U.S. patent application number 12/837705 was filed with the patent office on 2011-01-20 for grooved cmp polishing pad.
This patent application is currently assigned to Cabot Microelectronics Corporation. Invention is credited to Hao-Kuang Chiu, Jia-Cheng Hsu, Dinesh Khanna, Sheng-Huan Liu, Ananth Naman, Fred Sun, Ching-Ming TSAI.
Application Number | 20110014858 12/837705 |
Document ID | / |
Family ID | 43450188 |
Filed Date | 2011-01-20 |
United States Patent
Application |
20110014858 |
Kind Code |
A1 |
TSAI; Ching-Ming ; et
al. |
January 20, 2011 |
GROOVED CMP POLISHING PAD
Abstract
The present invention provides polishing pads for use in CMP
processes. In one embodiment, a pad comprises a surface defining a
plurality of grooves with landing surfaces separating the grooves,
the landing surfaces together defining a substantially coplanar
polishing surface, each groove having a depth of at least about 10
mil and a width, W.sub.G, with any two adjacent grooves being
separated from each other a landing surface having a width,
W.sub.L, wherein the quotient W.sub.L/W.sub.G is less than or equal
to 3. In a preferred embodiment, the surface of the pad defines a
series of concentric substantially circular grooves. In an
alternative embodiment, the surface of the pad defines a spiral
groove having a depth of at least about 10 mil and a width W.sub.G,
and a spiral landing surface outlining spiral groove the having a
width, W.sub.L, wherein the spiral landing surface defines a
substantially coplanar polishing surface and the quotient
W.sub.L/W.sub.G is less than or equal to 3.
Inventors: |
TSAI; Ching-Ming; (Jhudong
Township, TW) ; Sun; Fred; (Naperville, IL) ;
Liu; Sheng-Huan; (KweiShen, TW) ; Hsu; Jia-Cheng;
(Tainan City, TW) ; Naman; Ananth; (Naperville,
IL) ; Chiu; Hao-Kuang; (Taipei City, TW) ;
Khanna; Dinesh; (Naperville, IL) |
Correspondence
Address: |
STEVEN WESEMAN;ASSOCIATE GENERAL COUNSEL, I.P.
CABOT MICROELECTRONICS CORPORATION, 870 NORTH COMMONS DRIVE
AURORA
IL
60504
US
|
Assignee: |
Cabot Microelectronics
Corporation
|
Family ID: |
43450188 |
Appl. No.: |
12/837705 |
Filed: |
July 16, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61271068 |
Jul 16, 2009 |
|
|
|
Current U.S.
Class: |
451/527 |
Current CPC
Class: |
B24B 37/26 20130101 |
Class at
Publication: |
451/527 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A polishing pad suitable for use in chemical-mechanical
polishing of a substrate, the pad comprising a surface defining a
plurality of grooves with landing surfaces separating the grooves,
the landing surfaces together defining a substantially coplanar
polishing surface, each groove having a depth of at least about 10
mil and a width, W.sub.G, with any two adjacent grooves being
separated by a landing surface having a width, W.sub.L, wherein the
quotient W.sub.L/W.sub.G, is less than or equal to 3.
2. The polishing pad of claim 1 wherein the plurality of grooves
comprises concentric, substantially circular grooves.
3. The polishing pad of claim 1 wherein the grooves have a depth of
not more than about 50 mil.
4. The polishing pad of claim 1 wherein the depth of each groove is
in the range of about 10 to about 50 mil.
5. The polishing pad of claim 1 wherein W.sub.L for each landing
surface is not more than about 80 mil.
6. The polishing pad of claim 1 wherein W.sub.L for each landing
surface is in the range of about 30 mil to about 60 mil.
7. The polishing pad of claim 1 wherein W.sub.G for each groove is
in the range of about 20 mil to about 40 mil.
8. The polishing pad of claim 1 wherein each groove has
substantially the same depth.
9. The polishing pad of claim 1 wherein each groove has
substantially the same W.sub.G.
10. The polishing pad of claim 1 wherein each landing surface has
substantially the same W.sub.L.
11. A polishing pad suitable for use in chemical-mechanical
polishing of a substrate, the pad comprising a surface defining a
spiral groove with a spiral landing surface separating the turns of
the spiral groove, the spiral landing surface defining a
substantially coplanar polishing surface, the groove having a depth
of at least about 10 mil and a width, W.sub.G, and the landing
surface having a width, W.sub.L, wherein the quotient
W.sub.L/W.sub.G is less than or equal to 3.
12. The polishing pad of claim 11 wherein the spiral groove has a
depth of not more than about 50 mil.
13. The polishing pad of claim 11 wherein the depth of the groove
is in the range of about 10 to about 50 mil.
14. The polishing pad of claim 11 wherein W.sub.L is not more than
about 80 mil.
15. The polishing pad of claim 11 wherein W.sub.L is in the range
of about 30 mil to about 60 mil.
16. The polishing pad of claim 11 wherein W.sub.G is in the range
of about 20 mil to about 40 mil.
17. The polishing pad of claim 11 wherein the quotient
W.sub.L/W.sub.G is less than or equal to about 2.
18. The polishing pad of claim 11 wherein the quotient
W.sub.L/W.sub.G is less than or equal to about 1.
19. The polishing pad of claim 1 wherein the quotient
W.sub.L/W.sub.G is less than or equal to about 2.
20. The polishing pad of claim 1 wherein the quotient
W.sub.L/W.sub.G is less than or equal to about 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application for Patent Ser. No. 61/271,068, filed on Jul. 16, 2009,
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to chemical
mechanical polishing of substrates, and more particularly to a
polishing pad having a grooved pattern for a chemical mechanical
polishing system.
BACKGROUND OF THE INVENTION
[0003] Compositions and methods for chemical-mechanical polishing
of the surface of a substrate are well known in the art. Polishing
compositions (also known as polishing slurries, CMP slurries, and
CMP compositions) for CMP of surfaces of semiconductor substrates
(e.g., integrated circuits) typically contain an abrasive, various
additive compounds, and the like.
[0004] Chemical-mechanical polishing (CMP) involves the concurrent
chemical and mechanical abrasion of surface, e.g., abrasion of an
overlying first layer to expose the surface of a non-planar second
layer on which the first layer is formed. One such process is
described in U.S. Pat. No. 4,789,648 to Beyer et al. Briefly, Beyer
el al., discloses a CMP process using a polishing pad and a slurry
to remove a first layer at a faster rate than a second layer until
the surface of the overlying first layer of material becomes
coplanar with the upper surface of the covered second layer. More
detailed explanations of chemical mechanical polishing are found in
U.S. Pat. No. 4,671,851, No. 4,910,155 and No. 4,944,836.
[0005] In conventional CMP techniques, a substrate carrier or
polishing head is mounted on a carrier assembly and positioned in
contact with a polishing pad in a CMP apparatus. The carrier
assembly provides a controllable pressure to the substrate, urging
the substrate against the polishing pad. The pad and carrier, with
its attached substrate, are moved relative to one another. The
relative movement of the pad and substrate serves to abrade the
surface of the substrate to remove a portion of the material from
the substrate surface, thereby polishing the substrate. The
polishing of the substrate surface typically is further aided by
the chemical activity of the polishing composition (e.g., by
oxidizing agents, acids, bases, or other additives present in the
CMP composition) and/or the mechanical activity of an abrasive
suspended in the polishing composition. Typical abrasive materials
include silicon dioxide, cerium oxide, aluminum oxide, zirconium
oxide, and tin oxide.
[0006] One problem in CMP relates to polishing slurry distribution
over the polishing pad. The CMP process requires the interaction of
the polishing pad, abrasive particles and any reactive agent or
chemical in the polishing composition with the substrate to obtain
the desired polishing results. Ineffective distribution of the
slurry across the surface of the polishing pad can lead to
diminished polishing efficiency. Polishing pads generally include
some feature such as perforations or textures (e.g., grooves,
surface depressions, and the like) to aid in distributing the
abrasive polishing slurry relatively uniformly across the pad.
Grooves are often a preferred texturing feature, because they can
be designed to directly channel the excess slurry to where it is
needed. Grooved polishing pads are often characterized by the
dimensions (e.g., width and depth) of the grooves and the spacing
between the grooves (known as "pitch"). Examples of grooved pads
include those disclosed in U.S. Pat. No. 5,921,855 to Osterheld et
al., U.S. Pat. No. 6,520,847 to Osterheld et al., and U.S. Pat. No.
6,736,847 to James et al.
[0007] While conventional grooved CMP pads have certain preferred
performance characteristics over, for example, perforated pads,
there is still a need in the art for improved pad performance
features, such as improved pad lifetime (e.g., due to reduced wear
rates). The present invention addresses this need.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention provides polishing pads for use in CMP
processes. In one embodiment, a pad comprises a surface defining a
plurality of grooves with landing surfaces separating the grooves,
the landing surfaces together defining a substantially planar
polishing surface, each groove having a depth of at least about 10
mil and a width, W.sub.G, with any two adjacent grooves being
separated from each other by a landing surface having a width,
W.sub.L, wherein the quotient W.sub.L/W.sub.G is less than or equal
to 3. In a preferred embodiment, the surface of the pad defines a
series of concentric, substantially circular grooves. Preferably,
each groove has the same W.sub.G, and each landing surface has the
same W.sub.L.
[0009] In an alternative embodiment, the surface of the pad defines
a spiral groove having a depth of at least about 10 mil and a width
W.sub.G, and a spiral landing surface outlining the spiral groove.
The spiral landing surface has a width, W.sub.L, and defines a
substantially planar publishing surface. As in the previously
described embodiment, the quotient W.sub.L/W.sub.G is less than or
equal to 3.
[0010] The polishing surface of the polishing pads of the present
invention can be formed from any substance suitable for use in CMP
pad construction. In some preferred embodiments the polishing
surface of the pad is formed from a thermoplastic polyurethane
material. The pads can be constructed from a single layer of pad
material or from multiple layers (e.g., a base layer and a surface
layer).
[0011] The polishing pads of the present invention provide an
unexpected improvement in polishing removal rate uniformity over
extended use (e.g., polishing of up to 650 semiconductor wafers)
compared to a conventional grooved pad of similar construction, but
with W.sub.L/W.sub.G equal to about 7.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 illustrates a top plan view of an embodiment of a
polishing pad of the present invention including a plurality of
circular, concentric grooves.
[0013] FIG. 2 provides a partial cross-sectional view of the pad of
FIG. 1.
[0014] FIG. 3 illustrates an embodiment of a polishing pad of the
present invention including a single spiral groove in the polishing
surface.
[0015] FIG. 4 shows a graph of copper removal rate versus number of
wafers polished for a pad of the invention compared to a
conventional reference pad.
[0016] FIG. 5 shows a graph of copper removal rate uniformity
stability versus number of wafers polished for a pad of the
invention compared to a conventional reference pad.
[0017] FIG. 6 shows a graph of pad wear rate for pads of the
invention compared to a conventional reference pad.
DETAILED DESCRIPTION OF THE INVENTION
[0018] In one embodiment, a polishing pad of the present invention
comprises a surface defining a plurality of grooves, preferably
concentric and substantially circular grooves, with landing
surfaces separating the grooves. The landing surfaces together
define a substantially coplanar polishing surface. Each groove has
a depth of at least about 10 mil and a width, W.sub.G, with any two
adjacent grooves being separated by a landing surface having a
width, W.sub.L, wherein the quotient W.sub.L/W.sub.G, is less than
or equal to 3. Preferably, each of the plurality grooves has
substantially the same depth, and/or substantially the same
W.sub.G. Each of the landing surfaces preferably has substantially
the same W.sub.L, as well. The width of each groove preferably is
substantially uniform throughout the majority of the groove depth,
although the bottom of the groove may be rounded, resulting in a
decreasing width near the bottom of the groove.
[0019] FIG. 1 illustrates a top plan view of a polishing pad of the
present invention. Pad 10 includes a surface layer 12 defining
concentric circular grooves 14 separated by landing surfaces 16,
with peripheral surface 18 framing the pad surface. Landing
surfaces 16 are substantially coplanar with each other, as are
peripheral surface 18 and central surface 20. Collectively, landing
surfaces 16 define a substantially coplanar polishing surface.
[0020] FIG. 2 shows a partial cross-sectional view of surface 12
along plane 2-2 of FIG. 1. Surface layer 12 is affixed to base
layer 22. Grooves 14 have a depth, D.sub.G, and a width W.sub.G,
while the landing surfaces 16 have a width, W.sub.L. The distance
from the beginning of one groove to the beginning of the next
groove is defined as the pitch, P, which is equal to the sum of
W.sub.L and W.sub.G. In the pads of the invention W.sub.L/W.sub.G
is less than or equal to 3. Landing surfaces 16 are substantially
coplanar, thereby forming a coplanar
[0021] In an alternative embodiment, a polishing pad of the present
invention comprises a surface defining a spiral groove having a
depth of at least about 10 mil with a spiral landing surface
outlining the spiral groove. The spiral landing surface defines a
substantially planar polishing surface. The groove has a width,
W.sub.G, and the landing surface has a width, W.sub.L, wherein the
quotient W.sub.L/W.sub.G is less than or equal to 3. FIG. 3
provides a top plan view of such an alternative embodiment. Pad 30
includes a substantially planar surface layer 32 having a single
spiral groove 34 formed therein, which is outlined by a nested
spiral landing surface 36. The pitch, P, which is equal to the sum
of the widths of groove 34 and landing surface 36, is also
indicated in FIG. 3.
[0022] In each of the embodiments of the present invention, each
groove in the surface of the polishing pad preferably has a depth
of not more than about 50 mil. In some preferred embodiments, the
depth of each groove is in the range of about 10 to about 50 mil,
more preferably about 15 to about 40 mil.
[0023] If desired, the quotient W.sub.L/W.sub.G in any given
embodiment of the polishing pad of the present invention can less
than or equal to about 2, or less than or equal to about 1.
[0024] In certain preferred embodiments, W.sub.L for each landing
surface is not more than about 80 mil. In other preferred
embodiments, W.sub.L for each landing surface is in the range of
about 30 to about 60 mil. W.sub.G for each groove preferably is not
more than about 50 mil. In some preferred embodiments, W.sub.G for
each groove is in the range of about 20 mil to about 40 mil.
[0025] Table 1 illustrates some specific examples of different
grooving dimensions suitable for polishing pads of the present
invention.
TABLE-US-00001 TABLE 1 Pitch (mil) W.sub.G (mil) W.sub.L (mil)
W.sub.G/W.sub.L W.sub.L/W.sub.G 80 20 60 0.33 3.00 80 30 50 0.60
1.67 80 40 40 1.00 1.00 80 50 30 1.67 0.60 70 20 50 0.40 2.50 70 30
40 0.75 1.33 70 40 30 1.33 0.75 60 20 40 0.50 2.00 60 30 30 1.00
1.00 50 20 30 0.67 1.50 50 30 20 1.50 0.67 40 20 20 1.00 1.00 30 10
20 0.50 2.00 30 20 10 2.00 0.50
[0026] The polishing pads of the present invention are particularly
suited for use in conjunction with a chemical-mechanical polishing
apparatus. Typically, the CMP apparatus comprises a platen, which,
when in use, is in motion and has a velocity that results from
orbital, linear, and/or circular motion, a polishing pad in contact
with the platen and moving relative to the platen when in motion,
and a carrier that holds a substrate to be polished by contacting
and moving relative to the surface of the polishing pad. The
polishing of the substrate takes place by the substrate being
placed in contact with the polishing pad of the invention and then
moving the polishing pad relative to the substrate, so as to abrade
at least a portion of the substrate to polish the substrate.
[0027] Suitable materials for forming at least a portion of a
polishing pad of the invention polishing pads include, for example,
polymers of varying density, hardness, thickness, compressibility,
ability to rebound upon compression, and compression modulus.
Non-limiting examples of such polymers include polyvinylchloride,
polyvinyl fluoride, nylon, fluorocarbon, polycarbonate, polyester,
polyacrylate, polyether, polyethylene, polyamide, polyurethane,
polystyrene, polypropylene, coformed products thereof, and mixtures
thereof. The surface of the polishing pad defining the plurality of
grooves can comprise any such material. In a preferred embodiment,
the surface defining the plurality of grooves or spiral groove
comprises a thermoplastic polyurethane. If desired the pads of the
present invention can be composed of a single layer of material or
can include two or more layers of material, e.g., a base layer and
a surface layer.
[0028] Desirably, the CMP pads of the invention can further
comprise at least one light-or other radiation-transmitting window
region for in situ inspecting and monitoring a polishing process by
analyzing the light or other radiation reflected from a surface of
a workpiece being polished with the pad. Many in situ polishing
endpoint detection systems and techniques for inspecting and
monitoring the polishing process by analyzing light or other
radiation reflected from a surface of the workpiece are known in
the art. Such methods are described, for example, in U.S. Pat. No.
5,196,353 to Sandhu et al., U.S. Pat. No. 5,433,651 to Lustig el
al., U.S. Pat. No. 5,949,927 to Tang, and U.S. Pat. No. 5,964,643
to Birang et al. Desirably, the inspection or monitoring of the
progress of the polishing process with respect to a workpiece being
polished enables the determination of the polishing end-point,
i.e., the determination of when to terminate the polishing process
with respect to a particular workpiece.
[0029] The following examples further illustrate the invention but,
of course, should not be construed as in any way limiting its
scope.
Example 1
[0030] This example illustrates the superior removal rate stability
and removal uniformity stability obtainable in copper CMP utilizing
a polishing pad of the present invention.
[0031] A polishing pad comprising a thermoplastic polyurethane
surface layer including a series of concentric circular grooves
each having a width, W.sub.G, of about 30 mil, separated by
concentric landing surfaces having a width, W.sub.L, of 30 mil
(pitch of 60 mil), with W.sub.L/W.sub.G equal to about 1. The
polishing was repeatedly performed with the same pad on copper
blanket wafers using the commercial polishing slurry C8800 (Cabot
Microelectronics Corporation, Aurora, Ill.) on Mirra polisher under
the following polishing conditions: down-force of 1
pounds-per-square inch (psi), platen speed of 93
revolutions-per-minute (rpm), carrier speed of 87 rpm, and a slurry
feed rate of 100 milliliters-per-minute (mL/min). For comparison,
copper blanket wafers were also polished under the same conditions
with a similar polyurethane polishing pad having concentric annular
grooves separated by concentric annular landing surfaces, but
having W.sub.L of about 70 mil and W.sub.G of about 10 mil (pitch
of about 80 mil), with W.sub.L/W.sub.G of about 7.
[0032] FIG. 4 illustrates the change in copper removal rate versus
number of wafers polished for each of the pads, showing the removal
rates obtained at wafer 150 and wafer 650. As is evident from FIG.
4, the pad having a convention W.sub.L/W.sub.G of greater than 7
exhibited a decrease in Cu removal rate, while the pad of the
present invention, having W.sub.L/W.sub.G of 1, exhibited an
unexpected increase in Cu removal rate.
[0033] The observed removal uniformity stability percentage,
defined as WIWNU or with-in-wafer non-uniformity (i.e., relative
standard deviation of Cu removal across 49 point diameter scan of
entire wafer with 5 mm edge exclusion), obtained with each pad is
graphed in FIG. 5 for the same wafers. As can be seen in FIG. 5,
the pad of the present invention exhibited an unexpectedly
consistent removal uniformity stability compared to the
conventional pad.
Example 2
[0034] This example illustrates the effect of the grooving
configuration on pad wear rate.
[0035] Three polishing pads of the invention comprising a
thermoplastic polyurethane surface layer including a series of
concentric circular grooves were used for relative pad wear test.
The test was performed on an IPEC polisher with 7 ft-lb
conditioning down force, 105 rpm platen speed, and 100 rpm
conditioner rotational speed. Conditioner was from 3M Co (Model
A188). D.I. water was used and the test last for 40 minutes. Wear
rate was calculated using data from minute 10 to minute 40, and
normalized to mil-per-hour by times 2. The pads had the following
dimensions: Pad 60/20-W.sub.G=20 mil, W.sub.L=40 mil, pitch=60 mil,
W.sub.L/W.sub.G=2; Pad 60/30-W.sub.G=30 mil, W.sub.L=30 mil,
pitch=60 mil, W.sub.L/W.sub.G=1; and Pad 40/20-W.sub.G=20 mil,
W.sub.L=20 mil, pitch=40 mil, W.sub.L/W.sub.G=1. For comparison, a
similar polyurethane polishing pad having concentric annular
grooves separated by concentric annular landing surfaces, but
having W.sub.L of about 70 mil and W.sub.G of about 10 mil (pitch
of about 80 mil), with W.sub.L/W.sub.G of about 7 (Pad 80/10) was
tested.
[0036] FIG. 6 provides a graph of pad wear rate in mil/hour for
each of the pads examined. AS the data in FIG. 6 shows, the pad
wear rate increases for a given groove width (e.g., 20 mil) as
W.sub.L/W.sub.G decreases from 2 to 1 (Pads 60/20 and 40/20,
respectively). In addition, the wear rate also increases for a
given pitch (e.g., 60 mil) as the groove width increases from 20 to
30 mil (Pads 60/20 and 60/30, respectively).
[0037] All references, including publications, patent applications,
and patents, cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
[0038] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0039] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *