U.S. patent application number 10/822815 was filed with the patent office on 2004-11-11 for polishing pad and production method thereof.
This patent application is currently assigned to JSR CORPORATION. Invention is credited to Hasegawa, Kou, Igarashi, Yoshinori, Mihara, Iwao, Sakurai, Fujio.
Application Number | 20040224622 10/822815 |
Document ID | / |
Family ID | 32906023 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040224622 |
Kind Code |
A1 |
Sakurai, Fujio ; et
al. |
November 11, 2004 |
Polishing pad and production method thereof
Abstract
There are provided a polishing pad which exhibits excellent
polishing stability and excellent slurry retainability during
polishing and even after dressing, can prevent a reduction in
polishing rate effectively and is also excellent in an ability to
flatten an substrate to be polished, and a method for producing the
polishing pad. The method comprises dispersing water-soluble
particles such as .beta.-cyclodextrin into a crosslinking agent
such as a polypropylene glycol so as to obtain a dispersion, mixing
the dispersion with a polyisocyanate such as 4,4'-diphenylmethane
diisocyanate and/or an isocyanate terminated urethane prepolymer,
and reacting the mixed solution so as to obtain a polishing pad
having the water-soluble particles dispersed in the matrix.
Inventors: |
Sakurai, Fujio; (Tokyo,
JP) ; Mihara, Iwao; (Tokyo, JP) ; Igarashi,
Yoshinori; (Tokyo, JP) ; Hasegawa, Kou;
(Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JSR CORPORATION
Tokyo
JP
|
Family ID: |
32906023 |
Appl. No.: |
10/822815 |
Filed: |
April 13, 2004 |
Current U.S.
Class: |
451/526 |
Current CPC
Class: |
B24B 37/24 20130101;
B24D 3/342 20130101; B24D 18/00 20130101 |
Class at
Publication: |
451/526 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2003 |
JP |
2003-110853 |
Claims
What is claimed is:
1. A method for producing a polishing pad, comprising the steps of:
dispersing water-soluble particles in a crosslinking agent to
produce a dispersion, mixing the dispersion with a polyisocyanate
and/or an isocyanate terminated urethane prepolymer to produce a
mixed solution, and reacting the mixed solution to produce a
polishing pad comprising a polishing layer having the water-soluble
particles dispersed in a polymer matrix.
2. The method of claim 1, wherein the crosslinking agent has at
least two functional groups each of which has an active hydrogen
atom reactable with an isocyanate group, in a molecule.
3. The method of claim 1, wherein the crosslinking agent is a
polyol and/or a polyamine.
4. The method of claim 1, wherein the crosslinking agent comprises
a component having a number average molecular weight of not higher
than 5,000 in an amount of not smaller than 30 wt % based on 100 wt
% of the crosslinking agent.
5. The method of claim 1, wherein: the crosslinking agent is a
polyol, in the step of producing the mixed solution, an isocyanate
terminated urethane prepolymer, or a polyisocyanate and an
isocyanate terminated urethane prepoloymer is/are used, the
isocyanate terminated urethane prepolymer is obtained by reacting a
compound having at least two hydroxyl groups in a molecule with a
polyisocyanate in an equivalent ratio of the hydroxyl group (OH
group) to an isocyanate group (NCO group) of 1/1.8 to 1/2.4, and
the equivalent ratio of hydroxyl groups in the crosslinking agent
to isocyanate groups in the isocyanate raw material (OH group/NCO
group) is 1/0.9 to 1/1.4.
6. The method of claim 5, wherein the polyol is a diol and/or a
triol.
7. A polishing pad obtained according to the method of claim 1,
comprising a polishing layer having water-soluble particles
dispersed in a polymer matrix.
8. The polishing pad of claim 7, wherein the volume of the
water-soluble particles is 0.5 to 70% by volume when the volume of
the polishing layer in the polishing pad is 100%.
9. The polishing pad of claim 7, wherein a tensile product for a
tensile test at a temperature of 30.degree. C. and a pulling rate
of 500 mm/min is 50 to 20,000 kgf/cm.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing pad and a
method for producing the same. More specifically, it relates to a
polishing pad which has a polishing layer comprising a polymer
matrix and water-soluble particles dispersed in the polymer matrix,
and a method for producing the same. The pad can be suitably used
for polishing the surfaces of a semiconductor wafer and other
objects to be polished.
[0003] 2. Description of the Related Art
[0004] As a polishing method capable of forming a surface with a
high degree of smoothness, CMP (Chemical Mechanical Polishing) has
been receiving attention in recent years. In the CMP, a surface to
be polished is polished by sliding a polishing pad and the surface
against each other with slurry which is a water-based dispersion
having abrasive particles dispersed therein caused to flow down on
the surface of the polishing pad from above. One of factors which
significantly affect productivity in this CMP is a polishing rate.
It is conceived that this polishing rate can be significantly
improved by increasing the amount of retained slurry from a
conventional amount.
[0005] In the CMP, heretofore, a polyurethane foam containing fine
air bubbles is used as the polishing pad, and polishing is
performed with the slurry retained in holes (hereinafter referred
to as "pores") opened on a surface of the resin foam.
[0006] However, it is difficult to control the degree of foaming in
the polyurethane foam to a desired degree. It is very difficult to
control the sizes of the air bubbles, a foaming density and other
properties uniformly throughout the foam. Consequently, the quality
of the polishing pad comprising the polyurethane foam varies,
thereby causing a variation in the polishing rate and the state of
the produced polishing pad.
[0007] Various resins having soluble materials dispersed therein
are known as polishing pads whose formation of pores by foaming can
be controlled more easily (JP-A 8-500622 and JP-A 2000-33552, JP-A
2000-34416 and JP-A 2001-334455). Of these publications, the former
two publications suggest the effectiveness of the polishing pad
containing a soluble material. However, studies with respect to a
polymer matrix when actually used as the polishing pad have not
been made. Meanwhile, in the latter two publications,
constitutional materials thereof are studied, and more stable
polishing and an improvement in polishing rate are recognized.
However, much more stable polishing and further improvements in
slurry retainability and the polishing rate are required.
[0008] In addition, a further improvement in the level of
flattening a substrate to be polished is also required.
SUMMARY OF THE INVENTION
[0009] The present invention has been conceived in view of the
above circumstances. An object of the present invention is to
provide a polishing pad which exhibits excellent polishing
stability and excellent slurry retainability during polishing and
even after dressing, shows a high polishing rate, is excellent in
an ability to flatten a substrate to be polished and is free from
the occurrence of scratches, and a method for producing the
polishing pad.
[0010] Other objects and advantages of the present invention will
become apparent from the following description.
[0011] According to the present invention, firstly, the above
objects and advantages of the present invention are achieved by a
method for producing a polishing pad which comprises the steps
of:
[0012] dispersing water-soluble particles in a crosslinking agent
to produce a dispersion,
[0013] mixing the dispersion with a polyisocyanate and/or an
isocyanate terminated urethane prepolymer to produce a mixed
solution, and
[0014] reacting the mixed solution to produce a polishing pad
comprising a polishing layer having the water-soluble particles
dispersed in a polymer matrix.
[0015] According to the present invention, secondly, the above
objects and advantages of the present invention are achieved by a
polishing pad obtained by the above method of the present invention
which comprises a polishing layer having water-soluble particles
dispersed in a polymer matrix.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Hereinafter, the present invention will be described in
detail.
[0017] In a polishing pad, pores having functions such as retaining
slurry at the time of polishing and retaining polishing wastes
temporarily must be formed by the time of polishing. A polishing
pad of the present invention has a polishing layer which comprises
a polymer matrix comprising a polyurethane or a polyurethane-urea
and water-soluble particles dispersed in the polymer matrix. The
water-soluble particles make contact with slurry containing a
medium and a solid at the time of polishing and are detached by
dissolving into water or swelling due to water. Thereby, pores can
be produced. Owing to this mechanism, pores which are suitable for
retaining slurry and excellent in uniformity of pore sizes are
formed in the surface layer of the polishing pad of the present
invention which retains the slurry required for polishing. Further,
since the inside of the pad in which the water-soluble particles
exist is a non-porous structure, the polishing pad has a high
degree of hardness and a high compressive strength and has an
excellent ability to flatten a substrate to be polished. Further,
since a polymer matrix which is excellent in rupture strength and
abrasion resistance is obtained, deformation and abrasion of the
surface of the pad can be suppressed against a high pressure that
the polishing pad receives from a substrate to be polished during
polishing or an external force such as a dressing treatment by a
diamond dresser, excellent polishing stability and slurry
retainability can be obtained, and a high polishing rate can be
attained.
[0018] Water-Soluble Particles
[0019] In the present invention, the water-soluble particles are
dispersed in the polymer matrix. When the polishing pad is in use,
the water-soluble particles are detached from the water-insoluble
polymer matrix when they make contact with water for a dressing
treatment or slurry which is a water-based dispersion for polishing
in the surface layer of the pad. The detachment may also occur when
the water-soluble particles make contact with and dissolve into
water or water contained in the slurry. The detachment may also
occur when the water-soluble particles swell by absorbing the water
and become gel. Further, in addition to water, the water-soluble
particles may also be dissolved or swollen by making contact with a
water-based mixed medium containing an alcohol-based solvent such
as methanol.
[0020] In addition to the effect of forming pores, the
water-soluble particles also have an effect of increasing the
degree of indentation hardness of the polishing pad by being
present inside the polishing pad so as to reduce the degree of
indentation of a substrate to be polished by pressing. For example,
the polishing pad of the present invention can have a Shore D
hardness of 35 or higher, more preferably 50 to 95, much more
preferably 60 to 90, by containing the water-soluble particles.
When the Shore D hardness is 35 or higher, a high pressure can be
applied to the substrate to be polished, and a polishing rate can
be improved accordingly.
[0021] In addition, high polishing flatness of the substrate to be
polished is achieved by the presence of the water-soluble
particles. Thus, the water-soluble particles are preferably solid
particles which can ensure satisfactory indentation hardness in the
polishing pad.
[0022] A material constituting the water-soluble particles is not
particularly limited. For example, organic water-soluble particles
and inorganic water-soluble particles can be used. Illustrative
examples of materials of the organic water-soluble particles
include saccharides such as starch, polysaccharides such as dextrin
and cyclodextrin, lactose, mannitol, celluloses such as
hydroxypropylcellulose and methylcellulose, proteins, a polyvinyl
alcohol, a polyvinyl pyrrolidone, a polyacrylic acid and salts
thereof, a polyethylene oxide, water-soluble photosensitive resins,
a sulfonated polyisoprene and a sulfonated polyisoprene copolymer.
Meanwhile, illustrative examples of materials of the inorganic
water-soluble particles include potassium acetate, potassium
nitrate, potassium carbonate, potassium bicarbonate, potassium
chloride, potassium bromide, potassium phosphate and magnesium
nitrate. The above materials of the water-soluble particles may be
used alone or in combination of two or more.
[0023] Further, the average particle diameter of the water-soluble
particles is preferably 0.1 to 500 .mu.m, more preferably 0.5 to
300 .mu.m, much more preferably 1 to 100 .mu.m, most preferably 10
to 90 .mu.m. Further, the sizes of the pores which have been formed
by detachment of water-soluble particles are preferably 0.1 to 500
.mu.m, more preferably 0.5 to 300 .mu.m, much more preferably 1 to
100 .mu.m, particularly preferably 10 to 90 .mu.m. When the average
particle diameter of the water-soluble particles is smaller than
0.1 .mu.m, pores which are smaller in size than abrasive particles
used are formed, so that it is liable to become difficult to obtain
a polishing pad which can retain slurry sufficiently. Meanwhile,
when the average particle diameter is larger than 500 .mu.m, pores
of excessive sizes are formed, so that a polishing pad with low
mechanical strength and a low polishing rate is liable to be
obtained.
[0024] The content of the water-soluble particles is preferably 0.5
to 70% by volume, more preferably 1 to 60% by volume, much more
preferably 2 to 45% by volume, when the polishing layer comprising
the water-soluble particles and the polymer matrix is 100% by
volume. When the content of the water-soluble particles is lower
than 0.5% by volume, sufficient pores are not formed in the
polishing pad to be obtained, so that the polishing rate of the pad
is liable to be low. Meanwhile, when the content of the
water-soluble particles is higher than 70% by volume, it is liable
to be difficult to fully prevent swelling or dissolution of the
water-soluble particles present in the polishing pad at the time of
polishing, and it is therefore difficult to keep the hardness and
mechanical strength of the polishing pad at proper values.
[0025] Further, the content of the water-soluble particles on a
weight basis can be calculated in the following manner. For
example, when a saccharide having a specific gravity of about 1.5
is used as the water-soluble particles and a polyurethane showing a
specific gravity of 1.15 after completion of the reaction is used
as the polymer matrix, the water-soluble particles are 0.7 to 75.3
wt %, more preferably 1.3 to 66.2 wt %, much more preferably 2.6 to
51.6 wt % based on the polishing layer which is 100 wt %. Further,
when a polyacrylic acid, polyvinyl pyrrolidone or polyethylene
oxide having a specific gravity of about 1.15 is used as the
water-soluble particles and a polyurethane showing a specific
gravity of 1.15 after completion of the reaction is used as the
polymer matrix, the water-soluble particles are 0.5 to 70 wt %,
more preferably 1 to 60 wt %, much more preferably 2 to 45 wt %
based on the polishing layer which is 100 wt %. In addition, when
inorganic water-soluble particles such as potassium nitrate having
a specific gravity of about 2 are used as the water-soluble
particles and a polyurethane showing a specific gravity of 1.15
after completion of the reaction is used as the polymer matrix, the
water-soluble particles are 0.9 to 80.2 wt %, more preferably 1.7
to 72.3 wt %, much more preferably 3.4 to 58.7 wt % based on the
polishing layer which is 100 wt %.
[0026] Further, it is preferable that the water-soluble particles
be dissolved into water only when exposed to the surface layer of
the polishing pad and neither absorb moisture nor swell inside the
polishing pad. Thus, the water-soluble particle may have an outer
shell for inhibiting moisture absorption on at least a portion of
its surface. This outer shell may be physically adsorbed or
chemically bonded to the water-soluble particle. The shell may also
be in contact with the water-soluble particle by both physical
adsorption and chemical bonding. Illustrative examples of materials
which form such an outer shell include an epoxy resin, a polyimide
resin, a polyamide resin and a silicon resin. The outer shell can
still exert the above effect sufficiently even when it is formed on
only a portion of the surface of the water-soluble particle.
[0027] Crosslinking Agent
[0028] In the present invention, the crosslinking agent is a
compound which has, in a molecule, at least two functional groups
having active hydrogen reactable with an isocyanate group of a
polyisocyanate to be described later. Illustrative examples of the
functional groups having active hydrogen include a hydroxyl group,
a primary amino group, a secondary amino group and a carboxyl
group. In view of high reactivity with an isocyanate group, the
hydroxyl group and the amino groups are preferred. Further, the
hydroxyl group is more preferable for achieving good dispersion of
the water-soluble particles. The number of the
active-hydrogen-containing functional groups in a molecule is at
least 2 and may be 2 to 4 in particular. Of these, 2 or 3 is
preferred. Further, compounds having one or more of these
functional groups, e.g., a compound having two
active-hydrogen-containing functional groups in a molecule and a
compound having three active-hydrogen-containing functional groups
in a molecule, may be used in combination. An example of a
hydroxyl-group-containing compound is a polyol compound.
Illustrative examples of the polyol compound include diol compounds
having a hydroxyl group at both ends of a molecule such as a
polyether diol, polyester diol, polycarbonate diol, polyether
carbonate diol and polyester carbonate diol. In addition, a
polyfunctional polyether polyol, a polyfunctional polyester polyol,
a polyfunctional polycarbonate polyol, a polyfunctional polyether
carbonate polyol or a polyfunctional polyester carbonate polyol
which has at least three hydroxyl groups in a molecule can also be
used. Further, a polyfunctional low-molecular-weight alcohol having
at least two hydroxyl groups in a molecule can also be used.
[0029] Illustrative examples of the diol compounds having two
hydroxyl groups at both ends of a molecule include a polyether diol
such as an aliphatic polyether diol, an alicyclic polyether diol or
an aromatic polyether diol, a polyester diol, a polycarbonate diol,
a polycaprolactone diol, a polyol synthesized by a reaction between
a diol and a polyisocyanate, and other polyols. These polyols may
be used alone or in combination of two or more.
[0030] Specific examples of the aliphatic polyether diol include a
polyethylene glycol, a polypropylene glycol, a polytetramethylene
glycol, a polyhexamethylene glycol, a polyheptamethylene glycol, a
polydecamethylene glycol, and a polyether diol obtained by
subjecting at least two ion polymerizable cyclic compounds to
ring-opening copolymerization.
[0031] Specific examples of the above cyclic compounds include
cyclic ethers such as ethylene oxide, propylene oxide,
butene-1-oxide, isobutene oxide, 3,3-bischloromethyloxetane,
tetrahydrofuran, 2-methyl tetrahydrofuran, 3-methyl
tetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexene oxide,
styrene oxide, epichlorohydrin, glycidyl methacrylate, allyl
glycidyl ether, allyl glycidyl carbonate, butadiene monoxide,
isoprene monoxide, vinyl oxetane, vinyl tetrahydrofuran, vinyl
cyclohexene oxide, phenyl glycidyl ether, butyl glycidyl ether and
glycidyl benzoate.
[0032] Specific examples of the polyether diol obtained by
subjecting at least two ion polymerizable cyclic compounds to
ring-opening copolymerization include binary copolymer diols
obtained from a combination of tetrahydrofuran and propylene oxide,
a combination of tetrahydrofuran and 2-methyl tetrahydrofuran, a
combination of tetrahydrofuran and 3-methyl tetrahydrofuran, a
combination of tetrahydrofuran and ethylene oxide, a combination of
propylene oxide and ethylene oxide and a combination of
butene-1-oxide and ethylene oxide; and a ternary polymer diol
obtained from a combination of tetrahydrofuran, butene-1-oxide and
ethylene oxide.
[0033] Further, a polyether diol obtained by subjecting the above
cyclic compound and a cyclic imine such as ethylene imine; a cyclic
lactonic acid such as .beta.-propiolactone or lactide glycolate; or
dimethylcyclopolysiloxane to ring-opening copolymerization can also
be used. The above aliphatic polyether diols are also available as
commercial products such as PTMG650, PTMG1000 and PTMG2000
(products of Mitsubishi Chemical Corporation), PPG400, PPG1000 and
EXENOL720, 1020 and 2020 (products of ASAHI-OLIN LTD.), PEG1000 and
UNISAFE DC1100 and DC1800 (products of NOF CORPORATION), PPTG2000,
PPTG1000, PTG400 and PTGL2000 (products of HODOGAYA CHEMICAL CO.,
LTD.), Z-3001-4, Z-3001-5, PBG2000A, PBG2000B, EO/BO4000 and
EO/BO2000 (products of DAI-ICHI KOGYO SEIYAKU CO., LTD.),
PolyTHF250, PolyTHF650, PolyTHF1000, PolyTHF1800, PolyTHF2000
(products of BASF Japan Ltd.).
[0034] Specific examples of the alicyclic polyether diol include an
alkylene oxide added diol of hydrogenated bisphenol A, an alkylene
oxide added diol of hydrogenated bisphenol F, and an alkylene oxide
added diol of 1,4-cyclohexanediol. Further, specific examples of
the aromatic polyether diol include an alkylene oxide added diol of
bisphenol A, an alkylene oxide added diol of bisphenol F, an
alkylene oxide added diol of hydroquinone, an alkylene oxide added
diol of naphthohydroquinone, and an alkylene oxide added diol of
anthrahydroquinone. The above aromatic polyether diols are also
available as commercial products such as UNIOL DA400, DA700, DA1000
and DA4000 (products of NOF CORPORATION).
[0035] Illustrative examples of the polyester diol include a
polyester diol obtained by reacting a polyhydric alcohol with a
polybasic acid. Specific examples of the polyhydric alcohol include
ethylene glycol, a polyethylene glycol, propylene glycol, a
polypropylene glycol, tetramethylene glycol, a polytetramethylene
glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexane
dimethanol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, and
2-methyl-1,8-octanediol. Specific examples of the polybasic acid
include phthalic acid, isophthalic acid, terephthalic acid, maleic
acid, fumaric acid, adipic acid, and sebacic acid.
[0036] Specific examples of commercial products of the above
polyester diol include KURAPOL P-2010, P-1010, L-2010, L-1010,
A-2010, A-1010, F-2020, F-1010, PMIPA-2000, PKA-A, PNOA-2010 and
PNOA-1010 (products of KURARAY CO., LTD.).
[0037] Specific examples of the polycarbonate diol include a
polycarbonate of a polytetrahydrofuran and a polycarbonate of
1,6-hexanediol. Specific examples of commercial products of the
polycarbonate diol include DN-980, 981, 982 and 983 (products of
NIPPON POLYURETHANE INDUSTRY CO., LTD.), PC-8000 (product of PPG
Industries, Inc.) and PC-THF-CD (product of BASF
Aktiengesellshaft).
[0038] Illustrative examples of the polycaprolactone diol include a
polycaprolactone diol obtained by reacting .epsilon.-caprolactone
with a diol. Specific examples of the diol reacting with
.epsilon.-caprolactone include ethylene glycol, a polyethylene
glycol, propylene glycol, a polypropylene glycol, tetramethylene
glycol, a polytetramethylene glycol, a 1,2-polybutylene glycol,
1,6-hexanediol, neopentyl glycol, 1,4-cyclohexane dimethanol and
1,4-butanediol. These polycaprolactone diols are available as
commercial products such as PLACCEL 205, 205AL, 212, 212AL, 220 and
220AL (products of DAICEL CHEMICAL INDUSTRIES, LTD.).
[0039] Illustrative examples of the polyol compound having at least
three hydroxyl groups in a molecule include a polyether polyol,
polyester polyol, polycarbonate polyol, polyether carbonate polyol
and polyester carbonate polyol which are obtained by using, as a
starting polyol component, a triol such as glycerine,
trimethylolpropane, 1,2,6-hexanetriol or triethanolamine or a
tetraol such as pentaerythritol or tetramethylol cyclohexane; and a
trifunctional addition reaction product represented by the
following formula: 1
[0040] wherein a, b and c are each independently an integer of 0 to
100, in proviso that a, b and c is not 0 at the same time, and
resulting from addition of propylene oxide to glycerine. The
trifunctional addition reaction product is available as a
commercial product such as UNIOL TG330 (product of NOF
CORPORATION).
[0041] Specific examples of the low-molecular-weight alcohol having
at least two hydroxyl groups in a molecule include ethylene glycol,
1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and
trimethylolpropane.
[0042] An example of a compound having a primary or secondary amino
group is a polyamine compound. Specific examples of the polyamine
compound include organic diamine compounds such as
3,3'-dichloro-4,4'-diaminodiphe- nylmethane, chloroaniline modified
dichlorodiaminodiphenylmethane, 1,2-bis(2-aminophenylthio)ethane,
trimethylene glycol-di-p-amino benzoate and
3,5-bis(methylthio)-2,6-toluene diamine. Further, a compound having
three or more primary or secondary amino groups in a molecule can
also be used.
[0043] Illustrative examples of a carboxyl-group-containing
compound include aliphatic, aromatic, alicyclic and heterocyclic
dicarboxylic acid, tricarboxylic acid and tetracarboxylic acid.
[0044] Specific examples of the aliphatic dicarboxylic acid include
oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, azelaic acid and sebacic acid.
[0045] Specific examples of the aromatic dicarboxylic acid include
phthalic acid, isophthalic acid and terephthalic acid. Specific
examples of the alicyclic dicarboxylic acid include
cyclohexyldicarboxylic acid. Specific examples of the heterocyclic
dicarboxylic acid include naphthalenedicarboxylic acid. Specific
examples of the aliphatic tricarboxylic acid include citric acid
and aconitic acid.
[0046] As the crosslinking agent in the present invention, the
above active-hydrogen-containing compounds can be used alone or in
combination of two or more. Of these, a compound containing two
and/or three active hydrogens in a molecule is preferably used.
[0047] Particularly, as the compound containing two or three active
hydrogens in a molecule, the above diol and triol are preferably
used. When the diol and the triol are used in combination, the
amount of the diol is preferably 5 to 90 wt %, more preferably 20
to 70 wt %, based on the total of the diol and the triol which is
100 wt %. With the amounts of the diol and triol within this range,
well-balanced elongation and rupture strength can be imparted to
the polymer matrix such as urethane which forms the pad.
[0048] The crosslinking agent preferably contains a component
having a number average molecular weight of not higher than 5,000
in an amount of not smaller than 30 wt %, more preferably contains
a component having a number average molecular weight of not higher
than 2,000 in an amount of not smaller than 50 wt % and much more
preferably contains a component having a number average molecular
weight of not higher than 1,000 in an amount of not smaller than 70
wt %, based on the total of the crosslinking agent which is 100 wt
%.
[0049] The crosslinking agent particularly preferably contains a
component having a number average molecular weight of not higher
than 1,000 in an amount of 100 wt %.
[0050] As the low-molecular-weight component in the crosslinking
agent increases, polar bonds produced by bonding to isocyanate
increase in the eventually obtained polyurethane and intermolecular
hydrogen bonds increase. As a result, a cohesive force between
molecules becomes high, and a strong polymer matrix which can bear
deformation or rupture caused by an external force to a sufficient
degree can be obtained.
[0051] Dispersion
[0052] The dispersion in the present invention is obtained by
dispersing the above water-soluble particles in the above
crosslinking agent. A method of dispersing the water-soluble
particles is not particularly limited. For example, it is preferred
that the water-soluble particles be gradually added and dispersed
while the crosslinking agent is stirred in a container, so as to
obtain a good dispersion. Particularly preferred is a method of
dispersing the particles by a twin-screw stirring mixer which
provides a shearing force. A defoaming treatment by
depressurization or other means may be carried out during or after
dispersing as required.
[0053] Further, a dispersion aid can also be used as required.
Illustrative examples of the dispersion aid include a polymer,
block copolymer or random copolymer modified by an acid anhydride
group, a carboxyl group, a hydroxyl group, an epoxy group, an
oxazoline group or an amino group, and various nonionic surfactants
and coupling agents.
[0054] Polyisocyanate
[0055] As the polyisocyanate in the present invention, a compound
having at least two isocyanate groups in a molecule is used. As the
polyisocyanate compound, aromatic di- or triisocyanate, aliphatic
di- or triisocyanate, alicyclic di- or triisocyanate and a modified
polyisocyanate are preferably used. Specific examples of the
aromatic di- or triisocyanate include 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, phenylene diisocyanate, xylylene
diisocyanate, tetramethylxylene diisocyanate, 2,2'-diphenylmethane
diisocyanate, 2,4'-diphenylmethane diisocyanate,
4,4'-diphenylmethane diisocyanate, tolidine
diisocyanate[bis(4-isocyanate-3-methylphenyl)methane],
triphenylmethane triisocyanate and 1,5-naphthalene diisocyanate.
Specific examples of the aliphatic di- or triisocyanate include
1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,
trimethylhexamethylene diisocyanate, 1,10-decamethylene
diisocyanate, lysine diisocyanate and 1,3,6-hexamethylene
triisocyanate. Specific examples of the alicyclic di- or
triisocyanate include isophorone diisocyanate, hydrogenated
xylylene diisocyanate and hydrogenated diphenylmethane
diisocyanate. Specific examples of the modified polyisocyanate
include an adduct resulting from addition of a polyisocyanate to a
polyhydric alcohol, a dimer, a trimer with an isocyanurate ring,
modified allophanate, an urea modified polyisocyanate and a buret
modified polyisocyanate. Of these, the aromatic di- or
triisocyanate and the aliphatic di- or triisocyanate are preferably
used, and the aliphatic diisocyanate and the aromatic diisocyanate
are particularly preferably used. The above isocyanates can be used
alone or in combination of two or more.
[0056] Isocyanate Terminated Urethane Prepolymer
[0057] The isocyanate terminated urethane prepolymer is obtained by
reacting a compound having at least two hydroxyl groups in a
molecule with a polyisocyanate in an equivalent ratio of the
hydroxyl group/an isocyanate group of preferably 1/1.8 to 1/2.4,
more preferably 1/1.9 to 1/2.2. When the equivalent ratio of the
isocyanate group is less than 1.8, unreacted hydroxyl groups, i.e.,
a compound having an isocyanate group at only one end becomes
excessive, thereby causing the polyurethane matrix to be obtained
to have a low molecular weight or causing the unreacted OH groups
to remain in the polymer matrix; as a result, a change with time in
polishing performance due to deteriorations in the rupture
strength, abrasion resistance and water resistance of the
polyurethane matrix occurs. Meanwhile, when the equivalent ratio of
the isocyanate group is more than 2.4, the isocyanate terminated
urethane prepolymer to be obtained is liable to have poor storage
stability disadvantageously.
[0058] In synthesis of the isocyanate terminated urethane
prepolymer, the temperature may be increased to a temperature of 50
to 90.degree. C., and a tertiary amine or a metal catalyst such as
organotin may be used as a reaction catalyst. As the compound
having at least two hydroxyl groups in a molecule, the same
compounds as the hydroxyl-group-containing compounds enumerated
with respect to the above crosslinking agent can be used, for
example. As the polyisocyanate, the same compounds as those
enumerated with respect to the foregoing polyisocyanate can be
used, for example.
[0059] One or more of the above isocyanate terminated urethane
prepolymers may be used.
[0060] Mixed Solution of Dispersion with Polyisocyanate and/or
Isocyanate Terminated Urethane Prepolymer, and Reaction Thereof
[0061] As a method of preparing and reacting the above mixed
solution, any of (1) a one-shot method using only the
polyisocyanate as an isocyanate raw material without using an
isocyanate terminated prepolymer, (2) a prepolymer method using
only the isocyanate terminated prepolymer as an isocyanate raw
material and (3) a combination method using a combination of the
polyisocyanate and the isocyanate terminated prepolymer as an
isocyanate raw material can be employed. In any case, the
water-soluble particles are dispersed in the crosslinking agent in
advance, the resulting dispersion is mixed with the isocyanate raw
material, and a curing reaction is carried out so as to form the
polymer matrix. Thereby, inhibition of the polymer matrix curing
reaction by the water-soluble particles can be prevented, and the
water-soluble particles can be dispersed uniformly in the polymer
matrix to be obtained.
[0062] Further, of the above reaction methods, the prepolymer
method and the combination method are particularly preferred so as
to precisely control the molecular structure of the polymer matrix
to be obtained.
[0063] In the present invention, the crosslinking agent having an
active-hydrogen-containing functional group, the polyisocyanate and
the isocyanate terminated prepolymer are used in a ratio of
active-hydrogen-containing groups/isocyanate groups of preferably
1/0.9 to 1/1.4, more preferably 1/0.95 to 1/1.3. When the ratio of
the isocyanate to the active-hydrogen-containing groups is less
than 0.9, a large amount of the active-hydrogen-containing groups
remain unreacted, so that the polyurethane to be obtained has poor
water resistance, alkali resistance and acid resistance. When the
ratio of the isocyanate is more than 1.4, a large amount of the
isocyanate groups remain unreacted upon completion of the
polymerization reaction. The unreacted isocyanate groups cause a
crosslinking reaction as time elapses due to moisture, so that the
polymer matrix to be obtained becomes brittle.
[0064] In the synthesis reaction of the polymer matrix in the
present invention, the raw material mixture may be given heat
energy by heating, or a reaction accelerator may also be used as
required, so as to accelerate the reaction. Illustrative examples
of the reaction accelerator include tertiary amines such as
triethylamine, benzyldimethylamine, triethylene diamine,
tetramethylbutane diamine and 2-methyl-triethylene diamine, tin
compounds such as dibutyltin acetate, dibutyltin dilaurate,
dibutyltin maleate, dibutyltin di-2-ethyl-hexoate, dilauryltin
diacetate and dioctyltin diacetate, and a diazabicycloalkene and
salts thereof with organic acids.
[0065] For a polishing pad for a semiconductor wafer, the tertiary
amines and the diazabicycloalkene and salts thereof are preferably
used so as to prevent metal from remaining in the polishing
layer.
[0066] The temperature, time and pressure in the synthesis reaction
of the polymer matrix are not particularly limited. For a first
curing reaction, conditions under which the polymer matrix can be
reacted to a certain extent and released from a mold with low
adhesion and deformation are preferred. For example, the reaction
is preferably carried out at 30 to 170.degree. C. for 3 minutes to
24 hours, more preferably at 50 to 130.degree. C. for 5 minutes to
3 hours. Although it is possible to complete the curing reaction by
the first reaction, it is preferable to hold the polymer matrix at
80 to 150.degree. C. for 3 to 24 hours after completion of the
first reaction and carry out a second curing reaction, for the
purpose of fully completing the curing reaction.
[0067] Other Usable Additives
[0068] In addition to the foregoing components, the polymer matrix
and/or the water-soluble particles may contain one or more of
additives which are conventionally used in slurry, e.g., polishing
particles, an oxidizing agent and a surfactant. Thereby, polishing
can be carried out by giving only water to the polishing pad at the
time of polishing.
[0069] Illustrative examples of the above polishing particles
include silica particles, alumina particles, ceria particles,
zirconia particles, and titania particles. These can be used alone
or in combination of two or more.
[0070] Illustrative examples of the oxidizing agent include
hydrogen peroxide, peracetic acid, perbenzoic acid, organic
peroxides such as t-butyl hydroperoxide, permanganic acid compounds
such as potassium permanganate, dichromic acid compounds such as
potassium dichromate, halogen acid compounds such as potassium
iodate, nitric acid compounds such as iron nitrate, perhalogen acid
compounds such as perchloric acid, persulfates such as ammonium
persulfate and a heteropoly acid. Of these oxidizing agents,
hydrogen peroxide, the organic peroxides and the persulfates such
as ammonium persulfate are particularly preferred because their
decomposition products are harmless. These can be used alone or in
combination of two or more.
[0071] Illustrative examples of the above surfactant include a
cationic surfactant, an anionic surfactant and a nonionic
surfactant. Specific examples of the cationic surfactant include an
aliphatic amine salt and an aliphatic ammonium salt. Specific
examples of the anionic surfactant include fatty acid soap,
carboxylates such as an alkyl ether carboxylate, sulfonates such as
an alkyl benzene sulfonate, an alkyl naphthalene sulfonate and
.alpha.-olefin sulfonate, sulfates such as a higher alcohol
sulfate, an alkyl ether sulfate and a polyoxyethylene alkyl phenyl
ether sulfate, and phosphates such as an alkyl phosphate. These can
be used alone or in combination of two or more.
[0072] Further, in the polymer matrix, various other additives such
as a filler, a softener, an antioxidant, an ultraviolet absorber,
an antistatic agent, a lubricant and a plasticizer may be contained
as required, in addition to the above various materials which are
conventionally used in slurry. Of these, as the filler, a material
which improves rigidity such as calcium carbonate, magnesium
carbonate, talc or clay or a material having a polishing effect
such as silica, alumina, ceria, titania, zirconia, manganese
dioxide, dimanganese trioxide and barium carbonate may be used.
[0073] To incorporate the above usable additives into the polishing
layer of the polishing pad of the present invention, they must be
added to the raw materials used for forming the polymer matrix in
advance.
[0074] Polishing Pad
[0075] The polishing pad of the present invention is obtained as a
polishing pad which has a polishing layer having the water-soluble
particles dispersed in the polymer matrix by subjecting the above
mixed solution comprising the dispersion and the polyisocyanate
and/or the isocyanate terminated urethane prepolymer to the
reaction, for example, in a mold.
[0076] Further, the polishing pad preferably shows a tensile
product of 50 to 20,000 kgf/cm when a dumbbell-shaped type 3 test
piece is subjected to a tensile test which is conducted at a
pulling rate of 500 mm/min and a testing temperature of 30.degree.
C. in accordance with the JIS K 6251 "Method of Conducting Tensile
Test for Vulcanized Rubber" and ruptured. The tensile product is
more preferably 100 to 18,000 kgf/cm, much more preferably 500 to
15,000 kgf/cm.
[0077] When the tensile product is smaller than 50 kgf/cm, the
polishing layer is liable to be broken and has poor abrasion
resistance, and the useful life of the polishing pad is short.
Meanwhile, when it is larger than 20,000 kgf/cm, the polishing
layer is hardly broken, so that surface roughening by a diamond
dresser during use of the polishing pad does not easily occur,
retention of slurry on the surface of the polishing pad is
insufficient, and the polishing rate is low.
[0078] It is sufficient for the polishing layer to constitute at
least a portion of the polishing surface of the polishing pad. The
polishing layer preferably constitutes at least 50% of the
polishing surface, more preferably at least 80% of the polishing
surface, much more preferably at least 90% of the polishing
surface. As a matter of course, the whole polishing surface may
comprise the polishing layer.
[0079] An example of a portion other than the polishing layer is a
window portion for detecting an end point by use of an optical
end-point detecting device. As the window portion, a window portion
which shows a light transmittance of 0.1% or higher, preferably 2%
or higher, for light of any wavelength between 100 nm and 3,000 nm
at a thickness of 2 mm or shows an integration transmittance in any
wavelength range between 100 nm and 3,000 nm of 0.1% or higher,
preferably 2% or higher can be used.
[0080] Further, the polishing pad may be a single-layer pad or a
multilayer pad having other layers. When the polishing pad is the
multilayer pad, the polishing layer is included in the multilayer
pad as a portion constituting a polishing surface in the multilayer
pad. Illustrative examples of the layers other than the polishing
layer include a supporting layer disposed on the surface opposite
to the polishing surface of the polishing layer and a bonding layer
for laminating the supporting layer and the polishing layer.
[0081] The above supporting layer is a layer which supports the
polishing layer from the rear surface side thereof. The
characteristics of the supporting layer are not particularly
limited, but it is preferably softer than the polishing layer. With
a softer supporting layer, it can be prevented that the polishing
layer rises or the surface of the polishing layer bends at the time
of polishing and stable polishing can be performed, even when the
thickness of the polishing layer is as small as 0.5 mm or smaller.
The hardness of the supporting layer is generally not lower than
10%, preferably not higher than 90%, more preferably not higher
than 80%, particularly preferably not higher than 70% of the
hardness of the polishing layer. Further, the Shore D hardness of
the supporting layer is generally 1 or higher, preferably 70 or
lower, more preferably 60 or lower, much more preferably 50 or
lower.
[0082] Further, the supporting layer may be a foam or non-foam. In
addition, the shape of its-plane surface is not particularly
limited and may be the same as or different from that of the
polishing layer. The shape of the plane surface of the supporting
layer may be a circular shape or a polygonal shape such as a
rectangular shape, for example. Further, the thickness of the
supporting layer is also not particularly limited and may be
preferably 0.1 to 5 mm, more preferably 0.5 to 2 mm, for example.
When the polishing layer has the window portion for detecting an
end point by use of an optical end-point detecting device, the
supporting layer may also have a window portion which is similar to
or the same as that of the polishing layer so as not to block light
passing through the above window portion or may have a clipped
shape so as to allow light to pass through a clipped portion
without having window portion.
[0083] A material constituting the supporting layer is also not
particularly limited. An organic material is preferably used
because it is easily molded into a given shape and a given
characteristic and can impart moderate elasticity. As the organic
material, a variety of polymers can be used. The organic material
constituting the supporting layer may be a crosslinked polymer, a
pre-crosslinked polymer or an uncrosslinked polymer.
[0084] Further, the supporting layer may comprise only one layer or
two or more layers. In addition, the supporting layer and the
polishing layer may be in direct contact with each other and
laminated by such a method as thermal fusion. They may be laminated
via the above bonding layer. The bonding layer may be a layer of a
cured adhesive or a layer comprising an adhesive material such as
an adhesive tape.
[0085] The shape of the polishing pad of the present invention is
not particularly limited and may be a disk, belt or roller, for
example. The shape of the polishing pad is preferably selected as
appropriate according to a polishing device. Further, the size of
the polishing pad before use is also not particularly limited. In
the case of a disk-shaped polishing pad, the diameter is preferably
0.5 to 500 cm, more preferably 1.0 to 250 cm, particularly
preferably 20 to 200 cm, and the thickness is preferably larger
than 0.1 mm and not larger than 100 mm, particularly preferably 1
to 10 mm.
[0086] This polishing pad may be used in any polishing step. For
example, it may be used in an STI step in polishing a semiconductor
wafer, a damascene step of forming metal wiring of Al and Cu, a
damascene step in forming a via plug using Al, Cu and W, a dual
damascene step of forming the metal wiring and the via plug
simultaneously, a step of polishing an interlayer insulation film
(such as an oxidized film, Low-k or BPSG), a step of polishing a
nitrided film (such as TaN or TiN) and a step of polishing a
polysilicon or bare silicon.
[0087] On the polishing surface of the polishing pad, an open
groove can be formed. This groove has a function of retaining
slurry supplied at the time of polishing and distributing the
slurry on the polishing surface more uniformly. Further, the groove
also serves as a discharge path for retaining wastes including
abrasion chips produced by polishing and used slurry temporarily
and discharging the wastes to the outside. The outer shape of the
groove is not particularly limited and may be ring-shaped,
lattice-shaped and/or spiral, for example.
[0088] The shape on a plane surface of a ring-shaped groove is not
particularly limited and may be a circle, a polygon such as a
triangle, a rectangle or a pentagon, or an oval. Further, the
number of grooves formed on the polishing pad is not particularly
limited as long as it is 2 or more. Further, the positions of these
grooves are also not particularly limited. For example, these
grooves may be disposed around the same center or concentrically,
disposed eccentrically or disposed such that a plurality of other
ring-shaped grooves are disposed inside the polishing surface
surrounded by a cyclic groove. Of these configurations, a polishing
pad having the grooves disposed around the same center is
preferred, and a polishing pad having a plurality of ring-shaped
grooves disposed concentrically is more preferred. The polishing
pad having the grooves disposed around the same center is superior
to other polishing pads with respect to the above functions.
Further, by having the grooves concentrically, the polishing pad is
further superior in these functions, and formation of the grooves
is also easier.
[0089] Meanwhile, the shape of a cross section in the width
direction of the groove is also not particularly limited and may be
a shape formed by flat side faces and the flat bottom face (the
width of the groove on its open side may be equal to, larger than
or smaller than that on its bottom side), U-shaped or V-shaped, for
example.
[0090] A lattice-shaped groove may be formed by one continuous
groove or a plurality of independent grooves. Further, the shape on
a plane surface of each pattern constituting the lattice is not
particularly limited and may be a variety of polygons. Illustrative
examples of the polygons include quadrangles such as a square, a
rectangle, a trapezoid and a rhombus, a triangle, a pentagon and a
hexagon.
[0091] Meanwhile, the shape of a cross section in the width
direction of the groove is also not particularly limited and may be
a shape formed by flat side faces and the flat bottom face (the
width of the groove on its open side may be equal to, larger than
or smaller than that on its bottom side), U-shaped or V-shaped, for
example.
[0092] A spiral groove may be formed by one continuous groove or
two spiral grooves whose spiral directions are different. Further,
it may be formed by two spiral grooves whose spiral directions are
the same or three or more spiral grooves whose spiral directions
are the same or different.
[0093] Meanwhile, the shape of a cross section in the width
direction of the groove is also not particularly limited and may be
a shape formed by flat side faces and the flat bottom face (the
width of the groove on its open side may be equal to, larger than
or smaller than that on its bottom side), U-shaped or V-shaped, for
example.
[0094] The size of the groove is not particularly limited. For
example, the width of the groove is not smaller than 0.1 mm, more
preferably 0.1 to 5 mm, much more preferably 0.2 to 3 mm. It is
generally difficult to form a groove having a width or minimum size
of smaller than 0.1 mm. Further, the depth of the groove is
preferably not smaller than 0.1 mm, more preferably 0.1 to 2.5 mm,
much more preferably 0.2 to 2.0 mm. When the depth of the groove is
smaller than 0.1 mm, the useful life of the polishing pad is
excessively short disadvantageously. Further, the distance between
the grooves (for spiral grooves, a minimum distance between
adjacent portions in the diameter direction) is preferably not
smaller than 0.05 mm, more preferably 0.05 to 100 mm, much more
preferably 0.1 to 10 mm. It is difficult to form a groove having a
minimum distance of smaller than 0.05 mm. Further, a pitch which is
the total of the width of a groove and the distance between the
groove and an adjacent groove is preferably not smaller than 0.15
mm, more preferably 0.15 to 105 mm, much more preferably 0.3 to 13
mm, particularly preferably 0.5 to 2.2 mm.
[0095] The above preferable ranges may be combined. For example, it
is preferred that the width be not smaller than 0.1 mm, the depth
be not smaller than 0.1 mm and the minimum distance be not smaller
than 0.05 mm; it is more preferred that the width be 0.1 to 5 mm,
the depth be 0.1 to 2.5 mm and the minimum distance be 0.05 to 100
mm; and it is much more preferred that the width be 0.2 to 3 mm,
the depth be 0.2 to 2.0 mm and the minimum distance be 0.1 to 10
mm.
[0096] Further, the surface roughness of the internal surface of
the groove is preferably not larger than 20 .mu.m, more preferably
not larger than 15 .mu.m, much more preferably not larger than 10
.mu.m and generally not smaller than 0.05 .mu.m. With a surface
roughness of not larger than 20 .mu.m, scratches at the time of
polishing can be prevented effectively. It is to be understood that
the surface roughness is a value before use of the polishing pad of
the present invention.
[0097] When the internal surface of the groove has a surface
roughness of not larger than 20 .mu.m, the internal surface has no
large pits and projections. When the internal surface has large
pits and projections, particularly large projections, e.g.,
incompletely abraded portions produced in formation of the groove,
are detached from the surface during polishing and cause the
occurrence of scratches. Further, the scratches may also be
produced by foreign matter formed by compression of the detached
projections by a pressure or frictional heat during polishing or
foreign matter formed by contact between the detached projections
and abrasion chips or solids in slurry. Further, even during
dressing, these projections may be detached and cause a similar
problem.
[0098] Further, when the surface roughness is not larger than 20
.mu.m, the occurrence of the scratches can be prevented, and the
groove can exert functions as a groove, particularly a function of
distributing slurry on the polishing surface and a function of
discharging wastes to the outside, more efficiently.
[0099] In addition, the polishing pad of the present invention can
also have pits opened on the polishing surface side, in addition to
the grooves. The shape on a plane surface of the pit is not
particularly limited and may be a circle, a polygon such as a
triangle, a rectangle or a pentagon, or an oval, for example.
Further, the shape of a cross section of the pit is also not
particularly limited and may be a shape formed by flat side faces
and the flat bottom face (the size in a transverse cross-sectional
direction of the pit on its open side may be equal to, larger than
or smaller than that on its bottom side), U-shaped or V-shaped, for
example.
[0100] Further, as in the case of the surface roughness of the
internal surface of the groove, the surface roughness of the
internal surface of the pit is, for example, not larger than 20
.mu.m, preferably not larger than 15 .mu.m, more preferably not
larger than 10 .mu.m and generally not smaller than 0.05 .mu.m.
[0101] Such a groove can be formed by cutting the surface of the
polishing pad by a groove cutting machine with a blade. A material
constituting the blade is not particularly limited. As the
material, carbon steel, alloy steel, high-speed steel, a sintered
hard alloy, cermet, stellite, a very high pressure sintered body
and other ceramics can be used. The blade may be a single blade or
a multi-blade unit having a plurality of blades.
[0102] Further, it is also possible that a female shape of the
shape of such a groove is formed in a container (such as a mold)
used for polymerization in advance and a raw material mixture is
then poured into the container and undergoes a curing reaction so
as to form a polishing layer having the shape of the groove formed
on the surface without cutting.
EXAMPLES
[0103] Hereinafter, the present invention will be further described
with respect to Examples and Comparative Example. The constitutions
and evaluations of the polishing pads of Examples and Comparative
Example are shown in Table 1. The units for numbers representing
the amounts of constituents in Table 1 are parts by weight.
1 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 C. Ex. 1 Water-Soluble
Particles A> 14.5 14.5 70.0 4.0 2.5 -- .beta.-cyclodextrin
(Average Particle Diameter: 20 .mu.m) <Crosslinking Agent B>
B1 Trifunctional Addition Reaction Product of Glycerin and
Propylene Oxide 21.6 13.2 21.6 21.6 -- 21.6 (Average Molecular
Weight: 330 "UNIOL TG330") B1 Trimethylolpropane ("TMP") -- -- --
-- 2.2 -- B2 Difunctional Polytetramethylene Glycol (Average
Molecular Weight: 650 6.9 17.4 6.9 6.9 -- 6.9 "PTMG650") B2
1,6-hexanediol -- -- -- -- 11.1 -- (Proportion % of B2 when B1 + B2
= 100) 24.2 56.9 24.2 24.2 83.5 24.2 <Polyisocyanate D>
4,4'-diphenylmethane diisocyanate ("SUMIDUR 44S") 21.6 -- 21.6 21.6
21.6 <Terminal Isocyanate Prepolymer E> Difunctional
Polytetramethylene Glycol (Average Molecular Weight: 650 28.2 --
28.2 28.2 -- 28.2 "PTMG650") Difunctional Polytetramethylene Glycol
(Average Molecular Weight: 250 -- 23.1 -- -- -- -- "PolyTHF250")
4,4'-diphenylmethane diisocyanate 21.7 46.3 21.7 21.7 -- 21.7 Both
End Isocyanate Prepolymer ("ADIPRENE LFH 120") -- -- -- -- 86.7 --
(B + D + E) 100 100 100 100 100 100 <Reaction Accelerator>
2-methyltriethylenediamine ("Me-DABCO") 0.1 0.1 0.1 0.1 -- 0.1
ADEKASTAB BT 11 -- -- -- -- 0.015 -- Volume Fraction of
Water-Soluble Particles (%) 10 10 35 3 2 0 Tensile Product (kgf/cm)
2817 10320 1120 3530 9980 3860 Shore D Hardness 75 83 81 71 65 69
Polishing Rate (nm/min) 200 180 300 160 200 40 Presence of
Scratches None None None None None Many Flatness (nm) 50 30 80 40
30 130 Ex.: Example, C. Ex.: Comparative Example
Example 1
[0104] 28.2 parts by weight of polytetramethylene glycol (product
of Mitsubishi Chemical Corporation, trade name "PTMG650") with a
number average molecular weight of 650 which had two hydroxyl
groups at both ends of a molecule and 21.7 parts by weight of
4,4'-diphenylmethane diisocyanate (product of Sumika Bayer Urethane
Co., Ltd., trade name "SUMIDUR 44S") were charged into a reactor,
maintained at 90.degree. C. for 3 hours under agitation so as to
react and then cooled so as to obtain a both end isocyanate
prepolymer.
[0105] As a crosslinking agent, 21.6 parts by weight of addition
reaction product of glycerin and a propylene oxide (product of NOF
CORPORATION, trade name "UNIOL TG330") with a number average
molecular weight of 330 which had three hydroxyl groups and 6.9
parts by weight of polytetramethylene glycol "PTMG650" were used.
In the crosslinking agent, 14.5 parts by weight of
.beta.-cyclodextrin (product of BIO RESEARCH CORPORATION OF
YOKOHAMA, trade name "DEXPAL .beta.-100", average particle
diameter: 20 .mu.m) which was water-soluble particles was dispersed
by agitation, and as a reaction accelerator, 0.1 parts by weight of
2-methyltriethylenediamine (product of Air Products Japan, Inc.,
trade name "Me-DABCO") was dissolved by agitation. This mixture was
added to the reactor containing the above both end isocyanate
prepolymer.
[0106] Further, 21.6 parts by weight of 4,4'-diphenylmethane
diisocyanate "SUMIDUR 44S" was added to the above reactor
containing the both end isocyanate prepolymer, and the resulting
mixture was agitated at room temperature at 200 rpm for 2 minutes
and then defoamed under a reduced pressure so as to obtain a raw
material mixture.
[0107] This raw material mixture was poured into a mold having a
diameter of 60 cm and a thickness of 3 mm, kept at 80.degree. C.
for 20 minutes so as to react into a polyurethane and post-cured at
110.degree. C. for 5 hours so as to give a polishing pad having a
diameter of 60 cm and a thickness of 3 mm. The volume fraction of
the water-soluble particles with respect to the whole polishing
pad, i.e., the volume fraction of the water-soluble particles with
respect to the total of the volumes of the polyurethane matrix and
the water-soluble particles, was about 10%.
[0108] The obtained polishing pad showed a tensile product of 2,817
kgf/cm when a dumbbell-shaped type 3 test piece was subjected to a
tensile test at a pulling rate of 500 mm/min and a testing
temperature of 30.degree. C. in accordance with JIS K 6251 "Method
of Conducting Tensile Test for Vulcanized Rubber" and ruptured.
Further, the Shore D hardness of the pad was 75.
[0109] Further, the polishing performance of the polishing pad was
evaluated as follows.
[0110] (1) Polishing Rate and Presence or Absence of Scratches
[0111] An SiO.sub.2 solid film semiconductor wafer (product of
ADVANTEC CO., LTD., film thickness: 1,000 nm, thermal oxide wafer)
was polished for 2 minutes by use of the following conditions, and
a polishing rate and the presence or absence of scratches were
evaluated. The film thickness was measured before and after
polishing by use of an optical film thickness meter, and the
polishing rate was calculated from these film thicknesses.
Meanwhile, the scratches were checked by observing the polished
surface of the SiO.sub.2 film wafer after polishing under an
electron microscope. Further, to roughen the surface of the pad
before evaluation of the polishing performance, the surface was
treated for 20 minutes under the same conditions as those for
polishing except that a #100 diamond dresser was used and 1,500
ml/min of running water was used in place of slurry.
[0112] Slurry: 3-time diluted CMS1101 (product of JSR Corporation)
Chemical Mechanical Polishing Device: EPO112 (product of Ebara
Corporation)
[0113] Slurry Feed Rate: 200 ml/min
[0114] Polishing Load: 400 g/cm.sup.2
[0115] Revolution Speed of Surface Table: 30 rpm
[0116] Revolution Speed of Head: 31 rpm
[0117] As a result, the polishing rate was 200 nm/min, and few
scratches were found.
[0118] (2) Evaluation of Flatness
[0119] The polished amount of an SiO.sub.2 film in the concave
portion of the pattern when the initial level difference, which was
about 800 nm, of the convex portion of the pattern of a surface
SiO.sub.2 film patterned semiconductor wafer (product of SKW
Associates, Inc., trade name "SKW-7") having a pattern initial
level difference of about 800 nm was polished by use of the above
conditions was taken as flatness. The smaller this number is, the
better the ability of flattening the pattern wafer is. The film
thickness of the SiO.sub.2 film was measured before and after
polishing by an optical film thickness meter and calculated. As a
result, flatness was 50 nm which was considered good.
Example 2
[0120] 23.1 parts by weight of polytetramethylene glycol (product
of BASF Japan Ltd., trade name "PolyTHF250") with a weight average
molecular weight of 250 which had two hydroxyl groups at both ends
of a molecule and 46.3 parts by weight of 4,4'-diphenylmethane
diisocyanate "SUMIDULE 44S" were charged into a reactor, kept at
90.degree. C. for 3 hours under agitation so as to react and then
cooled so as to obtain a both end isocyanate prepolymer.
[0121] As a crosslinking agent, 13.2 parts by weight of "UNIOL
TG330" with a number average molecular weight of 330 which had
three hydroxyl groups and 17.4 parts by weight of
polytetramethylene glycol "PTMG650" were used. In the crosslinking
agent, 14.5 parts by weight of .beta.-cyclodextrin "DEXPAL
.beta.-100" which was water-soluble particles was dispersed by
agitation, and as a curing catalyst, 0.1 parts by weight of
2-methyltriethylenediamine "Me-DABCO" was dissolved by agitation.
This mixture was added to the reactor containing the above both end
isocyanate prepolymer. The resulting mixture was agitated at room
temperature at 200 rpm for 2 minutes and then defoamed under a
reduced pressure so as to obtain a raw material mixture.
[0122] This raw material mixture was poured into a mold having a
diameter of 60 cm and a thickness of 3 mm, kept at 80.degree. C.
for 20 minutes so as to react into a polyurethane and post-cured at
110.degree. C. for 5 hours so as to give a polishing pad having a
diameter of 60 cm and a thickness of 3 mm. The volume fraction of
the water-soluble particles with respect to the whole polishing
pad, i.e., the volume fraction of the water-soluble particles with
respect to the total of the volumes of the polyurethane matrix and
the water-soluble particles, was about 10%.
[0123] The obtained polishing pad showed a tensile product of
10,320 kgf/cm after subjected to a tensile test and a Shore D
hardness of 83.
[0124] Further, a polishing rate, the presence or absence of
scratches and flatness were evaluated in the same manner as in
Example 1. As a result, the polishing rate was 180 nm/min, few
scratches were found, and the flatness was 30 nm, indicating that
the flatness of a polished surface was very good.
Example 3
[0125] A raw material mixture for a polyurethane was obtained in
the same manner as in Example 1 except that the amount of
.beta.-cyclodextrin "DEXPAL .beta.-100" which was water-soluble
particles was changed to 70 parts by weight. Further, a reaction to
obtain a polyurethane and post-curing were carried out in the same
manner as in Example 1 so as to obtain a polishing pad having a
diameter of 60 cm and a thickness of 3 mm. The volume fraction of
the water-soluble particles with respect to the whole polishing
pad, i.e., the volume fraction of the water-soluble particles with
respect to the total of the volumes of the polyurethane matrix and
the water-soluble particles, was about 35%.
[0126] The obtained polishing pad showed a tensile product of 1,120
kgf/cm after subjected to a tensile test and a Shore D hardness of
81.
[0127] Further, a polishing rate, the presence or absence of
scratches and flatness were evaluated in the same manner as in
Example 1. As a result, the polishing rate was 300 nm/min, few
scratches were found, and the flatness was 80 nm which was
good.
Example 4
[0128] A raw material mixture for a polyurethane was obtained in
the same manner as in Example 1 except that the amount of
.beta.-cyclodextrin "DEXPAL .beta.-100" which was water-soluble
particles was changed to 4 parts by weight. Further, a reaction to
obtain a polyurethane and post-curing were carried out in the same
manner as in Example 1 so as to obtain a polishing pad having a
diameter of 60 cm and a thickness of 3 mm. The volume fraction of
the water-soluble particles with respect to the whole polishing
pad, i.e., the volume fraction of the water-soluble particles with
respect to the total of the volumes of the polyurethane matrix and
the water-soluble particles, was about 3%.
[0129] The obtained polishing pad showed a tensile product of 3,530
kgf/cm after subjected to a tensile test and a Shore D hardness of
71.
[0130] Further, a polishing rate, the presence or absence of
scratches and flatness were evaluated in the same manner as in
Example 1. As a result, the polishing rate was 160 nm/min, few
scratches were found, and the flatness was 40 nm which was
good.
Example 5
[0131] As a crosslinking agent, 2.2 parts by weight of
trimethylolpropane having three hydroxyl groups (product of BASF
Japan Ltd., trade name "TMP") and 11.1 parts by weight of
1,6-hexanediol having two hydroxyl groups (product of Wako Pure
Chemical Industries, Ltd.) were used. In the crosslinking agent,
2.5 parts by weight of .beta.-cyclodextrin (product of BIO RESEARCH
CORPORATION OF YOKOHAMA, trade name "DEXPAL .beta.-100", average
particle diameter: 20 .mu.m) which was water-soluble particles was
dispersed by agitation, and as a reaction accelerator, 0.015 parts
by weight of dibutyltin dimaleate (product of Asahi Denka Co.,
Ltd., trade name "ADEKASTAB BT 11") was dissolved by agitation. To
this mixture, 86.7 parts by weight of ADIPRENE LFH 120 (product of
Uniroyal Chemical Company, Inc.) which was commercially available
both end isocyanate prepolymer having a structure that
1,6-hexamethylene diisocyanate was reacted with both ends of a
polytetramethylene glycol was added. Thereafter, the resulting
mixture was agitated at room temperature at 200 rpm for 2 minutes
and then defoamed under a reduced pressure so as to obtain a raw
material mixture. Further, polymerization of polyurethane and
post-curing were carried out in the same manner as in Example 1 so
as to obtain a polishing pad having a diameter of 60 cm and a
thickness of 3 mm.
[0132] The volume fraction of the water-soluble particles with
respect to the whole polishing pad, i.e., the volume fraction of
the water-soluble particles with respect to the total of the
volumes of the polyurethane matrix and the water-soluble particles,
was about 2%.
[0133] The obtained polishing pad showed a tensile product of 9,980
kgf/cm after subjected to a tensile test and a Shore D hardness of
65.
[0134] Further, a polishing rate, the presence or absence of
scratches and flatness were evaluated in the same manner as in
Example 1. As a result, the polishing rate was 200 nm/min, few
scratches were found, and the flatness was 30 nm which was
good.
Comparative Example 1
[0135] A raw material mixture for a polyurethane was obtained in
the same manner as in Example 1 except that .beta.-cyclodextrin
which was water-soluble particles was not used. Further, a reaction
to obtain a polyurethane and post-curing were carried out in the
same manner as in Example 1 so as to obtain a polishing pad having
a diameter of 60 cm and a thickness of 3 mm and free of the
water-soluble particle.
[0136] The obtained polishing pad showed a tensile product of 3,860
kgf/cm after subjected to a tensile test and a Shore D hardness of
69.
[0137] Further, the tensile product, the Shore D hardness, a
polishing rate, the presence or absence of scratches and flatness
were evaluated in the same manner as in Example 1. As a result, the
polishing rate was 40 nm/min which was poor, and a number of
scratches were observed. The flatness was 130 nm which was
poor.
[0138] Comparative Example 1 (polishing pad containing no
water-soluble particles) showed a low polishing rate of 40 nm/min.
Further, it had many scratches and also showed a poor flatness of
130 nm. Meanwhile, in the case of the polishing pads of the present
invention of Examples 1 to 4, good results were obtained for all
physical properties, and well-balanced, excellent polishing pads
were obtained. Therefore, these polishing pads can be suitably used
for polishing the surface of a semiconductor wafer, et al.
[0139] As described in detail above, according to the method of the
present invention for producing a polishing pad, a polishing pad
which has water-soluble particles dispersed uniformly therein in a
matrix, a toughness and an excellent polishing-performance can be
obtained.
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