U.S. patent application number 11/490883 was filed with the patent office on 2008-01-24 for method for conditioning a polishing pad.
This patent application is currently assigned to Applied Materilas, Inc.. Invention is credited to Jim K. Atkinson, Liang-Yuh Chen, Jie Diao, Renhe Jia, Lakshmanan Karuppiah, Stan D. Tsai, You Wang.
Application Number | 20080020682 11/490883 |
Document ID | / |
Family ID | 38972028 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080020682 |
Kind Code |
A1 |
Jia; Renhe ; et al. |
January 24, 2008 |
Method for conditioning a polishing pad
Abstract
A method of conditioning processing pads increases the removal
rate of conductive material from a substrate surface during
polishing. In this method, the direction of rotation of the
processing pad relative to the conditioning disc during
conditioning is opposite the direction of rotation of the
processing pad relative to the substrate during polishing.
Inventors: |
Jia; Renhe; (Berkeley,
CA) ; Diao; Jie; (San Jose, CA) ; Wang;
You; (Cupertino, CA) ; Tsai; Stan D.;
(Fremont, CA) ; Atkinson; Jim K.; (Los Gatos,
CA) ; Karuppiah; Lakshmanan; (San Jose, CA) ;
Chen; Liang-Yuh; (Foster City, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materilas, Inc.
|
Family ID: |
38972028 |
Appl. No.: |
11/490883 |
Filed: |
July 21, 2006 |
Current U.S.
Class: |
451/56 |
Current CPC
Class: |
B24B 53/017
20130101 |
Class at
Publication: |
451/056 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Claims
1-23. (canceled)
24. A method of processing a substrate, comprising: rotating the
substrate in a first direction; contacting the substrate with a
conductive polishing surface of a processing pad that is rotating
in the first direction to perform a polishing process;
incrementally increasing a voltage applied to the processing pad;
removing the substrate from the conductive polishing surface;
reversing the direction of the processing pad to rotate in a second
direction; and contacting the conductive polishing surface of the
processing pad with a conditioning element that is rotating in the
second direction to perform a conditioning process.
25. The method of claim 24, wherein a first region of the
processing pad is used to remove a conductive material from the
substrate at a first removal rate and a second region of the
processing pad is used to remove a conductive material from the
substrate at a second removal rate, each of the first region and
second region being conditioned differently.
26 The method of claim 24, wherein the voltage is increased in 0.2
volt increments.
27. The method of claim 24, wherein the first direction is a
clockwise direction and the second direction is a counter clockwise
direction.
28. The method of claim 24, wherein the first direction is a
counter clockwise direction and the second direction is a clockwise
direction.
29. The method of claim 24, further comprising: supplying a
polishing composition to the surface of the substrate.
30. A method of processing a substrate in a polishing apparatus,
wherein the polishing apparatus has a conditioning element, a
processing pad, and a substrate holder, the method comprising: (a)
rotating the conditioning element and the processing pad to
condition a conductive surface of the processing pad; (b)
positioning a substrate in the substrate holder; and (c) rotating
the substrate and the processing pad to polish the surface of the
substrate while applying an increasing voltage to the conductive
surface, wherein the rotational direction in (a) and (c) are
opposite.
31. The method of claim 30, wherein: (a) comprises rotating the
processing pad and the conditioning element in a clockwise
direction; and (c) comprises rotating the processing pad the
substrate in a counter clockwise direction.
32. The method of claim 30, wherein: (a) comprises rotating the
conditioning element in a counter clockwise direction; and (c)
comprises rotating the substrate in a clockwise direction.
33. The method of claim 30, wherein a first region of the
processing pad is used to remove a conductive material from the
substrate at a first removal rate and a second region of the
processing pad is used to remove a conductive material from the
substrate at a second removal rate, each of the first region and
second region being conditioned differently.
34. The method of claim 33, wherein the surface of the substrate
contains a copper-containing material.
35. The method of claim 30, wherein polishing the surface of a
substrate comprises applying a bias between a first electrode and a
second electrode, wherein the first electrode is in electrical
contact with the substrate.
36. The method of claim 30, further comprising: supplying a
polishing composition to the surface of the substrate.
37. A method of processing a substrate in a polishing apparatus,
wherein the polishing apparatus has a conditioning element, a
processing pad, and a substrate holder, the method comprising:
conditioning a conductive surface of the processing pad by rotating
the conditioning element and the processing pad a first direction;
positioning a substrate in the substrate holder; and polishing the
surface of the substrate by applying an increasing voltage to the
processing pad and rotating the substrate and the processing pad in
a second rotational direction.
38. The method of claim 37, wherein: the conditioning of the
conductive surface of the processing pad comprises rotating the
processing pad and the conditioning element in a clockwise
direction; and the polishing of the surface of the substrate
comprises rotating the processing pad the substrate in a counter
clockwise direction.
39. The method of claim 37, wherein: the conditioning of the
conductive surface of the processing pad comprises rotating the
processing pad in a counter clockwise direction and rotating the
conditioning element in a counter clockwise direction; and the
polishing of the surface of the substrate comprises rotating the
processing pad in a clockwise rotational direction and rotating the
substrate in the clockwise direction.
40. The method of claim 37, wherein the polishing of the surface of
the substrate further comprises applying a bias between a first
electrode and a second electrode, wherein the first electrode is in
electrical contact with the substrate.
41. The method of claim 37, further comprising: supplying a
polishing composition to the surface of the substrate.
42. The method of claim 37, wherein the voltage is increased at
about 0.2 volt increments.
43. The method of claim 37, wherein the polishing of the surface of
the substrate further comprises removing a copper-containing
material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention generally relate to the
fabrication of integrated circuits and more particularly to the
removal of conductive material from a substrate.
[0003] 2. Description of the Related Art
[0004] In VLSI and ULSI semiconductor manufacturing, reliable
formation of multilevel interconnects is important to the continued
effort to increase circuit density and quality of individual
substrates and die. Multilevel interconnects are formed using
sequential material deposition and material removal techniques on a
substrate surface to form features therein. As layers of materials
are sequentially deposited and removed, the uppermost surface of
the substrate may become non-planar across its surface and require
planarization prior to further processing. Planarization, or
"polishing," is a process in which material is removed from the
surface of the substrate to form a generally even, planar surface.
Planarization is useful in removing excess deposited material,
undesired surface topography, and surface defects, such as surface
roughness, agglomerated materials, crystal lattice damage,
scratches, and the like. Planarization also provides an even
surface for subsequent photolithography and other semiconductor
manufacturing processes.
[0005] Electrochemical mechanical polishing (ECMP) is one method of
planarizing a surface of a substrate. ECMP is a method that removes
conductive materials, such as copper, from a substrate surface by
electrochemical "anodic" dissolution while polishing the substrate
with a reduced mechanical abrasion and pressure compared to
conventional chemical mechanical planarization (CMP) processes. The
greatly reduced down-pressure required for ECMP allows the
planarization of substrates having delicate low-k materials
deposited thereon. Electrochemical dissolution is performed by
applying an electrical bias between a cathode and a substrate
surface to remove conductive materials from the substrate surface
into a surrounding electrolyte, such as a polishing composition.
The bias may be applied to the substrate surface by a conductive
contact disposed on or through a polishing material upon which the
substrate is processed. The polishing material may be, for example,
a processing pad disposed on a rotating platen. The polishing
composition may be disposed in the processing pad and the metal
ions on the substrate surface dissolve into the surrounding
polishing composition.
[0006] A typical ECMP system includes a substrate support and two
electrodes disposed within an electrolyte containment basin. The
substrate is in electrical contact with one of the electrodes, and
in effect, the substrate becomes an anode during processing for
material removal. A mechanical component of the polishing process
is performed by providing a relative motion between the substrate
and the processing pad while in contact with each other that
enhances the removal of the conductive material from the
substrate.
[0007] The removal rate of conductive material from a substrate
surface is an important metric for the performance of an ECMP
processing system. Lower removal rate results in a longer
processing time, thereby increasing the production cost per
substrate. Process parameters used to affect removal rate during
ECMP include voltage applied between the electrodes, makeup of
electrolyte/polishing composition, substrate pressure against the
processing pad, polishing head rpm, and processing pad rpm.
[0008] Conventionally an abrasive conditioning element, such as a
diamond conditioning disk, or a brush conditioner, such as a
Nylon.TM. brush, is periodically used to refurbish the processing
pad surface to improve polishing results. A conditioning element is
applied to the processing pad, often in conjunction with a suitable
cleaning fluid, using a spinning conditioning disc that also
translates laterally across the surface of the processing pad.
After such conditioning, the removal rate of the processing pad is
increased and fewer substrate surface defects are formed by the
processing pad. A conditioning process is also typically performed
on unused processing pads in order to remove native oxides and
other passivation layers formed on the conductive materials therein
in order to "break-in" the processing pad.
[0009] FIG. 1 is a schematic plan view of an ECMP processing
station 100, having a rotating substrate polishing head 101, a
processing pad 103 disposed on a rotating platen (not shown) and a
conditioning head 104 disposed on a swing arm 105. In addition to
rotation, polishing head 101 is also typically adapted to translate
linearly or curvilinearly across processing pad 103 during ECMP
processing.
[0010] ECMP processing station 100 performs both substrate
processing and processing pad conditioning. In operation, a
substrate is mounted on polishing head 101 and is processed
face-down, i.e., production side down, during the ECMP process.
Polishing head 101 and processing pad 103 rotate continuously in
one direction, in this example counterclockwise. Polishing head 101
may also translate linearly across the surface of processing pad
103. During processing pad conditioning, processing pad 103
continues to rotate in the same direction as during the ECMP
process, and conditioning head 104 rotates continuously in that
same direction. Conditioning head 104 is also displaced along path
120 in a sweeping motion during the conditioning process to
uniformly and completely condition the entire surface of processing
pad 103.
[0011] While the processing pad conditioning method described above
improves the removal rate of ECMP processing pads, even higher
removal rates are desirable in the ECMP process. Higher ECMP
removal rates result in higher throughput and, and hence, lower
processing cost per substrate. In addition, higher ECMP removal
rates for a given processing pad allow more substrates to be
processed before reconditioning of the pad is necessary. Because
the reconditioning process is generally time-consuming, a longer
period between such reconditioning significantly reduces ECMP
system downtime, which also lowers processing cost per
substrate.
SUMMARY OF THE INVENTION
[0012] The present invention provides a method of conditioning
processing pads that increases the removal rate. According to
embodiments of the present invention, conductive material removal
rates will be increased during the ECMP process if the direction of
rotation of the processing pad relative to the conditioning disc is
opposite the direction of rotation of the processing pad relative
to the substrate.
[0013] According to a first embodiment, the relative rotation
between the conditioning element and the processing pad is produced
by rotating both the conditioning element and the processing pad in
a first rotational direction. The relative rotation between the
substrate and the processing pad during polishing is produced by
rotating both the substrate and the processing pad in a second
rotational direction, wherein the second rotational direction is
opposite to the first rotational direction.
[0014] According to a second embodiment, the relative rotation
between the conditioning element and the processing pad is produced
by rotating the processing pad in a first rotational direction and
the relative rotation between the substrate and the processing pad
is produced by rotating the processing pad in a second rotational
direction, wherein the second rotational direction is opposite to
the first rotational direction.
[0015] According to a third embodiment, the relative rotation
between the conditioning element and the processing pad is produced
by rotating the conditioning element in a first rotational
direction and rotating the processing pad in a second rotational
direction, wherein the first rotational direction is the opposite
of the second rotational direction. The relative rotation between
the substrate and the processing pad during polishing is produced
by rotating the substrate in the second rotational direction and
the processing pad in the first rotational direction.
[0016] According to a fourth embodiment, the relative rotation
between the conditioning element and the processing pad is produced
by rotating one of the conditioning element or the processing pad
in a first rotational direction while the other remains
rotationally stationary. The relative rotation between the
substrate and the processing pad during polishing is produced by
rotating one of the substrate or the processing pad in a second
rotational direction while the other remains rotationally
stationary, wherein the first rotational direction is the opposite
of the second rotational direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0018] FIG. 1 (Prior Art) is a schematic plan view of an ECMP
processing station.
[0019] FIG. 2 is a cross-sectional view of one example of an ECMP
station that may benefit from aspects of the invention.
[0020] FIG. 3 is a schematic plan view of an exemplary
planarization platform.
[0021] FIG. 4 is a schematic plan view of an ECMP processing
station.
[0022] FIG. 5 illustrates the removal rate of conductive material
during an ECMP process for two substrates.
[0023] FIG. 6 illustrates the removal rate of conductive material
during an ECMP process for two substrates.
[0024] FIG. 7 is a schematic plan view of an ECMP processing
station in which the processing pad is divided into three
regions.
[0025] For clarity, identical reference numerals have been used,
where applicable, to designate identical elements that are common
between figures.
DETAILED DESCRIPTION
[0026] FIG. 2 is a cross-sectional view of one example of an ECMP
station 200 that may be used to practice aspects of the invention.
The process cell 200 generally includes a basin 204 and a polishing
head 202. A substrate 208 is retained in the polishing head 202 and
lowered into the basin 204 during processing in a face-down, i.e.,
production side down, orientation. An electrolyte, as described
herein, flows into the basin 204 and is in contact with the surface
of substrate 208 and a processing pad assembly 222, while the
polishing head 202 places the substrate 208 in contact with the
processing pad assembly 222. The basin 204 includes the processing
pad assembly 222, a bottom 244 and sidewalls 246 that define a
container that houses the processing pad assembly 222. The
sidewalls 246 include a port 218, formed therethrough to allow
removal of polishing composition from the basin 204. The port 218
is coupled to a valve 220 to selectively drain or retain the
polishing composition in the basin 204.
[0027] The processing pad assembly 222 generally includes a
processing pad 203 coupled to a backing 207. The backing 207 may
also be coupled to an electrode 209. The processing pad 203 and the
backing 207 have a plurality of holes or pores formed therein to
allow the polish composition to make contact with, and thus provide
a conductive path between the substrate 208 and the electrode 209.
The processing pad 203 is used to apply a uniform bias to the
substrate surface by use of a conductive surface that makes contact
with the surface of the substrate.
[0028] Processing pad 203 is a conductive pad that has a working
surface adapted to polish the production side, i.e., the electronic
device side, of substrate 208 during ECMP processing. The working
surface may be smooth or patterned to facilitate distribution of a
polishing composition and/or electrolyte over the surface of the
processing pad assembly 222. Patterns may include grooves, cutouts,
perforations, and the like.
[0029] Processing pad 203 may be fabricated from polymeric
materials compatible with the process chemistry and includes
conductive material or conductive contact elements extending
therefrom. Examples of suitable polymeric materials include
polyurethane, polycarbonate, fluoropolymers, PTFE, PTFA,
polyphenylene sulfide (PPS), or combinations thereof. For example,
processing pad 203 may be fabricated from a conductive composite,
i.e., the conductive elements are dispersed integrally with or make
up the material of the polishing surface. Conductive composites
include a polymer matrix having conductive particles dispersed
therein or a conductive-coated fabric, among others.
[0030] Alternatively, processing pad 203 may consist of a fabric
layer having a conductive layer disposed thereover, wherein the
conductive layer has an exposed surface adapted to polish substrate
208. The fabric layer may be woven or non-woven. The conductive
layer may be comprised of a soft metal and, in one example, the
exposed surface may be planar. Examples of processing pad 203 that
may be adapted to benefit from the invention are described in
commonly assigned U.S. Pat. No. 6,979,248, U.S. Pat. No. 6,988,942,
and U.S. Pat. No. 6,991,528, each of which is hereby incorporated
by reference in its entirety.
[0031] Alternatively, processing pad 203 may include one or more
intervening layers (not shown). For example, a conductive foil may
be disposed below processing pad 203 to promote uniform power
distribution thereacross. In addition, an interposed pad may be
provided below the conductive foil to increase mechanical
attributes of processing pad 203. Lastly, a subpad may be provided
to tailor the compliance of the processing pad 203.
[0032] The substrate 208 and the processing pad assembly 222
disposed in the basin 204 are moved relative to each other to
provide a desired polishing motion. The polishing motion includes
at least one motion defined by an orbital, rotary, or curvilinear
motion, or combinations thereof, to provide a relative rotational
motion between the surface of substrate 208 and the processing
surface of processing pad assembly 222. In one example, the
polishing motion may be achieved by rotating polishing head 202,
basin 204, or both. Additional components to the polishing motion
may be included by linearly or curvilinearly translating polishing
head 202 relative to basin 204. In the example depicted in FIG. 2,
the polishing head 202 is coupled to a drive system 210. The drive
system 210 can move the polishing head 202 with a rotary, orbital,
or sweep motion, or combinations thereof. During ECMP, basin 204,
and therefore processing pad 203, is rotated at a velocity between
about 3 to about 100 rpm, and the polishing head 202 is rotated at
a velocity between about 5 to about 200 rpm. Drive system 210 may
also linearly translate polishing head 202 at a radial velocity of
between about 2 to about 8 centimeters per second. Preferred ranges
for processing circular 300 mm substrates are a rotational velocity
for basin 204 between about 5 to about 40 rpm, a rotational
velocity for polishing head 202 between about 5 to about 50 rpm,
and a linear, i.e., radial, velocity of about 2 to about 8
centimeters per second.
[0033] A power source 224 is coupled to the processing pad assembly
222 by electrical leads 223A, 223B. The power source 224 applies an
electrical bias to the processing pad assembly 222 to drive an
electrochemical process described herein. During ECMP, substrate
208 is exposed to the polishing composition and is in electrical
contact with processing pad 203. A bias from power source 224 is
then applied between substrate 208 and processing pad 203. The bias
is generally provided to produce anodic dissolution of the
conductive material from the surface of substrate 208 at a current
density up to about 55 mA/cm.sup.2, which correlates to an applied
current of up to about 40 amps to process substrates with a
diameter of about 300 mm. The bias may be varied in power and
duration depending on numerous factors, including the thickness and
type of conductive material to be removed from the substrate
surface. Substrate 208 is typically exposed to the power
application and polishing composition (described below) for a
period of time sufficient to remove at least a portion or all of
the desired material disposed thereon. For example, the substrate
may be exposed to the polishing composition and power between about
5 seconds and about 300 seconds, but may vary depending on the
thickness and type of conductive material to be removed.
[0034] The polishing head 202 retains the substrate 208 during
processing. In one embodiment, the polishing head 202 includes a
housing 214 enclosing a bladder 216. Bladder 216 may be deflated
when contacting the substrate to create a vacuum therebetween, thus
securing the substrate to the polishing head 202 to allow placement
and removal of the substrate. The bladder 216 may additionally be
inflated and pressurized to assure contact between the substrate
and the processing pad assembly 222 retained in basin 204. A
retaining ring 238 is coupled to housing 214 and circumscribes
substrate 208 to prevent the substrate from slipping from polishing
head 202 while being processed. During ECMP, substrate 208 and
processing pad 203 contact each other at a pressure of less than
about 2 psi (13.8 kPa). For example, a contact pressure between the
substrate and polishing pad between about 0.01 psi (69 Pa) and
about 1.5 psi (10.2 kPa), may be used for polishing the surface of
substrate 208. The optimal contact pressure therebetween is
dependent on the underlying non-conductive materials on the surface
of the substrate, what conductive material is being removed, the
makeup of the polishing composition, and other factors.
[0035] The basin 204 is generally fabricated from a plastic such as
fluoropolymers, TEFLON.RTM. polymers, or other materials that are
compatible or non-reactive with the polishing composition or other
chemicals used in ECMP station 200. The basin 204 is rotationally
supported above a base 206 by bearings 234. A drive system 236 is
coupled to the basin 204 and rotates the basin 204 during
processing. A catch basin 228 is disposed on the base 206 and
circumscribes the basin 204 to collect processing fluids, such as
polishing composition, that flow out of port 218 disposed through
the basin 204 during and/or after processing. An outlet drain 219
and outlet valve 219A are incorporated in the invention to allow
the polishing composition in the catch basin to be sent to a
reclaim system (not shown) or a waste drain (not shown).
[0036] A polishing composition delivery system 232 is generally
disposed adjacent basin 204. Polishing composition delivery system
232 includes a nozzle or outlet 230 coupled to a polishing
composition source 242. The outlet 230 delivers polishing
composition or other processing fluids from the polishing
composition source 242 into the basin 204, typically at a rate
between about 0.1 and 2.0 liters per minute, depending on the
specific ECMP process. The polishing composition source 242
schematically shown here includes a source of all of the chemicals
required to supply and support the polishing composition during
processing. The polishing composition may contain abrasive
particles to assist in the mechanical removal of conductive
materials from substrate 208. The abrasive content of the polishing
composition is selected based on the particular ECMP process. In
addition, the abrasive content of the polishing composition may be
varied during the ECMP process, for example from about 0 wt % to
0.4 wt. %. Examples of polishing compositions and methods of
varying the abrasive content thereof are described in detail in
commonly assigned U.S. patent application Ser. No. 10/957,199,
filed Oct. 1, 2004 by Rashid et al., which is hereby incorporated
by reference herein.
[0037] A conditioning apparatus 250 is disposed proximate basin 204
to periodically condition or regenerate processing pad 203 of
processing pad assembly 222. Typically, conditioning apparatus 250
includes an arm 252 coupled to a stanchion 254 that is adapted to
position and sweep a conditioning element 258 across processing pad
assembly 222. Conditioning element 258 is coupled to the arm 252 by
a shaft 256 to allow clearance between the arm 252 and sidewalls
246 of basin 204 while the conditioning element 258 is in contact
with processing pad assembly 222.
[0038] Conditioning element 258 is typically a diamond or silicon
carbide disk, which may be patterned to enhance the process of
conditioning the surface of processing pad 203. Alternatively, the
conditioning element 258 may be made of a Nylon.TM. brush or
similar conditioner for in-situ conditioning of processing pad 203.
One conditioning element 258 that may be adapted to benefit from
aspects of the invention is described in U.S. patent application
Ser. No. 09/676,280, filed Sep. 28, 2000 by Li, et al, which is
incorporated herein by reference to the extent not inconsistent
with the claimed invention.
[0039] In operation, conditioning element 258 contacts processing
pad 203 with a down-force in the range of about 0.01 to about 10
lbs, the optimal pressure depending on factors such as the
composition of the conditioning element 258 and the processing pad
203. A cleaning fluid may be dispensed onto processing pad 203,
either through conditioning element 258 or via a nozzle external
thereto. Alternatively, an electrolyte for polishing is dispensed
onto processing pad 203 to maintain a liquid film between
conditioning element 258 and the pad surface. Cleaning fluid or
electrolyte is generally supplied at a rate between about 10 ml/min
to about 500 ml/min. The conditioning element 258 may be rotated at
a speed between about 5 to about 100 rpm. The conditioning element
258 may be swept across the surface of processing pad 203 over a
range between about 0.1 and 14 inches. The frequency of the sweep
may be in the range of about 2 to about 40 cycles/minute.
[0040] The cleaning fluid is formulated to dissolve polishing
by-products and is generally used to clean processing pad 203. For
example, for cleaning processing pads utilized for copper
polishing, the cleaning fluid may include amine solutions,
carboxylic acid solutions, combinations thereof, and the like. The
pH value of the cleaning solution may be adjusted to substantially
match that of the ECMP processing fluid. In this way, in the event
that the cleaning fluid mixes with the polishing fluid, chemical
incompatibility issues therebetween are avoided that would
otherwise affect polishing performance. Acid-based, base-based, and
neutral cleaning solutions may be applied by conditioning apparatus
250, depending on the conductive material to be removed by ECMP and
on the composition of processing pad 203. Examples of cleaning
solutions suitable for use by conditioning apparatus 250 are
described in detail in commonly assigned U.S. patent application
Ser. No. 11/209,167, filed Aug. 22, 2005 by Wang et al., which is
hereby incorporated by reference herein.
[0041] The ECMP station 200 described above may be disposed on a
polishing platform, such as the planarization platform illustrated
in FIG. 3. FIG. 3 is a schematic plan view of an exemplary
planarization platform 300. Platform 300 may have at least one ECMP
station 200 as described above in conjunction with FIG. 2, and
optionally, the platform 300 may also include at least one
conventional CMP polishing station 306 disposed adjacent the ECMP
station 200. One such planarizing platform that may be adapted to
benefit from the invention is a REFLEXION.RTM. chemical mechanical
polisher available from Applied Materials, Inc. located in Santa
Clara, Calif. Examples of other polishing tools that may be adapted
to benefit from the invention are the MIRRA.RTM. chemical
mechanical polisher and the MIRRA MESA.TM. chemical mechanical
polishers also available from Applied Materials, Inc.
[0042] Platform 300 generally includes a base 308 that supports the
one or more ECMP stations 200, the one or more polishing stations
306, a transfer station 310, and a carousel 312. A loading robot
316 transfers substrates 314 to and from the transfer station 310
of the apparatus 300 and a factory interface 320. The factory
interface 320 may include a cleaning module 322, a metrology device
304, and one or more substrate storage cassettes 318. The carousel
312 has a plurality of arms 338, each respectively supporting one
of a plurality of polishing heads 208. Each polishing head 208
retains one substrate 314 during processing. Substrates are loaded
and unloaded from the polishing heads 208 by the load cup assembly
328. The carousel 312 moves the polishing heads 208 between the
load cup assembly 328 of the transfer station 310, the one or more
ECMP stations 200 and the one or more polishing stations 306. The
polishing head 208 retains the substrate 314 against the ECMP
station 200 or polishing station 306 during processing. The
arrangement of the ECMP stations 200 and polishing stations 306 on
the apparatus 300 allows for the substrate 314 to be sequentially
polished by moving the substrate between stations while being
retained in the same polishing head 208.
[0043] FIG. 4 is a schematic plan view of ECMP processing station
200, described above, having a rotating substrate polishing head
202 coupled to a drive system 210, a processing pad 203 disposed on
a rotating platen (not shown), and a rotating conditioning element
258 disposed on swing arm 252. As noted above, drive system 210 can
rotate, linearly translate, and sweep polishing head 202 across the
surface of processing pad 203 while pressing a surface of the
substrate against the processing surface of processing pad 203. In
so doing, a relative rotational motion is produced between the
substrate surface and processing pad 203 during the ECMP process.
Similarly, conditioning element 258 on swing arm 252 rotates to
provide a relative rotational motion between the surface of
conditioning element 258 and the processing surface of processing
pad 203 during the conditioning process.
[0044] According to a first embodiment of the invention, processing
pad 203 rotates counterclockwise and polishing head 202 rotates
counterclockwise during ECMP processing, and during the
conditioning and/or break-in process, processing pad 203 rotates
clockwise and conditioning element 258 rotates clockwise. According
to a second embodiment of the invention, processing pad 203 rotates
clockwise and polishing head 202 rotates clockwise during ECMP
processing, and during the conditioning and/or break-in process,
processing pad 203 rotates counterclockwise and conditioning
element 258 rotates counterclockwise. In a third embodiment, the
direction of rotation of the polishing pad during polishing is
opposite the direction of rotation of the polishing pad during
conditioning, while the direction of rotation of the substrate and
the conditioning head are the same. In each embodiment, the
relative rotational motion produced between processing pad 203 and
conditioning element 258 is substantially the opposite that of the
relative rotational motion produced between processing pad 203 and
substrate 208 during ECMP processing.
[0045] FIG. 5 illustrates the removal rate of conductive material
during an ECMP process for two substrates, substrate 501, 502.
Substrates 501, 502 were processed in an ECMP station substantially
similar to ECMP station 200, described above in conjunction with
FIG. 2. Substrate 501 was processed with a processing pad that had
been conditioned by a conventional method and substrate 502 was
processed with a processing pad that had been conditioned using the
first embodiment of the invention described above in conjunction
with FIG. 2. Similarly, FIG. 6 illustrates the removal rate of
conductive material conductive material during an ECMP process for
two substrates, substrate 601, 602. Substrate 601 was processed
with a processing pad that had been conditioned by a conventional
method and substrate 602 was processed with a processing pad that
had been conditioned using the second embodiment of the invention
described above in conjunction with FIG. 2.
[0046] In FIGS. 5 and 6, the abscissa represents time elapsed
during a number of ECMP processes, and the ordinate represents
polishing current measured during those ECMP processes. Because
conductive material removal is largely due to anodic dissolution
during ECMP, the removal rate of conductive material is known to be
proportional to polishing current, so in effect FIGS. 5 and 6
illustrate removal rate of conductive material vs. time. In the
ECMP process illustrated in FIGS. 5 and 6, every 20 seconds
electrode bias is incrementally increased 0.2 V, i.e., from 1.6 to
2.2 V, as indicated by voltage values 521-524.
[0047] Referring back to FIG. 5, the removal rate is seen to be
substantially higher for substrate 502 than for substrate 501. In
this example, the removal rate during the processing of substrate
502 at 2.2 V was approximately twice the removal rate during the
processing of substrate 501 at the same electrical bias. Except for
the method of conditioning processing pad 203, all other process
parameters that affect removal rate, including polishing head
pressure, the material being removed from substrate, applied
voltage, makeup of the polishing composition, etc. were
substantially identical when processing substrate 501 and substrate
502.
[0048] Referring to FIG. 6, a similar significant improvement in
removal rate is demonstrated between two substrates 601, 602. In
this case, removal rate of the polishing pad conditioned by an
aspect of the inventive method was over three times that for a
polishing pad conditioned by a conventional method.
[0049] The invention may be applied to an ECMP process in which the
processing pad and the substrate are rotated in opposite
directions, e.g., clockwise and counterclockwise, respectively.
During the conditioning process, the processing pad is rotated
clockwise and the conditioning element is rotated counterclockwise,
so that the relative rotational motion produced between the
processing pad and the conditioning element is opposite to the
relative rotational motion between the processing pad and the
substrate. In another aspect, the processing pad rotates in the
same direction in both the ECMP process and the conditioning
process, and a substantially different relative rotation motion is
provided during the conditioning process by rotating the
conditioning element in the opposite direction that the substrate
is rotated during the ECMP process.
[0050] An ECMP process, wherein a relative rotational motion
between a substrate and a processing pad is produced by rotating
only the substrate or only the processing pad, may also benefit
from the application of an aspect of inventive method. For example,
if the processing pad remains rotationally stationary during the
ECMP process and only the substrate is rotated, then during the
conditioning process, the conditioning head may be rotated in the
opposite direction, to provide a substantially different relative
rotational motion. In so doing, the resultant removal rate of the
processing pad can be improved.
[0051] Aspects of the invention further contemplate the application
of different conditioning processes on different regions of a
processing pad. By conditioning a processing pad differently in
different regions, a single processing pad may provide a different
removal rate in each region. In effect, this provides an additional
process parameter, i.e., which region of the pad is being used, for
modulating removal rates during the ECMP process. It may be
desirable in some applications for the removal rate to vary during
an ECMP process, but typical process parameters affecting removal
rate, e.g., down-pressure, polishing composition abrasive content,
etc., may have been optimized to a certain value and need to be
kept constant during the ECMP process. This aspect of the invention
allows removal rate of a conductive material from a substrate to be
varied during the ECMP process even when conventional process
parameters are fixed.
[0052] FIG. 7 is a schematic plan view of an ECMP processing
station in which the processing pad 203A is divided into three
regions, 701-703. Each of regions 701-703 is conditioned by a
different respective conditioning process, so that processing pad
203A may thereafter provide three different removal rates during
ECMP processing. In this way, processing pad 203A may provide a
removal rate profile consisting of the three different removal
rates when processing a substrate sequentially in regions 701-703
without altering other ECMP process parameters. A different
conditioning process may be performed on each of regions 701-703,
respectively, by altering one or more of the process parameters of
the conditioning process, including down-pressure of the
conditioning element against the processing pad, conditioning
element rotational velocity, processing pad rotational velocity,
direction of conditioning element rotation, direction of processing
pad rotation, and combinations thereof.
[0053] Any number of different processing regions may be prepared
on the surface of processing pad 203A, limited only by the ratio of
the diameter of processing pad 203A to the diameter of a substrate
to be processed therewith. For example, if the diameter of
processing pad 203A is at least three times the diameter of a
substrate to be processed therewith, then up to three discrete
concentric regions, each with a different associated removal rate,
may be formed on processing pad 203A during the conditioning
process.
[0054] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *