U.S. patent application number 11/217686 was filed with the patent office on 2006-07-06 for systems and methods for electrochemically processing microfeature workpieces.
Invention is credited to John L. Klocke.
Application Number | 20060144712 11/217686 |
Document ID | / |
Family ID | 36773199 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060144712 |
Kind Code |
A1 |
Klocke; John L. |
July 6, 2006 |
Systems and methods for electrochemically processing microfeature
workpieces
Abstract
Systems and methods for electrochemically processing
microfeature workpieces are disclosed herein. In one embodiment, a
method includes flowing a first processing fluid at least proximate
to a processing site in a reaction chamber, flowing a second
processing fluid at least proximate to an electrode in the reaction
chamber, applying an electrical current to the electrode to
establish an electrical current flow in the first and second
processing fluids, separating the first processing fluid and the
second processing fluid with a barrier, and changing a batch of the
first and/or second processing fluid after at least five weeks of
normal operation.
Inventors: |
Klocke; John L.; (Kalispell,
MT) |
Correspondence
Address: |
PERKINS COIE LLP
P.O. BOX 1247
PATENT-SEA
SEATTLE
WA
98111-1247
US
|
Family ID: |
36773199 |
Appl. No.: |
11/217686 |
Filed: |
August 31, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10729349 |
Dec 5, 2003 |
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11217686 |
Aug 31, 2005 |
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10729357 |
Dec 5, 2003 |
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11217686 |
Aug 31, 2005 |
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10861899 |
Jun 3, 2004 |
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11217686 |
Aug 31, 2005 |
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10729349 |
Dec 5, 2003 |
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10861899 |
Jun 3, 2004 |
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10729357 |
Dec 5, 2003 |
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10861899 |
Jun 3, 2004 |
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60607046 |
Sep 3, 2004 |
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Current U.S.
Class: |
205/98 |
Current CPC
Class: |
C25D 21/12 20130101 |
Class at
Publication: |
205/098 |
International
Class: |
C25D 21/18 20060101
C25D021/18 |
Claims
1. A method of electrochemically processing microfeature
workpieces, the method comprising: flowing a first processing fluid
at least proximate to a processing site in a reaction chamber;
flowing a second processing fluid at least proximate to an
electrode in the reaction chamber; applying an electrical current
to the electrode to establish an electrical current flow in the
first and second processing fluids; separating the first processing
fluid and the second processing fluid with a barrier; and changing
a batch of the first and/or second processing fluid after at least
five weeks of normal operation.
2. The method of claim 1 wherein changing the batch of the first
and/or second processing fluid comprises replacing the batch of the
first and/or second processing fluid after at least two months of
normal operation.
3. The method of claim 1 wherein changing the batch of the first
and/or second processing fluid comprises replacing the batch of the
first and/or second processing fluid after at least three months of
normal operation.
4. The method of claim 1 wherein changing the batch of the first
and/or second processing fluid comprises replacing the batch of the
first and/or second processing fluid after at least six months of
normal operation.
5. The method of claim 1 wherein changing the batch of the first
and/or second processing fluid comprises replacing the batch of the
first and/or second processing fluid after at least one year of
normal operation.
6. The method of claim 1 wherein changing the batch of the first
and/or second processing fluid comprises replacing the batch of the
first processing fluid after at least five weeks of normal
operation.
7. The method of claim 1 wherein separating the first and second
processing fluids comprises inhibiting organic additives from
passing between the first and second processing fluids with a
porous barrier.
8. The method of claim 1 wherein separating the first and second
processing fluids comprises separating the flow of the first
processing fluid from the flow of the second processing fluid with
a semipermeable barrier.
9. The method of claim 1 wherein separating the first and second
processing fluids comprises separating the flows of the first and
second processing fluids with a nonporous barrier configured to
allow either cations or anions to pass through the barrier between
the first and second processing fluids.
10. The method of claim 1 wherein: flowing the first processing
fluid comprises flowing a catholyte having a concentration of
between approximately 10 g/l and approximately 200 g/l of acid; and
flowing the second processing fluid comprises flowing an anolyte
having a concentration of between approximately 0.1 g/l and
approximately 1.0 g/l of acid.
11. The method of claim 1 wherein: flowing the first processing
fluid comprises flowing a catholyte having a first concentration of
acid; and flowing the second processing fluid comprises flowing an
anolyte having a second concentration of acid, the ratio of the
first concentration of acid to the second concentration of acid
being between approximately 10:1 and approximately 20,000:1.
12. The method of claim 1 wherein: flowing the second processing
fluid comprises flowing the second processing fluid at least
proximate to a plurality of electrodes in the reaction chamber; and
applying the electrical current comprises applying electrical
potentials to individual electrodes to establish the electrical
current flow in the first and second processing fluids.
13. A method of operating a system for depositing material onto
microfeature workpieces, the method comprising: processing a
plurality of microfeature workpieces in an electrochemical
deposition chamber, the deposition chamber comprising (a) a
processing unit including a first flow system configured to convey
a flow of a first processing fluid to the microfeature workpieces,
(b) an electrode unit coupled to the processing unit, the electrode
unit including a plurality of electrode compartments, a plurality
of electrodes in corresponding compartments, and a second flow
system configured to convey a flow of a second processing fluid
proximate to the electrodes, and (c) a barrier between the
processing unit and the electrode unit to inhibit selected matter
from passing between the first and second processing fluids; and
replacing a batch of the first and/or second processing fluid after
not less than six weeks of processing.
14. The method of claim 13 wherein replacing the batch of the first
and/or second processing fluid comprises changing the batch of the
first and/or second processing fluid after not less than two months
of processing.
15. The method of claim 13 wherein replacing the batch of the first
and/or second processing fluid comprises changing the batch of the
first and/or second processing fluid after not less than three
months of processing.
16. The method of claim 13 wherein replacing the batch of the first
and/or second processing fluid comprises changing the batch of the
first and/or second processing fluid after not less than six months
of processing.
17. The method of claim 13 wherein replacing the batch of the first
and/or second processing fluid comprises changing the batch of the
first and/or second processing fluid after not less than one year
of processing.
18. The method of claim 13 wherein the barrier comprises a porous
barrier.
19. The method of claim 13 wherein the barrier comprises a
semipermeable barrier.
20. A method of electrochemically processing microfeature
workpieces, the method comprising: flowing a first processing fluid
at least proximate to a microfeature workpiece in a reaction
chamber; flowing a second processing fluid at least proximate to an
electrode in the reaction chamber; selectively applying an
electrical current to the electrode to establish an electrical
current flow in the first and second processing fluids; separating
the first processing fluid and the second processing fluid with a
barrier; and removing and replenishing the first and/or second
processing fluid at a rate of less than five percent of the
corresponding fluid volume per day.
21. The method of claim 20 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
the first and/or second processing fluid at a rate of three percent
or less of the corresponding fluid volume per day.
22. The method of claim 20 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
ten liters or less of the first and/or second processing fluid per
day.
23. The method of claim 20 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
five liters or less of the first and/or second processing fluid per
day.
24. The method of claim 20 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
one liter or less of the first and/or second processing fluid per
day.
25. The method of claim 20 wherein removing and replenishing the
first and/or second processing fluid comprises analyzing the
removed first and/or second processing fluid.
26. The method of claim 20 wherein separating the first and second
processing fluids comprises inhibiting organic additives from
passing between the first and second processing fluids with a
porous barrier.
27. The method of claim 20 wherein separating the first and second
processing fluids comprises separating the flow of the first
processing fluid from the flow of the second processing fluid with
a semipermeable barrier.
28. The method of claim 20 wherein separating the first and second
processing fluids comprises separating the flows of the first and
second processing fluids with a nonporous barrier configured to
allow either cations or anions to pass through the barrier between
the first and second processing fluids.
29. The method of claim 20 wherein: flowing the first processing
fluid comprises flowing a catholyte having a concentration of
between approximately 10 g/l and approximately 200 g/l of acid; and
flowing the second processing fluid comprises flowing an anolyte
having a concentration of between approximately 0.1 g/l and
approximately 1.0 g/l of acid.
30. The method of claim 20 wherein: flowing the first processing
fluid comprises flowing a catholyte having a first concentration of
acid; and flowing the second processing fluid comprises flowing an
anolyte having a second concentration of acid, the ratio of the
first concentration of acid to the second concentration of acid
being between approximately 10:1 and approximately 20,000:1.
31. The method of claim 20 wherein: flowing the second processing
fluid comprises flowing the second processing fluid at least
proximate to a plurality of electrodes in the reaction chamber; and
selectively applying the electrical current comprises applying
electrical potentials to individual electrodes to establish the
electrical current flow in the first and second processing
fluids.
32. A method of operating a system for depositing material onto
microfeature workpieces, the method comprising: processing a
plurality of microfeature workpieces in an electrochemical
deposition chamber, the deposition chamber comprising (a) a
processing unit including a first flow system configured to convey
a flow of a first processing fluid to the microfeature workpieces,
(b) an electrode unit coupled to the processing unit, the electrode
unit including a plurality of electrode compartments, a plurality
of electrodes in corresponding compartments, and a second flow
system configured to convey a flow of a second processing fluid
proximate to the electrodes, and (c) a barrier between the
processing unit and the electrode unit to inhibit selected matter
from passing between the first and second processing fluids; and
removing and replenishing four percent or less of the first and/or
second processing fluid per day during processing.
33. The method of claim 32 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
three percent or less of the first and/or second processing fluid
per day.
34. The method of claim 32 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
ten liters or less of the first and/or second processing fluid per
day.
35. The method of claim 32 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
five liters or less of the first and/or second processing fluid per
day.
36. The method of claim 32 wherein removing and replenishing the
first and/or second processing fluid comprises bleeding and feeding
one liter or less of the first and/or second processing fluid per
day.
37. The method of claim 32 wherein the barrier comprises a porous
barrier.
38. The method of claim 32 wherein the barrier comprises a
semipermeable barrier.
39. A system for wet chemical processing of microfeature
workpieces, the system comprising: a processing unit including a
first flow system for conveying a flow of a first processing fluid
to a microfeature workpiece; an electrode unit coupled to the
processing unit, the electrode unit including an electrode and a
second flow system for conveying a flow of a second processing
fluid proximate to the electrode; a barrier between the processing
unit and the electrode unit to inhibit selected matter from passing
between the first and second processing fluids; and a controller
operably coupled to the processing and/or electrode unit, the
controller having a computer-readable medium containing
instructions to perform a method comprising-- flowing the first
processing fluid at least proximate to the microfeature workpiece;
flowing the second processing fluid at least proximate to the
electrode; applying an electrical current to the electrode to
establish an electrical current flow in the first and second
processing fluids; and changing a batch of the first and/or second
processing fluid after at least five weeks of normal operation.
40. The system of claim 39 wherein the computer-readable medium
instruction changing the batch of the first and/or second
processing fluid comprises replacing the batch of the first and/or
second processing fluid after at least two months of normal
operation.
41. The system of claim 39 wherein the computer-readable medium
instruction changing the batch of the first and/or second
processing fluid comprises replacing the batch of the first and/or
second processing fluid after at least three months of normal
operation.
42. The system of claim 39 wherein the computer-readable medium
instruction changing the batch of the first and/or second
processing fluid comprises replacing the batch of the first and/or
second processing fluid after at least six months of normal
operation.
43. The system of claim 39 wherein the computer-readable medium
instruction changing the batch of the first and/or second
processing fluid comprises replacing the batch of the first and/or
second processing fluid after at least one year of normal
operation.
44. The system of claim 39 wherein the barrier comprises a
semipermeable barrier that allows either cations or anions to pass
through the barrier between the first and second processing
fluids.
45. A system for wet chemical processing of microfeature
workpieces, the system comprising: a processing unit including a
first flow system for conveying a flow of a first processing fluid
to a microfeature workpiece; an electrode unit coupled to the
processing unit, the electrode unit including a plurality of
electrode compartments, a plurality of electrodes in corresponding
compartments, and a second flow system for conveying a flow of a
second processing fluid proximate to the electrodes; a barrier
between the processing unit and the electrode unit to separate the
first and second processing fluids; and a controller operably
coupled to the processing and/or electrode unit, the controller
having a computer-readable medium containing instructions to
perform a method comprising-- processing a plurality of
microfeature workpieces in the processing unit; and replacing a
batch of the first and/or second processing fluid after not less
than six weeks of processing.
46. A system for wet chemical processing of microfeature
workpieces, the system comprising: a processing unit including a
first flow system for conveying a flow of a first processing fluid
to a microfeature workpiece; an electrode unit coupled to the
processing unit, the electrode unit including an electrode and a
second flow system for conveying a flow of a second processing
fluid proximate to the electrode; a barrier between the processing
unit and the electrode unit to inhibit selected matter from passing
between the first and second processing fluids; and a controller
operably coupled to the processing and/or electrode unit, the
controller having a computer-readable medium containing
instructions to perform a method comprising-- flowing the first
processing fluid at least proximate to the microfeature workpiece;
flowing the second processing fluid at least proximate to the
electrode; selectively applying an electrical current to the
electrode to establish an electrical current flow in the first and
second processing fluids; and removing and replenishing the first
and/or second processing fluid at a rate of less than five percent
of the corresponding fluid volume per day.
47. A system for wet chemical processing of microfeature
workpieces, the system comprising: a processing unit including a
first flow system for conveying a flow of a first processing fluid
to a microfeature workpiece; an electrode unit coupled to the
processing unit, the electrode unit including a plurality of
electrode compartments, a plurality of electrodes in corresponding
compartments, and a second flow system for conveying a flow of a
second processing fluid proximate to the electrodes; a barrier
between the processing unit and the electrode unit to separate the
first and second processing fluids; and a controller operably
coupled to the processing and/or electrode unit, the controller
having a computer-readable medium containing instructions to
perform a method comprising-- processing a plurality of
microfeature workpieces in the processing unit; and removing and
replenishing four percent or less of the first and/or second
processing fluid per day during processing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of (a)
U.S. patent application Ser. No. 10/729,349 filed on Dec. 5, 2003;
(b) U.S. patent application Ser. No. 10/729,357 filed on Dec. 5,
2003; and (c) U.S. patent application Ser. No. 10/861,899 filed
Jun. 3, 2004, which is a continuation-in-part of U.S. application
Ser. No. (i) 10/729,349 filed on Dec. 5, 2003 and (ii) Ser. No.
10/729,357 filed on Dec. 5, 2003, all of which are incorporated
herein by reference. The present application is also related to
U.S. patent application Ser. No. ______ (Perkins Coie Docket No.
291958239US) filed on ______, and entitled SYSTEMS AND METHODS FOR
ELECTROCHEMICALLY PROCESSING MICROFEATURE WORKPIECES, which is
hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] This application relates to systems and methods for
electrochemically processing microfeature workpieces having a
plurality of microdevices integrated in and/or on the workpiece.
The microdevices can include submicron features. Particular aspects
of the present invention are directed toward methods for changing
the processing fluid in wet chemical processing systems.
BACKGROUND
[0003] Microelectronic devices, such as semiconductor devices,
imagers and 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
(i.e., planarization) to remove a portion of the deposited
conductive layers for forming electrically isolated contacts and/or
conductive lines.
[0004] Tools that plate metals or other materials onto 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,
electrophoretic resist and other materials 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] Conventional single-wafer processing stations generally
include a container for receiving a flow of electroplating solution
from a fluid inlet. The processing station can include an anode, a
plate-type diffuser having a plurality of apertures, and a
workpiece holder for carrying a workpiece. The workpiece holder can
include a plurality of electrical contacts for providing electrical
current to a seed layer on the surface of the workpiece. When the
seed layer is biased with a negative potential relative to the
anode, it acts as a cathode. In operation, the electroplating fluid
flows around the anode, through the apertures in the diffuser, and
against the plating surface of the workpiece. The electroplating
solution is an electrolyte that conducts electrical current between
the anode and the cathodic seed layer on the surface of the
workpiece. Therefore, ions in the electroplating solution plate the
surface of the workpiece.
[0006] The plating machines used in fabricating microelectronic
devices must meet many specific performance criteria. For example,
many plating processes must be able to form small contacts in vias
or trenches that are less than 0.5 .mu.m wide, and often less than
0.1 .mu.m wide. A combination of organic additives such as
"accelerators," "suppressors," and "levelers" can be added to the
electroplating solution to improve the plating process within the
trenches so that the plating metal fills the trenches from the
bottom up. As such, maintaining the proper concentration of organic
additives in the electroplating solution is important to properly
fill very small features.
[0007] One drawback of conventional plating processes is that the
organic additives decompose and break down proximate to the surface
of the anode. Also, as the organic additives decompose, it is
difficult to control the concentration of organic additives and
their associated breakdown products in the plating solution, which
can result in poor feature filling and nonuniform layers. Moreover,
the decomposition of organic additives produces byproducts that can
cause defects or other nonuniformities. To reduce the rate at which
organic additives decompose near the anode, other anodes such as
copper-phosphorous anodes can be used.
[0008] Another technique to compensate for breakdown products and
byproducts in conventional tools is to periodically replace the
electroplating solution to provide a fresh solution with an
acceptable concentration of byproducts. The electroplating solution
is changed in either a batch process in which the entire solution
is replaced at one time or a bleed-and-feed process in which a
portion of the solution is removed and replenished at a constant
rate or periodically. In batch processing, the electroplating
solution is typically changed every two to five weeks.
Consequently, the composition of the electroplating solution is not
consistent over the life of each batch because although organic
additives are added to the solution to keep the additives within a
desired range, byproducts build up in the solution until the
electroplating process is unsustainable. Bleed-and-feed processes
typically remove and replenish solution at a constant rate such
that a complete volume of the solution is changed every ten to
twenty days. Because electroplating solution is constantly being
removed and replenished, the solution often remains in a consistent
intermediate state with undesirable byproducts.
[0009] One drawback of conventional batch and bleed-and-feed
processes is that the frequent replacement of electroplating
solution (necessitated by byproduct buildup) consumes and wastes
large amounts of expensive organic additives. A significant portion
of the organic additives are wasted when the solution is changed
because both good and decomposed additives are removed with the
solution and replaced by new additives in the fresh solution.
[0010] Another drawback of conventional plating processes is that
organic additives and/or chloride ions in the electroplating
solution can passivate and/or consume pure copper anodes. This
alters the electrical field, which can result in inconsistent
processes and nonuniform layers. One existing approach to inhibit
organic additives from contacting and passivating the anode is to
place a porous barrier between the workpiece and the anode and flow
electroplating solution from the anode toward the workpiece during
operation and while the tool is idle. This approach, however, only
reduces the number of additives that decompose proximate to the
anode surface. The approach also includes using a carbon filter to
remove byproducts from the solution proximate to the workpiece. The
carbon filter, however, generates particles and removes good
organic additives in addition to the decomposed additives. Thus,
there is a need to improve the plating process to reduce the
adverse effects of the organic additives.
SUMMARY
[0011] The present invention is directed toward electrochemical
deposition chambers with a barrier between processing fluids to
mitigate or eliminate the problems caused by organic additives. The
chambers are divided into two distinct systems that interact with
each other to electroplate a material onto the workpiece while
controlling migration of organic additives in the processing fluids
across the barrier to avoid the problems caused by the interaction
between the additives and the anode. As such, the barrier prevents
organic additives from decomposing proximate to the anode and
producing byproducts that interfere with the plating process.
Moreover, by reducing the decomposition of organic additives, the
barrier increases the life of the processing fluids and,
accordingly, reduces the frequency at which the processing fluids
need to be replaced. This reduces the downtime of the chamber and
the volume of organic additives consumed.
[0012] The chambers include a processing unit for providing a first
processing fluid to a workpiece (i.e., working electrode), an
electrode unit for conveying a flow of a second processing fluid
different than the first processing fluid, an electrode (i.e.,
counter electrode) in the electrode unit, and a barrier between the
first and second processing fluids. The barrier can be a porous,
permeable member that permits fluid and small molecules to flow
through the barrier between the first and second processing fluids.
Alternatively, the barrier can be a nonporous, semipermeable member
that prevents fluid flow between the first and second processing
fluids while allowing ions to pass between the fluids. In either
case, the barrier separates and/or isolates components of the first
and second processing fluids from each other such that the first
processing fluid can have different chemical characteristics than
the second processing fluid. For example, the first processing
fluid can be a catholyte having organic additives and the second
processing fluid can be an anolyte without organic additives or
with a much lower concentration of such additives.
[0013] The barrier provides several advantages by substantially
preventing the organic additives in the catholyte from migrating to
the anolyte. First, because the organic additives are inhibited
from moving into the anolyte, the additives cannot flow past the
anode and decompose into products that interfere with the plating
process. Second, because the organic additives do not decompose at
the anode, the anode is consumed at a much slower rate in the
catholyte so that it is less expensive and easier to control the
concentration of organic additives in the catholyte. Third, less
expensive anodes, such as pure copper anodes, can be used in the
anolyte because the risk of passivation is reduced or
eliminated.
[0014] The barrier in the chamber provides a system that is
significantly more efficient and produces significantly better
quality products. The system is more efficient because using one
processing fluid for the workpiece and another processing fluid for
the electrodes allows the processing fluids to be tailored to the
best use in each area without having to compromise to mitigate the
adverse effects of using only a single processing solution. As
such, the tool does not need to be shut down as often to adjust the
fluids, and the tool consumes less organic additives and other bath
constituents. The system produces better quality products because
using two different processing fluids allows better control of the
concentration of important constituents in each processing
fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 schematically illustrates a system for wet chemical
processing of microfeature workpieces in accordance with one
embodiment of the invention.
[0016] FIGS. 2A-2H graphically illustrate the relationship between
the concentration of hydrogen and copper ions in an anolyte and a
catholyte during a plating cycle and while the system of FIG. 1 is
idle in accordance with one embodiment of the invention.
[0017] FIG. 3 schematically illustrates a system for wet chemical
processing of microfeature workpieces in accordance with another
embodiment of the invention.
DETAILED DESCRIPTION
[0018] As used herein, the terms "microfeature workpiece" or
"workpiece" refer to substrates on and/or in which microdevices are
formed. Typical microdevices include microelectronic circuits or
components, thin-film recording heads, data storage elements,
microfluidic devices, and other products. Micromachines or
micromechanical devices are included within this definition because
they are manufactured in much the same manner as integrated
circuits. The substrates can be semiconductive pieces (e.g.,
silicon wafers or gallium arsenide wafers), nonconductive pieces
(e.g., various ceramic substrates), or conductive pieces (e.g.,
doped wafers). Also, the term electrochemical processing or
deposition includes electroplating, electro-etching, anodization,
and/or electroless plating.
[0019] Several embodiments of electrochemical deposition chambers
for processing microfeature workpieces are particularly useful for
electrolytically depositing metals or electrophoretic resist in
and/or on structures of a workpiece. The deposition chambers in
accordance with the invention can accordingly be used in systems
for etching, rinsing, or other types of wet chemical processes in
the fabrication of microfeatures in and/or on semiconductor
substrates or other types of workpieces. Several embodiments of wet
chemical processing systems including electrochemical deposition
chambers are set forth in FIGS. 1-3 and the corresponding text to
provide a thorough understanding of particular embodiments of the
invention. A person skilled in the art will understand, however,
that the invention may have additional embodiments or that the
invention may be practiced without several of the details of the
embodiments shown in FIGS. 1-3.
A. Embodiments of Wet Chemical Processing Systems
[0020] FIG. 1 schematically illustrates a system 100 for
electrochemical deposition, electropolishing, or other wet chemical
processing of microfeature workpieces. The system 100 includes an
electrochemical deposition chamber 102 having a head assembly 104
(shown schematically) and a wet chemical vessel 110 (shown
schematically). The head assembly 104 loads, unloads, and positions
a workpiece W or a batch of workpieces at a processing site
relative to the vessel 110. The head assembly 104 typically
includes a workpiece holder having a contact assembly with a
plurality of electrical contacts configured to engage a conductive
layer on the workpiece W. The workpiece holder can accordingly
apply an electrical potential to the conductive layer on the
workpiece W. Suitable head assemblies, workpiece holders, and
contact assemblies are disclosed in U.S. Pat. Nos. 6,228,232;
6,280,583; 6,303,010; 6,309,520; 6,309,524; 6,471,913; 6,527,925;
6,569,297; 6,773,560; and 6,780,374, all of which are hereby
incorporated by reference in their entirety.
[0021] The illustrated vessel 110 includes a processing unit 120
(shown schematically), an electrode unit 180 (shown schematically),
and a barrier 170 (shown schematically) between the processing and
electrode units 120 and 180. The processing unit 120 is configured
to contain a first processing fluid for processing the microfeature
workpiece W. The electrode unit 180 is configured to contain an
electrode 190 and a second processing fluid at least proximate to
the electrode 190. The second processing fluid is generally
different than the first processing fluid, but they can be the same
in some applications. In general, the first and second processing
fluids have some ions in common. The first processing fluid in the
processing unit 120 is a catholyte and the second processing fluid
in the electrode unit 180 is an anolyte when the workpiece is
cathodic. In electropolishing or other deposition processes,
however, the first processing fluid can be an anolyte and the
second processing fluid can be a catholyte.
[0022] The system 100 further includes a first flow system 112 that
stores and circulates the first processing fluid and a second flow
system 192 that stores and circulates the second processing fluid.
The first flow system 112 may include (a) a first processing fluid
reservoir 113, (b) a plurality of fluid conduits 114 to convey a
flow of the first processing fluid between the first processing
fluid reservoir 113 and the processing unit 120, and (c) a
plurality of components 115 (shown schematically) in the processing
unit 120 to convey a flow of the first processing fluid between the
processing site and the barrier 170. The second flow system 192 may
include (a) a second processing fluid reservoir 193, (b) a
plurality of fluid conduits 185 to convey the flow of the second
processing fluid between the second processing fluid reservoir 193
and the electrode unit 180, and (c) a plurality of components 184
(shown schematically) in the electrode unit 180 to convey the flow
of the second processing fluid between the electrode 190 and the
barrier 170.
[0023] The barrier 170 is positioned between the first and second
processing fluids in the region of the interface between the
processing unit 120 and the electrode unit 180 to separate and/or
isolate the first processing fluid from the second processing
fluid. For example, the barrier 170 can be a porous, permeable
membrane that permits fluid and small molecules to flow through the
barrier 170 between the first and second processing fluids.
Alternatively, the barrier 170 can be a nonporous, semipermeable
membrane that prevents fluid flow between the first and second flow
systems 112 and 192 while selectively allowing ions, such as
cations and/or anions, to pass through the barrier 170 between the
first and second processing fluids. In either case, the barrier 170
restricts bubbles, particles, and large molecules such as organic
additives from passing between the first and second processing
fluids.
[0024] Nonporous barriers, for example, can be substantially free
of open area. Consequently, fluid is inhibited from passing through
a nonporous barrier when the first and second flow systems 112 and
192 operate at typical pressures. Water, however, can be
transported through the nonporous barrier via osmosis and/or
electro-osmosis. Osmosis can occur when the molar concentrations in
the first and second processing fluids are substantially different.
Electro-osmosis can occur as water is carried through the nonporous
barrier with current-carrying ions in the form of a hydration
sphere. When the first and second processing fluids have similar
molar concentrations and no electrical current is passed through
the processing fluids, fluid flow between the first and second
processing fluids is substantially prevented.
[0025] The illustrated barrier 170 can also be hydrophilic so that
bubbles in the processing fluids do not cause portions of the
barrier 170 to dry, which reduces conductivity through the barrier
170. Suitable materials for permeable barriers include
polyethersulfone, Gore-tex, Teflon coated woven filaments,
polypropylene, glass fritz, silica gels, and other porous polymeric
materials. Suitable membrane type (i.e., semipermeable) barriers
170 include NAFION membranes manufactured by DuPont.degree.,
Ionac.RTM. membranes manufactured by Sybron Chemicals Inc., and
NeoSepta membranes manufactured by Tokuyuma.
[0026] When the system 100 is used for electrochemical processing,
an electrical potential can be applied to the electrode 190 and the
workpiece W such that the electrode 190 is an anode and the
workpiece W is a cathode. The first and second processing fluids
are accordingly a catholyte and an anolyte, respectively, and each
fluid can include a solution of metal ions to be plated onto the
workpiece W. The electrical field between the electrode 190 and the
workpiece W may drive positive ions through the barrier 170 from
the anolyte to the catholyte, or drive negative ions in the
opposite direction. In plating applications, an electrochemical
reaction occurs at the microfeature workpiece W in which metal ions
are reduced to form a solid layer of metal on the microfeature
workpiece W. In electrochemical etching and other electrochemical
applications, the electrical field may drive ions in the opposite
direction.
[0027] One feature of the system 100 illustrated in FIG. 1 is that
the barrier 170 separates the first processing fluid in the first
flow system 112 from the second processing fluid in the second flow
system 192, but allows ions and/or small molecules, depending on
the type of barrier 170, to pass between the first and second
processing fluids. As such, the fluid in the processing unit 120
can have different chemical and/or physical characteristics than
the fluid in the electrode unit 180. For example, the first
processing fluid can be a catholyte having organic additives and
the second processing fluid can be an anolyte without organic
additives or with a much lower concentration of such additives. As
explained above in the summary section, the lack of organic
additives in the anolyte provides the following advantages: (a)
reduces byproducts of decomposed organics in the catholyte; (b)
reduces consumption of the organic additives; (c) reduces
passivation of the anode; and (d) enables efficient use of pure
copper anodes.
[0028] The illustrated system 100 further includes a chemical
management system 130 (shown schematically) for controlling the
composition of the first and second processing fluids and a
controller 140 (shown schematically) for operating the chemical
management system 130. The chemical management system 130 can be
operably coupled to (a) the processing unit 120 and/or the first
processing fluid reservoir 113 for monitoring and controlling the
concentrations of individual constituents in the first processing
fluid, and/or (b) the electrode unit 180 and/or the second
processing fluid reservoir 193 for monitoring and controlling the
concentrations of individual constituents in the second processing
fluid. The chemical management system 130, for example, can add
and/or remove individual organic additives, metals, and/or water
from the first and/or second processing fluid based on the
composition of the fluid or other parameters. In several
embodiments, when the anolyte lacks organic additives, the chemical
management system 130 may need to add only water to the anolyte.
The chemical management system 130 may also need to periodically
(a) add organic additives to the catholyte, and (b) add and/or
remove water from the catholyte.
[0029] The illustrated chemical management system 130 can also
replace the first and/or second processing fluid after a
predetermined period of time or after the concentration of
byproducts in the fluid exceeds a threshold. For example, in one
embodiment, the chemical management system 130 replaces a batch of
the first and/or second processing fluid after five weeks of normal
operation. In one aspect of this embodiment, the chemical
management system 130 changes the batch of the first and/or second
processing fluid after six weeks. In a further aspect of this
embodiment, the system 130 changes the batch of the first and/or
second processing fluid after two months. In a further aspect of
this embodiment, the system 130 changes the batch of the first
and/or second processing fluid after three months. In a further
aspect of this embodiment, the system 130 changes the batch of the
first and/or second processing fluid after six months. In a further
aspect of this embodiment, the system 130 changes the batch of the
first and/or second processing fluid after one year.
[0030] The chemical management system 130 can also replace the
first and/or second processing fluid by removing and replenishing
the fluid at a specific rate. For example, in one embodiment, the
chemical management system 130 bleeds-and-feeds the first and/or
second processing fluid at a rate of less than five percent of the
corresponding fluid volume per day. In one aspect of this
embodiment, the chemical management system 130 bleeds-and-feeds the
first and/or second processing fluid at a rate of three percent or
less of the corresponding fluid volume per day. In several
embodiments, the chemical management system 130 removes and
replenishes ten liters or less of the first and/or second
processing fluid per day. In one aspect of these embodiments, the
chemical management system 130 removes and replenishes five liters
or less of the first and/or second processing fluid per day. In a
further aspect of these embodiments, the chemical management system
130 removes and replenishes one liter or less of the first and/or
second processing fluid per day. In additional embodiments, the
chemical management system 130 may remove and replenish a volume of
fluid sufficient only for analysis purposes.
[0031] One feature of the system 100 illustrated in FIG. 1 is that
separation of the first and second processing fluids extends the
useful life of the fluids. For example, in several embodiments, the
anolyte can be replaced less frequently because the anolyte lacks
organic additives that decompose into byproducts. The catholyte
includes organic additives, however, the decomposition rate of the
additives in the catholyte is reduced because the additives are
separated from the anode. Accordingly, the catholyte and anolyte
can be replaced less frequently, which reduces the downtime of the
system 100 and the volume of good additives wasted when the fluid
is changed.
[0032] The system 100 illustrated in FIG. 1 is also particularly
efficacious in maintaining the desired concentration of copper ions
or other metal ions in the first processing fluid. During the
electroplating process, it is desirable to accurately control the
concentration of materials in the first processing fluid to ensure
consistent, repeatable depositions on a large number of individual
microfeature workpieces. For example, when copper is deposited on
the workpiece W, it is desirable to maintain the concentration of
copper in the first processing fluid (e.g., the catholyte) within a
desired range to deposit a suitable layer of copper on the
workpiece W. This aspect of the system 100 is described in more
detail below.
[0033] To control the concentration of metal ions in the first
processing solution in some electroplating applications, the system
100 illustrated in FIG. 1 uses characteristics of the barrier 170,
the volume of the first flow system 112, the volume of the second
flow system 192, and the different acid concentrations in the first
and second processing solutions. In general, the concentration of
acid in the first processing fluid is greater than the
concentration of acid in the second processing fluid, and the
volume of the first processing fluid in the system 100 is greater
than the volume of the second processing fluid in the system 100.
As explained in more detail below, these features work together to
maintain the concentration of the constituents in the first
processing fluid within a desired range to ensure consistent and
uniform deposition on the workpiece W. For purposes of
illustration, the effect of increasing the concentration of acid in
the first processing fluid will be described with reference to an
embodiment in which copper is electroplated onto a workpiece. One
skilled in the art will recognize that different metals can be
electroplated and/or the principles can be applied to different wet
chemical processes in other applications. In additional
embodiments, however, the concentration of acid in the first
processing fluid may not be greater than the concentration of acid
in the second processing fluid, and/or the volume of the first
processing fluid may not be greater than the volume of the second
processing fluid.
[0034] FIGS. 2A-2H graphically illustrate the relationship between
the concentrations of hydrogen and copper ions in the anolyte and
catholyte during a plating cycle and while the system 100 is idle.
FIGS. 2A and 2B show the concentration of hydrogen ions in the
second processing fluid (anolyte) and the first processing fluid
(catholyte), respectively, during a plating cycle. The electrical
field readily drives hydrogen ions across the barrier 170 (FIG. 1)
from the anolyte to the catholyte during the plating cycle.
Consequently, the concentration of hydrogen ions decreases in the
anolyte and increases in the catholyte. As measured by percent
concentration change or molarity, the decrease in the concentration
of hydrogen ions in the anolyte is generally significantly greater
than the corresponding increase in the concentration of hydrogen
ions in the catholyte because: (a) the volume of catholyte in the
illustrated system 100 is greater than the volume of anolyte; and
(b) the concentration of hydrogen ions in the catholyte is much
higher than in the anolyte.
[0035] FIGS. 2C and 2D graphically illustrate the concentration of
copper ions in the anolyte and catholyte during the plating cycle.
During the plating cycle, the anode replenishes copper ions in the
anolyte and the electrical field drives the copper ions across the
barrier 170 from the anolyte to the catholyte. Thus, as shown in
FIG. 2C, the concentration of copper ions in the anolyte increases
during the plating cycle. Conversely, in the catholyte cell, FIG.
2D shows that the concentration of copper ions in the catholyte
initially decreases during the plating cycle as the copper ions are
consumed to form a layer on the microfeature workpiece W.
[0036] FIGS. 2E-2H graphically illustrate the concentration of
hydrogen and copper ions in the anolyte and the catholyte while the
system 100 of FIG. 1 is idle. For example, FIGS. 2E and 2F
illustrate that the concentration of hydrogen ions increases in the
anolyte and decreases in the catholyte while the system 100 is idle
because the greater concentration of acid in the catholyte drives
hydrogen ions across the barrier 170 to the anolyte. FIGS. 2G and
2H graphically illustrate that the concentration of copper ions
decreases in the anolyte and increases in the catholyte while the
system 100 is idle. The movement of hydrogen ions into the anolyte
creates a charge imbalance that drives copper ions from the anolyte
to the catholyte.
[0037] One feature of the embodiment illustrated in FIG. 1 is that
when the system 100 is idle, the catholyte is replenished with
copper because of the difference in the concentration of acid in
the anolyte and catholyte. An advantage of this feature is that the
desired concentration of copper in the catholyte can be maintained
while the system 100 is idle. Another advantage of this feature is
that the increased movement of copper ions across the barrier 170
prevents saturation of the anolyte with copper, which can cause
passivation of the anode and/or the formation of salt crystals.
[0038] The foregoing operation of the system 100 shown in FIG. 1
occurs, in part, by selecting suitable concentrations of hydrogen
ions (i.e., acid protons) and copper. In several useful processes
for depositing copper, the acid concentration in the first
processing fluid can be from approximately 10 g/l to approximately
200 g/l, and the acid concentration in the second processing fluid
can be from approximately 0.1 g/l to approximately 1.0 g/l.
Alternatively, the acid concentration of the first and/or second
processing fluid can be outside of these ranges. For example, the
first processing fluid can have a first concentration of acid and
the second processing fluid can have a second concentration of acid
less than the first concentration. The ratio of the first
concentration of acid to the second concentration of acid, for
example, can be from approximately 10:1 to approximately 20,000:1.
The concentration of copper is also a parameter. For example, in
many copper plating applications, the first and second processing
fluids can have a copper concentration of between approximately 10
g/l and approximately 50 g/l. Although the foregoing ranges are
useful for many applications, it will be appreciated that the first
and second processing fluids can have other concentrations of
copper and/or acid.
[0039] In other embodiments, the barrier can be anionic and the
electrode can be an inert anode (i.e. platinum or iridium oxide) to
prevent the accumulation of sulfate ions in the first processing
fluid. In this embodiment, the acid concentration or pH in the
first and second processing fluids can be similar. Alternatively,
the second processing fluid may have a higher concentration of acid
to increase the conductivity of the fluid. Copper salt (copper
sulfate) can be added to the first processing fluid to replenish
the copper in the fluid. Electrical current can be carried through
the barrier by the passage of sulfate anions from the first
processing fluid to the second processing fluid. Therefore, sulfate
ions are less likely to accumulate in the first processing fluid
where they can adversely affect the deposited film.
[0040] In other embodiments, the system can electrochemically etch
copper from the workpiece. In these embodiments, the first
processing solution (the anolyte) contains an electrolyte that may
include copper ions. During electrochemical etching, an electrical
potential can be applied to the electrode and/or the workpiece. An
anionic barrier can be used to prevent positive ions (such as
copper) from passing into the second processing fluid (catholyte).
Consequently, the current is carried by anions, and copper ions are
inhibited from flowing proximate to and being deposited on the
electrode.
[0041] The foregoing operation of the illustrated system 100 also
occurs by selecting suitable volumes of anolyte and catholyte.
Another feature of the embodiment illustrated in FIG. 1 is that the
system 100 has (a) a first volume of the first processing fluid in
the first flow system 112 and the first processing fluid reservoir
113, and (b) a second volume of the second processing fluid in the
second flow system 192 and the second processing fluid reservoir
193. The ratio between the first volume and the second volume can
be from approximately 1.5:1 to 20:1, and in many applications is
approximately 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1. The
difference in volume of the first and second processing fluids
moderates the change in the concentration of materials in the first
processing fluid. For example, as described above with reference to
FIGS. 2A and 2B, when hydrogen ions move from the anolyte to the
catholyte, the percentage change in the concentration of hydrogen
ions in the catholyte is less than the change in the concentration
of hydrogen ions in the anolyte because the volume of catholyte is
greater than the volume of anolyte. In other embodiments, the first
and second volumes can be approximately the same.
B. Additional Embodiments of Wet Chemical Processing Systems
[0042] FIG. 3 schematically illustrates a system 200 for wet
chemical processing of microfeature workpieces in accordance with
another embodiment of the invention. The system 200 is generally
similar to the system 100 described above with reference to FIG. 1.
For example, the illustrated system 200 includes an electrochemical
deposition chamber 202, a first processing fluid reservoir 113, a
second processing fluid reservoir 193, and a chemical management
system 130 for monitoring and controlling the individual
constituents of the first and/or second processing fluid.
[0043] The deposition chamber 202 has a wet chemical vessel 210
(shown schematically) with a processing unit 220 (shown
schematically), an electrode unit 280 (shown schematically), and a
barrier 170 (shown schematically) between the processing and
electrode units 220 and 280. The processing unit 220 of the
illustrated embodiment includes a dielectric divider 242 projecting
from the barrier 170 toward the processing site and a plurality of
chambers 215 (identified individually as 215a-b) defined by the
dielectric divider 242. The chambers 215a-b can be arranged
concentrically and have corresponding openings 244a-b proximate to
the processing site. The chambers 215a-b are configured to convey
the first processing fluid to/from the microfeature workpiece W. In
other embodiments, the processing unit 220 may not include the
dielectric divider 242 and the chambers 215, or the dielectric
divider 242 and the chambers 215 may have other configurations.
[0044] The illustrated electrode unit 280 includes a dielectric
divider 286, a plurality of compartments 284 (identified
individually as 284a-b) defined by the dielectric divider 286, and
a plurality of electrodes 290 (identified individually as 290a-b)
disposed within corresponding compartments 284. The compartments
284 can be arranged concentrically and configured to convey the
second processing fluid at least proximate to the electrodes 290.
Although the illustrated system 200 includes two concentric
electrodes 290, in other embodiments, systems can include a
different number of electrodes and/or the electrodes can be
arranged in a different configuration.
[0045] When the system 200 is used for electrochemical processing,
an electrical potential can be applied to the electrodes 290 and
the workpiece W such that the electrodes 290 are anodes and the
workpiece W is a cathode. The first electrode 290a provides an
electrical field to the workpiece W at the processing site through
the portion of the second processing fluid in the first compartment
284a of the electrode unit 280 and the portion of the first
processing fluid in the first chamber 230a of the processing unit
220. Accordingly, the first electrode 290a provides an electrical
field that is effectively exposed to the processing site via the
first opening 244a. The first opening 244a shapes the electrical
field of the first electrode 290a to create a "virtual electrode"
at the top of the first opening 244a. This is a "virtual electrode"
because the dielectric divider 242 shapes the electrical field of
the first electrode 290a so that the effect is as if the first
electrode 290a were placed in the first opening 244a. Virtual
electrodes are described in detail in U.S. patent application Ser.
No. 09/872,151, which is hereby incorporated by reference in its
entirety. Similarly, the second electrode 290b provides an
electrical field to the workpiece W through the portion of the
second processing fluid in the second compartment 284b of the
electrode unit 280 and the portion of the first processing fluid in
the second chamber 230b of the processing unit 220. Accordingly,
the second electrode 290b provides an electrical field that is
effectively exposed to the processing site via the second opening
244b to create another "virtual electrode."
[0046] In operation, a first current is applied to the first
electrode 290a and a second current is applied to the second
electrode 290b. The first and second electrical currents are
controlled independently of each other such that they can be the
same or different than each other at any given time. Additionally,
the first and second electrical currents can be dynamically varied
throughout a plating cycle. The first and second electrodes 290a-b
accordingly provide a highly controlled electrical field to
compensate for inconsistent or non-uniform seed layers as well as
changes in the plated layer during a plating cycle.
[0047] 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.
* * * * *