U.S. patent application number 10/424479 was filed with the patent office on 2003-10-30 for method and associated apparatus for tilting a substrate upon entry for metal deposition.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Dordi, Yezdi N., Stevens, Joseph J., Sugarman, Michael N..
Application Number | 20030201184 10/424479 |
Document ID | / |
Family ID | 24724984 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030201184 |
Kind Code |
A1 |
Dordi, Yezdi N. ; et
al. |
October 30, 2003 |
Method and associated apparatus for tilting a substrate upon entry
for metal deposition
Abstract
An electro-chemical plating system is described. A method is
performed by the electro-chemical plating system in which a seed
layer formed on a substrate is immersed into an electrolyte
solution. In one aspect, a substrate is immersed in the
electrochemical plating system by tilting the substrate as it
enters the electrolyte solution to limit the trapping or formation
of air bubbles in the electrolyte solution between the substrate
and the substrate holder. In another aspect, an apparatus is
provided for electroplating that comprises a cell, a substrate
holder, and an actuator. The actuator can displace the substrate
holder assembly in the x and z directions and also tilt the
substrate. In another aspect, a method is provided of driving a
meniscus formed by electrolyte solution across a surface of a
substrate. The method comprises enhancing the interaction between
the electrolyte solution meniscus and the surface as the substrate
is immersed into the electrolyte solution.
Inventors: |
Dordi, Yezdi N.; (Palo Alto,
CA) ; Stevens, Joseph J.; (San Jose, CA) ;
Sugarman, Michael N.; (San Francisco, CA) |
Correspondence
Address: |
Patent Counsel
APPLIED MATERIALS, INC.
P.O. Box 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
24724984 |
Appl. No.: |
10/424479 |
Filed: |
April 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10424479 |
Apr 28, 2003 |
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09678947 |
Oct 3, 2000 |
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6582578 |
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09678947 |
Oct 3, 2000 |
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09289074 |
Apr 8, 1999 |
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6258220 |
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Current U.S.
Class: |
205/80 ; 205/96;
257/E21.175 |
Current CPC
Class: |
C25D 21/00 20130101;
C25D 7/123 20130101; H05K 3/241 20130101; H01L 21/2885 20130101;
C25D 21/04 20130101 |
Class at
Publication: |
205/80 ;
205/96 |
International
Class: |
C25D 005/00 |
Claims
What is claimed is:
1. A method for immersing a substrate into a plating solution,
comprising: positioning the substrate to a first angle relative to
horizontal; immersing the substrate into the plating solution while
substantially maintaining the substrate at the first angle; and
tilting the substrate to a second angle relative to horizontal.
2. The method of claim 1, wherein tilting the substrate to the
second angle comprises tilting the substrate to the second angle as
the substrate is being immersed into the plating solution.
3. The method of claim 1, wherein tilting the substrate to the
second angle comprises tilting the substrate to the second angle
after the substrate is immersed into the plating solution.
4. The method of claim 1, further comprising tilting the substrate
to a processing position.
5. The method of claim 4, wherein the processing position is
generally horizontal.
6. The method of claim 4, wherein the substrate is tilted to a
processing position after the substrate is tilted to the second
angle.
7. The method of claim 1, wherein tilting the substrate to the
second angle comprises moving the substrate in an x direction as
the substrate is being immersed into the plating solution.
8. The method of claim 1, wherein tilting the substrate to the
second angle comprises: tilting the substrate to the second angle
as the substrate is being immersed into the plating solution; and
moving the substrate in an x direction as the substrate is being
immersed into the plating solution.
9. The method of claim 1, further comprising spinning the substrate
as the substrate is being immersed into the plating solution.
10. The method of claim 1, wherein the first angle is greater than
the second angle.
11. The method of claim 1, wherein the rate at which the first
angle changes toward horizontal is greater than the rate at which
the second angle changes toward horizontal.
12. The method of claim 1, wherein the second angle is closer to
horizontal than the first angle.
13. The method of claim 1, wherein the first angle is greater than
about 0 degrees and less than about 90 degrees from horizontal.
14. The method of claim 1, wherein the first angle is greater than
about 0 degrees and less than about 45 degrees from horizontal.
15. The method of claim 1, wherein the first angle is greater than
about 45 degrees and less than about 90 degrees from
horizontal.
16. The method of claim 1, wherein the first angle is about 45
degrees from horizontal.
17. The method of claim 1, wherein tilting the substrate to the
second angle dislodges bubbles adhering to the substrate.
18. A method for immersing a substrate into a plating solution,
comprising: positioning the substrate to a first angle relative to
horizontal; immersing the substrate into the plating solution while
substantially maintaining the substrate at the first angle; tilting
the substrate to a second angle relative to horizontal as the
substrate is being immersed into the plating solution; and tilting
the substrate to a generally horizontal position for
processing.
19. The method of claim 18, further comprising spinning the
substrate as the substrate is being immersed into the plating
solution.
20. The method of claim 18, wherein tilting the substrate to the
second angle comprises moving the substrate in an x direction as
the substrate is being immersed into the plating solution.
21. A method for immersing a substrate into a plating solution,
comprising: positioning the substrate to a first angle relative to
horizontal; immersing the substrate into the plating solution while
substantially maintaining the substrate at the first angle; tilting
the substrate to a second angle relative to horizontal after the
substrate is immersed into the plating solution; and tilting the
substrate to a generally horizontal position for processing.
22. The method of claim 21, further comprising spinning the
substrate as the substrate is being immersed into the plating
solution.
23. The method of claim 21, wherein tilting the substrate to the
second angle comprises moving the substrate in an x direction.
Description
CROSS REFERENCE TO RELATED INVENTION
[0001] This is a continuation of prior filed U.S. patent
application Ser. No. 09/678,947, filed Oct. 3, 2000 and entitled
"METHOD AND ASSOCIATED APPARATUS, FOR TILTING A SUBSTRATE UPON
ENTRY FOR METAL DEPOSITION," which is a continuation-in-part of
prior filed U.S. patent application Ser. No. 09/289,074, filed Apr.
8, 1999, and entitled "ELECTRO-CHEMICAL DEPOSITION SYSTEM" and
claims priority to prior filed U.S. Provisional Patent Application,
Serial No. 60/216,896, filed on Jul. 7, 2000 and entitled "METHOD
AND APPARATUS FOR TILTING A SUBSTRATE UPON ENTRY", which are all
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to deposition of a
metal layer onto a substrate. More particularly, the present
invention relates to a substrate holder system for use in an
electrochemical plating (ECP) system to deposit a metal film on a
substrate.
[0004] 2. Description of the Related Art
[0005] Electroplating is used for the fabrication of lines on
circuit boards as well as to fill features, such as vias, trenches,
and electric contact elements, for example, in semiconductor
devices. A typical feature-fill process including electroplating
comprises depositing a barrier layer over the feature surfaces by a
process such as physical vapor deposition (PVD) or chemical vapor
deposition (CVD), then depositing a conductive metal seed layer
such as copper on the barrier layer by a process such as PVD or
CVD, and then electroplating a conductive metal film over the seed
layer to fill the feature and form a blanket layer on the field to
form the desired conductive structure. The deposited metal film is
then planarized by a process such as chemical mechanical polishing
(CMP) to define a conductive interconnect feature. An electric
contact ring is commonly positioned in contact with the seed layer
on the substrate during electroplating to supply electricity to the
seed layer.
[0006] A number of obstacles impair reliable electroplating onto
substrates having micron-sized, high aspect ratio features. One of
these obstacles relates to a substrates, held by a substrate holder
assembly, being immersed in a level attitude into electrolyte
solution. The substrate holder assembly typically includes an
electric contact ring, or a support ring, that extends around the
periphery of the substrate. The electric contact ring or a support
ring typically physically supports the substrate during
electroplating. Portions of the substrate holder assembly, such as
electric contact rings or support rings, together with the
substrate define a downwardly-facing concave surface. As the
substrate holder assembly is immersed with the substrate, the
concave surface defined by the substrate and substrate holder
assembly can trap air that form air pockets within the electrolyte
solution.
[0007] The air bubbles or the air bridges that are trapped in the
electrolyte solution by the concave surface defined by the
substrate holder assembly and substrate can contact the surface of
the substrate during plating. The electrolyte solution does not
physically contact those portions of the seed layer on the
substrate that the air bubbles or air bridges contact. Metal film,
therefore, cannot be deposited on those portions of the seed layer
that the air bubbles or air pockets cover. As such, the existence
of air bubbles or air bridges adjacent the seed layer during metal
film deposition can affect the uniformity of the depth of the
deposited metal film across the seed layer. Limiting the amount of
air bubbles or air bridges that contact the seed layer during
processing and providing a uniform electric current density across
the seed layer on the substrate during plating.
[0008] The existence of air bubbles within the features during
deposition of the metal film can also limit the filling of the
features on the substrate, and thereby lead to the creation of
voids, or spaces, within features formed within the deposited metal
film. The existence of voids in the features leads to unreliable,
unpredictable, and unuseable electronic devices in the electronic
circuit containing the feature.
[0009] Therefore, there remains a need for an electrochemical
plating (ECP) system that limits the formation of air bubbles
between the substrate and/or the substrate holder assembly during
the immersion of the substrate into electrolyte solution.
SUMMARY OF THE INVENTION
[0010] Embodiments of the present invention generally provide an
ECP system. More specifically, a method is performed by the
electrochemical plating system in which a seed layer formed on a
substrate is immersed into an electrolyte solution. In one aspect,
a substrate is immersed in the electrochemical plating system by
tilting the substrate as it enters the electrolyte solution to
limit the trapping or formation of air bubbles in the electrolyte
solution between the substrate and the substrate holder assembly.
In another aspect, an apparatus is provided for electroplating that
comprises a cell and a substrate holder system. The substrate
holder system can displace the substrate holder assembly in the x
and z directions and also tilt the substrate. In another aspect, a
method is provided of driving a meniscus formed by electrolyte
solution across a surface of a substrate. The method comprises
enhancing the interaction between the electrolyte solution meniscus
and the surface as the substrate is immersed into the electrolyte
solution.
[0011] In another embodiment, a method for immersing a substrate
into a plating solution is disclosed herein. The method includes
positioning the substrate to a first angle relative to horizontal,
immersing the substrate into the plating solution while
substantially maintaining the substrate at the first angle, and
tilting the substrate to a second angle relative to horizontal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features,
advantages and objects of the present invention are attained can be
understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to the
embodiments thereof which are illustrated in the appended
drawings.
[0013] FIG. 1 is a cross sectional view of a simplified typical
fountain plater;
[0014] FIG. 2 is a perspective view of one embodiment of an
electrochemical plating (ECP) system;
[0015] FIG. 3 is a top schematic view of the ECP system of FIG.
2;
[0016] FIG. 4 is a schematic perspective view of one embodiment of
spin-rinse-dry (SRD) module, incorporating rinsing and
dissolving-fluid inlets;
[0017] FIG. 5 is a side cross sectional view of the spin-rinse-dry
(SRD) module of FIG. 4 and shows a substrate in a processing
position;
[0018] FIG. 6 is a cross sectional view of an electroplating
process cell having a substrate holder system;
[0019] FIG. 7 is a partial cross sectional perspective view of an
embodiment of electric contact element;
[0020] FIG. 8 is a cross sectional perspective view of the electric
contact element showing an alternative embodiment of contact
pads;
[0021] FIG. 9 is a cross sectional perspective view of the electric
contact element showing an alternative embodiment of the contact
pads and an isolation gasket;
[0022] FIG. 10 is a cross sectional perspective view of the
electric contact element showing the isolation gasket;
[0023] FIG. 11 is a simplified schematic diagram of the electric
circuit representing the ECP system through each contact pin;
[0024] FIG. 12 is a cross sectional view of an embodiment of
substrate holder assembly;
[0025] FIG. 12A is an enlarged cross sectional view of the bladder
area of FIG. 12;
[0026] FIG. 13 is a partial cross sectional view of a substrate
holder plate;
[0027] FIG. 14 is a partial cross sectional view of a manifold;
[0028] FIG. 15 is a partial cross sectional view of a bladder;
[0029] FIG. 16 is a schematic diagram of one embodiment of
electrolyte solution system;
[0030] FIG. 17 is a cross sectional view of a rapid thermal anneal
(RTA) chamber;
[0031] FIG. 18 is a perspective view of an alternative embodiment
of an electric contact element;
[0032] FIG. 19 is a partial cross sectional view of an alternative
embodiment of a substrate holder assembly;
[0033] FIG. 20 is a cross sectional view of an embodiment of an
encapsulated anode;
[0034] FIG. 21 is a cross sectional view of another embodiment of
an encapsulated anode;
[0035] FIG. 22 is a cross sectional view of another embodiment of
an encapsulated anode;
[0036] FIG. 23 is a cross sectional view of yet another, embodiment
of an encapsulated anode;
[0037] FIG. 24 is a top schematic view of a mainframe transfer
robot having a flipper robot incorporated therein;
[0038] FIG. 25 is an alternative embodiment of the substrate holder
system having a rotatable head assembly;
[0039] FIGS. 26a and 26b are cross sectional views of embodiments
of a degasser module;
[0040] FIG. 27 is a cross sectional view of one embodiment of the
rotatable head assembly shown in FIG. 25;
[0041] FIG. 28, comprising FIGS. 28A to 28H, is a progression of
side views of the substrate holder system during immersion of a
seed layer on a substrate into the electrolyte solution contained
in the electrolyte cell;
[0042] FIG. 29 is one embodiment of a method performed by the
controller of FIG. 27 in performing the progression shown in FIG.
28;
[0043] FIG. 30 is a side view of a progression of substrates being
inserted into the electrolyte solution;
[0044] FIG. 31 is a side view of an immersed substrate having air
bubbles trapped between the substrate and the substrate holder
assembly;
[0045] FIG. 32 is a side view of an immersed substrate having an
air bridge forming between the substrate and the substrate holder
assembly;
[0046] FIG. 33 is a graph showing immersion of a substrate
indicating the rate of change of the angle of the substrate as the
ordinate versus time as the abscissa;.
[0047] FIG. 34 shows one embodiment of a substrate having a feature
being lowered into an electrolyte solution, in which a level of
electrolyte solution is below the level of a feature;
[0048] FIG. 35 shows the lowering of the substrate into the
electrolyte solution as shown in FIG. 34, in which the level of the
electrolyte solution is above to the level of the feature; and
[0049] FIG. 36 shows another embodiment of substrate holder
system.
[0050] The terms "below", "above", "bottom", "top", "up", "down",
"upper", and "lower" and other positional terms used herein are
shown with respect to the embodiments in the figures and may be
varied depending on the relative orientation of the processing
apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0051] This disclosure describes the structure and operation of an
electro-chemical plating (ECP) system. A substrate holder system of
the ECP system is also detailed. Operation of the substrate holder
system provides for tilting of the substrate upon immersion of the
substrate into the electrolyte solution.
[0052] 1. ECP System
[0053] FIG. 1 is a cross sectional view of one embodiment of
fountain plater 10 involved in electroplating. Generally, the
fountain plater 10 includes an electrolyte cell 12, an electric
contact ring 20, a controller 23, a substrate holder system 14, and
an anode 16. The electrolyte cell 12 has a top opening through
which the substrate holder system 14 can immerse the substrate
into, or remove the substrate from, the electrolyte solution
contained in the electrolyte cell. The anode 16 is immersed in
electrolyte solution contained in the electrolyte cell 12. A
plurality of grooves 24 is formed in the lower surface of the
substrate holder system 14. A vacuum pump 33 is coupled to the
substrate holder system 14 and communicates with the grooves 24 to
create a vacuum condition that is capable of securing the backside
of the substrate 22 to the substrate holder system 14 during
processing. The electric contact ring 20 comprises a plurality of
metallic or semi-metallic contact pins 26 distributed about the
peripheral portion of the substrate 22 to define a central
substrate plating surface. The tips of each one of the plurality of
contact pins 26 contact the seed layer on the substrate 22. A
controller 23 controls the electricity supplied to the pins 26 and
the anode 16 to providing an electric bias between the seed layer
on the substrate 22 and the anode. The substrate 22 is positioned
near the top of, and within, the cylindrical electrolyte cell 12
and electrolyte solution flow impinges perpendicularly on the
substrate plating surface during operation of the cell 10.
[0054] FIG. 2 is a perspective view of one embodiment of an ECP
system 200. FIG. 3 is a top plan view of the ECP system 200 of FIG.
2. Referring to both FIGS. 2 and 3 together, the ECP system 200
generally comprises a loading station 210, a rapid thermal anneal
(RTA) chamber 211, a spin-rinse-dry (SRD) station 212, a mainframe
214, and an electrolyte solution system 220. Preferably, the ECP
system 200 is enclosed in a clean environment using panels such as
PLEXIGLAS.RTM. (a registered trademark of the Rohm and Haas
Company, West Philadelphia, Pa.) panels. The mainframe 214
generally comprises a mainframe transfer station 216 and a
plurality of processing stations 218. Each processing station 218
includes one or more process cells 240. An electrolyte solution
system 220 is positioned adjacent the ECP system 200 and connected
to the process cells 240 individually to circulate electrolyte
solution used for the electroplating process. The ECP system 200
also includes a controller 222 that typically comprises a
programmable microprocessor.
[0055] The loading station 210 preferably includes one or more
substrate cassette receiving areas 224, one or more loading station
transfer robots 228 and at least one substrate orientor 230. The
number of substrate cassette receiving areas, loading station
transfer robots 228 and substrate orientors included in the loading
station 210 can be configured according to the desired throughput
of the system. As shown for one embodiment in FIGS. 2 and 3, the
loading station 210 includes two substrate cassette receiving areas
224, two loading station transfer robots 228 and one substrate
orientor 230. A substrate cassette 232 containing substrates 234 is
loaded onto the substrate cassette receiving area 224 to introduce
substrates 234 into the ECP system. The loading station transfer
robot 228 transfers substrates 234 between the substrate cassette
232 and the substrate orientor 230. The loading station transfer
robot 228 comprises a typical transfer robot commonly known in the
art. The substrate orientor 230 positions each substrate 234 in a
desired orientation to ensure that the substrate is properly
processed. The loading station transfer robot 228 also transfers
substrates 234 between the loading station 210 and the SRD station
212 and between the loading station 210 and the RTA chamber
211.
[0056] FIG. 4 is a schematic perspective view of one embodiment of
a spin-rinse-dry (SRD) module 236, incorporating rinsing and
dissolving fluid inlets. FIG. 5 is a side cross sectional view of
the SRD module of FIG. 4 and shows a substrate in a processing
position vertically disposed between fluid inlets. Preferably, the
SRD station 212 includes one or more SRD modules 236 and one or
more substrate pass-through cassettes 238. Preferably, the SRD
station 212 includes two SRD modules 236 corresponding to the
number of loading station transfer robots 228, and a substrate
pass-through cassette 238 is positioned above each SRD module 236.
The substrate pass-through cassette 238 facilitates substrate
transfer between the loading station 210 and the mainframe 214. The
substrate pass-through cassette 238 provides access to and from
both the loading station transfer robot 228 and a robot in the
mainframe transfer station 216.
[0057] Referring to FIGS. 4 and 5, the SRD module 236 comprises a
bottom 330a, a sidewall 330b, and an upper shield 330c. The bottom
330a, the sidewall 330b, and the upper shield 330c collectively
define a SRD module bowl 330d, where the shield attaches to the
sidewall and assists in retaining the fluids within the SRD module
236. Alternatively, a removable cover could also be used. A
pedestal 336, located in the SRD module 236, includes a pedestal
support 332 and a pedestal actuator 334. The pedestal 336 supports
the substrate 338 (shown in FIG. 5) on the pedestal upper surface
during processing. The pedestal actuator 334 rotates the pedestal
to spin the substrate and raises and lowers the pedestal as
described below. The substrate may be held in place on the pedestal
by a plurality of clamps 337. The clamps pivot with centrifugal
force and engage the substrate preferably in the edge exclusion
zone of the substrate. In one embodiment, the clamps engage the
substrate only when the substrate lifts off the pedestal during the
processing. Vacuum passages or other holding elements may also be
used. The pedestal has a plurality of pedestal arms 336a and 336b,
so that the fluid through the second nozzle may impact as much
surface area on the lower surface of the substrate as is practical.
An outlet 339 allows fluid to be removed from the SRD module
236.
[0058] A first conduit 346, through which the first fluid flows, is
connected to a valve 347a. The conduit may be hose, pipe, tube, or
other fluid containing conduits. The valve 347a controls the flow
of the first fluid. The valve 347a may be selected from a variety
of valves including a needle, globe, butterfly, or other valve
types and may include a valve actuator, such as a solenoid. The
valve 347a is controlled with a controller 222. The conduit 346
connects to a first fluid inlet 340 that is located above the
substrate and includes a mounting portion 342 to attach to the SRD
module 236 and a connecting portion 344 to attach to the conduit
346. The first fluid inlet is shown with a single first nozzle 348
to deliver a first fluid under pressure onto the substrate upper
surface. However, multiple nozzles could be used and multiple fluid
inlets could be positioned about the inner perimeter of the SRD
module. Preferably, nozzles placed above the substrate should be
outside the diameter of the substrate to lessen the risk of the
nozzles dripping on the substrate. The first fluid inlet could be
mounted in a variety of locations, including through a cover
positioned above the substrate. Additionally, the nozzle may
articulate to a variety of positions using an articulating member
343, such as a ball and socket joint.
[0059] Similar to the first conduit and related elements described
above, a second conduit 352 is connected to a control valve 349a
and a second fluid inlet 350 with a second nozzle 351. The second
fluid inlet 350 is shown below the substrate and angled upward to
direct a second fluid under the substrate through the second nozzle
351. Similar to the first fluid inlet, the second fluid inlet may
include a plurality of nozzles, a plurality of fluid inlets and
mounting locations, and a plurality of orientations including using
the articulating member 353. Each fluid inlet could be extended
into the SRD module 236 at a variety of positions. For instance, if
the flow is desired to be a certain angle that is directed back
toward the SRD module periphery along the edge of the substrate,
the nozzles could be extended radially inward and the discharge
from the nozzles be directed back toward the SRD module
periphery.
[0060] The controller 222 could individually control the two fluids
and their respective flow rates, pressure, and timing, and any
associated valving, as well as the spin cycle(s). The controller
could be remotely located, for instance, in a control panel or
control room and the plumbing controlled with remote actuators. An
alternative embodiment, shown in dashed lines, provides an
auxiliary fluid inlet 346a connected to the first conduit 346 with
a conduit 346b and having a control valve 346c. The alternate
embodiment may be used to flow a rinsing fluid on the backside of
the substrate after the dissolving fluid is applied without having
to reorient the substrate or switch the flow through the second
fluid inlet to a rinsing fluid.
[0061] The controller 222 controls electric voltage or current
supplied to the anode 16 and the seed layer of the substrate 22.
The controller 222, whose components are shown in FIG. 3, comprises
central processing unit (CPU) 260, memory 262, circuit portion 265,
input output interface (I/O) 264, and bus, not shown. The
controller 222 may be a general-purpose computer, a microprocessor,
a microcontroller, or any other known suitable type of computer or
controller. The CPU 260 performs the processing and arithmetic
operations for the controller 222, and controls the operation of
the electricity applied to the anode 16, the seed layer 15 on the
substrate 22, and the operation of the substrate holder system
14.
[0062] The memory 262 includes random access memory (RAM) and read
only memory (ROM) that together store the computer programs,
operands, operators, dimensional values, system processing
temperatures and configurations, and other parameters that control
the electroplating operation. The bus provides for digital
information transmissions between CPU 260, circuit portion 265,
memory 262, and I/O 264. The bus also connects I/O 264 to the
portions of the ECP system 200 that either receive digital
information from, or transmit digital information to, controller
222.
[0063] /O 264 provides an interface to control the transmissions of
digital information between each of the components in controller
222. I/O 264 also provides an interface between the components of
the controller 222 and different portions of the ECP system 200.
Circuit portion 265 comprises all of the other user interface
devices such as display and keyboard, system devices, and other
accessories associated with the controller 222. While one
embodiment of digital controller 222 is described herein, other
digital controllers as well as analog controllers could function
well in this application.
[0064] In one embodiment, the substrate is mounted with the
deposition surface of the disposed face up in the SRD module bowl.
The first fluid inlet generally flows a rinsing fluid, typically
de-ionized water or alcohol. Consequently, the backside of the
substrate is mounted facing down. The fluid flowing through the
second fluid inlet is usually an etching fluid, such as an acid,
including hydrochloric acid, sulfuric acid, phosphoric acid,
hydrofluoric acid, or other dissolving liquids or fluids, depending
on the material to be dissolved. Alternatively, the first fluid and
the second fluid are both rinsing fluids, such as de-ionized water
or alcohol, when the desired process is to rinse the processed
substrate.
[0065] In operation, the pedestal is in a raised position, shown in
FIG. 4, and a robot, not shown, places the substrate, front side
up, onto the pedestal 336. The pedestal lowers the substrate to a
processing position where the substrate is vertically disposed
between the first and the second fluid inlets. Generally, the
pedestal actuator rotates the pedestal between about 0 to about
2500 rpm for a 200 mm substrate. The rotation causes the lower end
337a of the clamps to rotate outward about pivot 337b, toward the
periphery of the SRD module sidewall, due to centrifugal force. The
clamp rotation forces the upper end 337c of the clamp inward and
downward to center and hold the substrate 338 in position on the
pedestal 336, preferably along the substrate edge. The clamps may
rotate into position without touching the substrate and hold the
substrate in position on the pedestal only if the substrate
significantly lifts off the pedestal during processing. With the
pedestal rotating the substrate, a rinsing fluid is delivered onto
the substrate front side through the first fluid inlet 340. The
second fluid, such as an acid, is delivered to the backside surface
through the second fluid inlet to remove any unwanted deposits. The
dissolving fluid chemically reacts with the deposited material,
dissolves, and then flushes the material away from the substrate
backside and other areas where any unwanted deposits are located.
In one embodiment, the rinsing fluid is adjusted to flow at a
greater rate than the dissolving fluid to help protect the front
side of the substrate from the dissolving fluid. The first and
second fluid inlets are located for optimal performance depending
on the size of the substrate 22, the respective flow rates, spray
patterns, and amount and type of deposits to be removed, among
other factors. In some instances, the rinsing fluid could be routed
to the second fluid inlet after a dissolving fluid has dissolved
the unwanted deposits to rinse the backside of the substrate. In
other instances, an auxiliary fluid inlet connected to flow rinsing
fluid on the backside of the substrate could be used to rinse any
dissolving fluid residue from the backside. After rinsing the front
side and/or backside of the substrate, the fluid(s) flow is stopped
and the pedestal continues to rotate, spinning the substrate, and
thereby effectively drying the surface.
[0066] The fluid(s) are generally delivered in a spray pattern,
which may be varied depending on the particular nozzle spray
pattern desired and may include a fan, jet, conical, and other
patterns. One spray pattern for the first and second fluids through
the respective fluid inlets, when the first fluid is a rinsing
fluid, is fan pattern with a pressure of about 10 to about 15
pounds per square inch (psi) and a flow rate of about 1 to about 3
gallons per minute (gpm) for a 200 mm substrate.
[0067] The ECP system 200 could also be used to remove the unwanted
deposits along the edge of the substrate to create an edge
exclusion zone. By adjustment of the orientation and placement of
the nozzles, the flow rates of the fluids, the rotational speed of
the substrate, the chemical composition of the fluids, and the
unwanted deposits can be removed from the edge and/or edge
exclusion zone of the substrate as well. Thus, substantially
preventing dissolution of the deposited material on the front side
surface may not necessarily include the edge or edge exclusion zone
of the substrate. Limiting dissolution of the deposited material on
the front side surface is intended to include at least preventing
the dissolution so that the front side with the deposited material
is not impaired beyond a commercial value.
[0068] One method of accomplishing the edge exclusion zone
dissolution process is to rotate the disk at a slower speed, such
as about 100 to about 1000 rpm, while etching the dissolving fluid
on the backside of the substrate. The centrifugal force moves the
dissolving fluid to the edge of the substrate and forms a layer of
fluid around the edge due to surface tension of the fluid, so that
the dissolving fluid overlaps from the backside to the front side
in the edge area of the substrate. The rotational speed of the
substrate and the flow rate of the dissolving fluid may be used to
determine the extent of the overlap onto the front side. For
instance, a decrease in rotational speed or an increase in flow
results in a less overlap of fluid to the opposing side, e.g., the
front side. Additionally, the flow rate and flow angle of the
rinsing fluid delivered to the front side can be adjusted to offset
the layer of dissolving fluid onto the edge and/or frontside of the
substrate. In some instances, the dissolving fluid may be used
initially without the rinsing fluid to obtain the edge and/or edge
exclusion zone removal, followed by the rinsing/dissolving process
by the SRD module 236.
[0069] The SRD module 236 is connected between the loading station
210 and the mainframe 214. The mainframe 214 generally comprises a
mainframe transfer station 216 and a plurality of processing
stations 218. Referring to FIGS. 2 and 3, the mainframe 214, as
shown, includes two processing stations 218, each processing
station 218 having two process cells 240. The mainframe transfer
station 216 includes a mainframe transfer robot 242. Preferably,
the mainframe transfer robot 242 comprises a plurality of
individual robot arms 244 that provides independent access of
substrates in the processing stations 218 and the SRD stations 212.
As shown in FIG. 3, the mainframe transfer robot 242 comprises two
robot arms 244, corresponding to the number of process cells 240
per processing station 218. Each robot arm 244 includes a robot
blade 246 for holding a substrate during a substrate transfer.
Preferably, each robot arm 244 is operable independently of the
other arm to facilitate independent transfers of substrates in the
system. Alternatively, the robot arms 244 operate in a coordinated
fashion such that one robot extends as the other robot arm
retracts.
[0070] Preferably, the mainframe transfer station 216 includes a
flipper robot 248 that facilitates transfer of a substrate from a
face-up position on the robot blade 246 of the mainframe transfer
robot 242 to a face down position for a process cell 240 that
requires face-down processing of substrates. The flipper robot 248
includes a main body 250 and a flipper robot arm 252. The main body
250 provides both vertical and rotational movements with respect to
a vertical axis of the main body 250. The flipper robot arm 252
provides rotational movement along a horizontal plane along the
flipper robot arm 252. Preferably, a vacuum suction gripper 254,
disposed at the distal end of the flipper robot arm 252, holds the
substrate as the substrate is flipped and transferred by the
flipper robot 248. The flipper robot 248 positions a substrate 234
into the process cell 240 for face-down processing. The details of
the electroplating process cell will be discussed below.
[0071] FIG. 24 is a top schematic view of a mainframe transfer
robot having a flipper robot incorporated therein. The mainframe
transfer robot 242 as shown in FIG. 24 serves to transfer
substrates between different stations attached the mainframe
station, including the processing stations and the SRD stations.
The mainframe transfer robot 242 includes a plurality of robot arms
2402 (two shown), and a flipper type robot blade 2404 is attached
as an end effector for each of the robot arms 2402. Flipper robots
are generally known in the art and can be attached as end effectors
for substrate handling robots, such as model RR701, available from
Rorze Automation, Inc., located in Milpitas, Calif. The main
transfer robot 242 having a flipper robot as the end effector is
capable of transferring substrates between different stations
attached to the mainframe as well as flipping the substrate being
transferred to the desired surface orientation, i.e., substrate
processing surface being face-down for the electroplating process.
Preferably, the mainframe transfer robot 242 provides independent
robot motion along the X-Y-Z axes by the robot arm 2402 and
independent substrate flipping rotation by the flipper type robot
blade 2404. By incorporating the flipper type robot blade 2404 as
the end effector of the mainframe transfer robot, the substrate
transfer process is simplified because the step of passing a
substrate from a mainframe transfer robot 242 to a flipper robot is
eliminated.
[0072] FIG. 6 is a cross sectional view of an electroplating
process cell 400. The electroplating process cell 400 as shown in
FIG. 6 is one embodiment of the electroplating process cell 240 as
shown in FIGS. 2 and 3. The process cell 400 generally comprises a
head assembly 410, a process cell 420 and an electrolyte solution
collector 440.. Preferably, the electrolyte solution collector 440
is secured onto the body 442 of the mainframe 214 over an opening
443 that defines the location for placement of the process cell
420. The electrolyte solution collector 440 includes an inner wall
446, an outer wall 448 and a bottom 447 connecting the walls. An
electrolyte solution outlet 449 is disposed through the bottom 447
of the electrolyte solution collector 440 and connected to the
electrolyte solution system 220 shown in FIG. 2 through tubes,
hoses, pipes or other fluid transfer connectors.
[0073] The head assembly 410 is mounted onto a head assembly frame
452. The head assembly frame 452 includes a mounting post 454 and a
cantilever arm 456. The mounting post 454 is mounted onto the body
442 of the mainframe 214, and the cantilever arm 456 extends
laterally from an upper portion of the mounting post 454.
Preferably, the mounting post 454 provides rotational movement with
respect to a vertical axis along the mounting post to allow
rotation of the head assembly 410 about the mounting post 454. The
head assembly 410 is attached to a mounting plate 460 disposed at
the distal end of the cantilever arm 456. The lower end of the
cantilever arm 456 is connected to a cantilever arm actuator 457,
such as a pneumatic cylinder, mounted on the mounting post 454. The
cantilever arm actuator 457 provides pivotal movement of the
cantilever arm 456 with respect to the joint between the cantilever
arm 456 and the mounting post 454. When the cantilever arm actuator
457 is retracted, the cantilever arm 456 moves the head assembly
410 away from the process cell 420 to provide the spacing required
to remove and/or replace the process cell 420 from the
electroplating process cell 400. When the cantilever arm actuator
457 is extended, the cantilever arm 456 moves the head assembly 410
toward the process cell 420 to position the substrate in the head
assembly 410 in a processing position.
[0074] The head assembly 410 generally comprises a substrate holder
assembly 450 and a substrate assembly actuator 458. The substrate
assembly actuator 458 is mounted onto the mounting plate 460 and
includes a head assembly shaft 462 extending downwardly through the
mounting plate 460. The lower end of the head assembly shaft 462 is
connected to the substrate holder assembly 450 to position the
substrate holder assembly 450 in a processing position and in a
substrate loading position.
[0075] The substrate holder assembly 450 generally comprises a
substrate holder element 464 and an electric contact element 466.
FIG. 7 is a cross sectional view of one embodiment of an electric
contact element 466. In general, the contact ring 466 comprises an
annular body having a plurality of conducting members disposed
thereon. The annular body is constructed of an insulating material
to electrically isolate the plurality of conducting members.
Together the body and conducting members form a diametrically
interior substrate seating surface which, during processing,
supports a substrate and provides a current thereto.
[0076] Referring now to FIG. 7 in detail, the contact ring 466
generally comprises a plurality of conducting members 765 at least
partially disposed within an annular insulative body 770. The
insulative body 770 is shown having a flange 762 and a downward
sloping shoulder portion 764 leading to a substrate seating surface
768. The substrate seating surface 768 is located below the flange
762 such that the flange 762 and the substrate seating surface 768
lie in offset and substantially parallel planes. Thus, the flange
762 may be understood to define a first plane while the substrate
seating surface 768 defines a second plane parallel to the first
plane wherein the shoulder 764 is disposed between the two planes.
However, contact ring design shown in FIG. 7 is intended to be
merely illustrative. In another embodiment, the shoulder portion
764 may be of a steeper angle including a substantially vertical
angle so as to be substantially normal to both the flange 762 and
the substrate seating surface 768. Alternatively, the contact ring
466 may be substantially planar thereby eliminating the shoulder
portion 764. However, for reasons described below, one embodiment
comprises the shoulder portion 764 shown in FIG. 6 or some
variation thereof.
[0077] The conducting members 765 are defined by a plurality of
outer electric contact pads 780 annularly disposed on the flange
762, a plurality of inner electric contact pads 772 disposed on a
portion of the substrate seating surface 768. A plurality of
embedded conducting connectors 776 link the pads 772, 780 to one
another. The conducting members 765 are isolated from one another
by the insulative body 770 that may be made of a plastic such as
polyvinylidenefluoride (PVDF), perfluoroalkoxy resin (PFA),
TEFLON.RTM. (a registered trademark of the E.I. duPont de Nemoirs
and Company of Wilmington, Del.), and TEFZEL.RTM. (a registered
trademark of the E.I. duPont de Nemoirs and Company of Wilmington,
Del.), or any other insulating material such as Alumina
(Al.sub.2O.sub.3) or other ceramics. The outer contact pads 780 are
coupled to a power supply, not shown, to deliver current and
voltage to the inner electric contact pads 772 via the conducting
connectors 776 during processing. In turn, the inner electric
contact pads 772 supply the current and voltage to a substrate by
maintaining contact around a peripheral portion of the substrate.
Thus, in operation the conducting members 765 act as discrete
current paths electrically connected to a substrate.
[0078] Low resistivity, and conversely high conductivity, are
directly related to good plating. To ensure low resistivity, the
conducting members 765 are preferably made of copper (Cu), platinum
(Pt), tantalum (Ta), titanium (Ti), gold (Au), silver (Ag),
stainless steel or other conducting materials. Low resistivity and
low contact resistance may also be achieved by coating the
conducting members 765 with a conducting material. Thus, the
conducting members 765 may, for example, be made of copper having a
resistivity of approximately 2.times.10.sup.-8 .OMEGA..multidot.m
and be coated with platinum having a resistivity of approximately
10.6.times.10.sup.-8 .OMEGA..multidot.m. Coatings such as tantalum
nitride (TaN), titanium nitride (TiN), rhodium (Rh), Au, Cu, or Ag
on a conductive base materials such as stainless steel, molybdenum
(Mo), Cu, and Ti are also possible. Further, since the contact pads
772, 780 are typically separate units bonded to the conducting
connectors 776, the contact pads 772, 780 may comprise one
material, such as Cu, and the conducting members 765 another, such
as stainless steel. Either or both of the pads 772, 780 and
conducting connectors 776 may be coated with a conducting material.
Additionally, because plating repeatability may be adversely
affected by oxidation that acts as an insulator, the inner electric
contact pads 772 preferably comprise a material resistant to
oxidation such as Pt, Ag, or Au.
[0079] In addition to being a function of the contact material, the
total resistance of each circuit is dependent on the geometry, or
shape, of the inner contact inner electric contact pads 772 and the
force supplied by the contact ring 466. These factors define a
constriction resistance, R.sub.CR, at the interface of the inner
electric contact pads 772 and the substrate seating surface 768 due
to asperaties between the two surfaces. Generally, as the applied
force is increased the apparent area is also increased. The
apparent area is inversely related to R.sub.CR so that an increase
in the apparent area results in a decreased R.sub.CR. Thus, to
minimize overall resistance it is preferable to maximize force. The
maximum force applied in operation is limited by the yield strength
of a substrate that may be damaged under excessive force and
resulting pressure. However, because pressure is related to both
force and area, the maximum sustainable force is also dependent on
the geometry of the inner electric contact pads 772. Thus, while
the contact pads 772 may have a flat upper surface as in FIG. 7,
other shapes may be used to advantage. For example, two preferred
shapes are shown in FIGS. 8 and 9. FIG. 8 shows a knife-edge
contact pad and FIG. 9 shows a hemispherical contact pad. A person
skilled in the art will readily recognize other shapes which may be
used to advantage. A more complete discussion of the relation
between contact geometry, force, and resistance is given in Ney
Contact Manual, by Kenneth E. Pitney, The J. M. Ney Company, 1973,
which is hereby incorporated by reference in its entirety.
[0080] The number of conducting connectors 776 may be varied
depending on the particular number of contact pads 772 desired,
shown in FIG. 7. For a 200 mm substrate, preferably at least
twenty-four conducting connectors 776 are spaced equally over
360.degree.. However, as the number of connectors reaches a
critical level, the compliance of the substrate relative to the
contact ring 466 is adversely affected. Therefore, while more than
twenty-four conducting connectors 776 may be used, contact
uniformity may eventually diminish depending on the topography of
the contact pads 772 and the substrate stiffness. Similarly, while
less than twenty-four conducting connectors 776 may be used,
current flow is increasingly restricted and localized, leading to
poor plating results. Since the dimensions are readily altered to
suit a particular application. For example, the number of
converters, the spacing between adjacent connectors, and the
periphery of the circle that the connectors are mounted on may
change between a process cell used for a 200 mm substrate and a
process cell used for a 300 mm substrate.
[0081] As shown in FIG. 10, the substrate seating surface 768
comprises an isolation gasket 782 disposed on the insulative body
770. The substrate seating surface extends diametrically interior
to the inner electric contact pads 772 to define the inner diameter
of the contact ring 466. The isolation gasket 782 preferably
extends slightly above the inner electric contact pads 772, e.g., a
few mils, and preferably comprises an elastomer such as VITON.RTM.
(a registered trademark of the E.I. duPont de Nemoirs and Company
of Wilmington, Del.), TEFLON.RTM., buna rubber, and the like. Where
the insulative body 770 also comprises an elastomer the isolation
gasket 782 may be of the same material. In the latter embodiment,
the isolation gasket 782 and the insulative body 770 may be
monolithic, i.e., formed as a single piece. However, the isolation
gasket 782 is preferably separate from the insulative body 770 so
that it may be easily removed for replacement or cleaning.
[0082] While FIG. 10 shows one embodiment of the isolation gasket
782 wherein the isolation gasket is seated entirely on the
insulative body 770, FIGS. 8 and 9 show an alternative embodiment.
In the latter embodiment, the insulative body 770 is partially
machined away to expose the upper surface of the conducting
connectors 776 and the isolation gasket 782 is disposed thereon.
Thus, the isolation gasket 782 contacts a portion of the conducting
connectors 776. This design requires less material to be used for
the inner electric contact pads 772 that may be advantageous where
material costs are significant such as when the inner electric
contact pads 772 comprise gold. Persons skilled in the art will
recognize other embodiments.
[0083] During processing, the isolation gasket 782 maintains
contact with a peripheral portion of the substrate plating surface
and is compressed to provide a seal between the remaining electric
contact element 466 and the substrate. The seal prevents the
electrolyte solution from contacting the edge and backside of the
substrate. As noted above, maintaining a clean contact surface is
necessary to achieving high plating repeatability. Previous contact
ring designs did not provide consistent plating results because
contact surface topography varied over time. The contact ring
limits, or substantially minimizes, deposits that would otherwise
accumulate on the inner electric contact pads 772 and change their
characteristics thereby producing highly repeatable, consistent,
and uniform plating across the substrate plating surface.
[0084] FIG. 11 is a simplified schematic diagram representing a
possible configuration of the electric circuit for the contact ring
466. To provide a uniform current distribution between the
conducting members 765, an external resistor 700 is connected in
series with each of the conducting members 765. Preferably, the
resistance value of the external resistor 700, represented as
R.sub.EXT, is much greater than the resistance of any other
component of the circuit. As shown in FIG. 11, the electric circuit
through each conducting member 765 is represented by the resistance
of each of the components connected in series with the power supply
702. R.sub.E represents the resistance of the electrolyte solution,
which is typically dependent on the distance between the anode and
the electric contact element and the composition of the electrolyte
solution chemistry. Thus, R.sub.A represents the resistance of the
electrolyte solution adjacent the substrate plating surface 754.
R.sub.S represents the resistance of the substrate plating surface
754, and R.sub.C represents the resistance of the conducting
members 765 plus the constriction resistance resulting at the
interface between the inner electric contact pads 772 and the
substrate plating surface 754. Generally, the resistance value of
the external resistor (R.sub.EXT) is at least as much as .SIGMA.R,
where .SIGMA.R equals the sum of R.sub.E, R.sub.A, R.sub.S and
R.sub.C. Preferably, the resistance value of the external resistor
(R.sub.EXT) is much greater than .SIGMA.R such that .SIGMA.R is
negligible and the resistance of each series circuit approximates
R.sub.EXT.
[0085] Typically, one power supply is connected to all of the outer
contact pads 780 of the electric contact element 466, resulting in
parallel circuits through the inner electric contact pads 772.
However, as the inner electric contact pad-to-substrate interface
resistance varies with each inner electric contact pad 772, more
current will flow, and thus more plating will occur, at the site of
lowest resistance. However, by placing an external resistor in
series with each conducting member 765, the value or quantity of
electric current passed through each conducting member 765 becomes
controlled mainly by the value of the external resistor. The
variations in the electric properties between each of the inner
electric contact pads 772 do not affect the current distribution on
the substrate. A uniform current density results across the plating
surface that contributes to a uniform plating thickness. The
external resistors also provide a uniform current distribution
between different substrates of a process-sequence.
[0086] Although the contact ring 466 is designed to resist deposit
buildup on the inner electric contact pads 772, over multiple
substrate plating cycles the substrate-pad interface resistance may
increase, eventually reaching an unacceptable value. An electronic
sensor/alarm 704 can be connected across the external resistor 700
to monitor the voltage/current across the external resistor to
address this problem. If the voltage/current across the external
resistor 700 falls outside of a preset operating range that is
indicative of a high substrate-pad resistance, the sensor/alarm 704
triggers corrective measures such as shutting down the plating
process until the problems are corrected by an operator.
Alternatively, a separate power supply can be connected to each
conducting member 765 and can be separately controlled and
monitored to provide a uniform current distribution across the
substrate. A very smart system (VSS) may also be used to modulate
the current flow. The VSS typically comprises a processing unit and
any combination of devices known in the industry used to supply
and/or control current such as variable resistors, separate power
supplies, etc. As the physiochemical, and hence electric,
properties of the inner electric contact pads 772 change over time,
the VSS processes and analyzes data feedback. The data is compared
to pre-established setpoints and the VSS then makes appropriate
current and voltage alterations to ensure uniform deposition.
[0087] FIG. 18 is a perspective view of an alternative embodiment
of an electric contact element. The electric contact element 1800
as shown in FIG. 18 comprises a conductive metal or a metal alloy,
such as stainless steel, copper, silver, gold, platinum, titanium,
tantalum, and other conductive materials, or a combination of
conductive materials, such as stainless steel coated with platinum.
The electric contact element 1800 includes an upper mounting
portion 1810 adapted for mounting the electric contact element onto
the substrate holder assembly and a lower substrate receiving
portion 1820 adapted for receiving a substrate therein. The
substrate receiving portion 1820 includes an annular substrate
seating surface 1822 having a plurality of contact pads or bumps
1824 disposed thereon and preferably evenly spaced apart. When a
substrate is positioned on the substrate seating surface 1822, the
contact pads 1824 physically contact a peripheral region of the
substrate to provide electric contact to the electroplating seed
layer on the substrate deposition surface. Preferably, the contact
pads 1824 are coated with a noble metal, such as platinum or gold,
that is resistant to oxidation.
[0088] The exposed surfaces of the electric contact element, except
the surfaces of the contact pads that come in contact with the
substrate, are preferably treated to provide hydrophilic surfaces
or coated with a material that exhibits hydrophilic properties.
Hydrophilic materials and hydrophilic surface treatments are known
in the art. One company providing a hydrophilic surface treatment
is Millipore Corporation, located in Bedford, Mass. The hydrophilic
surface significantly reduces beading of the electrolyte solution
on the surfaces of the electric contact element and promotes smooth
dripping of the electrolyte solution from the electric contact
element after the electric contact element is removed from the
electroplating bath or electrolyte solution. By providing
hydrophilic surfaces on the electric contact element that
facilitate run-off of the electrolyte solution, plating defects
caused by residual electrolyte solution on the electric contact
element are significantly reduced. The inventors also contemplate
application of this hydrophilic treatment or coating in other
embodiments of electric contact elements to reduce residual
electrolyte solution beading on the electric contact element and
the plating defects on a subsequently processed substrate that may
result therefrom.
[0089] Referring to FIGS. 12 and 12A, one embodiment of substrate
holder element element 464 is provided that is preferably
positioned above the electric contact element 466 and comprises a
bladder assembly 470 that provides pressure to the backside of a
substrate and ensures electric contact between the substrate
plating surface and the electric contact element 466. The
inflatable bladder assembly 470 is disposed on a substrate holder
plate 832. A bladder 836 disposed on a lower surface of the
substrate holder plate 832 is thus located opposite and adjacent to
the contacts on the electric contact element 466 with the substrate
821 interposed therebetween. A fluid source 838 supplies a fluid,
i.e., a gas or liquid, to the bladder 836 allowing the bladder 836
to be inflated to varying degrees. While this embodiment of
substrate holder is provided in which the substrate is attached to
the substrate holder plate 838. It is typical that a thrust plate
may be utilized in a substrate holder system so that the thrust
plate exerts a biasing force against the backside of the substrate
so the seed layer, on the front side, is biased into contact with
the electronic contact elements.
[0090] Referring now to FIGS. 12, 12A, and 13, the details of one
embodiment of the bladder assembly 470 is discussed. The substrate
holder plate 832 is shown as substantially disc-shaped having an
annular recess 840 formed on a lower surface and a centrally
disposed vacuum port 841. One or more inlets 842 are formed in the
substrate holder plate 832 and lead into the relatively enlarged
annular mounting channel 843 and the annular recess 840.
Quick-disconnect hoses 844 couple the fluid source 838 to the
inlets 842 to provide a fluid thereto. The vacuum port 841 is
preferably attached to a vacuum/pressure pumping system 859 adapted
to selectively supply a pressure or create a vacuum at a backside
of the substrate 821. The pumping system 859, shown in FIG. 12,
comprises a pump 845, a cross-over valve 847, and a vacuum ejector
849, commonly known as a venturi. One vacuum ejector that may be
used to advantage is available from SMC Pneumatics, Inc., of
Indianapolis, Ind. The pump 845 may be a commercially available
compressed gas source and is coupled to one end of a hose 851, the
other end of the hose 851 being coupled to the vacuum port 841. The
hose 851 is split into a pressure line 853 and a vacuum line 855
having the vacuum ejector 849 disposed therein. Fluid flow is
controlled by the cross-over valve 847 that selectively switches
communication with the pump 845 between the pressure line 853 and
the vacuum line 855. Preferably, the cross-over valve has an OFF
setting whereby fluid is restricted from flowing in either
direction through hose 851. A shut-off valve 861 disposed in hose
851 prevents fluid from flowing from pressure line 855 upstream
through the vacuum ejector 849. The desired direction of fluid flow
is indicated by arrows.
[0091] Where the fluid source 838 is a gas supply it may be coupled
to hose 851 thereby eliminating the need for a separate compressed
gas supply, i.e., pump 845. Further, a separate gas supply and
vacuum pump may supply the backside pressure and vacuum conditions.
While it is preferable to allow for both a backside pressure as
well as a backside vacuum, a simplified embodiment may comprise a
pump capable of supplying only a backside vacuum. However, as will
be explained below, deposition uniformity may be improved where a
backside pressure is provided during processing. Therefore, an
arrangement such as the one described above including a vacuum
ejector and a cross-over valve is preferred.
[0092] Referring now to FIGS. 12A and 14, a substantially circular
ring-shaped manifold 846 is disposed in the annular recess 840. The
manifold 846 comprises a mounting rail 852 disposed between an
inner shoulder 848 and an outer shoulder 850. The mounting rail 852
is adapted to be at least partially inserted into the annular
mounting channel 843. A plurality of fluid outlets 854 formed in
the manifold 846 provide communication between the inlets 842 and
the bladder 836. Seals 837, such as O-rings, are disposed in the
annular manifold channel 843 in alignment with the inlet 842 and
outlet 854 and secured by the substrate holder plate 832 to ensure
an airtight seal. Conventional fasteners, not shown, such as screws
may be used to secure the manifold 846 to the substrate holder
plate 832 via cooperating threaded bores, not shown, formed in the
manifold 846 and the substrate holder plate 832.
[0093] Referring now to FIG. 15, the bladder 836 is shown, in
section, as an elongated substantially semi-tubular piece of
material having annular lip seals 856, or nodules, at each edge. In
FIG. 12A, the lip seals 856 are shown disposed on the inner
shoulder 848 and the outer shoulder 850. A portion of the bladder
836 is compressed against the walls of the annular recess 840 by
the manifold 846 which has a width slightly less, e.g. a few
millimeters, than the annular recess 840. Thus, the manifold 846,
the bladder 836, and the annular recess 840 cooperate to form a
fluid-tight seal. To prevent fluid loss, the bladder 836 is
preferably comprised of some fluid impervious material such as
silicon rubber or any comparable elastomer that is chemically inert
with respect to the electrolyte solution and exhibits reliable
elasticity. Where needed a compliant covering 857 may be disposed
over the bladder 836, as shown in FIG. 15, and secured by means of
an adhesive or thermal bonding. The covering 857 preferably
comprises an elastomer such as VITON.RTM. (a registered trademark
of the E.I. duPont de Nemoirs and Company of Wilmington, Del.),
buna rubber or the like. The covering may be reinforced by
KEVLAR.RTM. (a registered trademark of the E.I. duPont de Nemoirs
and Company of Wilmington, Del.), for example. In one embodiment,
the covering 857 and the bladder 836 comprise the same material.
The covering 857 has particular application where the bladder 836
is liable to rupturing. Alternatively, the bladder 836 thickness
may simply be increased during its manufacturing to reduce the
likelihood of puncture. Preferably, the exposed surface of the
bladder 836, if uncovered, and the exposed surface of the covering
857 are coated or treated to provide a hydrophilic surface as
discussed above for the surfaces of the electric contact element.
The hydrophilic surface promotes dripping and removal of the
residual electrolyte solution after the head assembly is lifted
above the process cell.
[0094] The precise number of inlets 842 and outlets 854 may be
varied according to the particular application. For example, while
FIG. 12 shows two inlets with corresponding outlets, an alternative
embodiment could employ a single fluid inlet that supplies fluid to
the bladder 836.
[0095] In operation, the substrate 821 is introduced into the
container body 802 by securing it to the lower side of the
substrate holder plate 832. This is accomplished by engaging the
pumping system 159 to evacuate the space between the substrate 821
and the substrate holder plate 832 via port 841 thereby creating a
vacuum condition. The bladder 836 is then inflated by supplying a
fluid such as air or water from the fluid source 838 to the inlets
842. The fluid is delivered into the bladder 836 via the manifold
outlets 854, thereby pressing the substrate 821 uniformly against
the contacts of the electric contact element 466. The
electroplating process is then carried out. Electrolyte solution is
then pumped into the process cell 420 toward the substrate 821 to
contact the exposed substrate plating surface 820. The power supply
provides a negative bias to the substrate plating surface 820 via
the electric contact element 466. As the electrolyte solution is
flowed across the substrate plating surface 820, ions in the
electrolytic solution are attracted to the surface 820 and deposit
on the surface 820 to form the desired film.
[0096] Because of its flexibility, the bladder 836 deforms to
accommodate the asperaties of the substrate backside and contacts
of the electric contact element 466 thereby mitigating misalignment
with the conducting electric contact element 466. The compliant
bladder 836 prevents the electrolyte solution from contaminating
the backside of the substrate 821 by establishing a fluid tight
seal at a perimeter portion of a backside of the substrate 821.
Once inflated, a uniform pressure is delivered downward toward the
electric contact element 466 to achieve substantially equal force
at all points where the substrate 821 and electric contact element
466 interface. The force can be varied as a function of the
pressure supplied by the fluid source 838. Further, the
effectiveness of the bladder assembly 470 is not dependent on the
configuration of the electric contact element 466. For example,
while FIG. 12 shows a pin configuration having a plurality of
discrete contact points, the electric contact element 466 may also
be a continuous surface.
[0097] Because the force delivered to the substrate 821 by the
bladder 836 is variable, adjustments can be made to the current
flow supplied by the contact ring 466. As described above, an oxide
layer may form on the electric contact element 466 and act to
restrict current flow. However, increasing the pressure of the
bladder 836 may counteract the current flow restriction due to
oxidation. As the pressure is increased, the malleable oxide layer
is compromised and superior contact between the electric contact
element 466 and the substrate 821 results. The effectiveness of the
bladder 836 in this capacity may be further improved by altering
the geometry of the electric contact element 466. For example, a
knife-edge geometry is likely to penetrate the oxide layer more
easily than a dull rounded edge or flat edge.
[0098] Additionally, the fluid tight seal provided by the inflated
bladder 836 allows the pump 845 to maintain a backside vacuum or
pressure either selectively or continuously, before, during, and
after processing. Generally, however, the pump 845 is run to
maintain a vacuum only during the transfer of substrates to and
from the electroplating process cell 400 because it has been found
that the bladder 836 is capable of maintaining the backside vacuum
condition during processing without continuous pumping. Thus, while
inflating the bladder 836, as described above, the backside vacuum
condition is simultaneously relieved by disengaging the pumping
system 859, e.g., by selecting an OFF position on the cross-over
valve 847. Disengaging the pumping system 859 may be abrupt or
comprise a gradual process whereby the vacuum condition is ramped
down. Ramping allows for a controlled exchange between the
inflating bladder 836 and the simultaneously decreasing backside
vacuum condition. This exchange may be controlled manually or by
computer.
[0099] As described above, continuous backside vacuum pumping while
the bladder 836 is inflated is not needed and may actually cause
the substrate 820 to buckle or warp leading to undesirable
deposition results. It may, however, be desirable to provide a
backside pressure to the substrate 820 in order to cause a "bowing"
effect of the substrate to be processed. Bowing (i.e., curving the
surface) the substrate may result in a desired deposition profile
across the radius of the substrate. Thus, pumping system 859 is
capable of selectively providing a vacuum or pressure condition to
the substrate backside. For a 200 mm substrate a backside pressure
up to 5 psi is preferable to bow the substrate. Because substrates
typically exhibit some measure of pliability, a backside pressure
causes the substrate to bow or assume a convex shape relative to
the upward flow of the electrolyte solution. The degree of bowing
is variable according to the pressure supplied by pumping system
859.
[0100] While FIG. 12A shows one embodiment of bladder 836 having a
surface area sufficient to cover a relatively small perimeter
portion of the substrate backside at a diameter substantially equal
to the electric contact element 466, the bladder assembly 470 may
be geometrically varied. Thus, the bladder assembly may be
constructed using more fluid impervious material to cover an
increased surface area of the substrate 821.
[0101] FIG. 19 is a partial cross sectional view of an alternative
embodiment of a substrate holder assembly. The alternative
substrate holder assembly 1900 comprises a bladder assembly 470, as
described above, having the inflatable bladder 836 attached to the
back surface of an intermediary substrate holder plate 1910.
Preferably, a portion of the inflatable bladder 836 is sealingly
attached to the back surface 1912 of the intermediary substrate
holder plate 1910 using an adhesive or other bonding material. The
front surface 1914 of the intermediary substrate holder plate 1910
is adapted to receive a substrate 821 to be processed, and an
elastomeric o-ring 1916 is disposed in an annular groove 1918 on
the front surface 1914 of the intermediary substrate holder plate
1910 to contact a peripheral portion of the substrate back surface.
The elastomeric o-ring 1916 provides a seal between the substrate
back surface and the front surface of the intermediary substrate
holder plate. Preferably, the intermediary substrate holder plate
includes a plurality of bores or holes 1920 extending through the
plate that are in fluid communication with the vacuum port 841 to
facilitate securing the substrate on the substrate holder using a
vacuum force applied to the backside of the substrate. According to
this alternative embodiment of the substrate holder assembly, the
inflatable bladder does not directly contact a substrate being
processed, and thus the risk of cutting or damaging the inflatable
bladder during substrate transfers is significantly reduced. The
elastomeric O-ring 1916 is preferably coated or treated to provide
a hydrophilic surface, as discussed above for the surfaces of the
electric contact element, for contacting the substrate, and the
elastomeric O-ring 1916 is replaced as needed to ensure proper
contact and seal to the substrate.
[0102] In one embodiment, the uniformity of the deposited film so
the maximum deviation of deposited film thickness is at about 2% of
the average film thickness, while standard electroplating processes
typically achieves uniformity at best within about 5.5%. However,
rotation of the head assembly is not necessary to achieve uniform
electroplating deposition in some instances, particularly where the
uniformity of electroplating deposition is achieved by adjusting
the processing parameters, such as the electrolyte solution
chemistry, electrolyte solution flow and other parameters.
[0103] Referring back to FIG. 6, a cross sectional view of an
electroplating process cell 400, the substrate holder assembly 450
is positioned above the process cell 420. The process cell 420
generally comprises a bowl 430, a container body 472, an anode
assembly 474 and a filter 476. Preferably, the anode assembly 474
is disposed below the container body 472 and attached to a lower
portion of the container body 472, and the filter 476 is disposed
between the anode assembly 474 and the container body 472. The
container body 472 is preferably a cylindrical body comprised of an
electrically insulative material, such as ceramics, plastics,
PLEXIGLAS.RTM. (acrylic), lexane, PVC, CPVC, and PVDF.
Alternatively, the container body 472 can be made from a metal,
such as stainless steel, nickel and titanium, which is coated with
an insulating layer, such as TEFLON.RTM., PVDF, plastic, rubber and
other combinations of materials that do not dissolve in the
electrolyte solution and can be electrically insulated from the
electrodes, i.e., the anode and cathode of the ECP system. The
container body 472 is preferably sized and adapted to conform to
the substrate plating surface and the shape of the substrate being
processed through the system, the substrate is typically either
circular or rectangular in shape. One preferred embodiment of the
container body 472 comprises a cylindrical ceramic tube having an
inner diameter that has about the same dimension as or slightly
larger than the substrate diameter. The inventors have discovered
that the rotational movement typically required in typical ECP
system s is not required to achieve uniform plating results when
the size of the container body conforms to about the size of the
substrate plating surface.
[0104] An upper portion of the container body 472 extends radially
outwardly to form an annular weir 478. The weir 478 extends over
the inner wall 446 of the electrolyte solution collector 440 and
allows the electrolyte solution to flow into the electrolyte
solution collector 440. The upper surface of the weir 478
preferably matches the lower surface of the electric contact
element 466. Preferably, the upper surface of the weir 478 includes
an inner annular flat portion 480, a middle inclined portion 482
and an outer declined portion 484. When a substrate is positioned
in the processing position, the substrate plating surface is
positioned above the cylindrical opening of the container body 472,
and a gap for electrolyte solution flow is formed between the lower
surface of the electric contact element 466 and the upper surface
of the weir 478. The lower surface of the electric contact element
466 is disposed above the inner flat portion 480 and the middle
inclined portion of the weir 478. The outer declined portion 484 is
sloped downwardly to facilitate flow of the electrolyte solution
into the electrolyte solution collector 440.
[0105] A lower portion of the container body 472 extends radially
outwardly to form a lower annular flange 486 for securing the
container body 472 to the bowl 430. The outer dimension, i.e.,
circumference, of the annular flange 486 is smaller than the
dimensions of the opening 444 and the inner circumference of the
electrolyte solution collector 440. These relative dimensions allow
removal and replacement of the process cell 420 from the
electroplating process cell 400. Preferably, a plurality of bolts
488 are fixedly disposed on the annular flange 486 and extend
downwardly through matching bolt holes on the bowl 430. A plurality
of removable fastener nuts 490 secure the process cell 420 onto the
bowl 430. A seal 487, such as an elastomer O-ring, is disposed
between container body 472 and the bowl 430 radially inwardly from
the bolts 488 to prevent leaks from the process cell 420. The
nuts/bolts combination facilitates fast and easy removal and
replacement of the components of the process cell 420 during
maintenance.
[0106] Preferably, the filter 476 is attached to and completely
covers the lower opening of the container body 472, and the anode
assembly 474 is disposed below the filter 476. A spacer 492 is
disposed between the filter 476 and the anode assembly 474.
Preferably, the filter 476, the spacer 492, and the anode assembly
474 are fastened to a lower surface of the container body 472 using
removable fasteners, such as screws and/or bolts. Alternatively,
the filter 476, the spacer 492, and the anode assembly 474 are
removably secured to the bowl 430.
[0107] The anode assembly 474 preferably comprises a consumable
anode that serves as a metal source in the electrolyte solution.
Alternatively, the anode assembly 474 comprises a non-consumable
anode, and the metal to be electroplated is supplied within the
electrolyte solution from the electrolyte solution system 220. As
shown in FIG. 6, the anode assembly 474 is a self-enclosed module
having a porous anode enclosure 494 preferably made of the same
metal as the metal to be electroplated, such as copper.
Alternatively, the anode enclosure 494 is made of porous materials,
such as ceramics or polymeric membranes. A soluble metal 496, such
as high purity copper for electrochemical plating of copper, is
disposed within the anode enclosure 494. The soluble metal 496
preferably comprises metal particles, wires or a perforated sheet.
The porous anode enclosure 494 also acts as a filter that keeps the
particulates generated by the dissolving metal within the anode
enclosure 494. As compared to a non-consumable anode, the
consumable, i.e., soluble, anode provides gas-generation-free
electrolyte solution and minimizes the need to constantly replenish
the metal in the electrolyte solution.
[0108] An anode electrode contact 498 is inserted through the anode
enclosure 494 to provide electric connection to the soluble metal
496 from a power supply. Preferably, the anode electrode contact
498 is made from a conductive material that is insoluble in the
electrolyte solution, such as titanium, platinum and
platinum-coated stainless steel. The anode electrode contact 498
extends through the bowl 430 and is connected to an electric power
supply. Preferably, the anode electric contact 498 includes a
threaded portion 497 for a fastener nut 499 to secure the anode
electric contact 498 to the bowl 430, and a seal 495, such as a
elastomer washer, is disposed between the fastener nut 499 and the
bowl 430 to prevent leaks from the process cell 420.
[0109] The bowl 430 generally comprises a cylindrical portion 502
and a bottom portion 504. An upper annular flange 506 extends
radially outwardly from the top of the cylindrical portion 502. The
upper annular flange 506 includes a plurality of holes 508 that
matches the number of bolts 488 from the lower annular flange 486
of the container body 472. To secure the upper annular flange 506
of the bowl 430 and the lower annular flange 486 of the container
body 472, the bolts 488 are inserted through the holes 508, and the
fastener nuts 490 are fastened onto the bolts 488. Preferably, the
outer dimension, i.e., circumference, of the upper annular flange
506 is about the same as the outer dimension, i.e., circumference,
of the lower annular flange 486. Preferably, the lower surface of
the upper annular flange 506 of the bowl 430 rests on a support
flange of the mainframe 214 when the process cell 420 is positioned
on the mainframe 214.
[0110] The inner circumference of the cylindrical portion 502
accommodates the anode assembly 474 and the filter 476. Preferably,
the outer dimensions of the filter 476 and the anode assembly 474
are slightly smaller than the inner dimension of the cylindrical
portion 502 to force a substantial portion of the electrolyte
solution to flow through the anode assembly 474 first before
flowing through the filter 476. The bottom portion 504 of the bowl
430 includes an electrolyte solution inlet 510 that connects to an
electrolyte solution supply line from the electrolyte solution
system 220. Preferably, the anode assembly 474 is disposed about a
middle portion of the cylindrical portion 502 of the bowl 430 to
provide a gap for electrolyte solution flow between the anode
assembly 474 and the electrolyte solution inlet 510 on the bottom
portion 504.
[0111] The electrolyte solution inlet 510 and the electrolyte
solution supply line are preferably connected by a releasable
connector that facilitates easy removal and replacement of the
process cell 420. When the process cell 420 needs maintenance, the
electrolyte solution is drained from the process cell 420, and the
electrolyte solution flow in the electrolyte solution supply line
is discontinued and drained. The connector for the electrolyte
solution supply line is released from the electrolyte solution
inlet 510, and the electric connection to the anode assembly 474 is
also disconnected. The head assembly 410 is raised or rotated to
provide clearance for removal of the process cell 420. The process
cell 420 is then removed from the mainframe 214, and a new or
reconditioned is replaced into the mainframe 214.
[0112] Alternatively, the bowl 430 can be secured onto the support
flange of the mainframe 214, and the container body 472 along with
the anode and the filter are removed for maintenance. In this case,
the nuts securing the anode assembly 474 and the container body 472
to the bowl 430 are removed to facilitate removal of the anode
assembly 474 and the container body 472. New or reconditioned anode
assembly 474 and container body 472 are then replaced into the
mainframe 214 and secured to the bowl 430.
[0113] FIG. 20 is a cross sectional view of one embodiment of an
encapsulated anode. The encapsulated anode 2000 includes a
permeable anode enclosure that filters or traps "anode sludge" or
particulates generated as the metal is dissolved from the anode
plate 2004. As shown in FIG. 20, the consumable anode plate 2004
comprises a solid piece of copper enclosed in a hydrophilic anode
encapsulation membrane 2002. Preferably, the copper is a high
purity, oxygen free copper. The anode plate 2004 is secured and
supported by a plurality of electric contacts or feed-throughs 2006
that extend through the bottom of the bowl 430. The electric
contacts or feed-throughs 2006 extend through the anode
encapsulation membrane 2002 into the bottom surface of the anode
plate 2004. The flow of the electrolyte solution is indicated by
the arrows A from the electrolyte solution inlet 510 disposed at
the bottom of the bowl 430 through the gap between the anode and
the bowl sidewall. The electrolyte solution also flows through the
anode encapsulation membrane 2002 by permeation into and out of the
gap between the anode encapsulation membrane and the anode plate,
as indicated by the arrows B. Preferably, the anode encapsulation
membrane 2002 comprises a hydrophilic porous membrane, such as a
modified polyvinyllidene fluoride membrane, having porosity between
about 60% and 80%, more preferably about 70%, and pore sizes
between about 0.025 .mu.m and about 1 .mu.m, more preferably
between about 0.1 .mu.m and about 0.2 .mu.m. One example of a
hydrophilic porous membrane is the Durapore Hydrophilic Membrane,
available from Millipore Corporation, located in Bedford, Mass. As
the electrolyte solution flows through the encapsulation membrane,
anode sludge and particulates generated by the dissolving anode are
filtered or trapped by the encapsulation membrane. Thus, the
encapsulation membranes improve the purity of the electrolyte
solution during the electroplating process, and defect formations
on the substrate during the electroplating process caused by anode
sludge and contaminant particulates are significantly reduced.
[0114] FIG. 21 is a cross sectional view of another embodiment of
an encapsulated anode. The anode plate 2004 is secured and
supported on the electric feed-throughs 2006. A top encapsulation
membrane 2008 and a bottom encapsulation membrane 2010, disposed
respectively above and below the anode plate 2004, are attached to
a membrane support ring 2012 that is disposed around the anode
plate 2004. The top and bottom encapsulation membranes 2008, 2010
comprise a material from the list above for encapsulation membrane
of the encapsulated anode. The membrane support ring 2012
preferably comprises a relatively rigid material as compared to the
encapsulation membrane, such as plastic or other polymers. A bypass
fluid inlet 2014 is disposed through the bottom of the bowl 430 and
through the bottom encapsulation membrane 2010 to introduce
electrolyte solution into the gap between the encapsulation
membranes and the anode plate. A bypass outlet 2016 is connected to
the membrane support ring 2012 and extends through the bowl 430 to
facilitate flow of excess electrolyte solution with the anode
sludge or generated particulates out of the encapsulated anode into
a waste drain, not shown.
[0115] Preferably, the flow of the electrolyte solution within the
bypass fluid inlet 2014 and the main electrolyte solution inlet 510
are individually controlled by flow control valves 2020, 2022,
respectively placed along the fluid lines connected to the inlets,
and the fluid pressure in the bypass fluid inlet 2014 is preferably
maintained at a higher pressure than the pressure in the main
electrolyte solution inlet 510. The flow of the electrolyte
solution inside the bowl 430 from the main electrolyte solution
inlet 510 is indicated by arrows A, and the flow of the electrolyte
solution inside the encapsulated anode 2000 is indicated by the
arrows B. A portion of the electrolyte solution introduced into the
encapsulated anode flows out of the encapsulated anode through the
bypass outlet 2016. By providing a dedicated bypass electrolyte
solution supply into the encapsulated anode, the anode sludge or
particulates generated from the dissolving consumable anode is
continually removed from the anode, thereby improving the purity of
the electrolyte solution during the electroplating process.
[0116] FIG. 22 is a cross sectional view of a yet another
embodiment of an encapsulated anode. This embodiment of an
encapsulated anode 2000 includes an anode plate 2004, a plurality
of electric feed-throughs 2006, a top encapsulation membrane 2008,
a bottom encapsulation membrane 2010, and a membrane support ring
2012. The anode plate 2004 is secured and supported on a plurality
of electric feed-throughs 2006. The top and bottom encapsulation
membrane 2008, 2010 are attached to a membrane support ring 2012. A
bypass outlet 2016 is connected to the membrane support ring 2012,
and extends through the bowl 430. This embodiment of an
encapsulated anode preferably comprises materials as described for
the first encapsulated anode. The bottom encapsulation membrane
2010 includes one or more openings 2024 disposed substantially
above the main electrolyte solution inlet 510. The opening 2024 is
adapted to receive flow of electrolyte solution from the main
electrolyte solution inlet 510 and is preferably about the same
size as the internal circumference of the main electrolyte solution
inlet 510. The flow of the electrolyte solution from the main
electrolyte solution inlet 510 is indicated by the arrows A and the
flow of the electrolyte solution within the encapsulated anode is
indicated by the arrows B. A portion of the electrolyte solution
flows out of the encapsulated anode through the bypass outlet 2016,
carrying a portion of the anode sludge and particulates generated
from anode dissolution.
[0117] FIG. 23 is a cross sectional view of yet another embodiment
of an encapsulated anode. This embodiment of an encapsulated anode
2000 includes an anode plate 2002, a plurality of electric
feed-throughs 2006, a top encapsulation membrane 2008, a bottom
encapsulation membrane 2010, and a membrane support ring 2012. The
anode plate 2004 is secured and supported on a plurality of
electric feed-throughs 2006. The top and a bottom encapsulation
membrane 2008, 2010 are attached to a membrane support ring 2012. A
bypass fluid inlet 2014 is disposed through the bottom of the bowl
430 and through the bottom encapsulation membrane 2010 to introduce
electrolyte solution into the gap between the encapsulation
membranes and the anode plate. This embodiment of an encapsulated
anode preferably comprises materials as described for the
encapsulated anode. Preferably, the flow of the electrolyte
solution through the bypass fluid inlet 2014 and the main
electrolyte solution inlet 510 are individually controlled by
control valves 2020, 2022, respectively. The flow of the
electrolyte solution from the main electrolyte solution inlet 510
is indicated by the arrows A while the flow of the electrolyte
solution through the encapsulated anode is indicated by arrows B.
For this embodiment, the anode sludge and particulates generated by
the dissolving anode plate are filtered and trapped by the
encapsulation membranes as the electrolyte solution passes through
the membrane.
[0118] FIG. 16 is a schematic diagram of an electrolyte solution
system 220. The electrolyte solution system 220 provides the
electrolyte solution to the electroplating process cells for the
electroplating process. The electrolyte solution system 220
generally comprises a main electrolyte solution tank 602, a dosing
module 603, a filtration module 605, a chemical analyzer module
616, and an electrolyte solution waste disposal system 622
connected to the analyzing module 616 by an electrolyte solution
waste drain 620. One or more controllers control the composition of
the electrolyte solution in the main tank 602 and the operation of
the electrolyte solution system 220. Preferably, the controllers
are independently operable but integrated with the controller 222
of the ECP system 200.
[0119] The main electrolyte solution tank 602 provides a reservoir
for electrolyte solution and includes an electrolyte solution
supply line 612 that is connected to each of the electroplating
process cells through one or more fluid pumps 608 and valves 607. A
heat exchanger 624 or a heater/chiller disposed in thermal
connection with the main tank 602 controls the temperature of the
electrolyte solution stored in the main tank 602. The heat
exchanger 624 is connected to and operated by the controller
610.
[0120] The dosing module 603 is connected to the main tank 602 by a
supply line and includes a plurality of source tanks 606, or feed
bottles, a plurality of valves 609, and a controller 611. The
source tanks 606 contain the chemicals needed for composing the
electrolyte solution and typically include a de-ionized water
source tank and copper sulfate (CuSO.sub.4) source tank for
composing the electrolyte solution. Other source tanks 606 may
contain hydrogen sulfate (H.sub.2SO.sub.4), hydrogen chloride (HCl)
and various additives such as glycol. Each source tank is
preferably color coded and fitted with a unique mating outlet
connector adapted to connect to a matching inlet connector in the
dosing module. By color coding the source tanks and fitting the
source tanks with unique connectors, errors caused by human
operators when exchanging or replacing the source tanks are
significantly reduced.
[0121] The de-ionized water source tank preferably also provides
de-ionized water to the system for cleaning the system during
maintenance. The valves 609 associated with each source tank 606
regulate the flow of chemicals to the main tank 602 and may be any
of numerous commercially available valves such as butterfly valves,
throttle valves and the like. Activation of the valves 609 is
accomplished by the controller 611 which is preferably connected to
the controller 222 to receive signals therefrom.
[0122] The electrolyte solution filtration module 605 includes a
plurality of filter tanks 604. An electrolyte solution return line
614 is connected between each of the process cells and one or more
filter tanks 604. The filter tanks 604 remove the undesired
contents in the used electrolyte solution before returning the
electrolyte solution to the main tank 602 for re-use. The main tank
602 is also connected to the filter tanks 604 to facilitate
re-circulation and filtration of the electrolyte solution in the
main tank 602. By re-circulating the electrolyte solution from the
main tank 602 through the filter tanks 604, the undesired contents
in the electrolyte solution are continuously removed by the filter
tanks 604 to maintain a consistent level of purity. Additionally,
re-circulating the electrolyte solution between the main tank 602
and the filtration module 605 allows the various chemicals in the
electrolyte solution to be thoroughly mixed.
[0123] The electrolyte solution system 220 also includes a chemical
analyzer module 616 that provides real-time chemical analysis of
the chemical composition of the electrolyte solution. The analyzer
module 616 is fluidly coupled to the main tank 602 by a sample line
613 and to the waste disposal system 622 by an outlet line 621. The
analyzer module 616 generally comprises at least one analyzer and a
controller to operate the analyzer. The number of analyzers
required for a particular processing tool depends on the
composition of the electrolyte solution. For example, while a first
analyzer may be used to monitor the concentrations of organic
substances, a second analyzer is needed for inorganic chemicals. In
the specific embodiment shown in FIG. 16 the chemical analyzer
module 616 comprises an auto titration analyzer 615 and a cyclic
voltametric stripper (CVS) 617. Both analyzers are commercially
available from various suppliers. An auto titration analyzer that
may be used to advantage is available from Parker Systems and a
cyclic voltametric stripper is available from ECI. The auto
titration analyzer 615 determines the concentrations of inorganic
substances such as copper chloride and acid. The CVS 617 determines
the concentrations of organic substances such as the various
additives which may be used in the electrolyte solution and
by-products resulting from the processing which are returned to the
main tank 602 from the process cells.
[0124] The analyzer module shown FIG. 16 is merely illustrative. In
another embodiment each analyzer may be coupled to the main
electrolyte solution tank by a separate supply line and be operated
by separate controllers. Persons skilled in the art will recognize
other embodiments.
[0125] In operation, a sample of electrolyte solution is flowed to
the analyzer module 616 via the sample line 613. Although the
sample may be taken periodically, preferably a continuous flow of
electrolyte solution is maintained to the analyzer module 616. A
portion of the sample is delivered to the auto titration analyzer
615 and a portion is delivered to the CVS 617 for the appropriate
analysis. The controller 619 initiates command signals to operate
the analyzers 615, 617 in order to generate data. The information
from the chemical analyzers 615, 617 is then communicated to the
controller 222. The controller 222 processes the information and
transmits signals which include user-defined chemical dosage
parameters to the dosing controller 611. The received information
is used to provide real-time adjustments to the source chemical
replenishment rates by operating one or more of the valves 609
thereby maintaining a desired, and preferably constant, chemical
composition of the electrolyte solution throughout the
electroplating process. The waste electrolyte solution from the
analyzer module is then flowed to the waste disposal system 622 via
the outlet line 621.
[0126] Although one embodiment utilizes real-time monitoring and
adjustments of the electrolyte solution, various alternatives may
be employed. For example, the dosing module 603 may be controlled
manually by an operator observing the output values provided by the
chemical analyzer module 616. Preferably, the system software
allows for both an automatic real-time adjustment mode as well as
an operator (manual) mode. Further, although multiple controllers
are shown in FIG. 16, a single controller may be used to operate
various components of the system such as the chemical analyzer
module 616, the dosing module 603, and the heat exchanger 624.
Other embodiments will be apparent to those skilled in the art.
[0127] The electrolyte solution system 220 also includes an
electrolyte solution waste drain 620 connected to an electrolyte
solution waste disposal system 622 for safe disposal of used
electrolyte solutions, chemicals and other fluids used in the ECP
system. Preferably, the electroplating cells include a direct line
connection to the electrolyte solution waste drain 620 or the
electrolyte solution waste disposal system 622 to drain the
electroplating cells without returning the electrolyte solution
through the electrolyte solution system 220. The electrolyte
solution system 220 preferably also includes a bleed off connection
to bleed off excess electrolyte solution to the electrolyte
solution waste drain 620.
[0128] Preferably, the electrolyte solution system 220 also
includes one or more degasser modules 630 adapted to remove
undesirable gases from the electrolyte solution. The degasser
module generally comprises a membrane that separates gases from the
fluid passing through the degasser module and a vacuum system for
removing the released gases. The degasser modules 630 are
preferably placed in line on the electrolyte solution supply line
612 adjacent to the process cells 240. The degasser modules 630 are
preferably positioned as close as possible to the process cells 240
so that most of the gases from the electrolyte solution system are
removed by the degasser modules before the electrolyte solution
enters the process cells. Preferably, each degasser module 630
includes two outlets to supply degassed electrolyte solution to the
two process cells 240 of each processing station 218.
Alternatively, a degasser module 630 is provided for each process
cell. The degasser modules can be placed at many other alternative
positions. For example, the degasser module can be placed at other
positions in the electrolyte solution system, such as along with
the filter section or in a closed-loop system with the main tank or
with the process cell. As another example, one degasser module is
placed in line with the electrolyte solution supply line 612 to
provide degassed electrolyte solution to all of the process cells
240 of the electrochemical plating system. Additionally, a separate
degasser module is positioned in-line or in a closed-loop with the
de-ionized water supply line and is dedicated for removing oxygen
from the de-ionized water source. Because de-ionized water is used
to rinse the processed substrates, free oxygen gases are preferable
removed from the de-ionized water before reaching the SRD modules
so that the electroplated copper is less likely to become oxidized
by the rinsing process. Degasser modules are well known in the art
and commercial embodiments are generally available and adaptable
for use in a variety of applications. A commercially available
degasser module is available from Millipore Corporation, located in
Bedford, Mass.
[0129] One embodiment of the degasser module 630, as shown in FIG.
26a, includes a hydrophobic membrane 632 having a fluid, i.e.,
electrolyte solution, passage 634 on one side of the membrane 632
and a vacuum system 636 disposed on the opposite side of the
membrane. The enclosure 638 of the degasser module includes an
inlet 640 and one or more outlets 642. As the electrolyte solution
passes through the degasser module 630, the gases and other
micro-bubbles in the electrolyte solution are separated from the
electrolyte solution through the hydrophobic membrane and removed
by the vacuum system. Another embodiment of the degasser module
630', as shown in FIG. 26b, includes a tube of hydrophobic membrane
632' and a vacuum system 636 disposed around the tube of
hydrophobic membrane 632'. The electrolyte solution is introduced
inside the tube of hydrophobic membrane, and as the electrolyte
solution passes through the fluid passage 634 in the tube, gases
and other micro-bubbles in the electrolyte solution are separated
from the electrolyte solution through the tube of hydrophobic
membrane 632' and removed by the vacuum system 636 surrounding the
tube. More complex designs of degasser modules are contemplated,
including designs having serpentine paths of the electrolyte
solution across the membrane and other multi-sectioned designs of
degasser modules.
[0130] Although not shown in FIG. 16, the electrolyte solution
system 220 may include a number of other components. For example,
the electrolyte solution system 220 preferably also includes one or
more additional tanks for storage of chemicals for a substrate
cleaning system, such as the SRD station. Double-contained piping
for hazardous material connections may also be employed to provide
safe transport of the chemicals throughout the system. Optionally,
the electrolyte solution system 220 includes connections to
additional or external electrolyte solution processing system to
provide additional electrolyte solution supplies to the ECP
system.
[0131] FIG. 17 is a cross sectional view of the RTA chamber. The
RTA chamber 211 is preferably connected to the loading station 210,
and substrates are transferred into and out of the RTA chamber 211
by the loading station transfer robot 228. The ECP system, as shown
in FIGS. 2 and 3, preferably comprises two RTA chambers 211
disposed on opposing sides of the loading station 210,
corresponding to the symmetric design of the loading station 210.
RTA process chambers are generally well known in the art, and RTA
chambers are typically utilized in substrate processing systems to
enhance the properties of the deposited materials. The ECP system
200 contemplates utilizing a variety of RTA chamber designs,
including hot plate designs and heat lamp designs, to enhance the
electroplating results. One particular suitable RTA chamber is the
WxZ chamber available from Applied materials, Inc., located in
Santa Clara, Calif. Although a hot plate RTA chamber is described,
other RTA chambers could be used as well.
[0132] The RTA chamber 211 generally comprises an enclosure 902, a
heater plate 904, a heater 907 and a plurality of substrate holder
pins 906. The enclosure 902 includes a base 908, a sidewall 910 and
a top 912. Preferably, a cold plate 913 is disposed below the top
912 of the enclosure. Alternatively, the cold plate is integrally
formed as part of the top 912 of the enclosure. Preferably, a
reflector insulator dish 914 is disposed inside the enclosure 902
on the base 908. The reflector insulator dish 914 is typically made
from a material such as quartz, alumina, or other material that can
withstand high temperatures, i.e., greater than about 500.degree.
C., and act as a thermal insulator between the heater 907 and the
enclosure 902. The dish 914 may also be coated with a reflective
material, such as gold, to direct heat back to the heater plate
906.
[0133] The heater plate 904 preferably has a large mass compared to
the substrate being processed in the system and is preferably
fabricated from a material such as silicon carbide, quartz, or
other materials that do not react with any ambient gases in the RTA
chamber 211 or with the substrate material. The heater 907
typically comprises a resistive heating element or a
conductive/radiant heat source and is disposed between the heated
plate 906 and the reflector insulator dish 914. The heater 907 is
connected to a power source 916 which supplies the energy needed to
heat the heater 907. Preferably, a thermocouple 920 is disposed in
a conduit 922, disposed through the base 908 and dish 914, and
extends into the heater plate 904. The thermocouple 920 is
connected to the controller 222 and supplies temperature
measurements to the controller. The controller then increases or
decreases the heat supplied by the heater 907 according to the
temperature measurements and the desired anneal temperature.
[0134] The enclosure 902 preferably includes a cooling member 918
disposed outside of the enclosure 902 in thermal contact with the
sidewall 910 to cool the enclosure 902. Alternatively, one or more
cooling channels, not shown, are formed within the sidewall 910 to
control the temperature of the enclosure 902. The cold plate 913
disposed on the inside surface of the top 912 cools a substrate
that is positioned in close proximity to the cold plate 913.
[0135] The RTA chamber 211 includes a slit valve 922 disposed on
the sidewall 910 of the enclosure 902 for facilitating transfers of
substrates into and out of the RTA chamber. The slit valve 922
selectively seals an opening 924 on the sidewall 910 of the
enclosure that communicates with the loading station 210. The
loading station transfer robot 228, see FIG. 2, transfers
substrates into and out of the RTA chamber through the opening
924.
[0136] The substrate holder pins 906 preferably comprise distally
tapered members constructed from quartz, aluminum oxide, silicon
carbide, or other high temperature resistant materials. Each
substrate holder pin 906 is disposed within a tubular conduit 926,
preferably made of a heat and oxidation resistant material, that
extends through the heater plate 904. The substrate holder pins 906
are connected to a lift plate 928 for moving the substrate holder
pins 906 in a uniform manner. The lift plate 928 is attached to an
to an actuator 930, such as a stepper motor, through a lift shaft
932 that moves the lift plate 928 to facilitate positioning of a
substrate at various vertical positions within the RTA chamber. The
lift shaft 932 extends through the base 908 of the enclosure 902
and is sealed by a sealing flange 934 disposed around the
shaft.
[0137] To transfer a substrate into the RTA chamber 211, the slit
valve 922 is opened, and the loading station transfer robot 228
extends its robot blade having a substrate positioned thereon
through the opening 924 into the RTA chamber. The robot blade of
the loading station transfer robot 228 positions the substrate in
the RTA chamber above the heater plate 904, and the substrate
holder pins 906 are extended upwards to lift the substrate above
the robot blade. The robot blade then retracts out of the RTA
chamber, and the slit valve 922 closes the opening. The substrate
holder pins 906 are then retracted to lower the substrate to a
desired distance from the heater plate 904. Optionally, the
substrate holder pins 906 may retract fully to place the substrate
in direct contact with the heater plate.
[0138] Preferably, a gas inlet 936 is disposed through the sidewall
910 of the enclosure 902 to allow selected gas flow into the RTA
chamber 211 during the anneal treatment process. The gas inlet 936
is connected to a gas source 938 through a valve 940 for
controlling the flow of the gas into the RTA chamber 211. A gas
outlet 942 is preferably disposed at a lower portion of the
sidewall 910 of the enclosure 902 to exhaust the gases in the RTA
chamber and is preferably connected to a relief/check valve 944 to
prevent backstreaming of atmosphere from outside of the chamber.
Optionally, the gas outlet 942 is connected to a vacuum pump, not
shown, to exhaust the RTA chamber to a desired vacuum level during
an anneal treatment.
[0139] A substrate is annealed in the RTA chamber 211 after the
substrate has been electroplated in the electroplating cell and
cleaned in the SRD station. Preferably, the RTA chamber 211 is
maintained at about atmospheric pressure, and the oxygen content
inside the RTA chamber 211 is controlled to less than about 100 ppm
during the anneal treatment process. Preferably, the ambient
environment inside the RTA chamber 211 comprises nitrogen (N.sub.2)
or a combination of nitrogen (N.sub.2) and less than about 4%
hydrogen (H.sub.2), and the ambient gas flow into the RTA chamber
211 is maintained at greater than 20 liters/min to control the
oxygen content to less than 100 ppm. The electroplated substrate is
preferably annealed at a temperature between about 200.degree. C.
and about 450.degree. C. for between about 30 seconds and 30
minutes, and more preferably, between about 250.degree. C. and
about 400.degree. C. for between about 1 minute and 5 minutes. RTA
processing typically requires a temperature increase of at least
50.degree. C. per second. To provide the required rate of
temperature increase for the substrate during the anneal treatment,
the heater plate is preferably maintained at between about
350.degree. C. and about 450.degree. C., and the substrate is
preferably positioned at between about 0 mm, i.e., contacting the
heater plate, and about 20 mm from the heater plate for the
duration of the anneal treatment process. Preferably, a controller
222 controls the operation of the RTA chamber 211, including
maintaining the desired ambient environment in the RTA chamber and
the temperature of the heater plate.
[0140] After the anneal treatment process is completed, the
substrate holder pins 906 lift the substrate to a position for
transfer out of the RTA chamber 211. The slit valve 922 opens, and
the robot blade of the loading station transfer robot 228 is
extended into the RTA chamber and positioned below the substrate.
The substrate holder pins 906 retract to lower the substrate onto
the robot blade, and the robot blade then retracts out of the RTA
chamber. The loading station transfer robot 228 then transfers the
processed substrate into the cassette 232 for removal out of the
electroplating processing system, as shown in the embodiment of
FIGS. 2 and 3.
[0141] Referring back to FIG. 2, the ECP system 200 includes a
controller 222 that controls the functions of each component of the
platform. Preferably, the controller 222 is mounted above the
mainframe 214 and comprises a programmable microprocessor. The
programmable microprocessor is typically programmed using a
software designed specifically for controlling all components of
the ECP system 200. The controller 222 also provides electrical
power to the components of the system and includes a control panel
223 that allows an operator to monitor and operate the ECP system
200. The control panel 223, as shown in FIG. 2, is a stand-alone
module that is connected to the controller 222 through a cable and
provides easy access to an operator. Generally, the controller 222
coordinates the operations of the loading station 210, the RTA
chamber 211, the SRD station 212, the mainframe 214 and the
processing stations 218. Additionally, the controller 222
coordinates with the controller of the electrolyte solution system
220 to provide the electrolyte solution for the electroplating
process.
[0142] The following is a description of a typical substrate
electroplating process sequence through the ECP system 200 as shown
in FIG. 2. A substrate cassette containing a plurality of
substrates is loaded into the substrate cassette receiving areas
224 in the loading station 210 of the ECP system 200. A loading
station transfer robot 228 picks up a substrate from a substrate
slot in the substrate cassette and places the substrate in the
substrate orientor 230. The substrate orientor 230 determines and
orients the substrate to a desired orientation for processing
through the system. The loading station transfer robot 228 then
transfers the oriented substrate from the substrate orientor 230
and positions the substrate in one of the substrate slots in the
substrate pass-through cassette 238 in the SRD station 212. The
mainframe transfer robot 242 picks up the substrate from the
substrate pass-through cassette 238 and positions the substrate for
transfer by the flipper robot 248. The flipper robot 248 rotates
its robot blade below the substrate and picks up substrate from
mainframe transfer robot blade. The vacuum suction gripper on the
flipper robot blade secures the substrate on the flipper robot
blade, and the flipper robot flips the substrate from a face up
position to a face down position. The flipper robot 248 rotates and
positions the substrate face down in the substrate holder assembly
450. The substrate is positioned below the substrate holder
assembly 450 but above the electric contact element 466. The
flipper robot 248 then releases the substrate to position the
substrate into the electric contact element 466. The substrate
holder element 464 moves toward the substrate and the vacuum chuck
secures the substrate on the substrate holder element 464. The
bladder assembly 470 on the substrate holder assembly 450 exerts
pressure against the substrate backside to ensure electric contact
between the substrate plating surface and the electric contact
element 466.
[0143] The head assembly frame 452 is lowered to a processing
position above the process cell 420. At this position the substrate
is below the upper plane of the weir 478 and contacts the
electrolyte solution contained in the process cell 420. The power
supply is activated to supply electric power, i.e., voltage and
current, to the cathode and the anode to enable the electroplating
process. The electrolyte solution is typically continually pumped
into the electrolyte cell during the electroplating process. The
electric power supplied to the cathode and the anode and the flow
of the electrolyte solution are controlled by the controller 222 to
achieve the desired electroplating results. Preferably, the head
assembly is rotated as the head assembly is lowered and also during
the electroplating process.
[0144] After the electroplating process is completed, the head
assembly 410 raises the substrate holder assembly 450 and removes
the substrate from the electrolyte solution. Preferably, the head
assembly is rotated for a duration that enhances removal of
residual electrolyte solution from the substrate holder assembly.
The vacuum chuck and the bladder assembly of the substrate holder
assembly then release the substrate from the substrate holder
element 464, and the substrate holder element 464 is raised to
allow the flipper robot blade to pick up the processed substrate
from the electric contact element. The flipper robot rotates the
flipper robot blade above the backside of the processed substrate
in the electric contact element and picks up the substrate using
the vacuum suction gripper on the flipper robot blade. The flipper
robot rotates the flipper robot blade with the substrate out of the
substrate holder assembly, flips the substrate from a face-down
position to a face-up position, and positions the substrate on the
mainframe transfer robot blade. The mainframe transfer robot then
transfers and positions the processed substrate above the SRD
module 236. The SRD substrate support lifts the substrate, and the
mainframe transfer robot blade retracts away from the SRD module
236. The substrate is cleaned in the SRD module using de-ionized
water or a combination of de-ionized water and a cleaning fluid as
described in detail above. The substrate is then positioned for
transfer out of the SRD module. The loading station transfer robot
228 picks up the substrate from the SRD module 236 and transfers
the processed substrate into the RTA chamber 211 for an anneal
treatment process to enhance the properties of the deposited
materials. The annealed substrate is then transferred out of the
RTA chamber 211 by the loading station robot 228 and placed back
into the substrate cassette for removal from the ECP system. The
above-described sequence can be carried out for a plurality of
substrates substantially simultaneously in the ECP system 200. The
ECP system can be adapted to provide multi-stack substrate
processing.
[0145] 2. Substrate Holder System
[0146] A substrate holder system 14 is described that is capable of
immersing the substrate into an electrolyte solution in an
electrolyte cell. The substrate holder system 14 is capable of
tilting a substrate holder assembly containing a substrate relative
to the level line of the electrolyte solution, the level line being
substantially horizontal. Certain embodiments of substrate holder
systems are capable of rotating the substrate during the immersion
of the substrate into the electrolyte solution. The titling of the
substrate during immersion limits air bubbles or air bridges from
forming within the electrolyte solution under the substrate holder
and/or the substrate. This section describes the structure and the
operation of one embodiment of the substrate holder system.
[0147] FIG. 6, as described above, provides one embodiment in which
a head assembly 410 is capable of translating a substrate holder
assembly 450 in the x and z directions. FIG. 25 is a partial cross
sectional view of another embodiment of a substrate holder system
14 that is capable of translating a substrate holder assembly 2450
in the horizontal and vertical directions. The embodiment of a
substrate holder system 14 shown in FIG. 25 provides for tilting of
the substrate holder assembly at an angle .alpha. from horizontal
in addition to the translation of the substrate holder assembly in
a X-direction and the Z-direction. This embodiment provides for
rotation of the substrate during immersion of the substrate into
the electrolyte solution where the substrate is held by the
substrate holder assembly. The substrate holder system 14 includes
a rotatable head assembly 2410 and a head assembly frame 2452. The
head assembly frame 2452 includes a mounting post 2454, a shaft
2453, a post cover 2455, a cantilever arm 2456, a cantilever arm
actuator 2457, and a pivot joint 2459. The mounting post 2454 is
mounted onto the body of the mainframe 214, and the post cover 2455
covers a top portion of the mounting post 2454.
[0148] Preferably, the mounting post 2454 provides rotational
movement, in a direction indicated by arrow A1, of the mounting
post to allow for rotation of the head assembly frame 2452 about a
substantially vertical axis which extends through the mounting
post. Such motion is generally provided to align the head assembly
2410 with the electrolyte cell.
[0149] One end of the cantilever arm 2456 is pivotally connected to
the shaft 2453 of the cantilever arm actuator 2457. The cantilever
arm actuator 2457 is, for example, a pneumatic cylinder, a
lead-screw actuator, a servo-motor, or other type actuator. The
cantilever arm 2456 is pivotally connected to the mounting slide
2460 at the pivot joint 2459. The cantilever arm actuator 2457 is
mounted to the mounting post 2454. The pivot joint 2459 is
rotatably mounted to the post cover 2455 so that the cantilever arm
2456 can pivot about the post cover at the pivot joint. Actuation
of the cantilever arm actuator 2457 provides pivotal movement, in a
direction indicated by arrow A2, of the cantilever arm 2456 about
the pivot joint 2459. Alternatively, a rotary motor may be provided
as a cantilever arm actuator 2457, wherein output of a rotary motor
is connected directly between the post cover 2455 and the pivot
joint 2459. The rotary motor output effects rotation of the
cantilever arm 2456 and the head assembly 2410 about the pivot
joint.
[0150] The rotatable head assembly 2410 is attached to a mounting
slide 2460 of the head assembly frame 2452, and the mounting slide
2460 is disposed at the distal end of the cantilever arm 2456.
Rotation of the rotatable head assembly 2410 about the pivot joint
2459 causes tilting of a substrate held within the substrate holder
assembly 2450 of the rotatable head assembly 2410 about the pivot
joint 2459 relative to horizontal. When the cantilever arm actuator
2457 is retracted, the cantilever arm 2456 raises the head assembly
2410 away from the process cell 420 as shown in FIG. 6. This
tilting of the rotatable head assembly 2410 effects tilting of the
substrate relative to horizontal. Such tilting of the substrate is
used during removal and/or replacement of the substrate holder
assembly from/to the electroplating process cell 240. When the
cantilever arm actuator 2457 is extended, the cantilever arm 2456
moves the head assembly 2410 toward the process cell 420 to angle
the substrate closer to horizontal. The substrate is preferably in
a substantially horizontal position during ECP.
[0151] The rotatable head assembly 2410 includes a rotating
actuator 2464 slidably connected to the mounting slide 2460. The
mounting slide 2460 guides the vertical motion of the rotatable
head assembly 2410. A head lift actuator 2458 is disposed on the
mounting slide 2460 to provide motive force for vertical
displacement of the head assembly 2410. The shaft 2468 of the head
lift actuator 2458 is inserted through a lift guide 2466 attached
to the body of the rotating actuator 2464. Preferably, the shaft
2468 is a lead-screw type shaft that moves the lift guide, in a
direction indicated by arrow A3, between various vertical
positions. This lifting of the rotatable head assembly 2410 can be
used to remove and/or replace the substrate holder assembly from
the electroplating process cell 240. Removing the substrate from
the process cell is necessary to position the substrate so that a
robot can remove the substrate from the rotatable head assembly
2410.
[0152] The rotating actuator 2464 is connected to the substrate
holder assembly 2450 through the shaft 2470 and rotates the
substrate holder assembly 2450 in a direction indicated by arrow
A4. The rotation of the substrate during the electroplating process
generally enhances the deposition results. Preferably, the head
assembly rotates the substrate about the vertical axis of the
substrate between about 0 RPM and about 200 RPM, and more
particularly between about 10 and about 40 RPM, during the
electroplating process. Rotation of the substrate at a higher
angular velocity may result in turbulence within the electrolyte
solution. The head assembly can also be rotated as the head
assembly is lowered to position the substrate in contact with the
electrolyte solution in the process cell as well as when the head
assembly is raised to remove the substrate from the electrolyte
solution in the process cell. The head assembly is preferably
rotated at a high speed, e.g., up to about 2,500 RPM, after the
head assembly is lifted from the process cell. Such rotation of the
substrate following the removal of the substrate from the
electrolyte solution enhances removal of residual electrolyte
solution on the substrate by the centrifugal force applied to the
liquid on the substrate.
[0153] FIG. 27 shows a cross sectional view of one embodiment of
rotatable head assembly 2410 that can be contained in the substrate
holder system 14 of the embodiment shown in FIG. 25 to provide for
the rotation of the substrate. The rotatable head assembly 2410
provides for lowering of the thrust plate 66 to position a
substrate in contact with the electric contact element 67. The
thrust plate can be raised to provide a space between the thrust
plate 66 and the electric contact element 67 to permit removal of
the substrate from, or insertion of the substrate into, the
rotatable head assembly 2410. The rotatable head assembly 2410
comprises a substrate holder assembly 2450, a rotating actuator
2464, a shaft shield 2763, a shaft 2470, an electric feed through
2767, an electric conductor 2771, and a pneumatic feed through
2773. The rotating actuator 2464 comprises a head rotation housing
2760 and a head rotation motor 2706. The head rotation motor 2706
comprises a coil segment 2775 and a magnetic rotary element 2776.
The hollow coil segment 2775 generates a magnetic field rotates the
magnetic rotary element 2776 about a vertical axis. The substrate
holder assembly 2450 comprises a fluid shield 2720, a contact
housing 2765 a thrust plate 66, an electric contact element 67, and
a spring assembly 2732.
[0154] The contact housing 2765 and the spring assembly 2732 are
generally annular, and these two elements interfit, and may provide
for a combined rotation that is transferred to the thrust plate 66
and the electric contact element 67. The spring assembly 2732
comprises an upper spring surface 2728, a spring bellow connector
2729, and a lower spring surface 2738. Seal element 2751 seals the
fluid passage between the upper spring surface 2728 and the thrust
plate 66. Seal element 2753 seals the fluid passage between the
lower spring surface 2738 and the contact housing 2765.
[0155] Electricity is supplied to the electric contact element 67
that contacts the seed layer on a substrate to provide a desired
voltage between the anode 16 and the seed layer on the substrate to
effect the electroplating. Electricity is supplied from the
controller 222 to the electric contact element 67 via the electric
feed through 2767, a conductor 2733, and the contact housing 2765.
The electric contact element 67 is in physical, and electrical,
contact with the seed layer on the substrate. The shaft 2470, the
contact housing 2765, the spring assembly 2732, the thrust plate
66, the electric contact element 67, the rotary mount 2799, and the
substrate 22 secured between the thrust plate 66 and the electric
contact element 67 all rotate as a unit about a longitudinal axis
of the head assembly 2410. The head rotation motor 2706 provides
the motive force to rotate the above elements about its vertical
axis.
[0156] A vacuum is controllably supplied to portions of the
rotatable head assembly 2410 by the pneumatic feed through 2773 to
control the position of the thrust plate relative to the electric
contact element 67. The pneumatic feed through 2773 that supplies
the vacuum comprises a controllable vacuum supply 2790, a sleeve
member 2792, a fluid conduit 2794, a circumferential groove 2795, a
fluid aperture 2796, and a fluid passage 2798. The sleeve member
2792 may be a distinct member, or a portion of the shaft as shown
in FIG. 27. The circumferential groove 2795 extends within the
sleeve member 2792 about the circumference of the shaft 2470. The
pneumatic feed through supplies a vacuum to a pressure reservoir
2740. The pressure reservoir is configured to maintain either
positive air pressure or vacuum, depending upon the configuration
of the head assembly 2410. The fluid aperture 2796 is in fluid
communication with the circumferential groove. The fluid aperture
2796 extends axially through the shaft 2470 from the
circumferential groove 2795 to the bottom of the shaft 2470. The
fluid passage 2798 extends through the contact housing 2765. The
fluid aperture 2796 at the bottom of the shaft is in fluid
communication with the fluid passage 2798. The inner surface of the
sleeve member 2792 has a small clearance, e.g. about 0.0002 inch,
with the outer surface of the shaft 2470 to allow relative rotation
between these two members.
[0157] A vacuum is applied from the vacuum supply 2790 via the
fluid conduit 2794 to the inner surface of the sleeve member 2792
and the circumferential groove 2795. The vacuum is applied from the
fluid aperture 2796 to the fluid passage 2798, and the pressure
reservoir 2740. Due to the tight clearance between the sleeve
member 2792 and the shaft 2470, a vacuum applied to the inner
surface of the sleeve member 2792 passes via the circumferential
groove 2795 to the fluid aperture 2796. The tight clearance limits
air entering between the sleeve member 2792 and the outer surface
of the shaft 2470. Therefore, the vacuum applied from the
controllable vacuum supply 2790 extends to the pressure reservoir.
A vacuum within the shaft 2470 passes through the fluid passage
2798 to a pressure reservoir 2740 formed between the spring
assembly 2732 and the contact housing 2765. The vacuum applied by
the controllable vacuum supply 2790 thereby controls the vacuum in
the pressure reservoir 2740.
[0158] The spring bellow connector 2729 combines aspects of a
spring and a bellows. The spring bias connector 2729 is attached
between the thrust plate 66 and the contact housing 2765. The
spring bellows connector 2729 limits fluid flow between the thrust
plate 66 and the electric contact element 67. The spring bellows
connector 2729 additionally exerts a spring force when axially
displaced, either compressed or extended, from its relaxed shape.
The bias of the spring bellow connector 2729 is used to position
the thrust plate 66 relative to the electric contact element 67.
Any suitable type of bellows or baffle member that has a spring
constant may be used as spring bellow connector 2729.
Alternatively, separate spring and bellows members may be used as
the spring bellow connector 2729. The upper spring surface 2728 is
annular shaped and is sealably connected to the thrust plate 66.
The lower spring surface 2738 is sealably connected to the contact
housing 2765. A pressure reservoir 2740 is defined in the annulus
between the contact housing 2765 and the spring assembly 2732. In
one embodiment, the thrust plate is normally pressed against the
backside of the substrate by the spring tension exerted by the
spring bellow connector 2729. Application of the vacuum within the
pressure chamber 2740 raises spring bellows connector 2729, and
thereby also raises the thrust plate 66.
[0159] The thrust plate 66 is displaced to a raised position when a
robot, not shown, is loading or unloading a substrate 22 onto the
electric contact element 67. Following insertion by the robot, the
substrate 22 rests upon the contact element such that the periphery
of the plating surface of the substrate 22 rests upon the contact
element. The thrust plate 66 is then lowered firmly against the
upper surface of the substrate 22 to ensure a snug contact between
the plating surface of the substrate 22 and the electric contact
element 67. Electricity can be applied from the controller 222 to
the seed layer on the substrate 22.
[0160] The substrate holder assembly 2450 is configured to hold a
substrate 22 in a secured position such that the substrate can be
moved between the exchange, dry, and process positions. The thrust
plate 66 can also be biased downwardly to secure a substrate 22
against the electric contact element 67. The thrust plate 66 can be
biased upward to provide a space between the thrust plate 66 and
the electric contact element 67 through which a substrate can be
inserted by a robot device. In the embodiment shown in FIG. 27,
upward bias to the thrust plate is provided by a vacuum created
within pressure reservoir 2740 by the controllable vacuum supply
2790. The vacuum in the pressure reservoir 2740 causes the upper
spring surface 2728, the remainder of the spring assembly 2732, and
the attached thrust plate 66 to be displaced upwardly.
[0161] Reducing the vacuum from the controllable vacuum supply 2790
allows the spring bellow connector 2729 to return to its normal
tensioned position by which the upper spring surface 2728 biases
the attached thrust plate 66 into secure contact with a substrate
22 positioned on the electric contact element 67. This physical
biasing of the substrate against the electric contact element 67 is
sufficient to enhance the electric contact between the electric
contact element 67 and the seed layer on the substrate 22. The
electric contact element 67 extends about the periphery of the seed
layer on a substrate inserted in the substrate holder assembly, and
is electrically biased relative to the anode assembly 474 shown in
the embodiment of FIG. 6 to effect metal deposition on the seed
layer. The thrust plate 66, the electric contact element 67, the
spring bellow connector 2729, and a substrate inserted on the
electric contact element all rotate relative to the fluid shield
2720. The fluid shield 2720 remains fixed to the shaft shield 2763
and does not rotate.
[0162] The head rotation motor 2706 is mounted within, and at least
partially extends through, the inner circumference of the hollow
head rotation housing 2760 and is connected to the shaft 2470. The
hollow coil segment 2775 is mounted to, and remains substantially
stationary relative to, the inside of the hollow head rotation
housing 2760. The shaft 2470 includes a magnet portion 2777 that
can be rotated about a vertical axis. The magnet portion 2777 is
physically disposed within the hollow portion of the hollow coil
segment 2775. The hollow coil segment 2775 induces rotation in the
magnet portion 2777 and the connected shaft 2470. Bearings 2785 are
provided between shaft shield 2763 and the shaft 2470 to limit
lateral travel of the shaft 2470 during rotation about a vertical
axis. The output of the shaft 2470, at the lower end of the shaft,
provides rotary motion to certain portions of the substrate holder
assembly 2450 including a thrust plate 66 and a substrate 22 held
between the thrust plate and the electric contact element 67, as
described below. The head rotation motor 2706 may be of the type
that produces output rotation in the range from, for example, 0 RPM
to 2500 RPM under the influence of the controller 222.
[0163] The fluid shield 2720 is optional, and when used it may be
disposed about the periphery of, and preferably spaced from, the
substrate holder assembly 2450. The fluid shield contains
electrolyte solution or other matter that may be removed from the
substrate or substrate holder assembly by centrifugal rotation of
the substrate holder assembly 2450 on other adjacent equipment.
[0164] 3. Fluid Effects of Tilting a Substrate Upon Immersion
[0165] One technique that improves the uniformity of plating
involves limiting the formation of air bubbles or pockets that may
contact the seed layer on the substrate. The present system limits
air bubbles or air bridges being trapped between the electrolyte
solution and the substrate during the immersion of the substrate
into the electrolyte solution. Air bubbles or air bridges in the
electrolyte solution may cause pitting, tarnishing, deformations,
and non-uniformity of the deposited layer. If present for a
sufficient time, an air bubble or air bridge will limit the metal
ions in the electrolyte solution from depositing on the substrate,
thereby creating a void on the substrate.
[0166] One technique that minimizes the chance of air bubbles
getting trapped by the substrate and/or the substrate holder
assembly is to tilt the substrate/substrate holder assembly from
horizontal as the substrate is immersed into the electrolyte
solution. A very thin boundary layer of the electrolyte solution
will cover the substrate and the seed layer formed thereon. Air
bubbles that are proximate the substrate will flow upwardly along
the boundary layer as the substrate is tilted at an angle from
horizontal and disposed in the solution. The tendency of the air
bubbles to flow along the boundary layer without contacting any
part of the substrate increases as the angle of tilt increases.
[0167] FIGS. 34 and 35 shows a progression of steps as a substrate,
held by a substrate holder assembly, is immersed into the
electrolyte solution at an angle .alpha. from horizontal. These
figures illustrate how features are more completely filled by
electrolyte solution, and the air bubbles within the features are
more completely removed from the features. The substrate 22 is
lowered into the electrolyte solution as shown in FIG. 25 by the
downward displacement of the lift guide 2466 along the mounting
slide 2460. To explain the mechanism by which the substrate 22 is
immersed into the electrolyte solution, the fluid-level of the
electrolyte solution is considered to be moving upward relative to
the substrate in a direction indicated by arrow 3406 from the level
3402 shown in FIG. 34 to the level 3402' shown in FIG. 35. An
exemplary feature 3410, such as a via, a trench, an electric
contact, etc. is formed in the surface of the substrate 22. The
width of such features in modern semiconductor processing is
typically measured in the microns.
[0168] The "flow" of the electrolyte solution across the substrate
22, when the tilt angle .alpha. of the substrate is greater than 0
degrees, is enhanced by the travel of the meniscus 3004 across the
seed layer on the substrate 22. The meniscus 3004 is the convex
upper surface of the liquid that contacts the surface of an
adjacent solid material. The meniscus is caused by surface tension.
For instance, a meniscus is formed in a glass containing water as
the water surface touches the glass in which it is contained. The
meniscus 3004 enhances the displacement of air bubbles from within
the features as the substrate is immersed in the electrolyte
solution. Increasing the tilt angle a will also allow the meniscus
to be more effective in displacing air bubbles and air pockets from
within feature 3410 on the substrate by utilizing the displacing
action of the meniscus provided by surface tension. The surface
tension associated with the meniscus acts to draw the electrolyte
solution along the field, and therefore displace air bubbles or
pockets contained on a field surface 3410 of the substrate when the
tilt angle .alpha. of the substrate is angled from horizontal as
the electrolyte solution rises from level 3402 as indicated by
arrow 34.
[0169] As the level of the electrolyte solution rises from level
3402 in FIG. 34 to a level 3402' shown in FIG. 35, the meniscus
3004 rises above the lower level 3412 of the feature. Surface
tension is an important mechanism that is used to fill feature 3410
with electrolyte solution. Without surface tension, as the level of
the electrolyte solution rises to a highest opening point 3416 of
feature 3410, the level of the electrolyte solution would
horizontally extend as shown by dotted line 3418. Without surface
tension, an air bubble would be formed in the space above the
dotted line 3418. In actuality, surface tension draws electrolyte
solution into the features as the meniscus moves upwardly past the
opening of the feature. The molecular fluid attraction associated
with surface tension "draws" the electrolyte solution into, and
completely fills, the feature to the upper limits indicated by
3402". In so doing, the electrolyte meniscus displaces any air that
would otherwise be trapped within the feature. The electrolyte
solution is drawn into the feature more quickly as the tilt angle
.alpha., ranging from 0 to 90 degrees, increases. The reason that
air is displaced more quickly by the electrolyte solution is that
the volume of trapped air, i.e. above line 3418, decreases as the
tilt angle .alpha. is increased, and most particularly as .alpha.
exceeds 45 degrees.
[0170] More time is required for the electrolyte solution to
displace the air bubbles contained in the features if the substrate
is immersed at a lesser tilt angle .alpha. than a greater tilt
angle, e.g., less than 45 degrees from horizontal compared to
greater than 45 degrees. For example, the electric contact element
of the substrate holder assembly and the substrate together form an
inverted concave area. The area of trapped air in this
inverted-concave area decreases as the angle of the substrate
increases. As the substrate in the substrate holder assembly
approaches, but is not equal to, horizontal, the substrate holder
assembly has to be angularly tilted by the substrate holder system
14 at a slower angular rate to effectively remove the air bridges
and air bubbles. This slower angular tilt rate is necessary to
adequately fill the feature with electrolyte solution. The actual
angular tilt rate of the substrate holder system is a function of
such considerations as the chemical components of the electrolyte
solution, the surface of the substrate, the configuration and
surface of the substrate and the substrate holder assembly.
[0171] The substrate holder assembly 2450 functions to position the
substrate seed layer relative to the electrolyte solution during
start-up, processing, and removal of the substrate. The operation
of the substrate holder system 14, including the application of a
vacuum to pressure reservoir 2740 to extend or retract the thrust
plate 66, the operation and angular velocity of the motor 2706, the
position of the pivot joint 2459 that controls the tilt of the
substrate, and other such mechanical displacements are controlled
by the controller 222. One embodiment of the progression of the
substrate holder system 14 during the metal deposition process is
shown in FIGS. 28A to 28H. One embodiment of method 2900 shown in
FIG. 29 is performed by the controller 222 to perform the
progression shown in FIGS. 28A to 28H.
[0172] The progression of the substrate holder system 14 shown in
FIGS. 28A to 28H is to be read in conjunction with the method 2900
shown in FIG. 29. During the progression of FIGS. 28A to 28H,
generally a substrate is inserted into the substrate holder
assembly, the substrate is immersed into the electrolyte solution,
the substrate is processed, the substrate is removed from the
electrolyte solution, and the substrate is removed from the
substrate holder assembly.
[0173] FIG. 28A, and block 2902 in FIG. 29, show the substrate
holder system 14 being positioned in an exchange position in which
the thrust plate 66 of the substrate holder assembly is retracted
into a raised position by the creation of a vacuum in the pressure
reservoir 2740 shown in FIG. 27. The substrate holder system 14 is
positioned in its exchange position to allow a robot blade, not
shown, that is holding a substrate 22 to insert a substrate between
the electric contact element 67 and the thrust plate 66.
[0174] As shown in FIG. 28B, and block 2904 in FIG. 29, a robot
displaces the substrate 22 between the thrust plate 66 and the
electric contact element 67 as the substrate 22 is loaded on the
contact element. The thrust plate 66 is then lowered to exert a
bias against the backside to secure the substrate 22, and provide a
sufficient electric contact between the plating surface and the
contact element. The thrust plate is lowered with such force to
secure, but not damage, the substrate 22. The lowering of the
thrust plate is accomplished by decreasing the vacuum applied
within the pressure reservoir 2740 shown in FIG. 27 to allow the
spring bellow connector 2729 to return downwardly to its pre-set
position. During the remaining substrate 22 processing, the thrust
plate remains in the lowered biased position until the thrust plate
in the substrate holder assembly is moved to the exchange position
as indicated by FIG. 28G. In those embodiments of substrate holder
system 14 that the substrate can be rotated, the substrate holder
system starts angular rotation of the substrate in FIG. 28B about a
vertical axis passing through the substrate, and continues through
FIG. 28G. The velocity of angular rotation may vary through the
progression depending upon whether the substrate is being immersed
in the electrolyte solution, the substrate is being processed, or
the substrate is being removed from the electrolyte solution, or
the substrate is being rotated for drying of the substrate by
centrifugal force.
[0175] FIG. 28C, and block 2906 of FIG. 29, shows the substrate
holder assembly 2450 being moved to a dry position as a result of
actuation of the head lift portion 2708 in which the lift guide
2466 is translated downward relative to the mounting slide 2460. In
the drying position, the substrate holder assembly supports the
substrate 22 above the electrolyte solution contained in the
electrolyte solution cell 12. The substrate 22 is positioned in the
drying position prior to its immersion into the electrolyte
solution, and after the substrate has been removed from the
electrolyte solution. Positioning the substrate 22 in the drying
position is part of a routine such that the substrate 22 can be
quickly immersed into the electrolyte solution.
[0176] FIG. 28D, and block 2908 in FIG. 29, shows the substrate
holder assembly 2450, the rotating actuator 2464, and the head lift
portion 2708 all being tilted as a unit by the head assembly frame
about the pivot joint 2459. A cantilever arm actuator 2457 that can
controllably actuate the shaft 2453 and the connected cantilever
arm 2456 to effect tilting of the head assembly frame 2410, that
holds the substrate, about the pivot joint 2459. The tilting of the
seed layer on the substrate is provided to enhance the immersion of
the seed layer into the electrolyte solution, as shown in FIG.
28E.
[0177] FIG. 28E, and block 2910 of FIG. 29, shows the immersion of
the substrate 22, contained in the head portion 2450, into the
electrolyte solution from the dry position. The shaft 2468 is
rotated during the immersion of the substrate. During this shaft
rotation, the lift guide 2466 is translated downwardly along the
mounting slide 2460 to cause downward motion of the head assembly
2410. Concurrently, the head assembly 2410 is rotated downwardly
about the pivot joint 2459 to cause tilting of the substrate. The
tilting of the substrate 22 so that the substrate is angled from
horizontal minimizes the occurrences of air bubbles and air bridges
trapped underneath the substrate/substrate holder within the
electrolyte solution. This limitation of air bubbles results from
the enhanced action of the meniscus 3004 in limiting the number of
air bubbles trapped as substrate 22 is lowered into the electrolyte
solution, and also lets the air bubbles escape more easily across
the tilted substrate face. In addition, spinning of the substrate
during immersion minimizes the chance that an air bubble will
become attached to an location on the seed layer.
[0178] FIG. 30 shows how the tilt angle .alpha. changes as a
substrate is being immersed into an electrolyte solution by the
substrate holder system 14 between two positions 22' and 22". The
electric contact element 67 in FIGS. 30, 31, 32 represent a portion
of electric contact element that actually contacts the substrate.
Other portions of the electric contact element, similar to as shown
in FIG. 27, are not shown for simplicity of display. Substrate 22'
is angled at an angle .alpha..sub.1 while the substrate 22" is
angled at angle .alpha..sub.2 from horizontal. The substrate also
moves to the left, as the substrate is more completely immersed in
the electrolyte solution, between the positions shown as 22' and
22" in the embodiment in FIG. 31, as also reflected in the
positions shown in FIGS. 28E and 28F. This lateral motion results
from the lateral displacement of the substrate holder assembly 2450
as the rotatably head assembly 2410, shown in the embodiment of
FIG. 25, pivots about the pivot joint 2459. Angle .alpha..sub.1 is
greater than the angle .alpha..sub.2, indicating that the substrate
holder system rotates the substrate to an angle closer to
horizontal as the substrate is immersed deeper into the electrolyte
solution. As the substrate 22 is lowered into the electrolyte
solution, meniscus 3004 formed between the electrolyte solution and
the substrate flows along the substrate seed layer.
[0179] FIG. 31 shows the vertical height H of the electric contact
element 22. The greater the height H for a given combination of
substrate, electric contact element, and electrolyte solution,
generally results in a larger the volume of air being trapped under
a given-substrate if the substrate is immersed in a horizontal or
tilted attitude. Therefore, it is desired to limit the height H to
reduce the amount and volume of air bubbles trapped in the
electrolyte solution under the substrate during immersion.
[0180] It is possible to form air bubbles and air bridges between
the substrate and the electric contact element 67 upon immersion in
the electrolyte solution. The bubble 3002 in FIG. 31 is created
when the substrate 22 is immersed within the electrolyte solution
too rapidly. Alternatively, when the substrate 22 is immersed
within the electrolyte solution at too slow a rate, as illustrated
in FIG. 32, then air bridge 3102 forms between the substrate 22 and
the electric contact element 67. When substrate 22 is immersed in
the electrolyte solution at the suitable rate, neither a bubble
3002 nor an air bridge 3102 is formed between the substrate 22 and
the electric contact element 67 within the electrolyte
solution.
[0181] Graph 33 plots an ordinate 3302 d.alpha./dt that represent
the rate that the substrate tilt angle .alpha. is changed as a
function of time after initial immersion of the substrate on the
abscissa 3304. As the substrate approaches immersion, the tilt
angle .alpha. of the substrate is typically 45 degrees, or on some
embodiments, approaches 90 degrees. The substrate tilt angle
.alpha. is controlled by the amount that cantilever arm actuator
2457 pivots head assembly 2410 about pivot joint 2459. The value of
d.alpha./dt represented by 3306 shows the rapid rate at which the
substrate tilt angle .alpha. changes toward the horizontal as the
periphery of the substrate is initially immersed into the
electrolyte solution. As immersion continues, the rate of tilt
angle .alpha. change is reduced as represented by the value of
3308. Since the substrate is closer to horizontal, the substrate is
to be immersed into the electrolyte solution at a slower rate of
d.alpha./dt to enable the electrolyte solution to displace the air
from the features. During this period, the meniscus 3004, i.e.
where the electrolyte solution contacts the substrate, slowly
sweeps the seed layer on the substrate face, and displaces the air
from the features within the substrate face. This sweeping action
by the meniscus minimizes either the formation of air bubbles 3002
or air bridges 3102 between the substrate 22 and the electric
contact element 67, and limits the formation of air bubbles within
the features on the substrate seed layer. The preferred d.alpha./dt
rate is a function of such factors as the tilt angle .alpha., the
composition of the electrolyte solution, and the surfaces of the
substrate 22 and the electric contact element 67. After full
immersion of the substrate face, the rate of tilt angle .alpha.
change becomes zero as represented by 3310 since the substrate is
fully immersed and horizontal, and the substrate is in a position
to be electroplated. The majority of metal film is deposited on the
substrate seed layer during portion 3310. It is important to limit
the effect of, and the creation of, air bubbles 3002 or air bridges
3102 during portion 3310.
[0182] As shown in FIG. 28F and block 2912 of FIG. 29, the rotating
actuator 2464, and the head lift portion 2708 are all angled as a
unit by the head assembly frame about the pivot joint 2459 into the
process position. When the head portion is in the process position,
the substrate 22 is held in a substantially horizontal position
within the electrolyte solution. When the head portion 2450 tilts
the substrate horizontally into the process position, the entire
plating surface of the substrate 22 is immersed in the electrolyte
solution.
[0183] When the head portion 2450 is processed in the process
position shown in block 2914 of FIG. 29, the head portion 2450
supports the substrate 22 in a position where the plating surface
is immersed in the electrolyte solution contained in the
electrolyte cell. Portions of the head portion 2450 including the
contact housing 2765, the thrust plate 66, the electric contact
element 67 are rotated between about 0 and about 200 RPM,
preferably about 20 to about 40 RPM. The rotation of the substrate
22 provides for a uniform deposition of the metal ions across the
plating surface. The rotation of substrate 22 and the rotating
portions of head portion 2450 do not create too much turbulence in
the electrolyte solution as would be created by excessive angular
rotation within the electrolyte solution. The metal ions produced
by the reaction between the electrolyte solution and the anode 16
is deposited on the plating surface of the substrate 22 when the
substrate holder system 14 is in the process position.
[0184] As shown in FIG. 28G and block 2916 of FIG. 29, the head
portion 2450 is then displaced by the substrate holder system 14
into the dry position after the processing is performed on the
substrate 22. To provide for the displacement between the process
position shown in FIG. 28F and the dry position shown in FIG. 28G,
lift guide 2466 is translationally displaced upwardly relative to
the mounting slide 2460. Additionally, the head assembly 2410 is
rotated upwardly about the pivot joint 2459. When the head portion
2450 is in the dry position, the substrate is rotated between about
600 and about 2500 RPM, preferably about 2000 RPM. This rotation
effects drying of the substrate 22 by centrifugal action.
Alternatively, the substrate 22 can be transported to a separate
spin-rinse-dry unit as shown in the embodiment of FIG. 4.
[0185] As shown in FIG. 28H and block 2918 of FIG. 29, the head
portion 2450 is then raised into the exchange position by the lift
guide 2466 being translationally displaced upwardly relative to the
mounting slide 2460. When the head portion is in the exchange
position, the thrust plate 66 is raised by an amount that is
sufficient for a robot to remove the substrate 22 from the
substrate holder assembly. Following the raising of the thrust pad,
a first robot blade, not shown, is typically inserted between the
substrate 22 and the thrust plate to remove a first processed
substrate. Another robot blade inserts a new substrate to be
processed on to the electric contact element. The thrust pad is
then lowered to secure the substrate in position within the
substrate holder assembly. The metal deposition process depicted in
FIGS. 28A to 28H is then performed on the new substrate.
[0186] While the above provides one embodiment of a substrate
holder system 14 that can be used to tilt the substrate from
horizontal during immersion of the substrate into the electrolyte
solution, any device that can secure the substrate in a tilted
position upon immersion can be used. For example, FIG. 36 shows
another embodiment of substrate holder system 14 that comprises a
support mount 3609, a support 3610, a pivot joint 3611, the
rotatable head actuator 2410, and a controllable adjustable member
3602. In one embodiment, the rotatable head actuator 2410 is
configured as described in FIG. 27.
[0187] The support mount 3609 comprises a lateral track 3650, a
lateral follower 3652, a vertical track 3654, and a vertical
follower 3656. The lateral track 3650 is rigidly secured at one, or
both ends to a physically grounded surface 3658. The lateral
follower 3652 is constrained to follow the lateral track 3650 by a
tight-fitting connection, a plurality of wheel followers, an air
cushion, or another similar sliding connection. An actuator 3660,
that is controlled by the controller 222 shown in FIG. 3,
controllably displaces the lateral follower 3652 along the lateral
track 3650.
[0188] The vertical track 3654 is rigidly affixed to the lateral
follower 3652 by welding, bolts, rivets, or other known connectors
such that the vertical track 3654 follows the lateral motion of the
lateral follower 3652. The vertical follower 3656 is constrained to
follow the vertical track 3654 by a tight-fitting connection, a
plurality of wheel followers, an air cushion, or another similar
sliding connection. An actuator 3666, that is controlled by the
controller 222, controllably displaces the vertical follower 3656
along the vertical track 3650.
[0189] The head assembly 2410 is pivotally connected to the
vertical follower 3656 by the pivot joint 3611. The pivot joint
3611 is actuated by a pivot actuator 3670 that includes a pivot
joint follower wheel 3672, a pivot joint drive wheel 3674, and a
coupling belt 3676. The coupling belt 3676 transfers rotational
motive force from the pivot joint drive wheel 3674 to the pivot
joint follower wheel 3672 to rotate the head assembly between the
tilted position shown in solid in FIG. 27, and the upright position
shown by dotted lines 3678. The pivot joint drive wheel 3674 is
driven by an actuator such as a rotary stepper motor, a drive
motor, or any known type of rotational motor.
[0190] The support mount 3609 is thus able to displace the head
assembly 2410 in three directions. First, displacing the lateral
follower 3652 relative to the lateral track 3650 displaces the head
assembly 2410 in the X-direction shown in the coordinate axis 3620.
Second, displacing the vertical follower 3656 relative to the
vertical track 3654 displaces the head assembly 2410 in the
Z-direction shown in the coordinate axis 3620. Third, pivoting the
pivot joint follower wheel 3672 tilts the head assembly in a
direction indicated by arrow 3680.
[0191] In another embodiment, the pivot actuator 3670 can be
provided by a piston or linear drive member extending between an
offset link connected, not shown, to the pivot joint 3611 and the
support 3610. In this configuration, the linear actuation of the
piston or linear drive member is converted into rotational motion
of the head assembly 2410 about pivot joint 3611 by the offset of
the offset link.
[0192] The support mount 3609 can raise, lower, or laterally
displace the head actuator 2410 while being maintained in a
horizontal orientation. A robot device, not shown, can also be used
to provide motion to the support 3610 in the X-direction and the
Z-direction as shown by coordinate axis 3620.
[0193] To immerse the head assembly 2410 into the electrolyte
solution in the process cell, the substrate is tilted at the tilt
angle .alpha. by the pivot actuator 3670. The support may be
translated laterally in the X direction to align the head assembly
with the process cell by the translation of the robot device that
translates the support 3610. The support 3610 is then displaced
downward by the actuation of the actuator 3666 on the vertical
follower 3656 of the support mount 3609 to immerse the substrate
into the electrolyte solution contained in the process cell. The
coordinated motion of the pivot actuator 3670 and the actuator 3666
is controlled by the controller 222 in a manner to limit any
portion of the head assembly 2410 from contacting any portion of
the process cell. The head assembly 2410 is then moved into the
horizontal level position (.alpha.=0) by displacement of the pivot
actuator 3670 under the control of the controller 222. During the
leveling of the head assembly, the head assembly may have to be
concurrently aligned with the process cell by the actuator 3666
displacing the head assembly 2410 in the X direction. The head
assembly is then removed from the process cell by displacement of
the actuator 3666.
[0194] While the foregoing is directed to the preferred embodiment
of the present invention, other and further embodiments of the
invention may be devised without departing from the basic scope
thereof.
* * * * *