U.S. patent application number 11/051521 was filed with the patent office on 2005-10-20 for plating apparatus and method.
This patent application is currently assigned to Surfect Technologies, Inc.. Invention is credited to Berner, Robert Wayne, Bleck, Martin, Griego, Thomas P., Hannon, Mathew, Minogue, Gerard, Sanchez, Fernando M..
Application Number | 20050230260 11/051521 |
Document ID | / |
Family ID | 34860208 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050230260 |
Kind Code |
A1 |
Bleck, Martin ; et
al. |
October 20, 2005 |
Plating apparatus and method
Abstract
The present invention comprises a metal plating apparatus and
method, particularly suitable for autocatalytic (i.e., electroless)
plating, comprising a pressurized sealable vessel for disposing a
substrate to be plated and for the circulation of plating solutions
wherein temperatures and pressure are highly controllable.
Inventors: |
Bleck, Martin; (Albuquerque,
NM) ; Berner, Robert Wayne; (Kalispell, MT) ;
Minogue, Gerard; (Rio Rancho, NM) ; Sanchez, Fernando
M.; (Albuquerque, NM) ; Hannon, Mathew;
(Albuquerque, NM) ; Griego, Thomas P.; (Corrales,
NM) |
Correspondence
Address: |
PEACOCK MYERS, P.C.
P O BOX 26927
ALBUQUERQUE
NM
87125-6927
US
|
Assignee: |
Surfect Technologies, Inc.
Albuquerque
NM
|
Family ID: |
34860208 |
Appl. No.: |
11/051521 |
Filed: |
February 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60541687 |
Feb 4, 2004 |
|
|
|
Current U.S.
Class: |
205/88 ;
204/242 |
Current CPC
Class: |
C25D 5/003 20130101;
C23C 18/1619 20130101; C25D 17/001 20130101; C25D 7/123
20130101 |
Class at
Publication: |
205/088 ;
204/242 |
International
Class: |
C25D 005/00; C25D
017/00 |
Claims
1. A plating apparatus comprising: a pressurized, sealable vessel;
a controllable plating fluid source linked to said vessel; a
holding apparatus to secure a substrate within said vessel during
plating of the substrate and until the plating of the substrate is
complete; and at least one opening through which one or more
plating fluids pass in and out of said vessel.
2. The apparatus of claim 1 wherein the plating of the substrate
comprises autocatalytic plating.
3. The apparatus of claim 1 wherein the substrate comprises a
semiconductor wafer.
4. The apparatus of claim 1 wherein said linked controllable source
and vessel comprise a closed system.
5. The apparatus of claim 1 further comprising a pressure control
system to control a pressure of said plating fluid within said
vessel to control isostatic pressure.
6. The apparatus of claim 1 wherein said controllable source
comprises a system for the discreet, sequential introduction and
removal of said plating fluids into and from said vessel.
7. The apparatus of claim 6 wherein said system comprises a
plurality of nozzles and conduits.
8. The apparatus of claim 7 wherein said system comprises a
sequentially rotating nozzle system.
9. The apparatus of claim 1 further comprising a temperature
control system.
10. The apparatus of claim 9 wherein said temperature control
system controls a temperature to within approximately .+-.1.degree.
C.
11. The apparatus of claim 9 wherein said temperature control
system heats or cools said plating fluid at a rate faster than
approximately 0.5.degree. C. per second.
12. The apparatus of claim 11 wherein said temperature control
system heats or cools said plating fluid at a rate faster than
approximately 1.0.degree. C. per second.
13. The apparatus of claim 12 wherein said temperature control
system heats or cools said plating fluid at a rate faster than
approximately 2.5.degree. C. per second.
14. The apparatus of claim 9 wherein said temperature control
system is disposed outside of said vessel to affect a temperature
of said plating fluid prior to said plating fluid entering said
vessel.
15. The apparatus of claim 9 wherein said temperature control
system is disposed over said vessel.
16. The apparatus of claim 9 wherein said temperature control
system is disposed in said vessel.
17. The apparatus of claim 16 wherein said temperature control
system is disposed in at least one wall of said vessel.
18. The apparatus of claim 1 wherein said vessel comprises a volume
of less than approximately 5 liters.
19. The apparatus of claim 18 wherein said vessel comprises a
volume of less than approximately 3 liters.
20. The apparatus of claim 19 wherein said vessel comprises a
volume of less than approximately 2 liters.
21. The apparatus of claim 20 wherein a cell of said vessel
comprises a volume of less than approximately 1 liter.
22. The apparatus of claim 21 wherein said vessel comprises a
volume of less than approximately 0.5 liter.
23. The apparatus of claim 1 further comprising a baffle system
disposed within said vessel.
24. The apparatus of claim 1 further comprising a cathode disposed
in said vessel.
25. The apparatus of claim 1 wherein said vessel comprises: a base
plate; and a cover removably disposed on said base plate.
26. The apparatus of claim 1 wherein said holding apparatus
comprises a vacuum chuck.
27. The apparatus of claim 26 wherein said vacuum chuck comprises:
a base; and at least one vacuum cavity in said base.
28. The apparatus of claim 27 further comprising at least one
membrane disposed over said at least one cavity.
29. The apparatus of claim 28 wherein said membrane comprises a
membrane that is deformable in response to a vacuum.
30. The apparatus of claim 29 wherein said membrane comprises an
elastomeric material.
31. The apparatus of claim 27, said vacuum chuck further comprising
a center shuttle disposed in said base.
32. The apparatus of claim 27 further comprising an edge seal boot
disposed on said base.
33. The apparatus of claim 32 wherein said edge seal boot comprises
an edge skirt to contact the substrate and seal a portion of the
substrate.
34. The apparatus of claim 33 further comprising an electric bridge
contact disposed in said edge skirt.
35. The apparatus of claim 34 wherein said electric bridge contact
comprises an array of contacts.
36. A method for depositing metal on a substrate comprising the
steps of: providing a pressurized, sealable vessel; securing the
substrate within the vessel; introducing one or more plating fluids
into the vessel; removing the one or more plating fluids from the
vessel; and removing the substrate from the vessel after the metal
has been deposited on the substrate.
37. The method of claim 36 further comprising; introducing the
plating fluids discreetly and sequentially; and removing the
plating fluids discreetly and sequentially.
38. The method of claim 36 further comprising controlling an
isostatic pressure within the vessel.
39. The method of claim 36 further comprising the steps of:
disposing a cathode in the vessel; and sending an electrical
current to the cathode.
40. The method of claim 36 further comprising controlling a
temperature of at least one of the plating fluids.
41. The method of claim 40 comprising controlling the temperature
to within approximately .+-.1.degree. C.
42. The method of claim 40 comprising heating or cooling at least
one of the plating fluids at a rate faster than approximately
0.5.degree. C. per second.
43. The method of claim 42 comprising heating or cooling at least
one of the plating fluids at a rate faster than approximately
1.0.degree. C. per second.
44. The method of claim 43 comprising heating or cooling at least
one of the plating fluids at a rate faster than approximately
2.5.degree. C. per second.
45. The method of claim 40 further comprising affecting the
temperature of the at least one fluid before introducing it into
the vessel.
46. The method of claim 40 further comprising affecting the
temperature of the at least one fluid inside the vessel.
47. The method of claim 36 further comprising the steps of:
providing a baffle system; and affecting the flow of the at least
one fluid within the vessel using the baffle system.
48. The method of claim 36 further comprising the steps of:
providing a holding apparatus; and disposing the holding apparatus
in the vessel; and wherein the holding apparatus secures the
substrate within the vessel.
49. The method of claim 48 wherein the holding system comprises a
vacuum chuck comprising at least one vacuum cavity.
50. The method of claim 49 further comprising the steps of:
disposing a deformable membrane on the at least one cavity; and
disposing the substrate on the membrane.
51. The method of claim 50 further comprising applying a vacuum to
secure the substrate to the vacuum chuck.
52. The method of claim 49 further comprising the steps of:
providing a boot comprising an edge skirt; and disposing the boot
on the vacuum chuck.
53. The method of claim 52 further comprising the steps of:
disposing an electrical bridge contact in the boot; and sending an
electrical current through the bridge contact.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the filing of U.S.
Provisional Patent Application Ser. No. 60/541,687, entitled
"Pressurized Autocatalytic Vessel and Vacuum Chuck", filed Feb. 4,
2004. This application is also related to U.S. patent application
Ser. No. 10/778,647, entitled "Apparatus and Method for Highly
Controlled Electrodeposition", filed Feb. 12, 2004, which claims
priority of U.S. Provisional Patent Application Ser. No.
60/447,175, entitled "Electrochemical Devices and Processes", filed
Feb.12, 2003, and which is a continuation-in-part application of
U.S. patent application Ser. No. 10/728,636, entitled "Coated and
Magnetic Particles and Applications Thereof", filed Dec.5, 2003,
which claims priority of U.S. Provisional Patent Application Ser.
No. 60/431,315, entitled "Solid Core Solder Particles for Printable
Solder Paste", filed on Dec. 5, 2002, and the specifications and
claims thereof are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention (Technical Field)
[0003] The present invention relates to the plating of substrates
via metal deposition. Such plating involves either electrolytic
plating or electroless plating, otherwise commonly referred to as
autocatalytic plating.
[0004] 2. Background Art
[0005] During a typical autocatalytic plating process,
catalytically induced chemical reactions cause the continuous
deposition of a metal onto a solid surface. Autocatalytic plating
reactions are driven primarily by the temperature of the reaction,
and secondarily by the solution pH and the relative concentrations
of the metal complexes and their corresponding reducing agents.
Typically, the substrate surface is prepared for electroless
deposition by making it cathodic relative to the metal species to
be deposited to create a continuous surface layer of initiation
sites for the redox reactions.
[0006] Note that the following discussion refers to a number of
publications and references. Discussion of such publications herein
is given for more complete background of the scientific principles
and is not to be construed as an admission that such publications
are prior art for patentability determination purposes.
[0007] Electroless plating has been used for electronic assembly
components. There is now a significant interest in using it for
plating silicon wafers and other wafer scale and semi-conductor
devices. However, it is difficult to control spurious and
extraneous metal deposition onto surface areas where the metal is
not desired. Because autocatalytic plating is governed by the
chemical activity of the surface exposed to the plating solution as
well as by the chemical activity of the plating solution, metal
often deposits wherever and whenever a suitably activated surface
and a plating solution of sufficient chemical activity come in
contact.
[0008] Deposit edge resolution is not a primary concern with regard
to large coverage areas, but it is of greater concern with regard
to the plating of semiconductor wafers and substrates at micron
feature line widths. At micron and submicron feature sizes, the
magnitude of plating resolution and definition errors can approach,
and even exceed, the feature separation distance. This can cause
conductor bridging and electrical shorting of the wafer or
substrate.
[0009] In conventional practice, the propensity for electroless
plating chemical solutions to deposit metal indiscriminately is
controlled by incorporating any number of chemical rate inhibitors.
The inhibitors raise the chemical activation threshold for the
reduction of the metal ions out of solution thereby limiting their
deposition to only well activated surfaces. However, the addition
of inhibitors can negatively impact the utility of plating for
subsequent joining/connecting procedures. For example, a residue of
incorporated organics on, or within, the plating deposit can
preclude solder wetting or wire bonding to that metal surface. This
effect has discouraged the wide use of conventional electroless
plating technology for wafer scale electronic joining
applications.
[0010] Electroless plating is conventionally done in an open vessel
or tank. The vessel is typically made of either plastic or of
plastic lined metal to prevent the electroless chemicals from
spontaneously depositing out of solution when the plating solution
comes in contact with a metal surface.
[0011] A plastic, glass or polytetrafluoroethylene ("PTFE") coated
immersion heater is typically used to maintain the bath at the
optimal process temperature, which may range from 35 to 85 degrees
Celsius. The bath is typically mixed by stirring or by pumping the
solution in the tank.
[0012] The substrate is typically prepared by first immersing it in
a chemical cleaning solution followed by a rinse and an immersion
in a catalytic activator solution. The activated substrate is then
immersed in the hot plating bath until the desired thickness of the
plating layer is built up. The item is then removed, rinsed again,
and dried.
[0013] The following example outlines a typical process flow for
conventional electroless plating as it is conventionally practiced
in multiple tanks for an Electroless Nickel Immersion Gold ("ENIG")
process:
[0014] 1. immersion in an aluminum cleaner;
[0015] 2. immersion in a zincate activation solution;
[0016] 3. immersion in a desmut or strip solution;
[0017] 4. immersion in a second zincate solution;
[0018] 5. rinse in deionized water;
[0019] 6. immersion in a heated nickel electroless plating bath
solution;
[0020] 7. multiple rinses (1-3 times) in deionized water;
[0021] 8. immersion in an immersion gold bath solution; and
[0022] 9. rinse in deionized water.
[0023] This process is conventionally practiced in a serial
arrangement of open tanks, with the wafers or substrates fixed in a
plastic or plastic coated rack or wafer carrier. The wafers or
substrates are manually moved in their carrier from tank to tank or
are conveyed by a mechanical transporter. The requirement to
physically move the wafer or substrate from tank to tank creates a
significant risk of damage to the wafer. The risk of damage is
increased by the ongoing trend in the semiconductor processing
industry to "thin" wafers by chemical or mechanical means, making
an already delicate structure even more fragile.
[0024] To function well, conventional electroless plating
deposition processes require an optimum bath volume to plated work
surface area loading ratio. Therefore, a serial bath, open tank
electroless plating line, once constructed, will function well only
within a fairly narrow range of work volumes and area ratios.
[0025] Therefore, there is a need to better adapt autocatalytic
plating techniques and processes for optimal application in the
semiconductor industry.
[0026] With respect to the electrolytic plating of thin wafers such
as those found in the semiconductor industry, the existing
electrolytic plating methodology suffers from certain limitations.
To plate a wafer, the wafer is typically fixed onto a rigid
substrate to allow for plating, and an array of metallic contacts
are electrically connected via a wire to a direct current power
supply and to a counter-electrode (i.e. the anode). The metallic
surfaces of contacts must be completely isolated so that deposits
are not allowed to build up around the contact. Such build-up
detrimentally fuses the contact point to the surface of the wafer
and at the completion of the process can result in a tearing or
removal of the deposited film at the contact point.
[0027] Another limitation of electrolytic plating is that the
resulting surface area of the exposed contact can greatly affect
the amperage density applied and the cathode efficiency of the
wafer, which must be strictly controlled. This causes inaccurate or
inconsistent results in the mean target thickness of the deposited
film. Also, the contacts are a source of impurities that can be
introduced onto the wafer.
[0028] Electrolytic plating requires that a radial array of
contacts be disposed around the periphery of the wafer to be
plated. A current is bussed in through the wafer's edge where the
array is disposed. The higher the number of contact points around
the periphery of the wafer, the better the distribution of current.
The existing designs for electrolytic plating require a chemical
contact point and therefore create limitations in the number of
contact points that can be supplied around the periphery and
effectively sealed to prevent a detrimental influence on the
surface area of the plated wafer.
[0029] A limitation of copper electro-deposition on silicone wafers
is that the copper electrolyte and the resulting copper deposit can
contaminate the silicon. This converts the semiconductor material
into a conductive material, thereby ruining the entire wafer by
converting the surface from insulator to conductor.
[0030] Currently, the semiconductor industry favors the "damascene"
process for depositing copper, and techniques for depositing the
copper patterns have progressively favored the electrolytic
deposition of the metal. A number of clamping or sealing mechanisms
have been devised to seal off the edges and back side of the wafer
thereby exposing, through a circular or other patterned window, the
surface to be plated. Such devices are fairly complicated in that
typically a sandwich comprising a back plate, an O-ring seal, and a
top frame must be clamped, bolted, or fixed to the wafer. This
limits the effectiveness of automating the wafer handling process
in a production environment.
[0031] Consequently, the complicated nature of such devices limits
the cross-sectional area of the bussing elements which connect to
the contact points. The resulting buss cross-section is reduced to
favor the mechanical design, which detrimentally affects impacity
or current carrying capacity. This causes the requirement for a
higher voltage to complete the current flow through the
fixture.
[0032] A better, more effective method or apparatus for holding a
substrate during plating and for sealing portions of the substrate
and electrical contacts is required.
BRIEF SUMMARY OF THE INVENTION
[0033] The present invention comprises a plating apparatus
comprising a pressurized, sealable vessel within which to dispose a
substrate during plating of the substrate, a controllable source of
a plating fluid linked to the vessel, a holding apparatus to secure
the substrate within the vessel until the plating of the substrate
is complete, and at least one opening through which plating fluids
pass in and out of the vessel. In the preferred embodiment, the
apparatus is particularly applicable to autocatalytic plating.
[0034] The invention is particularly suitable to plating
semiconductor wafers.
[0035] The apparatus preferably comprises a closed loop system
between the controllable source of plating fluid and the vessel.
The invention preferably comprises a pressure control system to
control isostatic pressure within the vessel. The controllable
source of plating fluids preferably comprises a system for the
discreet, sequential introduction and removal of fluids into and
from the vessel and preferably comprises a plurality of nozzles and
conduits. The at least one opening in the vessel preferably
comprises a port.
[0036] The apparatus preferably comprises a temperature control
system, the system preferably controlling a temperature to within
approximately .+-.1.degree. C. The temperature control system
preferably heats and cools the plating fluid at a rate faster than
approximately 0.5.degree. C. per second, more preferably at a rate
faster than approximately 1.0.degree. C. per second, and most
preferably at a rate faster than approximately 2.5.degree. C. per
second. The temperature control system may be disposed outside of
the vessel to affect a temperature of a fluid prior to it entering
the vessel and/or disposed over the vessel and/or disposed in the
vessel. The temperature control system may also be disposed in at
least one wall of the vessel.
[0037] The vessel preferably comprises a volume of less than less
than approximately 5 liters, more preferably less than
approximately 3 liters, still more preferably less than
approximately 2 liters, still more preferably less than less than
approximately 1 liter, and most preferably less than approximately
0.5 liter.
[0038] The apparatus preferably comprises a baffle system disposed
within the vessel. The apparatus preferably comprises a cathode
disposed in the vessel to receive an electric current into the
vessel.
[0039] The vessel preferably comprises a base plate and a cover to
dispose on the base plate. The holding apparatus preferably
comprises a vacuum chuck which preferably a base and at least one
vacuum cavity in the base. The apparatus preferably comprises at
least one membrane disposed over the cavity(ies). The membrane
preferably comprises a membrane that is deformable in response to a
vacuum, and preferably comprises an elastomeric membrane.
[0040] The vacuum chuck preferably comprises a center shuttle
disposed in the base. The vacuum chuck also preferably comprises an
edge seal boot disposed on the base, and the edge seal boot
preferably comprises an edge skirt to contact the substrate and
seal a portion of the substrate. The apparatus may comprise an
electric bridge contact disposed in the edge skirt, and the contact
preferably comprises an array of contacts.
[0041] The present invention also comprises a method for depositing
metal on a substrate comprising providing a pressurized, sealable
vessel, securing the substrate within the sealable vessel,
introducing at least one plating fluid into the vessel, removing
the plating fluid(s) from the vessel, and removing the substrate
from the vessel after the metal has been deposited on the
substrate.
[0042] The method also preferably comprises introducing the fluids
discreetly and sequentially, and removing the fluids discreetly and
sequentially.
[0043] The method preferably comprises controlling an isostatic
pressure within the vessel. The method may also comprise disposing
a cathode in the vessel and sending an electrical current to the
cathode.
[0044] The method preferably comprises controlling a temperature of
fluid(s), preferably to within approximately .+-.1.degree. C. The
method also preferably comprises heating and cooling the plating
fluid preferably at a rate faster than approximately 0.5.degree. C.
per second, more preferably at a rate faster than approximately
1.0.degree. C. per second, and most preferably at a rate faster
than approximately 2.5.degree. C. per second. The temperature of
the fluid(s) is affected before introducing it into the vessel or
while inside the vessel.
[0045] The method also preferably comprises providing a baffle
system and affecting the flow of the fluid(s) within the vessel
using the baffle system.
[0046] The method preferably comprises providing a holding
apparatus and disposing the holding apparatus in the vessel,
wherein the holding apparatus secures the substrate within the
vessel. The holding apparatus preferably comprises a vacuum chuck
comprising at least one vacuum cavity. The method preferably
comprises disposing a deformable membrane on the cavity(ies) and
disposing the substrate on the membrane. Vacuum is preferably
applied to secure the substrate to the vacuum chuck.
[0047] Preferably, a boot comprising an edge skirt is provided and
the boot is disposed on the vacuum chuck. An electrical bridge
contact may be disposed in the boot and an electrical current is
sent through the bridge contact.
[0048] A primary object of the present invention is to provide for
the plating of a substrate while keeping the substrate in position
throughout the entire plating process.
[0049] Another object of the invention is to provide for better
control of autocatalytic plating processes, particularly with
respect to small substrates.
[0050] A primary advantage of the present invention is the ability
to finely control the plating processes with regard to, but not
limited to, initiation rates, deposition rates, temperature
control, and pressure control.
[0051] Another advantage of the present invention is the ability to
reduce the volumes required for plating.
[0052] Another advantage of the present invention is the ability to
minimize the risks of damage in plating small, expensive substrates
and thus reduce the costs inherent in such damage.
[0053] Other objects, advantages and novel features, and further
scope of applicability of the present invention are set forth in
part in the detailed description to follow, taken in conjunction
with the accompanying drawings, and in part will become apparent to
those skilled in the art upon examination of the following, or may
be learned by practice of the invention. The objects and advantages
of the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0054] The accompanying drawings, which are incorporated into, and
form a part of, the specification, illustrate one or more
embodiments of the present invention and, together with the
description, serve to explain the principles of the invention. The
drawings are only for the purpose of illustrating one or more
preferred embodiments of the invention and are not to be construed
as limiting the invention. In the drawings:
[0055] FIG. 1 is a perspective view of the preferred embodiment of
the vessel of the present invention;
[0056] FIG. 2 is a cross-sectional view of the embodiment of FIG.
1.
[0057] FIG. 3 is a cross-sectional view of the preferred embodiment
showing the application of vacuum into the vessel;
[0058] FIG. 4 is a cross-sectional view of the preferred embodiment
showing the introduction of a plating solution;
[0059] FIG. 5 is a cross-sectional view of the preferred embodiment
showing the circulation of a plating solution;
[0060] FIG. 6 is a cross-sectional view of the preferred embodiment
showing the purging of a plating solution;
[0061] FIG. 7 is a cross-sectional view of the preferred embodiment
showing a rinsing process;
[0062] FIG. 8 is a perspective view of the preferred embodiment
showing multiple solution nozzles;
[0063] FIG. 9 is a cross-sectional view of the preferred embodiment
of the vacuum chuck;
[0064] FIG. 10 is a perspective view of the preferred embodiment of
the vacuum chuck;
[0065] FIG. 11 is a cross-sectional view of the preferred
embodiment of the vacuum chuck showing the initial application of
vacuum;
[0066] FIG. 12 is a cross-sectional view of the preferred
embodiment of the vacuum chuck showing the subsequent application
of vacuum;
[0067] FIG. 13 is a cross-sectional view of the preferred
embodiment of the vacuum chuck showing the release of vacuum
through the center shuttle;
[0068] FIG. 14 is a cross-sectional view of the preferred
embodiment of the vacuum chuck showing the release of vacuum
through the center shuttle;
[0069] FIG. 15 is cross-sectional view of the edge skirt of the
preferred embodiment;
[0070] FIG. 16 is a cross-sectional view of the seal created by the
edge skirt of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0071] The preferred embodiment of the present invention comprises
a metal plating (i.e., metal deposition) apparatus and method. The
apparatus comprises a vessel or other enclosure to contain a
substrate to be plated while the substrate is subjected to one or
more plating processes and/or materials and fluids. Such processes
include the electrolytic and electroless (i.e., autocatalytic)
deposition of metal(s). As used herein, "substrate" is defined as
any object comprising a surface onto which metal deposition is to
occur, including, but not limited to, a semiconductor wafer. The
present invention provides for the plating of a substrate in a
single vessel without the need to transfer the substrate to other
vessels for exposure to other plating fluids or process steps. As
used herein, a "plating fluid" is any fluid to which a substrate is
exposed during a plating process including, but not limited to,
chemical solutions, rinsing solutions, and metal solutions. In the
preferred embodiment, the apparatus also comprises a controllable
source of a plating fluid. Such a controllable source preferably
comprises any source and delivery system known in the art
including, but not limited to, containers such as tanks or other
vessels linked to conduits for the transfer of fluids wherein the
delivery may be controlled by any number of systems such as, for
example, temperature control systems, pressure control systems,
pumps, valves, etc., or manual control.
[0072] In the preferred embodiment, the apparatus further comprises
a chuck, preferably a vacuum chuck, to hold the substrate in a
desired position during the process(es). In the preferred
embodiment, the apparatus and method are particularly suited for
use in the semiconductor industry, but may be utilized wherever the
indiscriminate deposition of metal onto surface areas must be
avoided and/or where a greater level of control over the deposition
of the metal is desired such as for the autocatalytic deposition of
ceramic substrates or other types of electronic substrates.
Although the apparatus and method of the present invention may be
utilized for both electrolytic and autocatalytic plating, the
remainder of this description focuses on autocatalytic plating.
[0073] As depicted in FIG. 1, the preferred embodiment of the
present invention comprises sealed plating vessel 20 within which
an item/substrate to be plated, such as substrate 100 (depicted in
the figures as a wafer), remains during the entire plating process.
Vessel 20 is preferably hydrostatically sealable. The plating
fluids to which substrate 100 is exposed are preferably introduced
discreetly (i.e., so that the unwanted contamination of one fluid
with another does not occur) into the cell, thereby allowing for
the sequential introduction of fluids at the appropriate process
step. The present invention, therefore, preferably provides for a
closed loop system between the source of the plating fluids and the
vessel 20.
[0074] Although the plating of one substrate 100 is described
herein and is representative of the preferred embodiment, other
embodiments of vessel 20 permit the plating of a plurality of
substrates, preferably fixed in a tight arrangement to increase the
total throughput.
[0075] Vessel 20 preferably comprises a cover such as dome 22 which
is preferably disposed over a bottom portion such as base plate 24.
Any shape or configuration for vessel 20 may be utilized in
accordance with the present invention, although a domed structure
with a circular base is preferred. Laminar flow formation is
preferably promoted by utilizing a non-rectangular shape of cell 30
adjacent to solution inlet 26. Base plate 24 is preferably machined
and preferably comprises stainless steel, plastic, or other rigid
material. Dome 22 preferably comprises supply port 26, which in the
preferred embodiment is preferably annular, for the introduction of
fluids into vessel 20. Dome 22 also preferably comprises return
port 28 for the return flow of fluids out of vessel 20. Although a
dome, base plate, and ports are described herein, any structure or
means known in the art to provide for a sealable vessel and to
provide access therein for the introduction and expelling of fluids
may be utilized.
[0076] In the preferred embodiment, heating and cooling controls
described below are provided. Such control of temperature is more
effective if the mass of vessel 20 is reduced. Therefore, in the
preferred embodiment, certain dimensions including, but not limited
to, wall thickness are minimized in manners well-known in the art
to provide for greater temperature control.
[0077] FIG. 2 shows a cross-section of the preferred embodiment of
vessel 20. As dome 22 is fitted over base plate 24, enclosed cell
30 is formed within vessel 20. Coupling nozzle 36 is preferably
disposed on supply port 26 and return port 28 to connect fluid
supply conduit 50 to supply port 26 and to connect fluid return
conduit 52 to port 28. Fluid supply conduit 50 transfers solution
200 (which may comprise any fluid to be introduced into vessel 20,
such as, but not limited to, chemical plating solutions) from
solution tank 54 and into cell 30, preferably through the use of
pump 56. Fluid return conduit 52 returns solution 200 to tank 54.
Preferably, a flow and pressure control system, preferably
comprising valve 60, pressure regulator 62, and filter 64, is
disposed along fluid return conduit 52.
[0078] Baffle system 88, as shown in FIG. 2a, is preferably
disposed within cell 30 (securing means not shown) to improve the
flow quality of fluids within cell 30. As plating fluid 200 passes
about and/or through baffle system 88, a pressure of the fluid,
within cell 30, as described below, is distributed and improves
laminar flow. Any design for baffle system 88 known in the art to
control the flow of fluids may be utilized.
[0079] Seal 34 is preferably provided, although any means known in
the art for ensuring the containment of fluids and gases within
cell 30 may be utilized. Drain basin 38 is preferably disposed
under base plate 24 to collect fluids when dome 22 is separated
from base plate 24. Released fluids are preferably collected
through drain return cup 68 and sent via drain conduit 70 to
storage (not shown) or to tank 72. Filter 74 may be disposed on
drain conduit 70.
[0080] Vessel 20 preferably comprises an apparatus for holding the
object to be plated (e.g., substrate 100) in a fixed or other
desired position during the plating process. The apparatus
preferably comprises chuck 40, and in the preferred embodiment,
comprises a vacuum chuck. The overall design of chuck 40 is
preferably circular, but any geometric shape may be utilized. In
the preferred embodiment, chuck 40 comprises a base that in the
preferred embodiment comprises base plate 24 (although chuck 40 can
comprise a separate, dedicated base) which in turn preferably
comprises vacuum chamber 44 and vacuum cavities 46, 46'. Vacuum
cavities 46, 46' may number one or more, although two are depicted
in the figures.
[0081] Chuck 40 also preferably comprises diaphragm 42 which is
disposed over, and completely seals, vacuum cavities 46, 46'.
Notwithstanding the number of vacuum cavities depicted throughout
the figures, one or more such cavities may be utilized. Membrane 42
preferably comprises a deformable sealing material, such as a
flexible or elastomeric membrane that can deform in response to
vacuum and that preferably comprises a material that is chemically
non-reactive and temperature resistant, such as, but not limited
to, thin rubber silicone. In a method of the present invention,
substrate 100 is disposed on diaphragm 42.
[0082] Vacuum port 48 is connected to a vacuum source system (not
shown). FIG. 3 shows how in the preferred embodiment, as vacuum is
applied into vacuum chamber 44 through vacuum port 48, vacuum
chamber 44, and vacuum cavities 46, 46', diaphragm 42 is distorted
so that vacuum void 47 forms between diaphragm 42 and substrate
100. The vacuum within vacuum void 47 holds substrate 100 against
base plate 24 and seals the contact surfaces between substrate 100
and diaphragm 42. Vacuum cavities 46, 46' preferably comprise a
series of concentric rings or grooves that are sized to create a
footprint pattern smaller than the main diameter of substrate 100.
Thus, the back side of substrate 100 is protected from exposure to
catalysts or other chemicals.
[0083] FIG. 4 shows the introduction of electroless chemical
solution 200 which preferably flows through port 26 into cell 30
preferably until cell 30 is filled to the desired level. Return
port 28 is preferably provided to permit the return or cycling of
solution 200 back to its source, such as tank 54. FIG. 5
schematically shows an embodiment of the present invention which
provides for a continuous circulation of solution 200 through cell
30. The duration of the flow of solution 200 through cell 30 and
the residence time for a given portion of solution 200 within cell
30 is determined by the process flow and the desired amount of
exposure to each solution.
[0084] In the preferred embodiment of the present invention, return
conduit 52, through which solution 200 is returned to its source,
is linked to a pressure system preferably comprising elements such
as valve 60 and pressure regulator 62. By regulating the back
pressure with valve 60, isostatic pressure may be introduced and/or
maintained within cell 30 and can act upon the surface of substrate
100 at the reaction interface. During plating, the pressure within
cell 30 is preferably maintained above atmospheric pressure.
[0085] As noted, typical electroless plating processes suffer from
the spurious deposition of metal in areas where deposition is not
desired and must be inhibited to maintain an acceptable level of
process control. Modulating the hydrostatic pressure of the plating
solution surrounding the substrate being plated can control the
electroless plating deposition rate. Specifically, increasing the
hydrostatic pressure in a closed space that holds both the plating
fluids and the substrate to be plated will reduce the plating rate
and increase the threshold for plating initiation in direct
proportion to the overpressure. This approach, in part, involves
the suppression of hydrogen gas generation at the boundary layer
between the metal surface and the plating fluid. The plating rate
can be retarded by increasing the direct application of hydrostatic
pressure to the system at up to several bars of overpressure. At
pressures greater than one atmosphere, the plating reaction can be
suspended so that there is no net metal deposition onto the
substrate.
[0086] Therefore, this preferred application of isostatic back
pressure in the present invention provides an additional kinetic
property or additional kinetic control that provides for better
process control without the need to add organic inhibiters. The
kinetic control provided by the present invention permits the use
of autocatalytic gold and other autocatalytic pressure chemical
formulations which have previously proven too reactive and too
difficult to control, as they require a high level of organic
inhibiters that typically result in an undesirable metallurgical
structure/material.
[0087] Through the application of hydrostatic pressure, the present
invention comprises the precise control of both the initiation and
rate of plating by directly controlling the physical environment of
the item to be plated. Other examples of the better control offered
by the present invention, discussed more fully below, are the
control over temperature and the electrical activation of various
surfaces to provide a more refined control over the deposition
process. Such control is particularly valuable within the
semiconductor industry because the line feature associated with
semiconductor patterns is too small to permit a high incidence of
organic material co-deposits. Such co-deposits reduce the
metallurgical density of the resulting metal pattern. By
controlling the environment as with the present invention, the
requirement to incorporate complexing agents, stabilizers,
inhibitors, etc. is largely, if not completely, obviated. The
present invention, therefore, provides for a metal deposit that is
free of the co-deposited and incorporated organic species commonly
found in the metal deposits resulting from conventional electroless
plating.
[0088] The pressure of the solution in cell 30 is regulated by
pressure valve 38 or other type of pressure regulator, which
preferably pressurizes the cell to one or two atmospheres above
open cell, or ambient, pressure. However, any pressure may be
utilized. For example, valve 38 introduces back pressure into cell
30, which optionally is monitored and controlled by pressure gauge
62 or other controller. The ability to pressurize cell 30 provides
control over pressure dependent characteristics of the plating
process, for example deposit kinetics, which results in improved
performance and an improved deposit.
[0089] Controlling the pressure in cell 30 also improves solution
exchange and ion supply on all surfaces of substrate 100, including
deep filled vias and planer surface areas. Thus, submicron
structures can be successfully plated and nanoscale vias can be
filled uniformly.
[0090] With regard to electrolytic plating, pressurizing cell 30
also suppresses the formation of gases such as hydrogen at the
deposition interface, (i.e. the cathode, or substrate, surface).
These gases cause undesirable porosity or voids resulting in
micropittings that typically occur in a deposit on the surface of
the cathode. Gases such as hydrogen also may reduce the mechanical
strength of the deposit; if hydrogen is left in the boundary area,
brittle deposits or highly stressed deposits may be formed,
resulting in tensile failure and possibly resulting in the deposit
peeling back from substrate 100. The integrity of the bond of the
deposit, such as a metallic interconnect, to substrate 100 is
critical to assure the high reliability necessary for electronic
components.
[0091] For applications in the submicron range, particulates,
pores, and micropittings that would normally be acceptable in
traditional plating applications are not tolerable because of the
small size of the features to be plated as well as the required
thinness of the deposit. Thus, the overall control of micropittings
is of paramount importance if semiconductor wafers are to be
electroplated. By using pressurization to minimize gas formation,
the integrity of the initial deposit on the surface of substrate
100 (when the voltage or the potential is at its highest), which
creates the first boundary layer between substrate 100 and the
metal being deposited, will be greatly improved. This results in a
surface morphology of sufficient quality to successfully plate
submicron structures.
[0092] Also, the ability to raise the pressure in cell 30 allows
for the use of temperatures higher than used conventionally such
as, for example, temperatures higher than the typical 85.degree.
C.
[0093] As shown in FIG. 6, after the desired processing is
complete, dome 22 can be lifted to create evacuation port 80.
Evacuation port 80 preferably comprises the open area encircling
base plate 24 and dome 22 as they are separated, thereby providing
for the a complete purging of solution 200. All purged fluids,
including solution 200, are preferably collected in basin 38. FIG.
6 shows catch basin 38 which is disposed over one or more of return
cup 68 (such as return cups 68, 68', 68", 68'", 68"", 68'"" as
shown in FIG. 8).
[0094] As shown in FIG. 7, after the purging of solution 200,
another coupling nozzle 36', which is connected via conduit 156 to
rinsing source 154 (containing rinsing fluid 158 such as, but not
limited to, deionized water), and is preferably connected to port
26 and/or port 28 to inject rinsing fluid 158 into cell 30 to
completely rinse out solution 200 and to purge rinse water 158.
Vessel 20 can be in an open or a closed position during this
step.
[0095] The injection and purging of water can be repeated a number
of times as described. Subsequent solutions are preferably applied
sequentially by attaching several coupling nozzles such as coupling
nozzles 36, 36', 36", 36'" shown in FIG. 8. All of the steps can be
repeated for any of each subsequent exposure to a solution. Thus,
solutions may be applied without contaminating one with another,
and they may be applied in a controlled time fashion to provide for
accuracy in the process and to build the desired metal deposit film
onto substrates.
[0096] To apply fluids sequentially, nozzle turret system 136 or
other similar (to accomplish the same task)is preferably utilized
in one embodiment, as shown in FIG. 8, which can, for example,
rotate to sequentially dispose distinct nozzles on vessel 20. By
multiplying the number of tanks, the number of nozzles and the
number of return cups, an unlimited number of process steps can be
applied to the vessel to provide a sophisticated process control
capability without transferring substrate 100 or other substrates
from vessel to vessel. The present invention also allows for the
pressurization of the work zone with an inert gas, such as
nitrogen, to control or eliminate oxidation on the metals between
process steps (i.e., elimination of exposure to oxygen).
[0097] An example of the method of the present invention applied to
an ENIG plating deposition comparable to the conventional
electroless plating process sequence described in the background
section above is as follows:
[0098] 1. filling the cell with an aluminum cleaner;
[0099] 2. rinsing the cell with deionized water;
[0100] 3. filling the cell with a zincate solution;
[0101] 4. rinsing the cell with deionized water;
[0102] 5. introducing a nickel electroless plating bath solution to
the cell and heating the cell to operating temperature;
[0103] 6. rinsing the cell with deionized water;
[0104] 7. introducing an immersion gold bath solution to the cell
and heating the cell to operating temperature; and
[0105] 8. rinsing the cell with deionized water.
[0106] In the present invention, plating solution 200 can be held
outside vessel 20 at a temperature just below the minimum plating
temperature and quickly raised to the optimum operating temperature
just as plating solution 200 is introduced into cell 30. Plating
solution 200 can be heated either by heating tank 54, by passing it
through thermostatically controlled heating coil 58 (shown in FIG.
2) or by embedding a heating system directly within the walls of
vessel 20, such as, for example, incorporating a heating/cooling
jacket 59 adjacent walls 32 of dome 22 as shown in FIG. 2a. The
heating system can comprise a heating/cooling jacket through which
a thermal control fluid such as, but not limited to, water and/or
glycol can be circulated. Other thermally conductive materials that
may be utilized in such a heating system include gases. Also, a
combination of electrically resistive heating and gaseous cooling,
thermoelectric heating and cooling, and combinations thereof may be
utilized. In effect, any heating/cooling system known in the art
may be used to regulate temperature. Also, a temperature control
system may be combined with such a heating system, thermocouples or
other systems may be included to provide feedback to the
temperature control system to keep plating solution 200 within a
desired temperature within approximately .+-.1.degree. C.
[0107] In addition to maintaining a constant temperature, the
present invention provides for the ability to quickly heat and/or
cool a plating fluid. Such cooling and heating rates are preferably
at rates of greater than approximately 2.degree. C. per second,
more preferably at rates of greater than approximately 1.degree. C.
per second, and most preferably at rates of greater than
approximately 0.5.degree. C. per second.
[0108] The temperature regulating feature of the present invention
is particularly helpful given that electroless plating processes
are highly dependent upon solution temperatures. Most autocatalytic
plating chemical solutions are designed to operate within a very
narrow range of temperature to achieve their catalytic effect and
can heat in situ.
[0109] The present invention provides for better and more efficient
process management in part because the volume of the cell can be
much smaller such as approximately 1-5 liters (but can be much
smaller such as 0.5 liters or smaller) in comparison to the tank
facilities utilized in conventional plating processes. The
relatively smaller volume of plating solution 200 in use at any one
time facilitates a higher degree of thermal management and plating
rate control than can be afforded by the open tank electroless
plating methodology. The smaller size is especially suited when
using a "static" plating embodiment described below wherein fluid
is not circulated within vessel 20 while deposition is taking
place.
[0110] Another benefit of the reduced volume is that, because the
amount of the organic chemicals in the solution is reduced, the
resulting metallurgical quality of the deposited film is higher.
For example, the use of autocatalytic gold allows thicker deposit
features that exceed 7 micrometers, thereby allowing an
electroless, post forming tool to form columns in precious metals
such as gold and platinum.
[0111] Although the figures and the preferred embodiment describe
herein describe an apparatus and method wherein plating fluids are
moved into, within, and out of vessel 20, another embodiment
provides that plating fluids may be introduced into vessel 20 and
held statically (i.e., not circulated within vessel 20). In this
"static fluid", non-flow embodiment, plating reactions occur
between the static chemical solutions and the surface of substrate
100. The initiation and rate of plating is controlled by
temperature control and/or hydrostatic overpressure control.
Operating the plating process in this static fluid mode provides
for rigorous control of the volume of plating fluid 200. In other
words, the amount of chemical used per substrate 100 can be titered
to the point of use, and it is not necessary to hold the entire the
source of plating solution 200 at operating temperatures. The
volume of plating fluid 200 can be heated at either the point of
use (i.e., within vessel 20) or immediately preceding the
introduction of plating fluid 200 in to vessel 20. Therefore, the
activity and performance of plating chemicals is preserved even as
the amount of chemicals expended per substrate during the plating
process is conserved. This embodiment is particularly suitable when
the dimensions of vessel 20 are greatly reduced in volume and/or in
terms of such dimensions as wall thickness, etc.
[0112] In the preferred embodiment, vessel 20 comprises electrode
76, which preferably comprises a ring-shaped cathode. Electrode 76
is disposed within vessel 20 (connection not shown) and can be
electrically biased to walls 32 or substrate 100. Electrode 76 can
be employed to electrically activate the substrate to be plated to
initiate the plating process. Electrode 76 can also be used to
prevent plating deposition from going out of solution and onto
vessel 20.
[0113] Electrode 76 is connected to direct current voltage power
supply 78. Base plate 24 and dome 22, which are preferably
manufactured of a metal that can be utilized as an electrode, such
as, but not limited to, stainless steel or titanium, comprise the
counter-electrode (i.e., anode). This provides a voltage potential
on the surface of base plate 24 and dome 22, protecting them from
metal deposition. The use of base plate 24 and dome 22 as an anode
can also provide a control scheme to accelerate the initiation of
the electroless process, which is typically controlled by bath
loading. The control scheme "fine tunes" the control over the
plating process. Initiation can be controlled by increasing or
decreasing the voltage into cell 30.
[0114] In accordance with the present invention, the polarity and
amplitude of bias voltage of ring electrodes can be varied to
facilitate anodic protection of the cell elements exposed to the
plating solution during the process (conventional electroless
plating processes can control plating initiation only by adjusting
levels of plating bath additives and bath temperature). The cell
design has a resident cathode electrode which can be used to
compensate dynamically for variations in the exposed wafer surface
area to be plated (conventional electroless plating processes have
a fundamental limitation as to the plating surface load which can
be plated at any given time which places limits on the flexibility
of the conventional electroless plating line hardware).
[0115] As detailed, the preferred embodiment of the vacuum chuck is
shown in FIGS. 9-16. Vacuum chuck 140 preferably comprises center
articulating shuttle 180 for interfacing substrate 100 with
automated end effectors (e.g., Y-shaped effector 220) and robotics
for wafer handling and wafer automation. Vacuum chuck 140 is
preferably rotatable, which provides advantages in uniformity of
deposit. Center articulating shuttle 180 is preferably disposed
within base plate 124. As shown in FIG. 11, when substrate 100 is
positioned on chuck 140, center articulating shuttle 180 holds
substrate 100 above base plate 124 to expose an outer perimeter of
the back side of substrate 100. Substrate 100 can then be carried
from the back side such as, for example, by effector 220 as shown
in FIG. 10. Fastener 118 holds diaphragm 142 to base plate 124 so
that only that portion of diaphragm 142 disposed on center
articulating shuttle 180 rises above base plate 124. Thus, handling
can be interfaced with conventional robotics.
[0116] FIG. 11 show substrate 100 held to center articulating
shuttle 180 as vacuum is applied through port 186 into vacuum
chamber 182 and vacuum cavities 184, 184' (any number of cavities
may be provided). The vacuum causes diaphragm 142 to deform,
thereby creating corresponding voids 188, 188'. FIG. 12 shows
center articulating shuttle 180 lowered into position so that
substrate 100 is set onto backing plate 124. FIG. 12 shows the
application of vacuum through port 148 into vacuum chamber 144 and
cavities 146, 146', 146" (any number of cavities may be provided).
This causes diaphragm 142 to deform and create corresponding voids
147, 147', 147" so that substrate 100 is held onto, and sealed
against, backing plate 124. FIG. 14 shows shuttle 180 retracted
further upon release of vacuum in chamber 182 so that it does not
interfere with the rotation, if such is desired, of substrate
100.
[0117] In the preferred embodiment, edge seal boot 190 is disposed
at the periphery of diaphragm 142. Edge seal boot 190 comprises any
flexible material that may provide a seal. Edge seal boot 190 may
be utilized in conjunction with any type vacuum chuck such as, but
not limited to, vacuum chuck 40 described in FIGS. 1-7, although it
is depicted herein in relation to chuck 140. As detailed in FIG.
15, edge seal boot 190 is constructed so that it provides for
vacuum chamber 144 to extend above and around the periphery of
substrate 100, preferably when center shuttle 180 is in a position
prior to bringing substrate 100 into full contact with base plate
124. Edge seal boot 190 preferably comprises edge skirt 192 which
collapses upon the application of vacuum within vacuum chamber 144.
As shown in FIG. 16, upon the application of vacuum through port
148, edge seal boot 190 preferably collapses. The design of the
wall thickness of edge bladder 190 is preferably in a staged
fashion so that a controlled collapse of edge seal boot 190 pulls
edge skirt 192 into contact with the surface of substrate 100,
creating an effective air and gas seal on the surface of substrate
100. Because a hydrostatic seal is created which protects the edges
and backside of substrate 100 from contact with plating chemicals,
there is no need for masking or coating the backside of the
wafer.
[0118] With respect to electrolytic plating, an electrolytic
contact with substrate 100 is not required but is preferably
incorporated by providing electrical bridge contact 196 and
electrical buss ring 194 as shown in FIG. 15. In practice,
substrate 100 is placed concentrically within electrical buss ring
194 which has a diameter greater than the main diameter of
substrate 100 so that substrate 100 can nest within electrical buss
ring 194. The surface of ring 194 is exposed to the top side and is
approximately flush with the surface of substrate 100.
[0119] Electrical bridge contact 196 is preferably embedded in edge
seal boot 190, and preferably comprises an evenly distributed array
of contacts, preferably so that electrical bridge contact 196 is
isolated when edge seal boot 190 is not under vacuum. When vacuum
is applied and edge skirt 192 is pulled into contact with substrate
100, electrical bridge contact 196 contacts ring 194 to cause an
electrical contact to the surface of substrate 100. This results in
a continuity from a, preferably direct current, power supply,
thereby bussing current in a 360 degree multi-point contact along
the periphery of substrate 100.
[0120] Edge skirt 192 also provides a seal to prevent contamination
of the back side and the periphery are of substrate 100 from the
copper electrolyte solution and also to isolate electrical contacts
196 from exposure to the electrolyte thereby preventing deposits
from forming on electrical bridge contact 196. This provides for an
easier and less damaging removal of substrate 100 upon completion
of electrolytic plating. This also reduces the maintenance required
for electrical bridge contact 196 which would typically suffer from
a build-up of deposits.
[0121] The bussing circuitry described above can be used in a notic
and ketotic fashion and with pulse and periodic reverse regimes.
Electrolytic plating processes benefit from the use of the
described array of electrical bridge contact 196. The result is a
lower resistance bussing of the current from buss ring 194 to the
surface of substrate 100 thereby requiring a lower voltage and
providing preferential conditions for the electro deposition
process.
[0122] Chuck 140 can be utilized in open and closed electroplating
cells, in a vertical or horizontal position, and can be affixed to
a bearing device (not shown) and rotationally actuated so that the
leading edge effects due to electrodeposition from a flowing
electrolyte are mitigated by rotating substrate 100 continuously
through the electrodeposition process to facilitate a homogeneous
deposit thickness on the wafer.
[0123] Because plating processes typically occur at the final stage
of wafer processing, a considerable investment in materials and
work has already been made to a wafer before plating, and any
damage to a wafer during plating results in a substantial loss of
the investment. The method of the present invention provides a more
reliable processing strategy with less risk than can be
accomplished with conventional plating. Also, because the present
invention allows for the plating of one wafer at a time, mistakes
are less costly (e.g., conventional electroless plating processes
operate on multiple wafers in parallel per plating tank step, so a
deviation or defect in the process parameters in any given
step/tank carries with it the attendant risk of damage to multiple
wafers). However, multiple substrates may be plated in parallel
according to the present invention. Thus, the present invention
results in improved film quality, improved feature size capability,
and a great reduction of risk to finished substrates.
[0124] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
[0125] Although the invention has been described in detail with
particular reference to the preferred embodiments in the
attachment, other embodiments can achieve the same results.
Variations and modifications of the present invention will be
obvious to those skilled in the art and it is intended to cover all
such modifications and equivalents. The entire disclosures of all
references, applications, patents, and publications cited above,
and of the corresponding application(s), are hereby incorporated by
reference.
* * * * *