U.S. patent application number 14/200149 was filed with the patent office on 2014-09-18 for pad conditioning process control using laser conditioning.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Rajeev BAJAJ, Thomas BREZOCZKY, Mario CORNEJO, Thomas H. OSTERHELD, Rixin PENG, Fred REDEKER.
Application Number | 20140273752 14/200149 |
Document ID | / |
Family ID | 51529184 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140273752 |
Kind Code |
A1 |
BAJAJ; Rajeev ; et
al. |
September 18, 2014 |
PAD CONDITIONING PROCESS CONTROL USING LASER CONDITIONING
Abstract
A method and apparatus for conditioning a polishing pad used in
a substrate polishing process. In one embodiment, a method for
conditioning a polishing pad utilized to polish a substrate is
provided. The method includes providing relative motion between an
optical device and a polishing pad having a polishing medium
disposed thereon, and scanning a processing surface of the
polishing pad with a laser beam to condition the processing
surface, wherein the laser beam has a wavelength that is
substantially transparent to the polishing medium, but is reactive
with the material of the polishing pad.
Inventors: |
BAJAJ; Rajeev; (Fremont,
CA) ; PENG; Rixin; (Santa Clara, CA) ;
CORNEJO; Mario; (San Jose, CA) ; BREZOCZKY;
Thomas; (Los Gatos, CA) ; REDEKER; Fred;
(Fremont, CA) ; OSTERHELD; Thomas H.; (Mountain
View, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
51529184 |
Appl. No.: |
14/200149 |
Filed: |
March 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61780155 |
Mar 13, 2013 |
|
|
|
61935747 |
Feb 4, 2014 |
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Current U.S.
Class: |
451/6 ;
451/56 |
Current CPC
Class: |
B24B 53/017 20130101;
B24B 37/042 20130101; B24B 49/18 20130101 |
Class at
Publication: |
451/6 ;
451/56 |
International
Class: |
B24B 53/017 20060101
B24B053/017; B24B 37/04 20060101 B24B037/04 |
Claims
1. A method for conditioning a polishing pad utilized to polish a
substrate, the method comprising: providing relative motion between
an optical device and a polishing pad having a polishing medium
disposed thereon; and scanning a processing surface of the
polishing pad with a laser beam to form a groove pattern on the
processing surface, wherein the laser beam has a wavelength that is
substantially transparent to the polishing medium, but is reactive
with the material of the polishing pad.
2. The method of claim 1, further comprising: monitoring a state of
the processing surface during polishing of a substrate.
3. The method of claim 2, wherein the state of the processing
surface is monitored by at least one sensor.
4. The method of claim 3, wherein the at least one sensor comprises
an optical sensor, a capacitive sensor, a rotational sensor, a
shear force sensors an eddy current sensor, and combinations
thereof.
5. The method of claim 3, further comprising: adjusting
conditioning parameters in response to a metric provided by the at
least one sensor.
6. The method of claim 5, wherein the adjusting conditioning
parameters includes adjusting a spot size of the beam.
7. The method of claim 5, wherein the adjusting conditioning
parameters includes adjusting a pulse frequency, a number of
pulses, and/or a pulse length of the beam.
8. The method of claim 5, wherein the adjusting conditioning
parameters includes adjusting an angle of incidence of the beam
relative to the processing surface.
9. The method of claim 5, wherein the adjusting conditioning
parameters includes adjusting an output power of the laser
device.
10. A method for polishing a substrate, comprising: urging a
substrate against a processing surface of a polishing pad while
providing relative movement between the substrate and the polishing
pad; providing a polishing medium to the processing surface;
monitoring a state of the processing surface during the relative
movement; and conditioning the processing surface with an optical
device comprising a laser emitter adapted to emit a beam having a
wavelength range that is substantially non-reactive with the
polishing medium, but is reactive with the polishing pad.
11. The method of claim 10, further comprising: adjusting
conditioning parameters based on a metric provided by one or more
sensors.
12. The method of claim 11, wherein the adjusting conditioning
parameters includes adjusting a spot size of the beam.
13. The method of claim 11, wherein the adjusting conditioning
parameters includes adjusting a pulse frequency, a number of
pulses, and/or a pulse length of the beam.
14. The method of claim 11, wherein the adjusting conditioning
parameters includes adjusting an angle of incidence of the beam
relative to the processing surface.
15. The method of claim 11, wherein the adjusting conditioning
parameters includes adjusting an output power of the laser
device.
16. A method for conditioning a polishing pad, comprising: scanning
a beam relative to a processing surface of the polishing pad having
water disposed thereon, the beam having a wavelength range that is
non-reactive with the water, but is reactive with the polishing
pad; and conditioning the processing surface of the polishing
pad.
17. The method of claim 16, further comprising: monitoring a
topography of the processing surface.
18. The method of claim 17, further comprising: adjusting
conditioning parameters in response to a metric provided by one or
more sensors.
19. The method of claim 18, wherein the adjusting conditioning
parameters includes adjusting a spot size of the beam.
20. The method of claim 18, wherein the adjusting conditioning
parameters includes adjusting a pulse frequency, a number of
pulses, and/or a pulse length of the beam.
21. The method of claim 18, wherein the adjusting conditioning
parameters includes adjusting an angle of incidence of the beam
relative to the processing surface.
22. The method of claim 18, wherein the adjusting conditioning
parameters includes adjusting an output power of the laser device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Patent Application
Ser. No. 61/780,155 (Attorney Docket No. 020572USAL) filed Mar. 13,
2013, and U.S. Patent Application Ser. No. 61/935,747 (Attorney
Docket No. 021012USAL) filed Feb. 4, 2014. Both of the
aforementioned patent applications are hereby incorporated by
reference herein.
BACKGROUND
[0002] 1. Field
[0003] Embodiments of the present invention generally relate to
control methods and apparatus for conditioning a substrate
polishing pad using optical conditioning devices, such as laser
conditioning devices.
[0004] 2. Description of the Related Art
[0005] In the fabrication of integrated circuits and other
electronic devices on substrates, multiple layers of conductive,
semiconductive, and dielectric materials are deposited on or
removed from a feature side, i.e., a deposit receiving surface, of
a substrate. As layers of materials are sequentially deposited and
removed, the feature side of the substrate may become non-planar
and require planarization and/or polishing. Planarization and
polishing are procedures where previously deposited material is
removed from the feature side of the substrate to form a generally
even, planar or level surface. The procedures are useful in
removing undesired surface topography and surface defects, such as
rough surfaces, agglomerated materials, crystal lattice damage, and
scratches. The procedures are also useful in forming features on a
substrate by removing excess deposited material used to fill the
features and to provide an even or level surface for subsequent
deposition and processing.
[0006] During polishing processes, the polishing surface of the pad
that is in contact with the feature side of the substrate
experiences a deformation. The deformation includes smoothing of
the polishing surface and/or unevenness in the plane of the
polishing surface, as well as clogging or blockage of pores in the
polishing surface that may lessen the ability of the pad to
properly and efficiently remove material from the substrate.
Periodic conditioning of the polishing surface is required to
maintain a consistent roughness, porosity and/or a generally flat
profile across the polishing surface.
[0007] One method to condition the polishing surface utilizes an
abrasive conditioning disk that is urged against the polishing
surface while being rotated and/or swept across the majority of the
polishing surface. The abrasive portion of the conditioning disk,
which may be diamond particles or other hard materials, typically
cut into the pad surface, which forms grooves in, and otherwise
roughens, the polishing surface. However, while the rotation and/or
downforce applied to the conditioning disk is controlled, the
abrasive portion may not cut into the polishing surface evenly,
which creates a difference in roughness across the polishing
surface. Additionally, as the cutting action is not readily
controlled, the pad lifetime may be shortened. Further, the cutting
action of these conditioning devices and systems sometimes produce
large asperities in the polishing surface. While the asperities are
beneficial in the polishing process, the asperities may break loose
during polishing, which creates debris that may contribute to
defects in the substrate.
[0008] Therefore, there is a need for an improved pad conditioning
process and associated control methods.
SUMMARY
[0009] A method and apparatus for conditioning a polishing pad
utilized in a polishing process is provided. In one embodiment, a
method for conditioning a polishing pad utilized to polish a
substrate is provided. The method includes providing relative
motion between an optical device and a polishing pad having a
polishing medium disposed thereon, and scanning a processing
surface of the polishing pad with a laser beam to condition the
processing surface, wherein the laser beam has a wavelength that is
substantially transparent to the polishing medium, but is reactive
with the material of the polishing pad.
[0010] In another embodiment, a method for polishing a substrate is
provided. The method includes urging a substrate against a
processing surface of a polishing pad while providing relative
movement between the substrate and the polishing pad, providing a
polishing medium to the processing surface, monitoring a state of
the processing surface during the relative movement, and
conditioning the processing surface with an optical device
comprising a laser emitter adapted to emit a beam having a
wavelength range that is substantially non-reactive with the
polishing medium, but is reactive with the polishing pad.
[0011] In another embodiment, a method for conditioning a polishing
pad is provided. The method includes scanning a beam relative to a
processing surface of the polishing pad having water disposed
thereon, the beam having a wavelength range that is non-reactive
with the water, but is reactive with the polishing pad, the beam
having a wavelength range that is substantially non-reactive with
the water, but is reactive with the polishing pad, and conditioning
the processing surface of the polishing pad.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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.
[0013] FIG. 1 is a partial sectional view of one embodiment of a
processing station that is configured to perform a polishing
process.
[0014] FIG. 2 is a top plan view of the processing station of FIG.
1.
[0015] FIG. 3 is a cross-sectional view of a portion of a polishing
pad.
[0016] FIG. 4 is a graph showing absorption coefficients for
various wavelengths of light.
[0017] FIG. 5 is a partial sectional view of the processing station
of FIG. 1 showing a monitoring/feedback system.
[0018] FIG. 6 is a top plan view of a polishing pad showing another
embodiment of a patterned processing surface.
[0019] FIGS. 7A-7C are schematic top views of mark arrays that may
be formed on a polishing pad.
[0020] FIGS. 8A-8C are schematic cross-sectional views of mark
arrays that may be formed on a polishing pad.
[0021] FIGS. 9A-9D are schematic top views of various embodiments
of marks that may be formed in or on a polishing pad.
[0022] FIGS. 10A and 10B are schematic top views of a polishing pad
showing embodiments of a portion of a patterned processing
surface.
[0023] 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
[0024] FIG. 1 is a partial sectional view of one embodiment of a
processing station 100 that is configured to perform a polishing
process, such as a chemical mechanical polishing (CMP) process or
an electrochemical mechanical polishing (ECMP) process. The
processing station 100 may be a stand-alone unit or part of a
larger processing system. Examples of a larger processing system
that the processing station 100 may be utilized with include
REFLEXION.RTM., REFLEXION.RTM. GT, REFLEXION.RTM. LK,
REFLEXION.RTM. LK ECMP.TM., MIRRA MESA.RTM. polishing systems
available from Applied Materials, Inc., located in Santa Clara,
Calif., although other polishing systems may be utilized, including
those from other manufacturers. Other polishing modules, including
those that use other types of processing 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] The processing station 100 includes a platen 102 rotatably
supported on a base 104. The platen 102 is operably coupled to a
drive motor 106 adapted to rotate the platen 102 about a rotational
axis A. The platen 102 supports a polishing pad 108 having a body
110. The body 110 of the polishing pad 108 may be a commercially
available pad material, such as polymer based pad materials
typically utilized in CMP processes, or other polishing article
suitable for practicing the invention. The polymer material may be
a polyurethane, a polycarbonate, fluoropolymers, PTFE, PTFA,
polyphenylene sulfide (PPS), or combinations thereof. The body 110
may further comprise open or closed cell foamed polymers,
elastomers, felt, impregnated felt, plastics, and like materials
compatible with the processing chemistries. While the body 110 may
be dielectric, it is contemplated that polishing pads having at
least partially conductive polishing surfaces may also benefit from
the invention.
[0026] The polishing pad 108 comprises a processing surface 112
which includes a naphthat may include microscopic pore structures.
The nap and/or pore structures effect material removal from the
feature side of a substrate. Attributes of the processing surface
112, such as polishing compound retention, polishing or removal
activity, and material and fluid transportation, affect the removal
rate. In order to facilitate optimal removal of material from the
substrate, the processing surface 112 must be periodically
conditioned to roughen and/or fully and evenly open the nap or pore
structures. When the processing surface 112 is conditioned in this
manner, the processing surface 112 provides a uniform and stable
removal rate. The roughened processing surface 112 facilitates
removal by enhancing pad surface wetability and dispersing
polishing compounds, such as, for example, abrasive particles
supplied from a polishing compound.
[0027] A carrier head 114 is disposed above the processing surface
112 of the polishing pad 108. The carrier head 114 retains a
substrate 116 and controllably urges the substrate 116 against the
processing surface 112 (along the Z axis) of the polishing pad 108
during processing. The carrier head 114 is mounted to a support
member 118 that supports the carrier head 114 and facilitates
movement of the carrier head 114 relative to the polishing pad 108.
The support member 118 may be coupled to the base 104 or mounted
above the processing station 100 in a manner that suspends the
carrier head 114 above the polishing pad 108. In one embodiment,
the support member 118 is a circular track that is mounted above
the processing station 100. In another embodiment, the support
member 118 is a support arm that couples to a central support
member (not shown) that may rotate the support member 118 relative
to the processing station 100.
[0028] The carrier head 114 is coupled to a drive system 120 that
provides at least rotational movement of the carrier head 114 about
a rotational axis B. The drive system 120 may additionally be
configured to move the carrier head 114 along the support member
118 laterally (X and/or Y axes) relative to the polishing pad 108.
In one embodiment, the drive system 120 moves the carrier head 114
vertically (Z axis) relative to the polishing pad 108 in addition
to lateral movement. For example, the drive system 120 may be
utilized to urge the substrate 116 against the polishing pad 108 in
addition to providing rotational and/or lateral movement of the
substrate 116 relative to the polishing pad 108. The lateral
movement of the carrier head 114 may be a linear, or an arcing or
sweeping motion (shown as 215 in FIG. 2).
[0029] A fluid applicator 122 is shown positioned over the
processing surface 112 of the polishing pad 108. The fluid
applicator 122 is adapted to provide polishing medium, such as
polishing fluids or a polishing compound, to at least a portion of
the radius of the polishing pad 108. The polishing fluid or
polishing compound may be a chemical solution, a slurry, a cleaning
solution, or a combination thereof, consisting primarily of water
(e.g., about 70% to about 99%, or greater, content of de-ionized
water (DIW)). For example, the medium may be an abrasive containing
or abrasive free polishing compound adapted to aid in removal of
material from the feature side of the substrate 116. Reductants and
oxidizing agents, such as hydrogen peroxide, may also be added to
the medium. Alternatively, the medium may be a rinsing agent, such
as DIW, which is used to rinse or flush polishing byproducts from
the polishing material of the polishing pad 108.
[0030] FIG. 1 also shows two distinct embodiments of a conditioning
device, shown as a first conditioner device 124A and a second
conditioner device 124B. One or both of the first conditioner
device 124A and the second conditioner device 124B may be utilized
with the processing station 100.
[0031] The first conditioner device 124A generally includes a
conditioner head 126 coupled to the base 104 of the processing
station 100. The conditioner head 126 may comprise an optical
device 128. The optical device 128 may be a laser emitter, a lens,
a mirror, or other suitable device for emitting, transmitting, or
directing a light beam 140 toward the processing surface 112 of the
polishing pad 108. In one embodiment, the optical device 128
comprises a laser emitter 129. The laser emitter 129 may
alternatively be located remotely from the first conditioner device
124A. Utilizing this architecture, the optical device 128 comprises
optics necessary to deliver the beam 140 to the processing surface
112 of the polishing pad 108. The conditioner head 126 is coupled
to a support member 130 by a support arm 132. The support member
130 is disposed through the base 104 of the processing station 100.
Bearings (not shown) are provided between the base 104 and the
support member 130 to facilitate rotation of the support member 130
about a rotational axis C relative to the base 104. An actuator 134
is coupled between the base 104 and the support member 130 to
control the rotational orientation of the support member 130 about
the rotational axis C to allow the conditioner head 126 to move in
an arc or sweeping motion above the processing surface 112 of the
polishing pad 108.
[0032] In one embodiment, the laser emitter 129 is utilized to emit
the beam 140 that impinges the polishing pad 108 to condition the
processing surface 112. For example, the beam 140 may be utilized
to form groove patterns in or on the processing surface 112 of the
polishing pad 108. The beam 140 may be a primary beam or the beam
140 may be a secondary beam that is emitted from a reflective
component (not shown) that may be part of the optical device 128.
The groove patterns provided in or on the processing surface 112 of
the polishing pad 108 may be formed on polishing pads that have a
relatively flat or planar processing surface, and may also be
formed on polishing pads that have a non-planar processing surface.
For example, the beam 140 and/or 154 may be utilized to condition
polishing pads with a non-planar processing surface without
flattening the processing surface.
[0033] The support member 130 may house drive components to
selectively control the vertical position (in the Z axis) and/or
the angle .alpha. of one of the conditioner head 126 and the
optical device 128 relative to the plane of the processing surface
112 of the polishing pad 108. The support member 130 and/or the
support arm 132 may also contain signal members 136 that are
coupled between a signal generator 138 and the optical device 128.
The signal generator 138 may be a controllable power supply and the
signal members 136 may be wires or optical fibers. The actuator 134
may also provide vertical positioning of the support member 130 (in
the Z direction) to provide height control of the conditioner head
126 relative to the polishing pad 108.
[0034] In some embodiments, the actuator 134 may also be used to
provide contact between the polishing pad 108 and the conditioner
head 126, as well as urge the conditioner head 126 against the
processing surface 112 of the polishing pad 108 with a controllable
downforce. In one embodiment (not shown), the conditioner head 126
may include a housing that contacts the polishing pad 108 during
conditioning. The housing may be coupled to a vacuum device (not
shown) and/or a fluid source (not shown) to facilitate removal of
materials that are released from the processing surface 112 of the
polishing pad 108 during conditioning.
[0035] The second conditioner device 124B is positioned above the
processing surface 112 of the polishing pad 108, and, in one
embodiment, is supported by a ceiling 142 of an enclosure 144 that
at least partially isolates the processing station 100 from the
surrounding environment. The second conditioner device 124B
includes the optical device 128, which may include the laser
emitter 129 and/or optics necessary for delivering a secondary beam
154 generated by the laser emitter 129 to the processing surface
112 of the polishing pad 108 disposed on the platen 102. In one
embodiment, the optical device 128 is positioned to direct the
secondary beam 154 through an opening 146 formed through the
ceiling 142. The opening 146 may include a window 148 that is
transparent to the wavelength of the secondary beam 154. The window
148 may be utilized to prevent any polishing debris or gases from
exiting the enclosure 144. In this embodiment, the optical device
128 includes the laser emitter 129 and may optionally include a
reflective component 150 to scan the secondary beam 154 relative to
the processing surface 112 of the polishing pad 108 to condition
the processing surface 112 of the polishing pad 108. The reflective
component 150 may be a mirror, such as a scanning mirror or a
scanning galvo-mirror that is coupled to an actuator 152 to move
the reflective component 150 about an axis D (about the X axis). In
another embodiment, the reflective component 150 may be configured
to rotate about the Y axis (to change the angle .alpha. relative to
the processing surface 112 of the polishing pad 108) as an
alternative to, or in addition to, the movement about the axis
D.
[0036] In one embodiment, the laser emitter 129 is adapted to emit
the beam 140 as a primary beam that may be directed through the
window 148 toward the processing surface 112 of the polishing pad
108 to condition the processing surface 112 of the polishing pad
108, for example, by forming groove patterns in or on the
processing surface 112 of the polishing pad 108. In another
embodiment, the laser emitter 129 emits the beam 140 toward the
reflective component 150 to provide the secondary beam 154 that
impinges the polishing pad 108 to condition the processing surface
112 of the polishing pad 108, for example, by forming groove
patterns in or on the processing surface 112 of the polishing pad
108.
[0037] FIG. 2 is a top plan view of the processing station 100 of
FIG. 1 showing one embodiment of a patterned processing surface 200
on the polishing pad 108. The patterned processing surface 200
facilitates removal of material from a substrate 116 and/or fluid
transport during processing. The patterned processing surface 200
may be formed using the first conditioner device 124A and/or the
second conditioner device 124B of FIG. 1. The patterned processing
surface 200 may include grooves or channels, hereinafter referred
to as marks 205 formed in the body 110 to a desired depth.
[0038] Each of the marks 205 may comprise a fluid retaining
structure formed in the body 110 of the polishing pad 108 by the
optical device 128 of the first conditioner device 124A and/or the
second conditioner device 124B of FIG. 1. The marks 205 may be
linear or curved, zig-zagged, and may have a radial, grid, spiral
or circular orientation on the polishing pad 108. The marks 205 may
be intersecting or non-intersecting. Alternatively or additionally,
the processing surface 112 of the polishing pad 108 may be
embossed.
[0039] In this embodiment, the patterned processing surface 200
includes a plurality of marks 205 that may be substantially
concentric. In some embodiments, the marks 205 may be intermittent
to form discrete marks 208A separated by non-conditioned areas 208B
of the processing surface 112 of the polishing pad 108 (e.g., areas
of the processing surface 112 of the polishing pad 108 that are not
conditioned by the optical device 128 (shown in FIG. 1)). Each of
the marks 208A may be grooves, channels or holes that may comprise
a fluid retaining structure formed the body 110 of the polishing
pad 108 by the first conditioner device 124A and/or the second
conditioner device 124B. The marks 208A may also be linear or
curved, zig-zagged, and may have a radial, grid, spiral or circular
orientation on the polishing pad 108. FIG. 2 also shows the
substrate 116 disposed on the processing surface 112 of the
polishing pad 108 (partially in phantom) to indicate one embodiment
of a polishing sweep pattern 215 of the substrate 116 on the
patterned processing surface 200 during polishing.
[0040] Each of the marks 205 and/or marks 208A may be formed by
continuous or intermittent pulsing of the signal generator 138
(shown in FIG. 1) in order to provide a continuous or intermittent
beam (i.e., 140 and/or 154 shown in FIG. 1) from the optical device
128 (shown in FIG. 1) directed toward the processing surface 112 of
the polishing pad 108. The marks 208A may define an array of holes
or short, linear or curved channels in the processing surface 112
of the polishing pad 108 as shown in FIG. 2.
[0041] During conditioning, which may be performed while polishing
or between polishing processes, the polishing pad 108 may be
rotated at about 0.5 revolutions per minute (rpm) to about 122 rpm
while forming the mark and/or groove patterns on the processing
surface 112 of the polishing pad 108. The pattern of marks 205
and/or marks 208A on the processing surface 112 of the polishing
pad 108 may include a pitch of about 50 microns (.mu.m) to about
1000 .mu.m. In one embodiment, at least a portion of the marks 205
and/or marks 208A formed in the processing surface 112 of the
polishing pad 108 may include a width of about 50 .mu.m to about
500 .mu.m. The marks 205 and/or marks 208A formed in the processing
surface 112 of the polishing pad 108 may include a depth of about 5
.mu.m to about 250 .mu.m, such as about 25 .mu.m to about 112
.mu.m. The width and/or depth of the marks 205 and/or marks 208A
formed in the processing surface 112 of the polishing pad 108 may
be maintained during the entire lifetime of the polishing pad 108
using the optical device 128. For example, the optical device 128
may be used to refresh the width and/or depth of the marks 205
and/or marks 208A during polishing processes, or in between
polishing processes. In one embodiment, the optical device 128 is
used to refresh the width and/or depth of the marks 205 and/or
marks 208A between each substrate 116 that is polished on the
polishing pad 108, such as after polishing a first substrate and
before polishing a second substrate. In another embodiment, the
optical device 128 is used to refresh the width and/or depth of the
marks 205 and/or marks 208A, as necessary, which may be subsequent
to a polishing process performed on more than one substrate 116
(e.g., two or more substrates).
[0042] In one example of operation of the first conditioner device
124A, the support member 130 may be rotatable in order to move the
conditioner head 126 (with the optical device 128 disposed therein)
on the support arm 132 in a sweep pattern 210 across the processing
surface 112 of the polishing pad 108. In one aspect, the rotational
movement of the polishing pad 108 during processing is utilized in
conjunction with the application of optical energy from the optical
device 128 of the first conditioner device 124A and/or the sweep
pattern 210 to form the pattern of marks 205 and/or marks 208A on
the processing surface 112 of the polishing pad 108. In another
aspect, the rotational movement of the polishing pad 108 during
processing is utilized in conjunction with the application of
optical energy from the optical device 128 of the second
conditioner device 124B.
[0043] FIG. 3 is a cross-sectional view of a portion of a polishing
pad 108 showing a graded groove pattern in the processing surface
112 provided by one or both of the first conditioner device 124A
and the second conditioner device 124B (both shown in FIG. 1). The
graded groove pattern includes first grooves 300A and second
grooves 300B that are formed by the optical device 128 at a
non-uniform depth in the body 110. For example, when the optical
device 128 is a laser device, the power may be pulsed between a low
power setting to form the first grooves 300A at a first, shallower
depth, and a high power setting to form the second grooves 300B at
a second, deeper depth. The first grooves 300A and the second
grooves 300B may be formed as a continuous groove in the processing
surface 112, such as marks 205 shown in FIG. 2. While not shown,
the first grooves 300A and second grooves 300B may be formed in an
array, such as marks 208A shown in FIG. 2.
[0044] Forming groove patterns on polishing pads using laser
devices has been used in the manufacture of new polishing pads. In
this function, the pad material is generally moisture-free, and
lasers with relatively high absorption coefficients are used.
Carbon dioxide (CO.sub.2) laser devices with wavelengths of about
10.6 .mu.m (e.g., far infrared spectrum) may be utilized for
grooving patterns in this liquid-free medium. However, during
conditioning a polishing pad during substrate polishing, the
polishing pad is wetted with a polishing fluid or polishing
compound, of which water is a main constituent. The use of laser
devices having wavelengths that are readily absorbed by the
polishing medium (e.g., water), such as 10.6 .mu.m, creates
challenges. When the optical energy is absorbed by water in the pad
material, heating of the water ensues. The heating of the water may
cause the water to boil. As the pad material is generally porous,
the boiling of water in pores, or localized areas of pores, may
cause ruptures in the pad surface. This rupturing is generally
uncontrollable across different areas of the pad surface, and may
produce large asperities, as well as a non-uniform grooving pattern
across the polishing surface, and, ultimately, unsuitable substrate
polishing results.
[0045] Conditioning of the polishing pad 108 utilizing optical
devices 128 as described herein may utilize the beams 140 and/or
154 having wavelengths that are not readily absorbed by a polishing
medium (e.g., polishing fluid or polishing compound) but are
absorbed efficiently by the pad material. Since the polishing
medium is substantially transparent to the beams 140 and/or 154, a
direct ablation of the pad material may be realized without the
problems encountered from moisture in the pad material, and a
controllable groove pattern may be formed in the processing surface
112 of the polishing pad 108 as described herein.
[0046] FIG. 4 is a graph 400 showing absorption coefficients
(1/centimeter (cm) or cm.sup.-1) for various wavelengths. A "water
window" is interposed on the graph 400. Wavelengths in between
about 200 nanometers (nm) and about 1,200 nm show a low absorption
coefficient (less than about 1.0/cm) while wavelengths above 1,200
nm have a high absorption coefficient (greater than about 100/cm).
Thus, laser devices, such as the laser emitter 129 described in
FIG. 1), having wavelength ranges within the "water window" are
utilized with the first conditioner device 124A and the second
conditioner device 124B, as shown in FIGS. 1, 2 and 3.
[0047] Examples of suitable wavelengths for the laser emitter 129
include ultraviolet wavelength ranges (e.g., about 355 nm), visible
wavelength ranges (e.g., about 532 nm), near infrared wavelength
ranges (e.g., about 1064 nm), and combinations thereof. In one
embodiment, the absorption coefficient of the material of the
polishing pad 108 is greater than about 1.0/cm, such as about
5.0/cm, or greater, while the absorption coefficient of the
polishing medium is less than about 1.0/cm, such as about 0.5/cm.
In one aspect, the wavelengths of the laser emitter 129 are
substantially transparent (non-reactive) with the water-based
polishing medium and the emitted beam is not significantly affected
by the polishing medium. For example, the layer of the polishing
medium on the processing surface 112 of the polishing pad 108 is
relatively thin, and the emitted beam passes therethrough and onto
the processing surface 112 without interacting with the polishing
medium. In one embodiment, the emitted beam from the laser emitter
129 passes through air in the space above the processing surface
112 of the polishing pad 108 and is not affected by the polishing
medium such that beam properties, such as spot size and/or angle of
incidence, are not significantly altered by the polishing medium.
In one aspect, the wavelength ranges provided by the laser emitter
129 are substantially non-reactive with a polishing medium utilized
in the polishing process but is reactive with the polishing pad
material in order to form groove patterns shown and described in
FIGS. 2 and 3. In another aspect, the wavelength ranges provided by
the laser emitter 129 are absorbed by polishing pad material in
preference to the polishing medium utilized in the polishing
process in order to form mark and/or groove patterns shown and
described in FIGS. 2 and 3.
[0048] In another aspect, the primary beam 140 is provided in a
wavelength range that is substantially non-reactive with a
polishing medium utilized in the polishing process, but is reactive
with the polishing pad material, in order to form groove patterns
shown and described in FIGS. 2 and 3.
[0049] "Substantially transparent" may be defined as the
incapability of the beam to cause a phase change of the polishing
medium under normal operating conditions (i.e., wavelength range of
the beam, output power of the beam, spot size of the beam, dwell
time of the beam on the polishing pad material, and combinations
thereof). "Substantially transparent" may also be defined as the
incapability of the beam to cause the polishing medium to heat up
and/or boil under normal use in the conditioning process as
described herein. For example, the wavelengths of the laser emitter
129 as described herein would not cause a substantial rise in
temperature of the polishing medium under normal operating
conditions using a pulsed beam and/or short dwell times.
"Substantially transparent" may also be defined as the incapability
of the polishing medium to affect properties of the beam emitted
from the laser emitter 129 under normal use in the conditioning
process as described herein. "Substantially non-reactive" may be
defined as the incapability of the beam to cause a phase change of
the polishing medium under normal operating conditions (i.e.,
wavelength range of the beam, output power of the beam, spot size
of the beam, dwell time of the beam on the polishing pad material,
and combinations thereof). "Substantially non-reactive" may also be
defined as the incapability of the beam to cause the polishing
medium to heat up and/or boil under normal use in the conditioning
process as described herein. For example, the wavelengths of the
laser emitter 129 as described herein would not cause a substantial
rise in temperature of the polishing medium under normal operating
conditions using a pulsed beam and/or short dwell times.
[0050] As stated above, periodic conditioning of the polishing pad
108 is needed to refresh the surface of the polishing pad in order
to maintain an optimal removal rate. In order to ensure efficient
conditioning of the processing surface 112 of the polishing pad
108, which provides the optimal removal rate, the state of the
polishing pad 108 must be monitored, and conditioning and/or
polishing processes may be changed based on the state of the
polishing pad 108. In one embodiment, conditioning parameters may
be adjusted based on the state of the processing surface 112 of the
polishing pad 108 based on input from one or more monitoring
devices associated with the processing station 100. Profilometry
(contact or non-contact) and interferometry techniques performed on
processed substrates may also be utilized to adjust conditioning
parameters.
[0051] Conditioning parameters include the frequency and/or
duration of pad conditioning, laser power output, laser pulse time,
wavelength, and/or frequency, laser pulse length, spot size (beam
diameter), angle of incidence of the beam, and combinations
thereof. Some of the conditioning parameters may be utilized as
control knobs to maintain consistent or a desired topography of the
processing surface 112 of the polishing pad 108. For example, pulse
shape (beam intensity profile) in time and/or the beam intensity
profile in space (beam intensity per unit of area) may provide
real-time adjustment of the topography control. Adjustment of the
conditioning parameters may provide optimal control of asperity
count, as well as dimensions and/or shape of the asperities on the
processing surface 112 of the polishing pad 108. In one embodiment,
when forming asperities using the laser emitter 129 in a hole
drilling mode, where the laser emitter 129 is pulsed to form holes
at predetermined pitch and depth over the processing surface 112 of
the polishing pad 108, pitch and/or pulses maybe such that fewer
asperities are formed at the edge and center of the pad, while
denser and deeper asperties are formed at the mid-radius of the
pad. Such a variation in asperity height and density may enable
more uniform polishing and improve planarization of substrates.
[0052] FIG. 5 is a partial sectional view of the processing station
100 of FIG. 1 showing various embodiments of monitoring and control
systems that enable closed-loop control of the conditioning process
and the polishing processes performed thereon. A
monitoring/feedback system 500 is shown within the processing
station 100. Components of the monitoring/feedback system 500 may
be in communication with the controller for closed-loop control of
the processes on the processing station 100.
[0053] The monitoring/feedback system 500 may include a first
monitoring device comprising one or more first sensors 505 disposed
on portions of the processing station 100. Each of the first
sensors 505 may be an optical device utilized to view the
processing surface 112 of the polishing pad 108. For example, the
first sensors 505 may be coupled to the ceiling 142 of the
enclosure 144, on the support arm 132, on the support member 118,
and combinations thereof, as well as other locations where the
processing surface 112 of the polishing pad 108 may be viewed. One
or more of the first sensors 505 may be a camera, or an optical
device, such as a laser sensor, which emits a beam 510 that is
directed toward the processing surface 112 of the polishing pad
108. In one example, the first sensor 505 (located on the enclosure
144) may comprise a transmitter 515A that emits the beam 510 and a
receiver 515B that receives a reflected beam (not shown). The
intensity of the reflected beam may be utilized to provide a
real-time metric of the roughness and/or porosity (i.e.,
topography) of the processing surface 112 of the polishing pad 108.
The roughness and/or porosity metric may be used to determine
conditioning parameters that may be adjusted. The first sensors 505
that comprise optical devices may also be used to determine an
average height of the processing surface 112 of the polishing pad
108, as well as determine depths of the first grooves 300A and a
depth of the second grooves 300B (both shown in FIG. 3).
[0054] In one embodiment, one or more of the first sensors 505 may
be a camera, such as a CCD camera, or a laser surface scanner, that
monitors the processing surface 112 of the polishing pad 108 during
conditioning and/or polishing. Images from the first sensors 505
may be sent to the controller and a topographical metric of the
processing surface 112 of the polishing pad 108 may be obtained.
The topographical metric may be used to determine conditioning
parameters that may be adjusted. The topographical metric may
include an average height of the processing surface 112 of the
polishing pad 108, as well as depths of the first grooves 300A and
a depth of the second grooves 300B (both shown in FIG. 3) that may
be used to adjust conditioning parameters.
[0055] Alternatively, one or more of the first sensors 505 may be a
capacitive sensor to provide topographical information indicative
of the state of the processing surface 112 of the polishing pad
108. The first sensors 505 utilizing capacitive coupling could also
be utilized to detect and measure proximity and/or displacement.
First sensors 505 that comprise capacitive sensing devices may also
be used to monitor the profile of the polishing pad 108, such as
determining an average height of the processing surface 112 of the
polishing pad 108 and/or monitoring the thickness of the polishing
pad 108, as well as determine depths of the first grooves 300A and
a depth of the second grooves 300B (both shown in FIG. 3). In one
embodiment, thickness information can be used to implement
corrective conditioning, such that more conditioning is affected
where the polishing pad 108 is thick and less conditioning is
affected where the polishing pad 108 is thin to obtain a flat
processing surface 112 of the polishing pad 108 with minimal
thickness variation. In another embodiment, profile information can
be used to determine wear of the processing surface 112 of the
polishing pad 108 and conditioning parameters may be adjusted to
provide uniform wear across the processing surface 112 of the
polishing pad 108.
[0056] The monitoring/feedback system 500 may include a second
monitoring device comprising one or more second sensors 520A and
520B. The second sensors 520A, 520B may be rotational sensors
utilized to sense torque and provide a torque value to the
controller. The second sensor 520A may be a platen rotational
sensor utilized to obtain a metric indicative of the force required
to rotate the platen 102 and polishing pad 108 during conditioning
and/or polishing. The second sensor 520A may be a torque or other
rotational force sensor coupled to the drive motor 106, or to an
output shaft of the drive motor 106. Likewise, the second sensor
520B may be coupled to the carrier head 114. The second sensor 520B
may be a rotational sensor for the carrier head 114 that is
utilized to obtain a metric of force required to sweep the carrier
head 114 in the polishing sweep pattern 215 (shown in FIG. 2). The
second sensor 520B may be a torque sensor, a shear force sensor, or
other rotational force sensor coupled to the drive system 120, or
an output shaft of the drive system 120. The second sensors 520A,
520B may provide a torque value to the controller, which is
utilized to determine conditioning parameters that may be
adjusted.
[0057] The monitoring/feedback system 500 may include a third
monitoring device, such as a third sensor 525. The third sensor 525
may comprise a pad surface sensor that reacts based on changes in
pad topography. The third sensor 525 may be a friction sensor that
includes a pad coupling member 530 and a sensor device 535. The pad
coupling member 530 may be a disk or plate of a material that is
utilized to ride on the processing surface 112 of the polishing pad
108 and interacts with the processing surface 112 as the polishing
pad 108 rotates. The pad coupling member 530 may move based on
unevenness in the processing surface and displacement is sensed by
the sensor device 535. The displacement values are provided to the
controller and adjustments to conditioning parameters may be
determined and implemented. Alternatively or additionally, the pad
coupling member 530 may be urged against the processing surface 112
at a specified load, and displacement values, torque values, or
other values based on friction, may be sensed by the sensor device
535. The displacement values, torque values, or other values are
provided to the controller and adjustments to conditioning
parameters may be determined and implemented. While the third
sensor 525 is shown coupled to the base 104 and is positioned
adjacent an edge of the polishing pad 108, the third sensor 525, or
multiple third sensors 525, may be coupled to other portions of the
processing station 100 to obtain feedback of the state of the
polishing pad 108 at different/multiple locations.
[0058] The monitoring/feedback system 500 may include a fourth
monitoring device, such as a fourth sensor 540. The fourth sensor
540 may comprise sensing device that provides a metric of material
that remains on the substrate 116 during a polishing process. The
fourth sensor 540 may be an eddy current sensor or an optical
device, such as a laser emitter and detector, or a light emitting
device (e.g., white light source) and detector, that is disposed
within the platen 102 beneath a window 545 formed in the polishing
pad 108. The fourth sensor 540 may be used to determine the
topography of the substrate 116 during a polishing process, which
is an indication of the level of conditioning of the topography of
the processing surface 112. The fourth sensor 540 may be used to
determine dishing and/or erosion, which is indicative of
over-conditioning of the polishing pad 108. Thus, real-time
adjustment of the conditioning parameters may be provided based on
observations of the topography of the substrate 116.
[0059] In one embodiment, signals from one or more of the sensors
505, 520A, 520B, 525, and 540 indicating a metric of roughness
and/or shear force measurement may be used to increase or decrease
the number of pulses to restore surface roughness such that an
optimum topography of the processing surface 112 of the polishing
pad 108 is maintained. In another embodiment, the pitch of the
marks 208A (shown in FIG. 2) may be increased or decreased alone,
or in combination with, the number of pulses from the laser emitter
129 for more stable polishing performance.
[0060] FIG. 6 is a top plan view of a polishing pad 600 showing
another embodiment of a patterned processing surface 605 provided
by the methods disclosed herein. In this embodiment, the patterned
processing surface 605 is provided by a linear scan of an optical
device 128 (shown in FIGS. 1 and 5) from near a geometric center of
the polishing pad 600 to an edge of the polishing pad 600, and vice
versa. For example, the optical device 128 provides a beam (i.e.,
beam 140 and/or beam 154 shown in FIGS. 1 and 5) that scans radii
of the polishing pad 600 while the polishing pad 600 is rotating.
Due to the movement of the polishing pad 600, the rotational speed
is higher at the edge of the polishing pad 600 relative to the
rotational speed of the polishing pad 600 at the center (e.g.,
where the rotational speed is zero). The result is a
spirograph-type pattern on the patterned processing surface 605 as
shown in FIG. 6.
[0061] The patterned processing surface 605 includes a plurality of
marks 610. The depth of the marks 610 and/or the pitch of the marks
610 are determined by one or a combination of scan speed of the
beam (140 and/or 154), a pulse rate of the beam and the rotational
speed of the polishing pad 600. For example, the spirograph-type
pattern of the patterned processing surface 605 includes a
plurality of arcs (only arcs 615A and 615B are shown) formed by the
marks 610. The arc 615A may begin at the center of the polishing
pad 600 and transition to the arc 6158 near the periphery of the
polishing pad 600, while the arc 6158 ends at the center of the
polishing pad 600. The circular shape of the arcs 615A, 6158 may be
due to the rotational speed of the polishing pad 600. For example,
the arcs 615A. 615B may be more elliptical when the rotational
speed of the polishing pad 600 is slowed. A similar effect may be
provided by varying the scan speed of the beam (140 and/or 154) as
it traverses the pad radially. Scan speed maybe varied to
compensate for varying radial velocity of the polishing pad 600 to
maintain a fixed relative speed between the beam and the polishing
pad 600 to affect uniform marking depth.
[0062] FIGS. 7A-7C are schematic top views of mark arrays 700A-700C
that may be formed on a polishing pad (shown in FIGS. 1, 2, 5 and
6) using the methods as described herein. FIG. 7A shows a mark
array 700A having a plurality of marks 705 having a substantially
uniform outer dimension d as well as a substantially similar pitch
710A in the X direction. The pitch in the Y direction may be
substantially equal to the pitch 710A. FIG. 7B shows a mark array
700B having a plurality of marks 705 with a substantially uniform
outer dimension d as well as a substantially similar pitch 710B in
the X direction that is greater than the pitch 710A. The pitch in
the Y direction may be substantially equal to the pitch 710B. FIG.
7C shows a mark array 700C having a plurality of marks 705 having a
substantially uniform outer dimension d. However, a pitch of the
marks 705 is set such that the marks 705 at least partially overlap
and form lines or chains 715 of marks 705. While the marks 705 in
FIGS. 7A-7C are shown as circular, the marks 705 may be one or any
combination of shapes, such as circular as shown, rectangles,
triangles, linear patterns, and the like. The dimension d may be a
diameter in the case of a circular mark, or an outer dimension of
other polygonal shapes. The dimension d may be provided by setting
a spot size of the beam during conditioning. Spot sizes may be
about 20 .mu.m to about 200 .mu.m. Additionally, one or a
combination of the dimensions d shown in the mark arrays 700A-700C
may be provided as needed to provide a mark array consisting of
similar size of marks 705 (e.g., the same dimension d and/or the
same pitch) or marks 705 of different sizes and pitches.
[0063] FIGS. 8A-8C are schematic cross-sectional views of mark
arrays 800A-800C that may be formed on a body 110 of a polishing
pad (shown in FIGS. 1, 2, 5 and 6) using the methods as described
herein. FIG. 8A shows a mark array 800A having a plurality of marks
805 with a substantially uniform pitch 810A as well as a
substantially uniform height h. FIG. 8B shows a mark array 800B
having a plurality of marks 805 with a substantially uniform pitch
810B as well as a substantially similar height h that is less than
the height h of the marks 805 shown in FIG. 8A. FIG. 8C shows a
mark array 800C having a plurality of marks 805 having a
substantially uniform pitch 810C and a height h. One or a
combination of the heights h shown in the mark arrays 800A-800C may
be provided as needed to provide a mark array consisting of similar
size of marks 805 (e.g., the same height h and/or the same pitch)
or marks 805 of different heights h and pitches. The height h may
be provided by setting a appropriate number of discreet pulses of
the beam during conditioning. Increasing the number of pulses may
promote greater mark depth (i.e., height h).
[0064] FIGS. 9A-9D are schematic top views of various embodiments
of marks that may be formed in or on a polishing pad (shown in
FIGS. 1, 2, 5 and 6) using the methods as described herein. FIG. 9A
depicts a mark 905A in the form of a triangle; FIG. 9B depicts a
mark 905B in the form of a rectangle; FIG. 9C depicts a mark 905C
in the form of a circle; and FIG. 9D depicts a mark 905D having a
plurality of linear grooves 910. Although four intersecting grooves
910 are shown, more or less than four may be used. Additionally,
the grooves 910 may not intersect. One or a combination of the
marks 905A-905D may be used to form patterned processing surfaces
on a polishing pad as described herein. Additionally, any of the
marks 905A-905D may be sized to have a major dimension from a few
millimeters to near the diameter of the polishing pad. For example,
the mark 905A (or the mark 905B) may be sized such that the corners
are adjacent the periphery of the polishing pad. Additional marks
(905A, 905B, or combinations of the marks 905A-905D) may be formed
within the mark 905A (or the mark 905B), or nested over or within
the mark 905A (or the mark 905B). In another example, the mark 905D
may be formed such that a length of the grooves 910 are
substantially equal to the diameter of the polishing pad.
[0065] FIGS. 10A and 10B are schematic top views of a polishing pad
1000 showing embodiments of a portion of a patterned processing
surface 1005A, 1005B thereon, respectively. In FIG. 10A, the
polishing pad 1000 includes a plurality of marks 1010A formed as
circles. In FIG. 10B, the polishing pad 1000 includes a plurality
of marks 1010B in the form of rectangles. Each of the patterned
processing surfaces 1005A, 1005B may be formed in or on the entire
surface of the polishing pad 1000, or combinations of each may be
used.
[0066] Some or all of the marks 1010A, 1010B may partially overlap
with other marks 1010A, 1010B. In one example, the patterned
processing surface 1005A may consist of the plurality of marks
1010A that overlap. At least a portion of the marks 1010A may
overlap another adjacent mark 1010A by about 50%, or greater, along
the radius direction. The depth of the marks 1010A may be about 50
.mu.m, or less. A similar process may be used on the patterned
processing surface 1005B to form an overlap of marks 1010B as
described above in the patterned processing surface 1005A.
[0067] Another conditioning method includes scanning the beam (140
and/or 154) in a radial or a circumferential direction relative to
the polishing pad 1000 to achieve different relative velocities
between the beam and the polishing pad 1000. For example, the beam
may be scanned in the direction of rotation of the polishing pad
1000 to create marks that are linear or arcing.
[0068] Apparatus and methods for providing a patterned processing
surface 200 (FIG. 2), 605 (FIG. 6), 1005A (FIG. 10A) and 1005B
(FIG. 10B) on a polishing pad 108 (FIG. 2), 600 (FIG. 6) and 1000
(FIGS. 10A and 10B) are provided. The patterned processing surface
may be formed by a beam and include multiple patterns including
lines, arcs or shapes, marks, objects, and the like, in discrete
patterns, repeating patterns, overlapping patterns or marks, and
the like. Additionally, apparatus and methods for a
monitoring/feedback system 500 for closed-loop control of a CMP
system utilizing optical conditioning are provided. The
monitoring/feedback system 500 provides control of conditioning
parameters to obtain optimal removal rates. The control of the
conditioning parameters provides precise topographical control of
the processing surface of a polishing pad, which results in lower
defect rates, longer pad lifetime, as well as improving
throughput.
[0069] 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.
* * * * *