U.S. patent application number 13/518230 was filed with the patent office on 2012-12-20 for pad for chemical mechanical polishing and method of chemical mechanical polishing using same.
This patent application is currently assigned to JSR Corporation. Invention is credited to Satoshi Kamo, Ayako Maekawa, Naoki Nishiguchi, Keiichi Satou, Hirotaka Shida, Hiroyuki Tano, Shinji Tonsho, Katsutaka Yokoi.
Application Number | 20120322348 13/518230 |
Document ID | / |
Family ID | 44195529 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120322348 |
Kind Code |
A1 |
Yokoi; Katsutaka ; et
al. |
December 20, 2012 |
PAD FOR CHEMICAL MECHANICAL POLISHING AND METHOD OF CHEMICAL
MECHANICAL POLISHING USING SAME
Abstract
A chemical mechanical polishing pad includes a polishing layer
formed using a composition that includes a thermoplastic
polyurethane, the polishing layer having a specific gravity of 1.15
to 1.30, and a durometer D hardness of 50 to 80.
Inventors: |
Yokoi; Katsutaka;
(Yokkaichi, JP) ; Maekawa; Ayako; (Yokkaichi,
JP) ; Shida; Hirotaka; (Yokkaichi, JP) ; Kamo;
Satoshi; (Yokkaichi, JP) ; Tonsho; Shinji;
(Taito-ku, JP) ; Satou; Keiichi; (Yokkaichi,
JP) ; Nishiguchi; Naoki; (Yokkaichi, JP) ;
Tano; Hiroyuki; (Yokkaichi, JP) |
Assignee: |
JSR Corporation
Tokyo
JP
|
Family ID: |
44195529 |
Appl. No.: |
13/518230 |
Filed: |
December 14, 2010 |
PCT Filed: |
December 14, 2010 |
PCT NO: |
PCT/JP10/72430 |
371 Date: |
August 30, 2012 |
Current U.S.
Class: |
451/54 ;
51/298 |
Current CPC
Class: |
C08G 18/4804 20130101;
B24B 37/24 20130101; C08G 18/4854 20130101; B24B 37/042 20130101;
C08L 75/04 20130101; C08L 2205/025 20130101; C08L 2205/025
20130101; C08L 75/04 20130101; C08L 75/04 20130101; C08L 2205/03
20130101; C08L 75/04 20130101; C08L 71/00 20130101; C08L 75/04
20130101; C08L 71/00 20130101; C08L 2205/03 20130101; C08G 18/4833
20130101; C08G 18/7664 20130101 |
Class at
Publication: |
451/54 ;
51/298 |
International
Class: |
B24B 37/24 20120101
B24B037/24; B24B 1/00 20060101 B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2009 |
JP |
2009-290213 |
Dec 24, 2009 |
JP |
2009-291613 |
Jul 28, 2010 |
JP |
2010-169318 |
Jul 28, 2010 |
JP |
2010-169319 |
Claims
1. A chemical mechanical polishing pad, comprising: a polishing
layer comprising a composition that comprises a thermoplastic
polyurethane, wherein a specific gravity of the polishing layer is
from 1.15 to 1.30, and a durometer D hardness of the polishing
layer is from 50 to 80.
2. The chemical mechanical polishing pad of claim 1, wherein the
polishing layer has a residual strain of from 2 to 10% when
applying tension to the polishing layer.
3. The chemical mechanical polishing pad of claim 1, wherein the
polishing layer has a volume change rate of from 0.8 to 5.0% when
immersed in water at 23.degree. C. for 24 hours.
4. The chemical mechanical polishing pad of claim 1, wherein the
polishing layer has a surface hardness of from 2 to 10 N/mm.sup.2
after being immersed in water at 23.degree. C. for 4 hours.
5. The chemical mechanical polishing pad of claim 1, wherein the
thermoplastic polyurethane comprises a repeating unit derived from
an alicyclic isocyanate, an aromatic isocyanate, or any combination
thereof.
6. The chemical mechanical polishing pad of claim 1, wherein the
composition further comprises water-soluble particles.
7. A chemical mechanical polishing method, comprising: chemically
and mechanically polishing a polishing target with the chemical
mechanical polishing pad of claim 1.
8. The chemical mechanical polishing pad of claim 5, wherein the
thermoplastic polyurethane comprises a repeating unit derived from
isophorone diisocyanate (IPDI), norbornene diisocyanate,
hydrogenated 4,4'-diphenylmethane diisocyanate (hydrogenated MDI),
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, or
any combination thereof.
9. The chemical mechanical polishing pad of claim 1, wherein the
thermoplastic polyurethane comprises a repeating unit derived from
a polyether polyol, a polyester polyol, a polycarbonate polyol, a
polyolefin polyol, or any combination thereof.
10. The chemical mechanical polishing pad of claim 1, wherein the
composition further comprises an additional polymer compound other
than the thermoplastic polyurethane.
11. The chemical mechanical polishing pad of claim 10, wherein the
additional polymer has a water absorption of from 3 to 3000%.
12. The chemical mechanical polishing pad of claim 10, wherein the
additional polymer comprises an ether bond, an ester bond, an amide
bond, or any combination thereof.
13. The chemical mechanical polishing pad of claim 6, wherein the
water-soluble particles are uniformly dispersed in the composition.
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 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,
JP-A-2000-17252 or Japanese Patent No. 3956364 discloses a
polishing pad formed using a polyurethane foam, JP-A-2007-284625
discloses a polishing pad wherein the degree of crosslinking of a
urethane resin is controlled by adjusting the amount of a polyol or
an isocyanate so as to control the property values, and
JP-A-2003-332277 discloses a polishing pad wherein the properties
of the uppermost surface of the polishing layer are controlled, for
example.
SUMMARY OF THE INVENTION
Technical Problem
[0004] These chemical mechanical polishing pads formed using a
known material are designed to improve the planarity of the
polishing target surface during CMP by increasing the modulus of
elasticity of the polishing layer, and the relationship between the
specific gravity and the hardness of the polishing layer has not
been sufficiently studied.
[0005] For example, the polishing pad disclosed in Japanese Patent
No. 3956364 includes a polishing layer having a porous structure in
order to increase the modulus of elasticity of the polishing layer.
Although the polishing layer is formed using a material having high
hardness, the specific gravity of the polishing layer decreases due
to the porous structure, and the polishing layer is easily deformed
to follow elevations and depressions of the polishing target
surface due to the cushion effect of the porous structure.
Therefore, the polishing target surface may be insufficiently
planarized during CMP.
[0006] When suppressing deformation of the polishing layer along
elevations and depressions of the polishing target surface by
merely increasing the specific gravity of the polishing layer, the
hardness of the polishing layer increases, so that the number of
polishing defects (scratches) may increase due to polishing waste
or pad waste that has entered the space between the polishing
target surface and the polishing layer.
[0007] 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 while
suppressing occurrence of polishing defects (scratches) during CMP,
and a chemical mechanical polishing method that utilizes the
chemical mechanical polishing pad.
Solution to Problem
[0008] The invention was conceived in order to solve at least some
of the above problems, and may be implemented by the following
aspects or application examples.
Application Example 1
[0009] According to one aspect of the invention, there is provided
a chemical mechanical polishing pad including a polishing layer
formed using a composition that includes a thermoplastic
polyurethane, the polishing layer having a specific gravity of 1.15
to 1.30 and a durometer D hardness of 50 to 80.
Application Example 2
[0010] In the chemical mechanical polishing pad according to
Application Example 1, the polishing layer may have a residual
strain of 2 to 10% when applying tension to the polishing
layer.
Application Example 3
[0011] In the chemical mechanical polishing pad according to
Application Example 1 or 2, the polishing layer may have a volume
change rate of 0.8 to 5.0% when immersed in water at 23.degree. C.
for 24 hours.
Application Example 4
[0012] In the chemical mechanical polishing pad according to any
one of Application Examples 1 to 3, the polishing layer may have a
surface hardness of 2 to 10 N/mm.sup.2 after being immersed in
water at 23.degree. C. for 4 hours.
Application Example 5
[0013] In the chemical mechanical polishing pad according to any
one of Application Examples 1 to 4, the thermoplastic polyurethane
may include a repeating unit derived from at least one compound
selected from an alicyclic isocyanate and an aromatic
isocyanate.
Application Example 6
[0014] In the chemical mechanical polishing pad according to any
one of Application Examples 1 to 5, the composition may further
include water-soluble particles.
Application Example 7
[0015] According to another aspect of the invention, there is
provided a chemical mechanical polishing method including
chemically and mechanically polishing a polishing target using the
chemical mechanical polishing pad according to any one of
Application Examples 1 to 6.
Effects of the Invention
[0016] The chemical mechanical polishing pad according to one
aspect of the invention can improve the planarity of the polishing
target surface while suppressing occurrence of polishing defects
(scratches) during CMP since the chemical mechanical polishing pad
includes the polishing layer that is formed using the composition
that includes the thermoplastic polyurethane, and has a specific
gravity and a hardness within the specific range.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1A is a schematic view illustrating the concept of the
durometer D hardness of a polishing layer.
[0018] FIG. 1B is a schematic view illustrating the concept of the
durometer D hardness of a polishing layer.
[0019] FIG. 2 is a schematic view illustrating the concept of the
residual strain of a polishing layer when applying tension.
[0020] FIG. 3A is an enlarged view of an area I in FIG. 2 that
illustrates the concept of the residual strain of a polishing layer
when applying tension.
[0021] FIG. 3B is an enlarged view of an area I in FIG. 2 that
illustrates the concept of the residual strain of a polishing layer
when applying tension.
[0022] FIG. 3C is an enlarged view of an area I in FIG. 2 that
illustrates the concept of the residual strain of a polishing layer
when applying tension.
[0023] FIG. 3D is an enlarged view of an area I in FIG. 2 that
illustrates the concept of the residual strain of a polishing layer
when applying tension.
[0024] FIG. 3E is an enlarged view of an area I in FIG. 2 that
illustrates the concept of the residual strain of a polishing layer
when applying tension.
[0025] FIG. 4A is a schematic view illustrating the concept of the
volume change rate of a polishing layer.
[0026] FIG. 4B is a schematic view illustrating the concept of the
volume change rate 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] Preferred embodiments of the invention are described in
detail below. Note that the term "wet state" used herein refers to
the state of a 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 a 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 on at least
one side. The term "polishing layer" used herein refers to a layer
having a surface that comes in contact with a polishing target
during CMP (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". The polishing layer is formed by the
following method using a composition that includes a thermoplastic
polyurethane (hereinafter may be referred to as "thermoplastic
polyurethane-containing composition"). The polishing layer has a
specific gravity of 1.15 to 1.30 and a durometer D hardness of 50
to 80. The chemical mechanical polishing pad according to one
embodiment of the invention is described in detail 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 method using a thermoplastic
polyurethane-containing composition (hereinafter may be referred to
as "composition").
[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 has a specific gravity
and a hardness higher than those of the foamed polishing layer, the
non-foamed polishing layer is elastically deformed to a small
extent when coming in contact with elevations and depressions of
the polishing target surface (e.g., the surface of a wafer).
Therefore, the polishing target surface is sufficiently planarized.
However, since the hardness of the non-foamed polishing layer is
higher than that of 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] On the other hand, the foamed polishing layer normally has
low specific gravity and hardness. Therefore, polishing waste or
pad waste that has entered the space between the polishing target
surface (e.g., the surface of a wafer) and the polishing layer does
not come in contact with the polishing target surface at high
pressure since the surface of the foamed polishing layer is soft.
Polishing defects can thus be suppressed. However, since the foamed
polishing layer is elastically deformed to a large extent so as to
follow elevations and depressions 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) by forming a polishing layer using a
thermoplastic polyurethane-containing composition while controlling
the specific gravity and the hardness of the polishing layer.
1.1.1. Composition
1.1.1.1. Thermoplastic Polyurethane
[0035] A polishing layer that exhibits excellent flexibility can be
formed using a thermoplastic polyurethane-containing composition.
In this case, since polishing waste or pad waste that has entered
the space between the polishing target surface and the polishing
layer does not come in contact with the polishing target surface at
a high pressure, occurrence of polishing defects can be suppressed.
Since a polishing layer formed using a polyurethane obtained by
crosslinking a thermally crosslinkable polyurethane (thermosetting
polyurethane) does not exhibit sufficient flexibility, it is
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 firmly bonded, rarely swells even
when coming in contact with water as compared with a polishing
layer formed using a thermoplastic polyurethane, and has high
surface hardness in the wet state. Therefore, when the polishing
layer contains a crosslinked polyurethane, polishing waste or pad
waste that has entered the space between the polishing target
surface and the polishing layer comes in contact with the polishing
target surface at a high pressure due to the surface of the
polishing layer having high surface hardness, so that occurrence of
polishing defects may not be suppressed.
[0037] The thermoplastic polyurethane included in the composition
preferably includes a repeating unit derived from at least one
compound selected from an alicyclic isocyanate and an aromatic
isocyanate. When forming a polishing layer using a composition that
includes a thermoplastic polyurethane having such a chemical
structure, since it is possible to easily control the crystallinity
of the polyurethane, the specific gravity, the hardness, and the
like of the polishing layer 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 aromatic
diisocyanates such as 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,
and p-xylene diisocyanate. 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
the alicyclic isocyanate. When the thermoplastic polyurethane
includes a repeating unit derived from the alicyclic isocyanate,
the thermoplastic polyurethane exhibits appropriate hardness.
Moreover, it is possible to more appropriately control the surface
hardness of the resulting polishing layer in the wet state, and
provide the resulting polishing layer with higher flexibility.
[0042] The thermoplastic polyurethane included in the composition
preferably further includes 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 exhibits 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-butanediol, 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 thermoplastic polyurethane included in the composition
preferably includes a repeating unit derived from at least one
compound selected from the alicyclic isocyanate and the aromatic
isocyanate in an amount of 2 to 60 parts by mass, and more
preferably 3 to 55 parts by mass, based on 100 parts by mass of the
thermoplastic polyurethane. When the thermoplastic polyurethane
includes a repeating unit derived from at least one compound
selected from the alicyclic isocyanate and the aromatic isocyanate
in an amount within the above range, the thermoplastic polyurethane
exhibits appropriate hardness. Moreover, it is possible to
appropriately control the surface hardness of the resulting
polishing layer in the wet state, and provide the resulting
polishing layer with higher flexibility.
[0045] The thermoplastic polyurethane included in the composition
may be produced by a normal polyurethane production method (e.g.,
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
volume change of the polishing layer that may occur when the
polishing layer swells due to absorption of water.
[0047] The water-absorbing polymer compound more preferably
includes at least one type of 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 as determined by gel
permeation chromatography is 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, as described
below. Specifically, the polymer compound is formed into a sheet
(thickness: 2 mm) The sheet is cut to have a size of 2.times.2 cm,
and immersed in water at 23.degree. C. for 24 hours. The mass (M1)
of the sheet in air before being immersed in water and the mass
(M3) of the sheet in air after being immersed in water are
measured, and the mass change rate is calculated by the following
expression (1), and taken as the water absorption.
Water absorption (%)=((M3-M1)/M1).times.100 (1)
[0053] The composition preferably includes the water-absorbing
polymer compound in an amount of 1 to 20 parts by mass, more
preferably 3 to 15 parts by mass, and particularly preferably 5 to
10 parts by mass, based on the total amount (=100 parts by mass) of
the thermoplastic polyurethane and the water-absorbing polymer
compound. When the composition includes the water-absorbing polymer
compound in an amount within the above range, the volume change
rate of the polishing layer in the wet state can be easily
controlled within the range of 0.8 to 5.0%. When the volume change
rate 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.
When the composition includes the water-soluble particles, it is
preferable that the water-soluble particles be uniformly dispersed
in the composition. A polishing layer in which water-soluble
particles are uniformly dispersed can be formed using such a
composition.
[0055] When the polishing layer that includes the water-soluble
particles comes in contact with a polishing aqueous dispersion that
contains 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 hold the slurry
are formed. In this case, the slurry can be further sufficiently
held by the polishing layer since pores are formed in the surface
of the polishing layer without 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 due to the pores formed in
the surface 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 thermoplastic polyurethane-containing composition
includes the water-soluble particles, the following advantages 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, so that it is possible to improve
the planarity of the polishing target surface; (2) since a
non-foamed polishing layer is formed, the polishing layer exhibits
excellent mechanical strength; and (3) since it is unnecessary to
uniformly control a foamed cell structure, the 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, a
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] The water-soluble particles may be formed using one or more
materials among the materials for forming the organic water-soluble
particles or the inorganic water-soluble particles. The
water-soluble particles are preferably solid since the polishing
layer exhibits appropriate mechanical strength (e.g.,
hardness).
[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 composition
includes the water-soluble particles in an amount within the above
range, it is possible to form a polishing layer that achieves a
high chemical mechanical polishing removal rate, 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 pores
formed when the water-soluble particles are removed from the
surface of the polishing layer included in 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 obtain a chemical mechanical polishing pad that
includes a polishing layer that achieves a high polishing removal
rate and exhibits excellent mechanical strength.
1.1.2. Specific Gravity
[0063] The specific gravity of the polishing layer included in the
chemical mechanical polishing pad according to one embodiment of
the invention is 1.15 to 1.30, and preferably 1.18 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. It is also
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 1.15, the hardness of the polishing layer may
become too low, so that the polishing target surface may not be
sufficiently planarized. If the specific gravity of the polishing
layer is more than 1.30, the hardness of the polishing layer may
become too high, so that the number of polishing defects
(scratches) may increase.
[0064] The upper limit of the specific gravity of the polishing
layer is 1.30, taking account of the balance between the specific
gravity of a known 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. However, the
resulting polishing layer has high hardness due to the filler, so
that the number of scratches on the polishing target surface
increases to a large extent. Therefore, it is impossible to achieve
the effects of the invention.
[0065] The specific gravity of the polishing layer may be measured
in accordance with JIS Z 8807, as described below. 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 by measuring a change in water 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 obtain a
specific gravity within the above range. The term "non-foamed
polishing layer" used herein refers to a polishing layer that does
not substantially include bubbles. For reference, 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. Durometer D Hardness
[0067] The durometer D hardness of the polishing layer included in
the chemical mechanical polishing pad according to one embodiment
of the invention is 50 to 80, preferably 55 to 80, more preferably
55 to 75, and particularly preferably 60 to 70.
[0068] FIGS. 1A and 1B are schematic views illustrating the concept
of the durometer D hardness of the polishing layer. When applying
load to a polishing layer 10 from above (in the same manner as in a
polishing step) as illustrated in FIG. 1A, the polishing layer 10
is warped as illustrated in FIG. 1B. The durometer D hardness is an
index of the degree of macroscopic warping of the polishing layer
10 when applying load to the polishing layer 10 in the polishing
step. This can be understood by 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 since the polishing layer has moderate
durometer D hardness. It is also 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 durometer D
hardness of the polishing layer is less than 50, the polishing
target may not be sufficiently planarized. If the durometer D
hardness of the polishing layer is more than 80, the number of
polishing defects (scratches) may increase.
[0069] The durometer D hardness of the polishing layer may be
measured in accordance with JIS K 6253, as described below.
Specifically, 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 caused to come in 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 causing the
pressure plate to come in 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.
1.1.4. Residual Strain when Applying Tension
[0070] 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%.
[0071] A polishing layer normally has minute pores and/or
depressions in its surface. Polishing waste or pad waste is
gradually accumulated in the pores and/or the depressions (i.e.,
clogging occurs), so that the polishing properties of the polishing
pad deteriorate. 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 as to obtain a
surface in the initial state. The surface of the polishing layer
may be roughened, or pad waste may occur during diamond
conditioning.
[0072] FIG. 2 is a schematic view illustrating the concept of the
residual strain when applying tension to the polishing layer. FIGS.
3A to 3E are enlarged views of an area I in FIG. 2 that illustrate
the concept of the residual strain when applying tension to the
polishing layer. As illustrated in FIG. 2, the surface of the
polishing layer 10 is ground during diamond conditioning using a
dresser 20 that is rotated in the direction indicated by the arrow.
When dressing the polishing layer 10, part of the surface of the
polishing layer 10 is pulled by the dresser 20, as illustrated in
FIGS. 3A and 3B. As illustrated in FIG. 3C, part of the surface of
the polishing layer 10 is cut to produce pad waste. As illustrated
in FIG. 3D, an elongated portion 10b 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. 3E) is formed
corresponding 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.
[0073] 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 due to diamond conditioning can be 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, so that the number of polishing defects may increase due
to the pad waste in the polishing step. If the residual strain of
the polishing layer when applying tension to the polishing layer is
more than 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 exhibit
large deformation along elevations and depressions of the polishing
target surface. As a result, the polishing target surface may not
be sufficiently planarized.
[0074] The residual strain of the polishing layer when applying
tension to the polishing layer may be measured in accordance with
JIS K 6270, as described 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 specimens in the shape of a dumbbell 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 (2) 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 (2)
[0075] 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
23.degree. C. (allowance: .+-.2.degree. C.). The standard humidity
(relative humidity) in the test room is 50% (allowance:
.+-.10%).
1.1.5. Volume Change Rate
[0076] The volume change rate 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%.
[0077] FIGS. 4A and 4B are schematic views illustrating the concept
of the volume change rate of the polishing layer. The chemical
mechanical polishing pad is always exposed to the slurry during
polishing. As illustrated in FIG. 4A, a depression 30 is formed in
the polishing layer 10 to have given dimensions and a given shape.
As illustrated in FIG. 4B, 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 rate 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 rate of the polishing layer
is less than 0.8%, 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, so that occurrence of
scratches may not be sufficiently suppressed. If the volume change
rate of the polishing layer is more than 5%, the polishing layer
may swell to a large extent due to absorption of water, so that 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 dimensions or the shape 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.
[0078] The volume change rate of the polishing layer is determined
in accordance with JIS K 6258, as described below. Specifically, a
polishing layer having a thickness of 2.8 mm is cut to have a size
of 2.times.2 cm, and immersed in water at 23.degree. C. for 24
hours. The mass (M1) of the specimen in air before being immersed
in water, the mass (M2) of the specimen in water before being
immersed in water, the mass (M3) of the specimen in air after being
immersed in water, and the mass (M4) of the specimen in water after
being immersed in water are measured, and the volume change rate is
calculated by the following expression (3).
Volume change rate (%)=(((M3-M4)-(M1-M2))/(M1-M2)).times.100
(3)
1.1.6. Surface Hardness of Polishing Layer in Wet State
[0079] 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. An area of the
polishing layer 10 directly below the probe 40 is deformed as
illustrated in FIG. 5B due to the probe 40. The surface hardness
thus indicates the degree of deformation or warping of the
uppermost surface of the polishing layer. 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. 1A and 1B), 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, so that occurrence
of polishing defects (scratches) can be suppressed. If the surface
hardness of the polishing layer in the wet state is less than 2
N/mm.sup.2, the polishing target surface may not be sufficiently
planarized. If the surface hardness of the polishing layer in the
wet state exceeds 10 N/mm.sup.2, 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 a nano indenter ("HM2000"
manufactured by FISCHER) against the polishing layer (that has been
immersed in water at 23.degree. C. for 4 hours) at 300 mN.
1.1.7. Shape of Polishing Layer and Depressions
[0080] The planar shape of the polishing layer is not particularly
limited, but may be circular. 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.
[0081] A plurality of depressions may be formed in the polishing
surface of the polishing layer. The depressions serve as a path
that holds 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.
[0082] 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 depressions adjacent to each other
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 the
depressions adjacent to each other) 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 obtain a chemical
mechanical polishing pad that achieves an excellent effect of
suppressing occurrence of scratches in the polishing target surface
and has a long lifetime by forming the depressions as described
above.
[0083] Each preferable range 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.
[0084] 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
include a coating layer formed using diamond, or at least one metal
element selected from the 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 include 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 for the tool, the
material for the coating layer, and the like.
1.1.8. Production Method
[0085] The polishing layer included in the chemical mechanical
polishing pad according to one embodiment of the invention may be
obtained by molding the thermoplastic polyurethane-containing
composition. The composition may be mixed 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.
[0086] Depressions may be formed in the polishing surface of the
polishing layer by cutting. It is also possible to form the
depressions and the polishing layer at the same time by molding the
composition using a mold provided with a depression pattern.
1.2. Support Layer
[0087] 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.
[0088] 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
a cushion layer that has an adhesive layer on each side.
[0089] The adhesive layer may be a pressure-sensitive adhesive
sheet, for example. 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 such a uniform thickness that the polishing
performance is not affected by elevations or depressions of the
polishing target surface.
[0090] A material for forming the pressure-sensitive adhesive sheet
is not particularly limited insofar 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.
[0091] The adhesive strength of the pressure-sensitive adhesive
sheet is not particularly limited insofar 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 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, as
measured in accordance with AS Z 0237.
[0092] The material for forming the cushion layer is not
particularly limited insofar 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.
2. CHEMICAL MECHANICAL POLISHING METHOD
[0093] 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 thermoplastic polyurethane-containing
composition and has a specific gravity and a hardness within the
specific range. Therefore, the chemical mechanical polishing method
according to one embodiment of the invention can improve the
planarity of the polishing target surface and suppress occurrence
of polishing defects (scratches) during CMP.
[0094] 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 the
commercially available chemical mechanical polishing system include
EPO-112 and EPO-222 (all manufactured by Ebara Corporation);
LGP-510 and LGP-552 (all manufactured by Lapmaster SFT); Mirra and
Reflexion LK (all manufactured by Applied Materials); and the
like.
[0095] A suitable slurry may be appropriately selected depending on
the polishing target (e.g., copper film, insulating film, or
low-dielectric-constant insulating film).
3. EXAMPLES
[0096] 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
[0097] 50 parts by mass of a non-alicyclic thermoplastic
polyurethane ("Elastollan 1174D" manufactured by BASF, hardness:
70), 50 parts by mass of an alicyclic thermoplastic polyurethane
("Elastollan NY 1197A" manufactured by BASF, hardness: 61), 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 mixed using an
extruder heated to 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: 2.8 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. Examples 2 to 7 and Comparative Examples 1 to 3
[0098] Chemical mechanical polishing pads of Examples 2 to 7 and
Comparative Examples 1 to 3 were produced in the same manner as in
Example 1, except for changing the type and the amount of each
component of the composition as shown in Table 1 or 3.
3.1.3. Examples 8 and 9
[0099] A four-necked separable flask (2 l) equipped with a stirrer
was charged with 38 parts by mass of polyoxyethylene bisphenol A
ether ("Uniol DA400" manufactured by NOF Corporation) and 31 parts
by mass of polytetramethylene glycol ("PTG-1000SN" manufactured by
Hodogaya Chemical Co., Ltd., Mn=1012) in air. The mixture was
stirred at 40.degree. C. After the addition of 31 parts by mass of
4,4'-diphenylmethane diisocyanate ("MILLIONATE MT" manufactured by
Nippon Polyurethane Industry Co., Ltd., dissolved in an oil bath at
80.degree. C.), the mixture was stirred for 15 minutes. The mixture
was spread over a surface-treated SS vat, allowed to stand
(reacted) at 110.degree. C. for 1 hour, and annealed at 80.degree.
C. for 16 hours to obtain a thermoplastic polyurethane A. A
chemical mechanical polishing pad was produced in the same manner
as in Example 1, except for using the polyurethane A as the
thermoplastic polyurethane, and changing the type and the amount of
each component of the composition as shown in Table 1.
3.1.4. Example 10
[0100] 67 parts by mass of a thermoplastic polyurethane
("Elastollan 1174D" manufactured by BASF), 30 parts by mass of a
thermoplastic polyurethane ("Elastollan NY 1197A" manufactured by
BASF), 3 parts by mass of a polyolefin/polyether copolymer
("PELESTAT 300" manufactured by Sanyo Chemical Industries Ltd., a
water-absorbing polymer compound having a water absorption of 38%),
and 20 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 using an
extruder heated to 180.degree. C. to prepare a thermoplastic
polyurethane composition. A chemical mechanical polishing pad of
Example 10 was produced in the same manner as in Example 1, except
for using the thermoplastic polyurethane composition thus
prepared.
3.1.5. Examples 11 to 14
[0101] Chemical mechanical polishing pads of Examples 11 to 14 were
produced in the same manner as in Example 1, except for changing
the type and the amount of each component of the composition as
shown in Table 2.
3.1.6. Comparative Example 4
[0102] A four-necked separable flask (2 l) equipped with a stirrer
was charged with 25 parts by mass of hydroxy-terminated
polybutadiene ("NISSO PB 0-1000" manufactured by Nippon Soda Co.,
Ltd.) and 35.8 parts by mass of polytetramethylene glycol
("PTMG-1000SN" manufactured by Hodogaya Chemical Co., Ltd.) in air.
The mixture was stirred at 40.degree. C. After the addition of 30.5
parts by mass of 4,4'-diphenylmethane diisocyanate ("MILLIONATE MT"
manufactured by Nippon Polyurethane Industry Co., Ltd., dissolved
in an oil bath at 80.degree. C.), the mixture was stirred for 10
minutes. After the addition of 8.4 parts by mass of
3-methyl-1,5-pentanediol ("MPD" manufactured by Kuraray Ltd.), the
mixture was stirred. The mixture was spread over a surface-treated
SS vat, allowed to stand and react at 110.degree. C. for 1 hour,
and annealed at 80.degree. C. for 16 hours to obtain a
thermoplastic polyurethane B. A chemical mechanical polishing pad
was produced in the same manner as in Example 1, except for using
the polyurethane B as the thermoplastic polyurethane, and changing
the type and the amount of each component of the composition as
shown in Table 3.
3.1.7. Comparative Example 5
[0103] A commercially available chemical mechanical polishing pad
("IC 1000" manufactured by Rohm & Haas, including a polishing
layer formed using a thermally crosslinkable polyurethane) was
used. The properties of the polishing layer were evaluated by the
methods described below. The polishing layer had a specific gravity
of 0.81, a durometer D hardness of 63, and a surface hardness of
14.5 N/mm.sup.2.
3.1.8. Comparative Example 6
[0104] 100 parts by mass of 1,2-polybutadiene ("RB830" manufactured
by JSR Corporation, hardness: 47) and 38 parts by mass of
beta-cyclodextrin ("Dexy Pearl beta-100" manufactured by Ensuiko
Sugar Refilling Co., Ltd, average particle size: 20 micrometers)
(water-soluble particles) were mixed to prepare a composition. 1
part by mass of an organic peroxide ("Percumyl D-40" manufactured
by NOF Corporation) was added to 100 parts by mass of the
composition to prepare a thermally crosslinked polybutadiene resin
containing water-soluble particles. A chemical mechanical polishing
pad was produced in the same manner as in Example 1, except for
using the thermally crosslinked polybutadiene resin.
[0105] The abbreviation of each component shown in Tables 1 to 3
has the following meaning.
"PU1-1": non-alicyclic thermoplastic polyurethane ("Elastollan
1174D" manufactured by BASF, hardness: 70) "PU1-2": non-alicyclic
thermoplastic polyurethane ("Elastollan 1164D" manufactured by
BASF, hardness: 64) "PU1-3": non-alicyclic thermoplastic
polyurethane ("Elastollan 1180A" manufactured by BASF, hardness:
41) "PU2-1": alicyclic thermoplastic polyurethane ("Elastollan NY
1197A" manufactured by BASF, hardness: 61) "PU2-2": alicyclic
thermoplastic polyurethane ("Elastollan NY 1164D" manufactured by
BASF, hardness: 64) "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: 47) "Organic peroxide": dicumyl peroxide ("Percumyl D-40"
manufactured by NOF Corporation, crosslinking agent) "PM1":
polyolefin/polyether copolymer ("PELESTAT 300" manufactured by
Sanyo Chemical Industries Ltd., water absorption: 38%) "PM2":
polyalkylene oxide ("AQUA CALK TWB" manufactured by Sumitomo Seika
Chemicals Company Limited, water absorption: 2050%)
3.2. Measurement of Properties of Polishing Layer
3.2.1. Specific Gravity
[0106] 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 Tables 1 to 3.
3.2.2. Durometer D Hardness
[0107] 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 Tables 1 to
3.
3.2.3. Residual Strain when Applying Tension
[0108] 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 Tables
1 to 3.
3.2.4. Volume Change Rate
[0109] The volume change rate 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 rate of the polishing layer was measured in
accordance with JIS K 6258, as described below. Specifically, 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 being immersed in water, the
mass (M2) of the measurement specimen in water before being
immersed in water, the mass (M3) of the measurement specimen in air
after being immersed in water, and the mass (M4) of the measurement
specimen in water after being immersed in water were measured using
an electronic balance ("JP-300" manufactured by Cho Balance Co.,
Ltd.), and the volume change rate was calculated by the following
expression (3). The results are shown in Tables 1 to 3.
Volume change rate (%)=(((M3-M4)-(M1-M2))/(M1-M2)).times.100
(3)
3.2.5. Surface Hardness of Polishing Layer in Wet State
[0110] 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 Tables 1
to 3.
3.3. Evaluation of Chemical Mechanical Polishing
[0111] 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. A polishing target was
chemically mechanically polished using the dressed chemical
mechanical polishing pad under the following conditions, and the
polishing properties were evaluated as described below.
Head rotational speed: 61 rpm Head load: 3 psi (20.6 kPa) Table
rotational speed: 60 rpm Slurry supply rate: 300 cm.sup.3/min
Slurry: CMS8401/CMS8452 (manufactured by JSR Corporation)
3.3.1. Evaluation of Planarity
[0112] A polishing target (test substrate) was prepared by forming
a PETEOS film (thickness: 5000 angstroms) on a silicon substrate,
forming a mask pattern ("SEMATECH 854"), and sequentially forming 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.
[0113] The polishing target was chemically and mechanically
polished for 1 minute under the conditions described in the section
"3.3. Evaluation of chemical mechanical polishing". The thickness
of the polishing target was measured before and after CMP using an
electric conduction-type thickness measurement system ("OmniMap
RS75" manufactured by KLA-Tencor). The polishing removal rate was
calculated from the thickness of the polishing target before CMP,
the thickness of the polishing target after CMP, 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 patterned wafer (polishing target) 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 wherein 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 hi the direction
perpendicular to the longitudinal direction, using a precise 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 Tables 1 to 3. The
amount of dishing is preferably less than 300 angstroms, more
preferably less than 250 angstroms, and particularly preferably
less than 200 angstroms.
3.3.2. Evaluation of Scratches (Scratch Resistance)
[0114] The number of scratches that occurred on the polishing
target surface of the 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 Tables 1 to 3.
The number of scratches is preferably less than 40, more preferably
less than 20, and particularly preferably less than 15.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Example 5 Composition Thermoplastic PU1-1 (parts by mass) 50 30 60
50 -- polyurethane PU1-2 (parts by mass) -- -- -- -- 80 PU1-3
(parts by mass) -- -- -- -- -- PU2-1 (parts by mass) 50 70 40 50 --
PU2-2 (parts by mass) -- -- -- -- 20 Polyurethane A -- -- -- -- --
(parts by mass) Other component beta-CD (parts by mass) 29 29 78 78
29 Properties of Specific gravity 1.18 1.15 1.28 1.25 1.22
polishing layer Durometer D hardness 67 63 77 75 64 Residual strain
when applying tension (%) 4.8 7.8 5.5 5.0 7.2 Volume change rate
(%) 1.0 1.3 1.6 1.7 1.2 Surface hardness (N/mm.sup.2) 4.3 1.9 10.2
8.9 6.5 Chemical mechanical Number of scratches 14 7 26 19 14
polishing evaluation Amount of dishing (angstroms) 188 265 175 184
196 results Example 6 Example 7 Example 8 Example 9 Composition
Thermoplastic PU1-1 (parts by mass) -- -- -- -- polyurethane PU1-2
(parts by mass) -- 80 -- -- PU1-3 (parts by mass) 50 -- -- -- PU2-1
(parts by mass) 50 -- -- -- PU2-2 (parts by mass) -- 20 -- --
Polyurethane A -- -- 100 100 (parts by mass) Other component
beta-CD (parts by mass) 78 78 29 -- Properties of Specific gravity
1.17 1.24 1.18 1.16 polishing layer Durometer D hardness 54 75 73
65 Residual strain when applying tension (%) 9.8 2.0 2.5 5.0 Volume
change rate (%) 2.3 1.7 0.9 0.8 Surface hardness (N/mm.sup.2) 5.8
7.8 42 4.4 Chemical mechanical Number of scratches 6 28 16 18
polishing evaluation Amount of dishing (angstroms) 280 228 200 210
results
TABLE-US-00002 TABLE 2 Example 10 Example 11 Example 12 Example 13
Example 14 Composition Thermoplastic PU1-1 (parts by mass) 67 -- --
-- 85 polyurethane PU1-2 (parts by mass) -- 70 62 69 -- PU1-3
(parts by mass) -- -- -- -- -- PU2-1 (parts by mass) 30 -- -- -- --
PU2-2 (parts by mass) -- 20 20 30 10 Polyurethane A -- -- -- -- --
(parts by mass) Water-absorbing PM1 (parts by mass) 3 10 18 -- --
polymer compound PM2 (parts by mass) -- -- -- 1 5 Other component
beta-CD (parts by mass) 20 20 20 5 40 Properties of Specific
gravity 1.21 1.20 1.19 121 1.26 polishing layer Durometer D
hardness 67 62 60 64 72 Residual strain when applying tension (%)
9.8 7.8 8.2 7.0 9.5 Volume change rate (%) 1.7 22 2.8 3.2 4.6
Surface hardness (N/mm.sup.2) 6.8 5.8 4.2 4.7 7.2 Chemical
mechanical Number of scratches 35 18 5 16 4 polishing evaluation
Amount of dishing (angstroms) 190 210 250 240 280 results
TABLE-US-00003 TABLE 3 Compara- Compara- Compara- Compara- Compara-
Compara- tive tive tive tive tive tive Example 1 Example 2 Example
3 Example 4 Example 5 Example 6 Composition Thermoplastic PU1-1
(parts by mass) 50 100 -- -- IC 1000 -- polyurethane PU1-2 (parts
by mass) -- -- -- -- (commercially -- PU1-3 (parts by mass) -- --
100 -- available -- PU2-1 (parts by mass) 50 -- -- -- pad) -- PU2-2
(parts by mass) -- -- -- -- -- Polyurethane B -- -- -- 100 --
(parts by mass) Other component beta-CD (parts by mass) -- 78 29 29
38 Thermally crosslinked -- -- -- -- 100 polybutadiene resin (parts
by mass) Organic peroxide -- -- -- -- 1.38 (parts by mass)
Properties of Specific gravity 1.13 1.19 1.10 1.18 0.81 1.03
polishing layer Durometer D hardness 64 81 48 45 63 67 Residual
strain when applying tension (%) 13.7 1.9 28.7 10.5 8.0 7.0 Volume
change rate (%) 0.8 2.5 2.7 0.7 0.2 0.1 Surface hardness
(N/mm.sup.2) 4.0 14.1 3.2 2.1 14.5 8.9 Chemical mechanical Number
of scratches 12 103 19 2 125 130 polishing evaluation Amount of
dishing (angstroms) 380 295 540 540 310 350 results
3.4. Chemical Mechanical Polishing Pad Evaluation Results
[0115] As shown in Tables 1 and 2, the chemical mechanical
polishing pads of Examples 1 to 14 showed excellent results for the
flatness and the scratch resistance.
[0116] As shown in Table 3, the chemical mechanical polishing pads
of Comparative Examples 1 to 6 showed poor results for the flatness
and/or the scratch resistance. The chemical mechanical polishing
pad of Comparative Example 1 containing an alicyclic thermoplastic
polyurethane showed poor results for the flatness since the
specific gravity of the polishing layer was not within the range of
1.15 to 1.30. The chemical mechanical polishing pad of Comparative
Example 2 containing a non-alicyclic thermoplastic polyurethane
showed unacceptable results for the scratch resistance since the
durometer D hardness of the polishing layer was not within the
range of 50 to 80. The chemical mechanical polishing pad of
Comparative Example 3 containing a non-alicyclic thermoplastic
polyurethane showed significantly poor results for the flatness
since the specific gravity of the polishing layer was not within
the range of 1.15 to 1.30 and the durometer D hardness was not
within the range of 50 to 80. The chemical mechanical polishing pad
of Comparative Example 4 containing the thermoplastic polyurethane
B showed significantly poor results for the flatness since the
durometer D hardness of the polishing layer was not within the
range of 50 to 80. The chemical mechanical polishing pad of
Comparative Example 6 containing polybutadiene and water-soluble
particles showed poor results for the flatness and the scratch
resistance since the specific gravity of the polishing layer was
not within the range of 1.15 to 1.30.
[0117] The chemical mechanical polishing pad containing a thermally
crosslinked foamed polyurethane as produced in Comparative Example
5 showed poor results for the flatness and the scratch
resistance.
[0118] As is clear from the above results obtained in the examples
and the comparative examples, the chemical mechanical polishing pad
according to the embodiments of invention achieved excellent
flatness and scratch resistance as a result of specifying the
balance between the specific gravity and the hardness of the
polishing layer formed using a thermoplastic polyurethane.
[0119] The invention is not limited to the above embodiments.
Various modifications and variations may be made. 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 section (part) described in connection with the
above embodiments is replaced by another section (part). 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
[0120] 10: polishing layer, 10a: pad waste, 10b: elongated portion,
10b': roughened portion, 20: dresser, 30: depression, 40: probe
* * * * *