U.S. patent application number 13/992554 was filed with the patent office on 2013-11-28 for chemical mechanical polishing pad and chemical mechanical polishing method using same.
This patent application is currently assigned to JSR CORPORATION. The applicant listed for this patent is Satoshi Kamo, Kotaro Kubo, Ayako Maekawa, Naoki Nishiguchi, Takahiro Okamoto, Hirotaka Shida. Invention is credited to Satoshi Kamo, Kotaro Kubo, Ayako Maekawa, Naoki Nishiguchi, Takahiro Okamoto, Hirotaka Shida.
Application Number | 20130316621 13/992554 |
Document ID | / |
Family ID | 46207081 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130316621 |
Kind Code |
A1 |
Maekawa; Ayako ; et
al. |
November 28, 2013 |
CHEMICAL MECHANICAL POLISHING PAD AND CHEMICAL MECHANICAL POLISHING
METHOD USING SAME
Abstract
A chemical mechanical polishing pad includes a polishing layer
that is formed of a composition that includes a polyurethane, the
polishing layer having a specific gravity of 1.1 to 1.3 and a
thermal conductivity of 0.2 W/mK or more.
Inventors: |
Maekawa; Ayako; (Yokkaichi,
JP) ; Kamo; Satoshi; (Yokkaichi, JP) ;
Nishiguchi; Naoki; (Yokkaichi, JP) ; Shida;
Hirotaka; (Sumida-ku, JP) ; Okamoto; Takahiro;
(Yokkaichi, JP) ; Kubo; Kotaro; (Urawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Maekawa; Ayako
Kamo; Satoshi
Nishiguchi; Naoki
Shida; Hirotaka
Okamoto; Takahiro
Kubo; Kotaro |
Yokkaichi
Yokkaichi
Yokkaichi
Sumida-ku
Yokkaichi
Urawa |
|
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
JSR CORPORATION
Tokyo
JP
|
Family ID: |
46207081 |
Appl. No.: |
13/992554 |
Filed: |
December 2, 2011 |
PCT Filed: |
December 2, 2011 |
PCT NO: |
PCT/JP2011/077904 |
371 Date: |
August 7, 2013 |
Current U.S.
Class: |
451/59 ; 451/526;
451/539 |
Current CPC
Class: |
B24B 37/22 20130101;
B24B 1/00 20130101; B24B 37/24 20130101 |
Class at
Publication: |
451/59 ; 451/526;
451/539 |
International
Class: |
B24B 37/24 20060101
B24B037/24; B24B 1/00 20060101 B24B001/00; B24B 37/22 20060101
B24B037/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2010 |
JP |
2010-272450 |
Claims
1. A chemical mechanical polishing pad comprising a polishing layer
that is formed of a composition comprising a polyurethane, wherein
the polishing layer has a specific gravity of from 1.1 to 1.3 and a
thermal conductivity of 0.2 W/mK or more.
2. The chemical mechanical polishing pad according to claim 1,
further comprising a laminate which comprises the polishing layer
and a support layer that is formed on one side of the polishing
layer, wherein the laminate has a thermal conductivity of 0.2 W/mK
or more.
3. The chemical mechanical polishing pad according to claim 1,
wherein the polishing layer has a residual strain of from 2 to 10%
when applying tension to the polishing layer.
4. The chemical mechanical polishing pad according to claim 1,
wherein the polishing layer has a volume change ratio of from 0.8
to 5.0% when immersed in water at 23.degree. C. for 24 hours.
5. The chemical mechanical polishing pad according to claim 2,
wherein the support layer has a compressibility of 5% or more.
6. The chemical mechanical polishing pad according to claim 1,
wherein the polyurethane is a thermoplastic polyurethane.
7. The chemical mechanical polishing pad according to claim 1,
wherein the composition further comprises water-soluble
particles.
8. A chemical mechanical polishing method comprising chemically and
mechanically polishing a polishing target with the chemical
mechanical polishing pad according to claim 1.
9. The chemical mechanical polishing pad according to claim 2,
wherein the polishing layer has a residual strain of from 2 to 10%
when applying tension to the polishing layer.
10. The chemical mechanical polishing pad according to claim 2,
wherein the polishing layer has a volume change ratio of from 0.8
to 5.0% when immersed in water at 23.degree. C. for 24 hours.
11. The chemical mechanical polishing pad according to claim 3,
wherein the polishing layer has a volume change ratio of from 0.8
to 5.0% when immersed in water at 23.degree. C. for 24 hours.
12. The chemical mechanical polishing pad according to claim 2,
wherein the polyurethane is a thermoplastic polyurethane.
13. The chemical mechanical polishing pad according to claim 3,
wherein the polyurethane is a thermoplastic polyurethane.
14. The chemical mechanical polishing pad according to claim 4,
wherein the polyurethane is a thermoplastic polyurethane.
15. The chemical mechanical polishing pad according to claim 5,
wherein the polyurethane is a thermoplastic polyurethane.
16. The chemical mechanical polishing pad according to claim 2,
wherein the composition further comprises water-soluble
particles.
17. The chemical mechanical polishing pad according to claim 3,
wherein the composition further comprises water-soluble
particles.
18. The chemical mechanical polishing pad according to claim 4,
wherein the composition further comprises water-soluble
particles.
19. The chemical mechanical polishing pad according to claim 5,
wherein the composition further comprises water-soluble
particles.
20. The chemical mechanical polishing pad according to claim 6,
wherein the composition further comprises water-soluble particles.
Description
TECHNICAL FIELD
[0001] The present invention relates to a chemical mechanical
polishing pad and a chemical mechanical polishing method using the
chemical mechanical polishing pad.
BACKGROUND ART
[0002] A porous nonwoven fabric obtained by impregnating a nonwoven
fabric with a polyurethane solution, or a polyurethane molded
product has been used as a polishing pad for polishing glass or a
semiconductor material. The following polyurethane polishing pads
have been studied as a chemical mechanical polishing pad suitable
for chemical mechanical polishing (hereinafter may be referred to
as "CMP") that planarizes the surface of a semiconductor
substrate.
[0003] JP-T-8-500622 discloses a polishing pad wherein a
filler-like component is dispersed in a polyurethane, and
JP-A-2000-17252 and Japanese Patent No. 3956364 disclose a
polishing pad formed using a polyurethane foam, for example.
[0004] When performing CMP using such a polishing pad, friction may
produce heat when the polishing target surface (e.g., the surface
of a wafer) and the surface of the polishing pad rub against each
other, and the temperature of the surface of the polishing pad may
increase locally. Since the polishing performance of the polishing
pad changes due to a local increase in temperature of the surface
of the polishing pad, the planarity of the polishing target surface
may become worse, or polishing defects (scratches) or the like may
be caused. Moreover, the polishing performance of the entire
polishing pad may change when frictional heat that is produced
during CMP performed over a long time is accumulated in the
polishing pad, and an increase in temperature of the polishing pad
continuously occurs. In order to solve the problems caused by
frictional heat, JP-A-7-142432 and JP-A-2003-197586 disclose a CMP
system in which a cooling mechanism (e.g., coolant circulation
system) is incorporated in a platen that holds the polishing
pad.
SUMMARY OF THE INVENTION
Technical Problem
[0005] However, since a related-art chemical mechanical polishing
pad has insufficient thermal conductivity, an improvement achieved
by improving a CMP system (e.g., cooling mechanism) has been
limited. In particular, a polyurethane foam that is widely used as
a material for the polishing pad has a low thermal conductivity due
to its foamed structure, and is used as a residential insulation. A
polishing pad composed of a polyurethane foam having such
properties has problems such as (1) a local increase in temperature
of the surface of the polishing pad occurs due to frictional heat,
and the polishing performance deteriorates, and (2) the temperature
of the entire polishing pad increases due to CMP performed for a
long time, and the polishing performance changes since frictional
heat is not easily dissipated.
[0006] Several aspects of the invention may solve the above
problems, and may provide a chemical mechanical polishing pad that
can improve the Planarity of the polishing target surface, suppress
occurrence of polishing defects (scratches), and maintain stable
polishing performance during CMP performed for a long time, and a
chemical mechanical polishing method that utilizes the chemical
mechanical polishing pad.
Solution to Problem
[0007] The invention was conceived in order to solve at least some
of the above problems, and may be implemented as the following
aspects or application examples.
Application Example 1
[0008] According to one aspect of the invention, a chemical
mechanical polishing pad includes a polishing layer that is formed
of a composition that includes a polyurethane, the polishing layer
having a specific gravity of 1.1 to 1.3 and a thermal conductivity
of 0.2 W/mK or more.
Application Example 2
[0009] The chemical mechanical polishing pad according to
Application Example 1 may include a laminate that includes the
polishing layer and a support layer that is formed on one side of
the polishing layer, the laminate having a thermal conductivity of
0.2 W/mK or more.
Application Example 3
[0010] In the chemical mechanical polishing pad according to
Application Example 1 or 2, the polishing layer may have a residual
strain of 2 to 10% when applying tension to the polishing
layer.
Application Example 4
[0011] In the chemical mechanical polishing pad according to any
one of Application Examples 1 to 3, the polishing layer may have a
volume change ratio of 0.8 to 5.0% when immersed in water at
23.degree. C. for 24 hours.
Application Example 5
[0012] In the chemical mechanical polishing pad according to
Application Example 2, the support layer may have a compressibility
of 5% or more.
Application Example 6
[0013] In the chemical mechanical polishing pad according to any
one of Application Examples 1 to 5, the polyurethane may be a
thermoplastic polyurethane.
Application Example 7
[0014] In the chemical mechanical polishing pad according to any
one of Application Examples 1 to 6, the composition may further
include water-soluble particles.
Application Example 8
[0015] According to another aspect of the invention, a chemical
mechanical polishing method includes chemically and mechanically
polishing a polishing target using the chemical mechanical
polishing pad according to any one of Application Examples 1 to
7.
Advantageous Effects of the Invention
[0016] Since the chemical mechanical polishing pad according to one
aspect of the invention includes the polishing layer that has a
specific gravity and a thermal conductivity within the specific
ranges, it is possible to improve the planarity of the polishing
target surface, suppress occurrence of polishing defects
(scratches), and maintain stable polishing performance during CMP
performed for a long time.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a schematic view illustrating the concept of the
residual strain of a polishing layer when applying tension to the
polishing layer.
[0018] FIG. 2A is an enlarged view of an area I illustrated in FIG.
1.
[0019] FIG. 2B is an enlarged view of an area I illustrated in FIG.
1.
[0020] FIG. 2C is an enlarged view of an area I illustrated in FIG.
1.
[0021] FIG. 2D is an enlarged view of an area I illustrated in FIG.
1.
[0022] FIG. 2E is an enlarged view of an area I illustrated in FIG.
1.
[0023] FIG. 3A is a schematic view illustrating the concept of the
volume change ratio of a polishing layer.
[0024] FIG. 3B is a schematic view illustrating the concept of the
volume change ratio of a polishing layer.
[0025] FIG. 4A is a schematic view illustrating the concept of the
durometer D hardness of a polishing layer.
[0026] FIG. 4B is a schematic view illustrating the concept of the
durometer D hardness of a polishing layer.
[0027] FIG. 5A is a schematic view illustrating the concept of the
surface hardness of a polishing layer.
[0028] FIG. 5B is a schematic view illustrating the concept of the
surface hardness of a polishing layer.
DESCRIPTION OF EMBODIMENTS
[0029] Exemplary embodiments of the invention are described in
detail below. Note that the term "wet state" used herein refers to
the state of the polishing layer that has been immersed in water at
23.degree. C. for 4 hours or more. The term "hardness" used herein
refers to durometer D hardness, and the term "surface hardness"
used herein refers to universal hardness (HU: N/mm.sup.2). Note
that the surface hardness of the polishing layer in the wet state
is indicated by universal hardness (HU: N/mm.sup.2) measured when
applying a constant pressure to the polishing layer (see the
examples).
1. CHEMICAL MECHANICAL POLISHING PAD
[0030] A chemical mechanical polishing pad according to one
embodiment of the invention includes a polishing layer that forms
at least one side of the chemical mechanical polishing pad. The
polishing layer has a specific gravity of 1.1 to 1.3 and a thermal
conductivity of 0.2 W/mK or more. The details of the chemical
mechanical polishing pad according to one embodiment of the
invention are described below.
1.1. Polishing Layer
[0031] The polishing layer included in the chemical mechanical
polishing pad according to one embodiment of the invention is
formed by the following production method using a composition that
includes a polyurethane (hereinafter may be referred to as
"composition"). The structure and the type of the polyurethane
included in the composition are not particularly limited as long as
the polishing layer has a specific gravity and a thermal
conductivity within the above ranges. An optimum polyurethane may
be appropriately selected taking account of the material of the
polishing target, affinity to the slurry used for polishing, and
the like. Note that the term "polishing layer" used herein refers
to a single layer having a surface that comes in contact with the
polishing target during chemical mechanical polishing (hereinafter
referred to as "polishing surface"). The chemical mechanical
polishing pad may include an additional layer that does not have a
polishing surface between the polishing layer and a support layer.
Such an additional layer does not fall under the term "polishing
layer".
[0032] A polyurethane-containing polishing layer is normally
classified into a foamed polishing layer and a non-foamed polishing
layer. Since the non-foamed polishing layer that is widely used at
present has a specific gravity and a hardness higher than those of
the foamed polishing layer due to its structure, the non-foamed
polishing layer is elastically deformed to a small extent when
coming in contact with roughness of the polishing target surface
(e.g., the surface of a wafer). Therefore, the polishing target
surface is sufficiently planarized. However, since the non-foamed
polishing layer has higher hardness than the foamed polishing
layer, polishing defects (e.g., scratches) may increase due to
polishing waste or pad waste present between the polishing target
surface and the polishing layer.
[0033] The foamed polishing layer tends to have a low specific
gravity and low hardness due to its structure. Therefore, since
polishing waste or pad waste that present between the polishing
target surface (e.g., the surface of a wafer) and the polishing
layer is captured by the soft surface of the polishing layer, and
is not strongly pressed against the polishing target surface,
occurrence of polishing defects can be suppressed. However, since
the foamed polishing layer is elastically deformed to a large
extent so as to follow roughness of the polishing target surface,
the polishing target surface may not be sufficiently planarized.
Accordingly, it has been considered that it is difficult to improve
the planarity of the polishing target surface (e.g., the surface of
a wafer) while suppressing occurrence of polishing defects (e.g.,
scratches).
[0034] The inventors of the invention found that it is possible to
improve the planarity of the polishing target surface (e.g., the
surface of a wafer) while suppressing occurrence of polishing
defects (e.g., scratches), and achieve stable polishing performance
even during CMP performed over a long time by forming the polishing
layer using a composition that includes a polyurethane while
controlling the specific gravity and the thermal conductivity of
the polishing layer.
1.1.1. Composition
1.1.1.1. Polyurethane
[0035] The structure and the type of the polyurethane included in
the composition are not particularly limited. When the polishing
target is a semiconductor wafer on which wirings are formed, it is
preferable to use a thermoplastic polyurethane in order to improve
the planarity of the polishing target surface while suppressing
occurrence of polishing defects (scratches). It is more preferable
to use a thermoplastic polyurethane that includes a repeating unit
derived from at least one compound selected from an alicyclic
isocyanate and an aromatic isocyanate. A polishing layer that
exhibits excellent flexibility can be formed when the composition
includes a thermoplastic polyurethane having such a chemical
structure. In this case, since polishing waste or pad waste present
between the polishing target surface and the polishing layer is
captured by the soft surface of the polishing layer, and is not
strongly pressed against the polishing target surface, occurrence
of polishing defects can be suppressed. When the polishing layer is
formed using a polyurethane obtained by crosslinking a thermally
crosslinkable polyurethane (thermosetting polyurethane), it is
difficult to provide the polishing layer with sufficient
flexibility. This makes it difficult to suppress occurrence of
polishing defects.
[0036] A polishing layer formed using a polyurethane which is
obtained by crosslinking a thermally crosslinkable polyurethane and
in which the molecular chains are strongly bonded, swells to only a
small extent even when coming in contact with water (i.e., surface
hardness does not decrease in the wet state) as compared with a
polishing layer formed using a thermoplastic polyurethane.
Therefore, when the polishing layer includes a crosslinked
polyurethane, polishing waste or pad waste present between the
polishing target surface and the polishing layer is captured by the
surface of the polishing layer having high surface hardness, and is
strongly pressed against the polishing target surface. This makes
it difficult to suppress occurrence of polishing defects.
[0037] When forming the polishing layer using the composition that
includes a thermoplastic polyurethane that includes a repeating
unit derived from at least one compound selected from an alicyclic
isocyanate and an aromatic isocyanate, it is possible to easily
control the specific gravity, the hardness, and the like of the
polishing layer since the crystallinity of the polyurethane can be
easily controlled.
[0038] Examples of the alicyclic isocyanate include isophorone
diisocyanate (IPDI), norbornene diisocyanate, hydrogenated
4,4'-diphenylmethane diisocyanate (hydrogenated MDI), and the like.
These alicyclic isocyanates may be used either alone or in
combination.
[0039] Examples of the aromatic isocyanate include 2,4-tolylene
diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane
diisocyanate, 2,4'-diphenylmethane diisocyanate,
4,4'-diphenylmethane diisocyanate, naphthalene diisocyanate,
1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene
diisocyanate, p-xylene diisocyanate, and the like. Among these,
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and
4,4'-diphenylmethane diisocyanate are preferable since a reaction
with a hydroxyl group can be easily controlled. These aromatic
isocyanates may be used either alone or in combination.
[0040] The thermoplastic polyurethane included in the composition
may include a repeating unit derived from the alicyclic isocyanate
and a repeating unit derived from the aromatic isocyanate, or may
further include a repeating unit derived from an additional
isocyanate other than the alicyclic isocyanate and the aromatic
isocyanate. Examples of the additional isocyanate include aliphatic
diisocyanates such as ethylene diisocyanate,
2,2,4-trimethylhexamethylene diisocyanate, and 1,6-hexamethylene
diisocyanate.
[0041] It is preferable that the thermoplastic polyurethane
included in the composition include a repeating unit derived from
an alicyclic isocyanate. When the thermoplastic polyurethane
includes a repeating unit derived from an alicyclic isocyanate, the
thermoplastic polyurethane exhibits appropriate hardness. Moreover,
it is possible to more appropriately control the surface hardness
of the polishing layer in the wet state, and provide the polishing
layer with higher flexibility.
[0042] It is preferable that the thermoplastic polyurethane
included in the composition further include a repeating unit
derived from at least one compound selected from a polyether
polyol, a polyester polyol, a polycarbonate polyol, and a
polyolefin polyol. When the thermoplastic polyurethane includes a
repeating unit derived from at least one compound selected from
these polyols, the thermoplastic polyurethane tends to exhibit
improved water resistance.
[0043] The thermoplastic polyurethane included in the composition
may include a repeating unit derived from a chain extender.
Examples of the chain extender include low-molecular-weight
dihydric alcohols such as ethylene glycol, propylene glycol,
1,3-propanediol, 1,3-butylene glycol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol,
1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene
glycol, triethylene glycol, and 1,4-bis(2-hydroxyethoxy)benzene.
Among these, ethylene glycol, propylene glycol, 1,3-propanediol,
1,3-butylene glycol, 1,4-butanediot, 1,5-pentanediol, and
1,6-hexanediol are preferable, and 1,4-butanediol is more
preferable, since a reaction with an isocyanate group can be easily
controlled.
[0044] The content of a repeating unit derived from at least one
compound selected from an alicyclic isocyanate and an aromatic
isocyanate in the thermoplastic polyurethane included in the
composition is preferably 2 to 60 mass %, and more preferably 3 to
55 mass %. When the content of a repeating unit derived from at
least one compound selected from an alicyclic isocyanate and an
aromatic isocyanate in the thermoplastic polyurethane is within the
above range, the thermoplastic polyurethane exhibits appropriate
hardness. Moreover, it is possible to appropriately control the
surface hardness of the polishing layer in the wet state, and
provide the polishing layer with higher flexibility.
[0045] The thermoplastic polyurethane included in the composition
may be produced by an arbitrary common polyurethane production
method (e.g., known batch method or prepolymer method).
1.1.1.2. Water-Absorbing Polymer Compound
[0046] The composition may further include an additional polymer
compound other than the thermoplastic polyurethane. The additional
polymer compound that may be included in the composition is
preferably a polymer compound that has a water absorption of 3 to
3000% (hereinafter may be referred to as "water-absorbing polymer
compound"). When the composition includes the water-absorbing
polymer compound, the polishing layer exhibits moderate
water-absorbing properties, and it is possible to easily control a
change in volume of the polishing layer that may occur when the
polishing layer swells due to absorption of water.
[0047] The additional polymer compound is more preferably a
water-absorbing polymer compound that includes at least one bond
selected from an ether bond, an ester bond, and an amide bond.
[0048] Examples of the water-absorbing polymer compound that
includes an ether bond include polyoxyethylene, a polyoxyethylene
alkyl ether, a polyoxyethylene alkylphenol ether, a poly(ether
ester amide), a poly(ether amide imide), polypropylene glycol,
polyoxypropylene butyl ether, polyoxypropylene glyceryl ether,
polyoxypropylene sorbitol, an oxyethylene-epichlorohydrin
copolymer, a methoxypolyethylene glycol (meth)acrylate copolymer,
polyoxyethylene lauryl ether, polyoxyethylene cetyl ether,
polyoxyethylene oleyl ether, polyoxyethylene oleyl cetyl ether,
polyoxyethylene polyoxypropylene glycol, polyoxyethylene
polyoxypropylene butyl ether, polyoxyethylene polyoxypropylene
hexylene glycol ether, polyoxyethylene polyoxypropylene
trimethylolpropane, polyoxyethylene polyoxypropylene glyceryl
ether, a copolymer of an olefin and a monomer that includes an
ether bond, a chlorine-containing polyether, a polyacetal resin, an
alkyl glucoside, a polyoxyethylene fatty acid amine, and the
like.
[0049] Examples of the water-absorbing polymer compound that
includes an ester bond include a polyoxyethylene fatty acid ester,
a sucrose fatty acid ester, a sorbitan fatty acid ester, a
polyoxyethylene sorbitan fatty acid ester, a glycerol fatty acid
ester, an acrylate copolymer (acrylic rubber), and the like.
Examples of the polyoxyethylene fatty acid ester include
polyethylene glycol monostearate, polyethylene glycol laurate,
polyethylene glycol monooleate, polyethylene glycol distearate, and
the like.
[0050] Examples of the water-absorbing polymer compound that
includes an amide bond include a fatty acid alkanolamide, a
modified polyamide resin, and the like.
[0051] The polystyrene-reduced weight average molecular weight of
the water-absorbing polymer compound determined by gel permeation
chromatography is preferably 500 to 1,000,000, and more preferably
5000 to 500,000.
[0052] The water absorption of the water-absorbing polymer compound
may be determined in accordance with JIS K 6258 (see below).
Specifically, the water-absorbing polymer compound is formed into a
sheet having a thickness of 2 mm. The sheet is cut to dimensions of
2.times.2 cm, and immersed in water at 23T for 24 hours. The mass
(M1) of the sheet in air before immersion and the mass (M3) of the
sheet in air after immersion are measured, and the mass change
ratio is calculated by the following expression (1), and taken as
the water absorption.
Water absorption (%)=((M3-M1)/M1).times.100 (1)
[0053] The content of the water-absorbing polymer compound in the
composition is preferably 1 to 20 mass %, more preferably 3 to 15
mass %, and particularly preferably 5 to 10 mass %, based on the
total content (=100 mass %) of the thermoplastic polyurethane and
the water-absorbing polymer compound. When the content of the
water-absorbing polymer compound in the composition is within the
above range, the volume change ratio of the polishing layer in the
wet state can be easily controlled to 0.8 to 5.0%. When the volume
change ratio of the polishing layer is within the above range, the
surface of the polishing layer is moderately softened when the
polishing layer absorbs water. Therefore, the polishing target
surface can be sufficiently planarized, and occurrence of polishing
defects (scratches) can be suppressed.
1.1.1.3. Water-Soluble Particles
[0054] The composition may further include water-soluble particles.
It is preferable that the water-soluble particles be uniformly
dispersed in the composition. In this case, a polishing layer in
which the water-soluble particles are uniformly dispersed can be
obtained.
[0055] When the polishing layer that includes the water-soluble
particles comes in contact with a polishing aqueous dispersion that
includes abrasive grains and chemicals (hereinafter may be referred
to as "slurry"), the water-soluble particles are removed from the
surface of the polishing layer, so that pores that retain the
slurry are formed. In this case, the slurry can be sufficiently
retained in the pores that are formed in the surface of the
polishing layer by utilizing the water-soluble particles instead of
using a polyurethane foam having a cell structure. It is also
possible to control the surface hardness of the polishing layer in
the wet state by utilizing the pores formed in of the polishing
layer. Moreover, the specific gravity of the polishing layer can be
increased by utilizing particles having a high specific gravity as
the water-soluble particles.
[0056] When the composition that includes the thermoplastic
polyurethane includes the water-soluble particles, the following
advantages (1) to (3) can be obtained. (1) Since the water-soluble
particles serve as a reinforcing agent (e.g., filler), elastic
deformation of the polishing layer can be reduced, and the
planarity of the polishing target surface can be improved. (2)
Since a non-foamed polishing layer is formed, the polishing layer
exhibits excellent mechanical strength. (3) Since it is unnecessary
to uniformly control a foamed cell structure, productivity can be
improved.
[0057] Examples of the water-soluble particles include, but are not
limited to, organic water-soluble particles and inorganic
water-soluble particles. Specific examples of the water-soluble
particles include a substance that is dissolved in water (e.g.,
water-soluble polymer), and a substance that swells or gels when
coming in contact with water and is removed from the surface of the
polishing layer (e.g., water-absorbing resin).
[0058] Examples of a material for forming the organic water-soluble
particles include a saccharide (e.g., polysaccharide (e.g., starch,
dextrin, and cyclodextrin), lactose, and mannitol), a cellulose
(e.g., hydroxypropyl cellulose and methyl cellulose), a protein,
polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid,
polyethylene oxide, sulfonated polyisoprene, a sulfonated isoprene
copolymer, and the like.
[0059] Examples of a material for forming the inorganic
water-soluble particles include potassium acetate, potassium
nitrate, potassium carbonate, potassium hydrogen carbonate,
potassium bromide, potassium phosphate, potassium sulfate,
magnesium sulfate, calcium nitrate, and the like.
[0060] These materials may be used either alone or in combination
when forming the organic water-soluble particles or the inorganic
water-soluble particles. It is preferable that the water-soluble
particles be solid from the viewpoint of adjusting the mechanical
strength (e.g., hardness) of the polishing layer to an appropriate
value.
[0061] The composition preferably includes the water-soluble
particles in an amount of 3 to 150 parts by mass based on 100 parts
by mass of the thermoplastic polyurethane. When the amount of the
water-soluble particles is within the above range, it is possible
to form a polishing layer that achieves a high polishing rate
during chemical mechanical polishing, and exhibits appropriate
mechanical strength (e.g., hardness).
[0062] It is preferable that the water-soluble particles have an
average particle size of 0.5 to 200 micrometers. The size of the
pores formed when the water-soluble particles are removed from the
surface of the polishing layer of the chemical mechanical polishing
pad is preferably 0.1 to 500 micrometers, and more preferably 0.5
to 200 micrometers. When the average particle size of the
water-soluble particles is within the above range, it is possible
to produce a chemical mechanical polishing pad that includes a
polishing layer that achieves a high polishing rate and exhibits
excellent mechanical strength.
1.1.2. Specific Gravity
[0063] The polishing layer included in the chemical mechanical
polishing pad according to one embodiment of the invention has a
specific gravity of 1.1 to 1.3, and preferably 1.15 to 1.27. When
the specific gravity of the polishing layer is within the above
range, the polishing target surface can be sufficiently planarized
since the polishing layer exhibits appropriate hardness. Moreover,
it is possible to suppress occurrence of polishing defects
(scratches) since the polishing layer exhibits moderate elastic
deformation (i.e., followability) along elevations and depressions
of the polishing target surface. If the specific gravity of the
polishing layer is less than the above range, the hardness of the
polishing layer may decrease to a large extent, and the polishing
target surface may not be sufficiently planarized. If the specific
gravity of the polishing layer exceeds the above range, the
hardness of the polishing layer may increase to a large extent, and
the number of polishing defects (scratches) may increase.
[0064] The upper limit of the specific gravity of the polishing
layer is set to 1.30 taking account of the balance between the
specific gravity of a polyurethane and the hardness of the
polishing layer. It is necessary to use a material having a high
specific gravity together with a urethane in order to produce a
polishing layer having a specific gravity of more than 1.30. For
example, a polishing layer having a specific gravity of more than
1.30 may be formed by mixing a urethane with a material having a
high specific gravity (e.g., silica or alumina) as a filler. In
this case, however, the resulting polishing layer exhibits high
hardness due to the filler, and the polishing target surface may be
scratched to a large extent. Therefore, it is impossible to achieve
the advantageous effects of the polishing layer used in connection
with the embodiments of the invention.
[0065] The specific gravity of the polishing layer may be measured
in accordance with JIS Z 8807. Specifically, a Le Chatelier
specific gravity bottle containing water is charged with a sample
having a known mass, and the volume of the sample is determined
from an increase in liquid level. The specific gravity of the
sample is calculated from the mass and the volume of the
sample.
[0066] It is preferable that the polishing layer included in the
chemical mechanical polishing pad according to one embodiment of
the invention be a non-foamed polishing layer in order to adjust
the specific gravity of the polishing layer within the above range.
Note that the term "non-foamed polishing layer" used herein refers
to a polishing layer that substantially does not include bubbles.
The specific gravity of a commercially available urethane pad that
includes a foamed polishing layer (e.g., "IC 1000" manufactured by
Rohm & Haas) is about 0.40 to about 0.90.
1.1.3. Thermal Conductivity
[0067] The polishing layer included in the chemical mechanical
polishing pad according to one embodiment of the invention has a
thermal conductivity of 0.2 W/mK or more, and preferably 0.3 W/mK
or more. When the polishing layer has a thermal conductivity of 0.2
W/mK or more, frictional heat that is produced when the polishing
target surface and the surface of the polishing pad rub against
each other can be promptly diffused in the polishing layer, and a
local increase in temperature of the surface of the polishing pad
can be reduced. Moreover, the durability of the polishing layer can
be improved by suppressing a situation in which frictional heat
that is produced during CMP performed over a long time is
accumulated in the polishing layer.
[0068] The thermal conductivity of the polishing layer is
preferably 0.2 W/mK or more from the viewpoint of the technical
idea of the invention. The upper limit of thermal conductivity of a
general-purpose engineering plastic (e.g., polyvinyl alcohol,
polyvinyl chloride, epoxy resin, polyurethane, polyacrylic resin,
and polyester resin) currently known in the art is 0.6 W/mK. Note
that a polymer composition having a higher thermal conductivity can
be obtained by mixing a thermally conductive filler or the like
into a general-purpose engineering plastic. It is considered that a
novel polyurethane having a higher thermal conductivity may be
developed in the future. Accordingly, the technical idea of the
invention is not limited to the above thermal conductivity upper
limit.
[0069] The thermal conductivity of the polishing layer is
calculated from the thermal diffusivity, specific heat, and
specific gravity. More specifically, a specimen is placed on a
sensor, and covered with a jig equipped with a microheater, and a
weight (50 g) is placed over the specimen. The thermal diffusivity
D is measured from amplitude attenuation and a phase delay that
occur when thermal waves generated from the surface of the
microheater diffuse in the thickness direction and reach the back
side of the specimen. The thermal conductivity (W/mK) is calculated
by the following expression (2) using the thermal diffusivity D,
the specific heat rho and the specific gravity Cp of the
specimen.
Thermal conductivity (W/mK)=D/(rho.times.Cp) (2)
[0070] It is preferable that the polishing layer included in the
chemical mechanical polishing pad according to one embodiment of
the invention be a non-foamed polishing layer in order to obtain a
thermal conductivity within the above range. It is preferable that
the polishing layer include a filler that exhibits high thermal
conductivity. For example, the polishing layer may include
water-soluble particles (see above) or the like as the filler. Note
that the thermal conductivity of the polishing layer of a
commercially available urethane pad that includes a foamed
polishing layer (e.g., "IC 1000" manufactured by Rohm & Haas)
is about 0.05 to about 0.10 W/mK.
[0071] When the chemical mechanical polishing pad according to one
embodiment of the invention includes a laminate that includes the
polishing layer and a support layer (described later), or includes
a laminate that includes the polishing layer, a support layer, and
an additional layer that is provided between the polishing layer
and the support layer, it is preferable that the laminate have a
thermal conductivity of 0.2 W/mK or more, and preferably 0.3 W/mK
or more. When the laminate has a thermal conductivity of 0.2 W/mK
or more, frictional heat that occurs when the polishing target
surface and the surface of the polishing pad rub against each other
can be efficiently diffused to a platen that holds the polishing
pad through the additional layer and/or the support layer.
[0072] The thermal conductivity of the laminate is calculated from
the thickness and the thermal conductivity of each layer. For
example, when the chemical mechanical polishing pad includes the
polishing layer (thickness: d1, thermal conductivity: lambda1), a
support layer (thickness: d3, thermal conductivity: lambda3), and
an additional layer (thickness: d2, thermal conductivity: lambda2)
that is provided between the polishing layer and the support layer,
the thermal conductivity is calculated by the following expression
(3). When the chemical mechanical polishing pad does not include
the additional layer, the thermal conductivity is calculated by the
expression (3) provided that the values d2 and d2/lambda2 are
0.
Thermal conductivity
(W/mK)=(d1+d2+d3)/((d1/lambda1)+(d2/lambda2)+(d3/lambda3)) (3)
[0073] Note that the thermal conductivity of a commercially
available urethane pad that includes a foamed polishing layer
(e.g., "IC 1000" manufactured by Rohm & Haas) is about 0.02 to
about 0.10 W/mK.
[0074] Note that it is preferable to provide a cooling mechanism
that controls temperature to a platen that holds the chemical
mechanical polishing pad. This makes it possible to efficiently
reduce an increase in temperature of the polishing layer, and
easily allow the entire chemical mechanical polishing pad to have a
constant temperature.
1.1.4. Residual Strain when Applying Tension
[0075] The residual strain of the polishing layer included in the
chemical mechanical polishing pad according to one embodiment of
the invention when applying tension to the polishing layer is
preferably 2 to 10%, and more preferably 2 to 9%.
[0076] Small pores and/or depressions are normally formed in the
surface of the polishing layer, and are gradually filled (clogged)
with polishing waste or pad waste, whereby a deterioration in
polishing performance occurs. In this case, the surface of the
polishing layer is ground by dressing using a diamond grinding
wheel (hereinafter may be referred to as "diamond conditioning") so
that a surface under the initial conditions is obtained. The
surface of the polishing layer may be roughened, or pad waste may
occur during diamond conditioning.
[0077] FIG. 1 is a schematic view illustrating the concept of the
residual strain of the polishing layer when applying tension to the
polishing layer. FIGS. 2A to 2E are enlarged views of an area I in
FIG. 1 that illustrate the concept of the residual strain of the
polishing layer when applying tension to the polishing layer. As
illustrated in FIG. 1, the surface of a polishing layer 10 is
ground during diamond conditioning by rotating a dresser 20 in the
direction indicated by the arrow. As illustrated in FIGS. 2A and
2B, part of the surface of the polishing layer 10 is pulled by the
dresser 20 when dressing the polishing layer 10. As illustrated in
FIG. 2C, part of the surface of the polishing layer 10 is removed
(cut) to produce pad waste 10a. As illustrated in FIG. 2D, an
elongated portion 10b of the polishing layer 10 shrinks so as to
return to the original state due to the elasticity of the polishing
layer. In this case, a roughened portion 10b' (see FIG. 2E) is
formed due to the residual strain of the polishing layer.
Therefore, the residual strain of the polishing layer when applying
tension to the polishing layer is an index that indicates the
degree of roughness of the surface of the polishing layer during
diamond conditioning.
[0078] When the residual strain of the polishing layer when
applying tension to the polishing layer is within the above range,
occurrence of pad waste and roughening of the surface of the
polishing layer during diamond conditioning are suppressed. It is
also possible to suppress deformation of the polishing layer due to
elevations and depressions of the polishing target surface (e.g.,
the surface of a wafer). This makes it possible to improve the
planarity of the polishing target surface while suppressing
occurrence of polishing defects. If the residual strain of the
polishing layer when applying tension to the polishing layer is
less than 2%, the amount of pad waste that occurs when subjecting
the surface of the polishing layer to diamond conditioning may
increase, and the number of polishing defects may increase due to
entrance of the pad waste in the polishing step. If the residual
strain of the polishing layer when applying tension to the
polishing layer exceeds 10%, the surface of the polishing layer may
be roughened to a large extent when subjecting the surface of the
polishing layer to diamond conditioning, and the polishing layer
may be deformed to a large extent along elevations and depressions
of the polishing target surface. As a result, the polishing target
surface may not be sufficiently planarized.
[0079] The residual strain of the polishing layer when applying
tension to the polishing layer may be measured in accordance with
JIS K 6270 (see below). A residual strain tester includes a
plurality of fixed clamps that hold one end of a specimen, a
plurality of reciprocating clamps that hold the other end of the
specimen, a driver device that reciprocates the reciprocating
clamps at a given frequency and a given amplitude, a counter that
displays the number of reciprocations of the reciprocating clamps,
and the like. Two dumbbell-shaped specimens are held by the clamps.
After reciprocating the reciprocating clamps 1.times.10.sup.3
times, the operation of the tester is stopped so that no stress is
applied to one of the specimens. When 1 minute has elapsed, the
bench mark distance of the specimen is measured. After
reciprocating the reciprocating clamps 100 times, the bench mark
distance of the other specimen is measured in the same manner as
described above. The test is normally performed at a frequency of 1
to 5 Hz. The residual strain (%) when applying tension to the
specimen is calculated by the following expression (4) using the
bench mark distance (I.sub.0) measured before the test and the
bench mark distance (I.sub.n) measured after the test in a state in
which tension is not applied to the specimen.
Residual strain (%) when applying
tension=((I.sub.n-I.sub.0)/I.sub.0).times.100 (4)
[0080] The temperature and the humidity during the measurement are
set in accordance with "6.1 Standard temperature in test room" and
"6.2 Standard humidity in test room" defined in JIS K 6250.
Specifically, the standard temperature in the test room is set to
23.degree. C. (allowance: +2.degree. C.). The standard humidity
(relative humidity) in the test room is set to 50% (allowance:
.+-.10%).
1.1.5. Volume Change Ratio
[0081] The volume change ratio of the polishing layer included in
the chemical mechanical polishing pad according to one embodiment
of the invention when immersing the polishing layer in water at
23.degree. C. for 24 hours is preferably 0.8 to 5%, and more
preferably 1 to 3%.
[0082] FIGS. 3A and 3B are schematic views illustrating the concept
of the volume change ratio of the polishing layer. The chemical
mechanical polishing pad is always exposed to the slurry during
polishing. As illustrated in FIG. 3A, a depression 30 is formed in
the polishing layer 10 to have given dimensions and a given shape.
As illustrated in FIG. 3B, the depression 30 may change in
dimensions, shape, degree of roughening, or the like when the
polishing layer 10 swells due to absorption of water. When the
volume change ratio of the polishing layer when immersing the
polishing layer in water is within the above range, the surface of
the polishing layer is moderately softened when the polishing layer
swells due to absorption of water, so that occurrence of scratches
can be suppressed. If the volume change ratio of the polishing
layer is less than the above range, the surface of the polishing
layer may not be sufficiently softened since the polishing layer
may swell to only a small extent due to absorption of water, and
occurrence of scratches may not be sufficiently suppressed. If the
volume change ratio of the polishing layer exceeds the above range,
the polishing layer may swell to a large extent due to absorption
of water, and the polishing target surface may not be sufficiently
planarized although occurrence of scratches may be suppressed. When
a depression pattern is formed in the polishing surface of the
polishing layer, the shape or the dimensions of the depression
pattern may change depending on the polishing time if the polishing
layer swells to a large extent due to absorption of water. As a
result, stable polishing properties may not be achieved. Therefore,
it is preferable to prevent a situation in which the polishing
layer swells to a large extent in order to prevent deformation of
the polishing surface.
[0083] The volume change ratio of the polishing layer may be
determined in accordance with JIS K 6258 (see below). A polishing
layer having a thickness of 2.8 mm is cut to obtain a specimen
having dimensions of 2.times.2 cm, and the specimen is immersed in
water at 23.degree. C. for 24 hours. The mass (M1) of the specimen
in air before immersion, the mass (M2) of the specimen in water
before immersion, the mass (M3) of the specimen in air after
immersion, and the mass (M4) of the specimen in water after
immersion are measured, and the volume change ratio is calculated
by the following expression (5),
Volume change ratio (%)=(((M3-M4)-(M1-M2))/(M1-M2)).times.100
(5)
1.1.6. Durometer D Hardness
[0084] The durometer D hardness of the polishing layer included in
the chemical mechanical polishing pad according to one embodiment
of the invention is preferably 50 to 80, more preferably 55 to 75,
and particularly preferably 60 to 70.
[0085] FIGS. 4A and 4B are schematic views illustrating the concept
of the durometer D hardness of the polishing layer. When a load is
applied to the polishing layer 10 from above (in the same manner as
in the polishing step) as illustrated in FIG. 4A, the polishing
layer 10 warps as illustrated in FIG. 4B. The durometer D hardness
is an index of the degree of macroscopic warping of the polishing
layer 10 when a load is applied to the polishing layer 10 in the
polishing step. This can be understood from the measurement method
described below. When the durometer D hardness of the polishing
layer is within the above range, the polishing target surface can
be sufficiently planarized, and occurrence of polishing defects
(scratches) can be suppressed since the polishing layer exhibits
moderate elastic deformation (i.e., followability) along elevations
and depressions of the polishing target surface. If the durometer D
hardness of the polishing layer is less than the above range, the
polishing target may not be sufficiently planarized. If the
durometer D hardness of the polishing layer exceeds the above
range, the number of polishing defects (scratches) may
increase.
[0086] The durometer D hardness of the polishing layer may be
measured in accordance with JIS K 6253 (see below). A specimen is
placed on a flat and rigid surface. A type D durometer is held so
that the pressure plate of the type D durometer is parallel to the
surface of the specimen, and the indenter is perpendicular to the
surface of the specimen. The pressure plate is then brought into
contact with the specimen without applying an impact to the
specimen. Note that the measurement point (at which the end of the
indenter comes in contact with the specimen) is apart from the edge
of the specimen by 12 mm or more. When 15 seconds has elapsed after
bringing the pressure plate into contact with the specimen, the
hardness of the specimen is measured. The hardness of the specimen
is measured five times at measurement points that are apart from
each other by 6 mm or more. The average value of the measured
values is taken as the durometer D hardness.
1.1.7. Surface Hardness in Wet State
[0087] The surface hardness of the polishing layer included in the
chemical mechanical polishing pad according to one embodiment of
the invention in the wet state is preferably 2 to 10 N/mm.sup.2,
more preferably 3 to 9 N/mm.sup.2, and particularly preferably 4 to
8 N/mm.sup.2. The surface hardness of the polishing layer in the
wet state is an index that indicates the surface hardness of the
polishing layer during CMP. FIGS. 5A and 5B are schematic views
illustrating the concept of the surface hardness of the polishing
layer. As illustrated in FIG. 5A, a minute probe 40 is pressed
against the surface of the polishing layer 10. As illustrated in
FIG. 5B, the polishing layer 10 is deformed (pushed out) by the
probe 40 in an area directly under the probe 40. The surface
hardness thus indicates the degree of deformation or warping of the
uppermost surface of the polishing layer. More specifically, while
data that indicates the macroscopic hardness of the entire
polishing layer is obtained by measuring the durometer D hardness
(i.e., hardness on millimeter scale) (see FIGS. 4A and 4B), data
that indicates the microscopic hardness of the uppermost surface of
the polishing layer is obtained by measuring the surface hardness
of the polishing layer in the wet state (see FIGS. 5A and 5B). The
polishing layer is depressed to a depth of 5 to 50 micrometers
during CMP. Therefore, it is preferable to determine the
flexibility of the uppermost surface of the polishing layer during
CMP based on the surface hardness of the polishing layer in the wet
state. When the surface hardness of the polishing layer in the wet
state is within the above range, the uppermost surface of the
polishing layer exhibits moderate flexibility, and occurrence of
polishing defects (scratches) can be suppressed. If the surface
hardness of the polishing layer in the wet state is less than the
above range, the polishing target surface may not be sufficiently
planarized. If the surface hardness of the polishing layer in the
wet state exceeds the above range, the number of polishing defects
(scratches) may increase. Note that the surface hardness of the
polishing layer in the wet state is indicated by the universal
hardness (HU) measured when pressing the polishing layer that has
been immersed in water at 23.degree. C. for 4 hours at 300 mN using
a nanoindenter ("HM2000" manufactured by FISCHER).
1.1.8. Shape of Polishing Layer and Depressions
[0088] The planar shape of the polishing layer is not particularly
limited. For example, the polishing layer may have a circular
planar shape. When the polishing layer has a circular planar shape,
the diameter of the polishing layer is preferably 150 to 1200 mm,
and more preferably 500 to 1000 mm. The thickness of the polishing
layer is preferably 0.5 to 5.0 mm, more preferably 1.0 to 4.0 mm,
and particularly preferably 1.5 to 3.5 mm.
[0089] A plurality of depressions may be formed in the polishing
surface of the polishing layer. The depressions serve as a path
that retains the slurry supplied during CMP, uniformly distributes
the slurry over the polishing surface, temporarily stores waste
(e.g., polishing waste, pad waste, or spent slurry), and discharges
the waste to the outside.
[0090] The depth of the depressions is preferably 0.1 mm or more,
more preferably 0.1 to 2.5 mm, and particularly preferably 0.2 to
2.0 mm. The width of the depressions is preferably 0.1 mm or more,
more preferably 0.1 to 5.0 mm, and particularly preferably 0.2 to
3.0 mm. The interval between the adjacent depressions is preferably
0.05 mm or more, more preferably 0.05 to 100 mm, and particularly
preferably 0.1 to 10 mm. The pitch (i.e., the sum of the width of
the depression and the distance between adjacent depressions) is
preferably 0.15 mm or more, more preferably 0.15 to 105 mm, and
particularly preferably 0.6 to 13 mm. The depressions may be formed
at constant intervals within the above range. It is possible to
easily produce a chemical mechanical polishing pad that achieves an
excellent effect of suppressing occurrence of scratches on the
polishing target surface and has a long lifetime by forming the
depressions as described above.
[0091] The above preferable ranges may be arbitrarily combined. For
example, it is preferable that the depressions have a depth of 0.1
mm or more, a width of 0.1 mm or more, and an interval of 0.05 mm
or more. It is more preferable that the depressions have a depth of
0.1 to 2.5 mm, a width of 0.1 to 5.0 mm, and an interval of 0.05 to
100 mm. It is particularly preferable that the depressions have a
depth of 0.2 to 2.0 mm, a width of 0.2 to 3.0 mm, and an interval
of 0.1 to 10 mm.
[0092] The depressions may be formed using a multi-blade tool
having the shape disclosed in JP-A-2006-167811, JP-A-2001-18164,
JP-A-2008-183657, or the like. The cutting blades of the tool may
be provided with a coating layer formed using diamond, or at least
one metal element selected from Group 4, 5, and 6 metals (e.g., Ti,
Cr, Zr, and V) and at least one non-metal element selected from
nitrogen, carbon, and oxygen. The cutting blades may be provided
with a plurality of coating layers that differ in material. The
thickness of the coating layer is preferably 0.1 to 5 micrometers,
and more preferably 1.5 to 4 micrometers. The coating layer may be
formed by an appropriate known technique (e.g., technique using an
arc ion plating apparatus) depending on the material of the tool,
the material of the coating layer, and the like.
1.1.9. Production Method
[0093] The polishing layer included in the chemical mechanical
polishing pad according to one embodiment of the invention is
obtained by molding the composition that includes the polyurethane.
The composition may be kneaded using a known mixer or the like.
Examples of the mixer include a roller, a kneader, a Banbury mixer,
an extruder (single-screw extruder or multi-screw extruder), and
the like. For example, the composition that has been plasticized at
120 to 230.degree. C. may be molded by press molding, extrusion
molding, or injection molding, and plasticized/sheeted to obtain a
polishing layer. The specific gravity and the hardness of the
polishing layer may be controlled by appropriately adjusting the
molding conditions.
[0094] Depressions may be formed in the polishing surface of the
polishing layer by cutting. The depressions may be formed when
forming the polishing layer by molding the composition using a mold
provided with a depression pattern.
1.2. Support Layer
[0095] The chemical mechanical polishing pad according to one
embodiment of the invention may include only the polishing layer,
or may further include a support layer that is provided on the
surface of the polishing layer opposite to the polishing
surface.
[0096] The support layer included in the chemical mechanical
polishing pad is used to support the polishing layer on a platen of
a polishing system. The support layer may be an adhesive layer, or
may be a cushion layer that has an adhesive layer on each side. The
adhesive layer may be a pressure-sensitive adhesive sheet, for
example.
[0097] The thickness of the pressure-sensitive adhesive sheet is
preferably 50 to 250 micrometers. When the pressure-sensitive
adhesive sheet has a thickness of 50 micrometers or more, it is
possible to sufficiently reduce the pressure applied to the
polishing surface of the polishing layer. When the
pressure-sensitive adhesive sheet has a thickness of 250
micrometers or less, it is possible to obtain a chemical mechanical
polishing pad having a uniform thickness so that the polishing
performance is not affected by elevations or depressions of the
polishing target surface.
[0098] A material for forming the pressure-sensitive adhesive sheet
is not particularly limited as long as the polishing layer can be
secured on the platen of the polishing system. The material for
forming the pressure-sensitive adhesive sheet is preferably an
acrylic material or a rubber material that has a modulus of
elasticity lower than that of the polishing layer.
[0099] The adhesive strength of the pressure-sensitive adhesive
sheet is not particularly limited as long as the chemical
mechanical polishing pad can be secured on the platen of the
polishing system. The adhesive strength of the pressure-sensitive
adhesive sheet measured in accordance with JIS Z 0237 is preferably
3 N/25 mm or more, more preferably 4 N/25 mm or more, and
particularly preferably 10 N/25 mm or more.
[0100] A material for forming the cushion layer is not particularly
limited as long as the material has a hardness lower than that of
the polishing layer. The cushion layer may be formed of a porous
body (foam) or a non-porous body. Examples of the cushion layer
include a layer obtained by molding a polyurethane foam or the
like. The thickness of the cushion layer is preferably 0.1 to 5.0
mm, and more preferably 0.5 to 2.0 mm.
[0101] It is preferable that the support layer have a thermal
conductivity of 0.2 W/mK or more, and more preferably 0.3 W/mK or
more. When the support layer has a thermal conductivity of 0.2 W/mK
or more, frictional heat that is produced when the polishing target
surface and the surface of the polishing pad rub against each other
can be efficiently diffused to the platen through the support
layer. As a result, frictional heat that has been produced in the
polishing layer can be efficiently removed, so that an increase in
temperature of the polishing layer can be reduced, and stable
polishing performance can be maintained even when performing CMP
for a long time.
[0102] The thermal conductivity of the support layer is measured in
the same manner as in the case of measuring the thermal
conductivity of the polishing layer. Note that the thermal
conductivity of the support layer of a commercially available
urethane pad that includes a foamed polishing layer (e.g., "IC
1000" manufactured by Rohm & Haas) is about 0.01 to about 0.10
W/mK.
[0103] The compressibility of the support layer is preferably 5% or
more, and more preferably 6% or more. When polishing the polishing
target (e.g., silicon wafer), pressure applied to the polishing
target per unit area differs between the center area and the
peripheral area of the polishing target (i.e., pressure applied to
the peripheral area of the polishing target tends to increase). In
this case, since the polishing rate differs to a large extent
between the center area and the peripheral area of the polishing
target, it is difficult to polish the polishing target surface at a
uniform polishing rate. When the compressibility of the support
layer is within the above range, the support layer is effectively
deformed so that an increase in pressure applied to the peripheral
area of the polishing target can be reduced. Therefore, it is
possible to polish the entire polishing target surface at a uniform
polishing rate. If the compressibility of the polishing layer is
within the above range, the polishing rate may decrease to a large
extent, and the planarity of the polishing target surface may be
impaired due to a decrease in pressure applied to the polishing
target. Accordingly, it is desirable that the compressibility of
the support layer be within the above range in order to achieve the
object of the invention.
2. CHEMICAL MECHANICAL POLISHING METHOD
[0104] A chemical mechanical polishing method according to one
embodiment of the invention includes chemically and mechanically
polishing a polishing target using the chemical mechanical
polishing pad according to one embodiment of the invention. The
chemical mechanical polishing pad includes the polishing layer that
is formed using the composition that includes the polyurethane, and
has a specific gravity and a thermal conductivity within the
specific ranges. Therefore, the chemical mechanical polishing
method according to one embodiment of the invention can improve the
planarity of the polishing target surface, suppress occurrence of
polishing defects (scratches), and maintain stable polishing
performance during CMP performed for a long time.
[0105] The chemical mechanical polishing method according to one
embodiment of the invention may be implemented using a commercially
available chemical mechanical polishing system. Examples of a
commercially available chemical mechanical polishing system include
EPO-112 and EPO-222 (manufactured by Ebara Corporation); LGP-510
and LGP-552 (manufactured by Lapmaster SFT); Mirra and Reflexion LK
(manufactured by Applied Materials); and the like.
[0106] An optimum slurry may be appropriately selected depending on
the polishing target (e.g., copper film, insulating film, or
low-dielectric-constant insulating film).
3. EXAMPLES
[0107] The invention is further described below by way of examples.
Note that the invention is not limited to the following
examples.
3.1. Production of Chemical Mechanical Polishing Pad
3.1.1. Example 1
[0108] 100 parts by mass of a non-alicyclic thermoplastic
polyurethane ("Elastollan 1174D" manufactured by BASF, hardness:
70D) and 29 parts by mass of beta-cyclodextrin ("Dexy Pearl
beta-100" manufactured by Ensuiko Sugar Refining Co., Ltd., average
particle size: 20 micrometers) (water-soluble particles) were
kneaded using an extruder heated at 200.degree. C. to prepare a
thermoplastic polyurethane composition. The thermoplastic
polyurethane composition was compression-molded at 180.degree. C.
in a press mold to obtain a cylindrical molded product (diameter:
845 mm, thickness: 3.2 mm). The surface of the molded product was
ground using sandpaper to adjust the thickness. A plurality of
concentric depressions (width: 0.5 mm, depth: 1.0 mm, pitch: 1.5
mm) were formed in the surface of the molded product using a
cutting machine (manufactured by Kato Machine Corporate), and the
periphery of the molded product was cut to obtain a polishing layer
(diameter: 600 mm, thickness: 2.5 mm). The surface of the polishing
layer in which the depressions were not formed was laminated with a
double-sided tape "#422JA" (manufactured by 3M) to produce a
chemical mechanical polishing pad.
3.1.2. Example 2
[0109] A polishing layer was obtained in the same manner a in
Example 1. The surface of the polishing layer in which the
depressions were not formed was laminated with a double-sided tape
"#550PS5" (manufactured by Sekisui Chemical Co., Ltd.). A
sheet-like urethane ("Nippalay EXY" manufactured by NHK Spring Co.,
Ltd.) (support layer) was bonded to the tape, and laminated with a
double-sided tape "#442JA" (manufactured by 3M) to produce a
chemical mechanical polishing pad.
3.1.3. Examples 3 and 4
[0110] A chemical mechanical polishing pad was produced in the same
manner as in Example 1, except that the type and the amount of each
component of the composition were changed as shown in Table 1.
3.1.4. Example 5
[0111] A polishing layer was obtained in the same manner as in
Example 1. The surface of the polishing layer in which the
depressions were not formed was laminated with a double-sided tape
"#550PS5" (manufactured by Sekisui Chemical Co., Ltd.). A support
layer having the compressibility and the thermal conductivity shown
in Table 1 was bonded to the tape, and laminated with a
double-sided tape "#442JA" (manufactured by 3M) to produce a
chemical mechanical polishing pad. Note that the support layer
having the compressibility and the thermal conductivity shown in
Table 1 was produced by adding an appropriate amount of spheroidal
graphite ("WF-15C" manufactured by Chuetsu Graphite Works Co.,
Ltd.) to a hydrogenated ethylene-butylene block copolymer
("DYNARON" manufactured by JSR Corporation) so that the
compressibility and the thermal conductivity shown in Table 1 were
obtained, kneading the mixture using a kneader, and forming the
mixture into a sheet.
3.1.5. Example 6
[0112] A chemical mechanical polishing pad was produced in the same
manner as in Example 5. Note that the support layer having the
compressibility and the thermal conductivity shown in Table 1 was
produced by adding an appropriate amount of spheroidal alumina
("DAM-70" manufactured by Denki Kagaku Kogyo Kabushiki Kaisha) to a
hydrogenated ethylene-butylene block copolymer ("DYNARON"
manufactured by JSR Corporation) so that the compressibility and
the thermal conductivity shown in Table 1 were obtained, kneading
the mixture using a kneader, and forming the mixture into a
sheet.
3.1.6. Example 7
[0113] A chemical mechanical polishing pad was produced in the same
manner as in Example 2, except that a flame-retardant polycarbonate
insulating sheet "SunMorfee" (manufactured by SunDelta Corporation)
was used as the support layer.
3.1.7. Comparative Example 1
[0114] A commercially available chemical mechanical polishing pad
("IC 1000" manufactured by Rohm & Haas, wherein the polishing
layer is formed of a thermally crosslinkable polyurethane) was
used. The specific gravity and the thermal conductivity of the
polishing layer measured by the following methods were 0.81 and
0.05 W/mK, respectively.
3.1.8. Comparative Example 2
[0115] 100 parts by mass of 1,2-polybutadiene ("RB830" manufactured
by JSR Corporation, hardness: 47D) and 38 parts by mass of
beta-cyclodextrin ("Dexy Pearl beta-100" manufactured by Ensuiko
Sugar Refining Co., Ltd, average particle size: 20 micrometers)
(water-soluble particles) were mixed to prepare a composition.
After the addition of 1 part by mass of an organic peroxide
("Percumyl D-40" manufactured by NOF Corporation) to 100 parts by
mass of the composition, the mixture was kneaded. A polishing layer
formed of a water-soluble particle-containing thermally crosslinked
polybutadiene resin was obtained in the same manner as in Example
1. The surface of the polishing layer in which the depressions were
not formed was laminated with a double-sided tape "#550PS5"
(manufactured by Sekisui Chemical Co., Ltd.). A high-density
sheet-like hydrogenated ethylene-butylene block copolymer
("DAYNARON" manufactured by JSR Corporation) (support layer) was
bonded to the tape, and laminated with a double-sided tape "#442JA"
(manufactured by 3M) to produce a chemical mechanical polishing
pad.
[0116] The abbreviation of each component shown in Table 1 has the
following meaning.
"PU1-1": non-alicyclic thermoplastic polyurethane ("Elastollan
1174D" manufactured by BASF, hardness: 70D) "PU2-1": alicyclic
thermoplastic polyurethane ("Elastollan NY 1197A" manufactured by
BASF, hardness: 61D) "beta-CD": beta-cyclodextrin ("Dexy Pearl
beta-100" manufactured by Ensuiko Sugar Refining Co., Ltd., average
particle size: 20 micrometers) "Thermally crosslinked polybutadiene
resin": 1,2-polybutadiene ("RB830"manufactured by JSR Corporation,
hardness: 47D) "Organic peroxide": dicumyl peroxide ("Percumyl
D-40" manufactured by NOF Corporation, crosslinking agent)
3.2. Measurement of Properties of Polishing Layer
3.2.1. Specific gravity
[0117] The specific gravity of the polishing layer produced in the
section "3.1. Production of chemical mechanical polishing pad" and
the polishing layer of the pad "IC 1000" was measured. The specific
gravity was measured in accordance with JIS Z 8807. The results are
shown in Table 1.
3.2.2. Thermal Conductivity
[0118] The thermal conductivity of the polishing layer produced in
the section "3.1. Production of chemical mechanical polishing pad"
and the polishing layer of the pad "IC 1000" was measured. The
thermal conductivity was measured as described below. A specimen
was placed on a sensor, and covered with a jig equipped with a
microheater, and a weight (50 g) was placed over the specimen. The
thermal diffusivity D was measured from an amplitude attenuation
and a phase delay that occurred when thermal waves generated from
the surface of the microheater diffused in the thickness direction
and reached the back side of the specimen. The thermal conductivity
(W/mK) was calculated by the following expression (2) using the
thermal diffusivity D, the specific heat rho and the specific
gravity Cp of the specimen. The results are shown in Table 1.
Thermal conductivity (W/mK)=D/(rho.times.Cp) (2)
3.2.3. Residual Strain when Applying Tension
[0119] A specimen was prepared from the polishing layer produced in
the section "3.1. Production of chemical mechanical polishing pad"
and the polishing layer of the pad "IC 1000" in an area in which
the depressions were not formed, and the residual strain when
applying tension was measured. The residual strain when applying
tension was measured in accordance with JIS K 6270. The temperature
and the humidity (relative humidity) during the measurement were
respectively 23.degree. C. and 50%. The results are shown in Table
1.
3.2.4. Volume Change Ratio
[0120] The volume change ratio of the polishing layer produced in
the section "3.1. Production of chemical mechanical polishing pad"
and the polishing layer of the pad "IC 1000" was measured. The
volume change ratio of the polishing layer was measured in
accordance with JIS K 6258 (see below). The polishing layer having
a thickness of 2.8 mm was cut into a square measurement specimen
(2.times.2 cm). The measurement specimen was immersed in water at
23.degree. C. for 24 hours. The mass (M1) of the measurement
specimen in air before immersion, the mass (M2) of the measurement
specimen in water before immersion, the mass (M3) of the
measurement specimen in air after immersion, and the mass (M4) of
the measurement specimen in water after immersion were measured
using an electronic balance ("JP-300" manufactured by Cho Balance
Co., Ltd.), and the volume change ratio was calculated by the
following expression (5). The results are shown in Table 1.
Volume change ratio (%)=(((M3-M4)-(M1-M2))/(M1-M2)).times.100
(5)
3.2.5. Durometer D Hardness
[0121] The durometer D hardness of the polishing layer produced in
the section "3.1. Production of chemical mechanical polishing pad"
and the polishing layer of the pad "IC 1000" was measured. The
durometer D hardness of the polishing layer was measured in
accordance with JIS K 6253. The results are shown in Table 1.
3.2.6. Surface Hardness in Wet State
[0122] The surface hardness of the polishing layer produced in the
section "3.1. Production of chemical mechanical polishing pad" and
the polishing layer of the pad "IC 1000" in the wet state was
measured. The universal hardness (HU) measured when pressing a
nanoindenter ("HM2000" manufactured by FISCHER) against the
polishing layer (that had been immersed in water at 23.degree. C.
for 4 hours) at 300 mN was taken as the surface hardness of the
polishing layer in the wet state. The results are shown in Table
1.
3.3. Measurement of Properties of Support Layer
3.3.1. Compressibility
[0123] The support layer used in the section "3.1. Production of
chemical mechanical polishing pad" and the support layer removed
from the pad "IC 1000" were cut into a square small piece
(2.times.2 cm). The small piece was placed on the probe of a
measurement system "Compressive Elasticity Tester Model. SE-15"
(manufactured by Intec Co., Ltd.). A load of 10 gf or 600 gf was
applied to the small piece, and the small piece was allowed to
stand for 1 minute while applying a constant load. The thickness of
the small piece was then measured, and taken as a temporary
thickness of the small piece. The thickness in a blank state (i.e.,
a state in which the small piece was not placed on the probe) was
also measured. The compressibility was calculated by the following
expression (6) using the measurement results.
|Temporary thickness of small piece at 10 gf-thickness in blank
state at 10 gf|=thickness of support layer at 10 gf
|Temporary thickness of small piece at 600 gf-thickness in blank
state at 600 gf|=thickness of support layer at 600 gf
(Thickness of support layer at 10 gf-thickness of support layer at
600 gf)/thickness of support layer at 10
gf.times.100=compressibility (%) (6)
3.4. Evaluation of Chemical Mechanical Polishing
[0124] The chemical mechanical polishing pad produced in the
section "3.1. Production of chemical mechanical polishing pad" was
installed in a chemical mechanical polishing system ("EPO-112"
manufactured by Ebara Corporation), and dressed for 30 minutes
using a dresser ("#325-63R" manufactured by A.L.M.T. Corp.) at a
table rotational speed of 20 rpm, a dressing rotational speed of 19
rpm, and a dressing load of 5.1 kgf. The polishing target was
chemically mechanically polished using the dressed chemical
mechanical polishing pad under the following conditions, and the
polishing performance was evaluated as described below.
Head rotational speed: 60 rpm Head load: 3 psi (20.6 kPa) Table
rotational speed: 61 rpm Slurry supply rate: 300 cm.sup.3/min
Slurry: CMS8401/CMS8452 (manufactured by JSR Corporation)
3.4.1. Evaluation of Flatness
[0125] A polishing target (test substrate) was prepared by
depositing a PETEOS film (thickness: 5000 angstroms) on a silicon
substrate, forming a mask pattern ("SEMATECH 854"), and
sequentially depositing a tantalum nitride film (thickness: 250
angstroms), a copper seed film (thickness: 1000 angstroms), and a
copper film (thickness: 10,000 angstroms) over the mask
pattern.
[0126] The polishing target was chemically and mechanically
polished for 1 minute under the conditions described in the section
"3.4. Evaluation of chemical mechanical polishing". The thickness
of the polishing target was measured before and after chemical
mechanical polishing using an electric conduction-type thickness
measurement system ("OmniMap RS75" manufactured by KLA-Tencor), and
the polishing rate was calculated from the thickness of the
polishing target before chemical mechanical polishing, the
thickness of the polishing target after chemical mechanical
polishing, and the polishing time. An end point detection time at
which Cu had been completely removed (i.e., Cu clear) was
calculated from the time from the start of polishing to the end
point detected based on a change in table torque current. The
polishing target (patterned wafer) was polished for a time 1.2
times the end point detection time, and the amount of dishing of a
copper interconnect (width: 100 micrometers) was measured (in an
area in which a pattern in which a copper interconnect area (width:
100 micrometers) and an insulating area (width: 100 micrometers)
were alternately provided, was continuously formed to a length of
3.0 mm in the direction perpendicular to the longitudinal
direction) using a precision step meter ("HRP-240" manufactured by
KLA-Tencor Corporation). The planarity of the polishing target
surface was evaluated based on the amount of dishing. The results
are shown in Table 1. The amount of dishing is preferably less than
400 angstroms, more preferably less than 300 angstroms, and
particularly preferably less than 200 angstroms.
3.4.2. Evaluation of Scratches
[0127] The number of scratches that occurred on the polishing
target surface of the polishing target (patterned wafer) due to
polishing was counted using a wafer defect inspection system ("KLA
2351" manufactured by KLA-Tencor Corporation). The results are
shown in Table 1. The number of scratches is preferably less than
50, more preferably less than 30, and particularly preferably less
than 20.
3.4.3. Evaluation of Polishing Rate
[0128] A polishing target (8-inch wafer on which a PETEOS film
(thickness: 1000 nm) was formed) was chemically and mechanically
polished under the conditions described in the section "3.4.
Evaluation of chemical mechanical polishing". Note that the PETEOS
film is a silicon oxide film formed by plasma-enhanced chemical
vapor deposition using tetraethylorthosilicate (TEOS) as a raw
material.
[0129] The thickness of the PETEOS film of the polishing target was
measured (at 33 points situated at equal intervals in the
diametrical direction excluding the range of 5 mm from each end)
before and after chemical mechanical polishing using an optical
interference-type thickness meter ("Nano Spec 6100" manufactured by
Nanometrics Japan Ltd.). The polishing rate was calculated by the
following expressions (7) and (8) using the measurement
results.
Amount of polishing (nm)=thickness (nm) before polishing-thickness
(nm) after polishing (7)
Polishing rate (nm/min)=average amount of polishing (nm) at 33
points/polishing time (min) (8)
[0130] The polishing rate evaluation results are shown in Table 1.
The polishing performance was evaluated as acceptable when the
polishing rate was 200 nm/min or more, and evaluated as
unacceptable when the polishing rate was less than 200 nm/min.
3.4.4. Evaluation of Durability
[0131] The polishing rate change ratio when continuously polishing
the wafer based on the method described in the section "3.4.3.
Evaluation of polishing rate" was calculated by the following
expression (9) to evaluate the durability of the polishing layer.
More specifically, the dresser and the pad were set to a frictional
state for 10 hours by dressing in order to reproduce a state in
which the wafer is continuously polished, and the change ratio was
calculated by the expression (9) using the polishing rate before
and after dressing. The durability was evaluated as "Acceptable"
when the polishing rate change ratio was less than 5%, evaluated as
"Fair" when the polishing rate change ratio was 5% or more and less
than 10%, and evaluated as "Unacceptable" when the polishing rate
change ratio was 10% or more (see Table 1).
Polishing rate change ratio (%)=((polishing rate after 10 hours of
dressing-initial polishing rate)/initial polishing rate).times.100
(9)
3.4.5. Evaluation of Polishing Rate Change Ratio in Edge Area
[0132] A polishing target (8-inch wafer on which a PETEOS film
(thickness: 1000 nm) was formed) was chemically and mechanically
polished under the conditions described in the section "3.4.
Evaluation of chemical mechanical polishing". The thickness of the
PETEOS film of the polishing target was measured (at 0 mm, 4 mm, 8
mm, and 98 mm from the center of the wafer in the diametrical
direction) before and after chemical mechanical polishing using an
optical interference-type thickness meter ("Nano Spec 6100"
manufactured by Nanometrics Japan Ltd.). The polishing rate change
ratio in the edge area RR was calculated by the following
expressions using the measurement results.
Amount of polishing (nm)=thickness (nm) before polishing-thickness
(nm) after polishing
Amount of polishing (nm) in center area=average amount of polishing
(nm) at 0 mm, 4 mm, and 8 mm from center
Polishing rate (nm/min) in center area=amount of polishing (nm) in
center area/polishing time (min)
Amount of polishing (nm) in edge area=average amount of polishing
(nm) at 98 mm from center
Polishing rate (nm/min) in edge area=amount of polishing (nm) in
edge area/polishing time (min)
Polishing rate change ratio in edge area=|(polishing rate in edge
area-polishing rate in center area)/polishing rate in center
area|
[0133] It is preferable that the polishing rate change ratio in the
edge area be as small as possible. It is determined that the
polishing rate change ratio is practical when the polishing rate
change ratio is 30% or less. The evaluation results for the
polishing rate change ratio in the edge area are shown in Table
1.
TABLE-US-00001 TABLE 1 Compar- Compar- Exam- Exam- Exam- Exam-
Exam- Exam- Exam- ative ative ple 1 ple 2 ple 3 ple 4 ple 5 ple 6
ple 7 Example 1 Example 2 Composi- Thermo- PU1-1 100 100 70 50 100
100 100 IC1000 tion plastic (parts by mass) (commercially poly-
PU2-1 30 50 available urethane (parts by mass) pad) Other Thermally
100 crosslinked polybutadiene resin (parts by mass) beta-CD 29 29
29 29 29 29 38 (parts by mass) Organic peroxide 1.38 (parts by
mass) Properties Specific gravity 1.23 1.23 1.21 1.13 1.23 1.23
1.23 0.81 1.03 of polishing Thermal conductivity 0.27 0.27 0.32
0.20 0.27 0.27 0.27 0.10 0.24 layer (W/m k) Residual strain (%)
when 2.6 2.6 3.8 13.7 2.6 2.6 2.6 8.0 7.0 applying tension Volume
change ratio (%) 1.4 1.4 0.7 0.8 1.4 1.4 1.4 0.2 0.1 Durometer D
hardness 79D 79D 72D 64D 79D 79D 79D 63D 67D Surface hardness
(N/mm.sup.2) 6.7 6.5 4.4 4.0 6.7 6.7 6.7 14.5 8.9 Properties
Compressibility (%) -- 3.5 -- -- 13.0 6.5 3.0 12.0 2.0 of support
Thermal conductivity -- 0.08 -- -- 0.55 0.80 1.45 0.03 0.18 layer
(W/m k) Properties Thermal conductivity 0.27 0.12 0.32 0.24 0.34
0.37 0.34 0.05 0.47 of laminate (W/m k) Chemical Number of
scratches 45 49 33 12 48 47 46 125 130 mechanical Amount of dishing
(angstroms) 220 231 145 380 225 228 215 310 350 polishing Polishing
rate (angstroms/min) 610 810 591 700 710 600 650 730 450 evaluation
Durability Accept- Fair Accept- Accept- Accept- Accept- Accept-
Unaccept- Unaccept- results able able able able able able able able
Polishing rate change ratio 30 15 28 30 9 12 25 28 25 (%) in edge
area
3.5. Chemical Mechanical Polishing Pad Evaluation Results
[0134] As shown in Table 1, since the polishing layer of the
chemical mechanical polishing pads of Examples 1 to 7 had a thermal
conductivity of 0.2 W/mK or more, frictional heat that occurred
when the polishing target surface and the polishing pad rubbed
against each other could be reduced. It is considered that the
polishing layer of the chemical mechanical polishing pads of
Examples 1 to 7 showed excellent durability due to the above
effect. The chemical mechanical polishing pads of Examples 1 to 7
showed excellent results for planarity and scratches.
[0135] In contrast, the chemical mechanical polishing pads of
Comparative Examples 1 and 2 showed poor results for one or more
polishing performance items.
[0136] The polishing layer of the chemical mechanical polishing pad
of Comparative Example 1 was formed of the thermally crosslinked
polyurethane having a foamed structure, and had a thermal
conductivity of 0.10 W/mK. In this case, frictional heat tends to
be accumulated in the polishing layer. As a result, the polishing
layer of the chemical mechanical polishing pad of Comparative
Example 1 exhibited poor durability. The chemical mechanical
polishing pad of Comparative Example 1 was a laminate of the
polishing layer and the support layer. Since the laminate had a
thermal conductivity of 0.05 W/mK, it was difficult to diffuse
frictional heat.
[0137] The polishing layer of the chemical mechanical polishing pad
of Comparative Example 2 was formed of polybutadiene, and had a
sufficiently high thermal conductivity of 0.24 W/mK. However, since
the surface of the polishing layer had poor hydrophilicity, and
transfer of heat to the slurry on the surface of the polishing
layer was insufficient, the polishing layer exhibited poor
durability. The chemical mechanical polishing pad also exhibited
poor scratch resistance.
[0138] As is clear from the results obtained in the examples and
the comparative examples, the chemical mechanical polishing pad
according to the embodiments of invention achieved excellent
flatness and exhibited excellent scratch resistance and excellent
durability as a result of specifying the balance between the
specific gravity and the thermal conductivity of the polishing
layer formed of a polyurethane.
[0139] The invention is not limited to the above embodiments.
Various modifications and variations may be made of the above
embodiments. For example, the invention includes various other
configurations substantially the same as the configurations
described in connection with the above embodiments (e.g., a
configuration having the same function, method, and results, or a
configuration having the same objective and results). The invention
also includes a configuration in which an unsubstantial part
(element) described in connection with the above embodiments is
replaced with another part (element). The invention also includes a
configuration having the same effects as those of the
configurations described in connection with the above embodiments,
or a configuration capable of achieving the same objective as that
of the configurations described in connection with the above
embodiments. The invention further includes a configuration in
which a known technique is added to the configurations described in
connection with the above embodiments.
REFERENCE SIGNS LIST
[0140] 10: polishing layer, 10a: pad waste, 10b: elongated portion,
10b': roughened portion, 20: dresser, 30: depression, 40: probe
* * * * *