U.S. patent application number 11/399762 was filed with the patent office on 2006-10-12 for die-level wafer contact for direct-on-barrier plating.
This patent application is currently assigned to Semitool, Inc.. Invention is credited to Rajesh Baskaran, Steve L. Eudy, Paul R. McHugh, Raymon F. Thompson, Gregory J. Wilson, Daniel J. Woodruff.
Application Number | 20060226019 11/399762 |
Document ID | / |
Family ID | 37082142 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060226019 |
Kind Code |
A1 |
Thompson; Raymon F. ; et
al. |
October 12, 2006 |
Die-level wafer contact for direct-on-barrier plating
Abstract
The present invention provides a semiconductor workpiece support
and contact assembly for providing localized electrical connections
with the device side of the workpiece. The additional contact
points help overcome the terminal effect caused by very high sheet
resistance of thin barrier layers and enable plating a conformal
seed layer or feature filling directly on thin barrier layers. By
utilizing the streets that separate individual dice on a workpiece
to make electrical connections with the workpiece and provide
localized distribution of plating chemistry, the present invention
provides a more uniform and conformal metallization layer.
Inventors: |
Thompson; Raymon F.;
(Kalispell, MT) ; McHugh; Paul R.; (Kalispell,
MT) ; Woodruff; Daniel J.; (Kalispell, MT) ;
Wilson; Gregory J.; (Kalispell, MT) ; Eudy; Steve
L.; (Kalispell, MT) ; Baskaran; Rajesh;
(Kalispell, MT) |
Correspondence
Address: |
WALLENSTEIN & WAGNER, LTD.
311 SOUTH WACKER DRIVE
53RD FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
Semitool, Inc.
Kalispell
MT
|
Family ID: |
37082142 |
Appl. No.: |
11/399762 |
Filed: |
April 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60669312 |
Apr 7, 2005 |
|
|
|
Current U.S.
Class: |
205/157 ;
257/E21.175; 257/E21.585 |
Current CPC
Class: |
C25D 17/005 20130101;
H01L 21/76877 20130101; H01L 21/76873 20130101; C25D 17/06
20130101; C25D 7/123 20130101; H01L 21/2885 20130101; C25D 17/001
20130101 |
Class at
Publication: |
205/157 |
International
Class: |
C25D 7/12 20060101
C25D007/12 |
Claims
1. A semiconductor contact assembly for use in a semiconductor
electroplating apparatus used to plate a metal or metals onto a
semiconductor workpiece having a plurality of streets, comprising:
an outer continuous shoulder that defines an inner area; a
plurality of conductive contact members connected to the outer
continuous shoulder and extending into the open area to form a
plurality of openings in the inner area; and at least one recess
formed in the outer shoulder.
2. The semiconductor contact assembly of claim 1, wherein the
plurality of conductive contact members lie within a common
horizontal plane.
3. The semiconductor contact assembly of claim 1, wherein the
plurality of openings in the contact assembly are substantially
square shaped.
4. The semiconductor contact assembly of claim 1, wherein the
plurality of openings in the contact assembly are substantially
rectangular shaped.
5. The semiconductor contact assembly of claim 1, wherein the at
least one recess formed in the outer shoulder comprises two opposed
recesses.
6. The semiconductor contact assembly of claim 1, wherein the
plurality of conductive contact members intersect one another to
form a grid.
7. The semiconductor contact assembly of claim 1, wherein the
plurality of conductive contact members comprise a plurality of
discrete contact points.
8. The semiconductor contact assembly of claim 1 further comprising
an electrical connector to provide electrical power to the contact
assembly.
9. The semiconductor contact assembly of claim 1, wherein the
plurality of conductive contact members have a width in a range of
0.5 to 5 mm.
10. The semiconductor contact assembly of claim 9, wherein the
width is in a range of 1 to 2 mm.
11. The semiconductor contact assembly of claim 1 further
comprising a plate for distributing process fluid to the
semiconductor workpiece that rests on the plurality of conductive
contact members.
12. The semiconductor contact assembly of claim 11, wherein the
plate comprises a plurality of spaced apart cells projecting
outwardly from a base, the cells configured to rest within the
openings of the inner area and the space between the cells
configured to receive the conductive contact members.
13. The semiconductor contact assembly of claim 12, wherein each of
the plurality of spaced apart cells has at least one aperture.
14. The semiconductor contact assembly of claim 13, wherein each of
the plurality of spaced apart cells has a plurality of
apertures.
15. A semiconductor support and contact assembly for use in plating
a semiconductor workpiece having a plurality of microelectronic
devices formed on one side, the plurality of microelectronic
devices being separated from one another by streets, the
semiconductor support and contact assembly comprising a plurality
of point contacts provided on a frame having a plurality of
openings, whereby upon placing the workpiece on the semiconductor
support and contact assembly the plurality of point contacts make a
plurality of electrical connections with the semiconductor
workpiece along the streets.
16. An apparatus for plating a metal onto a semiconductor
workpiece, comprising: a bowl assembly adapted to hold a plating
fluid; an anode positioned in the bowl assembly; a contact assembly
located in the bowl assembly, the contact assembly having a frame
that defines an inner area and a plurality of conductive contact
members connected to the frame and forming a plurality of openings
in the inner area; and a process head for placing the semiconductor
workpiece onto the contact assembly.
17. The apparatus of claim 16 further comprising a plate having a
plurality of apertures for distributing the plating fluid to the
semiconductor workpiece.
18. The apparatus of claim 16, wherein the contact assembly
comprises a plurality of discrete contact points for making an
electrical connection with the semiconductor workpiece.
19. The apparatus of claim 16 wherein the bowl assembly comprises a
bowl having an inlet and outlet port for selectively introducing a
electrolyte into the bowl.
20. The apparatus of claim 19, wherein a membrane divides the bowl
into first and second compartments.
21. The apparatus of claim 16 further comprising a power supply for
selectively powering the plurality of conductive members.
22. The apparatus of claim 16, wherein the workpiece has a
plurality of streets and the contact members are electrically
connected to the streets.
23. The apparatus of claim 22, wherein conductive members are
positioned within the streets and the contact assembly is in
electrical contact with the conductive members of the streets.
24. The apparatus of claim 16, wherein a portion of the contact
members are covered with a material resistant to electrochemical
plating.
25. A method for plating a metal onto a surface of a semiconductor
workpiece, comprising: providing a semiconductor workpiece having a
plurality of microelectronic devices and streets formed on one side
thereof; placing the semiconductor workpiece on a contact assembly
having a plurality of conductive members wherein the conductive
members contact the semiconductor workpiece at one of the streets;
applying a plating bath fluid to the one side of the semiconductor
workpiece; and electroplating a metal onto the semiconductor
workpiece by passing electrical current through the plurality of
conductive members and between the semiconductor workpiece and the
contact assembly.
26. The method of claim 25, wherein the contact assembly comprises
a contact plate and a plate for distributing the plating bath fluid
to the one side of the semiconductor workpiece.
27. The method of claim 26, wherein the contact plate and the fluid
distribution plate are generally co-planar.
28. The method of claim 25, wherein the contact members lie within
a common horizontal plane.
29. The method of claim 25, wherein electrical current is passed
through some but not all of the conductive members.
30. The method of claim 25, wherein the contact assembly is
comprised of a contact plate having a plurality point contacts and
a plurality of openings.
31. The method of claim 30, wherein the contact further comprises a
plate having a plurality of apertures for distributing the plating
bath fluid to the one side of the semiconductor workpiece.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a nonprovisional of U.S. Provisional
Patent Application No. 60/669,312, filed Apr. 7, 2005, now pending.
Priority to this application is claimed under 35 U.S.C.
.sctn..sctn. 119, and the disclosure of this application is
incorporated herein by reference in its entirety.
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] None.
TECHNICAL FIELD
[0003] The invention relates to a workpiece support used in
semiconductor plating systems having electrodes which engage the
workpieces for electroplating metals, such as copper and others,
onto seed, barrier and other layers formed on semiconductor wafers
and other semiconductor workpieces.
BACKGROUND OF THE INVENTION
[0004] In the production of semiconductor wafers and other
semiconductor articles it is necessary to plate metals onto the
semiconductor surface to provide conductive areas which transfer
electrical current. There are two primary types of plating layers
formed on the wafer or other workpiece. One is a blanket layer used
to provide a metallic layer which covers large areas of the wafer.
The other is a patterned layer which is discontinuous and provides
various localized areas that form electrically conductive paths
within the layer and to adjacent layers of the wafer or other
device being formed. Plating can occur on a flat metal layer,
through a non-conducting mask to an underlying metal layer or onto
a patterned non-flat substrate.
[0005] There are a wide range of manufacturing processes that may
be used to deposit the metallization on the workpiece in the
desired manner. Such processes included chemical vapor deposition
("CVD"), physical vapor deposition ("PVD"), electroplating, and a
damascene process where holes, more commonly called vias, trenches
and other recesses are formed in the layer of semiconductor
material in which a pattern of copper is desired. In the damascene
process the wafer is first provided with a metallic seed layer
which is used to conduct electrical current during a subsequent
metal electroplating step. The seed layer is a very thin layer of
metal which can be laid down using several processes. The seed
layer of metal can be laid down using PVD or CVD processes to
produce a layer on the order of 1000 angstroms thick. The seed
layer can advantageously be formed of copper, gold, nickel,
palladium, and most or all other metals. The seed layer is formed
over a surface which is convoluted by the presence of vias,
trenches, or other device features which are recessed. This
convoluted nature of the exposed surface provides increased
difficulties in forming the seed layer in a uniform manner.
Non-uniformities in the seed layer can result in variations in the
electrical current passing from the exposed surface of the wafer
during the subsequent electroplating process. This in turn can lead
to non-uniformities in the blanket layer electroplated onto the
seed layer. Such non-uniformities can cause deformities and
failures in the resulting semiconductor device being formed.
[0006] In the damascene processes, after the seed layer is laid
down, then it is typical to plate additional metal (e.g., copper)
onto the seed layer in the form of a blanket layer formed thereon.
The blanket layer is typically electroplated and is used to fill
the vias and trenches. The blanket layer is also typically plated
to an extent which forms an overlying layer. Such a blanket layer
will typically be formed in thicknesses on the order of
3,000-15,000 angstroms (0.3-1.5 microns). Chemical mechanical
polishing ("CMP") is used to remove any excess copper and other
metal above the features.
[0007] As damascene-interconnect feature sizes shrink, the barrier
layer and seed layers used for manufacturing device metal
interconnects (i.e. the dual-damascene process) become thinner and
more resistive. Furthermore, it becomes more difficult to provide a
uniform seed-layer thickness on the sidewalls of features as the
features shrink. The seed layers are typically deposited using
relatively expensive PVD vacuum processes and it may be necessary
to improve the sidewall coverage by using a process such as the
"seed layer repair" and "seed layer enhancement" processes
developed by Semitool and disclosed in U.S. Pat. No. 6,197,181. It
would be of great benefit to plate the seed layer directly on the
barrier in a conformal manner, thereby, insuring good sidewall
coverage and omitting the expense of the PVD process
altogether.
[0008] To plate directly on a thin barrier layer, the very strong
terminal effect created by the high sheet resistance must be
overcome. This is very challenging when contacting the wafer around
its circumference because a high voltage is required to pass
current from the contact to the center of the wafer in order to
plate at the center. The current will preferentially plate near the
contact to avoid the sheet resistance. An electrolytic bath with a
low conductivity reduces the terminal effect, but untested ultra
low conductivity bath formulations (less than 1 mS/cm.sup.2 and
down to 0.001 mS/cm.sup.2) would be required to enable relative
uniform plating on the barrier layers expected below 45 nm feature
sizes.
[0009] Moreover, the difficulty of plating on a barrier layer (or
seed layer) is aggravated when the layer covers features on the
surface of the wafer. In general, these features increase the
effective length of the conductive film and, thus, increase the
film sheet resistance compared to a blanket film. Typically these
features are via and trench geometries (e.g. dual-damascene
features) to be filled with copper to form metal interconnects. But
not only do the features add to the overall sheet resistance, they
can also create regions of anisotropic sheet-resistance making some
areas of the wafer extremely difficult to plate. For example, the
barrier layer covering trenches aligned with the current flow (e.g.
along radial lines) will be less resistive than trenches
perpendicular to the current flow. In addition, there may be
underlying layers or pads that are more conductive than the barrier
layer or seed layer connecting various features that are to be
plated. For example, one via array may be connected to another via
array by such an underlying structure. This conductive structure
can shunt current and influence local plating voltages, thereby,
disrupting the plating on the barrier layer. Accordingly, there is
a need for electroplating equipment and methods that overcome the
challenges inherent in plating highly resistive barrier and seed
layers.
[0010] The present invention is provided to solve the problems
discussed above and other problems, and to provide advantages and
aspects not provided by prior electroplating equipment and methods
of this type. A full discussion of the features and advantages of
the present invention is deferred to the following detailed
description, which proceeds with reference to the accompanying
drawings.
SUMMARY OF THE INVENTION
[0011] The present invention proposes mechanical schemes to
increase the contact points across a semiconductor workpiece in an
electroplating vessel, rather than (or in addition to) contacting
the wafer around its circumference as is the case in typical
electroplating equipment and processes. By utilizing the gaps
called "streets" or "scribes" that separate the individual dice on
a wafer, it is possible to contact or touch the wafer in these
streets without harming the devices on the wafer. The additional
contact locations help to overcome the terminal effect caused by
the very high sheet resistance of thin barrier layers and enable
plating a conformal seed layer or feature filling directly on thin
barrier layers.
[0012] In some embodiments of the present invention, the contact to
the wafer approaches the die or device level in order to provide
localized plating in an electrochemical plating vessel. For
example, in one embodiment the present invention provides a wafer
support for use in electroplating a semiconductor workpiece. The
wafer support comprises a plurality of discrete contacts that make
point contacts at selected points with the streets of the wafer.
The discrete point contacts may contact the wafer at each corner of
a die (or less frequently). In another embodiment of the present
invention, continuous contacts may run along the entire length of
the streets formed between the devices formed in the semiconductor
wafer. The contacts may run along only the vertical streets or the
horizontal streets, or may run along both directions forming a
grid-like support structure. In any of these embodiments, the
circumference/periphery of the semiconductor workpiece may (or may
not) also be electrically contacted.
[0013] Since a plurality of discrete contact points or a grid-like
contact structure may disrupt the electrolyte flow and mass
transfer to the wafer when it is added to a conventional fountain
plater, another aspect of the present invention combines the street
contacts with a sparger flow system. Such a system allows for
device-scale delivery and removal of process fluid, and local
control of the current to each die from the anode.
[0014] To eliminate the die-specific nature of the contact geometry
associated with a certain aspects of the present invention, an
alternative embodiment of the present invention provides for
relatively high conductivity current paths (e.g., bus paths) to be
formed or imbedded in the streets. Thus, even when a conventional
circumferential contact is used, the highly conductive streets
provide a low resistance path around each die, effectively
achieving the same result as contacting the wafer locally around
each device.
[0015] Even more uniform barrier and seed layer plating may be
achieved by coupling the localized die-level contact schemes
discussed above with localized plating. For example, local die
level anode shapes (or smaller) may be moved and/or controlled to
enable better die scale plating. By locally plating one die at a
time, the terminal effect is reduced because the overall current
passing though the barrier at a given time is reduced and the
voltage variations throughout the film are correspondingly reduced.
Similarly, localized/dynamic control of the individual contacts
across the streets or the circumference can create more controlled
localized plating. For example, only a portion of the
circumferential or street contacts may be active at a certain time.
This dynamic control could be cycled around the wafer creating
varying current flow directions and potential drops across the
wafer to overcome the effects of anisotropic sheet-resistance and
shorting by underlying conductive pads.
[0016] Other features and advantages of the invention will be
apparent from the following specification taken in conjunction with
the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] To understand the present invention, it will now be
described by way of example, with reference to the accompanying
drawings in which:
[0018] FIG. 1 is a sectional view of a semiconductor processing
station having a processing head, a workpiece support assembly and
a plating bowl assembly.
[0019] FIG. 2 is a sectional view of the semiconductor processing
station shown in FIG. 1 just after the processing head has placed
the workpiece onto the workpiece support assembly.
[0020] FIG. 3A is a sectional view of the workpiece support
assembly and plating bowl assembly with a semiconductor workpiece
resting on the workpiece support assembly.
[0021] FIG. 3B is an expanded partial view of the area identified
by reference letter A in FIG. 3A.
[0022] FIG. 4A is a sectional view of the workpiece support
assembly and plating bowl assembly with arrows showing the
processing fluid flow paths through the workpiece support assembly
and the bowl assembly.
[0023] FIG. 4B is a expanded partial view of the area identified by
reference letter B in FIG. 4A with arrows showing the processing
fluid flow paths through the workpiece support assembly.
[0024] FIG. 5 is a plan view of the workpiece support assembly and
plating bowl assembly shown in FIG. 3A
[0025] FIG. 6A is a cross-sectional view taken along line C-C of
the workpiece support assembly and plating bowl in FIG. 5.
[0026] FIG. 6B is an expanded partial view of the area identified
by reference letter D in FIG. 6A.
[0027] FIG. 7 is the cross-sectional view of FIG. 6A with a partial
semiconductor workpiece resting on the workpiece support
assembly.
[0028] FIG. 8 is an exploded view of the workpiece, wafer support
contact plate and sparger plate according to the present
invention.
[0029] FIG. 9A is a perspective view of a wafer support contact
plate according to one embodiment of the present invention.
[0030] FIG. 9B is a plan view of the wafer support contact plate
shown in FIG. 9A.
[0031] FIG. 9C is a cross-sectional view taken along line A-A of
the wafer support contact plate shown in FIG. 9B.
[0032] FIG. 9D is an expanded view of the detailed section labeled
B in FIG. 9C.
[0033] FIG. 10A is a perspective view of a wafer support contact
plate according to another embodiment of the present invention.
[0034] FIG. 10B is a plan view of the wafer support contact plate
shown in FIG. 10A.
[0035] FIG. 10C is a cross-sectional view taken along line A-A of
the wafer support contact plate shown in FIG. 10B.
[0036] FIG. 10D is a expanded view of the detailed section labeled
B in FIG. 10C.
[0037] FIG. 11 is a plan view of a wafer support contact plate
according to another embodiment of the present invention.
[0038] FIG. 12 is a plan view of a wafer support contact plate
according to another embodiment of the present invention.
[0039] FIG. 13 is a perspective view of a device side of a
semiconductor workpiece with high conductivity current paths formed
in the streets formed between the devices on the workpiece.
[0040] FIG. 14A is a is a perspective view of a sparger plate to be
used in a plating apparatus according to another aspect of the
present invention.
[0041] FIG. 14B is a plan view of the sparger plate shown in FIG.
14A.
[0042] FIG. 14C is a cross-sectional view taken along line A-A of
the sparger plate shown in FIG. 14B.
[0043] FIG. 14D is a expanded view of the detailed section labeled
B in FIG. 14C.
DETAILED DESCRIPTION
[0044] While this invention is susceptible of embodiments in many
different forms, there is shown in the drawings and will herein be
described in detail preferred embodiments of the invention with the
understanding that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not
intended to limit the broad aspect of the invention to the
embodiments illustrated.
[0045] Turning to FIGS. 1 and 2, there is shown a semiconductor
processing station 10 incorporating features of the present
invention. The processing station 10 is comprised of four main
components; a process head 15, a bowl assembly 20, a semiconductor
workpiece contact assembly 25 and a process head operator 30. The
bowl assembly 20 is generally comprised of a bowl 22 positioned
within an outer receptacle 21. The bowl 22 shown in FIG. 1 is
divided by a membrane 23 into an upper section 24 and a lower
section 26. An anode 27 is positioned at the bottom of the lower
section 26 of the bowl 22 and is in fluid communication with a
process fluid, e.g., an electrolyte or anolyte. The lower section
26 has a process fluid inlet 28 and a process fluid outlet 29. The
upper section 24 of the bowl 22 has a process fluid inlet 31.
[0046] The workpiece contact assembly 25 sits atop the bowl 22 and
is generally comprised of a contact plate 32 which supports the
workpiece and a sparger plate 33 for distributing process fluid to
the device side of the workpiece. Appropriate electrical
connections are made with the contact assembly 25 to provide
controlled electrical power to the contact assembly 25. Various
embodiments of the workpiece contact assembly 25 will be discussed
in greater detail below.
[0047] The process head assembly 15 accepts the workpiece W for
processing and introduces the workpiece to the bowl assembly 20 by
placing the workpiece onto the contact plate 32 for processing, and
removes the workpiece W from the bowl assembly 20 after processing
for transition to, for example, another processing station. The
process head assembly 15 is comprised of a process head 34 and a
rotor 35. The process head 34 holds a rotor drive assembly (not
shown) which includes, among other components, a motor for spinning
the process head assembly about the axis R. The process head 34
also includes an actuator that cooperates with components in the
rotor 35 which cause fingers 36, which extend outwardly from the
face of rotor 35, to engage and disengage from the periphery of the
workpiece W.
[0048] The process head assembly 15 is preferably supported by
process head operator 30. The operator 30 includes a linear drive
37 which is used to adjust the height of the process head assembly
15 with respect to the bowl assembly 20. The process head assembly
15 also includes a head rotor drive 38 which operates to rotate the
process head assembly 15 about a horizontal axis H. The rotational
movement of the process head assembly 15 allows it to be placed in
a first position (approximately 180 degrees from the position of
the process head assembly shown in FIG. 1) for loading and
unloading the workpiece W and a second position (shown in FIG. 1)
wherein the device side of the workpiece W is exposed and available
for making contact with the contact assembly 25, which is
positioned atop of the bowl 22. A variety of drives which provide
linear and/or rotational drive movement are suitable for use in a
plating system according to the present invention.
[0049] FIG. 1 illustrates the processing station 10 after the
process head assembly 15 has accepted the workpiece W and the
process head operator 30 has started to lower the workpiece into
the bowl assembly 20. In FIG. 2, the process head assembly 15 has
been completely lowered into the bowl assembly 20 such that the
workpiece W rests on the contact assembly 25 with the device side
of the workpiece W contacting the contact plate 32. As shown in
FIG. 2 and discussed in detail below, the contact plate 32 has at
least one and preferably a plurality of recesses 42 which allow
clearance for the fingers 36 of the rotor 35. In this position, the
device side of the workpiece W is exposed such that the contact
plate 32 makes electrical contact with the workpiece W along the
"streets" or "scribes" that separate the individual dice on a
wafer. After all processing steps, the devices on the wafer are
separated by cutting along these streets. Therefore, it is possible
to contact or touch the wafer in these streets without harming the
devices on the workpiece W. This position also allows the sparger
plate 33 to locally deliver a plating chemistry to the device side
of the workpiece W to effectuate a uniform deposition of metal. The
present invention proposes utilizing the gaps called "streets" or
"scribes" In operation, the anode 27 is connected to a positive
potential terminal of a power supply (not shown). In the embodiment
shown in FIGS. 1 and 2, and with reference to FIGS. 4A and 4b, an
anolyte is introduced into the lower compartment 26 through inlet
28. The anolyte flows over the anode and exits the lower
compartment 26 through exit 29. In a preferred embodiment, the
anolyte is recirculated outside the processing station and
re-introduced through the inlet 28. The contact plate 32 is
connected to a positive potential terminal of the power supply. A
catholyte is introduced into the upper compartment 24 through inlet
31. The catholyte is forced up through the sparger plate 33 to
distribute the catholyte to the device side of the workpiece W, and
more specifically to the individual devices formed on the device
side of the workpiece W. The excess catholyte flows outside the
bowl 22 and is caught in the outer receptacle 21 and eventually
drained through a drain 40 located in the bottom of the inner
receptacle 21. FIGS. 4A and 4B illustrate the anolyte flow
(indicated by the arrows labeled A) and the catholyte flow
(indicated by the arrows labeled C). In operation, the power supply
provides an electrical potential difference between the anode and
the workpiece W (due to the electrical connection with the contact
plate 32) which results in a chemical plating reaction at the
device side of the workpiece W in which the desired metal is
deposited.
[0050] It should be understood by those having skill in the art
that the contact assembly 25 of the present invention can be used
in a plating reactor wherein the plating bath is comprised of a
single electrolyte which is introduced into a bowl 22 having only a
single compartment, rather than the multi-compartment bowl 22 and
the use of a catholyte and an anolyte as disclosed in FIGS. 1, 2,
3A, 3B, 4A, 6A and 7. In either embodiment, the chemistries may be
recirculated to the external supply and filtered or supplemented as
needed to maintain chemistry constituent proportions.
[0051] With reference specifically to FIGS. 3A and 3B, there is
shown a cross-sectional view of the bowl assembly 20 and contact
assembly 25 with the semiconductor workpiece W being supported on
the contact assembly 25. FIG. 3B is an expanded partial view of the
area identified by reference letter A in FIG. 3A. The contact plate
32 has a plurality of conductive members 32a, which contact the
streets formed in the device side of the workpiece W. The sparger
plate 33 has a plurality of grooves 33a. The conductive members 32a
of the contact plate 32 sit within the grooves 33a of the sparger
plate 32. Although the conductive members 32a sit slightly above
the sparger plate 32, the contact plate 32 and the sparger plate 33
are generally co-planar as they sit atop the bowl 22.
[0052] The sparger plate 33 and the contact plate 32 will now be
described in greater detail with reference to a preferred
embodiment shown in FIGS. 5-10D. FIG. 5 is a plan view of a
preferred embodiment of the workpiece support and contact assembly
25 and plating bowl assembly 20 shown in FIG. 3A. The contact plate
32 has a continuous shoulder or frame 41. At least one, and
preferably a plurality of, recesses 42 are formed in the shoulder
41. As mentioned above, the recesses 42 allow for clearance of the
fingers 36 of the rotor 35 when the process head assembly 15 is
loading the workpiece onto the contact assembly 25. A plurality of
conductive members 32a extend inwardly from the shoulder 41. The
conductive members 32a lie within a common horizontal plane. In the
embodiment shown in FIGS. 5-10D, the conductive members 32a are
continuous, rail-like, intersecting members that form a grid-like
structure. The intersecting, grid-like structure forms a plurality
of open areas 32b (best shown in FIG. 8). In the preferred
embodiment shown in FIG. 8, the open areas 32b are substantially
square or rectangular shaped. However, the open areas 32b can take
other configurations as well.
[0053] The sparger plate 33 is comprised of a base plate 43 having
a plurality of spaced-apart, hollow cells 44 projecting outwardly
therefrom. Each cell 44 has at least one aperture 44a, and
preferably a plurality of apertures 44a for distributing the
plating chemistry to the device side of the workpiece W. Because
the cells 44 are spaced apart from one another, a groove 33a is
formed between the cells 44. When the contact plate 32 and the
sparger plate 33 are combined, the conductive members 32a of the
contact plate 32 fit within the grooves 33a of the sparger plate 33
so that the sparger apertures 44a are positioned adjacent the
workpiece W and in close proximity to the electrical contacts made
with the workpiece W. As best shown in FIG. 6B, the conductive
members 32a do not completely fill the grooves 33a. Accordingly,
the grooves 33a also act as drain pathways for the plating
chemistry as shown in FIG. 4B. Likewise, the cells 44 of the
sparger plate 33 fit within the open areas 32b of the contact plate
32. In this regard, the sparger plate 33 provides inlet and drain
sections that open upward toward the workpiece W to direct
electrolyte fluid against the workpiece W and drain the fluid from
contact with the workpiece W in a continuous flow manner.
[0054] Referring to FIG. 6B, when the sparger plate 33 and the
contact plate 32 are properly combined in the plating vessel, there
is a generally co-planar relation between the two plates even
though the conductive members 32a extend above the adjacent cell 44
and apertures 44a of the sparger plate 33. In a preferred
embodiment, the distal ends 32c of the conductive members 32a which
make electrical contact with the streets of workpiece W are tapered
to enhance the electrical contact with the workpiece W (see FIG.
9C). Preferably the conductive members 32a have a thickness
slightly less than the thickness of the streets of the workpiece W,
which may be approximately 100 to 250 microns wide. Accordingly,
thickness ranges of the conductive members 32a may be 0.5 mm to 5
mm, and more preferably between 1 and 2 mm so that they fit within
the streets formed in the workpiece W. In an even more preferred
embodiment, with the exception of the tapered distal end or tip
32c, the conductive members 32a are coated or sealed in a suitable
material resistant to plating (e.g., TEFLON or elastomeric material
such as VITON) to withstand the wet and harsh conditions of the
plating bath environment, and prevent plating or thieving on the
contact end or tip 32c. Because plating will take place at an
accelerated rate at the contact point, by sealing the conductive
members 32a and minimizing the contact area by utilizing a tapered
end or tip 32c to make contact with the workpiece W, a more uniform
metallization will occur.
[0055] FIG. 7 shows a partial semiconductor workpiece W resting
device side down on the contact assembly 25. FIG. 8 shows an
exploded view of the workpiece W, contact plate 32 and sparger
plate 33. A typical device side of a semiconductor workpiece W
before plating is shown in FIG. 13. With reference to FIGS. 7, 8
and 13, the conductive members 32a of the contact plate 32 make
electrical contact with the workpiece W at the streets 50. The
microelectronic devices 55, which lie between the streets 50, rest
adjacent the open areas 32b of the contact plate 32. The cells 44
of the sparger plate 33 fit within the open areas 32b and are
adjacent the microelectronic devices 55. When combined, the sparger
plate 33 and contact plate 32 allows for device-scale delivery and
removal of plating fluid, and local control of the current to each
device 55 from the anode 27. A preferred contact plate 32 is
illustrated in FIGS. 9A-9D and a preferred sparger plate 33 is
illustrated in FIGS. 14A-14D.
[0056] The conductive members 32a of the contact plate 32 may take
many different forms in the present invention. Turning to FIGS.
10A-10D there is shown a preferred embodiment of contact plate 32
wherein the conductive members 32a include a plurality of
conductive fingers 32d to make discrete point contacts with the
workpiece W. The fingers 32d are preferably made from a flexible,
conductive material and can flex to adapt to non-uniform surfaces,
ensuring a reliable electrical connection. In this preferred
embodiment, the fingers 32d preferably contact the workpiece W at
the four corners of each die, however, more or less fingers 32d may
be used. For example, only the conductive members 32a that define
four quadrants of the contact plate 32 (see FIG. 12) may include a
plurality of fingers 32d (and may include more than necessary to
contact the corners of the dice that run along the quadrant
boundaries).
[0057] FIGS. 11 and 12 show alternative embodiments of the contact
plate 32 of the present invention. In FIG. 11, the contact plate 32
includes a plurality of continuous conductive members 32a that run
only along the vertical streets (or horizontal streets not shown)
of the workpiece W. The contact plate 32 may have one continuous
conductive member 32a connected at opposite ends to the shoulder 41
(effectively dividing the device side of the workpiece W into two
zones). Or the contact plate may have a plurality of conductive
members 32a (up to the number corresponding to the number of
streets on the workpiece W. FIG. 12 shows two intersecting
conductive members 32a splitting the contact plate 32 into
quadrants. The localized contacts proposed by the present invention
may (or may not) be utilized in conjunction with contacting the
circumference or periphery of the wafer as is typical in
conventional plating apparatuses. However, by creating device level
contact schemes as discussed above, the challenges inherent in
plating highly resistive films can be overcome.
[0058] To eliminate the die-specific nature of the contact geometry
associated with a certain aspects of the present invention, an
alternative embodiment of the present invention provides for
relatively high conductivity current paths (e.g., bus paths) to be
formed or imbedded in the streets. This can be accomplished by
creating conductive streets or electrical bus paths on the
workpiece W. For example, a PVD copper bus line is deposited on the
workpiece W. The bus line may be only within a first layer and
contact to the bus lines is maintained on subsequent layers by
having vias connecting to the bus path. Thus, even when a
conventional circumferential contact is used, the highly conductive
streets provide a low resistance path around each die, effectively
achieving the same result as contacting the wafer locally around
each device.
[0059] In another aspect of the present invention, even more
uniform barrier and seed layer plating may be achieved by coupling
the localized die-level contact schemes discussed above with
localized plating. For example, local die level anode shapes (or
smaller) may be moved and/or controlled to enable better die scale
plating. By locally plating one die at a time, the terminal effect
is reduced because the overall current passing though the barrier
at a given time is reduced and the voltage variations throughout
the film are correspondingly reduced. Similarly, localized/dynamic
control of the individual contacts across the streets or the
circumference can create more controlled localized plating. For
example, only a portion of the circumferential or street contacts
may be active at a certain time. This dynamic control could be
cycled around the wafer creating varying current flow directions
and potential drops across the wafer to overcome the effects of
anisotropic sheet-resistance and shorting by underlying conductive
pads.
[0060] While the specific embodiments have been illustrated and
described, numerous modifications come to mind without
significantly departing from the spirit of the invention, and the
scope of protection is only limited by the scope of the
accompanying Claims.
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