U.S. patent application number 10/039808 was filed with the patent office on 2002-06-06 for method and apparatus for supplying electricity uniformly to a workpiece.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Clinton, Jon, Kumar, Anada H., Leon, Ricardo, Olgado, Donald J., Shamouilian, Shamouil, Stevens, Joseph J..
Application Number | 20020066664 10/039808 |
Document ID | / |
Family ID | 24062903 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020066664 |
Kind Code |
A1 |
Shamouilian, Shamouil ; et
al. |
June 6, 2002 |
Method and apparatus for supplying electricity uniformly to a
workpiece
Abstract
The present invention relates to a device that supplies
electricity to a substrate. In one embodiment, the device includes
multiple contacts, a current sensor, and a current regulator. The
current sensor is attached to each of the plurality of contacts to
sense their electric current. A current regulator controls current
applied to each of the multiple contacts in response to the current
sensor. In another embodiment, a compliant ridge is formed about
the periphery of each contact to seal the contact from undesired
chemicals.
Inventors: |
Shamouilian, Shamouil; (San
Jose, CA) ; Kumar, Anada H.; (Milpitas, CA) ;
Olgado, Donald J.; (Palo Alto, CA) ; Stevens, Joseph
J.; (San Jose, CA) ; Leon, Ricardo; (Palo
Alto, CA) ; Clinton, Jon; (San Jose, CA) |
Correspondence
Address: |
Patent Counsel
APPLIED MATERIALS, INC.
P.O. Box 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
24062903 |
Appl. No.: |
10/039808 |
Filed: |
October 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10039808 |
Oct 26, 2001 |
|
|
|
09518182 |
Mar 2, 2000 |
|
|
|
Current U.S.
Class: |
204/228.1 ;
257/E21.175 |
Current CPC
Class: |
C25D 21/12 20130101;
H01L 21/2885 20130101; C25D 17/001 20130101; C25D 7/123
20130101 |
Class at
Publication: |
204/228.1 |
International
Class: |
B23H 003/02 |
Claims
What is claimed is:
1. An apparatus for supplying electricity to a substrate,
comprising: a plurality of contacts; a current sensor attached to
each of the plurality of contacts; and a current regulator that
controls current applied to each of the plurality of contacts in
response to the current sensor.
2. The apparatus of claim 1, further comprising a controller that
determines non-uniformity of current between each of the plurality
of contacts.
3. The apparatus of claim 2, wherein the current regulator operates
in response to the controller.
4. The apparatus of claim 1, wherein the current regulator ensures
that a similar current level is applied to each of the plurality of
contacts.
5. The apparatus of claim 1, further comprising a power supply that
supplies the current to each contact.
6. The apparatus of claim 5, further comprising a plurality of
individual conductors, at least one of the individual conductors
connected from the power supply to each of the plurality of
contacts.
7. The apparatus of claim 6, wherein the current regulator further
comprises a plurality of varistors, at least one of the varistors
connected to each of the individual conductors to control current
applied to each of the plurality of contacts.
8. The apparatus of claim 6, wherein the current regulator further
comprises a current control device that regulates the current over
each of the individual conductors.
9. The apparatus of claim 1, further comprising a conformal ridge
formed around the periphery of the contacts.
10. An method for supplying electricity to a substrate, comprising:
providing a plurality of contacts; sensing the current applied to
each of the plurality of contacts; and controlling the current
applied to each of the plurality of contacts in response to the
current sensor.
11. The method of claim 10, wherein controlling the current further
comprises balancing the current applied to each of the plurality of
contacts.
12. The method of claim 10, wherein controlling the current further
comprises varying the resistance of a conductor that supplies the
current to the contact.
13. The method of claim 10, wherein controlling the current further
comprises varying the current level applied to a conductor that
supplies the current to the contact.
14. A method of forming a contact ring, comprising: providing a
substrate; depositing at least one conductive layer on the
substrate; and depositing at least one insulative layer adjacent to
the at least one conductive layer, on the substrate.
15. The method of claim 14, further comprising electrically
connecting a contact to at least one of the conductive layers.
16. The method of claim 14, wherein at least one of the conductive
layers is of sufficient thickness such that after the depositing of
at least one insulative layer, a compliant ridge is defined in the
insulative layer.
17. The method of claim 16, further comprising electrically
connecting a contact to at least one of the conductive layers,
wherein the compliant ridge extends around the periphery of the
contact.
18. A contact ring for providing electrical contact between a wafer
and a power supply, comprising: a conductive layer an insulative
layer deposited above the conductive layer; a contact in electrical
contact with the conductive layer and extending through the
insulative layer to an external surface; and a compliant ridge
formed on the external surface, and extending about the periphery
of the contact.
19. The contact ring of claim 18, wherein the insulative layer is a
conformal layer, and the conductive layer is of a sufficient
dimension to form the compliant ridge on the insulative layer.
20. The contact ridge of claim 18, wherein the compliant ridge is
formed by an additional layer deposited on top of the insulative
layer.
21. An apparatus for supplying electricity to a substrate,
comprising: a metal deposition system comprising a deposition cell,
an anode, and a cathode, the cathode comprising: a plurality of
contacts, a current sensor attached to each of the plurality of
contacts, and a current regulator that controls current applied to
each of the plurality of contacts in response to the current
sensor.
22. The apparatus of claim 21, wherein the metal deposition system
is an electroplating device.
23. The apparatus of claim 21, further comprising a compliant ridge
formed on the external surface and extending about the periphery of
the contact.
Description
BACKGROUND OF THE DISCLOSURE
[0001] 1. Field of the Invention
[0002] The invention relates to supplying electrical contacts for
applying electrical power to a substrate in a metal depositing
system. More particularly, the invention relates to a method and
apparatus for uniformly applying electricity to a workpiece in an
electroplating system.
[0003] 2. Description of the Background Art
[0004] Sub-quarter micron, multi-level metallization is an
important technology for the next generation of ultra large scale
integration (ULSI). Reliable formation of these interconnect
features permits increased circuit density, improves acceptance of
ULSI, and improves quality of individual processed wafers. As
circuit densities increase, the widths of vias, contacts and other
features, as well as the width of the dielectric materials between
the features, decrease. However, the height of the dielectric
layers remains substantially constant. Therefore, the aspect ratio
for the features (i.e., their height or depth divided by their
width) increases. Many traditional deposition processes, such as
physical vapor deposition (PVD) and chemical vapor deposition
(CVD), presently have difficulty providing uniform features having
aspect ratios greater than 4/1, and particularly greater than 10/1.
Therefore, a great amount of ongoing effort is directed at the
formation of void-free, nanometer-sized features having aspect
ratios of 4/1, or higher.
[0005] Electroplating, previously limited in integrated circuit
design to the fabrication of lines on circuit boards, is being used
to fill vias and contacts. Metal electroplating, in general, can be
achieved by a variety of techniques. One embodiment of an
electroplating process involves initially depositing a barrier
layer over the feature surfaces of the wafer, depositing a
conductive metal seed layer over the barrier layer, and then
depositing a conductive metal (such as copper) over the seed layer
to fill the structure/feature. Finally, the deposited layers are
planarized by, for example, chemical mechanical polishing (CMP), to
define a conductive interconnect feature.
[0006] Damascene processes comprise those processes in which metal
conductive layers are applied to fill troughs formed in insulative
material. The surface of the metal conductive material is then
etched to provide a smooth-surfaced insulated conductor formed in
the insulative material. Effectiveness and success of the damascene
and dual-damascene processes (that are used in such applications as
fabricating highly conductive copper wiring on silicon wafers)
depends largely upon the uniformity of copper layers deposited. The
effectiveness also depends on the partial removal of the copper
layer by chemical-mechanical polishing.
[0007] In electroplating, depositing of a metallic layer is
accomplished by delivering electric power to the seed layer and
then exposing the wafer-plating surface to an electrolytic solution
containing the metal to be deposited. The subsequently deposited
metal layer adheres to the seed layer (as well as a conformal
layer) to provide for uniform growth of the metal layer. A number
of obstacles impair consistently reliable electroplating of metal
onto wafers having nanometer-sized, high aspect ratio features.
These obstacles include non-uniform power distribution and current
density to across the wafer plating surface.
[0008] In metal deposition systems, several things may lend to
uneven depositing of the metal layer. One major contributor to a
non-uniform deposition of process time dependent variations in
material buildup upon the different contacts 56. Each contact will
thus develop unique and unpredictable geometric profiles and
densities, thus producing varying and unpredictable resistances
when exposed to a similar voltage. The varying resistance of the
individual contacts 56 results in a non-uniform current density
distribution across the wafer. The varying resistances of the
contacts provide modified electrical fields. In addition, the
contact resistance at the contact/seed layer interface may vary
from wafer 48 to wafer, resulting in inconsistent plating
distribution between different wafers using the same equipment.
[0009] The power supply circuit that supplies current to the seed
layer includes the plurality of contacts 56 located on a contact
ring. In electroplater embodiments, a single power supply applies
electricity to a junction that is electrically connected to all of
the metal contacts 56. The electrical characteristics of different
contacts may vary, especially after prolonged use. Those metal
contacts having a higher resistance provide less electrical current
to the adjacent seed layer. If an equal voltage is applied to each
metal contact, these contacts with increased resistance also have a
higher current flowing therethrough as indicated by Ohm's law.
Non-uniform power distribution and current densities are applied to
the seed layer across the wafer plating surface as a result of the
varied electrical current applied by the contacts. This inequality
of non-uniform power distribution and current densities results in
uneven deposition of metal to the seed layer.
[0010] Therefore, there remains a need for an apparatus that
delivers a uniform electric current to multiple contacts, and to a
seed layer deposited on a wafer. Such a device would provide
substantially uniform electrical power distribution to a wafer
surface in an electroplating cell, enabling deposition of reliable
and consistent conductive metallic layers on wafers.
SUMMARY OF THE INVENTION
[0011] The present invention generally provides a method and
apparatus that supplies electricity to a substrate. In one
embodiment, the device includes multiple contacts, a current
sensor, and a current regulator. The current sensor is attached to
each of the plurality of contacts to sense their electric current.
A current regulator controls current applied to each of the
multiple contacts in response to a signal produced by the current
sensor.
[0012] In another embodiment, a compliant ridge is formed about the
periphery of each contact that can form a seal about the contacts.
The compliant ridge may be formed by either applying a thick
conductor layer resulting in a ridge defined in an external surface
of the conformal layer. Alternately, the compliant ridge may be
formed as an additional layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The teachings of the present invention can be readily
understood by considering the following detailed description in
conjunction with the accompanying drawings, in which:
[0014] FIG. 1 shows a simplified side cross sectional view of a one
embodiment of fountain plater of the present invention;
[0015] FIG. 2 shows a schematic diagram of one embodiment of power
supply of the present invention that may be used with the fountain
plater of FIG. 1;
[0016] FIG. 3 shows a schematic diagram of an individual conductor
with a feedback portion 242 of FIG. 2 of one embodiment of the
present invention;
[0017] FIG. 4 shows a side cross sectional view of a wafer holding
fixture of one embodiment of the present invention;
[0018] FIG. 5 shows an expanded view of the elements within portion
410 of FIG. 4;
[0019] FIG. 6, comprising of FIGS. 6A to 6I, shows a cross
sectional view of one embodiment of a contact substrate fabrication
progression; and
[0020] FIG. 7 shows a top view of one embodiment of compliant
ridge.
[0021] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures.
DETAILED DESCRIPTION
[0022] After considering the following description, those skilled
in the art will clearly realize that the teachings of this
invention can be readily utilized in any metallic deposition
application, such as electroplating.
[0023] 1. Component Structure
[0024] A fountain plater 10 comprises an electrolyte container 12,
an anode 16, a power supply 22, a contact ring 20, a plurality of
contacts 56, and a wafer support 14. The electrolyte container 12
contains an electrolyte used to deposit metal upon a substrate such
as a wafer. A wafer 48 is fixed to the wafer support 14 and then is
inserted into the electrolyte in container 12 for depositing metal
thereupon. A copper layer is deposited by electroplating from a
copper containing electrolyte onto areas of the wafer 48 that have
typically previously been covered by a previously formed copper
seed layer. FIG. 2 depicts a power supply 22 of one embodiment of
the present invention that senses and controls electrical current
supplied to contacts 56 located in the fountain plater 10 shown in
FIG. 1. Even though the fountain plater 10 is shown and described
relative to the present disclosure, any process chamber comprising
contacts 56 that deposits metal on a wafer or other substrate is
intended to be within the scope of the present invention.
[0025] In FIG. 1, the contacts 56 are electrically coupled to an
electric power supply 22. Any contact structure that contacts a
seed layer disposed on a substrate is within the intended scope of
the term "contacts" as used within this disclosure (e.g., contact
comprise contact rods and contact pins, as well as other known
contact structures). The fountain plater 10 includes an electrolyte
container 12 into which the wafer 48 attached to wafer support 14
can be disposed through an opening 13. An anode 16 is disposed near
the bottom of the electrolyte container 12. A contact ring 20 is
configured to maintain the wafer in position such that electricity
may be supplied from the contacts 56 located in the contact ring
20. The wafer support 14 is supported by edges of opening 13 to
form an enclosure 21 containing electrolyte solution. The circular
electrical contact ring 20 facilitates electrical contact with the
seed layer (not shown) disposed on the wafer plating surface 54
formed on the wafer 48. A portion of the seed layer includes a seed
layer contact portion preferably positioned near the periphery of
the wafer 48. This location of the seed layer provides an effective
contact with contacts 56. An input source and output source for
electrolyte solution (neither of which are shown) are connected to
the electrolyte container 12 to respectively provide, and drain,
electrolyte solution to, and from, the electrolyte container
12.
[0026] Typically, the contacts 56 are formed from materials, or
alloys, including conductive material such as tantalum (Ta),
titanium (Ti), platinum (Pt), gold (Au), copper (Cu), or silver
(Ag). The portion of the contacts 56 that are located inside of the
contact ring 20, are configured to minimize the electrical field
generated thereby (and mechanical binding effects of the contacts
56) on the wafer 48. The wafer 48 is secured within and located on
top of the cylindrical electrolyte container 12 that axially
conforms to the shape of the wafer 48. Electrolyte flow impinges
perpendicularly on a wafer plating surface 54 of the wafer 48
during operation of the fountain plater 10.
[0027] During operation, the wafer 48 interacts with the anode 16
as a cathode, and may be considered as a work-piece having a metal
controllably layered thereupon. Typically, the contact ring 20
comprises a plurality of metallic or semi-metallic contacts 56. If
a contact 56 is exposed to the electrolyte, the seed layer will
accumulate plating deposits. Deposits on the contacts 56 change
their physical, electrical, and chemical characteristics and
eventually degrade the electrical performance of the contact ring
20. Such degradation results in uneven plating on the wafer due to
non-uniform current distribution.
[0028] FIG. 2 depicts a power supply 22 of one embodiment of the
present invention associated with fountain plater 10. This
embodiment provides a design for the power supply that supplies
power to individual contacts in which the electric currents
supplied among the different contacts 56 are balanced even if the
resistance of each contact 56 differs. The power supply 22 provides
a more uniform electric current density (and application of
electric current density) to the seed layer, even in those
instances that contacts 56 have unequal resistances. An individual
conductor with feedback portion 242 connects each contact 56
individually to a controller 204. Each individual conductor with
feedback portion 242 senses the electric current being applied to
its particular contact 56, and provides input to the controller 204
indicative of the electric current. The controller relies upon this
sensed electrical current to balance the electric current between
the different contacts 56 (if necessary), as described below.
[0029] The structure of one embodiment of an individual conductor
with a feedback portion 242 associated with power supply 206 and
controller 204 is shown in detail in FIG. 3. The individual
conductor with a feedback portion 242 comprises power conductors
702, 704, and 708; a varistor (variable resistor) 706; a current
sensor 710; and control conductors 712 and 714. The power conductor
702 supplies sufficient electric current from the power supply 206
to the controller 204 to satisfy the electrical and electronic
requirements for the operation of the controller 204 and the
fountain plater 10. Power conductors 704 and 708 (with varistor 706
interspaced therebetween) provide controlled electric power from
the controller 204 to the contact 56 in the fountain plater 10. The
current sensor 710 determines the current flowing through the power
conductor 708, and transmits this information (preferably in
digital form) back to the controller 204.
[0030] A current regulator portion 720 of the controller 204
provides a control signal to varistor 706. The varistor responds by
increasing, or decreasing the its resistance that controls the
electric current supplied to the contact 56 if the contact is
receiving respectively more or less current than other contacts.
That the varistors 706 associated with the different individual
feedback portions 242 should function in an integrated fashion.
Nearly identical electric currents will then be applied from each
individual conductor with feedback portion 242 to their respective
contact 56.
[0031] In one embodiment, the electrical current applied to every
individual contact 56 may be reduced by the amount that the
electric current to that individual contact exceeds the electric
current supplied to the particular contact in the fountain plater
that is receiving the least electric current. This reduction in
electric current may result from increasing the resistance in the
varistor 706 by a suitable amount, as determined by controller 204.
The controller 204 operates continuously such that the relative
resistance levels in the varistors 706 continuously regulate the
electrical current supplied to the contacts.
[0032] In an alternate embodiments, the electric current supplied
by the controller 204 to those contacts 56 that receive less
electric current than other contacts may receive more electrical
current by increasing a current supplied by current regulator (not
shown) located in controller 204. Alternately, controller 204 may
decrease the electric current supplied by the controller 204 to
those contacts 56 that are receiving more electrical current than
other contacts 56. Any technique by which electric currents
supplied to different contacts 56 are varied based upon the sensed
electric currents applied to those contacts 56 (to balance the
electric current applied between the multiple contacts) is within
the intended scope of this invention.
[0033] Operationally, controller 204 may be viewed as including two
portions, the current sensor portion and the current regulator
portion. Each of these two portions is not depicted separately in
the figures since their operation is related and involves so much
of the same equipment. The controller 204 comprises central
processing unit (CPU) 210, memory 212, input/output circuits (I/O)
214, circuit portion 216, and system bus 218. The controller 204
may be fashioned as a personal computer (PC), a microcomputer, a
networked-computer, a mainframe, a microprocessor, or any other
known type of computer, the operations of which is generally known
in the art and will not be further detailed herein for brevity.
[0034] The CPU 210 performs the processing and arithmetic functions
of the controller 204. The CPU 210 is preferably a type such as
produced by Intel Corporation, Texas Instruments, or Advanced Micro
Devices, and whose operation is known to those skilled in the art.
The memory 212 includes random access memory (RAM and read only
memory (ROM) that together store, and access, the programs,
operands, system parameters, and other necessary parameters for
controlling the operation of the power supply 22. System bus 218
provides for transmission of digital information between the CPU
210, the memory 212, the support circuits 216, and the I/O circuits
214. The bus 218 also transmits the necessary information between
the elements CPU 210, memory 212, I/O circuits 214 and support
circuits 216 that the bus 218 is connected to with fountain plater
10.
[0035] The I/O circuits 214 provide an interface to control the
transmission of digital information between each of the components
in the controller 204. The I/O circuits 214 also provide an
interface between the components of the controller 204 and
different portions of the fountain plater 10. The support circuit
portion 216 comprises all of the other user interface portions
(such as display and keyboard), system devices, and additional
devices associated with the controller 204. While the controller
204 is described as a digital device, it is within the scope of the
present invention that an analog device that performs similar
functions is also within the intended scope of the present
invention. Also shown in FIG. 2 is a current regulator 250 that
controls the electric current supplied from power supply 206 to the
anode 16.
[0036] Such interconnections between the controller 204 and the
contacts 56 can be fabricated using known fabrication techniques
involving single or multi-layer thin film wiring methods on
appropriate wafers.
[0037] 2. Manufacture of Wafer Contacts
[0038] A manufacturing process that uses contact ring 20 of the
type used in the FIG. 2 embodiment is now described. This
embodiment of manufacturing provides for contacts 56, which lends
to the fabrication of the necessary wiring structures that compares
the current flowing into the individual contacts. This embodiment
provides a configuration of electrical contacts that permit the
re-balancing of electrical currents between the different contacts
56, as described above.
[0039] The wiring network and the contacts 56 can be fabricated as
a metal network. The preferred metal is a copper-beryllium alloy
that is available in strip form and widely used in electrical
contacts due to the high spring factor, good formability, and
relatively high electrical conductivity. One example of the method
of fabrication is illustrated in FIG. 6, which comprises FIGS. 6A
to 6I.
[0040] In FIG. 6A, the contact ring 20 (preferably made from
beryllium-copper) is deburred, and the contact ring 20 is
electroplated with nickel having a thickness of5 .mu.m.
[0041] In FIG. 6B, a 15-20 .mu.m polyimide coat 604 covers both the
sides and the edges of the contact ring 20. Polyimides are well
known for their use as dielectrics, though any other dielectric
that can be applied in the manner described below is intended to be
within the scope of the present invention. The wafer is then cured
at 300 to 400 degrees Celsius.
[0042] In FIG. 6C, a Cr--Cu--Cr sputter layer 606 is applied to the
upper surface of the contact ring 20. The inner chromium layer is
provided as a protective layer to limit adverse affects to the
copper layer. The copper layer is provided as the conductive layer,
and the outer chromium layer is provided as another protective
layer. The protective chromium layer(s) may be removed while
remaining within the intended scope of the present invention. The
Cr--Cu--Cr sputter layer 606 shown in FIG. 6C includes about 200
Angstroms Chromium, about 10-25 .mu.m copper, and then about 200
Angstroms Chromium. The 10-25 .mu.m of copper is relatively thick
compared to existing fabrication techniques, and provides for a
build-up, or compliant ridges 470, in latter fabrication layers, as
shown in FIG. 5. The chromium in the Cr--Cu--Cr sputter layer 606
is provided as a protective layer that limits oxidation of the
copper.
[0043] In FIG. 6D, photo-resist (not shown) is then applied to the
wafer to begin the process of selectively removing the Cr--Cu--Cr
sputter layer 606. The photo-resist is then soft baked. The
photo-resist may be either a positive or a negative photo-resist,
as desired. The photo-resist is then exposed, using mask 608, to
define the first wiring level. In FIG. 6E, a subtractive etch layer
(one embodiment of which comprises ammonium persulfate) is applied
to remove those portions of the Cr--Cu--Cr sputter layer 606 that
have not been protected by the photo-resist. The subtractive etch
portion, other etching techniques may also be used, (using plasma
etching, reactive ion etching, liquid etching, or other suitable
techniques) is thus returned to the polyimide layer.
[0044] In FIG. 6F, photosensitive polyimide (PSPI) 612 is then
applied and soft baked. The PSPI is then exposed, developed, and
cured. Polyimide is an electrical dielectric. The steps illustrated
in FIGS. 6C to 6F are then repeated in FIG. 6F to provide as many
conductive wiring layers 614, 616, between the successive layers of
polyimide, as desired. In FIG. 6G, the portions of the
photosensitive polyimide that are removed at 618, in FIG. 6F during
the exposing and processing portions provide for vias to lower
layers, if necessary. The multiple layers may be utilized to
provide a multi-layer conductive configuration as indicated in FIG.
6G.
[0045] In FIG. 6H, a laser is used to ablate a contact hole 650
through the multiple layers down to, but not including, the
polyimide coat layer 604 shown in FIG. 6B. This process provides
for a contact 56 extending to the polyimide coat layer 604. In FIG.
61, contacts 56, preferably formed from platinum, are electroplated
into the contact holes 650 produced in FIG. 6H.
[0046] A benefit of the method depicted in FIGS. 6A to 6G is that
compliant ridges 654 are formed surrounding each contact 56. The
compliant ridges 654, when compressed as shown in FIGS. 4 and 5,
seal the contacts 56 from the electrolyte solution contained in the
enclosure 21 of the electrolyte container 12 of FIG. 1. In one
embodiment of the present invention, coating thick (25 .mu.m)
copper features in the Cr--Cu--Cr sputter layer 606 forms the
compliant ridges 654 as shown in FIG. 6C. The compliant ridges
surround the contact as shown in FIG. 7. This surface topography
can be engineered to provide compressible compliant ridges or dams
654 that are raised compared to the surrounding surface due to the
thicknesss of the Cr--Cu--Cr layer. The raised compressible
compliant ridges or dams extending around the contacts 652 "pinch
off" exposure of the plating solution to the contacts 56 when the
compliant ridges contact and are compressed against the substrate
48. FIG. 7 shows the top view of the compliant ridges 652 that
extend above surrounding land 702 and interior land 704. The
interior land 704 comprises contact 56. The compressible compliant
ridges 654 can be made highly reproducible using the
above-described thin film process. This sealing of the contacts 56
from the electrolyte limits coating of the contacts 56 by metal
contained in the electrolyte. The sealing of the contacts also
extends the life of the electrolyte because the electrolyte does
not chemically interact with the material of the contacts 56. This
sealing of the contacts from the electrolyte makes the electrical
characteristics between the different electrical contacts 56
uniform and predictable since the contacts will maintain their
original material and configuration longer. In an alternate
embodiment of the present invention, the compliant ridges 654 are
formed by adding an additional layer of polyimide around a
periphery of the contacts 56. This alternate embodiment does not
rely upon using a thicker Cr--Cu--Cr sputter layer 606:
[0047] FIGS. 4 and 5 show an alternate, and more detailed
embodiment, of a wafer support 400 that fits within the electrolyte
container 12. The wafer support 400 supports the wafer 48 such that
the wafer plating surface 54 is exposed to electrolyte solution
contained in the enclosure 21 defined by the container 12. The
contact ring 20 (shown in cross section in FIGS. 4 and 5) is
attached to an annular support member 424 by insulative fasteners
425, e.g. bolts or screws, formed from a plastic or other
corrosion-resistant material. Wafer support 14, shown in FIG. 1,
engages and is supported by surfaces 426 formed in the annular
support member 424. A plurality of the contacts 56 are spaced about
the periphery of the contact ring 20, and supplies electricity to
seed layer (not shown) found on wafer plating surface 54.
[0048] FIG. 5 shows an expanded view of the elements within a
portion 410 of FIG. 4. Dielectric polyimide layer 460 structurally
supports the contacts 56. There are multiple electric conductive
layers 462 disposed within the dielectric polyimide layers 460. The
contacts 56 supply electricity to seed layer that is positioned on
the wafer plating surface 54. Compliant ridges 470 (the outer layer
is formed from the dielectric polyimide layer 460 in one
embodiment) engage wafer plating surface 54 around the periphery of
the contacts 56. The compliant ridges limit electrolyte solution
from passing from the chamber 422 to the contacts 56. This limiting
of exposure of contacts 56 to the electrolyte solution extends the
practical life of the contact ring and the electrolyte
solution.
[0049] The pressure applied to the back of the contact ring 20 is
sufficient to flatten the compliant ridges 654 formed around the
contacts 652 as described. Such flattening of the compliant ridges
654 enables establishing robust electrical connections to each
contact 56. The contact ring 20 is applied with sufficient force to
flatten the compliant ridges 654 around the contact holes 650 and
thereby bias the contacts 652 against the wafer. This force
provides consistent sealing action that limits fluid passage
between the contacts 56 and the seed layer formed on the wafer
plating surface 54 of contact ring 20.
[0050] The structure of the contact ring 20, including the contacts
56 and the compliant ridges, can also be formed in an alternate
embodiment as a flexible circuit with polyimide as the interlayer
dielectric layer using known flex circuit manufacturing methods. An
example of such flex circuit manufacturing methods are depicted in
U.S. Pat. No. 5,885,469 that issued on Mar. 23, 1999 to Kholodenko
et al., and assigned to the owner of the present invention
(incorporated herein by reference). Such a flex circuit can be
attached to the rigid body of the plating fixture by gluing (and
possibly curing in an autoclave), or alternatively by suitable
fasteners. In the latter case, the inexpensive flex circuit can be
used as a replaceable contact circuit in plating cells. Polyimides
have generally very good resistance to attack in acidic plating
solutions. Other polymeric dielectric can be substituted for
polyimide.
[0051] Although various embodiments that incorporate the teachings
of the present invention have been shown and described in detail
herein, those skilled in the art can readily devise many other
varied embodiments that still incorporate these teachings.
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