U.S. patent application number 17/297221 was filed with the patent office on 2022-01-27 for polishing pads and systems and methods of making and using the same.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Samad Javid, Duy K. Lehuu, Qin Lin, David J. Muradian.
Application Number | 20220023991 17/297221 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-27 |
United States Patent
Application |
20220023991 |
Kind Code |
A1 |
Lehuu; Duy K. ; et
al. |
January 27, 2022 |
POLISHING PADS AND SYSTEMS AND METHODS OF MAKING AND USING THE
SAME
Abstract
A polishing pad includes a polishing layer having a first major
surface and a second major surface opposite the first major
surface. The polishing pad further includes a subpad, which is
coupled to the polishing layer, and has a first major surface and a
second major surface opposite the first major surface. At least 50%
of the subpad, based on the total surface area of the first major
surface of the subpad, is optically transparent.
Inventors: |
Lehuu; Duy K.; (Lake Elmo,
MN) ; Lin; Qin; (Woodbury, MN) ; Muradian;
David J.; (Saint Paul, MN) ; Javid; Samad;
(Woodbury, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Appl. No.: |
17/297221 |
Filed: |
November 22, 2019 |
PCT Filed: |
November 22, 2019 |
PCT NO: |
PCT/IB2019/060064 |
371 Date: |
May 26, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62771738 |
Nov 27, 2018 |
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International
Class: |
B24B 37/22 20060101
B24B037/22; B24B 37/24 20060101 B24B037/24; B24B 37/04 20060101
B24B037/04 |
Claims
1) A polishing pad comprising: a polishing layer having a first
major surface and a second major surface opposite the first major
surface; a subpad having a first major surface and a second major
surface opposite the first major surface, wherein the subpad is
coupled to the polishing layer; and wherein at least 50% of the
subpad, based on the total surface area of the first major surface
of the subpad, is optically transparent.
2) The polishing pad of claim 1, wherein at least 50% of the
polishing layer, based on the total surface area of the first major
surface of the polishing pad, is optically transparent.
3) The polishing pad of claim 2, wherein at least 50% of the
optically transparent region of the subpad overlays the optically
transparent region of the polishing pad.
4) The polishing pad of claim 3, wherein the polishing pad is
optically transparent in the region of the subpad that overlays the
optically transparent region of the polishing pad.
5) The polishing pad of claim 4, wherein the subpad has a Young's
Modulus of between 4000 kPa and 100 kPa, between 3000 kPa and 200
kPa, or between 300 and 2000 kPa.
6) The polishing pad of claim 4, wherein the subpad has a Shore A
hardness of between 5 and 70.
7) The polishing pad of claim 4, wherein the subpad is elasctically
deformable.
8) The polishing pad of claim 4, wherein the subpad has a
relaxation modulus of less than 40%.
9) The polishing pad of claim 1, wherein the subpad comprises
cavities or voids.
10) The polishing pad of claim 9, wherein a volume percentage of
the voids and cavities is less than about 50.
11) The polishing pad of claim 4, wherein the subpad has a
compressibility at 25% deflection of between 25 and 1000 kPa.
12) The polishing pad of claim 4, wherein the subpad comprises a
polymer having a glass transition below room temperature.
13) The polishing pad of claim 4, wherein the subpad comprises a
polymer and a plasticizer.
14) The polishing pad of claim 4, wherein the subpad comprises an
acrylate or methacrylate resin.
15) The polishing pad of claim 4, wherein the polishing layer
comprises pores and asperities.
16) A method of polishing a substrate, the method comprising:
providing the polishing pad of claim 4; providing a substrate;
contacting the first major surface of the polishing pad with the
substrate; moving the polishing pad and the substrate relative to
one another while maintaining contact between the first major
surface of the polishing pad and the substrate.
Description
FIELD
[0001] The present disclosure relates to polishing pads and systems
useful for the polishing of substrates, and methods of making and
using such polishing pads.
SUMMARY
[0002] In some embodiments, a polishing pad is provided. The
polishing pad includes a polishing layer having a first major
surface and a second major surface opposite the first major
surface. The polishing pad further includes a subpad, which is
coupled to the polishing layer, and has a first major surface and a
second major surface opposite the first major surface. At least 50%
of the subpad, based on the total surface area of the first major
surface of the subpad, is optically transparent.
[0003] The above summary of the present disclosure is not intended
to describe each embodiment of the present disclosure. The details
of one or more embodiments of the disclosure are also set forth in
the description below. Other features, objects, and advantages of
the disclosure will be apparent from the description and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The disclosure may be more completely understood in
consideration of the following detailed description of various
embodiments of the disclosure in connection with the accompanying
figures, in which:
[0005] FIG. 1 is a schematic cross-sectional view of a polishing
pad in accordance with some embodiments of the present
disclosure.
[0006] FIG. 2 is a schematic view of a polishing system in
accordance with some embodiments of the present disclosure.
DETAILED DESCRIPTION
[0007] Chemical-mechanical planarization (CMP) is a process used to
planarize the surface topography of a wafer in the fabrication of
integrated circuits (ICs) and often employs the use a liquid or
slurry and a polishing pad. During the process, the slurry
chemically reacts with materials on the surface of the wafer. The
reacted materials are then removed mechanically by abrasive
particles in the slurry or within the pad. Performance
characteristics relevant to CMP include wafer removal rate (WRR),
wafer non-uniformity (NU), and defectivity.
[0008] With respect to wafer NU, nonuniformity of the pattern
layout within a layer of an IC die often contributes to nonuniform
polishing across the die area (overpolishing/dishing). Variation of
the CMP process parameters (platen and wafer carrier speeds, wafer
pressure, slurry transport, etc.) and process random variation
contribute to increase in within-wafer and within-lot
nonuniformity. To reduce the variance of polishing outputs (e.g.,
uniformity, overpolishing, and dishing), integration of in situ
sensing and endpoint detection techniques with process optimization
schemes to improve process performance are employed. Detecting the
end point using optical reflectance (e.g., using reflected optical
signal at either a single wave length (i.e. a laser source) or a
broadband light, which travels back and forth through the polishing
pad and to the wafer surface, is one of the known techniques.
[0009] The components of commercially available polishing pads
(e.g., the top pad, subpad, optional foam layers, and the like) are
typically non-optically transparent, e.g. opaque, and are disposed
between the optical signal generator of a polishing tool and the
surface of the wafer to be polished. Thus, these components prevent
optical sensing directly through the pad. Consequently, to enable
optical end point detection, often times an end-point detection
window is fabricated within the polishing pad. This may be achieved
by cutting an appropriate size aperture in the polishing pad
(including the top pad and any non-optically transparent layers to
be coupled to the top pad, such as the subpad and optional foam
layers that overlay the polishing pad). The window is then created
by inserting a solid, optically transparent (e.g., polyurethane)
window into the aperture and securing the window to the pad. During
the CMP process, optical signals may then be passed, via the
window, though the polishing pad (including any of the coupled
layers) to enable end point detection. While this practice provides
adequate end point detection, accommodation of end point detection
through an aperture in the polishing pad is associated with
increased manufacturing complexity of the polishing pad and
polishing performance issues. For example, formation of the
aperture through the polishing pad results in an additional
manufacturing step for each layer of the polishing pad.
Additionally, the presence of apertures in the polishing pad
results in non-uniform pressure and contact material to the wafer
surface and, in turn, performance reliability. Still further, end
point detection through an aperture in the polishing pad limits the
location of the aperture in the pad through which end point
detection can occur, as the window of the pad must align with the
detection system of the tool, e.g. the end point detection window
of the platen the pad is mounted to. Consequently, polishing pads
that do not require apertures in the various layers (or minimize
the number of apertures) for end point detection are desirable, as
they provide uniform pressure and contact material to the wafer
surface, and/or allow for flexibility in the precise location of
end point detection through the polishing pad.
Definitions
[0010] As used herein, the singular forms "a", "an", and "the"
include plural referents unless the content clearly dictates
otherwise. As used in this specification and the appended
embodiments, the term "or" is generally employed in its sense
including "and/or" unless the content clearly dictates
otherwise.
[0011] As used herein, the recitation of numerical ranges by
endpoints includes all numbers subsumed within that range (e.g. 1
to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).
[0012] Unless otherwise indicated, all numbers expressing
quantities or ingredients, measurement of properties and so forth
used in the specification and embodiments are to be understood as
being modified in all instances by the term "about." Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the foregoing specification and attached listing of
embodiments can vary depending upon the desired properties sought
to be obtained by those skilled in the art utilizing the teachings
of the present disclosure. At the very least, and not as an attempt
to limit the application of the doctrine of equivalents to the
scope of the claimed embodiments, each numerical parameter should
at least be construed in light of the number of reported
significant digits and by applying ordinary rounding
techniques.
[0013] "Working surface" refers to a major surface of a polishing
pad that is intended to be nearest to, and at least partially
contact a major surface of a substrate being polished.
[0014] "Pore" refers to a cavity in the working surface of a pad
that allows a fluid, e.g. a liquid, to be contained therein. The
pore enables at least some fluid to be contained within the pore
and not flow out of the pore.
[0015] "Precisely shaped" refers to a topographical feature, e.g.
an asperity or pore, having a molded shape that is the inverse
shape of a corresponding mold cavity or mold protrusion, said shape
being retained after the topographical feature is removed from the
mold. A pore formed through a foaming process or removal of a
soluble material (e.g. a water soluble particle) from a polymer
matrix, is not a precisely shaped pore.
[0016] As used herein, "major surface" refers to the surfaces of an
article or layer having a greater dimension or surface area than
other surfaces of the article or layer, for example, an article or
layer that has an aspect ratio of greater width or diameter to
height, where the surface area of the side corresponding to the
article or layer height (e.g., thickness) is significantly smaller
than the surface area of the width or diameter of the same article
or layer.
[0017] As used herein, in some embodiments, "optically transparent"
refers to an article or layer that has optical transmission value
of at least 10% at wavelengths of at least 400 nm, when tested as
described in the Light Transmission Test Method of the Examples. In
other embodiments, "optically transparent" refers to an article or
layer that has optical transmission value of at least 20%, at least
30%, at least 40%, at least 50%, at least 60%, at least 70%, or at
least 80%, at wavelengths of at least 400 nm, when tested as
described in the Light Transmission Test Method of the Examples.
The term "optical transmission value" means the percentage of light
that is not either reflected back toward the source or absorbed by
the sample as a percentage of the total incident light at a
wavelength of 400 nm (light emitted/light source.times.100). For
purposes of the present application, optically transparent articles
or layers permit transmission therethrough of optical signals
employed in conventional end point detection systems to an extent
necessary to achieve accurate end point detection.
[0018] "Thickness", when discussed in relation to a polishing pad,
refers to the total average thickness of any and all layers of the
polishing pad measured in a direction normal to the working
surface. "Thickness", when discussed in relation to a layer of a
polishing pad refers to the total average thickness of such layer
of the polishing pad measured in a direction normal to the working
surface of the polishing pad.
[0019] The present disclosure is directed to articles, systems, and
methods useful for polishing substrates including, for example,
semiconductor wafers.
[0020] In some embodiments, as shown in FIG. 1, the present
disclosure is directed to a polishing pad 10, which may be used to
polish a substrate in, for example, a CMP process. The polishing
pad 10 may include a polishing layer 15 (often referred to as a top
pad) having a first major surface 15A (which will be referred to as
the "working surface" of the polishing pad 15) and a second major
surface 15B opposite the first major surface 15A. The polishing pad
10 may further include a subpad 30 that is coupled to the polishing
layer 15, the subpad 30 having a first major surface 30A (nearest
the polishing layer 15) and a second major surface 30B opposite the
first major surface 30A (which is intended for coupling to a platen
of a polishing apparatus). The polishing pad 10 may further include
one or more optional layers 40 disposed between the polishing layer
15 and the subpad 30. The layers forming the polishing pad 10 may
be coupled to one another via any suitable coupling mechanism know
in the art. For example, adhesives, e.g. pressure sensitive
adhesives (PSAs), hot melt adhesives, or cure in place adhesives
may be employed. Additionally, or alternatively, lamination may be
employed.
[0021] In some embodiments, the polishing layer 15 may include or
be formed of a polymer. Polishing layer 15 may be fabricated from
any known polymer, including thermoplastics, thermoplastic
elastomers (TPEs), e.g. TPEs based on block copolymers, or
thermosets, e.g. elastomers and combinations thereof. In some
embodiments, the polishing layer may include or be formed of a
polyurethane, polyamide, polybutadiene, or polyolefin, such as is
common in commercially available polishing pads for substrate
planarization.
[0022] In some embodiments, the hardness of polishing layer 15 may
be predominately controlled by the polymer used to fabricate it. In
some embodiments, the hardness of polishing layer 15 may be greater
than about 20 Shore D, greater than about 30 Shore D, or greater
than about 40 Shore D; less than about 90 Shore D, less than about
80 Shore D, or less than about 70 Shore D; between 20 and 90 Shore
D, between 30 and 80 Shore D, or between 40 and 70 Shore D. In some
embodiments, the hardness of polishing layer 15 may be greater than
about 20 Shore A, greater than about 30 Shore A, or greater than
about 40 Shore A; less than about 95 Shore A, less than about 80
Shore A or less than about 70 Shore A; or between 20 and 95 Shore
A, between 30 and 80 Shore A, or between 40 and 70 Shore A.
[0023] In some embodiments, the thickness of the polishing layer 15
may be greater than about 25 microns, greater than about 50
microns, greater than about 100 microns, or greater than 250
microns; less than about 20 mm, less than about 10 mm, less than
about 5 mm, or less than about 2.5 mm; or between 15 microns and 20
mm, between 25 microns and 10 mm, between 50 microns and 5 mm, or
between 100 microns and 2.5 mm.
[0024] In various embodiments, the polishing layer 15 may be
flexible. For example, in some embodiments, the polishing layer 15
may be capable of being bent back upon itself producing a radius of
curvature in the bend region of less than about 10 cm, less than
about 5 cm, less than about 3 cm, or less than about 1 cm; and
greater than about 0.1 mm, greater than about 0.5 mm, or greater
than about 1 mm. In some embodiments, the polishing layer 15 may be
capable of being bent back upon itself producing a radius of
curvature in the bend region of between about 10 cm and about 0.1
mm, between about 5 cm and about 0.5 mm, or between about 3 cm and
about 1 mm.
[0025] In some embodiments, the polishing layer 15 may be a unitary
sheet. For purposes of the present application, a unitary sheet
refers to an article that includes only a single layer of material
(i.e. it is not a multi-layer construction, or laminate) and the
single layer of material has a single composition. The composition
may include multiple-components, e.g. a polymer blend or a
polymer-inorganic composite. Use of a unitary sheet as the
polishing layer may provide cost benefits, due to minimization of
the number of process steps required to form the polishing layer. A
polishing layer that includes a unitary sheet may be fabricated
from techniques know in the art, including, but not limited to,
molding and embossing.
[0026] In some embodiments, the polishing layer 15 may be optically
transparent (at least to an extent sufficient to allow for end
point detection through such portion of the polishing layer 15)
over at least 10%, at least 50%, at least 60%, at least 70%, at
least 80%, at least 90%, or at least 99% of its surface area, based
on the total surface area of the working surface 15a. In such
embodiments, the polishing layer 15 may not include an aperture for
receiving an end point detection window. In alternative
embodiments, the polishing layer 15 may not be optically
transparent. In such embodiments, the polishing layer 15 may
include an aperture for receiving an end point detection
window.
[0027] In some embodiments, the polishing layer 15 may include a
plurality of precisely shaped pores and a plurality of precisely
shaped asperities on its working surface 15a, such as in the
polishing pads described in U.S. patent application Ser. No.
15/300,125, which is herein incorporated by reference in its
entirety.
[0028] In some embodiments, the subpad 30, or a substantial portion
of the subpad 30, may include or be formed of an optically
transparent material. For example, in some embodiments, the subpad
30 may include or be formed of soft polymeric materials with glass
transition below 30.degree. C. or polymers blended with
plasticizers. Other additives such as photo initiators, free
radical initiators, crosslinkers, or inorganic fillers, may be
added without interrupting the optical transparency.
[0029] Suitable soft polymeric materials may include elastomers,
polyurethanes, polyolefins, polycarbonates, polyamides, elastomeric
rubbers, styrenic polymers, polystyrenes, polymethylmethacrylates,
copolymers and block copolymers thereof, and mixtures and blends
thereof. In some embodiments, the subpad 30 may include or consist
essentially of oligomeric acrylate or methacrylate resins.
[0030] Suitable oligomeric acrylate monomers may include epoxy
oligomeric acrylate/methacrylate, urethane oligomeric
acrylate/methacrylate, polyester oligomeric acrylate/methacrylate,
polyether oligomeric acrylate/methacrylate and amino
acrylate/methacrylate monomers.
[0031] In some embodiments, suitable monomers have a single
ethylenically unsaturated group. The monomers may include or
consist essentially of alkyl (meth)acrylate. The alkyl group can be
linear, branched, cyclic, bicyclic, tricylic, adamantly or a
combination thereof. Suitable alkyl (meth)acrylates include methyl
(meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate,
isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl
(meth)acrylate, n-pentyl (meth)acrylate, 2-methylbutyl
(meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate,
3,3,5-trimethylcyclohexyl (meth)acrylate, 4-methyl-2-pentyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-methylhexyl
(meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate,
2-octyl (meth)acrylate, isononyl (meth)acrylate, isoamyl
(meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate,
2-propylheptyl (meth)acrylate, isotridecyl (meth)acrylate,
isobornyl (meth)acrylate, isostearyl (meth)acrylate, octadecyl
(meth)acrylate, 2-octyldecyl (meth)acrylate, dodecyl
(meth)acrylate, lauryl (meth)acrylate, dicyclopentenloxyethy
(meth)acrylate, dicyclopentanyl acrylate, 1-adamantly
(meth)acrylate, 2-adamantly (meth)acrylate and heptadecanyl
(meth)acrylate. Some suitable branched alkyl (meth)acrylates
include (meth)acrylic acid esters of Guerbet alcohols having 12 to
32 carbon atoms as described in U.S. Pat. No. 8,137,807 (Clapper et
al.). The alkyl monomers can be a single isomer or an isomer blend
such as those described in U.S. Pat. No. 9,102,774 (Clapper et
al.). Other monomers with a single ethylenically unsaturated group
that can be used are heteroalkyl (meth)acrylates. The heteroalkyl
group can be linear, branched, cyclic, bicyclic, or a combination
thereof. The heteroatom is often oxygen (--O--) but can be sulfur
(--S--) or nitrogen (--NH--). The heteroalkyl often has 2 to 12
carbon atoms and 1 to 4 heteroatom or 4 to 10 carbon atoms and 1 to
3 heteroatoms. Suitable heteroalkyl (meth)acrylates include
alkoxylated alkyl (meth)acrylates such as 2-(2-ethoxyethoxy)ethyl
(meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxyethyl
(meth)acrylates. Still other monomers with a single ethylenically
unsaturated group can include a urethane linkage (--NH--(CO)--O--).
One example is 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, which
is commercially available under the trade designation GENOMER G1122
from Rahn USA Corp. (Aurora, Ill., USA).
[0032] In some embodiments, suitable plasticizers can be small
molecular, oligomeric or polymeric compounds, which are compatible
with the resin/soft polymer system, and thus significantly lowering
the glass transition temperature for the plastic and making it
softer. For example, plasticizers may include sebacates, adipates
terephalate, dibenzoate, gluterate, phthalates, azelates, other
ester compounds or any other organic chemicals, such as
sulfonamides, organophosphates, polyethers and polybutene
compatible with the resin. Additional examples include benzyl butyl
phthalate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl)
adipate, bis(2-ethylhexyl) maleate, bis(2-ethylhexyl) sebacate,
dibasic ester mixture(mixture of dimethyl adipate and dimethyl
glutarate), dibasic ester mixture (mixture of dimethyl glutarate
and dimethyl succinate), dimethyl glutarate, dibutyl adipate,
dibutyl itaconate, dibutyl sebacate, dicyclohexyl phthalate,
diethyl adipate, diethyl azelate, di(ethylene glycol) dibenzoate,
diethyl sebacate, diethyl succinate, diheptyl phthalate, diisobutyl
adipate, diisobutyl fumarate, diisobutyl phthalate, diisodecyl
adipate, diisononyl phthalate, dimethyl adipate, dimethyl azelate,
dimethyl phthalate, di(propylene glycol) dibenzoate, dipropyl
phthalate, ethyl 4-acetylbutyrate, 2-(2-ethylhexyloxy)ethanol,
isooctyl tallate, neopentyl glycol dimethylsulfate, poly(ethylene
glycol) bis(2-ethylhexanoate), poly(ethylene glycol) dibenzoate,
poly(ethylene glycol) dioleate, poly(ethylene glycol) monolaurate,
poly(ethylene glycol) monooleate, sucrose benzoate, trioctyl
trimellitate, trimethyl trimellitate, tri-(2-ethylhexyl)
trimellitate, tri-(heptyl,nonyl) trimellitate, N-ethyl toluene
sulfonamide, N-(2-hydroxypropyl) benzene sulfonamide, N-(n-butyl)
benzene sulfonamide. Plasticizers can also be bio-based materials,
acetylated monoglycerides, triethyl citrate, tributyl citrate,
acetyltributyl citrate, trioctyl citrate, acetyl trioctyl citrate,
trihexyl citrate, acetyl trihexyl citrate, butyryl trihexyl
citrate, trimethyl citrate, methyl ricinoleate, epoxidized soybean
oil, or epoxidized vegetable oil.
[0033] In some embodiments, the acrylate/methacrylate can be
polymerized and crosslinked by photoinitiators/or thermal
initiators. In some embodiments, inorganic filler such fume silica,
calcium carbonate, kaolin, alumina trihydrate, calcium sulfate or
titanium oxide can be added to modify the mechanical
performances.
[0034] In some embodiments, at least 50%, at least 60%, at least
70%, at least 80%, at least 90%, at least 99%, or 100% of the
subpad 30, based on the total surface area of the first major
surface 30A of the subpad 30, may be optically transparent. In
embodiments in which the polishing layer 15 (or at least a portion
of the polishing layer 15) is optically transparent, at least 10%,
at least 50%, at least 60%, at least 70%, at least 80%, at least
90%, at least 99%, or 100% of the of the optically transparent
region of the subpad 30 may overlay an optically transparent region
of the polishing layer 15. In such embodiments, the polishing pad
10 (including the polishing layer 15, subpad 30, and any
intervening layers) may be optically transparent (in a direction
normal to the working surface) at least in the overlay region of
subpad 30 and the polishing layer 15. For purposes of the present
application, it is to be appreciated that overlaid layers of the
polishing pad 10 may refer to directly overlaid layers (i.e.,
layers that are in physical contact) or indirectly overlaid layers
(i.e, layers that are not in physical contact due to, for example,
one or more intervening layers) but that overlap with one another
when one layer is superimposed on the other layer. Overlaying
optically transparent regions of the polishing layer 15 and subpad
30 in this fashion facilitates increased flexibility in selecting
the position through which end point detection can occur within the
polishing pad 10. Moreover, it eliminates the need for the
inclusion of a pad window (and the associated apertures in the
polishing layer and subpad) which, in turn, facilitates uniform
pressure and contact material from the polishing pad to the
substrate to be polished.
[0035] In some embodiments, the thickness of the subpad 30 may be
greater than about 25 microns, greater than about 50 microns,
greater than about 100 microns, or greater than 250 microns; less
than about 20 mm, less than about 10 mm, less than about 5 mm, or
less than about 2.5 mm; or between 25 microns and 20 mm, between 50
microns and 10 mm, or between 100 microns and 5 mm.
[0036] In some embodiments, the subpad 30 may be intended to
provide the polishing pad 10 with sufficient compliance to mitigate
pressure variation at the surface of the substrate to be polished
by the polishing pad 10. The pressure nonuniformity might be caused
by variation in the engagement of slurry abrasive particles into
the substrate surface due to, for example, variation in the size of
the abrasive particles, thickness variation in any layer of the
polishing pad 10, existence of debris in the contact area between
the substrate surface and the major surface 15A of the polishing
pad 10, or topology variation in the substrate surface. The
pressure variation at the surface of the substrate exposing to the
polishing pad causes undesired polishing variation on the substrate
surface and thus need to be moderated. In this regard, in some
embodiments, the subpad 30 may have a Young's Modulus of less than
about 4000 kPa, less than about 3000 kPa, or less than about 2000
kPa; greater than about 100 kPa, greater than about 200 kPa, or
greater than about 300 kPa; or between 4000 kPa and 100 kPa,
between 3000 kPa and 200 kPa, or between 2000 and 300 kPa. In some
embodiments, the subpad 30 may be composed of a material selected
according to hardness. In this regard, in some embodiments, subpad
30 may have a Shore A hardness (measured in accordance with ASTM
D2240) of less than about 70, less than about 60, or less than
about 50; greater than about 5, greater than about 10, or greater
than about 15; or between 70 and 5, between 60 and 10, or between
50 and 15. In some embodiments, the subpad 30 may be composed of a
material selected according to elastic deformation. Elastic
deformation may represent an ability of a material to recover to
its original state after being deformed. The material of subpad 30
may be elastically deformable, e.g., being capable of substantially
100% (e.g., 99% or more, 99.5% or more, or 99.9% or more)
recovering to its original state after being deformed. In some
embodiments, the subpad 30 may be composed of a material selected
according to relaxation modulus. Relaxation modulus may represent a
measure of a time-dependent viscoelastic property. In this
disclosure, relaxation modulus is measured according to the
Relaxation Test described herein. In this regard, in some
embodiments, subpad 30 may have a relaxation modulus of less than
40%, less than 35%, or less than 30% measured according to the
Relaxation Test.
[0037] In some embodiments, subpad 30 or at least a portion of that
may contain cavities or voids, or may be expanded, engraved, or
perforated to provide more compliance to the polishing pad 10. The
voids and cavities may be distributed sporadic or patterned
regularly at least in a portion of subpad 30. The volume percentage
of voids and cavities may be less than about 50, less than about
30, or less than about 20 vol. %, based on the total volume of the
subpad 30. The voids can be defects during fabrication or can be
fabricated by, but not limited to, casting on mold or machined by
different methods, such as mechanical drilling, or laser blasting.
The voids can have a variety of shapes such as rectangular column,
pyramid, cone, sphere, hemisphere, or others. The voids can pass
through the whole subpad layer 30, or terminate mid-layer, or a
combination thereof. The average size (in terms of longest
dimension) of the voids may be less than 5 mm, less than 3 mm, or
less than 2 mm. The voids can be arranged in different patterns or
densities. In any case, the cavities or voids do not meaningfully
interrupt the optical transparency of subpad 30.
[0038] In some embodiments, the subpad 30 may have a
compressibility at 25% deflection, measured according to ASTM
D1056, of less than 1000 kPa, less than 750 kPa, or less than 500
kPa; greater than about 25 kPa, greater than about 50 kPa, or
greater than about 75 kPa; or between 1000 kPa and 25 kPa, between
750 kPa and 50 kPa, or between 500 and 75 kPa. In some embodiments,
the subpad 30 may have a Poisson's ratio of less than 0.5, less
than 0.4, less than 0.3, less than about 0.2, or a negative
Poisson's ratio.
[0039] In some embodiments, the subpad may include multiple layers,
e.g. may include two or more layers of material. In some
embodiments, the subpad may include a rigid layer, e.g. a high
modulus material such as a thermoplastic, and a compliant layer,
e.g. a low modulus material as previously described above. A
polishing pad that includes a multiple layer subpad, having at
least one rigid layer and at least one compliant layer, may enable
the planarization characteristic of the polishing pad to be
adjusted and thus provide the ability to optimize the polishing
pads polishing performance to the wafer topography being
polished.
[0040] In some embodiments, the polishing pad 10 may include one or
more layers that are disposed between the polishing layer 15 and
the subpad 30. For example, as shown in FIG. 1, the polishing pad
may include a foam layer 40 that is interposed between the
polishing layer 15 and the subpad 30.
[0041] In some embodiments, the foam layer 40 may be open-cell or
closed-cell including or be formed of list suitable materials for
foam layer, for example, synthetic or natural foams, thermoformed
foams, polyurethanes, polyesters, polyethers, filled or grafted
polyethers, viscoelastic foams, melamine foam, polyethylenes,
cross-linked polyethylenes, polypropylenes, silicone, or ionomeric
foams.
[0042] In some embodiments, the thickness of the foam layer 40 may
be greater than 25 microns, greater than 50 microns, greater than
100 microns, or greater than 250 microns; less than 20 mm, less
than 10 mm, less than 5 mm, or less than 2.5 mm.
[0043] In some embodiments, the foam layer 40 may be optically
transparent (at least to an extent sufficient to allow for end
point detection through such portion of the foam layer 40) over at
least 50%, at least 60%, at least 70%, at least 80%, at least 90%,
or at least 99% of its surface area, based on the total surface
area one of its major surfaces. In such embodiments, the foam layer
40 may not include an aperture for receiving an end point detection
window. In alternative embodiments, the foam layer 40 may not be
optically transparent. In such embodiments, the foam layer 40 may
include an aperture for receiving an end point detection
window.
[0044] In some embodiments, the foam layer 40 may have a durometer
from between about 20 Shore D to about 90 Shore D and/or between
about 20 Shore A to about 90 Shore A.
[0045] In some embodiments, in addition to, or as an alternative to
the foam layer 40, layers disposed between the polishing layer 15
and the subpad 30 may include one or more stiff polymer layers such
as polycarbonate, polymethyl methacrylate, polyethylene,
polyethylene terephthalate, polyethylene terephthalate-glycol
modified, polypropylene, polyvinylchloride,
acrylonitrile-butadiene-styrene. Adhesive layers can also be
present including acrylic adhesives, urethane adhesives, or other
epoxy adhesives.
[0046] In some embodiments, the thickness of the polishing pad 10
is not particularly limited. For example, the thickness of the
polishing pad 10 may coincide with the required thickness to enable
polishing on the appropriate polishing tool. In some embodiments,
the thickness of the polishing pad may be greater than 25 microns,
greater than 50 microns, greater than 100 microns, or greater than
250 microns; less than 20 mm, less than 10 mm, less than 5 mm, or
less than 2.5 mm; or between 25 microns and 20 mm, between 50
microns and 10 mm, or between 50 microns and 5 mm. The shape of the
polishing pad 10 (when viewed from a direction normal to the
working surface) is not particularly limited. In some embodiments,
the polishing pads 10 may be fabricated such that the pad shape
coincides with the shape of the corresponding platen of the
polishing tool the pad will be attached to during use. Pad shapes,
such as circular, square, hexagonal and the like may be used. A
maximum dimension of the pad in a direction parallel to the working
surface (i.e. the diameter for a circular shaped pad) is not
particularly limited. In some embodiments, such maximum dimension
of the polishing pad 10 may be greater than 10 cm, greater than 20
cm, greater than 30 cm, greater than 40 cm, greater than 50 cm, or
greater than 60 cm; less than 2.0 meters, less than 1.5 meters, or
less than 1.0 meter.
[0047] In some embodiments, the present disclosure relates to a
polishing system, the polishing system including any one of the
previously discussed polishing pads 10 and a polishing solution.
The polishing solutions used are not particularly limited and may
be any of those known in the art. The polishing solutions may be
aqueous or non-aqueous. An aqueous polishing solution is defined as
a polishing solution having a liquid phase (does not include
particles, if the polishing solution is a slurry) that is at least
50% by weight water. A non-aqueous solution is defined as a
polishing solution having a liquid phase that is less than 50% by
weight water. In some embodiments, the polishing solution is a
slurry, i.e. a liquid that contains organic or inorganic abrasive
particles or combinations thereof. The concentration of organic or
inorganic abrasive particles or combination thereof in the
polishing solution is not particularly limited. The concentration
of organic or inorganic abrasive particles or combinations thereof
in the polishing solution may be, greater than 0.5%, greater than
1%, greater than 2%, greater than 3%, greater than 4% or even
greater than 5% by weight; may be less than 30%, less than 20% less
than 15%, or less than 10% by weight. In some embodiments, the
polishing solution is substantially free of organic or inorganic
abrasive particles. By "substantially free of organic or inorganic
abrasive particles" it is meant that the polishing solution
contains less than 0.5%, less than 0.25%, less than 0.1% or less
than 0.05% by weight of organic or inorganic abrasive particles. In
one embodiment, the polishing solution may contain no organic or
inorganic abrasive particles. The polishing system may include
polishing solutions, e.g. slurries, used for silicon oxide CMP,
including, but not limited to shallow trench isolation CMP;
polishing solutions, e.g. slurries, used for metal CMP, including,
but not limited to, tungsten CMP, copper CMP and aluminum CMP;
polishing solutions, e.g. slurries, used for barrier CMP, including
but not limited to tantalum and tantalum nitride CMP and polishing
solutions, e.g. slurries, used for polishing hard substrates, such
as, sapphire. The polishing system may further include a substrate
to be polished or abraded.
[0048] FIG. 2 is a schematic illustration of a polishing system 100
for utilizing the polishing pads and methods in accordance with
some embodiments of the present disclosure. As shown, the system
100 may include a polishing pad 150 (such as any one of the above
described polishing pads) and a polishing solution 160. The system
may further include a substrate 110 to be polished or abraded, a
platen 140, and a carrier assembly 130. An adhesive layer 170 may
be used to attach the polishing pad 150 to platen 140 and may be
part of the polishing system. Polishing solution 160 may be a layer
of solution disposed about a major surface of the polishing pad
150. The polishing solution is typically disposed on the working
surface of the polishing layer of the polishing pad. The polishing
solution may also be at the interface between substrate 110 and
polishing pad 150. During operation of the polishing system 100, a
drive assembly 145 may rotate (arrow A) the platen 140 to move the
polishing pad 150 to carry out a polishing operation. The polishing
pad 150 and the polishing solution 160 may separately, or in
combination, define a polishing environment that mechanically
and/or chemically removes material from or polishes a major surface
of a substrate 110. To polish the major surface of the substrate
110 with the polishing system 100, the carrier assembly 130 may
urge substrate 110 against a working surface, i.e. a polishing
surface, of the polishing pad 150 in the presence of the polishing
solution 160. The platen 140 (and thus the polishing pad 150)
and/or the carrier assembly 130 then move relative to one another
to translate the substrate 110 across the polishing surface of the
polishing pad 150. The carrier assembly 130 may rotate (arrow B)
and optionally traverse laterally (arrow C). As a result, the
polishing layer of polishing pad 150 removes material from the
surface of the substrate 110. In some embodiments, inorganic
abrasive material, e.g. inorganic abrasive particles, may be
included in the polishing layer to facilitate material removal from
the surface of the substrate. In other embodiments, the polishing
layer is substantially free of any inorganic abrasive material and
the polishing solution may be substantially free of organic or
inorganic abrasive particle or may contain organic or inorganic
abrasive particles or combination thereof. It is to be appreciated
that the polishing system 100 of FIG. 2 is only one example of a
polishing system that may be employed in connection with the
polishing pads and methods of the present disclosure, and that
other conventional polishing systems may be employed without
deviating from the scope of the present disclosure.
[0049] In another embodiment, the present disclosure relates to a
method of polishing a substrate, the method of polishing including:
providing a polishing pad according to any one of the previously
discussed polishing pads, providing a substrate, contacting the
working surface of the polishing pad with the substrate surface,
and moving the polishing pad and the substrate relative to one
another while maintaining contact between the working surface of
the polishing pad and the substrate surface. Such polishing
operation may be conducted in the presence of a polishing solution.
In some embodiments, the polishing solution is a slurry and may
include any of the previously discussed slurries. In some
embodiments, the substrate is a semiconductor wafer. The materials
comprising the semiconductor wafer surface to be polished, i.e. in
contact with the working surface of the polishing pad, may include,
but are not limited to, at least one of a dielectric material, an
electrically conductive material, a barrier/adhesion material and a
cap material. The dielectric material may include at least one of
an inorganic dielectric material, e.g. silicone oxide and other
glasses, and an organic dielectric material. The metal material may
include, but is not limited to, at least one of copper, tungsten,
aluminum, silver and the like. The cap material may include, but is
not limited to, at least one of silicon carbide and silicon
nitride. The barrier/adhesion material may include, but is not
limited to, at least one of tantalum and tantalum nitride. The
method of polishing may also include a pad conditioning or cleaning
step, which may be conducted in-situ, i.e. during polishing. Pad
conditioning may use any pad conditioner or brush known in the art,
e.g. 3M CMP PAD CONDITIONER BRUSH PB33A, 4.25 in diameter available
from the 3M Company, St. Paul, Minn. Cleaning may employ a brush,
e.g. 3M CMP PAD CONDITIONER BRUSH PB33A, 4.25 in diameter available
from the 3M Company, and/or a water or solvent rinse of the
polishing pad.
Embodiments
[0050] 1) A polishing pad comprising:
[0051] a polishing layer having a first major surface and a second
major surface opposite the first major surface;
[0052] a subpad having a first major surface and a second major
surface opposite the first major surface,
[0053] wherein the subpad is coupled to the polishing layer;
and
[0054] wherein at least 50% of the subpad, based on the total
surface area of the first major surface of the subpad, is optically
transparent. [0055] 2) The polishing pad of embodiment 1, wherein
at least 50% of the polishing layer, based on the total surface
area of the first major surface of the polishing pad, is optically
transparent. [0056] 3) The polishing pad of embodiment 2, wherein
at least 50% of the optically transparent region of the subpad
overlays the optically transparent region of the polishing pad.
[0057] 4) The polishing pad of embodiment 3, wherein the polishing
pad is optically transparent in the region of the subpad that
overlays the optically transparent region of the polishing pad.
[0058] 5) The polishing pad of any one of the previous embodiments,
wherein the subpad has a Young's Modulus of between 4000 kPa and
100 kPa, between 3000 kPa and 200 kPa, or between 300 and 2000 kPa.
[0059] 6) The polishing pad of any one of the previous embodiments,
wherein the subpad has a Shore A hardness of between 5 and 70.
[0060] 7) The polishing pad of any one of the previous embodiments,
wherein the subpad is elasctically deformable. [0061] 8) The
polishing pad of any one of the previous embodiments, wherein the
subpad has a relaxation modulus of less than 40%. [0062] 9) The
polishing pad of any one of the previous embodiments, wherein the
subpad comprises cavities or voids. [0063] 10) The polishing pad of
embodiment 9, wherein a volume percentage of the voids and cavities
is less than about 50. [0064] 11) The polishing pad of any one of
the previous embodiments, wherein the subpad has a compressibility
at 25% deflection of between 25 and 1000 kPa. [0065] 12) The
polishing pad of any one of the previous embodiments, wherein the
subpad comprises a polymer having a glass transition below room
temperature. [0066] 13) The polishing pad of any one of the
previous embodiments, wherein the subpad comprises a polymer and a
plasticizer. [0067] 14) The polishing pad of any one of the
previous embodiments, wherein the subpad comprises an acrylate or
methacrylate resin. [0068] 15) The polishing pad of any one of the
previous embodiments, wherein the polishing layer comprises pores
and asperities. [0069] 16) A method of polishing a substrate, the
method comprising:
[0070] providing a polishing pad according to any one of
embodiments 1-15;
[0071] providing a substrate;
[0072] contacting the first major surface of the polishing pad with
the substrate;
[0073] moving the polishing pad and the substrate relative to one
another while maintaining contact between the first major surface
of the polishing pad and the substrate.
EXAMPLES
TABLE-US-00001 [0074] Material designation Description Source
CN973H85 An aromatic polyester Available under the trade
designation based urethane diacrylate "CN973H85" from Sartomer
Americas, oligomer blended with 15% Exton, Pennsylvania.
2(2-ethoxyethoxy) ethyl acrylate. SR-256 A monomer, 2(2- Available
under the trade designation ethoxyethoxy) ethyl "SR 256" from
Sartomer Americas. acrylate. SR-506C A monomer, isobornyl Available
under the trade designation acrylate. "SR 506C" from Sartomer
Americas. Irgacure 651 A photoinitiator, 2,2- Available under the
trade designation Dimethoxy-1,2- "CIBA IRGACURE 651" from BASF
diphenylethan-1-one. Corp., Florham Park, New Jersey. Poron Foam A
microcellular Available under the trade designation polyurethane.
"PORON 4701-60-20062004-54T-UR" from Rogers Corporation, Chandler
Arizona. Uniplex 155 A plasticizer, diisobutyl Available under the
trade desigmation phthalate. "UNIPLEX 155" from Lanxess Coporation,
Pittsburg, Pennsylvania. CN9071 An aliphatic urethane Available
under the trade designation acrylate oligomer. "CN9071", from
Sartomer Americas. CN9021 A polyester acrylate. Available under the
trade designation "CN9021" from Sartomer Americas. 43543 Liner A 5
mil thick polyethylene Available under the trade designation
terephthalate release liner. "43543 5 mil PET release liner" from
Loparex, Hammond, Wisconsin. PL-1104 Isophoryl Acrylate Available
under the trade designation "PL-1104" from PL Industries, Ltd.,
Essington, Pennsylvania. PET-EVA A 5 mil (0.127 mm) thick
Commercially available. PET film coated with ethylene vinyl acetate
copolymer.
Test Methods:
Glass Transition Temperature Test Method
[0075] The glass transition temperature (Tg, .degree. C.) of the
prepared subpads was defined as the location of the peak of tan
delta value as determined from a dynamic mechanical analysis (DMA)
test. DMA was conducted using a dynamic mechanical analyzer, model
DMA Q800, available from TA Instrument, New Castle, Del. Subpad
samples, having a length of 13 mm and a width of 5.5 mm, were
tested in a tensile mode at a frequency of 1 Hz over a temperature
range from -60.degree. C. to 120.degree. C. at a scan rate of
5.degree. C./min. Testing results are shown in Table 1.
Light Transmission Test Method
[0076] Light transmission of the prepared subpads and several
examples was measured using a benchtop spectrophotometer, model
Color i7 from X-Rite, Inc., Grand Rapids, Mich. Data was collected
at 10 nm intervals from 800 nm to 350 nm. The sample thickness was
about 53 mils (1.34 mm). Testing results are shown in Table 2.
Stress Relaxation Test Method
[0077] Stress relaxation characteristics of the prepared subpads
were measured following ASTM D6048. Cylindrical subpad samples,
1.25 in (3.18 cm) diameter.times.53 mils (1.35 mm) thickness, were
loaded in a MTS INSIGHT Electromechanical System, from MTS Systems
Corp., Eden Prairie, Minn. and held under a constant compressive
strain (e.g. as change in the sample thickness divided by its
original, non-deformed thickness). The force applied by the sample
to the testing machine platens was measured and recorded
continuously along with the corresponding elapsed time. The stress,
.sigma., modulus at a given time, E(t), and the relaxation modulus
(%) were calculated as described below.
Stress (.sigma.) was calculated from the recorded force using the
following equation:
.sigma.(t)=Force (t)/Sample's cross section area
Modulus (E) was calculated by dividing stress (.sigma.) by the
constant strain (.epsilon..sub.c), using the following
equation:
E(t)=.sigma.(t)/.epsilon..sub.c
Relaxation Modulus (%) was calculated using the following
equation:
Relaxation Modulus (%)=[(E.sub.0-E.sub.2)/E.sub.0]*100
where E.sub.0 is the instantaneous modulus and E.sub.2 is the
modulus after two minutes of relaxation of the sample material
under constant compressive strain. The instantaneous modulus is
defined as the modulus of the sample material immediately after
starting the test. Testing results are shown in Table 1.
CMP Simulated Compression Test Method
[0078] An MTS INSIGHT Electromechanical System, from MTS Systems
Corp., Eden Prairie, Minn., was used to conduct compression cycle
testing on subpad samples. A 1.25 in (3.18 cm) diameter sample was
placed between 2 in (51 cm) diameter platens. The sample was then
put through repeated compression cycles of 0 psi (0 kPa) to 12 psi
(83 KPa) for 60 cycles at a frequency of approximately 1 Hz. This
was followed by a 15 second break The series of 60 compressions at
about 1 Hz followed by a 15 second break was repeated 299 times. A
total of 18,000 compression cycles were run on each sample.
Compression values, i.e. the difference between the thickness of
the sample when measured at 0 psi and 12 psi, was measured over the
time range of 500 to 700 seconds and then averaged to obtain an
initial compression value. Similarly, compression values were
measured over the last 200 seconds of the test and averaged to
obtain a final compression value. The difference between the two
averages is compared to estimate sample fatigue. Testing results
are shown in Table 1.
Thermal Oxide Wafer (300 mm Diameter) Removal Rate Test Method
[0079] Substrate removal rates for the following Examples were
calculated by determining the change in thickness of the layer
being polished from the initial (i.e. before polishing) thickness
and the final (i.e. after polishing) thickness and dividing this
difference by the polishing time. Thickness measurements are made
using a non-contacting, film analysis system NovaScan 3090Next
available from Nova Measuring Instruments Ltd., Rehovot, Israel.
Fifty-three points diameter scans with 2 mm edge exclusion were
employed.
Wafer Non-Uniformity Determination
[0080] Percent wafer non-uniformity was determined by calculating
the standard deviation of the change in thickness of the layer
being polished at points on the surface of the wafer (as obtained
from the above Removal Rate Test Methods), dividing the standard
deviation by the average of the changes in thickness of the layer
being polished, and multiplying the value obtained by 100, results
were therefore reported as a percentage.
300 mm Thermal Oxide Wafer Polishing Test Method
[0081] Wafers were polished using a CMP polisher available under
the trade designation REFLEXION polisher from Applied Materials,
Inc. of Santa Clara, Calif. The polisher was fitted with a 300 mm
CONTOUR head for holding 300 mm diameter wafers. A 30.5 in (77.5
cm) diameter pad was laminated to the platen of the polishing tool
with a layer of PSA. There was no break-in procedure. During this
polish, the pressures applied to the CONTOUR head's zones, zone 1,
zone 2, zone 3, zone 4, zone 5 and retaining ring were 3.0 psi
(20.7 kPa), 1.4 psi (9.7 kPa), 1.3 psi (9.0 kPa), 1.1 psi (7.6
kPa), 1.1 psi (7.6 kPa) and 3.7 psi (25.5 kPa), respectively. The
platen speed was 53 rpm and the head speed was 47 rpm. A brush type
pad conditioner, available under the trade designation 3M CMP PAD
CONDITIONER BRUSH PB33A, 4.25 in diameter available from the 3M
Company, St. Paul, Minn. was mounted on the conditioning arm and
used at a speed of 81 rpm with a 3 lbf downforce. The pad
conditioner was swept across the surface of the pad via a
sinusoidal sweep, with 100% in-situ conditioning. The polishing
solution was a slurry, available under the trade designation WIN
W7300 A34 and WIN W7300 B34 from Cabot Microelectronics
Corporation, Aurora, Ill. Prior to use, the WIN W7300 A34 and WIN
W7300 B34 is mixed in a ratio of 4:1 and 30% hydrogen peroxide was
added such that the final volume ratios of A34+B34/30%
H.sub.2O.sub.2 were 98/2. Polishing was conducted at a solution
flow rate of 100 mL/min. Fifty thermal oxide monitor wafers were
polished for 1 minute and subsequently measured. 300 mm diameter
Thermal Oxide monitor wafers were obtained from Advantiv
Technologies Inc., Freemont, Calif. The wafer stack was as follows:
300 mm prime Si substrate+thermal oxide 20KA.
300 mm Copper Wafer Polishing Test Method with In-Situ Rate
Monitoring (ISRM)
[0082] The copper wafer polishing method used the same 300 mm
REFLEXION equipment and brush as the 300 mm thermal oxide wafer
polishing. During this polish, the pressures applied to the CONTOUR
head's zones, zone 1, zone 2, zone 3, zone 4, zone 5 and retaining
ring were 4.6 psi (31.7 kPa), 2.2 psi (15.2 kPa), 2.1 psi (14.5
kPa), 2.0 psi (13.8 kPa), 2.0 psi (13.8 kPa) and 5.3 psi (36.5
kPa), respectively. The polish recipe was run with the ISRM
software enabled. The polishing solution was a slurry, available
under the trade designation CSL 9044c from Planar Solutions LLC,
Adrian, Mich., USA. Prior to use, CSL 9044c was diluted with DI
water and 30% hydrogen peroxide was added such that the final
volume ratios of 9044c/DI water/H.sub.2O.sub.2 were 9/88/3.
Polishing was conducted at a solution flow rate of 150 mL/min. The
polish process began with running ten dummy thermal oxide wafers
followed by a Cu wafer. 300 mm diameter Cu monitor wafers were
obtained from Advantiv Technologies Inc., Freemont, Calif. The
wafer stack was as follows: 300 mm prime Si substrate+thermal oxide
3KA+TaN 250A+PVD Cu 1KA+e-Cu 15KA+anneal. Thickness measurements of
the Cu were not taken as the goal of this test was to observe the
ISRM signal for a change when the wafer is completely cleared of
Cu. At the times indicated in Table 5, the ISRM signal was
recorded. The wafer polished until a change in signal was observed
and an appropriate amount of overpolish completed.
Subpad 1
[0083] 97.6 lbs (44.3 kg) CN973H85, 48.0 lbs (21.8 kg) SR-506C,
14.4 lbs (6.53 kg) SR-256 and 0.32 lbs (145 g) Irgacure 651 were
mixed at room temperature under vacuum to degas. The obtained
mixture was cast between two layers of 43543 Liner and cured via
exposure under UV light with a dose of 2,000 mJ/cm.sup.2. After
removal of the liners, the thickness of the obtained 38 inch (0.965
m) wide cured film was 53.+-.1 mils (1.34.+-.0.025 mm).
Subpad 2
[0084] 106.7 lbs (48.4 kg) CN973H85, 53.3 lbs (24.2 kg) SR-506C and
0.32 lbs (145 g) Irgacure 651 were mixed at room temperature under
vacuum to degas. The obtained mixture was cast between two layers
of 43543 Liner and cured via exposure under UV light with a dose of
2,000 mJ/cm.sup.2. After removal of the liners, the thickness of
the obtained 36 inch (0.914 mm) wide cured film was 53.+-.1 mils
(1.34.+-.0.025 mm).
Subpad 3
[0085] 100 g CN9071, 120 g Uniplex 155 and 0.44 g Irgacure 651 were
mixed at room temperature under vacuum to degas. The obtained
mixture was cast between two layers of 43543 Liner, and cured via
exposure under UV light with a dose of 2,500 mJ/cm.sup.2. After
removal of the liners, the thickness of the obtained 8 in (20.3 cm)
wide cured film was 53.+-.1 mils (1.34.+-.0.025 mm).
Subpad 4
[0086] 100 g CN9021, 40 g Uniplex 155 and 0.30 g Irgacure 651 were
mixed at room temperature under vacuum to degas. After removal of
the liners, the obtained mixture was cast between two layers of
43543 Liner and cured via exposure under UV light with a dose of
2,500 mJ/cm.sup.2. The thickness of the obtained 8 in (20.3 cm)
wide cured film was 53.+-.1 mils (1.34.+-.0.025 mm).
Subpad 5
[0087] 100 lbs (45.4 kg) CN973H85, 40 lbs (18.1 kg) PL-1104 and
0.28 lbs (127 g) Irgacure 651 were mixed at room temperature under
vacuum to degas. The obtained mixture was cast between a layer of
PET-EVA film and a layer of 43543 Liner and cured via exposure
under UV light with a dose of 2,000 mJ/cm.sup.2. The 43543 Liner
was removed, while the PET-EVA film remained attached to the cured
film. The thickness of the obtained 38 in (0.965 m) wide cured film
with PET-EVA film was 58.+-.1 mil (1.47.+-.0.025 mm) and.
Subpad 6
[0088] Subpad 6 is a perforated film with squared through holes,
made from the film of Subpad 5. The through holes were fabricated
on the film using an Epilog Laser Engraver, model Fusion 40 laser,
from Epilog Corp. (Golden, Colo.). The holes are arranged in a
square grid array with a hole width of 1 mm and a hole pitch of 5
mm.
Subpad 7
[0089] Subpad 7 was prepared similarly to Subpad 6, except the
square grid array had a pitch of 2.5 mm.
Subpad 8
[0090] Subpad 8 was prepared from the film of Subpad 5. Square
blind holes at a depth of 0.1 mm were ablated in the film using the
Epilog Laser Engraver. The holes are arranged in a squared grid
array with hole width of 1 mm and hole pitch of 5 mm.
Subpad 9
[0091] Subpad 9 was prepared similarly to Subpad 6, except the hole
width was 2 mm.
Example 1
[0092] A polishing pad according to FIG. 1 was prepared with the
following procedure. The polishing layer was prepared with the
procedure described in U.S. Pat. No. 6,285,001. More specifically,
the polishing layer included a plurality of precisely shaped
asperities and a plurality of precisely shaped pores, the
asperities being tapered cylinders of height 18 .mu.m, diameter 50
.mu.m, pitch 90 .mu.m with bearing area of 24%. The pores were
generally hemispherical shaped with depth 30 .mu.m, diameter 60
.mu.m, and pitch 90 .mu.m. Both the plurality of precisely shaped
asperities and the plurality of precisely shaped pores were
configured in a square array pattern.
[0093] The polymeric material used in the embossing process to form
the polishing layer was a thermoplastic polyurethane, available
under the trade designation Estane 58277 resin from Lubrizol
Corporation (Wickliffe, Ohio). The polyurethane had a durometer of
about 92 Shore A and the polishing layer had thickness of about 22
mils (0.559 mm). During the embossing process, a 2.96 mil (0.0752
mm) PET film was brought into contact and adhered to the back
surface the polishing layer.
[0094] The polishing pad was formed through multiple lamination
steps, using an AGL 4400 laminator from Advanced Greig Laminators,
Inc (Deforest, Wis.). The first step was lamination of a subpad
(Subpad 1, after removing the 43543 Liners) to a 32 in (81
cm).times.32 in (81 cm).times.10 mil (0.25 mm) PET sheet
prelaminated with an adhesive available under the trade designation
3M ADHESIVE TRANSFER TAPE 468MP (from the 3M Company, St. Paul,
Minn.) on the side to be laminated to the polishing layer. The
second step was lamination of a rubber-based adhesive on the
opposite side of Subpad 1, which was used to laminate the polishing
pad to the platen of a polishing tool during polishing testing. The
third step was the lamination of another layer of 3M ADHESIVE
TRANSFER TAPE 468MP to the exposed surface of the PET sheet that
had previously been laminated to Subpad 1 in the first lamination
step. The fourth step was the lamination of the polishing layer to
the exposed surface of 3M ADHESIVE TRANSFER TAPE 468MP of the third
3, yielding Example 1. A 30.5 in (76.2 cm) diameter pad was die cut
using conventional techniques, forming the final polishing pad.
Example 2
[0095] A polishing pad was prepared similarly to Example 1, except
Subpad 1 was replaced by Subpad 2, yielding Example 2.
Comparative Example 3
[0096] Comparative Example 3 was prepared similarly to Example 1,
except Subpad 1 was replaced by a sheet of Poron Foam, yielding
Comparative Example 3 (CE-3).
TABLE-US-00002 TABLE 1 Average Average compression compression
Stress at Stress between 500 during the 5% Strain Relax and 700 s
last 200 s T.sub.g Sample (kPa) (%) (mils) (mil) (.degree. C.)
Subpad 1 102.0 6.3 1.9 1.9 18 Subpad 2 119.7 34.5 1.4 1.5 20 Subpad
3 20.4 22.3 3.0 3.0 * Subpad 4 15.9 17.8 3.2 3.3 * Subpad 5 87.6
12.2 2.0 2.0 6 Subpad 6 39.3 9.56 4.4 4.4 6 Subpad 7 34.3 10.9 4.3
4.3 6 Subpad 8 83.2 9.3 2.3 2.3 6 Subpad 9 13.5 11.2 5.5 5.1 6
Poron Foam 43 26.3 3.5 3.3 N/A * Sample was too soft to be measured
by DMA.
TABLE-US-00003 TABLE 2 Sample Wavelength (nm) % Transmission Subpad
1 400 to 750 90-93 Subpad 2 400 to 750 88-92 Subpad 3 400 to 750
91-93 Subpad 4 400 to 750 90-93 Subpad 5 400 to 750 90-94 Subpad 6
400 to 750 87-92 Example 1 400 to 750 40-57 Example 2 400 to 750
56-82 Poron Foam 400 to 750 0 CE-3 400 to 750 0
TABLE-US-00004 TABLE 3 Example 1 Thermal Oxide Polishing Results
Polishing Removal Non- Time Rate Uniformity (min) (.ANG./min) (%) 1
1 88 5 77 6 10 76 8 15 81 8 20 80 6 25 77 5 30 83 8 35 84 13 40 82
9 45 80 14 50 79 5
TABLE-US-00005 TABLE 4 Example 2 Thermal Oxide Polishing Results
Polishing Removal Non- Time Rate Uniformity (min) (.ANG./min) (%) 1
-- -- 5 80 3 10 75 4 15 74 7 20 76 6 25 74 4 30 72 6 35 75 5 40 73
8 45 77 7 50 72 5
TABLE-US-00006 TABLE 5 Example 1 Copper Polishing ISRM Signal
Results Polish Time ISRM (min) Signal 1 44 5 43 10 44 15 42 20 42
25 41 30 38 35 39 40 39 45 40 50 40 55 40 60 33 65 29 70 27 75 27
80 28 85 28 89 28
For CE-3, as the transmission is zero (Table 2), the ISRM signal is
expected to be zero and use of visible light endpoint detection is
not possible.
* * * * *