different than the third value.
83. The system of claim 81 wherein current density is equivalent to
current per unit area of the microelectronic workpiece, and wherein
the computer operable medium is capable of providing to the first
portion of the microelectronic workpiece current at a first current
density and providing to the second portion of the microelectronic
workpiece current at a second density, the first current density
being at least approximately the same as the second current
density.
84. The system of claim 81 wherein the second portion of the
microelectronic workpiece is positioned outwardly from the first
portion of the microelectronic workpiece, and wherein the computer
operable medium is capable of decreasing an electrical current
applied to the first electrode relative to an electrical current
applied to the second electrode and/or increasing an electrical
current applied to the second electrode relative to an electrical
current applied to the first electrode.
85. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and a plurality of electrodes,
all configured to be in electrical communication with the
microelectronic workpiece, the plurality of electrodes including at
least a first electrode and a second electrode; and a controller
having a computer operable medium with contents capable of:
directing a first electrical current through the electrolytic fluid
between the first electrode and a first portion of the
microelectronic workpiece; directing a second electrical current
through the electrolytic fluid between the second electrode and a
second portion of the microelectronic workpiece while the first
electrical current is directed between the first electrode and the
first portion of the microelectronic workpiece; varying the first
and second electrical currents as a function of time while
directing the first and second electrical currents and while the
microelectronic workpiece contacts the electrolytic fluid; while
the first electrical current varies with time, providing the first
electrical current at a current density per unit area of the
microelectronic workpiece that varies by less than about 10% of a
3.sigma. value over the surface of the microelectronic workpiece;
and while the second electrical current varies with time, providing
the second electrical current at a current density per unit area of
the microelectronic workpiece that varies by less than about 10% of
a 3.sigma. value over the surface of the microelectronic
workpiece.
86. The system of claim 85 wherein the second portion of the
microelectronic workpiece is disposed outwardly from the first
portion, and wherein the computer operable medium is capable of
changing a ratio of the first electrical current to a sum of the
first and second electrical currents, and changing a ratio of the
second current to a sum of the first and second electrical
currents.
87. The system of claim 85 wherein the computer operable medium is
capable of directing to the first electrode a current at a first
value while features on a surface of the microelectronic workpiece
are being filled, and directing to the first electrode a current at
a second value while a layer of conductive material is built on the
microelectronic workpiece after the features have been filled.
88. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and a plurality of electrodes,
all configured to be in electrical communication with the
microelectronic workpiece; and a controller having a computer
operable medium with contents capable of: directing a first
electrical current through the electrolytic fluid from one of a
first electrode and a first portion of the microelectronic
workpiece to the other; directing a second electrical current
through the electrolytic fluid from one of a second electrode and a
second portion of the microelectronic workpiece to the other while
the first electrical current is directed between the first
electrode and the first portion of the microelectronic workpiece;
directing the first electrical current at a first value while
filling features of the microelectronic workpiece with conductive
material, then applying the first electrical current at a second
value different than the first value while applying conductive
material to the filled features; and directing the second
electrical current at a first value while filling features of the
microelectronic workpiece with conductive material, then applying
the second electrical current at a second value while applying
conductive material to the filled features, wherein a ratio of the
first value of the first current to a sum of the first values of
the first and second currents is different than a ratio of the
second value of the first current to a sum of the second values of
the first and second currents.
89. The system of claim 88 wherein the computer operable medium is
capable of changing a ratio of the first electrical current to the
sum of the first and second electrical currents as a function of
time and changing a ratio of the second electrical current to the
sum of the first and second electrical currents as a function of
time.
90. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and a plurality of electrodes,
all configured to be in electrical communication with the
microelectronic workpiece; and a controller having a computer
operable medium with contents capable of: directing first
electrical currents through at least one of the plurality of
electrodes to remove conductive material from an outer region of a
conductive layer of the microelectronic workpiece; and after
removing conductive material from the conductive layer in the outer
region, directing second electrical currents through at least one
of the plurality of electrodes to simultaneously add conductive
material to the conductive layer in both the outer region and the
inner region of the conductive layer.
91. The system of claim 90 wherein the computer operable medium is
capable of directing currents for simultaneously adding conductive
material to the conductive layer in both the outer region and the
inner region by directing a first current through the electrolytic
fluid between a first electrode and the inner region and directing
a second current through the electrolytic fluid between a second
electrode and the outer region.
92. The system of claim 90 wherein the computer operable medium is
capable of directing currents for simultaneously adding conductive
material to the conductive layer in both the outer region and the
inner region by directing a first current through the electrolytic
fluid between a first electrode and the inner region, directing a
second current through the electrolytic fluid between a second
electrode and the outer region, and varying the first and second
currents over time while the microelectronic workpiece contacts the
electrolytic fluid.
93. A system for electrolytically processing a microelectronic
workpiece, comprising: a processing station having a vessel
configured to carry an electrolytic fluid, the processing station
further having at least one contact and a plurality of electrodes
configured to carry a plurality of electrical currents, wherein the
at least one contact and the plurality of electrodes are configured
to be in electrical communication with the microelectronic
workpiece; and a controller having a computer operable medium with
contents capable of: for each electrical current, varying a ratio
of the electrical current to a sum of electrical currents applied
to the microelectronic workpiece; and for each portion of the
microelectronic workpiece at any point in time, maintaining a
current density per unit area of the microelectronic workpiece at
approximately the same value while the microelectronic workpiece
contacts the electrolytic fluid.
94. The system of claim 93 wherein the computer operable medium is
capable of directing currents for maintaining approximately the
same current density per unit area of the microelectronic workpiece
while features are being filled and while the conductive material
is applied to the filled features.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to Provisional
Application No. 60/294,690, filed May 30, 2001, which is
incorporated herein in its entirety by reference.
TECHNICAL FIELD
[0002] This application relates to methods and systems for
enhancing the performance of plating and other electrochemical
processes.
BACKGROUND
[0003] Microelectronic devices, such as semiconductor devices and
field emission displays, are generally fabricated on and/or in
microelectronic workpieces using several different types of
machines ("tools"). Many such processing machines have a single
processing station that performs one or more procedures on the
workpieces. Other processing machines have a plurality of
processing stations that perform a series of different procedures
on individual workpieces or batches of workpieces. In a typical
fabrication process, one or more layers of conductive materials are
formed on the workpieces during deposition stages. The workpieces
are then typically subject to etching and/or polishing procedures
(.e., planarization) to remove a portion of the deposited
conductive layers for forming electrically isolated contacts and/or
conductive lines.
[0004] Plating tools that plate metals or other materials on the
workpieces are becoming an increasingly useful type of processing
machine. Electroplating and electroless plating techniques can be
used to deposit copper, solder, permalloy, gold, silver, platinum
and other metals onto workpieces for forming blanket layers or
patterned layers. A typical copper plating process involves
depositing a copper seed layer onto the surface of the workpiece
using chemical vapor deposition (CVD), physical vapor deposition
(PVD), electroless plating processes, or other suitable methods.
After forming the seed layer, a blanket layer or patterned layer of
copper is plated onto the workpiece by applying an appropriate
electrical potential between the seed layer and an anode in the
presence of an electroprocessing solution. The workpiece is then
cleaned, etched and/or annealed in subsequent procedures before
transferring the workpiece to another processing machine.
[0005] FIG. 1 illustrates an embodiment of a single-wafer
processing station 1 that includes a container 2 for receiving a
flow of electroplating solution from a fluid inlet 3 at a lower
portion of the container 2. The processing station 1 can include an
anode 4, a plate-type diffuser 6 having a plurality of apertures 7,
and a workpiece holder 9 for carrying a workpiece 5. The workpiece
holder 9 can include a plurality of electrical contacts for
providing electrical current to a seed layer on the surface of the
workpiece 5. The seed layer acts as a cathode when it is biased
with a negative potential relative to the anode 4. In operation the
electroplating fluid flows around the anode 4, through the
apertures 7 in the diffuser 6 and against the plating surface of
the workpiece 5. The electroplating solution is an electrolyte that
conducts electrical current between the anode 4 and the cathodic
seed layer on the surface of the workpiece 5. Therefore, ions in
the electroplating solution are reduced at the surface of the
workpiece 5 to form a metal film.
[0006] The plating machines used in fabricating microelectronic
devices must meet many specific performance criteria. For example,
many processes must be able to form small contacts in vias that are
less than 0.5 .mu.m wide, and are desirably less than 0.1 .mu.m
wide. The plated metal layers accordingly often need to fill vias
or trenches that are on the order of 0.1 .mu.m wide, and the layer
of plated material should also be deposited to a desired, uniform
thickness across the surface of the workpiece 5. One factor that
influences the uniformity of the plated layer is the current
density at the workpiece. Current density is influenced by the mass
transfer of electroplating solution at the surface of the
workpiece. This parameter is generally influenced by the velocity
of the flow of the electroplating solution perpendicular to the
surface of the workpiece. Other factors that influence the current
density at the workpiece are the design of the electroplating
chamber, the position of the anodes, the initial seed layer
resistance and the current applied to the anodes.
[0007] One concern of existing electroplating equipment is
providing a uniform mass transfer at the surface of the workpiece.
Referring to FIG. 1, existing plating tools generally use the
diffuser 6 to enhance the uniformity of the fluid flow
perpendicular to the face of the workpiece. Although the diffuser 6
improves the uniformity of the fluid flow, it produces a plurality
of localized areas of increased flow velocity perpendicular to the
surface of the workpiece 5 (indicated by arrows 8). The localized
areas generally correspond to the position of the apertures 7 in
the diffuser 6. The increased velocity of the fluid flow normal to
the substrate in the localized areas increases the mass transfer of
the electroplating solution in these areas. This typically results
in faster plating rates in the localized areas over the apertures
7. Although many different configurations of apertures have been
used in plate-type diffusers, these diffusers may not provide
adequate uniformity for the precision required in many current
applications.
[0008] Another concern of existing plating tools is that the
diffusion layer in the electroplating solution adjacent to the
surface of the workpiece 5 can be disrupted by gas bubbles or
particles. For example, bubbles can be introduced to the plating
solution by the plumbing and pumping system of the processing
equipment, or they can evolve from inert anodes. Consumable anodes
are often used to prevent or reduce the evolvement of gas bubbles
in the electroplating solution, but these anodes erode and they can
form a passivated film surface that must be maintained. Consumable
anodes, moreover, often generate particles that can be carried in
the plating solution. As a result, gas bubbles and/or particles can
flow to the surface of the workpiece 5, which disrupts the
uniformity and affects the quality of the plated layer.
[0009] Still another challenge of plating uniform layers is
providing a desired electrical field at the surface of the
workpiece 5. The distribution of electrical current in the plating
solution is a function of the uniformity of the seed layer across
the contact surface, the resistance of the seed layer, the
configuration/condition of the anode, and the configuration of the
chamber. However, the current density profile on the plating
surface can change. For example, the current density profile
typically changes during a plating cycle because plating material
covers the seed layer, or it can change over a longer period of
time because the shape of consumable anodes changes as they erode
and the concentration of constituents in the plating solution can
change. Therefore, it can be difficult to maintain a desired
current density at the surface of the workpiece 5 and can
accordingly be difficult to form uniform void-free plated layers.
In one particular example, the current density can be significantly
higher near the junctions between the contact elements and the
workpiece 5 than at points distant from these junctions, an effect
referred to in the industry as the "terminal effect." This can
result in electroplated layers that (a) are not uniformly thick
and/or (b) contain voids and/or (c) non-uniformly incorporating
impurities or defects. Both of these characteristics tend to reduce
the effectiveness and/or reliability of the devices formed from the
workpiece 5.
SUMMARY
[0010] The present invention is directed toward methods and systems
for electrolytically processing microelectronic workpieces. One
aspect of several embodiments of the invention includes
electrolytically depositing conductive material on a
microelectronic workpiece by applying current to the workpiece
through an electrolytic fluid from one or more electrodes. The
distribution of current in the electrolytic fluid is actively
changed during the course of the process. For example, in one
embodiment, the current is applied by a plurality of electrodes in
a manner that can account for different plating characteristics at
different portions of the workpiece, and the current applied to
individual electrodes is changed to account for changes in behavior
as the thickness of the conductive material on the workpiece
increases. As a result, conductive materials such as copper are
deposited on the workpiece at a uniform current density or other
desired current density to provide a conductive layer having the
desired properties. Several embodiments of the present invention
accordingly apply the current to the individual electrodes to
counteract the terminal effect between the contact elements and the
workpiece. Additional embodiments of the invention compensate for
irregularities in the seed layers or other aspects of single-wafer
electrochemical deposition techniques to inhibit voids and produce
plated layers with a desired thickness.
[0011] The current applied to the electrodes is varied in a variety
of manners. For example, in one embodiment the current is varied
such that the ratio of the current applied to one electrode
relative to the currents provided by all the electrodes changes
over time. This ratio has one value while features in a seed layer
of the workpiece are filled, and another value while a blanket
layer is applied to the filled features. In another arrangement,
the current is applied such that the current density per unit area
of the microelectronic workpiece varies by less than about ten
percent of a 3.sigma. value across the surface of the
workpiece.
[0012] In still further embodiments, the current is varied in other
manners. For example, in one embodiment the current is varied to
create a domed or dished blanket layer on an initially flat seed
layer, or a flat blanket layer on an initially domed or dished seed
layer. In another embodiment, current is provided at an opposite
polarity to at least one of the electrodes to either remove
material from the workpiece or attract material that would
otherwise attach to the workpiece, again, to form a conductive
layer having a desired shape and/or uniformity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic diagram of an electroplating chamber
in accordance with the prior art.
[0014] FIG. 2 is an isometric view of an electroprocessing machine
having electroprocessing stations for processing microelectronic
workpieces in accordance with an embodiment of the invention.
[0015] FIG. 3 is a cross-sectional view of an electroprocessing
station having a processing chamber for use in an electroprocessing
machine in accordance with an embodiment of the invention. Selected
components in FIG. 3 are shown schematically.
[0016] FIG. 4 is an isometric view showing a cross-sectional
portion of a processing chamber taken along line 4-4 of FIG.
8A.
[0017] FIGS. 5A-5D are cross-sectional views of a distributor for a
processing chamber in accordance with an embodiment of the
invention.
[0018] FIG. 6 is an isometric view showing a different
cross-sectional portion of the processing chamber of FIG. 4 taken
along line 6-6 of FIG. 8B.
[0019] FIG. 7A is an isometric view of an interface assembly for
use in a processing chamber in accordance with an embodiment of the
invention.
[0020] FIG. 7B is a cross-sectional view of the interface assembly
of FIG. 7A.
[0021] FIGS. 8A and 8B are top plan views of a processing chamber
that provide a reference for the isometric, cross-sectional views
of FIGS. 4 and 6, respectively.
[0022] FIGS. 9A-9D are flow diagrams illustrating processes in
accordance with embodiments of the invention.
[0023] FIG. 10A is a table illustrating predicted electrode
currents as a function of initial seed layer thickness for
instantaneously uniform deposition, simulating a multi-stage
deposition process in accordance with an embodiment of the
invention.
[0024] FIG. 10B is a graph illustrating the predicted electrode
currents as a function of initial seed layer thickness based on the
table of FIG. 10A.
[0025] FIG. 11 illustrates predicted electrode currents as a
function of time for a multi-stage process in accordance with an
embodiment of the invention.
[0026] FIG. 12 is a graphical comparison of film non-uniformity as
a function of film thickness for an existing single-step plating
process and a multi-stage process in accordance with an embodiment
of the invention.
[0027] FIG. 13 is a graph of predicted current density as a
function of location on a microelectronic workpiece for a
multi-stage process in accordance with an embodiment of the
invention.
[0028] FIG. 14 is a graph of predicted current density as a
function of location on a microelectronic workpiece for an existing
single-stage process.
[0029] FIG. 15 is a graph of experimentally determined initial and
final conductive layer thicknesses for a microelectronic workpiece
processed in accordance with an embodiment of the invention.
[0030] FIG. 16 is a graph illustrating experimentally determined
initial and final thicknesses for a concave conductive layer
deposited in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
[0031] The following description discloses the details and features
of several embodiments of electrochemical reaction vessels for use
in electrochemical processing stations and integrated tools to
process microelectronic workpieces. The term "microelectronic
workpiece" is used throughout to include a workpiece formed from a
substrate upon which and/or in which microelectronic circuits or
components, data storage elements or layers, and/or
micro-mechanical elements are fabricated. It will be appreciated
that several of the details set forth below are provided to
describe the following embodiments in a manner sufficient to enable
a person skilled in the art to make and use the disclosed
embodiments. Several of the details and advantages described below,
however, may not be necessary to practice certain embodiments of
the invention. Additionally, the invention can also include
additional embodiments that are within the scope of the claims, but
are not described in detail with respect to FIGS. 2-16.
[0032] The operation and features of electrochemical reaction
vessels are best understood in light of the environment and
equipment in which they can be used to electrochemically process
workpieces (e.g., electroplate and/or electropolish). As such,
embodiments of integrated tools with processing stations having the
electrochemical reaction vessels are initially described with
reference to FIGS. 2 and 3 (Section A). The details and features of
several embodiments of electrochemical reaction vessels and methods
for mechanically controlling the electrochemical processing current
during processing are then described with reference to FIGS. 4-8B
(Section B). Further details of methods for electrically
controlling the current during electrochemical processing are
described with reference to FIGS. 9A-16 (Section C).
[0033] A. Selected Embodiments of Integrated Tools with
Electrochemical Processing Stations
[0034] FIG. 2 is an isometric view of a system, such a processing
machine 100, having an electrochemical processing station 120 in
accordance with an embodiment of the invention. A portion of the
processing machine 100 is shown in a cut-away view to illustrate
selected internal components. In one aspect of this embodiment, the
processing machine 100 includes a cabinet 102 having an interior
region 104 defining an interior enclosure that is at least
partially isolated from an exterior region 105. The cabinet 102
also includes a plurality of apertures 106 (only one shown in FIG.
1) through which microelectronic workpieces 101 can ingress and
egress between the interior region 104 and a load/unload station
110.
[0035] In one embodiment, the load/unload station 110 has two
container supports 112 that are each housed in a protective shroud
113. The container supports 112 are configured to position
workpiece containers 114 relative to the apertures 106 in the
cabinet 102. The workpiece containers 114 each house a plurality of
microelectronic workpieces 101 in a "mini" clean environment for
carrying a plurality of workpieces through other environments that
are not at clean room standards. Each of the workpiece containers
114 is accessible from the interior region 104 of the cabinet 102
through the apertures 106.
[0036] In one embodiment, the processing machine 100 also includes
a plurality of electrochemical processing stations 120 and a
transfer device 130 in the interior region 104 of the cabinet 102.
In one aspect of this embodiment, the processing machine 100 is a
plating tool that also includes clean/etch capsules 122,
electroless plating stations, annealing stations, and/or metrology
stations.
[0037] The transfer device 130 includes a linear track 132
extending in a lengthwise direction of the interior region 104
between the processing stations. In one aspect of this embodiment,
the transfer device 130 further includes a robot unit 134 carried
by the track 132. In the particular embodiment shown in FIG. 2, a
first set of processing stations is arranged along a first row
R.sub.1-R.sub.1 and a second set of processing stations is arranged
along a second row R.sub.2-R.sub.2. The linear track 132 extends
between the first and second rows of processing stations, and the
robot unit 134 can access any of the processing stations along the
track 132.
[0038] In a further aspect of this embodiment, the processing
machine 100 includes a controller 140 (such as a computer) that
coordinates the activities of the load/unload station 110, the
processing stations 120, and the transfer device 130. In a
particular embodiment, the controller 140 includes an input device
141 (such as a keyboard), a graphical user interface 142 (such as
an LCD screen) and a processor (not visible in FIG. 2). The
controller 140 also includes a computer operable medium, such as a
memory or a computer-readable medium (for example, a hard disk,
floppy disk or CD). In one embodiment, the computer operable medium
includes instructions for directing the operation of the
load/unload station 110 and the transfer device 130 to move
workpieces into and out of the processing stations 120. In one
aspect of this embodiment, the computer operable medium also
includes instructions for a controller 140 regulating the
electrical current(s) applied to the workpieces processed in the
processing stations 120, as described in greater detail below with
reference to FIGS. 9A-16.
[0039] FIG. 3 illustrates an embodiment of an
electrochemical-processing chamber 120 having a head assembly 150
and a processing chamber 200. The head assembly 150 includes a spin
motor 152, a rotor 154 coupled to the spin motor 152, and a contact
assembly 160 carried by the rotor 154. The rotor 154 can have a
backing plate 155 and a seal 156. The backing plate 155 can move
transverse to a workpiece 101 (arrow T) between a first position in
which the backing plate 155 contacts a backside of the workpiece
101 (shown in solid lines in FIG. 3) and a second position in which
it is spaced apart from the backside of the workpiece 101 (shown in
broken lines in FIG. 3). The contact assembly 160 can have a
support member 162, a plurality of contacts 164 carried by the
support member 162, and a plurality of shafts 166 extending between
the support member 162 and the rotor 154. The contacts 164 can be
ring-type spring contacts or other types of contacts that are
configured to engage a portion of the seed-layer on the workpiece
101. Commercially available head assemblies 150 and contact
assemblies 160 can be used in the electroprocessing chamber 120.
Particular suitable head assemblies 150 and contact assemblies 160
are disclosed in U.S. Pat. Nos. 6,228,232 and 6,080,691; and U.S.
application Ser. Nos. 09/385,784; 09/386,803; 09/386,610;
09/386,197; 09/501,002; 09/733,608; and 09/804,696, all of which
are herein incorporated by reference.
[0040] The processing chamber 200 includes an outer housing 202
(shown schematically in FIG. 3) and a reaction vessel 204 (also
shown schematically in FIG. 3) in the housing 202. The reaction
vessel 204 carries at least one electrode (not shown in FIG. 3) and
directs a flow of electroprocessing solution to the workpiece 101.
The electroprocessing solution, for example, can flow over a weir
(arrow F) and into the external housing 202, which captures the
electroprocessing solution and sends it back to a tank. Several
embodiments of reaction vessels 204 are shown and described in
detail with reference to FIGS. 4-8B.
[0041] In operation, the head assembly 150 holds the workpiece at a
workpiece-processing site of the reaction vessel 204 so that at
least a plating surface of the workpiece engages the
electroprocessing solution. An electrical field is established in
the solution by applying an electrical potential between the
plating surface of the workpiece via the contact assembly 160 and
one or more electrodes in the reaction vessel 204. For example, the
contact assembly 160 can be biased with a negative potential with
respect to the electrode(s) in the reaction vessel 204 to plate
materials onto the workpiece. On the other hand, the contact
assembly 160 can be biased with a positive potential with respect
to the electrode(s) in the reaction vessel 204 to (a) de-plate or
electropolish plated material from the workpiece or (b) deposit
other materials (e.g., electrophoretic resist). In general,
therefore, materials can be deposited on or removed from the
workpiece with the workpiece acting as a cathode or an anode
depending upon the particular type of material used in the
electrochemical process.
[0042] B. Selected Embodiments of Reaction Vessels for Use in
Electrochemical Processing Chambers
[0043] FIGS. 4-8B illustrate several embodiments of reaction
vessels 204 for use in the processing chamber 200. As explained
above, the housing 202 carries the reaction vessel 204. The housing
202 can have a drain 210 for returning the processing fluid that
flows out of the reaction vessel 204 to a storage tank, and a
plurality of openings for receiving inlets and electrical fittings.
The reaction vessel 204 can include an outer container 220 having
an outer wall 222 spaced radially inwardly of the housing 202. The
outer container 220 can also have a spiral spacer 224 between the
outer wall 222 and the housing 202 to provide a spiral ramp (i.e.,
a helix) on which the processing fluid can flow downward to the
bottom of the housing 202. The spiral ramp reduces the entrainment
of gasses in the return fluid.
[0044] The particular embodiment of the reaction vessel 204 shown
in FIG. 4 can include a distributor 300 for receiving a primary
fluid flow F.sub.p and a secondary fluid flow F.sub.2, a primary
flow guide 400 coupled to the distributor 300 to condition the
primary fluid flow F.sub.p, and a field shaping unit 500 coupled to
the distributor 300 to contain the secondary flow F.sub.2 in a
manner that shapes the electrical field in the reaction vessel 204.
The reaction vessel 204 can also include at least one electrode 600
in a compartment of the field shaping unit 500 and at least one
filter or other type of interface member 700 carried by the field
shaping unit 500 downstream from the electrode. The primary flow
guide 400 can condition the primary flow F.sub.p by projecting this
flow radially inwardly relative to a common axis A-A, and a portion
of the field shaping unit 500 directs the conditioned primary flow
F.sub.p toward the workpiece. In several embodiments, the primary
flow passing through the primary flow guide 400 and the center of
the field shaping unit 500 controls the mass transfer of processing
solution at the surface of the workpiece. The field shaping unit
500 also defines the shape the electric field, and it can influence
the mass transfer at the surface of the workpiece if the secondary
flow passes through the field shaping unit. The rate at which the
workpiece is rotated (typically from about 20 rpm to about 100 rpm)
can also be used to influence the mass transfer at the surface of
the workpiece.
[0045] The reaction vessel 204 can also have other configurations
of components to guide the primary flow F.sub.p and the secondary
flow F.sub.2 through the processing chamber 200. For example, in
one embodiment, the reaction vessel 204 includes a shield 580
having a central opening surrounded by a ring-shaped, solid portion
that at least limits contact between the fluid flow and the
peripheral region of the workpiece 101 (FIG. 3). In one aspect of
this embodiment, the shield 580 is removed entirely or replaced
with another shield having a larger or smaller central opening to
control the fluid flow passing adjacent to the peripheral region of
the workpiece 101 and to influence the electrical field in the
peripheral region. In a further aspect of this embodiment, the
vertical separation between the shield 580 and the workpiece 101 is
also adjusted to control the interaction between the fluid and the
workpiece 101. In one embodiment, the reaction vessel 204 also
includes a diffuser (generally similar to that shown in FIG. 1)
positioned in the fluid flow. The porosity/hole pattern of the
diffuser is selected to further control the interaction between the
fluid/electrical field and the workpiece 101.
[0046] In still further embodiments, the reaction vessel 204 has
other configurations. The reaction vessel 204, for example, may not
have a distributor in the processing chamber, but rather separate
fluid lines with individual flows can be coupled to the vessel 204
to provide a desired distribution of fluid through the primary flow
guide 400 and the field shaping unit. For example, the reaction
vessel 204 can have a first outlet in the outer container 220 for
introducing the primary flow into the reaction vessel and a second
outlet in the outer container for introducing the secondary flow
into the reaction vessel 204. Each of these components is explained
in more detail below.
[0047] FIGS. 5A-5D illustrate an embodiment of the distributor 300
for directing the primary fluid flow to the primary flow guide 400
and the secondary fluid flow to the field shaping unit 500.
Referring to FIG. 5A, the distributor 300 can include a body 310
having a plurality of annular steps 312 (identified individually by
reference numbers 312a-d) and annular grooves 314 in the steps 312.
The outermost step 312d is radially inward of the outer wall 222
(shown in broken lines) of the outer container 220 (FIG. 4), and
each of the interior steps 312a-c can carry an annular wall (shown
in broken lines) of the field shaping unit 500 in a corresponding
groove 314. The distributor 300 can also include a first inlet 320
for receiving the primary flow F.sub.p and a plenum 330 for
receiving the secondary flow F.sub.2. The first inlet 320 can have
an inclined, annular cavity 322 to form a passageway 324 (best
shown in FIG. 4) for directing the primary fluid flow F.sub.p under
the primary flow guide 400. The distributor 300 can also have a
plurality of upper orifices 332 along an upper part of the plenum
330 and a plurality of lower orifices 334 along a lower part of the
plenum 330. As explained in more detail below, the upper and lower
orifices are open to channels through the body 310 to distribute
the secondary flow F.sub.2 to the risers of the steps 312. The
distributor 300 can also have other configurations, such as a
"step-less" disk or non-circular shapes.
[0048] FIGS. 5A-5D further illustrate one configuration of channels
through the body 310 of the distributor 300. Referring to FIG. 5A,
a number of first channels 340 extend from some of the lower
orifices 334 to openings at the riser of the first step 312a. FIG.
5B shows a number of second channels 342 extending from the upper
orifices 332 to openings at the riser of the second step 312b, and
FIG. 5C shows a number of third channels 344 extending from the
upper orifices 332 to openings at the riser of the third step 312c.
Similarly, FIG. 5D illustrates a number of fourth channels 346
extending from the lower orifices 334 to the riser of the fourth
step 312d.
[0049] The particular embodiment of the channels 340-346 in FIGS.
5A-5D are configured to transport bubbles that collect in the
plenum 330 radially outward as far as practical so that these
bubbles can be captured and removed from the secondary flow
F.sub.2. This is beneficial because the field shaping unit 500
removes bubbles from the secondary flow F.sub.2 by sequentially
transporting the bubbles radially outwardly through electrode
compartments. For example, a bubble B in the compartment above the
first step 312a can sequentially cascade through the compartments
over the second and third steps 312b-c, and then be removed from
the compartment above the fourth step 312d. The first channel 340
(FIG. 5A) accordingly carries fluid from the lower orifices 334
where bubbles are less likely to collect to reduce the amount of
gas that needs to cascade from the inner compartment above the
first step 312a all the way out to the outer compartment. The
bubbles in the secondary flow F.sub.2 are more likely to collect at
the top of the plenum 330 before passing through the channels
340-346. The upper orifices 332 are accordingly coupled to the
second channel 342 and the third channel 344 to deliver these
bubbles outward beyond the first step 312a so that they do not need
to cascade through so many compartments. In this embodiment, the
upper orifices 332 are not connected to the fourth channels 346
because this would create a channel that inclines downwardly from
the common axis such that it may conflict with the groove 314 in
the third step 312c. Thus, the fourth channel 346 extends from the
lower orifices 334 to the fourth step 312d.
[0050] Referring again to FIG. 4, the primary flow guide 400
receives the primary fluid flow F.sub.p via the first inlet 320 of
the distributor 300. In one embodiment, the primary flow guide 400
includes an inner baffle 410 and an outer baffle 420. The inner
baffle can have a base 412 and a wall 414 projecting upward and
radially outward from the base 412. The wall 414, for example, can
have an inverted frusto-conical shape and a plurality of apertures
416. The apertures 416 can be holes, elongated slots or other types
of openings. In the illustrated embodiment, the apertures 416 are
annularly extending radial slots that slant upward relative to the
common axis to project the primary flow radially inward and upward
relative to the common axis along a plurality of diametrically
opposed vectors. The inner baffle 410 can also includes a locking
member 418 that couples the inner baffle 410 to the distributor
300.
[0051] The outer baffle 420 can include an outer wall 422 with a
plurality of apertures 424. In this embodiment, the apertures 424
are elongated slots extending in a direction transverse to the
apertures 416 of the inner baffle 410. The primary flow F.sub.p
flows through (a) the first inlet 320, (b) the passageway 324 under
the base 412 of the inner baffle 410, (c) the apertures 424 of the
outer baffle 420, and then (d) the apertures 416 of the inner
baffle 410. The combination of the outer baffle 420 and the inner
baffle 410 conditions the direction of the flow at the exit of the
apertures 416 in the inner baffle 410. The primary flow guide 400
can thus project the primary flow along diametrically opposed
vectors that are inclined upward relative to the common axis to
create a fluid flow that has a highly uniform velocity. In
alternate embodiments, the apertures 416 do not slant upward
relative to the common axis such that they can project the primary
flow normal, or even downward, relative to the common axis.
[0052] FIG. 4 also illustrates an embodiment of the field shaping
unit 500 that receives the primary fluid flow F.sub.p downstream
from the primary flow guide 400. The field shaping unit 500 also
contains the second fluid flow F.sub.2 and shapes the electrical
field within the reaction vessel 204. In this embodiment, the field
shaping unit 500 has a compartment structure with a plurality of
walls 510 (identified individually by reference numbers 510a-d)
that define electrode compartments 520 (identified individually by
reference numbers 520a-d). The walls 510 can be annular skirts or
dividers, and they can be received in one of the annular grooves
314 in the distributor 300. In one embodiment, the walls 510 are
not fixed to the distributor 300 so that the field shaping unit 500
can be quickly removed from the distributor 300. This allows easy
access to the electrode compartments 520 and/or quick removal of
the field shaping unit 500 to change the shape of the electric
field.
[0053] The field shaping unit 500 can have at least one wall 510
outward from the primary flow guide 400 to prevent the primary flow
F.sub.p from contacting an electrode. In the particular embodiment
shown in FIG. 4, the field shaping unit 500 has a first electrode
compartment 520a defined by a first wall 510a and a second wall
510b, a second electrode compartment 520b defined by the second
wall 510b and a third wall 510c, a third electrode compartment 520c
defined by the third wall 510c and a fourth wall 510d, and a fourth
electrode compartment 520d defined by the fourth wall 510d and the
outer wall 222 of the container 220. The walls 510a-d of this
embodiment are concentric annular dividers that define annular
electrode compartments 520a-d. Alternate embodiments of the field
shaping unit can have walls with different configurations to create
non-annular electrode compartments and/or each electrode
compartment can be further divided into cells. The second-fourth
walls 510b-d can also include holes 522 for allowing bubbles in the
first-third electrode compartments 520a-c to "cascade" radially
outward to the next outward electrode compartment 520 as explained
above with respect to FIGS. 5A-5D. The bubbles can then exit the
fourth electrode compartment 520d through an exit hole 525 through
the outer wall 222. In an alternate embodiment, the bubbles can
exit through an exit hole 524.
[0054] The electrode compartments 520 provide electrically discrete
compartments to house an electrode assembly having at least one
electrode and generally two or more electrodes 600 (identified
individually by reference numbers 600a-d). The electrodes 600 can
be annular members (e.g., annular rings or arcuate sections) that
are configured to fit within annular electrode compartments, or
they can have other shapes appropriate for the particular workpiece
(e.g., rectilinear). In the illustrated embodiment, for example,
the electrode assembly includes a first annular electrode 600a in
the first electrode compartment 520a, a second annular electrode
600b in the second electrode compartment 520b, a third annular
electrode 600c in the third electrode compartment 520c, and a
fourth annular electrode 600d in the fourth electrode compartment
520d. As explained in U.S. application Ser. Nos. 60/206,661,
09/845,505, and 09/804,697, all of which are incorporated herein by
reference, each of the electrodes 600a-d can be biased with the
same or different potentials with respect to the workpiece to
control the current density across the surface of the workpiece. In
alternate embodiments, the electrodes 600 can be non-circular
shapes or sections of other shapes.
[0055] The field shaping unit 500 can also include a virtual
electrode unit coupled to the walls 510 of the compartment assembly
for individually shaping the electrical fields produced by the
electrodes 600. In the particular embodiment illustrated in FIG. 4,
the virtual electrode unit includes first-fourth partitions
530a-530d, respectively. The first partition 530a can have a first
section 532a coupled to the second wall 510b, a skirt 534 depending
downward above the first wall 510a, and a lip 536a projecting
upwardly. The lip 536a has an interior surface 537 that directs the
primary flow F.sub.p exiting from the primary flow guide 400. The
second partition 530b can have a first section 532b coupled to the
third wall 510c and a lip 536b projecting upward from the first
section 532b, the third partition 530c can have a first section
532c coupled to the fourth wall 510d and a lip 536c projecting
upward from the first section 532c, and the fourth partition 530d
can have a first section 532d carried by the outer wall 222 of the
container 220 and a lip 536d projecting upward from the first
section 532d. The fourth partition 530d may not be connected to the
outer wall 222 so that the field shaping unit 500 can be quickly
removed from the vessel 204 by simply lifting the virtual electrode
unit. The interface between the fourth partition 530d and the outer
wall 222 is sealed by a seal 527 to inhibit both the fluid and the
electrical current from leaking out of the fourth electrode
compartment 520d. The seal 527 can be a lip seal. Additionally,
each of the sections 532a-d can be lateral sections extending
transverse to the common axis.
[0056] The individual partitions 530a-d can be machined from or
molded into a single piece of dielectric material, or they can be
individual dielectric members that are welded together. In
alternate embodiments, the individual partitions 530a-d are not
attached to each other and/or they can have different
configurations. In the particular embodiment shown in FIG. 4, the
partitions 530a-d are annular horizontal members, and each of the
lips 536a-d are annular vertical members arranged concentrically
about the common axis.
[0057] The walls 510 and the partitions 530a-d are generally
dielectric materials that contain the second flow F.sub.2 of the
processing solution for shaping the electric fields generated by
the electrodes 600a-d. The second flow F.sub.2, for example, can
pass (a) through each of the electrode compartments 520a-d, (b)
between the individual partitions 530a-d, and then (c) upward
through the annular openings between the lips 536a-d. In this
embodiment, the secondary flow F.sub.2 through the first electrode
compartment 520a can join the primary flow F.sub.p in an
antechamber just before the primary flow guide 400, and the
secondary flow through the second-fourth electrode compartments
520b-d can join the primary flow F.sub.p beyond the top edges of
the lips 536a-d. The flow of electroprocessing solution then flows
over a shield weir attached at rim 538 and into the gap between the
housing 202 and the outer wall 222 of the container 220 as
disclosed in International Application No. PCT/US00/10120,
incorporated herein by reference. The fluid in the secondary flow
F.sub.2 can be prevented from flowing out of the electrode
compartments 520a-d to join the primary flow F.sub.p while still
allowing electrical current to pass from the electrodes 600 to the
primary flow. In this alternate embodiment, the secondary flow
F.sub.2 can exit the reaction vessel 204 through the holes 522 in
the walls 510 and the hole 525 in the outer wall 222. In still
additional embodiments in which the fluid of the secondary flow
does not join the primary flow, a duct can be coupled to the exit
hole 525 in the outer wall 222 so that a return flow of the
secondary flow passing out of the field shaping unit 500 does not
mix with the return flow of the primary flow passing down the
spiral ramp outside of the outer wall 222.The field shaping unit
500 can have other configurations that are different than the
embodiment shown in FIG. 4. For example, the electrode compartment
assembly can have only a single wall 510 defining a single
electrode compartment 520, and the reaction vessel 204 can include
only a single electrode 600. The field shaping unit of either
embodiment still separates the primary and secondary flows so that
the primary flow does not engage the electrode, and thus it shields
the workpiece from the single electrode. One advantage of shielding
the workpiece from the electrodes 600a-d is that the electrodes can
accordingly be much larger than they could be without the field
shaping unit because the size of the electrodes does not have an
effect on the electrical field presented to the workpiece. This is
particularly useful in situations that use consumable electrodes
because increasing the size of the electrodes prolongs the life of
each electrode, which reduces downtime for servicing and replacing
electrodes.
[0058] An embodiment of reaction vessel 204 shown in FIG. 4 can
accordingly have a first conduit system for conditioning and
directing the primary fluid flow F.sub.p to the workpiece, and a
second conduit system for conditioning and directing the secondary
fluid flow F.sub.2. The first conduit system, for example, can
include the inlet 320 of the distributor 300; the channel 324
between the base 412 of the primary flow guide 400 and the inclined
cavity 322 of the distributor 300; a plenum between the wall 422 of
the outer baffle 420 and the first wall 510a of the field shaping
unit 500; the primary flow guide 400; and the interior surface 537
of the first lip 536a. The first conduit system conditions the
direction of the primary fluid flow F.sub.p by passing it through
the primary flow guide 400 and along the interior surface 537 so
that the velocity of the primary flow F.sub.p normal to the
workpiece is at least substantially uniform across the surface of
the workpiece. The primary flow F.sub.p and the rotation of the
workpiece can accordingly be controlled to influence the mass
transfer of electroprocessing medium at the workpiece.
[0059] The second conduit system, for example, can include the
plenum 330 and the channels 340-346 of the distributor 300, the
walls 510 of the field shaping unit 500, and the partitions 530 of
the field shaping unit 500. The secondary flow F.sub.2 contacts the
electrodes 600 to establish individual electrical fields in the
field shaping unit 500 that are electrically coupled to the primary
flow F.sub.p. The field shaping unit 500, for example, separates
the individual electrical fields created by the electrodes 600a-d
to create "virtual electrodes" at the top of the openings defined
by the lips 536a-d of the partitions. In this particular
embodiment, the central opening inside the first lip 536a defines a
first virtual electrode, the annular opening between the first and
second lips 536a-b defines a second virtual electrode, the annular
opening between the second and third lips 536b-c defines a third
virtual electrode, and the annular opening between the third and
fourth lips 536c-d defines a fourth virtual electrode. These are
"virtual electrodes" because the field shaping unit 500 shapes the
individual electrical fields of the actual electrodes 600a-d so
that the effect of the electrodes 600a-d acts as if they are placed
between the top edges of the lips 536a-d. This allows the actual
electrodes 600a-d to be isolated from the primary fluid flow, which
can provide several benefits as explained in more detail below.
[0060] An additional embodiment of the processing chamber 200
includes at least one interface member 700 (identified individually
by reference numbers 700a-d) for further conditioning the secondary
flow F.sub.2 of electroprocessing solution. The interface members
700, for example, can be filters that capture particles in the
secondary flow that were generated by the electrodes (i.e., anodes)
or other sources of particles. The filter-type interface members
700 can also inhibit bubbles in the secondary flow F.sub.2 from
passing into the primary flow F.sub.p of electroprocessing
solution. This effectively forces the bubbles to pass radially
outwardly through the holes 522 in the walls 510 of the field
shaping unit 500. In alternate embodiments, the interface members
700 can be ion-membranes that allow ions in the secondary flow
F.sub.2 to pass through the interface members 700. The ion-membrane
interface members 700 can be selected to (a) allow the fluid of the
electroprocessing solution and ions to pass through the interface
member 700, or (b) allow only the desired ions to pass through the
interface member such that the fluid itself is prevented from
passing beyond the ion-membrane.
[0061] FIG. 6 is another isometric view of the reaction vessel 204
of FIG. 4 showing a cross-sectional portion taken along a different
cross-section. More specifically, the cross-section of FIG. 4 is
shown in FIG. 8A and the cross-section of FIG. 6 is shown in FIG.
8B. Returning now to FIG. 6, this illustration further shows one
embodiment for configuring a plurality of interface members 700a-d
relative to the partitions 530a-d of the field shaping unit 500. A
first interface member 700a can be attached to the skirt 534 of the
first partition 530a so that a first portion of the secondary flow
F.sub.2 flows past the first electrode 600a, through an opening 535
in the skirt 534, and then to the first interface member 700a.
Another portion of the secondary flow F.sub.2 can flow past the
second electrode 600b to the second interface member 700b.
Similarly, portions of the secondary flow F.sub.2 can flow past the
third and fourth electrodes 600c-d to the third and fourth
interface members 700c-d.
[0062] When the interface members 700a-d are filters or
ion-membranes that allow the fluid in the secondary flow F.sub.2 to
pass through the interface members 700a-d, the secondary flow
F.sub.2 joins the primary fluid flow Fp. The portion of the
secondary flow F.sub.2 in the first electrode compartment 520a can
pass through the opening 535 in the skirt 534 and the first
interface member 700a, and then into a plenum between the first
wall 510a and the outer wall 422 of the baffle 420. This portion of
the secondary flow F.sub.2 accordingly joins the primary flow
F.sub.p and passes through the primary flow guide 400. The other
portions of the secondary flow F.sub.2 in this particular
embodiment pass through the second-fourth electrode compartments
520b-d and then through the annular openings between the lips
536a-d. The second-fourth interface members 700b-d can accordingly
be attached to the field shaping unit 500 downstream from the
second-fourth electrodes 600b-d.
[0063] In the particular embodiment shown in FIG. 6, the second
interface member 700b is positioned vertically between the first
and second partitions 530a-b, the third interface member 700c is
positioned vertically between the second and third partitions
530b-c, and the fourth interface member 700d is positioned
vertically between the third and fourth partitions 530c-d. The
interface assemblies 710a-d are generally installed vertically, or
at least at an upwardly inclined angle relative to horizontal, to
force the bubbles to rise so that they can escape through the holes
522 in the walls 510a-d (FIG. 4). This prevents aggregations of
bubbles that could potentially disrupt the electrical field from an
individual electrode.
[0064] FIGS. 7A and 7B illustrate an interface assembly 710 for
mounting the interface members 700 to the field shaping unit 500 in
accordance with an embodiment of the invention. The interface
assembly 710 can include an annular interface member 700 and a
fixture 720 for holding the interface member 700. The fixture 720
can include a first frame 730 having a plurality of openings 732
and a second frame 740 having a plurality of openings 742 (best
shown in FIG. 7A). The holes 732 in the first frame can be aligned
with the holes 742 in the second frame 740. The second frame can
further include a plurality of annular teeth 744 extending around
the perimeter of the second frame. It will be appreciated that the
teeth 744 can alternatively extend in a different direction on the
exterior surface of the second frame 740 in other embodiments, but
the teeth 744 generally extend around the perimeter of the second
frame 740 in a top annular band and a lower annular band to provide
annular seals with the partitions 536a-d (FIG. 6). The interface
member 700 can be pressed between the first frame 730 and the
second frame 740 to securely hold the interface member 700 in
place. The interface assembly 710 can also include a top band 750a
extending around the top of the frames 730 and 740 and a bottom
band 750b extending around the bottom of the frames 730 and 740.
The top and bottom bands 750a-b can be welded to the frames 730 and
740 by annular welds 752. Additionally, the first and second frames
730 and 740 can be welded to each other by welds 754. It will be
appreciated that the interface assembly 710 can have several
different embodiments that are defined by the configuration of the
field shaping unit 500 (FIG. 6) and the particular configuration of
the electrode compartments 520a-d (FIG. 6).
[0065] When the interface member 700 is a filter material that
allows the secondary flow F.sub.2 of electroprocessing solution to
pass through the holes 732 in the first frame 730, the
post-filtered portion of the solution continues along a path (arrow
Q) to join the primary fluid flow F.sub.p as described above. One
suitable material for a filter-type interface member 700 is
POREX.RTM., which is a porous plastic that filters particles to
prevent them from passing through the interface member. In plating
systems that use consumable anodes (e.g., phosphorized copper or
nickel sulfamate), the interface member 700 can prevent the
particles generated by the anodes from reaching the plating surface
of the workpiece.
[0066] In alternate embodiments in which the interface member 700
is an ion-membrane, the interface member 700 can be permeable to
preferred ions to allow these ions to pass through the interface
member 700 and into the primary fluid flow F.sub.p. One suitable
ion-membrane is NAFION.RTM. perfluorinated membranes manufactured
by DuPont.RTM.. Other suitable types of ion-membranes for plating
can be polymers that are permeable to many cations, but reject
anions and non-polar species. It will be appreciated that in
electropolishing applications, the interface member 700 may be
selected to be permeable to anions, but reject cations and
non-polar species. The preferred ions can be transferred through
the ion-membrane interface member 700 by a driving force, such as a
difference in concentration of ions on either side of the membrane,
a difference in electrical potential, or hydrostatic pressure.
[0067] Using an ion-membrane that prevents the fluid of the
electroprocessing solution from passing through the interface
member 700 allows the electrical current to pass through the
interface member while filtering out particles, organic additives
and bubbles in the fluid. For example, in plating applications in
which the interface member 700 is permeable to cations, the primary
fluid flow F.sub.p can be a catholyte and the secondary fluid flow
F.sub.2 can be a separate anolyte because these fluids do not mix
in this embodiment. A benefit of having separate anolyte and
catholyte fluid flows is that it eliminates the consumption of
additives at the anodes and thus the need to replenish the
additives as often. Additionally, this feature combined with the
"virtual electrode" aspect of the reaction vessel 204 reduces the
need to "burn-in" anodes for insuring a consistent black film over
the anodes for predictable current distribution because the current
distribution is controlled by the configuration of the field
shaping unit 500. Another advantage is that it also eliminates the
need to have a predictable consumption of additives in the
secondary flow F.sub.2 because the additives to the secondary flow
F.sub.2 do not effect the primary fluid flow F.sub.p when the two
fluids are separated from each other.
[0068] In another embodiment, the geometry of the reaction vessel
204 described above with reference to FIGS. 3-8B is adjusted as the
microelectronic workpiece 101 is processed to actively control the
current distribution at the microelectronic workpiece 101 as a
function of time. For example, in one aspect of this embodiment,
the distance between the microelectronic workpiece 101 and the
electrodes 600a-d and/or the shield 580 is adjusted while current
is passing through the electroprocessing fluid. The distance is
changed by moving the microelectronic workpiece 101, the electrodes
600a-d, and/or the shield 580 toward and away from each other.
[0069] In other embodiments, other methods are used to adjust the
geometry of the reaction vessel 204 during proessing. For example,
in one embodiment, the shield 580 (FIG. 4) has an adjustable
diaphragm arrangement in which the central opening can change
diameter, much like the aperture of a camera. In another
embodiment, the distance between the shield 580 and the
microelectronic workpiece 101 is adjusted by moving the shield 580
and/or the microelectronic workpiece 101 toward and/or away from
each other. For example, the shielding provided to the periphery of
the microelectronic workpiece 101 can be reduced during processing
by increasing the distance between the workpiece 101 and the shield
580. In yet another embodiment, the openings in the diffuser
(positioned between the electrodes 600a-d and the microelectronic
workpiece 101) are each individually adjustable to change the flow
distribution and/or the overall flow rate of electroprocessing
fluid. For example, peripheral openings in the diffuser can be
selectively closed or opened to increase or decrease, respectively,
the shielding provided to the peripheral region of the workpiece
101. In still further embodiments, the geometry of the reaction
vessel is altered during processing by other methods and/or
mechanisms.
[0070] In any of the foregoing embodiments, mechanical changes to
the geometry of the reaction vessel 204 change the distribution of
current at the microelectronic workpiece 101 during processing. In
other embodiments, described below in Section C, the current
distribution is changed by changing the current applied to the
electrodes 600a-d. The effects of actively changing the current
distribution during processing, by mechanical and/or electrical
techniques, are also described in greater detail below in Section
C.
[0071] C. Method of Selecting and Applying Electrical Currents to
Electrodes in Reaction Vessels
[0072] FIGS. 9A-9D illustrate processes that can be completed with
the apparatuses described above with reference to FIGS. 2-8B by
selectively adjusting the currents applied to multiple electrodes
in processing chambers, for example, to adjust the current
distribution in the electrolytic fluid within the processing
chambers. For example, FIG. 9A illustrates a process 900 that
includes contacting a microelectronic workpiece with an
electrolytic fluid (process portion 901) and positioning a
plurality of electrodes in electrical communication with the
electrolytic fluid (process portion 902). The process 900 can
further include directing a plurality of electrical currents
through the plurality of electrodes and changing at least one of
the currents in a selected manner during the process. For example,
a current ratio of at least one of the electrical currents to a sum
of all of the electrical currents can initially have a first
current ratio value (process portion 903). In process portion 904,
the current ratio is changed from the first current ratio value to
a second current ratio value, and the at least one electrical
current is directed at the second current ratio value through one
of the electrodes.
[0073] In one embodiment, the current ratio is adjusted between at
least two electrodes, and in another embodiment, the current ratio
is adjusted over four electrodes. In a further embodiment, the
current ratio is adjusted to maintain a current density across the
workpiece that varies by less than ten percent of the 3-.sigma.
deviation level of a standard distribution curve. In other
embodiments, the variation is less than five percent of the
3-.sigma. level. In yet a further embodiment, the first current
ratio value is used while features in a conductive layer of the
workpiece are filled, and the second current ratio value is used
while a blanket layer is applied to the filled features.
[0074] In another embodiment, the current distribution over a
plurality of electrodes is adjusted to account for different
electrolytic fluids having different conductivities. For example,
as shown in FIG. 9B, a process 910 includes contacting a first
microelectronic workpiece with a first electrolytic fluid having a
first conductivity (process portion 911) and positioning a
plurality of electrodes in electrical communication with the first
microelectronic workpiece (process portion 912). An embodiment of
the process 910 further includes directing a plurality of first
electrical currents through the plurality of electrodes, with a
first current distribution as a function of electrode position
(process portion 913). In process portion 914, a second
microelectronic workpiece is placed in contact with a second
electrolytic fluid having a second conductivity different than the
first conductivity. The process 910 further includes positioning
the plurality of electrodes in electrical communication with the
second microelectronic workpiece (process portion 915) and
directing a plurality of second electrical currents through the
plurality of electrodes, with a second current distribution as a
function of electrode position (process portion 916).
[0075] In other embodiments, the current applied to the electrodes
is used to remove conductive material from the workpiece, and/or
thieve conductive material that would otherwise attach to the
workpiece. For example, as shown in FIG. 9C, a process 920 includes
contacting a microelectronic workpiece with an electrolytic fluid
(process portion 921), removing conductive material from an outer
region of a conductive layer of the workpiece (process portion
922), and then simultaneously adding conductive material to both
the inner and outer regions of the conductive layer (process
portion 923). In another embodiment, shown in FIG. 9D, a process
930 includes contacting the workpiece with an electrolytic fluid
(process portion 931) and directing conductive material from a
first electrode toward the microelectronic workpiece (process
portion 932). The process 930 further includes attracting to a
second electrode at least a portion of the conductive material in
the electrolytic fluid that would otherwise attach to the
workpiece, while adding at least a portion of the conductive
material to an inner region of the workpiece (process portion 933).
In one aspect of this embodiment, the process 930 further includes
changing a current applied to the first electrode as a function of
time (process portion 934) and then simultaneously adding
conductive material to both the inner region and the outer region
of the workpiece (process portion 935).
[0076] FIGS. 10A-16 illustrate analytical predictions and
experimental results for plating conductive materials on
microelectronic workpieces in accordance with several embodiments
of the invention that can use multi-electrode processing chambers
generally similar to those described above with reference to FIGS.
2-8. The examples described below relate to plating copper blanket
layers on copper seed layers, but are also applicable to other
materials and other plating operations. The methods are further
applicable to material removal processes.
[0077] FIG. 10A illustrates a table of predicted current levels for
each of four electrodes 600a-d (FIG. 4) as a function of initial
seed layer thickness for a 200 mm workpiece. The predicted current
levels are selected to produce a total current in each case of
about 6.5 amps, and an instantaneously uniform current density
(i.e., a uniform current per square centimeter of workpiece surface
area) across the workpiece 101 (FIG. 3). Also shown in FIG. 10A for
each initial seed layer thickness is the percentage of the total
current applied to the workpiece 101 contributed by each electrode.
FIG. 10B is a graphical illustration of the current levels for each
electrode as a function of the initial seed layer thickness.
[0078] Referring now to FIGS. 10A and 10B, the percentage of the
total current applied to the inner three electrodes (600a-c) tends
to drop as the initial seed layer thickness increases. The
percentage of the total current applied to the outermost electrode
(600d) tends to increase as the initial seed layer thickness
increases. It is believed that this result is due to the decreasing
significance of the terminal effect as the seed layer thickness
increases. For example, compared to a thick seed layer, a
relatively thin seed layer will have a higher resistivity and
accordingly electrical current will be concentrated near the
contacts around the periphery of the workpiece 101. This will
result in higher plating rates near the contacts than at the center
of thin seed layers. Thus, the current applied to the outermost
electrode can be lower than that applied to the inner electrodes to
counteract the terminal effect If the seed layer is relatively
thick, it will have a lower resistivity, and, all other variables
being equal, the current density will tend to be more uniform over
the surface of the workpiece 101. Accordingly, FIGS. 10A and 10B
indicate that by changing the percentage of the current passing
through each electrode as the seed layer thickens, a uniform
current density over the surface of the workpiece 101 is
obtained.
[0079] The results described above with reference to FIGS. 10A and
10B are somewhat simplified from an actual deposition process in
that different starting seed layer thicknesses are used to simulate
a buildup of conductive material on a given seed layer. For
example, the predicted current levels for a 3,000 .ANG. seed layer
provide an indication of the current levels that would be required
after 2,400 .ANG. of conductive material have been built up on a
600 .ANG. seed layer. This is somewhat simplified from the actual
case in that slight non-uniformities that may tend to form during
each step of the deposition process may not be accounted for. FIG.
11, described below, illustrates predicted results that account for
at least a portion of this simplification.
[0080] FIG. 11 illustrates predicted current levels as a function
of time applied to each of four electrodes 600a-d in a process that
begins with a 1000 .ANG. thick seed layer on a 300 mm workpiece,
and ends with a 1 micron thick blanket layer. The current levels
applied to each electrode 600a-d change in six discrete stages. As
expected, (based on the results of FIGS. 10A and 10B) the current
applied to the innermost electrode 600a tends to decrease over time
and the current applied to the outermost electrode 600d tends to
increase over time. The predicted current applied to the third
electrode 600c tends to decrease over time, and the predicted
current applied to the second electrode 600b tends to increase
slightly over time. These results may be due to the effects
neighboring electrodes have on each other, which may be more
accurately predicted by simulating an entire deposition process on
a single seed layer (as shown in FIG. 11) than by simulating the
deposition process by assuming a series of separate processes, each
starting with a thicker initial seed layer (as shown in FIGS. 10A
and 10B).
[0081] FIG. 12 illustrates the predicted film non-uniformity as a
function of film thickness for a six-stage process in accordance
with an embodiment of the invention (line 1200) compared with an
existing single-stage process optimized for uniform current density
at a film thickness of 1 micron. The predictions are for a total
current of 15 amps transmitted through an electrolytic solution
having a conductivity of 511 millisiemens per centimeter (mS/cm).
In this prediction, the shield 580 (FIG. 4) has an inner diameter
of 290 mm and is positioned 11 mm beneath the workpiece 101. The
workpiece has an initial seed layer thickness of 1,000 .ANG.. The
non-uniformity is indicated as a percentage of the 3-.sigma.
deviation level of a standard distribution curve ("% 3-.sigma.").
In other embodiments, the total current changes with time, the
conductivity has other values, and/or the shield 580 has different
arrangements.
[0082] As shown in FIG. 12, the multi-stage process indicated by
line 1200 produces an applied film that is significantly more
uniform than that resulting from the single-stage process indicated
by line 1201, at all thicknesses other than about one micron. For
example, in one embodiment, the multi-stage process produces an
applied layer having a uniformity of 10% of 3-.sigma. or better. In
another embodiment, the uniformity is 5% of 3-.sigma. or better. As
is also shown in FIG. 12, the single-stage process produces an
optimally uniform film at only one point (about 1 micron). This is
because the single-stage process tends to overplate the edge of the
workpiece 101 in the beginning of the process (due to the terminal
effect) and underplate the edge of the workpiece 101 toward the end
of the process (to account for the earlier overplating). If the
process continues beyond the design point (e.g., beyond about 1
micron), the single-stage process will continue to underplate the
edge of the workpiece 101, resulting in an increasingly non-uniform
conductive layer. By contrast, the multi-stage process tends to
produce a uniform layer at all phases of the process, and can
accordingly continue beyond the design point without a substantial
increase in non-uniformity.
[0083] FIG. 13 illustrates predicted current densities as a
function of workpiece radius at several points in time during an
embodiment of the multi-stage process described above with
reference to FIGS. 11 and 12. As shown in FIG. 13, the current
density is generally uniform (at a level of from about 20.5
mA/cm.sup.2 to about 21 mA/cm.sup.2) from the center of the
workpiece 101 to a radius of about 125 mm for all phases of the
process. At the outer periphery of the workpiece 101, the current
density varies between about 19.5 mA/cm.sup.2 to about 21.5
mA/cm.sup.2 over the course of the process. Accordingly, the
current density variation over the entire workpiece 101 is about 2
mA/cm.sup.2 (21.5 mA/cm.sup.2 minus 19.5 mA/cm.sup.2).
[0084] By way of comparison, FIG. 14 illustrates predicted current
densities as a function of workpiece radius for an existing
single-stage process, at the same points in time shown in FIG. 13.
As is seen in FIG. 14, the existing single-stage process produces a
significantly less uniform current density distribution than does
an embodiment of the multi-stage process described above with
reference to FIG. 13. For example, the current density over the
inner 125 mm of the workpiece 101 varies from about 17 mA/cm.sup.2
to about 21.75 mA/cm.sup.2. The current density over the outer 25
mm of the workpiece 101 varies from about 19.5 mA/cm.sup.2 to about
27 mA/cm.sup.2. Accordingly, the current density variation over the
entire workpiece is about 10 mA/cm.sup.2 (27 mA/cm.sup.2 minus 17
mA/cm.sup.2), significantly greater than the 2 mA/cm.sup.2
variation described above with reference to FIG. 13.
[0085] One feature of an embodiment of a process described above
with reference to FIGS. 10A-13 is that the current passing through
each electrode (and/or the percentage of the total current
contributed by each electrode) changes during the process. An
advantage of this arrangement is that the local current density at
each point on the workpiece is more uniform throughout the course
of the process. As a result, the layer of conductive material
applied to the microelectronic workpiece 101 is also more uniform
at all times. This advantage can have increasing significance as
the features that are filled by the conductive material decrease in
size. For example, while existing processes may produce a blanket
layer that is uniform at its target thickness (e.g., at 1 micron,
as indicated by line 1201 shown in FIG. 12), the non-uniform
plating rate during earlier phases of the process may have
significant drawbacks. In particular, the electrolytic solution may
include additives or other chemicals that promote uniform film
growth, but that operate best at selected current densities and/or
material application rates. By keeping the current density uniform
over the surface of the workpiece 101 throughout the process, a
method in accordance with an embodiment of the invention increases
the likelihood that these additives perform well, and reduces the
likelihood that non-uniformities form in the conductive material
applied to the workpiece 101. The performance of the additives
generally becomes more important as the size of the features
decreases and the aspect ratio of the features increases.
[0086] FIGS. 11-13 (described above) illustrate six-stage processes
for producing uniform blanket layers on generally uniform seed
layers. In other embodiments, the process can have other numbers of
stages, other starting seed layer shapes and/or other blanket layer
shapes. For example, FIG. 15 illustrates experimental results for a
two-stage process that operates on an initially domed seed layer
(represented by line 1501). The data shown in FIG. 15 are
normalized to the average thickness at each stage of the process.
During a first stage of the process, features in the seed layer are
filled to produce the profile represented by line 1502. Because the
shape of line 1502 is similar to that of line 1501, the current
density was uniform during the first stage of the process. During a
second stage of the process, material is applied to the filled seed
layer with the current applied to at least one of the electrodes
changed from the level applied during the first stage. At the end
of the second stage, the applied layer has a generally uniform
thickness, as represented by line 1503.
[0087] In another embodiment, shown in FIG. 16, the workpiece has
an initially generally flat seed layer profile (indicated by line
1601). The target profile for the blanket layer is indicated by
line 1602 and has a generally concave distribution. Line 1603
indicates an actual profile produced using a three-stage process
and an apparatus generally similar to that described above with
reference to FIGS. 2-8. In one aspect of this embodiment, the
current was applied to the electrodes according to a first
distribution during a first stage of the process. The current was
changed to a non-DC application after the features of the seed
layer were filled (during a second stage of the process), and
distribution of the current to the electrodes was changed prior to
a third, bulk fill stage of the process.
[0088] In other embodiments, multi-stage processes are used to
apply material to a variety of different types of seed layers (or
other layers or features), to produce a variety of different types
of blanket layers (or other layers or features). For example, in
one embodiment, multi-stage processes apply material at a generally
uniform current density to a generally uniform seed layer, or a
concave seed layer, or a convex seed layer, to produce any of a
generally uniform blanket layer, a concave blanket layer, or a
convex blanket layer.
[0089] In other embodiments, other characteristics of the material
application process are controlled in conjunction with controlling
the current applied to each of the electrodes to provide increased
control over the resulting applied conductive layers. For example,
in one embodiment the size of the opening in the shield 580 (FIG.
4) is adjusted to control the electrical field and/or the
interaction between the electrolytic fluid and the peripheral
region of the microelectronic workpiece. In another embodiment, the
spacing between the shield 580 and the microelectronic workpiece is
adjusted. In still further embodiments, the configuration and/or
position of a diffuser in the electrolytic fluid is adjusted to
control the electrical field proximate to the microelectronic
workpiece, and/or the interaction between the fluid and the
microelectronic workpiece.
[0090] In yet a further embodiment, the conductivity of the
electrolytic solution in which the microelectronic workpiece is
positioned is adjusted and, in one embodiment, has a value of
between about 5 mS/cm and about 500 mS/cm. In other embodiments,
the conductivity of the electrolytic fluid has values above or
below this range. In one particular embodiment, the distribution of
current applied to the electrodes is adjusted as a function of the
conductivity of the bath. Accordingly, the distribution of the
total current applied to the electrodes is different when the bath
has a low conductivity than when the bath has a high conductivity.
An advantage of this process is that the same processing chamber
and electrode arrangement is suitable for use with electrolytic
fluids having a variety of conductivities (with or without changing
the hardware of the processing chamber) to process different types
of workpieces. For example, some workpieces (in particular, those
with very thin starting seed layers) may accumulate additional
conductive material more uniformly when in contact with low
conductivity electrolytic fluids, while the same or other
workpieces may benefit from subsequent process stages that produce
better results when the workpiece is in contact with high
conductivity electrolytic fluids.
[0091] In another embodiment, the current applied to the electrodes
is adjusted to add material to one portion of the microelectronic
workpiece and remove material from another portion of the
microelectronic workpiece. For example, in one embodiment, the
current applied to all the electrodes 600a-d is reversed, with the
current applied to the outer-most electrode 600d greater than the
current applied to the inner electrodes 600a-c. Accordingly, the
electrodes 600a-d operate as cathodes to remove material from the
workpiece (and remove material from the outer portion of the
workpiece more quickly than from the inner portion) to counteract
the terminal effect, which would otherwise tend to overplate the
peripheral region of the workpiece. After a selected period of time
has passed, material is applied to both the inner and outer regions
of the workpiece. In another embodiment, the outer electrode 600d
can operate as a thieving electrode to attract conductive material
in the electrolytic solution that would otherwise plate to the
peripheral region of the workpiece. In still another arrangement, a
separate thieving electrode positioned outwardly from the
electrodes 600a-d shown in FIG. 4 attracts some of the conductive
material in the electrolytic fluid while the remaining electrodes
plate the remainder of the workpiece. In any of the foregoing
embodiments, the rate at which conductive material is removed from
the microelectronic workpiece, or thieved prior to attaching to the
microelectronic workpiece, can change during the course of the
process.
[0092] In still further embodiments, the process includes other
numbers and/or sequences of process stages. For example, in one
embodiment the currents applied to the electrodes vary continuously
rather than in discrete stages. In other embodiments the current is
applied to more than four electrodes or fewer than four electrodes.
In any of the foregoing embodiments in which material is applied
to, removed from or thieved from particular regions of the
microelectronic workpiece, material may also be applied to, removed
from or thieved from, respectively, other regions of the
microelectronic workpiece, but at a slower rate. For example, when
material is removed from the outer region of the workpiece, it is
preferentially removed from the outer region, but may also be
removed from the inner region at a slower or less preferential
rate.
[0093] 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.
Accordingly, the invention is not limited except as by the appended
claims.
* * * * *