U.S. patent application number 12/843793 was filed with the patent office on 2012-01-26 for real-time monitoring of retaining ring thickness and lifetime.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Garlen C. Leung, Peter McReynolds, Gregory E. Menk, Thomas H. Osterheld, Gopalakrishna B. Prabhu, Eric S. Rondum, Adam H. Zhong.
Application Number | 20120021671 12/843793 |
Document ID | / |
Family ID | 45494015 |
Filed Date | 2012-01-26 |
United States Patent
Application |
20120021671 |
Kind Code |
A1 |
McReynolds; Peter ; et
al. |
January 26, 2012 |
REAL-TIME MONITORING OF RETAINING RING THICKNESS AND LIFETIME
Abstract
A method and apparatus for monitoring the condition of a surface
of a retaining ring disposed on a carrier head in a polishing
module is described. In one embodiment, a method for monitoring at
least one surface of a retaining ring coupled to a carrier head is
provided. The method includes moving the carrier head adjacent a
sensor device disposed in a polishing module, transmitting energy
from the sensor device toward the retaining ring, receiving energy
reflected from the retaining ring, and determining a condition of
the retaining ring based on the received energy.
Inventors: |
McReynolds; Peter; (San
Mateo, CA) ; Rondum; Eric S.; (San Ramon, CA)
; Leung; Garlen C.; (San Jose, CA) ; Zhong; Adam
H.; (Milpitas, CA) ; Menk; Gregory E.;
(Pleasanton, CA) ; Prabhu; Gopalakrishna B.; (San
Jose, CA) ; Osterheld; Thomas H.; (Mountain View,
CA) |
Assignee: |
APPLIED MATERIALS, INC.
Santa Clara
CA
|
Family ID: |
45494015 |
Appl. No.: |
12/843793 |
Filed: |
July 26, 2010 |
Current U.S.
Class: |
451/6 ;
451/8 |
Current CPC
Class: |
B24B 37/042 20130101;
B24B 37/005 20130101; B24B 37/32 20130101 |
Class at
Publication: |
451/6 ;
451/8 |
International
Class: |
B24B 49/12 20060101
B24B049/12 |
Claims
1. A method for monitoring at least one surface of a retaining ring
coupled to a carrier head, the method comprising: moving the
carrier head adjacent a sensor device disposed in a polishing
module; transmitting energy from the sensor device toward the
retaining ring; receiving energy reflected from the retaining ring;
and determining a condition of the retaining ring based on the
received energy.
2. The method of claim 1, wherein the transmitted and received
energy is a sound wave.
3. The method of claim 1, wherein the transmitted and received
energy is an optical signal.
4. The method of claim 1, wherein the transmitted and received
energy is a magnetic field.
5. The method of claim 1, wherein the energy is transmitted and
received through a liquid.
6. The method of claim 1, further comprising: moving the carrier
head adjacent a load cup assembly disposed in the polishing module,
the sensor device being disposed in a body of the load cup
assembly.
7. The method of claim 6, further comprising: actuating the sensor
device within the load cup assembly as the retaining ring is in the
line-of-sight of the sensor device.
8. The method of claim 7, wherein the received energy is indicative
of a thickness of the retaining ring.
9. The method of claim 1, further comprising: transferring a
substrate to the carrier head; and urging the substrate toward a
polishing surface of a polishing pad disposed in the polishing
module to perform a polishing process on the substrate.
10. The method of claim 9, wherein the received energy is
indicative of a thickness of the retaining ring, the method further
comprising: adjusting one or more parameters of the polishing
process based on a thickness of the retaining ring.
11. A method for monitoring at least one surface of a retaining
ring coupled to a carrier head, the method comprising: moving the
carrier head adjacent a load cup assembly disposed in a polishing
module, the sensor device being disposed in a body of the load cup
assembly; transmitting energy from the sensor device toward a
surface of the retaining ring as the retaining ring is in the
line-of-sight of the sensor device; receiving energy reflected from
the surface; and determining a thickness of the retaining ring
based on the received energy.
12. The method of claim 11, wherein the surface is a contact
surface of the retaining ring.
13. The method of claim 11, wherein the surface is a metallic
surface disposed inside the retaining ring.
14. The method of claim 11, wherein the surface is the bottom of a
groove formed in the retaining ring.
15. A method for monitoring at least one surface of a retaining
ring coupled to a carrier head, the method comprising: moving the
carrier head adjacent a load cup assembly disposed in a polishing
module, the sensor device being disposed in a body of the load cup
assembly; rinsing the retaining ring; transmitting energy from the
sensor device toward a surface of the retaining ring as the
retaining ring is in the line-of-sight of the sensor device;
receiving energy reflected from the surface; and determining a
thickness of the retaining ring based on the received energy.
16. The method of claim 15, wherein the surface is a contact
surface of the retaining ring.
17. The method of claim 15, wherein the surface is a metallic
surface disposed inside the retaining ring.
18. The method of claim 15, wherein the surface is the bottom of a
groove formed in the retaining ring.
19. The method of claim 15, wherein the transmitted and received
energy is a sound wave, an optical signal, an electrical signal, a
magnetic field, or combinations thereof.
20. The method of claim 15, wherein a contact surface of the
retaining ring is contacting an active surface of the body of the
load cup assembly when the energy is transmitted and received.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the invention relate to polishing systems for
polishing a substrate, such as a semiconductor substrate. More
particularly, to a method and apparatus for monitoring components
of a polishing system.
[0003] 2. Description of the Related Art
[0004] Chemical mechanical polishing (CMP) is one process commonly
used in the manufacture of high-density integrated circuits to
planarize or polish a layer of material deposited on a substrate.
The substrate may be provided to a polishing station on a polishing
system and retained in a carrier head that controllably urges the
substrate against a moving polishing pad. CMP is effectively
employed by providing contact between a feature side of the
substrate and moving the substrate relative to the polishing pad
while in the presence of a polishing fluid. Material is removed
from the feature side of the substrate that is in contact with the
polishing surface through a combination of chemical and mechanical
activity.
[0005] The carrier head typically includes a retaining ring that
circumscribes the substrate and may facilitate holding of the
substrate in the carrier head. One or more surfaces of the
retaining ring are typically in contact with the polishing pad
during polishing. While the retaining ring is adapted to endure
polishing of multiple substrates, the surfaces that are in contact
with the polishing pad experience wear and periodic replacement of
the retaining ring is necessary. Thus, inspection of the retaining
ring is necessary to monitor wear and determine replacement
intervals.
[0006] The conventional inspection methods are time-consuming,
require personnel to physically handle components in the station
and requires shutdown of the polishing system. Additionally, the
conventional methods may require partial disassembly of the
polishing station and removal of the carrier head from the station,
which may expose other components within the system to
contamination.
[0007] Therefore, there is a need for a method and apparatus that
facilitates monitoring of the retaining ring without the need to
physically handle the retaining ring or shut down the polishing
system.
SUMMARY OF THE INVENTION
[0008] The invention generally provides a method and apparatus that
facilitates monitoring of a retaining ring within a polishing
system to determine condition of the retaining ring and/or assess
lifetime of the retaining ring. In one embodiment, a method for
monitoring at least one surface of a retaining ring coupled to a
carrier head is provided. The method includes moving the carrier
head adjacent a sensor device disposed in a polishing module,
transmitting energy from the sensor device toward the retaining
ring, receiving energy reflected from the retaining ring, and
determining a condition of the retaining ring based on the received
energy.
[0009] In another embodiment, a method for monitoring at least one
surface of a retaining ring coupled to a carrier head is provided.
The method includes moving the carrier head adjacent a load cup
assembly disposed in a polishing module, the sensor device being
disposed in a body of the load cup assembly, transmitting energy
from the sensor device toward a surface of the retaining ring as
the retaining ring is in the line-of-sight of the sensor device,
receiving energy reflected from the surface, and determining a
thickness of the retaining ring based on the received energy.
[0010] In another embodiment, a method for monitoring at least one
surface of a retaining ring coupled to a carrier head is provided.
The method includes moving the carrier head adjacent a load cup
assembly disposed in a polishing module, the sensor device being
disposed in a body of the load cup assembly, rinsing the retaining
ring, transmitting energy from the sensor device toward a surface
of the retaining ring as the retaining ring is in the line-of-sight
of the sensor device, receiving energy reflected from the surface,
and determining a thickness of the retaining ring based on the
received energy.
[0011] In another embodiment, an apparatus is provided. The
apparatus includes a carrier head movable in a travel path between
at least one polishing station for polishing a substrate as the
substrate is retained in the carrier head and a transfer station
for transferring the substrate to and from the carrier head, the
carrier head having a retaining ring, and a sensor disposed in the
travel path of the carrier head, the sensor operable to provide a
metric indicative of a condition of the retaining ring.
[0012] In another embodiment, a transfer station disposed in a
polishing module for transferring substrates between a substrate
transfer device and at least one carrier head is provided. The
transfer station includes a load cup assembly having a body that is
sized to receive a substrate and at least a portion of a retaining
ring that is coupled to the at least one carrier head, and a sensor
disposed on the body, the sensor operable to provide a metric
indicative of a condition of the retaining ring, wherein the
substrate includes a first radius and the sensor is positioned on
the body at a second radius that is greater than the first
radius.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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.
[0014] FIG. 1 is a plan view of one embodiment of a polishing
system.
[0015] FIG. 2 is a partial cross-sectional view of one embodiment
of a transfer station that may be utilized in the polishing system
of FIG. 1.
[0016] FIG. 3 is a schematic cross-sectional view of another
embodiment of a transfer station that may be utilized with the
polishing system of FIG. 1.
[0017] FIG. 4 is a schematic cross-sectional view of another
embodiment of a transfer station that may be utilized with the
polishing system of FIG. 1.
[0018] FIG. 5A is a partial plan view of one embodiment of a
retaining ring.
[0019] FIG. 5B is a schematic cross-sectional view of another
embodiment of a transfer station that may be utilized with the
polishing system of FIG. 1.
[0020] FIG. 6 is a schematic cross-sectional view of another
embodiment of a transfer station that may be utilized with the
polishing system of FIG. 1.
[0021] FIG. 7 is a flow chart showing one embodiment of a
method.
[0022] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0023] The invention generally provides a method and apparatus that
facilitates monitoring of a retaining ring within a polishing
system to determine wear of the retaining ring and/or assess
lifetime of the retaining ring. An on-tool monitoring device is
described that provides monitoring of the retaining ring without
the need to physically handle the retaining ring or shut down the
polishing system. Additionally, data from the monitoring device may
be provided to a controller and utilized for tuning subsequent
polishing processes.
[0024] FIG. 1 is a plan view of a polishing system 100 having a
polishing module 105 and a substrate transfer device that is
suitable for electrochemical mechanical polishing and/or chemical
mechanical polishing. The polishing module 105 includes a first
polishing station 110A, a second polishing station 110B, and a
third polishing station 110C disposed in an environmentally
controlled enclosure 115. The substrate transfer device, such as a
carousel 125, moves substrates between the polishing stations 110A,
110B and 110C. Any of the polishing stations 110A, 110B, 110C may
perform a planarizing or polishing process to remove material from
a feature side of a substrate to form a planar surface on the
feature side. The module 105 may be part of a larger polishing
system, such as, for example REFLEXION.RTM., REFLEXION.RTM. LK,
REFLEXION.RTM. LK ECMP.TM., MIRRA MESA.RTM., and REFLEXION GT.TM.
polishing systems available from Applied Materials, Inc., located
in Santa Clara, Calif., although other polishing systems may be
utilized. Other polishing modules, including those that use other
types of polishing pads, belts, indexable web-type pads, or a
combination thereof, and those that move a substrate relative to a
polishing surface in a rotational, linear or other planar motion
may also be adapted to benefit from embodiments described
herein.
[0025] In one embodiment, each of the polishing stations 110A-110C
of the polishing module 105 are adapted to perform a conventional
chemical mechanical polishing (CMP) process. Alternatively, the
first polishing station 110A may be configured to perform an
electrochemical mechanical planarization (ECMP) process, while the
second polishing station 110B and the third polishing station 110C
may perform a CMP process. In one embodiment of a process, a
substrate having feature definitions formed therein and covered
with a barrier layer and a conductive material disposed over the
barrier layer may have the conductive material removed in two steps
in the first and second polishing stations 110A, 110B, by a CMP
process, with the barrier layer processed in the third station 110C
by a third CMP process to form a planarized surface on the
substrate.
[0026] In one embodiment, the system 100 includes a module base 118
that supports the polishing stations 110A, 110B and 110C, a
transfer station 120, and the carousel 125. Each of the polishing
stations 110A, 1108, and 110C include a polishing fluid delivery
arm 128 adapted to deliver a polishing fluid to a polishing surface
175 during a polishing process. A plurality of conditioning devices
130 are shown coupled to the module base 118 and are movable in the
direction A in order to selectively place the conditioning device
130 over each of the polishing stations 110A, 110B, and 110C. The
transfer station 120 generally facilitates transfer of a substrate
135 to and from the system 100 via a wet robot 140. The wet robot
140 typically transfers substrates 135 between the transfer station
120 and a factory interface (not shown) that may include a cleaning
module, a metrology device and one or more substrate storage
cassettes. The transfer station 120 comprises a first buffer
station 145, a second buffer station 150, a transfer robot 155, and
a load cup assembly 160. The transfer robot 155 transfers
substrates between the first buffer station 145, the second buffer
station 150 and the load cup assembly 160. The load cup assembly
160 includes a monitoring device 162 that is coupled to a
controller.
[0027] The carousel 125 includes a plurality of arms 170, and each
arm 170 supports a carrier head 165A-165D. Carrier heads 165C and
165D as well as a portion of the two arms 170 are shown in phantom
so that the transfer station 120 and the polishing surface 175 of
the polishing station 110C may be seen. The polishing surface 175
comprises the upper surface of a pad assembly disposed on a
rotatable platen (not shown in this view). Each of the carrier
heads 165A-165D includes an actuator 168. The carousel 125 moves
the carrier heads 165A-165D between the transfer station 120 and
polishing stations 110A, 110B and 110C and the actuator 168 is
adapted to move the carrier heads 165A-165D relative to the
carousel 125. The carousel 125 is indexable such that the carrier
heads 165A-165D may be moved between polishing stations 110A, 110B,
110C and the transfer station 120 in a sequence defined by the
user. Each of the carrier heads 165A-165D retain one substrate 135
during a polishing process on the polishing stations 110A-110C.
Other polishing modules, such as the REFLEXION GT.TM. polishing
system, which includes more than one carrier head per polishing
station, may also be adapted to benefit from embodiments described
herein. Each of the carrier heads 165A-165D are movable in a
longitudinal axis of each arm 170. A polished substrate 135 may be
transferred from each carrier head 165A-165D at the transfer
station 120A. Additionally, an unpolished substrate 135 may be
transferred to each carrier head 165A-165D at the transfer station
120. As shown in reference to carrier head 165D, the carrier head
165D is movable along a longitudinal axis of the arm 170 in a
travel path 164 indicated by dashed lines to allow the carrier head
165D to access the load cup assembly 160 and facilitate transfer of
substrates.
[0028] In one embodiment, the carousel 125 is sequentially advanced
in a counterclockwise direction (direction B) to move the carrier
heads 165A-165D above the polishing stations 110A-110C and the
transfer station 120. During processing, three of the four carrier
heads 165A-165D, having substrates retained therein, are disposed
above the polishing stations 110A, 110B, 110C to perform a
polishing process thereon. The substrates 135 are sequentially
processed by moving the substrate between stations while being
retained in the same carrier head 165A-165D. In one example, three
carrier heads 165A-165C contain substrates and urge the substrates
135 toward the polishing surface 175 of the polishing stations
110A, 110B, and 110C. During polishing, the carrier heads 165A-165C
containing substrates are rotated in a counterclockwise direction
(direction C) while the polishing surfaces 175 are rotated in a
counterclockwise direction (direction D).
[0029] As the three carrier heads, which are shown as carrier heads
165A-165C in this example, are utilized at the stations 110A-110C,
the carrier head 165D is adjacent the transfer station 120 where a
substrate transfer process occurs. The carrier head 165D may be
idle for a time period as the three carrier heads 165A-165C perform
a polishing process. During this time period, the carrier head 165D
is readied for use in the polishing station 110A in a following
cycle at the transfer station 120. The carrier head 165D may be
advanced along the travel path 164 to be proximate the transfer
station 120. While the carrier head 165D is at the transfer station
120, the carrier head 165D may unload a polished substrate 135, be
washed, and receive a new, un-polished substrate 135 for a
polishing process on the polishing station 110A. In one embodiment,
the carrier head 165D is inspected using the monitoring device 162
disposed in the transfer station 120.
[0030] The polishing surface 175 is roughened to facilitate
mechanical removal of material from substrates 135. The polishing
surface 175 of the polishing pad may be a polymer material which
may be solely dielectric to facilitate removal of materials from
substrates 135 during a polishing process. Alternatively, the
polishing surface 175 of the polishing pad may be at least
partially conductive to facilitate electrochemical dissolution of
material from substrates in an electrochemical mechanical polishing
(ECMP) process. Suitable polymeric materials that may be used
include polyurethane, polycarbonate, fluoropolymers, PTFE, PTFA,
polyphenylene sulfide (PPS), or combinations thereof, and other
polishing materials used in polishing substrate surfaces. In one
embodiment, polishing surface 175 of the polishing pad includes a
polymeric material, such as open-pored or closed-pored polyurethane
material typically used in the fabrication of polishing pads for
service in the polishing of semiconductor substrates. In another
embodiment, the polishing surface 175 of the polishing pad may
contain fixed abrasives. A polishing fluid is typically delivered
to the polishing surface 175 of the polishing pad during polishing.
The polishing fluid may be a slurry or an electrolytic fluid
depending on the polishing process and type of polishing pad
used.
[0031] FIG. 2 is a partial cross-sectional view of one embodiment
of the transfer station 120 of FIG. 1. As described above, the
transfer station 120 includes the load cup assembly 160 adjacent
the first buffer station 145. The first buffer station 145 may be
an input or output buffer station that is configured to support a
substrate 135. The transfer robot 155 transfers substrates 135
between the first buffer station 145 and the load cup assembly 160
facilitating transfer of substrates to the carrier head 165D.
[0032] In one embodiment, the first buffer station 145 supports a
polished substrate 135 to allow the wet robot 140 (FIG. 1) to
transfer the substrate 135 to a factory interface for subsequent
polishing and/or storage. In another embodiment, the first buffer
station 145 supports an un-polished substrate 135 to allow the
carrier head 165D to receive the substrate 135 for polishing on the
polishing station 110A. In one embodiment, the transfer robot 155
is configured to transfer substrates 135 between the first buffer
station 145 and the load cup assembly 160 to allow the carrier head
165D to receive a substrate 135 as shown in phantom in FIG. 2.
[0033] The carrier head 165D is coupled to a shaft 200, which is
coupled to a motor 215 configured to move the carrier head 165D
laterally in a linear motion (X and/or Y direction) relative to the
arm 170. The carrier head 165D also includes an actuator or motor
210 to lift or lower the carrier head 165D in the Z direction
relative to arm 170. The carrier head 165D is also coupled to a
rotary actuator or motor 220 that is adapted to rotate the carrier
head 165D about a rotational axis relative to the arm 170. The
motors 210, 215 and 220 disposed on the carrier head 165D are also
configured to provide movement of the carrier head 165D relative to
the polishing surface 175 (FIG. 1) of a polishing pad. In one
embodiment, the motors 210, 215 and 220 are configured to rotate
the carrier head 165D relative to a rotating polishing surface 175
as well as provide a down-force to urge the substrate 135 retained
therein against the polishing surface 175 of a polishing pad during
processing. The carrier head 165D construction and operation
depicted in FIG. 2 is representative of the carrier heads 165A-165C
of FIG. 1 and carrier heads 165A-165C will not be described further
for brevity.
[0034] The carrier head 165D includes a body 225 circumscribed by a
retaining ring 230. The carrier head 165D also contains one or more
bladders 235A, 235B that are adjacent a flexible membrane 240. The
flexible membrane 240 contacts a backside of the substrate 135 when
the substrate 135 is retained in the carrier head 165D. The
bladders 235A and 235B are coupled to a first variable pressure
source 245A that selectively delivers a fluid to the bladders 235A
and 235B to apply force to the flexible membrane 240. In one
embodiment, the bladder 235A applies force to an outer zone of the
flexible membrane 240 while the bladder 235B applies force to a
central zone of the flexible membrane 240. Forces applied to the
flexible membrane 240 from the bladders 235A and 235B are
transmitted to portions of the substrate 135 and may be used to
urge portions of the substrate 135 toward the polishing surface of
a polishing pad (not shown). The first variable pressure source
245A is configured to deliver fluids to each of the bladders 235A
and 235B independently in order to control forces to discrete
regions of the substrate 135 through the flexible membrane 240.
Additionally, vacuum ports (not shown) may be provided in the
carrier head 135 to apply suction to the backside of the substrate
135 facilitating retention of the substrate 135 in the carrier head
165D. Examples of a carrier head 165D that may be utilized include
the TITAN HEAD.TM., the TITAN CONTOUR.TM. and the TITAN
PROFILER.TM. carrier heads, which are available from Applied
Materials, Inc. of Santa Clara, Calif.
[0035] In one embodiment, the retaining ring 230 is coupled to the
body 225 by an actuator 232. The actuator 232 is controlled by a
second variable pressure source 245B. The second variable pressure
source 245B provides or removes fluid from the actuator 232 which
causes the retaining ring 230 to move relative to the body 225 of
the carrier head 165D in at least the Z direction. The second
variable pressure source 245B is adapted to provide the Z
directional movement of the retaining ring 230 independent of
movement provided by the motor 210. The second variable pressure
source 245B may provide movement of the retaining ring 230 by
applying negative pressure or positive pressure to the actuator 232
and/or the retaining ring 230. In one aspect, pressure is applied
to the retaining ring 230 to urge the retaining ring 230 toward the
polishing surface 175 (FIG. 1) of a polishing pad (not shown)
during a polishing process. Each of the first variable pressure
source 245A and the second variable pressure source 245B may be
coupled with the controller to facilitate execution of a polish
recipe that automatically controls pressures to zones of the
substrate 135 during a polishing process.
[0036] The retaining ring 230 contacts the polishing surface 175
during the polishing process. The retaining ring 230 may also
facilitate transportation of the polishing fluid on the polishing
surface 175 and create heat due to friction from contact with the
polishing surface 175. The fluid transportation and generated heat
may be utilized to advantage during a polishing process. The
contact with the polishing surface 175 causes the retaining ring
230 to wear. The wear of surfaces of the retaining ring 230 affect
the polishing process and the retaining ring 230 will eventually
require replacement. Thus, thickness of the retaining ring 230 must
be periodically assessed to determine wear and replacement
intervals.
[0037] In one embodiment, the surfaces of the retaining ring 230
are monitored by the monitoring device 162 disposed in the load cup
assembly 160. Surfaces of the retaining ring 230 may be sensed as
the carrier head 165D is adjacent the load cup assembly 160 and
data representative of wear of the retaining ring 230 may be sent
to a controller. The controller may be in communication with a
monitor to display the data for a user. The data from the
monitoring device 162 is used to predict and/or ascertain a
condition of the retaining ring 230 that is utilized to determine
lifetime and replacement of the retaining ring 230. In one
embodiment, the data is indicative of the thickness of the
retaining ring 230. Alternatively or additionally, the controller
may be a system controller that may analyze the data and implement
corrective measures in a process recipe to compensate for wear of
the retaining ring 230 in the polishing process. Thus, data from
the monitoring device 162 is used to determine lifetime and
replacement of the retaining ring 230 and may be additionally
utilized as a control knob to tune the polishing process. Moreover,
in systems having multiple carrier heads with retaining rings, the
data from the monitoring device 162 may be utilized to adjust the
process recipe of individual retaining rings independently from
other retaining rings on other carrier heads in the system. For
example, as individual retaining rings may wear at different rates,
a process recipe for one retaining ring on one carrier head may be
adjusted while other process recipes on other retaining rings on
remaining carrier heads may remain the same.
[0038] FIG. 3 is a schematic cross-sectional view of another
embodiment of a transfer station 120 that may be utilized with the
polishing system 100 of FIG. 1. The transfer station 120 includes a
load cup assembly 160 and a carrier head 165D is disposed adjacent
the load cup assembly 160. In this embodiment, the load cup
assembly 160 is configured as a wash station 300 adapted to clean
the carrier head 165D when the carrier head 165D is not utilized
for polishing on the polishing stations 110A-110C of FIG. 1.
[0039] In one embodiment, the load cup assembly 160 includes a body
305 having a reference cone or ring 307 that is coupled to a base
309. The ring 307 and the base 309 are movable relative to a module
base 118 by a first actuator 310A. The first actuator 310A may be
utilized to move the body 305 in at least a linear direction (Z
direction) relative to the module base 118. The load cup assembly
160 also includes a pedestal 320 adapted to support a substrate 135
(shown in phantom). The pedestal 320 is coupled to a second
actuator 310B adapted to raise and lower a support surface 321 of
the pedestal 320. The second actuator 310B facilitates transfer of
the substrate 135 to or from the carrier head 165D by moving the
support surface 321 in the Z direction relative to the body
305.
[0040] The body 305 also includes a plurality of nozzles 315
utilized to wash the carrier head 165D when a substrate is not
present on the pedestal 320. The nozzles 315 are in fluid
communication with a pressurized fluid supply 330. The pressurized
fluid supply 330 contains a fluid, such as deionized water, that is
applied through nozzles 315 to clean the carrier head 165D. In one
embodiment, the support surface 321 of the pedestal 320 is
configured as a ring having multiple open areas to allow cleaning
fluid from the nozzles 315 to impinge the carrier head 165D. The
cleaning fluid washes polishing liquid and other debris from the
polishing process that may be retained on the carrier head 165D.
The wash station 300 also contains an opening 325 formed in the
base 309 that is adapted as a drain to selectively remove fluid and
polishing debris dislodged from the carrier head 165D.
[0041] In this embodiment, the wash station 300 includes a
monitoring device 162 comprising a sensor 335 coupled to a
controller. The sensor 335 is adapted to measure a thickness T of
the retaining ring 230. In one embodiment, the sensor 335 is an
ultrasonic sensor. The sensor 335 may be coupled to or embedded
within the body 305 to transmit and receive sound waves. The sound
waves are transmitted to the controller to provide a metric
indicative of the thickness T of the retaining ring 230. In one
embodiment, the retaining ring 230 comprises two annular portions,
such as an upper portion 355A and a lower portion 355B. In one
embodiment, the upper portion 355A and lower portion 355B may
contain a material which is chemically inert in a CMP process, such
as metal material, a ceramic material, or a plastic material. In
one embodiment, the lower portion 355B contains a plastic, e.g.,
polyphenylene sulfide (PPS), polyetheretherketone (PEEK), a carbon
containing PEEK material, a TEFLON.RTM. containing PEEK material,
or a composite material. The upper portion 355A may contain a
material that is more rigid or dense than the lower portion 355B.
In one embodiment, the upper portion 355A contains stainless steel,
aluminum, molybdenum or ceramic materials.
[0042] In one example of operation, the sensor 335 is mounted on an
active surface 340 of a land area 345 of the body 305. The land
area 345 may be defined as a region of a bottom surface of the ring
307 where the lower portion 355B of the retaining ring 230 contacts
a surface of the ring 307. The active surface 340 may be flush with
the surface of the ring 307 at the land area 345 where the
retaining ring 230 is positioned. In one embodiment, sound waves
are transmitted to or through the lower portion 355B of the
retaining ring 230 and are reflected from the upper portion 355A.
The reflected signals are transmitted to the controller and
utilized to determine thickness T of the lower portion 355B of the
retaining ring 230. The change in thickness T over time is
indicative of the wear of the retaining ring 230.
[0043] FIG. 4 is a schematic cross-sectional view of another
embodiment of a transfer station 120 that may be utilized with the
polishing system 100 of FIG. 1. In this embodiment, the load cup
assembly 160 is configured as a wash station 400 that may be
substantially similar to the embodiment shown in FIG. 3. Elements
of the transfer station 120 that are similar to the transfer
station 120 of FIG. 3 will not be repeated for brevity.
[0044] In this embodiment, the monitoring device 162 comprises a
sensor 335 which is an eddy current sensor adapted to measure a
thickness T of the lower portion 355B. In this embodiment, a
contact surface 405 of the lower portion 355B is in contact with
the active surface 340 of the ring 307. In other embodiments, the
sensor 335 may be utilized as the retaining ring 230 is spaced away
from the ring 307. In one aspect, the sensor 335 adapted as an eddy
current sensor may be utilized to measure the displacement between
the active surface 340 and the contact surface 405 of the upper
portion 355A of the retaining ring 230. The displacement
corresponds to a change in thickness of at least the lower portion
355B of the retaining ring 230. The displacement may be determined
when the lower portion 355B of the retaining ring 230 is in contact
with the active surface 340 or when the lower portion 355B is held
a constant distance from the active surface 340.
[0045] FIG. 5A is a partial plan view of one embodiment of a
retaining ring 230 having one or more grooves 500. Each of the one
or more grooves 500 are formed in the retaining ring 230 at a
desired depth between a contact surface 405 of the retaining ring
230 and a bottom 505 of the groove 500. Each of the grooves 500
disposed on the retaining ring 230 may be utilized to facilitate
polishing by enhancing transportation of polishing fluid during a
polishing process.
[0046] FIG. 5B is a schematic cross-sectional view of another
embodiment of a transfer station 120 that may be utilized with the
polishing system 100 of FIG. 1 and the retaining ring 230 shown in
FIG. 5A. The retaining ring 230 comprises a one or more grooves 500
having a depth D' defined by a contact surface 405 and a bottom
505. The change in the depth D' of the groove 500 corresponds to
the change in thickness of the retaining ring 230. In one
embodiment, the sensor 335 may be coupled to or embedded within the
ring 307. The sensor 335 may be an optical sensor, an eddy current
sensor, an ultrasonic sensor, or other suitable sensing device. In
one embodiment, the sensor 335 is an ultrasonic sensor configured
to transmit and receive sound waves illustrated as signals 510 that
impinge the contact surface 405. The sound waves are transmitted to
the controller to provide a metric indicative of the depth D' of
the groove 500, and, accordingly the thickness of the retaining
ring 230, whether the retaining ring 230 is sensed dry or wet.
Thus, the depth of the groove 500 measured between the contact
surface 405 and the bottom 505 to determine wear without physical
contact between the retaining ring 230 and other portions of the
load cup assembly 160. The carrier head 165D may be rotated at a
predetermined rotational velocity to provide sensing at multiple
locations of the retaining ring 230. Thus, multiple grooves 500 may
be monitored. Alternatively, the carrier head 165D may be
motionless to allow sensing of a single groove 500. In another
embodiment, a controlled air column or liquid column may be
utilized to surround the signals 510 and control the interface
between the retaining ring 230 and the sensor 335. For example, a
bubbler (not shown) may be utilized to form a cylindrical air
column that surrounds the path of the signals 510.
[0047] In one embodiment, the position of the monitoring device 162
is outside of the area of the substrate 135 to prevent any
inadvertent sensing of the substrate 135 or portions of the carrier
head 165D that are not of interest. For example, the substrate 135
includes a first radius R.sub.1 in the case of a circular
substrate. In one embodiment, the first radius R.sub.1 includes a
radius of about 100 mm for a 200 mm diameter substrate. In another
embodiment, the first radius R.sub.1 includes a radius of about 150
mm for a 300 mm diameter substrate. In one embodiment, the
monitoring device 162 is positioned at a second radius R.sub.2 that
is greater than or outside of the first radius R.sub.1. The second
radius R.sub.2 may be greater than about 100 mm, such as about 105
mm to about 120 mm from a centerline C' for a 200 mm substrate. In
another example, the second radius R.sub.2 may be greater than
about 150 mm, such as about 155 mm to about 170 mm from the
centerline C' for a 300 mm substrate. The centerline C' may be a
geometric center of the load cup assembly 160 and/or a center of
the carrier head 165D. Thus, the positioning of the monitoring
device 162 prevents any inadvertent sensing of the substrate 135 or
portions of the carrier head 165D that are not of interest.
[0048] FIG. 6 is a schematic cross-sectional view of another
embodiment of a transfer station 120 that may be utilized with the
polishing system 100 of FIG. 1. In this embodiment, the load cup
assembly 160 is similar to the embodiment shown in FIGS. 3, 4 and
5. Elements of the transfer station 120 that are similar to the
transfer station 120 of FIGS. 3-5 will not be repeated for brevity.
In one embodiment, the retaining ring 230 comprises a one or more
grooves 500 similar to the embodiment of the retaining ring 230 of
FIG. 5.
[0049] In this embodiment, the monitoring device 162 comprises a
sensor 335 that is an ultrasonic sensor although an optical sensor,
an eddy current sensor, or other suitable sensing device may be
utilized. In one embodiment, the sensor 335 may be utilized when
the retaining ring 230 is in the line-of-sight or field of view of
the sensor 335. In other embodiments, the sensor 335 may be
utilized when the retaining ring 230 is at least partially disposed
in the load cup assembly 160. In one aspect, the sensor 335
includes a tubular conduit 600 disposed adjacent the sensor 335.
The tubular conduit 600 is coupled to a fluid supply 605 that
delivers a fluid, such as deionized water, to surround the signal
path of the sensor 335. The fluid is utilized to eliminate
uncontrolled air that may affect the signals from the sensor 335.
In one embodiment, the contact surface 405 of the retaining ring
230 is in direct contact with the active surface 340 of the ring
307. In another embodiment, the tubular conduit 600 is coupled to
an actuator 610 that allows the tubular conduit 600 to extend and
retract relative to an active surface 340 of the ring 307. The
tubular conduit 600 may be actuated toward the contact surface 405
as shown in phantom to a position adjacent the contact surface 405
of the retaining ring 230 when the carrier head 165D is not in
contact with the ring 307. The tubular conduit 600 may contain at
least a portion of the sensor 335 which moves with the tubular
conduit 600 toward the contact surface 405 of the retaining ring
230. The actuator 610 may also retract the tubular conduit 600 when
the sensor 335 is not needed.
[0050] FIG. 7 is a flow chart showing one embodiment of a method
700. At 705, a carrier head 165D having a retaining ring 230 is
moved adjacent a monitoring device 162. In one embodiment, the
monitoring device 162 is disposed on a load cup assembly 160 within
a polishing module 105. In other embodiments, the monitoring device
162 may be adjacent the transfer station 120 or in a travel path of
the carrier head 165D adjacent the transfer station 120 or other
position on the polishing module 105. The monitoring device 162
includes a sensor 335 and energy is transmitted from the sensor 335
as shown at 710. The energy may be ultrasonic waves, optical waves
or magnetic fields or magnetic signals. At 715, energy reflected
from the retaining ring 230 is received by the sensor 335. The
reflected energy may be from an internal or external surface or
surfaces of the retaining ring 230. At 720, a condition of the
retaining ring is determined based on the received energy. The
reflected signals may be provided to a controller to obtain a
metric indicative of the condition of the retaining ring 230, for
example, a thickness of the retaining ring 230 or portion thereof,
or a depth of a groove 500 of the retaining ring 230 that may be
associated with a thickness of the retaining ring 230. The data may
be utilized to determine replacement intervals for the retaining
ring 230 and/or tuning of variables in subsequent polishing
processes.
[0051] Embodiments described herein provide a method and apparatus
for monitoring the condition of a surface of a retaining ring 230
disposed on a carrier head in a polishing station, such as carrier
heads 165A-165D as described herein. A monitoring device 162 is
described that may be mounted on-tool and, in one embodiment,
senses the retaining ring 230 condition between polishing cycles.
The sensing of the retaining ring 230 may be set by a user at
pre-defined intervals as part of routine monitoring or at chosen
intervals based on user preferences. Data from the monitoring
device 162 is provided to a controller that may be used to monitor
wear of the retaining ring 230, determine lifetime of the retaining
ring 230 and/or determine replacement intervals for the retaining
ring 230. In one aspect, data from the monitoring device 162 could
be used to predict the lifetime of the retaining ring 230 and
facilitate replacement of the retaining ring 230 at the end of the
useful lifetime. In another aspect, data from the monitoring device
162 could be used to predict the lifetime and facilitate a
convenient replacement interval even if the retaining ring 230 is
not completely worn out.
[0052] Embodiments of the monitoring device 162 as described herein
minimize or eliminate physical handling and/or mechanical contact
with the carrier heads 165A-165D and retaining ring 230. For
example, mechanical measuring devices such as calipers require
contact with the retaining ring 230. The contact with the
mechanical measuring devices may damage the retaining ring 230
during measurement which, in turn, may damage the polishing surface
175 during processing. The measurements may be taken within the
tool and there is no need for shutting down the polishing system.
Additionally, there is no need to completely dry the retaining ring
230 for measurements. The monitoring device 162 is mounted on-tool
such that the environment contained in the environmentally
controlled enclosure 115 (FIG. 1). Thus, the monitoring device 162
as described herein provides monitoring of the retaining ring 230
with less potentially damaging handling or contact with the carrier
heads 165A-165D and/or breaching of the environment of the
polishing module 105. The method and apparatus also eliminates or
minimizes visual inspections, which are time consuming and may be
inaccurate. Additionally, throughput may be maximized as the
polishing system will not require shut downs for measurement and/or
observation of the retaining ring 230.
[0053] Additionally, the retaining ring 230 wear data may be used
as a control variable during a polishing process. For example, if
the retaining ring 230 contains grooves 500, and the grooves 500
show a predetermined amount of wear, one or more polishing
parameters may be adjusted to compensate for any retaining ring 230
thickness effects in polishing uniformity. In one example,
polishing parameters such as rotational velocity and down-force of
the carrier head 165A-165D may be adjusted to account for wear of
the retaining ring 230 and mimic the polishing effects of a
less-worn retaining ring 230. In one aspect, the rotational
velocity of the carrier head 165A-165D may be accelerated to
facilitate transportation of the polishing fluid and create heat on
the polishing surface 175 that is substantially equivalent to the
effect of a less-worn retaining ring 230.
[0054] In another example, the retaining ring 230 wear data may be
utilized to minimize within wafer non-uniformity during the
lifetime of the retaining ring 230. Wear data of the retaining ring
230 may be utilized with an automated process control system that
is coupled to the bladders 235A and 235B in multi-zone carrier
heads, such as the carrier head 165D shown in FIG. 2. Additionally,
the automated process control system may be in communication with
the actuator 232 on the carrier head 165D shown in FIG. 2. In one
aspect, the pressure applied to outer zones (bladder 235A) and/or
the retaining ring 230 by the actuator 232 may be modified in
response to changes in the thickness of the retaining ring 230.
Changes to the pressure applied to the substrate by the bladders
235A and 235B and/or pressures applied to the retaining ring 230
may be made in real-time based on the thickness data of the
retaining ring 230. Thus, removal rate, removal profile and/or
topography of the substrates being polished may be controlled by
manipulating the polishing parameters based on the wear of the
retaining ring 230. Additionally, as the polishing parameters may
be tuned for each carrier head 165A-165D, carrier head to carrier
head variation may be minimized.
[0055] Embodiments described herein provide methods and apparatus
that facilitate monitoring of a retaining ring within a polishing
system to determine condition of the retaining ring and/or assess
lifetime of the retaining ring. In one embodiment, an apparatus is
provided. The apparatus includes a carrier head movable in a travel
path between at least one polishing station for polishing a
substrate as the substrate is retained in the carrier head and a
transfer station for transferring the substrate to and from the
carrier head, the carrier head having a retaining ring, and a
sensor disposed in the travel path of the carrier head, the sensor
operable to provide a metric indicative of a condition of the
retaining ring.
[0056] In another embodiment, a transfer station disposed in a
polishing module for transferring substrates between a substrate
transfer device and at least one carrier head is provided. The
transfer station includes a load cup assembly having a body that is
sized to receive a substrate and at least a portion of a retaining
ring that is coupled to the at least one carrier head, and a sensor
disposed on the body, the sensor operable to provide a metric
indicative of a condition of the retaining ring, wherein the
substrate includes a first radius and the sensor is positioned on
the body at a second radius that is greater than the first
radius.
[0057] While the foregoing is directed to embodiments of the
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof.
* * * * *