U.S. patent application number 14/736568 was filed with the patent office on 2015-10-01 for polishing pad with foundation layer and polishing surface layer.
The applicant listed for this patent is William C. Allison, James P. LaCasse, Paul Andre Lefevre, Diane Scott, Alexander William Simpson. Invention is credited to William C. Allison, James P. LaCasse, Paul Andre Lefevre, Diane Scott, Alexander William Simpson.
Application Number | 20150273656 14/736568 |
Document ID | / |
Family ID | 48467319 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150273656 |
Kind Code |
A1 |
Allison; William C. ; et
al. |
October 1, 2015 |
POLISHING PAD WITH FOUNDATION LAYER AND POLISHING SURFACE LAYER
Abstract
Polishing pads with foundation layers and polishing surface
layers are described. In an example, a polishing pad for polishing
a substrate includes a foundation layer. A polishing surface layer
is bonded to the foundation layer. Methods of fabricating polishing
pads with a polishing surface layer bonded to a foundation layer
are also described.
Inventors: |
Allison; William C.;
(Beaverton, OR) ; Scott; Diane; (Portland, OR)
; Lefevre; Paul Andre; (Portland, OR) ; LaCasse;
James P.; (Portland, OR) ; Simpson; Alexander
William; (Hillsboro, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Allison; William C.
Scott; Diane
Lefevre; Paul Andre
LaCasse; James P.
Simpson; Alexander William |
Beaverton
Portland
Portland
Portland
Hillsboro |
OR
OR
OR
OR
OR |
US
US
US
US
US |
|
|
Family ID: |
48467319 |
Appl. No.: |
14/736568 |
Filed: |
June 11, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13306845 |
Nov 29, 2011 |
9067297 |
|
|
14736568 |
|
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Current U.S.
Class: |
451/527 |
Current CPC
Class: |
B24B 37/24 20130101;
B24B 37/205 20130101; B24D 18/0009 20130101; B24D 11/001 20130101;
B24B 37/16 20130101; B24B 37/22 20130101; B24B 37/26 20130101 |
International
Class: |
B24B 37/24 20060101
B24B037/24; B24B 37/22 20060101 B24B037/22; B24B 37/26 20060101
B24B037/26; B24B 37/20 20060101 B24B037/20 |
Claims
1. A polishing pad for polishing a substrate, the polishing pad
comprising: a foundation layer having a first hardness; a polishing
surface layer bonded directly to the foundation layer, the
polishing surface layer having a second hardness less than the
first hardness; and an aperture disposed in the polishing pad,
through the polishing surface layer and the foundation layer.
2. The polishing pad of claim 1, wherein the polishing surface
layer comprises a continuous layer portion with a plurality of
polishing features protruding there from, the continuous layer
portion bonded directly to the foundation layer.
3. The polishing pad of claim 1, wherein the polishing surface
layer comprises a plurality of discrete polishing protrusions
bonded directly to the foundation layer.
4. The polishing pad of claim 1, wherein the polishing surface
layer is covalently bonded to the foundation layer.
5. The polishing pad of claim 1, wherein the foundation layer and
the polishing surface layer have a peel resistance sufficient to
withstand a shear force applied during the useful lifetime of the
polishing pad.
6. The polishing pad of claim 1, wherein the foundation layer has a
surface roughness greater than approximately 1 micrometer Ra (root
mean square) where the polishing surface layer is bonded directly
to the foundation layer.
7. The polishing pad of claim 6, wherein the surface roughness is
approximately in the range of 5-10 micrometers Ra (root mean
square).
8. The polishing pad of claim 1, wherein the foundation layer has a
smooth surface with a surface roughness less than approximately 1
micrometer Ra (root mean square) where the polishing surface layer
is bonded directly to the foundation layer.
9. The polishing pad of claim 8, wherein the polishing surface
layer comprises a material formed from polyurethane.
10. The polishing pad of claim 1, wherein the foundation layer has
an energy loss factor of less than approximately 100 KEL at 1/Pa at
40.degree. C.
11. The polishing pad of claim 1, wherein the foundation layer has
a compressibility of less than approximately 1% under a central
pressure of 5 PSI.
12. The polishing pad of claim 1, wherein the foundation layer has
a hardness greater than approximately 75 Shore D.
13. The polishing pad of claim 1, wherein the foundation layer
comprises a polycarbonate material.
14. The polishing pad of claim 1, wherein the foundation layer
comprises a material selected from the group consisting of an epoxy
board material and a metal sheet.
15. The polishing pad of claim 1, wherein the polishing surface
layer has an energy loss factor of greater than approximately 1000
KEL at 1/Pa at 40.degree. C.
16. The polishing pad of claim 1, wherein the polishing surface
layer has a compressibility of greater than approximately 0.1%
under a central pressure of 5 PSI.
17. The polishing pad of claim 1, wherein the polishing surface
layer has a hardness less than approximately 70 Shore D.
18. The polishing pad of claim 1, wherein the polishing surface
layer is a homogeneous polishing surface layer.
19. The polishing pad of claim 18, wherein the homogeneous
polishing surface layer comprises a thermoset polyurethane
material.
20. The polishing pad of claim 1, wherein the polishing surface
layer has a pore density of closed cell pores approximately in the
range of 6% - 50% total void volume.
21. The polishing pad of claim 1, wherein the foundation layer has
an energy loss factor of less than approximately 100 KEL at 1/Pa at
40.degree. C., wherein the polishing surface layer has an energy
loss factor of greater than approximately 1000 KEL at 1/Pa at
40.degree. C., and wherein the foundation layer and the polishing
surface layer together have an energy loss factor of less than
approximately 100 KEL at 1/Pa at 40.degree. C.
22. The polishing pad of claim 1, wherein the foundation layer has
a hardness approximately in the range of 70-90 Shore D, and the
polishing surface layer has a hardness approximately in the range
of 50-60 Shore D.
23. The polishing pad of claim 1, wherein the foundation layer has
a hardness approximately in the range of 70-90 Shore D, and the
polishing surface layer has a hardness approximately in the range
of 20-50 Shore D.
24. The polishing pad of claim 1, wherein the polishing surface
layer has a first modulus of elasticity, and the foundation layer
has a second modulus of elasticity greater than approximately 10
times the first modulus of elasticity.
25. The polishing pad of claim 24, wherein the polishing surface
layer has a first modulus of elasticity, and the foundation layer
has a second modulus of elasticity greater than approximately 100
times the first modulus of elasticity.
26. The polishing pad of claim 1, wherein the polishing surface
layer has a thickness approximately in the range of 2-50 mils, and
the foundation layer has a thickness of greater than approximately
20 mils.
27. The polishing pad of claim 26, wherein the thickness of the
foundation layer is greater than the thickness of the polishing
surface layer.
28. The polishing pad of claim 1, wherein the foundation layer has
a thickness and hardness relative to the thickness and hardness of
the polishing surface layer sufficient to dictate the bulk
polishing characteristics of the polishing pad.
29. The polishing pad of claim 1, wherein the foundation layer is
sufficiently thick for the polishing pad to provide die-level
polishing planarity, but sufficiently thin for the polishing pad to
provide wafer-level polishing uniformity.
30. The polishing pad of claim 1, further comprising: a detection
region disposed in the foundation layer.
31. The polishing pad of claim 1, further comprising: an adhesive
sheet disposed on a back surface of the foundation layer but not in
the aperture, the adhesive sheet providing an impermeable seal for
the aperture at the back surface of the foundation layer.
32. The polishing pad of claim 1, further comprising: a sub pad
having a third hardness less than the first hardness, wherein the
foundation layer is disposed proximate to the sub pad.
33. The polishing pad of claim 32, wherein the foundation layer has
a hardness approximately in the range of 70-90 Shore D, the
polishing surface layer has a hardness approximately in the range
of 20-60 Shore D, and the sub pad has a hardness less than
approximately 90 Shore A.
34. The polishing pad of claim 32, wherein the polishing pad
provides die-level polishing planarity and wafer-level polishing
uniformity.
35. The polishing pad of claim 1, wherein the foundation layer
comprises a stack of sub layers.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/306,845, filed on Nov. 29, 2011, the entire
contents of which are hereby incorporated by reference herein.
TECHNICAL FIELD
[0002] Embodiments of the present invention are in the field of
chemical mechanical polishing (CMP) and, in particular, polishing
pads with foundation layers and polishing surface layers.
BACKGROUND
[0003] Chemical-mechanical planarization or chemical-mechanical
polishing, commonly abbreviated CMP, is a technique used in
semiconductor fabrication for planarizing a semiconductor wafer or
other substrate.
[0004] The process uses an abrasive and corrosive chemical slurry
(commonly a colloid) in conjunction with a polishing pad and
retaining ring, typically of a greater diameter than the wafer. The
polishing pad and wafer are pressed together by a dynamic polishing
head and held in place by a plastic retaining ring. The dynamic
polishing head is rotated during polishing. This approach aids in
removal of material and tends to even out any irregular topography,
making the wafer flat or planar. This may be necessary in order to
set up the wafer for the formation of additional circuit elements.
For example, this might be necessary in order to bring the entire
surface within the depth of field of a photolithography system, or
to selectively remove material based on its position. Typical
depth-of-field requirements are down to Angstrom levels for the
latest sub-50 nanometer technology nodes.
[0005] The process of material removal is not simply that of
abrasive scraping, like sandpaper on wood. The chemicals in the
slurry also react with and/or weaken the material to be removed.
The abrasive accelerates this weakening process and the polishing
pad helps to wipe the reacted materials from the surface. In
addition to advances in slurry technology, the polishing pad plays
a significant role in increasingly complex CMP operations.
[0006] However, additional improvements are needed in the evolution
of CMP pad technology.
SUMMARY
[0007] Embodiments of the present invention include polishing pads
with foundation layers and polishing surface layers.
[0008] In an embodiment, a polishing pad for polishing a substrate
includes a foundation layer having a first hardness. A polishing
surface layer is bonded directly to the foundation layer. The
polishing surface layer has a second hardness less than the first
hardness.
[0009] In another embodiment, a polishing pad for polishing a
substrate includes a foundation layer having a first hardness. A
polishing surface layer is bonded directly to the foundation layer.
The polishing surface layer has a second hardness equal to or
greater than the first hardness.
[0010] In another embodiment, a polishing pad for polishing a
substrate includes a foundation layer having an energy loss factor
of less than approximately 100 KEL at 1/Pa at 40.degree. C. A
polishing surface layer is attached to the foundation layer. The
polishing surface layer has an energy loss factor of greater than
approximately 1000 KEL at 1/Pa at 40.degree. C. The foundation
layer and the polishing surface layer together have an energy loss
factor of less than approximately 100 KEL at 1/Pa at 40.degree.
C.
[0011] In another embodiment, a polishing pad for polishing a
substrate includes a foundation layer having a first hardness. A
polishing surface layer is attached to the foundation layer. The
polishing surface layer has a second hardness less than the first
hardness and is composed of a thermoset material.
[0012] In another embodiment, a polishing pad for polishing a
substrate includes a nonporous foundation layer. A polishing
surface layer is bonded directly to the foundation layer. The
polishing surface layer has a pore density of closed cell
pores.
[0013] In another embodiment, a method of fabricating a polishing
pad for polishing a substrate includes providing, in a formation
mold, a foundation layer and a mixture formed from mixing a set of
polymerizable materials. A pattern of protrusions of the formation
mold is coupled with the mixture. With the pattern of protrusions
coupled with the mixture, the mixture is at least partially cured
to form a molded homogeneous polishing surface layer directly on
the foundation layer. The molded homogeneous polishing surface
layer includes a pattern of grooves corresponding to the pattern of
protrusions of the formation mold.
[0014] In another embodiment, a method of fabricating a polishing
pad for polishing a substrate includes providing, in a formation
mold, a foundation layer and a mixture formed from mixing a set of
polymerizable materials. A pattern of protrusions of the formation
mold is coupled with the mixture. With the pattern of protrusions
coupled with the mixture, the mixture is at least partially cured
to form a molded homogeneous polishing surface layer attached to
the foundation layer. The molded homogeneous polishing surface
layer includes a pattern of grooves corresponding to the pattern of
protrusions of the formation mold. The foundation layer having the
molded homogeneous polishing surface layer attached thereto is
removed from the base of the formation mold when the extent of
curing is sufficient to maintain geometry of the molded homogeneous
polishing surface layer but insufficient for the molded homogeneous
polishing surface layer to withstand mechanical stress.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 illustrates a cross-sectional view of a polishing pad
with a foundation layer and a polishing surface layer, in
accordance with an embodiment of the present invention.
[0016] FIG. 2 illustrates a cross-sectional view of another
polishing pad with a foundation layer and a polishing surface
layer, in accordance with an embodiment of the present
invention.
[0017] FIG. 3 illustrates a top-down view of a polishing pad with a
polishing surface layer including discrete linear segment
protrusions, in accordance with an embodiment of the present
invention.
[0018] FIG. 4 illustrates a top-down plan view of a polishing pad
with a polishing surface layer having an aperture and/or an
indication region, in accordance with an embodiment of the present
invention.
[0019] FIGS. 5A-5F illustrate cross-sectional views of operations
used in the fabrication of a polishing pad with a foundation layer
and a polishing surface layer, in accordance with an embodiment of
the present invention.
[0020] FIG. 6 illustrates a cross-sectional view of a polishing pad
with a grooved foundation layer and a polishing surface layer, in
accordance with an embodiment of the present invention.
[0021] FIG. 7 illustrates a cross-sectional view of another
polishing pad with a grooved foundation layer and a polishing
surface layer, in accordance with an embodiment of the present
invention.
[0022] FIG. 8 illustrates an isometric side-on view of a polishing
apparatus compatible with a polishing pad with a foundation layer
and a polishing surface layer, in accordance with an embodiment of
the present invention.
DETAILED DESCRIPTION
[0023] Polishing pads with foundation layers and polishing surface
layers are described herein. In the following description, numerous
specific details are set forth, such as specific polishing pad
compositions and designs, in order to provide a thorough
understanding of embodiments of the present invention. It will be
apparent to one skilled in the art that embodiments of the present
invention may be practiced without these specific details. In other
instances, well-known processing techniques, such as details
concerning the combination of a slurry with a polishing pad to
perform CMP of a semiconductor substrate, are not described in
detail in order to not unnecessarily obscure embodiments of the
present invention. Furthermore, it is to be understood that the
various embodiments shown in the figures are illustrative
representations and are not necessarily drawn to scale.
[0024] Polishing pads for CMP operations may have trade-offs in
performance such as a trade-off between across-wafer polishing
uniformity versus within die polishing uniformity. For example,
hard polishing pads may exhibit good die-level planarization, but
poor across-wafer uniformity. They may also scratch a substrate
being polished. On the other hand, soft polishing pads may exhibit
poor die-level planarization (e.g., they may cause dishing within
die), but good wafer-level uniformity. An approach to mitigating
the above performance trade-off may be to decouple within-wafer and
within-die polishing effects.
[0025] Conventional approaches to fabricating and using soft pads
may have limitations. For example, casted soft pads may offer low
defect characteristics but compromised planarization performance.
There may be a need for polishing pads that offer both low defect
characteristics yet high planarization performance during polishing
operations. Similarly, conventional approaches to fabricating and
using hard pads may have limitations. For example, faster gelling
speeds possibly inherent in harder urethane formulations may force
process compromises that impact pad uniformity and limit
formulation options. There may be a need for an approach suitable
to produce and implement hard pads that avoid such compromises.
Additionally, as noted above, it may be desirable to decouple the
properties of the polishing surface of a pad from its bulk
properties, such that the properties of each may be separately
optimized.
[0026] In accordance with an embodiment of the present inventions,
polishing pads with bulk or foundation material different from the
material of the polishing surface are described herein. Such
polishing pads may be fabricated or implemented in approaches
suitable to address the above described compromises made for
conventional pads. In one embodiment, a composite polishing pad
includes a foundation or bulk layer fabricated from a stable,
essentially non-compressible, inert material onto which a polishing
surface layer is disposed. A harder foundation layer may provide
support and strength for pad integrity while a softer polishing
surface layer may reduce scratching, enabling decoupling of the
material properties of the polishing layer and the remainder of the
polishing pad.
[0027] In a specific embodiment elaborated in greater detail below,
the planarization characteristics of a soft pad is made available
by producing a soft polishing surface layer on a stiff backer
material or foundation layer, such as a sheet of polycarbonate. For
example, in a particular embodiment, a 20 mil (thousandths of an
inch) thick polycarbonate sheet was placed on the casting base
portion of a pad-making mold and the pad formulation was dispensed
directly onto the sheet. The polishing pad was then processed
through molding, demolding and curing operations. The result was a
uniform pad, with good adhesion between a urethane polishing layer
and the polycarbonate support sheet.
[0028] In accordance with embodiments of the present invention,
approaches to mitigating the above described performance trade-off
include the formation of polishing pads having either a soft
continuous polishing surface layer or a soft polishing surface
layer composed of discrete protrusions bonded with a hard
foundation layer. Although the foregoing may be preferred, it is to
be understood that reverse arrangements, e.g., a hard polishing
surface layer disposed on a soft underlying foundation layer, are
also contemplated and described herein.
[0029] In a first aspect, a polishing pad is provided with a
continuous polishing surface layer. For example, FIG. 1 illustrates
a cross-sectional view of a polishing pad with a foundation layer
and a polishing surface layer, in accordance with an embodiment of
the present invention.
[0030] Referring to FIG. 1, a polishing pad 100 is provided for
polishing a substrate. The polishing pad 100 includes a foundation
layer 102 having a polishing side 104 and a back side 106. The
foundation layer 102 is composed of a material having a first
hardness. The polishing pad 100 also includes a polishing surface
layer 108 bonded with the foundation layer 102. The polishing
surface layer 108 is composed of a material having a second
hardness. In an embodiment, the polishing surface layer 108
includes a continuous layer portion 108A with a plurality of
polishing features 108B protruding there from, as depicted in FIG.
1. It is the continuous layer portion 108A that is bonded with the
foundation layer 102. In a preferred, but not limiting, embodiment,
the second hardness (the hardness of the polishing surface layer
108) is less than the first hardness (the hardness of the
foundation layer 102).
[0031] In a second aspect, a polishing pad is provided with a
non-continuous polishing surface layer. For example, FIG. 2
illustrates a cross-sectional view of another polishing pad with a
foundation layer and a polishing surface layer, in accordance with
another embodiment of the present invention.
[0032] Referring to FIG. 2, a polishing pad 200 is provided for
polishing a substrate. The polishing pad 200 includes a foundation
layer 202 having a polishing side 204 and a back side 206. The
foundation layer 202 is composed of a material having a first
hardness. The polishing pad 200 also includes a polishing surface
layer 208 bonded with the foundation layer 202. The polishing
surface layer 208 is composed of a material having a second
hardness. In an embodiment, the polishing surface layer 208
includes only a plurality of discrete protrusions or polishing
features protruding there from, as depicted in FIG. 2. It is the
discrete polishing protrusions that are bonded with the foundation
layer 202. In a preferred, but not limiting, embodiment, the second
hardness (the hardness of the polishing surface layer 208 of
discrete polishing protrusions) is less than the first hardness
(the hardness of the foundation layer 202).
[0033] It is noted that the polishing surface layers 108 or 208 are
described as being "bonded with" foundation layers 102 or 202,
respectively. In a first such embodiment, the polishing surface
layers 108 or 208 are bonded directly to foundation layers 102 or
202, respectively. That is, the polishing surface layers 108 or 208
are in direct contact with foundation layers 102 or 202,
respectively, as depicted in FIGS. 1 and 2. In one embodiment,
then, "bonded directly to" describes direct contact with no
intervening layers (such as pressure sensitive adhesive layers) or
otherwise glue-like or adhesive films. It may be preferable that
the polishing surface layers 108 or 208 are bonded directly to
foundation layers 102 or 202, respectively, so that only the
polishing surface layer and corresponding foundation layer dictate
the polishing performance of a pad composed there of.
[0034] In a specific such embodiment, the polishing surface layer
108 or 208 is covalently bonded to the corresponding foundation
layer 102 or 202. In an embodiment, the term "covalently bonded"
refers to arrangements where atoms from a first material (e.g., the
material of a polishing surface layer) are cross-linked or share
electrons with atoms from a second material (e.g., the material of
a foundation layer) to effect actual chemical bonding. Covalent
bonding is distinguished from mechanical bonding, such as bonding
through screws, nails, glues, or other adhesives. In another
specific embodiment, the polishing surface layer 108 or 208 is not
covalently bonded, but is rather only electrostatically bonded, to
the corresponding foundation layer 102 or 202. Such electrostatic
bonding may involve van der Waals type interactions between the
foundation layer and the polishing surface layer.
[0035] Other direct bonding may be preferred, in a second such
embodiment, the polishing surface layers 108 or 208 are attached to
foundation layers 102 or 202, respectively. That is, the polishing
surface layers 108 or 208 and corresponding foundation layers 102
or 202, respectively, may include intervening layers (such as
pressure sensitive adhesive layers) or otherwise glue-like or
adhesive films. Thus, "attached to" describes both direct contact
with no intervening layers (such as pressure sensitive adhesive
layers) or otherwise glue-like or adhesive films, and also
describes situations where such intervening layers are used between
a foundation layer and corresponding polishing surface layer.
[0036] In either of the above cases, peel resistance may provide an
indication of the strength and extent to which a polishing surface
layer is bonded with a foundation layer. In an embodiment, the
foundation layer 102 or 202 and the corresponding polishing surface
layer 108 or 208 have a peel resistance sufficient to withstand a
shear force applied during the useful lifetime of the polishing
pad.
[0037] In an embodiment, a surface roughness is used at the
interface of a polishing surface layer and a foundation layer to
enhance bond strength of these two portions of a polishing pad. In
one such embodiment, the foundation layer 102 or 202 has a surface
roughness greater than approximately 1 micrometer Ra (root mean
square) where the corresponding polishing surface layer 108 or 208
is bonded directly to the foundation layer (e.g., at interface 104
or 204). In a specific such embodiment, the surface roughness is
approximately in the range of 5-10 micrometers Ra (root mean
square).
[0038] However, in another embodiment, substantial surface
roughness is not included and the interface of a polishing surface
layer and a foundation layer is particularly smooth. The strength
of such a smooth interface may be independent of surface roughness
or may not need further strengthening by the inclusion of such
surface roughness. In one such embodiment, the foundation layer 102
or 202 has a smooth surface with a surface roughness less than
approximately 1 micrometer Ra (root mean square) where the
corresponding polishing surface layer 108 or 208 is bonded directly
to the foundation layer (e.g., at interface 104 or 204). The
decision or need to include or exclude roughness at an interface of
a foundation layer and polishing surface layer may depend on the
pristine nature of the interface (e.g., exclusion of impurities
such as oil films) or on the nature of the materials at the
interface. For example, in a particular such embodiment, the
polishing surface layer 108 or 208 at a smooth interface is
composed of a material formed from polyurethane.
[0039] The materials of polishing surface layer 108 or 208 and
corresponding foundation layer 102 or 202 may each have defined
parameters suitable to provide desired polishing characteristics,
either as individual components or collectively for the polishing
pad as an entirety. For example, in one such embodiment the
polishing surface layer 108 or 208 and corresponding foundation
layer 102 or 202 differ in their energy loss factor, or KEL. KEL is
parameter for predicting polishing performance. ASTM D4092-90
("Standard Terminology Relating to Dynamic Mechanical Measurements
of Plastics") defines this parameter as the energy per unit volume
lost in each deformation cycle. In other words, it is a measure of
the area within the stress-strain hysteresis loop. The Energy Loss
Factor (KEL) is a function of both tan .delta. and the elastic
storage modulus (E') and may be defined by the following equation:
KEL=tan .delta.*10.sup.12/[E'*(1+tan .delta..sup.2)] where E' is in
Pascals. The ratio of elastic stress to strain is the storage (or
elastic) modulus and the ratio of the viscous stress to strain is
the loss (or viscous) modulus. When testing is performed in
tension, flex, or compression, E' and E'' designate the storage and
loss modulus, respectively. The ratio of the loss modulus to the
storage modulus is the tangent of the phase angle shift (.delta.)
between the stress and the strain. Thus, E''/E'=tan .delta. and is
a measure of the damping ability of the material. In an embodiment,
the foundation layer 102 or 202 has an energy loss factor of less
than approximately 100 KEL at 1/Pa at 40.degree. C., e.g., of
approximately 7. In an embodiment, the polishing surface layer 108
or 208 has an energy loss factor of greater than approximately 1000
KEL at 1/Pa at 40.degree. C., e.g., of approximately 8000. In an
embodiment, the foundation layer 102 or 202 has an energy loss
factor of less than approximately 100 KEL at 1/Pa at 40.degree. C.,
the polishing surface layer 108 or 208 has an energy loss factor of
greater than approximately 1000 KEL at 1/Pa at 40.degree. C., and
the foundation layer 102 of 202 and the corresponding polishing
surface layer 108 or 208 together have an energy loss factor of
less than approximately 100 KEL at 1/Pa at 40.degree. C.
[0040] In another example, the materials of polishing surface layer
108 or 208 and corresponding foundation layer 102 or 202 may each
have defined compressibility of elasticity suitable to provide
desired polishing characteristics, either as individual components
or collectively for the polishing pad as an entirety. In an
embodiment, the foundation layer 102 or 202 has a compressibility
of less than approximately 1% under a central pressure of 5 PSI. In
an embodiment, the polishing surface layer 108 or 208 has a
compressibility of greater than approximately 0.1% under a central
pressure of 5 PSI. In an embodiment, the polishing surface layer
108 or 208 has a first modulus of elasticity, and the corresponding
foundation layer 102 or 202 has a second modulus of elasticity
greater than approximately 10 times the first modulus of
elasticity, e.g. for a relatively harder polishing surface on a
hard foundation layer. In another embodiment, however, the
polishing surface layer 108 or 208 has a first modulus of
elasticity, and the corresponding foundation layer 102 or 202 has a
second modulus of elasticity greater than approximately 100 times
the first modulus of elasticity, e.g. for a relatively softer
polishing surface on a hard foundation layer.
[0041] In another example, the materials of polishing surface layer
108 or 208 and corresponding foundation layer 102 or 202 may each
have defined hardness suitable to provide desired polishing
characteristics, either as individual components or collectively
for the polishing pad as an entirety. In an embodiment, the
foundation layer 102 or 202 has a hardness greater than
approximately 75 Shore D, e.g., approximately 84-85 Shore D for a
polycarbonate foundation layer. In an embodiment, the polishing
surface layer 108 or 208 has a hardness less than approximately 70
Shore D and, preferably, less than approximately 60 Shore D. In an
embodiment, the foundation layer 102 or 202 has a hardness
approximately in the range of 70-90 Shore D, and the corresponding
polishing surface layer 108 or 208 has a hardness approximately in
the range of 50-60 Shore D, e.g., for a hard polyurethane polishing
surface layer. In another embodiment, the foundation layer 102 or
202 has a hardness approximately in the range of 70-90 Shore D, and
the corresponding polishing surface layer 108 or 208 has a hardness
approximately in the range of 20-50 Shore D, e.g., for a soft
polyurethane polishing surface layer.
[0042] In another example, the materials of polishing surface layer
108 or 208 and corresponding foundation layer 102 or 202 may each
have defined composition suitable to provide desired polishing
characteristics, either as individual components or collectively
for the polishing pad as an entirety. In an embodiment, the
foundation layer 102 or 202 is composed of a polycarbonate
material. In one such embodiment, the polycarbonate material is
composed of a stack of several discrete layers (sub layers) of
polycarbonate or is composed of a single, continuous, layer of
polycarbonate. In another embodiment, the foundation layer 102 or
202 is composed of a material such as, but not limited to, an epoxy
board material or a metal sheet.
[0043] In an embodiment, the polishing surface layer 108 or 208 is
a homogeneous polishing surface layer. In one such embodiment, the
homogeneous polishing surface layer is composed of a thermoset
polyurethane material. For example, in a specific embodiment, the
homogeneous body is composed of a thermoset, closed cell
polyurethane material. In an embodiment, the term "homogeneous" is
used to indicate that the composition of a thermoset, closed cell
polyurethane material is consistent throughout the entire
composition of the body. For example, in an embodiment, the term
"homogeneous" excludes polishing pad bodies composed of, e.g.,
impregnated felt or a composition (composite) of multiple layers of
differing material. In an embodiment, the term "thermoset" is used
to indicate a polymer material that irreversibly cures, e.g., the
precursor to the material changes irreversibly into an infusible,
insoluble polymer network by curing. For example, in an embodiment,
the term "thermoset" excludes polishing pads composed of, e.g.,
"thermoplast" materials or "thermoplastics"--those materials
composed of a polymer that turns to a liquid when heated and
returns to a very glassy state when cooled sufficiently. It is
noted that polishing pads made from thermoset materials are
typically fabricated from lower molecular weight precursors
reacting to form a polymer in a chemical reaction, while pads made
from thermoplastic materials are typically fabricated by heating a
pre-existing polymer to cause a phase change so that a polishing
pad is formed in a physical process. Polyurethane thermoset
polymers may be selected for fabricating polishing pads described
herein based on their stable thermal and mechanical properties,
resistance to the chemical environment, and tendency for wear
resistance. In an embodiment, although the polishing surface layer
108 or 208 is composed of a thermoset material, the corresponding
foundation layer 102 or 202 is composed of a thermoplastic
material, such as a polycarbonate.
[0044] The materials of polishing surface layer 108 or 208 may be
molded. The term "molded" may be used to indicate that the
polishing surface layer is formed in a formation mold, as described
in more detail below in association with FIGS. 5A-5F. In an
embodiment, the molded polishing surface layer 108 or 208, upon
conditioning and/or polishing, has a polishing surface roughness
approximately in the range of 1-5 microns root mean square. In one
embodiment, the molded polishing surface layer 108 or 208, upon
conditioning and/or polishing, has a polishing surface roughness of
approximately 2.35 microns root mean square. In an embodiment, the
molded polishing surface layer 108 or 208 has a storage modulus at
25 degrees Celsius approximately in the range of 30-500 megaPascals
(MPa). In another embodiment, the molded polishing surface layer
108 or 208 has a storage modulus at 25 degrees Celsius
approximately less than 30 megaPascals (MPa).
[0045] The materials of polishing surface layer 108 or 208 may
include pore-forming features. In an embodiment, the polishing
surface layer 108 or 208 has a pore density of closed cell pores
approximately in the range of 6%-50% total void volume. In one
embodiment, the plurality of closed cell pores is a plurality of
porogens. For example, the term "porogen" may be used to indicate
micro- or nano-scale spherical or somewhat spherical particles with
"hollow" centers. The hollow centers are not filled with solid
material, but may rather include a gaseous or liquid core. In one
embodiment, the plurality of closed cell pores is composed of
pre-expanded and gas-filled EXPANCEL.TM. distributed throughout
(e.g., as an additional component in) a polishing surface layer of
a polishing pad. In a specific embodiment, the EXPANCEL.TM. is
filled with pentane. In an embodiment, each of the plurality of
closed cell pores has a diameter approximately in the range of
10-100 microns. In an embodiment, the plurality of closed cell
pores includes pores that are discrete from one another. This is in
contrast to open cell pores which may be connected to one another
through tunnels, such as the case for the pores in a common sponge.
In one embodiment, each of the closed cell pores includes a
physical shell, such as a shell of a porogen, as described above.
In another embodiment, however, each of the closed cell pores does
not include a physical shell. In an embodiment, the plurality of
closed cell pores is distributed essentially evenly throughout a
thermoset polyurethane material of a homogeneous polishing surface
layer.
[0046] In an embodiment, although the polishing surface layer 108
or 208 includes pore-forming features, the corresponding foundation
layer 102 or 202 does not and is non-porous.
[0047] In an embodiment, polishing pads described herein, such as
polishing pads 100 or 200, include a polishing surface layer 108 or
208 that is opaque. In one embodiment, the term "opaque" is used to
indicate a material that allows approximately 10% or less visible
light to pass. In one embodiment, the polishing surface layer 108
or 208 is opaque in most part, or due entirely to, the inclusion of
an opacifying particle filler, such as a lubricant, throughout
(e.g., as an additional component in) the polishing surface layer
108 or 208. In a specific embodiment, the opacifying particle
filler is a material such as, but not limited to boron nitride,
cerium fluoride, graphite, graphite fluoride, molybdenum sulfide,
niobium sulfide, talc, tantalum sulfide, tungsten disulfide, or
Teflon.RTM..
[0048] In another example, the materials of polishing surface layer
108 or 208 and corresponding foundation layer 102 or 202 may each
have defined dimensions suitable to provide desired polishing
characteristics, either as individual components or collectively
for the polishing pad as an entirety. In an embodiment, the
polishing surface layer 108 or 208 has a thickness (a or a' in FIG.
1 or 2, respectively) approximately in the range of 2-50 mils, and
the corresponding foundation layer 102 or 202 has a thickness (b or
b' in FIG. 1 or 2, respectively) of greater than approximately 20
mils. In an embodiment, the thickness (b or b') of the foundation
layer 102 or 202 is greater than the thickness (a or a') of the
polishing surface layer 108 or 208. In an embodiment, the
foundation layer 102 or 202 has a thickness (b or b') and hardness
relative to the thickness (a or a') and hardness of the
corresponding polishing surface layer 108 or 208 sufficient to
dictate the bulk polishing characteristics of the corresponding
polishing pad 100 or 200. In an embodiment, the foundation layer
102 or 202 is sufficiently thick for the corresponding polishing
pad 100 or 200 to provide die-level polishing planarity, but
sufficiently thin for the polishing pad to provide wafer-level
polishing uniformity.
[0049] In an embodiment, polishing pad 100 or 200 further includes
a sub pad, e.g., a conventional sub pad as known in the CMP art.
The foundation layer 102 or 202 is disposed proximate to the sub
pad. In one such embodiment, the sub pad has a hardness less than
the hardness of the corresponding foundation layer 102 or 202. In
one such embodiment, the sub pad is composed of a material such as,
but not limited to, foam, rubber, fiber, felt or a highly porous
material. In an embodiment, the foundation layer 102 or 202 has a
hardness approximately in the range of 70-90 Shore D, the
corresponding polishing surface layer 108 or 208 has a hardness
approximately in the range of 20-60 Shore D, and a corresponding
sub pad has a hardness less than approximately 90 Shore A. In an
embodiment, a polishing pad including a polishing surface layer 108
or 208, the corresponding foundation layer 102 or 202, and a
corresponding sub pad provides die-level polishing planarity and
wafer-level polishing uniformity for CMP operations.
[0050] Although the above embodiments primarily focus on polishing
pads with a polishing surface layer softer than a corresponding,
underlying, foundation layer, other arrangements are contemplated
within the spirit and scope of embodiments of the present
invention. For example, in an embodiment, a polishing pad for
polishing a substrate includes a foundation layer having a first
hardness. A polishing surface layer is bonded with the foundation
layer. The polishing surface layer has a second hardness equal to
or greater than the first hardness. In one embodiment, the
polishing surface layer is directly bonded to, and is covalently
bonded to, the foundation layer. In one embodiment, the foundation
layer and the polishing surface layer have a peel resistance
sufficient to withstand a shear force applied during the useful
lifetime of the polishing pad. In one embodiment, the polishing
surface layer is composed of a continuous layer portion with
plurality of polishing features protruding there from, the
continuous layer portion bonded directly to the foundation layer.
In one embodiment, the polishing surface layer is composed of a
plurality of discrete polishing protrusions bonded directly to the
foundation layer.
[0051] In another example, in an embodiment, a polishing pad for
polishing a substrate includes a foundation layer having an energy
loss factor of less than approximately 100 KEL at 1/Pa at
40.degree. C. A polishing surface layer is bonded with the
foundation layer. The polishing surface layer has an energy loss
factor of greater than approximately 1000 KEL at 1/Pa at 40.degree.
C. The foundation layer and the polishing surface layer together
have an energy loss factor of less than approximately 100 KEL at
1/Pa at 40.degree. C. In one embodiment, the polishing surface
layer is composed of a continuous layer portion with plurality of
polishing features protruding there from, the continuous layer
portion attached to the foundation layer. In one embodiment, the
polishing surface layer is composed of a plurality of discrete
polishing protrusions attached to the foundation layer. In one
embodiment, the polishing surface layer is composed of a thermoset
polyurethane material.
[0052] In another example, in an embodiment, a polishing pad for
polishing a substrate includes a foundation layer having a first
hardness. A polishing surface layer is bonded with the foundation
layer. The polishing surface layer has a second hardness less than
the first hardness and is composed of a thermoset material. In one
embodiment, the polishing surface layer is a homogeneous polishing
surface layer. In one embodiment, the thermoset material is
polyurethane. In one embodiment, the foundation layer has a
hardness approximately in the range of 70-90 Shore D, and the
polishing surface layer has a hardness approximately in the range
of 50-60 Shore D. In one embodiment, the foundation layer has a
hardness approximately in the range of 70-90 Shore D, and the
polishing surface layer has a hardness approximately in the range
of 20-50 Shore D. In one embodiment, the polishing surface layer is
composed of a continuous layer portion with plurality of polishing
features protruding there from, the continuous layer portion
attached to the foundation layer. In one embodiment, the polishing
surface layer is composed of a plurality of discrete polishing
protrusions attached to the foundation layer. In one embodiment,
the polishing surface layer has a pore density of closed cell pores
approximately in the range of 6%-50% total void volume.
[0053] In another example, in an embodiment, a polishing pad for
polishing a substrate includes a nonporous foundation layer. A
polishing surface layer is bonded with the foundation layer. The
polishing surface layer has a pore density of closed cell pores. In
one embodiment, the pore density of closed cell pores is
approximately in the range of 6%-50% total void volume. In one
embodiment, the polishing surface layer is composed of a continuous
layer portion with plurality of polishing features protruding there
from, the continuous layer portion bonded directly to the
foundation layer. In one embodiment, the polishing surface layer is
composed of a plurality of discrete polishing protrusions bonded
directly to the foundation layer.
[0054] In another aspect, the polishing surface layer 108 or 208
may have a pattern suitable for polishing during a CMP operation.
In a first general example, some embodiments of the present
invention include a plurality of protrusions having a pattern of
linear features. In a specific such example, FIG. 3 illustrates a
top-down view of a polishing pad 300 with a polishing surface layer
including discrete linear segment protrusions 302, in accordance
with an embodiment of the present invention. The discrete linear
segment protrusions shown are essentially orthogonal to radii of
the polishing surface. It is to be understood, however, that
embodiments of the present invention may also include discrete
linear segments that are not precisely orthogonal to radii of the
polishing surface. In such embodiments, the discrete linear
segments may form a portion of a, but not a complete, concentric or
approximately concentric polygon arrangement. The relative
association with the corresponding radius is not precisely 90
degrees but rather, perhaps, a fraction of a degree to a few
degrees off of 90 degrees. Nonetheless, such near-orthogonal or
approximately orthogonal discrete linear segments are considered to
be within the spirit and scope of the present invention.
[0055] In a second general example, some embodiments of the present
invention include a plurality of protrusions having a pattern of
discrete curved features. In a specific such example, discrete
arc-shaped protrusions are included. Other specific such
embodiments include, but are not limited to, a plurality of partial
circumferential protrusions disposed on a substantially circular
polishing pad.
[0056] In a third general example, some embodiments of the present
invention include a plurality of protrusions having a pattern of
discrete tiles. In a specific such embodiment, discrete hexagonal
tile protrusions are included. Other specific such embodiments
include, but are not limited to, pluralities of circular tiles,
oval tiles, square tiles, rectangular tiles, or a combination
thereof.
[0057] Although the above three general examples are defined in
terms of protrusions (e.g., the highest points of a patterned
polishing surface layer), the polishing surface layers may also or
alternatively be defined in terms of grooves (e.g., the lowest
points of a patterned polishing surface layer). Individual grooves
may be from about 4 to about 100 mils deep at any given point on
each groove. In some embodiments, the grooves are about 10 to about
50 mils deep at any given point on each groove. The grooves may be
of uniform depth, variable depth, or any combinations thereof. In
some embodiments, the grooves are all of uniform depth. For
example, the grooves of a groove pattern may all have the same
depth. In some embodiments, some of the grooves of a groove pattern
may have a certain uniform depth while other grooves of the same
pattern may have a different uniform depth. For example, groove
depth may increase with increasing distance from the center of the
polishing pad. In some embodiments, however, groove depth decreases
with increasing distance from the center of the polishing pad. In
some embodiments, grooves of uniform depth alternate with grooves
of variable depth.
[0058] Individual grooves may be from about 2 to about 100 mils
wide at any given point on each groove. In some embodiments, the
grooves are about 15 to about 50 mils wide at any given point on
each groove. The grooves may be of uniform width, variable width,
or any combinations thereof. In some embodiments, the grooves of a
groove pattern are all of uniform width. In some embodiments,
however, some of the grooves of a groove pattern have a certain
uniform width, while other grooves of the same pattern have a
different uniform width. In some embodiments, groove width
increases with increasing distance from the center of the polishing
pad. In some embodiments, groove width decreases with increasing
distance from the center of the polishing pad. In some embodiments,
grooves of uniform width alternate with grooves of variable
width.
[0059] In accordance with the previously described depth and width
dimensions, individual grooves may be of uniform volume, variable
volume, or any combinations thereof. In some embodiments, the
grooves are all of uniform volume. In some embodiments, however,
groove volume increases with increasing distance from the center of
the polishing pad. In some other embodiments, groove volume
decreases with increasing distance from the center of the polishing
pad. In some embodiments, grooves of uniform volume alternate with
grooves of variable volume.
[0060] Grooves of the groove patterns described herein may have a
pitch from about 30 to about 1000 mils. In some embodiments, the
grooves have a pitch of about 125 mils. For a circular polishing
pad, groove pitch is measured along the radius of the circular
polishing pad. In CMP belts, groove pitch is measured from the
center of the CMP belt to an edge of the CMP belt. The grooves may
be of uniform pitch, variable pitch, or in any combinations
thereof. In some embodiments, the grooves are all of uniform pitch.
In some embodiments, however, groove pitch increases with
increasing distance from the center of the polishing pad. In some
other embodiments, groove pitch decreases with increasing distance
from the center of the polishing pad. In some embodiments, the
pitch of the grooves in one sector varies with increasing distance
from the center of the polishing pad while the pitch of the grooves
in an adjacent sector remains uniform. In some embodiments, the
pitch of the grooves in one sector increases with increasing
distance from the center of the polishing pad while the pitch of
the grooves in an adjacent sector increases at a different rate. In
some embodiments, the pitch of the grooves in one sector increases
with increasing distance from the center of the polishing pad while
the pitch of the grooves in an adjacent sector decreases with
increasing distance from the center of the polishing pad. In some
embodiments, grooves of uniform pitch alternate with grooves of
variable pitch. In some embodiments, sectors of grooves of uniform
pitch alternate with sectors of grooves of variable pitch.
[0061] In another aspect, a polishing pad with a polishing surface
layer and corresponding foundation layer further includes a
detection region for use with, e.g., an eddy current detection
system. For example, FIG. 4 illustrates a top-down plan view of a
polishing pad with a polishing surface layer having an aperture
and/or an indication region, in accordance with an embodiment of
the present invention.
[0062] Referring to FIG. 4, the polishing surface layer 402 of
polishing pad 400 includes an indication region 404 indicating the
location of a detection region disposed in the back surface of the
polishing pad 400, e.g., in the back surface of a corresponding
foundation layer. In one embodiment, the indication region 404
interrupts a pattern of protrusions 406 with a second pattern of
protrusions 408, as depicted in FIG. 4. Examples of suitable
detection regions, such as eddy current detection regions, are
described in U.S. patent application Ser. 12/895,465 filed on Sep.
30, 2010, assigned to NexPlanar Corporation.
[0063] In another aspect, a polishing pad with a polishing surface
layer and corresponding foundation layer further includes an
aperture disposed in the polishing pad. For example, referring
again to FIG. 4, an aperture 410 is disposed in the polishing
surface layer 402 of polishing pad 400. As depicted in FIG. 4, the
aperture 410 interrupts the pattern of protrusions 406. In an
embodiment, the aperture 410 is disposed in the polishing pad 400,
through the polishing surface layer 402 and a corresponding
foundation layer. An adhesive sheet is disposed on a back surface
of the foundation layer but not in the aperture. The adhesive sheet
provides an impermeable seal for the aperture 410 at the back
surface of the foundation layer. Examples of apertures are
described in U.S. patent application Ser. No. 13/184,395 filed on
Jul. 15, 2011, assigned to NexPlanar Corporation.
[0064] In another aspect, polishing pads with foundation layers and
corresponding polishing surface layers may be fabricated in a
molding process. For example, such multi-layer (e.g., surface
polishing layer plus underlying foundation layer) polishing pads as
those described above may be fabricated with a molding process to
facilitate direct bonding between a surface polishing layer and an
underlying foundation layer. FIGS. 5A-5F illustrate cross-sectional
views of operations used in the fabrication of a polishing pad with
a foundation layer and a polishing surface layer, in accordance
with an embodiment of the present invention.
[0065] Referring to FIG. 5A, a formation mold 500 is provided. A
foundation layer 502 is then provided in the formation mold 500.
The foundation layer 502 may be composed of a material or have
properties similar or the same as the materials and properties
described above for foundation layers 102 and 202. In an
embodiment, the material of foundation layer 502 is in a completed
form, e.g., fully cured, when provided in the formation mold 502.
For example, in an embodiment, the foundation layer 502 is cut from
a larger sheet of the same material and sized for formation mold
500. In one embodiment, the foundation layer 502 is placed in a
base of the formation mold 500, as depicted in FIG. 5B. In an
embodiment, providing the foundation layer 502 in the formation
mold 500 includes first roughening a surface of the foundation
layer 502, e.g., roughening the surface upon which a polishing
surface layer will ultimately be formed. In one such embodiment,
the roughening is performed by a technique such as, but not limited
to, plasma treatment, mechanical treatment, or chemical
treatment.
[0066] A mixture is formed from mixing a set of polymerizable
materials. For example, referring to both FIGS. 5C and 5D a
pre-polymer 504 and a curative 505 are mixed to form a mixture 506
in the formation mold 500. In an embodiment, forming the mixture
506 includes providing the mixture 506 in the base of the formation
mold 500, on the foundation layer 502, as depicted in FIG. 5D. In
an embodiment, mixing the pre-polymer 504 and the curative 505
includes mixing an isocyanate and an aromatic diamine compound,
respectively. In one embodiment, the mixing further includes adding
an opacifying particle filler to the pre-polymer 504 and the
curative 505 to ultimately provide an opaque molded polishing
surface layer of a polishing pad. In a specific embodiment, the
opacifying particle filler is a material such as, but not limited
to boron nitride, cerium fluoride, graphite, graphite fluoride,
molybdenum sulfide, niobium sulfide, talc, tantalum sulfide,
tungsten disulfide, or Teflon.
[0067] In an embodiment, the mixture 506 is used to ultimately form
a molded polishing surface layer composed of a thermoset, closed
cell polyurethane material. In one embodiment, the mixture 506 is
used to ultimately form a hard polishing surface layer and only a
single type of curative is used. In another embodiment, the mixture
506 is used to ultimately form a soft polishing surface layer and a
combination of a primary and a secondary curative is used. For
example, in a specific embodiment, the pre-polymer includes a
polyurethane precursor, the primary curative includes an aromatic
diamine compound, and the secondary curative includes a compound
having an ether linkage. In a particular embodiment, the
polyurethane precursor is an isocyanate, the primary curative is an
aromatic diamine, and the secondary curative is a curative such as,
but not limited to, polytetramethylene glycol, amino-functionalized
glycol, or amino-functionalized polyoxypropylene. In an embodiment,
the pre-polymer, a primary curative, and a secondary curative have
an approximate molar ratio of 100 parts pre-polymer, 85 parts
primary curative, and 15 parts secondary curative. It is to be
understood that variations of the ratio may be used to provide a
molded polishing surface layer with varying hardness values, or
based on the specific nature of the pre-polymer and the first and
second curatives. In an embodiment, mixing the pre-polymer and any
curatives to form the mixture 506 includes degassing the mixture
506.
[0068] Referring to FIG. 5E, a lid 510 of the formation mold 500 is
placed into the mixture 506. A top-down plan view of lid 510 is
shown on top, while a cross-section along the a-a' axis is shown
below in FIG. 5E. The lid 510 has disposed thereon a pattern of
protrusions, such as a pattern of protrusions corresponding to the
pattern of grooves or protrusions described in association with
FIG. 3, as depicted in FIG. 5E.
[0069] It is to be understood that embodiments described herein
involving lowering the lid 510 of a formation mold 500 need only
achieve a bringing together of the lid 510 and a base of the
formation mold 500. That is, in some embodiments, a base of a
formation mold 500 is raised toward a lid 510 of a formation mold,
while in other embodiments a lid 510 of a formation mold 500 is
lowered toward a base of the formation mold 500 at the same time as
the base is raised toward the lid 510.
[0070] With the lid 510 placed in the mixture 506, the mixture 506
is at least partially cured to form a polishing surface layer 508
disposed on the foundation layer 502. The pattern of protrusions of
the lid 510 is used to stamp a pattern of grooves from the mixture
506 in the formation mold 500. The mixture 506 may be heated under
pressure (e.g., with the lid 510 in place) to provide the molded
polishing surface layer 508. In an embodiment, heating in the
formation mold 500 includes at least partially curing in the
presence of lid 510, which encloses the mixture 506 in formation
mold 500, at a temperature approximately in the range of 200-260
degrees Fahrenheit and a pressure approximately in the range of
2-12 pounds per square inch.
[0071] In an embodiment, at least partially curing the mixture 506
includes heating the base of the formation mold 500. In an
embodiment, at least partially curing the mixture 506 includes
heating both the mixture 506 and the foundation layer 502. This
approach may alleviate compression stress that may otherwise result
upon cooling of a molded polishing surface layer if the foundation
layer 502 is not heated. In an embodiment, at least partially
curing the mixture 506 forms the molded homogeneous polishing
surface layer 508 covalently bonded with the foundation layer
502.
[0072] Referring to FIG. 5F, a polishing pad 550 is provided upon
removal of the coupled foundation layer 502 and molded polishing
surface layer 508 from the formation mold 500. The polishing
surface layer 508 has a pattern of grooves corresponding to the
pattern of protrusions of the lid 510. A top-down plan view of the
polishing pad 550 is shown below, while a cross-section taken along
the b-b' axis is shown above in FIG. 5F. In an embodiment, as shown
in FIG. 5F, the polishing surface layer 508 is formed from discrete
protrusions (to form the groove pattern), similar or the same as
the polishing surface layer 208 described in association with FIG.
2. However, in another embodiment, the polishing surface layer 508
is a continuous layer with protrusions formed there from, similar
or the same as the polishing surface layer 108 described in
association with FIG. 1. In either case, the polishing surface
layer 508 may be composed of a material or have properties similar
or the same as the materials and properties described above for
polishing surface layers 108 and 208.
[0073] By including a foundation layer in the molding process,
efficiency may be built into the molding process with respect to
timing of demolding a fabricated pad from the formation mold. For
example, in an embodiment, removal of the coupled foundation layer
502 and molded polishing surface layer 508 from the formation mold
500 (e.g., removal of polishing pad 550) is performed when the
extent of curing is sufficient to maintain geometry of the molded
homogeneous polishing surface layer 508 but insufficient for the
molded homogeneous polishing surface layer 508 to withstand
mechanical stress. That is, the removal is performed prior to
removal of a solo molded homogeneous polishing surface layer could
otherwise be performed in the absence of a foundation layer. In one
such embodiment, the foundation layer 502 having the molded
homogeneous polishing surface layer 508 attached thereto is removed
from the base of the formation mold 500 less than approximately 4
minutes after coupling the pattern of grooves of the formation mold
of lid 510 with the mixture 506. Such timing may reflect an
approximately 3-fold reduction in time for the molding process,
enabling greater throughput in a given individual mold. In an
embodiment, removal of the coupled foundation layer 502 and molded
polishing surface layer 508 from the formation mold 500 is
performed immediately after the material of the molded homogeneous
polishing surface layer 508 gels.
[0074] In addition to adding backing support, the foundation layer
may additionally be sized larger than the polishing surface layer
508 to further enable an earlier demolding time. For example, in
one embodiment, the foundation layer 502 extends beyond the molded
homogeneous polishing surface layer 508, and removing the
foundation layer 502 having the molded homogeneous polishing
surface layer 508 formed thereon from the base of the formation
mold 500 includes taking hold of the foundation layer 502 but not
the molded homogeneous polishing surface layer 508.
[0075] It is noted that further curing of the polishing surface
layer 508 through heating may be desirable and may be performed by
placing the polishing pad 550 in an oven and heating. Thus, in one
embodiment, curing the mixture 506 includes first partially curing
in the formation mold 500 and then further curing in an oven.
Either way, a polishing pad 550 is ultimately provided, wherein a
molded polishing surface layer 508 is formed on a foundation layer
502. In an embodiment, the molded polishing surface layer 508 is
composed of a thermoset polyurethane material with a plurality of
closed cell pores disposed in the thermoset polyurethane
material.
[0076] By including a foundation layer in the molding process,
further processing of a fabricated pad there from may be reduced or
eliminated. For example, conventional molding may require
subsequent back-side cutting of the body of a polishing pad.
However, in an embodiment, a polishing pad (e.g., polishing pad
550) including the foundation layer 502 having the molded
homogeneous polishing surface layer 508 formed thereon is suitable
for performing a polishing process without performing a backside
cut of the foundation layer 502, or of the polishing pad 550 in
general.
[0077] By including a foundation layer in the molding process,
recycling or reuse of materials may be made possible. For example,
in an embodiment, the molded homogeneous polishing surface layer
508 is removed from the foundation layer 502, and a second
homogeneous polishing surface layer is formed on the foundation
layer. Such a reuse process of the foundation layer 502 may be
performed after the life of the polishing surface layer and, thus,
the life of the polishing pad is determined to have terminated in a
CMP facility. In another such embodiment, providing the foundation
layer 502 in the formation mold 500 includes first removing a
previously formed polishing surface layer from the foundation layer
502.
[0078] In an embodiment, referring again to FIG. 5C, the mixing
further includes adding a plurality of porogens 520 to the
pre-polymer 504 and the curative 505 to provide closed cell pores
in the ultimately formed polishing surface layer 508 of the
polishing pad 550. Thus, in one embodiment, each closed cell pore
has a physical shell. In another embodiment, referring again to
FIG. 5C, the mixing further includes injecting a gas 522 into to
the pre-polymer 504 and the curative 505, or into a product formed
there from, to provide closed cell pores in the ultimately formed
polishing surface layer 508 of the polishing pad 550. Thus, in one
embodiment, each closed cell pore has no physical shell. In a
combination embodiment, the mixing further includes adding a
plurality of porogens 520 to the pre-polymer 504 and the curative
505 to provide a first portion of closed cell pores each having a
physical shell, and further injecting a gas 522 into the
pre-polymer 504 and the curative 505, or into a product formed
there from, to provide a second portion of closed cell pores each
having no physical shell. In yet another embodiment, the
pre-polymer 504 is an isocyanate and the mixing further includes
adding water (H.sub.2O) to the pre-polymer 504 and the curative 505
to provide closed cell pores each having no physical shell.
[0079] Thus, protrusion patterns contemplated in embodiments of the
present invention may be formed in-situ. For example, as described
above, a compression-molding process may be used to form polishing
pads with a foundation layer having a molded polishing layer with
protrusions disposed thereon. By using a molding process, highly
uniform protrusion dimensions within-pad may be achieved.
Furthermore, extremely reproducible protrusion dimensions along
with very smooth, clean protrusion surfaces may be produced. Other
advantages may include reduced defects and micro-scratches and a
greater usable protrusion depth.
[0080] Also, since the fabricated protrusions of the polishing
surface layer are formed during the molding, the positioning of the
resulting pad during formation of a pad in a mold can be determined
after removal of the pad from the mold. That is, such an polishing
surface layer may be designed (e.g., with clocking marks) to
provide traceability back to the molding process. Thus, in one
embodiment, the polishing surface layer of a polishing pad is a
molded polishing surface layer, and an feature included therein
indicates a location of a region in a mold used for forming a
resulting polishing pad.
[0081] In another aspect, a polishing pad is provided with a
topographically patterned foundation layer bonded with a
corresponding polishing surface layer. For example, FIG. 6
illustrates a cross-sectional view of a polishing pad with a
grooved foundation layer and a polishing surface layer, in
accordance with an embodiment of the present invention.
[0082] Referring to FIG. 6, a polishing pad 600 is provided for
polishing a substrate. The polishing pad 600 includes a grooved
foundation layer 602 having a polishing side 604 and a back side
606. The polishing side 604 of the grooved foundation layer 602 has
a pattern of grooves 614 (and corresponding protrusions) disposed
therein. A continuous polishing surface layer 608 is attached to
the grooved foundation layer 602, conformal with the pattern of
grooves 614. In a preferred, but not limiting, embodiment, the
hardness of the polishing surface layer 608 is less than the
hardness of the grooved foundation layer 602. In an embodiment, the
grooved foundation layer 602 is formed by molding a pattern of
grooves into the foundation layer during fabrication thereof, or
etching a pattern of grooves into a topographically smooth staring
layer.
[0083] In another example, FIG. 7 illustrates a cross-sectional
view of another polishing pad with a grooved foundation layer and a
polishing surface layer, in accordance with an embodiment of the
present invention.
[0084] Referring to FIG. 7, a polishing pad 700 is provided for
polishing a substrate. The polishing pad 700 includes a grooved
foundation layer 702 having a polishing side 704 and a back side
706. The polishing side 704 of the grooved foundation layer 702 has
a pattern of protrusions 714 (and corresponding grooves) disposed
thereon. Each protrusion 714 has a top surface 714A and sidewalls
714B. A non-continuous polishing surface layer 708 is attached to
the grooved foundation layer 702. The non-continuous polishing
surface layer 708 is composed of discrete portions, each discrete
portion attached to the top surface 714A of a corresponding one of
the protrusions 714 of the grooved foundation layer 702. In a
preferred, but not limiting, embodiment, the hardness of the
non-continuous polishing surface layer 708 is less than the
hardness of the grooved foundation layer 702.
[0085] It is to be understood that, while remaining discrete, the
material of the non-continuous polishing surface layer 708 may not
be entirely limited to the top surfaces 714A of the protrusions
714. Depending on the approach used to apply the non-continuous
polishing surface layer 708, other regions of each of the
protrusions 714 may be inadvertently or intentionally covered with
the non-continuous polishing surface layer 708. For example, in an
embodiment (not shown), each discrete portion of the non-continuous
polishing surface layer 708 is further attached to a portion of the
sidewalls 714B of the corresponding protrusions 714 of the
foundation layer 702.
[0086] It is to be understood that the polishing surface layer 608
or 708 may be composed of a material or have properties similar or
the same as the materials and properties described above for
polishing surface layers 108 and 208. Likewise, the foundation
layer 602 or 702 may be composed of a material or have properties
similar or the same as the materials and properties described above
for foundation layers 102 and 202. Such materials and/or properties
may include, but are not limited to, bonding type between the
foundation layer 602 or 702 and the corresponding polishing surface
layer 608 or 708, energy loss factor (KEL), compressibility,
hardness, composition, the inclusion of a detection region, the
inclusion of an aperture, or the inclusion of a sub pad.
[0087] Dimensions for the polishing pads 600 or 700 may be selected
based on polishing performance characteristics. In an embodiment,
the continuous polishing surface layer 608 has a thickness
approximately in the range of 2-50 mils, and the foundation layer
602 has a thickness of greater than approximately 20 mils. In an
embodiment, the non-continuous polishing surface layer 708 has a
thickness approximately in the range of 2-50 mils, and the
foundation layer 702 has a thickness of greater than approximately
20 mils. In an embodiment, the foundation layer 602 or 702 has a
thickness and hardness relative to the thickness and hardness of
the continuous polishing surface layer 608 or the non-continuous
polishing surface layer 708, respectively, sufficient to dictate
the bulk polishing characteristics of the corresponding polishing
pad 600 or 700. In an embodiment, the foundation layer 602 or 702
is sufficiently thick for the corresponding polishing pad 600 or
700 to provide die-level polishing planarity, but sufficiently thin
for the polishing pad 600 or 700 to provide wafer-level polishing
uniformity. In an embodiment, for very thin polishing surface
layers, the hardness measurement corresponds to the bulk or
foundation layer hardness measurement.
[0088] In an embodiment, more than one continuous surface layer
with an uppermost continuous polishing surface layer (such as
continuous polishing surface layer 608) may be used. In another
embodiment, more than one non-continuous surface layer with an
uppermost non-continuous polishing surface layer (such as
non-continuous polishing surface layer 808) may be used. In another
embodiment, a combination of a plurality of continuous and
non-continuous surface layers may be used. Such combinations may be
combinations of homogeneous or non-homogeneous materials.
[0089] Referring as an example to the polishing pads 600 and 700,
in an embodiment, a method of fabricating a polishing pad for
polishing a substrate includes providing a foundation layer with a
surface having a pattern of protrusions formed thereon. Each
protrusion has a top surface and sidewalls. A polishing surface
layer is then formed above the foundation layer. In one such
embodiment, forming the polishing surface layer includes forming a
continuous polishing surface layer attached to the foundation
layer, conformal with the pattern of protrusions, such as depicted
in FIG. 6. In another such embodiment, forming the polishing
surface layer includes forming a non-continuous polishing surface
layer attached to the foundation layer and having discrete
portions. Each discrete portion is attached to the top surface of a
corresponding one of the protrusions of the foundation layer, such
as depicted in FIG. 7. In an embodiment, forming the polishing
surface layer (continuous or non-continuous) includes forming the
polishing surface layer directly on the foundation layer.
[0090] In an embodiment, forming the polishing surface layer
includes using a technique such as, but not limited to, rolling on
the polishing surface layer, spraying on the polishing surface
layer, double molding the polishing surface layer with the
foundation layer, printing the polishing surface layer, or stamping
on the polishing surface layer. Polishing pads made in such a
manner may be amenable to reuse. For example, in one embodiment, at
end of life of the polishing pad, the polishing surface layer is
removed from the foundation layer. A second polishing surface layer
is then formed above the foundation layer. In an embodiment,
providing the foundation layer includes first removing a previously
formed polishing surface layer from the foundation layer.
[0091] In an embodiment, polishing pads described herein, such as
polishing pads 100, 200, 300, 400, 600 or 700, are suitable for
polishing substrates. The substrate may be one used in the
semiconductor manufacturing industry, such as a silicon substrate
having device or other layers disposed thereon. However, the
substrate may be one such as, but not limited to, a substrates for
MEMS devices, reticles, or solar modules. Thus, reference to "a
polishing pad for polishing a substrate," as used herein, is
intended to encompass these and related possibilities. In an
embodiment, a polishing pad has a diameter approximately in the
range of 20 inches to 30.3 inches, e.g., approximately in the range
of 50-77 centimeters, and possibly approximately in the range of 10
inches to 42 inches, e.g., approximately in the range of 25-107
centimeters.
[0092] Polishing pads described herein may be suitable for use with
a variety of chemical mechanical polishing apparatuses. As an
example, FIG. 8 illustrates an isometric side-on view of a
polishing apparatus compatible with a polishing pad with a
foundation layer and a polishing surface layer, in accordance with
an embodiment of the present invention.
[0093] Referring to FIG. 8, a polishing apparatus 800 includes a
platen 804. The top surface 802 of platen 804 may be used to
support a polishing pad with a foundation layer and a polishing
surface layer. Platen 804 may be configured to provide spindle
rotation 806 and slider oscillation 808. A sample carrier 810 is
used to hold, e.g., a semiconductor wafer 811 in place during
polishing of the semiconductor wafer with a polishing pad. Sample
carrier 810 is further supported by a suspension mechanism 812. A
slurry feed 814 is included for providing slurry to a surface of a
polishing pad prior to and during polishing of the semiconductor
wafer. A conditioning unit 890 may also be included and, in one
embodiment, includes a diamond tip for conditioning a polishing
pad.
[0094] Thus, polishing pads with foundation layers and polishing
surface layers have been disclosed. In accordance with an
embodiment of the present invention, a polishing pad for polishing
a substrate includes a foundation layer having a first hardness. A
polishing surface layer is bonded directly to the foundation layer.
The polishing surface layer has a second hardness less than the
first hardness. In one embodiment, the polishing surface layer
includes a continuous layer portion with a plurality of polishing
features protruding there from, the continuous layer portion bonded
directly to the foundation layer. In one embodiment, the polishing
surface layer includes a plurality of discrete polishing
protrusions bonded directly to the foundation layer.
* * * * *