U.S. patent application number 11/115122 was filed with the patent office on 2005-11-03 for chemical mechanical polishing pad, manufacturing process thereof and chemical mechanical polishing method for semiconductor wafers.
This patent application is currently assigned to JSR Corporation. Invention is credited to Hasefawa, Kou, Hosaka, Yukio, Kawahashi, Nobuo, Miyauchi, Hiroyuki, Okamoto, Takahiro, Shiho, Hiroshi.
Application Number | 20050245171 11/115122 |
Document ID | / |
Family ID | 34935818 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050245171 |
Kind Code |
A1 |
Hosaka, Yukio ; et
al. |
November 3, 2005 |
Chemical mechanical polishing pad, manufacturing process thereof
and chemical mechanical polishing method for semiconductor
wafers
Abstract
There is provided a chemical mechanical polishing pad containing
a polishing substrate having a polishing surface and a
light-transmitting member fused to the polishing substrate. The
sectional form of the light-transmitting member when it is cut with
a plane parallel to the polishing surface is elliptic with a value
obtained by dividing its long diameter by its short diameter of
more than 1. The pad is capable of transmitting end-point detection
light without reducing its polishing efficiency in polishing a
semiconductor wafer.
Inventors: |
Hosaka, Yukio; (Chuo-ku,
JP) ; Shiho, Hiroshi; (Chuo-ku, JP) ;
Miyauchi, Hiroyuki; (Chuo-ku, JP) ; Okamoto,
Takahiro; (Chuo-ku, JP) ; Hasefawa, Kou;
(Chuo-ku, JP) ; Kawahashi, Nobuo; (Chuo-ku,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JSR Corporation
Tokyo
JP
|
Family ID: |
34935818 |
Appl. No.: |
11/115122 |
Filed: |
April 27, 2005 |
Current U.S.
Class: |
451/6 ;
451/41 |
Current CPC
Class: |
B24B 37/04 20130101;
B24D 18/0009 20130101 |
Class at
Publication: |
451/006 ;
451/041 |
International
Class: |
B24B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2004 |
JP |
2004-132525 |
Claims
What is claimed is:
1. A chemical mechanical polishing pad comprising a polishing
substrate having a polishing surface and a light-transmitting
member fused to the polishing substrate, the sectional form of the
light-transmitting member when it is cut with a plane parallel to
the polishing surface being elliptic with a value obtained by
dividing its long diameter by its short diameter of more than
1.
2. The chemical mechanical polishing pad according to claim 1,
wherein the light-transmitting member comprises a water-insoluble
material and water-soluble particles dispersed in the
water-insoluble material.
3. The chemical mechanical polishing pad according to claim 2,
wherein at least part of the water-insoluble material is a
crosslinked polymer.
4. The chemical mechanical polishing pad according to claim 3,
wherein the crosslinked polymer is 1,2-polybutadiene.
5. A process for manufacturing the chemical mechanical polishing
pad of claim 1, comprising fusing the polishing substrate to the
light-transmitting member in a metal mold for insert molding.
6. A method for the chemical mechanical polishing of a
semiconductor wafer with the chemical mechanical polishing pad of
claim 1, comprising detecting the end point of chemical mechanical
polishing with an optical end-point detector through the
light-transmitting member of the chemical mechanical polishing pad
of claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a chemical mechanical
polishing pad, a manufacturing process thereof and a method of
polishing a semiconductor wafer.
[0002] More specifically, it relates to a chemical mechanical
polishing pad capable of transmitting light without reducing its
polishing efficiency, a manufacturing process thereof and a method
of polishing a semiconductor wafer.
[0003] The present invention is used for the polishing of a
semiconductor wafer using an optical end-point detector.
DESCRIPTION OF THE PRIOR ART
[0004] In the polishing of a semiconductor wafer, after the purpose
of polishing is accomplished, the polishing end point for
terminating polishing can be determined based on a time obtained
empirically. However, various materials are used to form the
surface to be polished and the polishing time differs by each
material. It is conceivable that the material forming the surface
to be polished will change in the future. Further, the same can be
said of slurry used for polishing and a polishing machine.
Therefore, it is extremely inefficient to obtain a polishing time
which differs according to the above polishing factors empirically.
To cope with this, optical end-point detectors and processes using
optical means capable of directly observing the state of the
polished surface are now under study (JP-A 9-7985 and JP-A
2000-326220) (the term"JP-A" as used herein means an "unexamined
published Japanese patent application").
[0005] In the above optical end-point detectors and processes, a
window made of a hard and homogenous resin which can transmit
end-point detection light and having no essential ability of
absorbing and transporting a slurry material is formed in a
polishing pad to observe the polished surface only through this
window (JP-A 11-512977).
[0006] However, it is apprehended that the polishing efficiency of
the polishing pad is reduced or made non-uniform by forming the
window. Therefore, it is difficult to obtain a polishing pad which
has a large window or an increased number of windows to ensure the
detection of the end point by an optical end-point detector and
which is free from the reduction of its polishing efficiency.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to solve the above
problem and provide a polishing pad for a semiconductor wafer,
capable of transmitting end-point detection light without reducing
its polishing efficiency, a manufacturing process thereof, a
polishing pad manufacturing metal mold, a multi-layer polishing pad
and a method of polishing a semiconductor wafer.
[0008] Other objects and advantages of the present invention will
become apparent from the following description.
[0009] According to the present invention, firstly, the above
objects of the present invention are attained by a chemical
mechanical polishing pad comprising a polishing substrate having a
polishing surface and a light-transmitting member fused to the
polishing substrate, the sectional form of the light-transmitting
member when it is cut with a plane parallel to the polishing
surface being elliptic with a value obtained by dividing its long
diameter by its short diameter of more than 1.
[0010] Secondly, the above objects of the present invention are
attained by a process for manufacturing the above chemical
mechanical polishing pad, comprising fusing the polishing substrate
to the light-transmitting member in a metal mold for insert
molding.
[0011] Thirdly, the above objects of the present invention are
attained by a method for the chemical mechanical polishing of a
semiconductor wafer with the above chemical mechanical polishing
pad, comprising detecting the end point of chemical mechanical
polishing with an optical end-point detector through the
light-transmitting member of the above chemical mechanical
polishing pad of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a plan view of an example of a light-transmitting
member;
[0013] FIG. 2 is a plan view of another example of the
light-transmitting member;
[0014] FIG. 3 is a partial sectional view of an example of the
polishing pad of the present invention;
[0015] FIG. 4 is a partial sectional view of another example of the
polishing pad of the present invention;
[0016] FIG. 5 is a plan view of an example of the polishing pad of
the present invention;
[0017] FIG. 6 is a plan view of another example of the polishing
pad of the present invention;
[0018] FIG. 7 is a partial sectional view of an example of a metal
mold for molding the polishing pad;
[0019] FIG. 8 is a partial sectional view of another example of the
metal mold for molding the polishing pad;
[0020] FIG. 9 is a partial sectional view of still another example
of the metal mold for molding the polishing pad;
[0021] FIG. 10 is a diagram for explaining a polishing method using
the polishing pad of the present invention; and
[0022] FIG. 11 is a sectional view of an example of a material to
be polished.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The present invention will be described in detail
hereinunder.
[0024] Chemical mechanical polishing pad
[0025] The chemical mechanical polishing pad of the present
invention has a polishing substrate and a light-transmitting member
fused to the polishing substrate. The sectional form of the
light-transmitting member when it is cut with a plane parallel to
the polishing surface is elliptic with a value obtained by dividing
its long diameter by its short diameter (aspect ratio) of more than
1.
[0026] Polishing substrate
[0027] The planar shape of the polishing substrate constituting the
chemical mechanical polishing pad of the present invention is not
particularly limited and may be disk-like, polygonal or square
pole-like. The size of the polishing substrate is not particularly
limited. However, the shape and size of the polishing substrate are
preferably such that it is fitted to the platen of a chemical
mechanical polishing machine for use with the chemical mechanical
polishing pad of the present invention. The thickness of the
polishing substrate is more than 0.1 mm and 100 mm or less,
particularly preferably 1 to 10 mm.
[0028] The material for forming the polishing substrate is not
particularly limited if it can exhibit a function as a polishing
pad. It is preferred that pores having the function of holding
slurry during polishing and the function of retaining polishing
chips temporarily out of the functions of the polishing pad should
be formed by the time of polishing. Therefore, it is preferably a
material composed of water-soluble particles and a water-insoluble
matrix containing the water-soluble particles dispersed therein, or
a material composed of cavities and a water-insoluble matrix
material containing the cavities dispersed therein, for example, a
foam.
[0029] In the former material out of these, the water-soluble
particles come into contact with an aqueous medium of slurry
containing the aqueous medium and a solid at the time of polishing
and dissolve or swell to be eliminated, and the slurry can be held
in pores formed by elimination. In the latter material, the slurry
can be held in pores formed as the cavities.
[0030] The material for forming the above water-insoluble matrix is
not particularly limited but an organic material is preferably used
because it is easily molded to have a predetermined shape and
predetermined properties and can provide suitable hardness and
suitable elasticity. Examples of the organic material include
thermoplastic resins, elastomers, rubbers such as crosslinked
rubbers, and curable resins such as thermally or optically curable
resins and resins cured by heat or light. They may be used alone or
in combination.
[0031] Out of these, the above thermoplastic resins include
1,2-polybutadiene resin, polyolefin resins such as polyethylene,
polystyrene resins, polyacrylic resins such as (meth)
acrylate-based resins, vinyl ester resins (excluding acrylic
resins), polyester resins, polyamide resins, fluororesins such as
polyvinylidene fluoride, polycarbonate resins and polyacetal
resins.
[0032] The above elastomers include diene elastomers such as
1,2-polybutadiene, polyolefin elastomer (TPO), styrene-based
elastomers such as styrene-butadiene-styrene block copolymer (SBS)
and hydrogenated block copolymers thereof (SEBS), thermoplastic
elastomers such as thermoplastic polyurethane elastomers (TPU),
thermoplastic polyester elastomers (TPEE) and polyamide elastomers
(TPAE), silicone resin elastomers and fluororesin elastomers. The
rubbers include conjugated diene rubbers such as butadiene rubber
(high cis -butadiene rubber, low cis -butadiene rubber, etc.),
isoprene rubber, styrene-butadiene rubber and styrene-isoprene
rubber, nitrile rubbers such as acrylonitrile-butadiene rubber,-
acrylic rubber, ethylene-.alpha.-olefin rubbers such as
ethylene-propylene rubber and ethylene-propylene-diene rubber, and
other rubbers such as butyl rubber, silicone rubber and fluorine
rubber.
[0033] The above curable resins include urethane resins, epoxy
resins, acrylic resins, unsaturated polyester resins,
polyurethane-urea resins, urea resins, silicon resins, phenolic
resins and vinyl ester resins.
[0034] The above organic materials may be modified by an acid
anhydride group, carboxyl group, hydroxyl group, epoxy group or
amino group. The affinity for the water-soluble particles to be
described hereinafter and slurry of the organic material can be
adjusted by modification.
[0035] These organic materials may be used alone or in combination
of two or more.
[0036] Further, the organic material may be a partially or wholly
crosslinked polymer or non-crosslinked polymer. It is preferably
composed of a crosslinked polymer alone or a mixture of a
crosslinked polymer and a non-crosslinked polymer. When a
crosslinked polymer is contained, elastic recovery force is
provided to the water-insoluble matrix so that displacement caused
by shear stress applied to the polishing pad during polishing can
be reduced. Further, it is possible to effectively prevent the
pores from being filled by the plastic deformation of the
water-insoluble matrix when it is excessively stretched at the time
of polishing and dressing and the surface of the polishing pad from
being excessively fluffed. Therefore, the pores are formed
efficiently even during dressing, whereby a reduction in the
retainability of the slurry during polishing can be suppressed and
further the polishing pad is rarely fluffed, thereby not impairing
polishing flatness.
[0037] The method of crosslinking the above organic material is not
particularly limited. For example, chemical crosslinking making use
of an organic peroxide, sulfur or sulfur compound or radiation
crosslinking by applying an electron beam may be employed.
[0038] Out of the above organic materials, a crosslinked rubber,
curable resin, crosslinked thermoplastic resin or crosslinked
elastomer may be used as the crosslinked polymer. At least one
selected from a crosslinked thermoplastic resin, crosslinked
elastomer and polyurethane all of which are stable to a strong acid
or strong alkali contained in many kinds of slurry and are rarely
softened by water absorption is preferably contained. Out of the
crosslinked thermoplastic resin and crosslinked elastomer, what is
crosslinked with an organic peroxide is more preferred, and
crosslinked 1,2-polybutadiene is particularly preferred.
[0039] The content of the crosslinked polymer is not particularly
limited but preferably 30 vol % or more, more preferably 50 vol %
or more, particularly preferably 70 vol % or more and may be 100
vol % of the water-insoluble matrix. When the content of the
crosslinked polymer in the water-insoluble matrix is lower than 30
vol %, the effect obtained by containing the crosslinked polymer
may not be fully obtained.
[0040] The residual elongation after breakage (to be simply
referred to as "residual elongation at break" hereinafter) of the
above water-insoluble matrix containing a crosslinked polymer can
be 100% or less when a specimen of the above water-insoluble matrix
is broken at 80.degree. C. in accordance with JIS K 6251. That is,
the total distance between bench marks of the specimen after
breakage becomes 2 times or less the distance between the bench
marks before breakage. This residual elongation at break is
preferably 30% or less, more preferably 10% or less, particularly
preferably 5% or less and generally 0% or more. When the above
residual elongation at break is higher than 100%, fine pieces
scraped off from the surface of the polishing pad or stretched at
the time of polishing and surface renewal tend to fill the pores
disadvantageously. The"residual elongation at break" is an
elongation obtained by subtracting the distance between bench marks
before the test from the total distance between each bench mark and
the broken portion of the broken and divided specimen in a tensile
test in which a dumbbell-shaped specimen No. 3 is broken at a
tensile rate of 500 mm/min and a test temperature of 80.degree. C.
in accordance with the"vulcanized rubber tensile test method"
specified in JIS K 6251. The test is carried out at 80.degree. C.
because heat is generated by slide contact at the time of actual
polishing.
[0041] The above"water-soluble particles" are particles which are
eliminated from the water-insoluble material when they come into
contact with an aqueous dispersion for chemical mechanical
polishing in the polishing pad. This. elimination may occur when
they dissolve in water contained in this aqueous dispersion upon
their contact with water or when they swell and gel by absorbing
this water. Further, this dissolution or swelling is caused not
only by their contact with water but also by their contact with an
aqueous mixed medium containing an alcohol-based solvent such as
methanol.
[0042] The water-soluble particles have the effect of increasing
the indentation hardness of the polishing pad in addition to the
effect of forming pores in the polishing pad. For example, the
shore D hardness of the polishing pad of the present invention can
be set to preferably 35 or more, more preferably 50 to 90,
particularly preferably 60 to 85 and generally 100 or less by
adding the water-soluble particles. When the shore D hardness is 35
or more, pressure applied to the object to be polished can be
increased, and the polishing rate can be thereby improved. In
addition, high polishing flatness is obtained. Therefore, the
water-soluble particles are particularly preferably made of a solid
substance which can ensure sufficiently high indentation hardness
for the polishing pad.
[0043] The material for forming the water-soluble particles is not
particularly limited. They are, for example, organic water-soluble
particles or inorganic water-soluble particles. Examples of the
material of the organic water-soluble particles include saccharides
(polysaccharides such as starch, dextrin and cyclodextrin, lactose,
mannitol, etc.), celluloses (such as hydroxypropyl cellulose,
methyl cellulose, etc.), protein, polyvinyl alcohol, polyvinyl
pyrrolidone, polyacrylic acid, polyethylene oxide, water-soluble
photosensitive resins, sulfonated polyisoprene and sulfonated
polyisoprene copolymers. Examples of the material of the inorganic
water-soluble particles include potassium acetate, potassium
nitrate, potassium carbonate, potassium hydrogencarbonate,
potassium chloride, potassium bromide, potassium phosphate and
magnesium nitrate. These water-soluble particles may be used alone
or in combination of two or more. The water-soluble particles may
be made of a predetermined single material, or two or more
different materials.
[0044] The water-soluble particles have an average particle
diameter of preferably 0.1 to 500 .mu.m, more preferably 0.5 to 100
.mu.m. The pores are as big as preferably 0.1 to 500 .mu.m, more
preferably 0.5 to 100 .mu.m. When the average particle diameter of
the water-soluble particles is smaller than 0.1 .mu.m, the formed
pores become smaller in size than the abrasive grains in use,
whereby a polishing pad capable of holding slurry completely may be
hardly obtained. When the average particle diameter is larger than
500 .mu.m, the formed pores become too big, whereby the mechanical
strength and polishing rate of the obtained polishing pad may
lower.
[0045] The content of the water-soluble particles is preferably 1
to 60 vol %, more preferably 1 to 40 vol %, particularly preferably
2 to 30 vol % based on 100 vol % of the total of the
water-insoluble material and the water-soluble particles. When the
content of the water-soluble particles is set to the above range, a
polishing pad having a high polishing rate and excellent hardness
and mechanical strength is easily obtained.
[0046] It is preferred that the water-soluble particles should
dissolve in water only when they are exposed to the surface layer
of the polishing pad and should not absorb moisture or swell when
they are existent in the interior of the polishing pad. Therefore,
the water-soluble particles may have an outer shell for suppressing
moisture absorption on at least part of their outermost portion.
This outer shell may be physically adsorbed to the water-soluble
particle, chemically bonded to the water-soluble particle, or in
contact with the water-soluble particle by physical adsorption and
chemical bonding. The outer shell is made of epoxy resin,
polyimide, polyamide or polysilicate. Even when it is formed on
only part of the water-soluble particle, the above effect can be
fully obtained.
[0047] The water-insoluble matrix material constituting the
polishing pad comprising the latter water-insoluble matrix material
(foam, etc.) containing cavities dispersed therein is, for example,
a polyurethane, melamine resin, polyester, polysulfone or polyvinyl
acetate.
[0048] The average size of the cavities dispersed in the
water-insoluble matrix material is preferably 0.1 to 500 .mu.m,
more preferably 0.5 to 100 .mu.m.
[0049] The method of dispersing the above water-soluble particles
into the matrix material at the time of production is not
particularly limited. For instance, the matrix material and
water-soluble particles and optionally other additives are kneaded
together to obtain a dispersion. The shape of the obtained
dispersion is not particularly limited. For example, it is obtained
in the form of a pellet, crumb or powder. The matrix material is
preferably kneaded under heating so that it can be easily
processed. At this heating temperature, the water-soluble particles
are preferably solid.
[0050] When they are solid, the water-soluble particles are easily
dispersed while they show the above preferred average particle
diameter. Therefore, the types of the water-soluble particles are
preferably selected according to the processing temperature of the
used matrix material.
[0051] Light-transmitting member
[0052] The light-transmitting member is a member for forming a
portion having light transmission properties in part of the
polishing pad so that it forms a common surface together with the
polishing surface of the polishing substrate.
[0053] The sectional form of this light-transmitting member when it
is cut with a plane parallel to the polishing surface is elliptic
with a value obtained by dividing its long diameter by its short
diameter (aspect ratio) of more than 1. The term "elliptic" as used
herein comprehends a concept including, for example, a
mathematically elliptic shape as shown in FIG. 1 and a deformed
roughly elliptic shape like a hen's egg as shown in FIG. 2. The
above aspect ratio is preferably more than 1 and 20 or less, more
preferably 1.5 to 10, particularly preferably 1.5 to 5. When the
sectional form of the chemical mechanical polishing pad is
circular, the long diameter direction of the light-transmitting
member is preferably parallel to the diameter direction of the
polishing surface.
[0054] This light-transmitting member and the above polishing
substrate are fused together into a single body.
[0055] The term"fusion" refers to a state in which the
light-transmitting member and the polishing substrate are bonded
together by melting or dissolving at least the bonding surface(s)
of both or one of them without using an adhesive. For the
manufacture of the polishing pad, not only the bonding surface but
also the entire light-transmitting member may be molten to be
bonded, or the entire polishing substrate may be molten to be
bonded.
[0056] The method of fusing together the light-transmitting member
and the polishing substrate is not particularly limited. For
instance, it maybe (1) an insert molding method in which one of the
light-transmitting member and the polishing substrate is held in a
metal mold and the other member is injected and fused, (2) a method
in which the light-transmitting member and the polishing substrate
are manufactured in predetermined shapes and mated together, and
their contact surfaces are molten to be bonded together by infrared
welding, high-frequency welding, microwave welding or ultrasonic
welding, or (3) a method in which a solvent is applied to the
bonding surfaces of the light-transmitting member and the polishing
substrate to bond them together.
[0057] Since the light-transmitting member and the polishing
substrate of the polishing pad of the present invention are fused
together, there is no gap between the light-transmitting member and
the polishing substrate, whereby slurry does not leak to the rear
side of the polishing pad.
[0058] FIG. 3 and FIG. 4 are partial sectional views of the
polishing pad of the present invention when it is cut with a plane
perpendicular to the polishing surface and passing through the
light-transmitting member. The above light-transmitting member 12
may be the same in thickness as the polishing substrate 13 as shown
in FIG. 3 or thinner than the polishing substrate 13 as shown in
FIG. 4.
[0059] The number of the above light-transmitting members is not
particularly limited and may be one or more. The position(s) of the
light-transmitting member(s) is/are not particularly limited.
However, the light-transmitting member(s) should be arranged on the
polishing pad such that it/they is/are located in a portion(s)
through which the end-point detection light of a chemical
mechanical polishing machine for use with the chemical mechanical
polishing pad of the present invention passes.
[0060] The percentage of the area of the light-transmitting
member(s) to the total area of the polishing surface is preferably
10% or less, more preferably 0.005 to 10%, much more preferably
0.005 to 5%, particularly preferably 0.01 to 1%. By setting the
percentage to this range, end-point detection can be ensured and
high polishing efficiency can be obtained.
[0061] FIG. 5 and FIG. 6 show examples of the position(s) of the
light-transmitting member(s) of the polishing pad of the present
invention on the polishing surface.
[0062] As for the light transmission properties of the
light-transmitting member, when the thickness of the
light-transmitting member is 2 mm, it preferably has a
transmittance at a wavelength between 100 and 3,000 nm of 0.1% or
more or an integrated transmittance at a wavelength between 100 and
3,000 nm of 0.1% or more. This transmittance or integrated
transmittance is more preferably 1% or more, much more preferably
2% or more, particularly preferably 3% or more, ideally 4% or more.
The transmittance or integrated transmittance does not need to be
higher than required, and may be 50% or less, preferably 30% or
less, particularly preferably 20% or less.
[0063] In the polishing pad used for polishing using an optical
end-point detector, the light-transmitting member preferably has a
high transmittance at a wavelength range of 400 to 800 nm which is
frequently used as light for end-point detection. Therefore, the
transmittance at a wavelength of 400 to 800 nm preferably satisfies
the above requirement.
[0064] This transmittance is a value measured at a wavelength with
an UV absorptiometer which can measure the absorbance of a 2
mm-thick specimen at a predetermined wavelength. The integrated
transmittance can be obtained by integrating transmittances at a
predetermined wavelength range measured similarly.
[0065] The above light-transmitting member is composed of a
water-insoluble matrix material and optionally added water-soluble
particles. When water-soluble particles are added, they are
preferably dispersed into the water-insoluble matrix.
[0066] The water-insoluble matrix material (may be simply referred
to as "matrix material" hereinafter) constituting the above
light-transmitting member is preferably a thermoplastic resin,
thermosetting resin, elastomer, rubber or a combination thereof
which can provide light transmission properties. Although this
matrix material does not need to be transparent or semitransparent
if it has light transmission properties (which does not mean that
it transmits only visible light), it preferably has higher light
transmission properties, more preferably transparency.
[0067] The thermoplastic resin, thermosetting resin, elastomer,
rubber, etc. which can provide light transmission properties may be
the same as those listed for the water-insoluble matrix material
used in the above polishing substrate. These matrix materials maybe
used in combination of two or more. Further, the water- insoluble
matrix material may be a mixture of a polymer having a functional
group and a polymer having no functional group as explained in
detail for the above polishing substrate.
[0068] The matrix material may be a crosslinked polymer or
non-crosslinked polymer. At least part of the matrix material is
preferably a crosslinked polymer. For example, the matrix material
is a mixture of two or more materials and at least part of at least
one of the materials is a crosslinked polymer, or the matrix
material is only one material and at least part of the material is
a crosslinked polymer.
[0069] When at least part of the matrix material has a crosslinked
structure, elastic recovery force can be provided to the matrix
material. Therefore, it is possible to suppress displacement caused
by shearing stress applied to the polishing pad at the time of
polishing and to prevent the pores from being filled by the plastic
deformation of the matrix material when it is excessively stretched
at the time of polishing and dressing. It is also possible to
prevent the surface of the polishing pad from being fluffed
excessively. Consequently, the retainability of slurry at the time
of polishing is high, the retainability of slurry is easily
recovered by dressing, and further scratching can be prevented.
[0070] These crosslinked polymers are the same as those which have
been already described in detail for the above polishing
substrate.
[0071] Out of these crosslinked polymers, crosslinked
1,2-polybutadiene and polyurethane are particularly preferred
because they can provide sufficiently high light transmission
properties, are stable to a strong acid or strong alkali contained
in many kinds of slurry and further are rarely softened by water
absorption. This crosslinked 1,2-polybutadiene may be blended with
other rubber such as butadiene rubber or isoprene rubber. Further,
1,2-polybutadiene may be used alone as the matrix material.
[0072] The residual elongation after breakage (to be simply
referred to as"residual elongation at break" hereinafter) of the
matrix material at least part of which is a crosslinked polymer can
be set to 100% or less when a matrix material specimen is broken at
80.degree. C. in accordance with JIS K 6251. That is, it is a
matrix material having a total distance between bench marks of the
specimen after breakage which is 2 times or less the distance
between the bench marks before breakage. This residual elongation
at break is preferably 30% or less, more preferably 10% or less,
and particularly preferably 5% or less. As the residual elongation
at break becomes higher than 100%, fine pieces scraped off from the
surface of the polishing pad or stretched at the time of polishing
or surface renewal tend to fill the pores.
[0073] The "residual elongation at break" is an elongation obtained
by subtracting the distance between bench marks before the test
from the total distance between each bench mark and the broken
portion of the broken and divided specimen in a tensile test in
which a dumbbell-shaped specimen No. 3 is broken at a tensile rate
of 500 mm/min and a test temperature of 80.degree. C. in accordance
with the"vulcanized rubber tensile test method" specified in JIS K
6251. The test temperature is 80.degree. C. as the temperature
reached by slide contact at the time of actual polishing is about
80.degree. C.
[0074] The above water-soluble particles are dispersed in the
light-transmitting member. They are made of a substance capable of
forming pores by its contact with an aqueous medium supplied from
the outside at the time of polishing as described above.
[0075] The shape, size, content in the light-transmitting member
and material of the water-soluble particles are the same as those
of the water-soluble particles which have been described in detail
for the above polishing substrate.
[0076] It is preferred that the water-soluble particles should
dissolve in water or swell only when they are exposed to the
surface of the light-transmitting member and should not absorb
moisture or swell when they are existent in the interior of the
light-transmitting member without surfacing. Therefore, an outer
shell made of an epoxy resin, polyimide, polyamide or polysilicate
for suppressing moisture absorption may be formed on at least part
of the outer surface of the water-soluble particle.
[0077] The water-soluble particles have the function of matching
the indentation hardness of the light-transmitting member with that
of other portion of the polishing pad in addition to the function
of forming pores. The Shore D hardness of the entire polishing pad
is preferably set to 35 to 100 in order to increase pressure to be
applied at the time of polishing, improve polishing rate and obtain
high flatness. However, it is often difficult to obtain a desired
Shore D hardness only from the matrix material. In this case, the
shore D hardness can be increased to the same level as that of
other portion of the polishing pad by containing the water-soluble
particles, besides the purpose of forming pores. For this reason,
the water-soluble particles are preferably made of a solid material
capable of securing sufficiently high indentation hardness in the
polishing pad.
[0078] The method of dispersing the water-soluble particles in the
matrix material at the time of production may be the same as the
method which has been described for the above polishing
substrate.
[0079] The polishing pad of the present invention may have a fixing
layer for fixing the polishing pad on a polishing machine on the
rear surface opposite to the polishing surface at the time of
polishing. The fixing layer is not particularly limited if it can
fix the polishing pad itself.
[0080] This fixing layer may be a layer formed by using an adhesive
double-coated tape, for example, a layer comprising an adhesive
layer and a peel layer formed on the outer surface of the adhesive
layer, or an adhesive layer formed by applying an adhesive. The
peel layer may be formed on the outer surface of the adhesive layer
formed by applying an adhesive.
[0081] The adhesive material for forming the fixing layer is not
particularly limited. It is, for example, a thermoplastic,
thermosetting or optically curable acrylic adhesive or synthetic
rubber adhesive. Commercially available products of the adhesive
material include #442 of 3M Limited and #5511 and #5516 of Sekisui
Chemical Co., Ltd.
[0082] Out of these fixing layers, a layer formed by using an
adhesive double-coated tape is preferred because it has a peel
layer in advance. A fixing layer having a peel layer can protect an
adhesive layer before use and can easily fix the polishing pad on
the polishing machine by removing the peel layer at the time of
use.
[0083] The light transmission properties of the material of the
fixing layer are not particularly limited. When the material of the
fixing layer does not have light transmission properties or has low
light transmission properties, a through hole may be formed at a
position corresponding to the light-transmitting member. This
through hole may be larger or smaller than or the same as the area
of the light-transmitting member.
[0084] The fixing layer may not be formed in the path of
transmitted light when a through hole is formed in the fixing
layer.
[0085] Further, when a fixing layer is formed by using an adhesive
double-coated tape, a through hole can be formed at a predetermined
position of the adhesive double-coated tape. The method of forming
this through hole is not particularly limited. The through hole may
be formed with a laser cutter or punching blade. When a laser
cutter is used, the through hole may be formed after a fixing layer
is formed by using an adhesive double-coated tape.
[0086] Process for Manufacturing a Chemical Mechanical Polishing
Pad
[0087] Although the process for manufacturing the polishing pad of
the present invention is not particularly limited, the polishing
pad of the present invention is preferably manufactured by using
mainly the following metal mold for insert molding.
[0088] Metal Mold for Insert Molding
[0089] The metal mold for insert molding used in the process for
manufacturing the polishing pad of the present invention has a
projection portion(s) and/or a depressed portion(s) for positioning
the light-transmitting member or the polishing substrate, which has
been molded in advance.
[0090] The position, shape, size and number of the projection
portions and/or depressed portions for positioning the
light-transmitting member or the polishing substrate are not
particularly limited if they can position the light-transmitting
member or the polishing substrate.
[0091] As for the projection portion(s) for positioning the
light-transmitting member, (1) a plurality of, for example, 3 or 4
dot-like, point-like or prolonged projections 721 are arranged on a
lower mold 72 to surround the light-transmitting member as shown in
FIG. 7, (2) the above projection is arranged such that it is mated
with a depression formed in the center of the bottom of the
light-transmitting member, or (3) a ring projection, partially ring
projection or quadrilateral projection, for example, rectangular
projection is arranged such that it is mated with the
light-transmitting member having a circular bottom or quadrilateral
bottom to surround the light-transmitting member so as to form a
ring or square as a whole. Reference numeral 71 denotes an upper
mold.
[0092] As for the projection portion(s) for positioning the
polishing substrate, as shown in FIG. 8, a disk-like or thin square
pole-like projection 721 is formed on the lower mold 72 to be mated
with a hole for mounting the light-transmitting member of the
polishing substrate, or a dot-like, point-like or prolonged
projection is formed on the lower mold 72 to be mated with a
depression formed in the polishing substrate.
[0093] Since the surface of the projection portion for fixing this
polishing substrate is the surface for forming the surface layer of
the light-transmitting member, the surface of the projection
portion desirably has excellent flatness to improve the light
transmission properties of the light-transmitting member. It is
desirably planished.
[0094] As for the depressed portion(s) for positioning the
light-transmitting member, as shown in FIG. 9, a circular or
quadrilateral depression 722 is formed in the lower mold 72 to be
mated with the light-transmitting member, or depressions are formed
in the lower mold 72 to be mated with a plurality of dot-like,
point-like or prolonged projections formed on the
light-transmitting member.
[0095] Further, as for the depressed portion(s) for positioning the
polishing substrate, depressions may be arranged to be mated with
dot-like, point-like or prolonged projections formed on the bottom
portion of the polishing substrate.
[0096] Process for Manufacturing a Polishing Pad
[0097] The process for manufacturing the polishing pad of the
present invention is not particularly limited if the
light-transmitting member or the polishing substrate can be held in
the metal mold and the material for forming the light-transmitting
member or the polishing substrate can be injected into the cavity.
To facilitate the manufacture of the polishing pad of the present
invention, the above metal mold for insert molding is preferably
used.
[0098] This manufacturing process is preferably the following
process (1) or (2).
[0099] (1) A dispersion is obtained by pre-kneading a matrix, a
water-soluble substance, etc. for forming the light-transmitting
member. The obtained dispersion is molded in a metal mold having a
molding cavity to manufacture the light-transmitting member.
[0100] Then, this light-transmitting member is set in a metal mold
having a cavity and a dispersion for forming the polishing
substrate, obtained by kneading or the like, is injected into the
metal mold and molded to obtain a polishing pad.
[0101] Stated more specifically, the pre-molded light-transmitting
member is held between the projection portions of the metal mold
for insert molding having projection portions (see FIG. 7) for
positioning. Thereafter, the metal mold 71 is clamped and the
dispersion for forming the polishing substrate, obtained by
kneading or the like, is injected from an injection port into the
remaining space in the mold. This dispersion is solidified by
cooling to mold a polishing pad. Before the above metal mold is
closed, the dispersion for forming the polishing substrate may be
directly injected, and then the above metal mold may be clamped for
molding.
[0102] (2) A polishing substrate having a hole for accepting the
light-transmitting member is first molded and then set in a metal
mold having a cavity, a dispersion for forming the
light-transmitting member, obtained by kneading or the like, is
injected into the hole of the polishing substrate and molded in the
metal mold to manufacture the light-transmitting member, thereby
obtaining a polishing pad. The above hole may be a hole with a
bottom or a through hole without a bottom. A polishing substrate
having a through hole is preferably used.
[0103] Stated more specifically, a polishing substrate molded in a
predetermined shape is held onto the projection portion of a metal
mold for insert molding having the projection portion (see FIG. 8)
for positioning. Thereafter, the metal mold is clamped and the
dispersion for forming the light-transmitting member, obtained by
kneading or the like, is injected from an injection port to be
molded. Before the above metal mold is closed, the dispersion for
forming the light-transmitting member may be directly injected and
the above metal mold may be clamped for molding.
[0104] In the above processes (1) and (2), the inside temperature
of the metal mold for insert molding is preferably 30 to
300.degree. C., more preferably 40 to 250.degree. C., much more
preferably 50 to 200.degree. C.
[0105] The height of the light-transmitting member and the
thickness of the polishing substrate do not need to be the same
basically. Further, the flatness of the polished surface may be
improved and the polishing pad may be processed to a desired
thickness by grinding with sandpaper after molding.
[0106] A groove or dot pattern may be formed in a predetermined
shape on the polishing surface of the polishing pad of the present
invention as required in order to improve the discharge ability of
the used slurry. When the groove or dot pattern is required, it can
be obtained by forming a depression on the front side of the
polishing pad by reducing the thickness of the above
light-transmitting member.
[0107] Polishing Laminated Pad
[0108] The polishing pad of the present invention can be provided
as a polishing laminate having a base layer formed on the rear
surface.
[0109] The above "base layer" is a layer formed on the rear surface
opposite to the polishing surface of the polishing pad. It doesn't
matter whether the base layer has light transmission properties or
not. When a base layer made of a material having the same or higher
light transmission properties than the light-transmitting member is
used, light transmission properties are ensured for the polishing
laminated pad. In this case, a through hole may be or may not be
formed at a position corresponding to the light-transmitting member
of the base layer.
[0110] When a base layer having no light transmission properties is
used, the light transmission properties of the polishing laminated
pad can be secured by forming a through hole at a position
corresponding to the light-transmitting member.
[0111] The shape of the base layer is not particularly limited and
its planar shape may be quadrate, for example, quadrilateral, or
circular. Further, it can be formed as a sheet. This base layer
preferably has the same planar shape as the polishing pad. The
material for forming the base layer is not particularly limited and
various materials may be used. An organic material is preferably
used because it is easily molded to have a predetermined shape and
predetermined properties and can be provided with suitable
elasticity. The same materials as those used as the matrix material
of the above-described light-transmitting member may be used as
this organic material. The material for forming the base layer may
be the same or different from the matrix material(s) of the
light-transmitting member and/or the polishing substrate.
[0112] The number of the base layers is not particularly limited
and may be one or more. When two or more base layers are formed,
they may be the same or different. The hardness of the base layer
is not particularly limited but preferably lower than that of the
polishing pad. Thereby, the polishing laminated pad has
sufficiently high flexibility and suitable conformability to the
unevenness of the surface to be polished as a whole.
[0113] When the polishing pad of the present invention is a
polishing laminated pad, a fixing layer may be formed like the
above polishing pad. The fixing layer in the laminated pad is
preferably formed on the rear surface of the base layer, that is,
the surface opposite to the polishing surface. The fixing layer is
the same as that which has been explained for the above polishing
pad.
[0114] Method of Polishing a Semiconductor Wafer
[0115] The method of polishing a semiconductor wafer of the present
invention is to polish a semiconductor wafer with the polishing pad
of the present invention, using an optical end-point detector for
detecting the polishing end point of the semiconductor wafer.
[0116] The above optical end-point detector is capable of detecting
the polishing end point of the surface to be polished from light
reflected from the surface of an object to be polished by letting
light pass through the light-transmitting member to the polishing
surface side from the rear surface side of the polishing pad. Other
measurement principles are not particularly limited.
[0117] In the method of polishing a semiconductor wafer of the
present invention, the detection of the end point can be carried
out without reducing polishing efficiency. For example, when the
polishing pad or the polishing laminated pad is disk-like, the
light-transmitting members are arranged in a loop concentric to the
center of the disk so that polishing can be carried out while the
polishing end point is always monitored. Therefore, polishing can
be ended surely at the optimal polishing end point.
[0118] In the method of polishing a semiconductor wafer of the
present invention, a polishing machine shown in FIG. 10 may be
used. That is, the machine comprises a rotatable platen 2, a
pressure head 3 which can turn and move in vertical and horizontal
directions, a slurry feed unit 5 which can drop a predetermined
amount per unit time of slurry on the platen 2, and an optical
end-point detection unit 6 installed below the platen 2.
[0119] In this polishing machine, the polishing pad (including the
polishing laminated pad) 1 of the present invention is fixed on the
platen 2, and the semiconductor wafer 4 is fixed to the under
surface of the pressure head 3 and pressed against the polishing
pad at a predetermined pressure. Slurry is dropped on the platen 2
from the slurry feed unit 5 in a predetermined amount each time,
and the platen 2 and the pressure head 3 are turned to bring the
semiconductor wafer in slide contact with the polishing pad for
polishing.
[0120] End-point detection radiation R.sub.1 having a predetermined
wavelength or wavelength range is applied from the optical
end-point detection unit 6 to the polished surface of the
semiconductor wafer 4 from below the platen through the
light-transmitting member 12 for polishing. That is, the platen
itself has light transmission properties or a cut-out portion so
that the end-point detection radiation can pass therethrough.
Reflected radiation R.sub.2 obtained by reflecting this end-point
detection radiation R.sub.1 from the polished surface of the
semiconductor wafer 4 is seized by the optical end-point detection
unit 6 so that polishing can be carried out while the state of the
polished surface is monitored from this reflected radiation.
[0121] The suitable material to be polished by the polishing method
of the present invention is, for example, a laminated substrate
having a structure shown in FIG. 11. This laminated substrate
comprises a substrate made of silicon or the like, a first
insulating film made of silicon oxide or the like, a second
insulating film having a groove (such as a TEOS-based oxide film,
for example, a silicon oxide-based insulating film formed from
tetraethoxysilane by chemical vapor deposition, insulating film
having a low dielectric constant (such as silsequioxane,
fluorine-added SiO.sub.2, polyimide-based resin, benzocyclobutene,
etc.), etc.), a barrier metal film and a metal film as a wiring
material (pure copper film, pure tungsten film, pure aluminum film,
alloy film, etc.) formed in the mentioned order.
[0122] The object to be polished is, for example, an object to be
polished including a buried material, or an object to be polished
including no buried material.
[0123] The object to be polished including a buried material is,
for example, a laminate which comprises a desired material
deposited by CVD or the like so that the desired material is buried
at least in the groove of a substrate which will become a
semiconductor device (which generally comprises at least a wafer
and an insulating film formed on the front surface of the wafer. It
may further comprise a stopper layer as a stopper at the time of
polishing formed on the front surface of the insulating film)
having a groove at least on the front surface. For the polishing of
this object to be polished, after the buried material deposited
excessively is removed by polishing with the polishing pad of the
present invention, the front surface thereof can be polished to be
flattened. When the object to be polished has a stopper layer under
the buried material, the stopper layer may be polished in the
latter stage of polishing at the same time.
[0124] The buried material is, for example, (1) an insulating
material used in the STI step, (2) at least one metal wiring
material selected from Al and Cu used in the damascene process, (3)
at least one via plug material selected from Al, Cu and W used in
the step of forming a via plug, or (4) an insulating material used
in the step of forming an interlayer insulating film.
[0125] The stopper material for forming the above stopper layer is
a nitride-based material such as Si.sub.3N.sub.4, TaN or TiN, or a
metal-based material such as tantalum, titanium or tungsten.
[0126] Examples of the above insulating material include a silicon
oxide (SiO.sub.2) film, boron phosphorus silicate film (BPSG film)
obtained by adding small amounts of boron and phosphorus to
SiO.sub.2, insulating film called "FSG (Fluorine doped silicate
glass)" obtained by doping SiO.sub.2 with fluorine, and silicon
oxide-based insulating film having a low dielectric constant.
[0127] Examples of the silicon oxide film include a thermal oxide
film, PETEOS film (Plasma Enhanced-TEOS film), HDP film (High
Density Plasma Enhanced-TEOS film) and silicon oxide film obtained
by thermal CVD.
[0128] The above thermal oxide film can be formed by exposing
silicon heated at high temperature to an oxidative atmosphere to
cause a chemical reaction between silicon and oxygen or between
silicon and water.
[0129] The above PETEOS film can be formed by the chemical vapor
deposition of tetraethyl orthosilicate (TEOS) using plasma as a
promoting condition.
[0130] The above HDP film can be formed by the chemical vapor
deposition of tetraethyl orthosilicate (TEOS) using high-density
plasma as a promoting condition.
[0131] The above silicon oxide film obtained by thermal CVD can be
obtained by atmospheric CVD (AP-CVD) or low-pressure. CVD
(LP-CVD).
[0132] The above boron phosphorus silicate film (BPSG film) can be
obtained by atmospheric CVD (AP-CVD) or low-pressure CVD
(LP-CVD).
[0133] The above insulating film called "FSG" can be formed by
chemical vapor deposition using high-density plasma as a promoting
condition.
[0134] Further, the above silicon oxide-based insulating film
having a low dielectric constant can be obtained by applying a raw
material to a substrate by rotational coating and heating it in an
oxidative atmosphere, as exemplified by an HSQ film (Hydrogen
Silsesquioxane film) obtained from triethoxysilane, and MSQ film
(Methyl Silsesquioxane film) obtained from tetraethoxysilane and
methyl trimethoxysilane as a part of raw material.
[0135] Other insulating films having a low dielectric constant
include films obtained from an organic polymer such as
polyarylene-based polymer, polyarylene ether-based polymer,
polyimide-based polymer or benzocyclobutene polymer.
[0136] This flush type laminate is shown in FIG. 11. That is, the
laminated substrate 9 comprises a substrate 91 made of silicon or
the like, an insulating film 92 made of silicon oxide or the like
formed on the silicon substrate 91, an insulating film 93 made of
silicon nitride or the like formed on the insulating film 92, an
insulating film 94 made of PTEOS (material synthesized from
tetraethoxysilane by CVD) formed on the insulating film 93 to form
a groove, a barrier metal film 95 made of tantalum or the like
formed to cover the insulating film 94 and the groove, and a film
96 (groove is formed on the surface which is uneven) made of a
wiring material such as metal copper formed on the above barrier
metal film 95 to fill the groove.
[0137] The object to be polished including no buried material is a
substrate made of polysilicon or bare silicon.
EXAMPLES
[0138] Example 1
[0139] 1. Manufacture of Polishing Pad
[0140] 1-1. Production of Surface Treated .beta.-cyclodextrin
[0141] 100 parts by weight of .beta.-cyclodextrin (manufactured by
Yokohama International Bio Research Laboratory Co., Ltd., trade
name of Dexy Pearl .beta.-100, average particle diameter of 20
.mu.m) as water-soluble particles was fed to a mixer (Super Mixer
SMZ-3SP of Kawata Co., Ltd.), 0.5 part by weight of
.gamma.-aminopropyltriethoxysilane (manufactured by Nippon Unica
Co., Ltd., trade name of A-1100) was sprayed on the water-soluble
particles for 5 minutes under agitation at 400 rpm, and the coated
water-soluble particles were further stirred at 400 rpm for 2
minutes. Thereafter, the extracted particles were dried by heating
in a vacuum drier set at 130.degree. C. until the water content
became 5,000 ppm or less to obtain surface treated
.beta.-cyclodextrin.
[0142] 1-2. Manufacture of Polishing Pad Having an Elliptic
Hole
[0143] 66.5 vol % of 1,2-polybutadiene (manufactured by JSR
Corporation, trade name of JSR RB830) and 28.5 vol % of polystyrene
(manufactured by PS Japan Co., Ltd., trade name of HF-55) both of
which would be crosslinked to become a matrix material and 5 vol %
of the above surface treated .beta.-cyclodextrin produced above as
the water-soluble substance were kneaded together by an extruder
heated at 160.degree. C. Thereafter, Percumyl D40 (trade name,
manufactured by NOF Corporation, containing 40% by mass of dicumyl
peroxide) was added in an amount of 0.4 part by mass (equivalent to
0.16 part by mass in terms of pure dicumyl peroxide) based on 100
parts by mass of the total of 1,2-polybutadiene and polystyrene and
further kneaded with the above kneaded product to carry out a
crosslinking reaction at 160.degree. C. in a press metal mold for 7
minutes so as to obtain a disk-like molded product having a
diameter of 790 mm and a thickness of 3.2 mm. An elliptic hole
(aspect ratio of 2.64) having a long diameter of 58 mm and a short
diameter of 22 mm was formed at a position 195 mm away from the
center of the pre-polishing substrate as the center thereof by an
end mill of Kato Machinery Co., Ltd. in such a manner that the long
diameter direction became the diameter direction of the polishing
substrate to manufacture a polishing substrate having an elliptic
hole.
[0144] 1-3. Preparation of Light-Transmitting Member
Composition
[0145] 98 volt of 1,2-polybutadiene (trade name of JSR RB830) which
would be crosslinked to become a light-transmitting member and 2
volt of the surface treated .beta.-cyclodextrin produced in the
above paragraph 1-1 as the water-soluble substance were kneaded
together by an extruder heated at 160.degree. C. Thereafter,
Percumyl D40 was added in an amount of 0.4 part by mass (equivalent
to 0.16 part by mass in terms of pure dicumyl peroxide) based on
100 parts by mass of 1,2-polybuatdiene and further kneaded with the
above kneaded product to produce a light-transmitting member
composition.
[0146] 1-4. Manufacture of Polishing Pad
[0147] Thereafter, the above manufactured polishing substrate was
set in a press metal mold again, the above light-transmitting
member composition was filled into the formed elliptic hole to be
crosslinked at 180.degree. C. for 8 minutes to be molded into a
disk-like molded product having a diameter of 790 mm and a
thickness of 3.2 mm. This molded product was set in the insertion
port of a wide belt sander (of Meinan Machinery Works, Inc.), and
the roller was turned at 500 rpm to grind the front surface and the
rear surface of the molded product by 0.08 mm (total amount of
grinding of 0.32 mm) for each grit size with sandpapers having grit
sizes of 120, 150, 220 and 320 (of Novatec Co., Ltd.) by moving it
at 0.1 m/sec. Thereafter, only the rear surface was ground with a
sandpaper having a grit size of 600 (of Novatec Co., Ltd.) at the
same roller revolution and molded product moving speed as above to
remove 0.06 mm in total. Further, concentric grooves having a width
of 0.5 mm, a pitch of 2 mm and a depth of 1 mm (having a
rectangular sectional form) were formed on the polishing side in
portions 20 mm away from the center of the polishing surface of the
pad by a groove processing machine manufactured by Kato Machinery
Co., Ltd. to manufacture a polishing pad.
[0148] The thickness of the obtained pad was 2.5 mm. When the
arithmetic surface roughness of the rear surface of the
light-transmitting member was measured with the 1LM21P of Laser
Tech Co., Ltd., it was 2.2 .mu.m and the arithmetic surface
roughness of the inner wall of each of the grooves was 6.2 .mu.m.
When part of the light-transmitting member of a polishing pad
manufactured in the same manner as described above was set in a
quartz cell together with water and the transmittance of the
light-transmitting member at a wavelength of 650 nm was measured
with a UV absorptiometer (manufactured by Hitachi Ltd., type of
U-2010), the average integrated transmittance of 5 measurement data
was 25%.
[0149] 2. Test on Polishing Efficiency
[0150] 2-1. Polishing Test on Wafer having a Pattern
[0151] The #422 adhesive double-coated tape of 3M Limited was
laminated on the rear surface of the above manufactured polishing
pad and set in the Applied Reflexion chemical mechanical polishing
machine of Applied Material Co., Ltd. to carry out the chemical
mechanical polishing of a 12-inch wafer having a pattern (trade
name of SEMATECH-754) as an object to be polished under the
following conditions.
[0152] Revolution of platen: 120 rpm
[0153] Revolution of polishing head: 36 rpm
[0154] Polishing pressure:
[0155] Pressure of retainer ring: 7.5 psi
[0156] Pressure of zone 1: 6.0 psi
[0157] Pressure of zone 2: 3.0 psi
[0158] Pressure of zone 3: 3.5 psi
[0159] Aqueous dispersion for chemical mechanical polishing: a
mixture of CMS7401 and CMS7452 (trade names, manufactured by JSR
Corporation) and water in a weight ratio of 1:1:2) Supply rate of
aqueous dispersion for chemical mechanical polishing: 300
ml/min
[0160] In the above polishing, end-point detection was carried out
without a problem. When the number of scratches on the polished
surface of the object after polishing was measured with the Surf
Scan SP1 of KLA Ten Call Co., Ltd., it was "0" on the entire
surface of the wafer.
[0161] 2-2. Test on the Polishing of wafer having a Copper Film and
no Pattern
[0162] A 12-inch diameter wafer having a copper film and no pattern
was polished as an object to be polished with a polishing pad
manufactured in the same manner as in "1. manufacture of chemical
mechanical polishing pad" for 1 minutes to carry out chemical
mechanical polishing in the same manner as in "12-1. polishing test
on wafer having a pattern".
[0163] The thickness of the copper film before and after polishing
was measured at 33 points equally away from one another excluding 5
mm areas from the both ends in the diameter direction of the
object, and the polishing rate and the in-plane uniformity were
calculated from the measurement results based on the following
equations.
Amount of polishing=thickness of copper film before
polishing-thickness of copper film after polishing Polishing
rate=average value of film thickness.div.polishing time In-plane
uniformity=(standard deviation of amount of polishing.div.average
value of amount of polishing).times.100 (%)
[0164] As a result, the polishing rate was 8,550 .ANG./min and the
in-plane uniformity was 3.0%. When the value of in-plane uniformity
is 5% or less, it can be said that the in-plane uniformity is
satisfactory.
Examples 2
[0165] Manufacture of Polishing Pad
[0166] 64 volt of 1,2-polybutadiene (manufactured by JSR
Corporation, trade name of JSR RB830) and 16 volt of a
styrene-butadiene elastomer (manufactured by JSR Corporation, trade
name of JSR TR2827) both of which would be crosslinked to become a
matrix material and 20 volt of the surface treated
.beta.-cyclodextrin produced in "1-1." of Example 1 as a
water-soluble substance were kneaded together by an extruder heated
at 160.degree. C. Thereafter, Percumyl D40 (trade name,
manufactured by NOF Corporation, containing 40% by mass of dicumyl
peroxide) was added in an amount of 0.4 part by mass (equivalent to
0.16 part by mass in terms of pure dicumyl peroxide) based on 100
parts by mass of the total of 1,2-polybutadiene and
styrene-butadiene elastomer and further kneaded with the above
kneaded product to carry out a crosslinking reaction at 160.degree.
C. in a press metal mold for 7 minutes to obtain a disk-like molded
product having a diameter of 790 mm and a thickness of 3.2 mm. An
elliptic hole (aspect ratio of 1.04) having a long diameter of 50
mm and a short diameter of 48 mm was formed at a position 195 mm
away from the center of the pre-polishing substrate as the center
thereof by an end mill of Kato Machinery Co., Ltd. in such a manner
that the long diameter direction became the diameter direction of
the polishing substrate to manufacture a polishing substrate having
an elliptic hole.
[0167] A polishing pad was manufactured in the same manner as in
Example 1 except that the above produced polishing substrate was
used as the polishing substrate having an elliptic hole.
[0168] Test on Polishing Efficiency
[0169] A polishing test was made in the same as in "2. test on
polishing efficiency" of Example 1 except that the above produced
polishing pad was used. The results are shown in Table 1.
Examples 3
[0170] Manufacture of Polishing Pad
[0171] 80 volt of 1,2-polybutadiene (manufactured by JSR
Corporation, trade name of JSR RB830) which would be crosslinked to
become a matrix material and 20 volt of the surface treated
.beta.-cyclodextrin produced in "1-1." of Example 1 as a
water-soluble substance were kneaded together by an extruder heated
at 160.degree. C. Thereafter, Percumyl D40 was added in an amount
of 0.8 part by mass (equivalent to 0.32 part by mass in terms of
pure dicumyl peroxide) based on 100 parts by mass of
1,2-polybutadiene and further kneaded with the above kneaded
product to carry out a crosslinking reaction at 160.degree. C. in a
press metal mold for 7 minutes to obtain a disk-like molded product
having a diameter of 790 mm and a thickness of 3.2 mm. An elliptic
hole (aspect ratio of 10) having a long diameter of 70 mm and a
short diameter of 7 mm was formed at a position 195 mm away from
the center of the pre-polishing substrate as the center thereof by
an end mill of Kato Machinery Co., Ltd. in such a manner that the
long diameter direction became the diameter direction of the
polishing substrate to manufacture a polishing substrate having an
elliptic hole.
[0172] A polishing pad was manufactured in the same manner as in
Example 1 except that the above produced polishing substrate was
used as the polishing substrate having an elliptic hole.
[0173] Test on Polishing Efficiency
[0174] A polishing test was made in the same as in"2. test on
polishing efficiency" of Example 1 except that the above produced
polishing pad was used. The results are shown in Table 1.
Example 4
[0175] Manufacture of Polishing Pad
[0176] (1) manufacture of light-transmitting member 100 parts by
weight of a prepolymer (manufactured by Uni Royal Chemical Co.,
Ltd., trade name of Vibrasene B670) was fed to a vessel and stirred
at 80.degree. C., and 3 parts by weight of the surface treated
.beta.-cyclodextrin produced in"1-1." of Example 1 and further 10.8
parts by weight of trimethylolpropane were added and stirred for 3
minutes. The above mixture was injected into a metal mold having a
rectangular cavity measuring 180 mm.times.180 mm.times.3 mm and
maintained at 110.degree. C. for 30 minutes to carry out a
reaction, and the obtained molded product was removed from the
mold. This molded product was punched by an elliptic puncher to
obtain a light-transmitting member (aspect ratio of 20) having a
long diameter of 120 mm, a short diameter of 6 mm and a thickness
of 3 mm.
[0177] (2) Preparation of Polishing Substrate Composition
[0178] 58 parts by weight of 4,4'-diphenylmethane diusocyanate
(manufactured by Sumika Bayer Urethane Co., Ltd., trade name of
Sumijule 44S) was fed into a reactor and stirred at 60.degree. C.,
and 5.1 parts by weight of polytetramethylene glycol having a
number average molecular weight of 650 and two hydroxyl groups at
both terminals of the molecule (manufactured by Mitsubishi Chemical
Corporation, trade name of PTMG650) and 17.3 parts by weight of
polytetramethylene glycol having a number average molecular weight
of 250 (manufactured by Mitsubishi Chemical Corporation, trade name
of PTMG250) were added and maintained at 90.degree. C. for 2 hours
under agitation to carry out a reaction and then cooled to obtain
an isocyanate-terminated prepolymer. This isocyanate-terminated
prepolymer contained 21 wt % of unreacted 4,4'-diphenylmethane
diisocyanate and the remaining 79 wt % was a mixture of an
isocyanate both-terminated prepolymer.
[0179] 80.4 parts by weight of the obtained isocyanate-terminated
prepolymer was placed in a stirring vessel and maintained at
90.degree. C. and stirred at 200 rpm, and 14.5 parts by weight of
the above obtained water-soluble particles surface treated with a
silane coupling agent was added, mixed, dispersed into the
prepolymer for 1 hour and defoamed under reduced pressure to obtain
an isocyanate-terminated prepolymer containing the water-soluble
particles dispersed therein.
[0180] 12.6 parts by weight of 1,4-bis(.beta.-hydroxyethoxy)benzene
having two hydroxyl groups at a terminal (manufactured by Mitsui
Chemical Fine Co., Ltd., trade name of BHEB) was heated at
120.degree. C. in a stirring vessel for 2 hours to be molten, and 7
parts by weight of trimethylolpropane having three hydroxyl groups
(manufactured by BASF Japan Co., Ltd., trade name of TMP) was added
under agitation and mixed for 10 minutes to be dissolved in the
above substance so as to obtain a mixture of chain extenders.
[0181] 94.9 parts by weight of the above obtained
isocyanate-terminated prepolymer containing water-soluble particles
dispersed therein was heated at 90.degree. C. and stirred in an
agitator mixer, and 19.6 parts by weight of the above obtained
mixture of chain extenders heated at 120.degree. C. was added and
mixed for 1 minute to obtain a polishing substrate composition.
[0182] (3) Manufacture of Polishing Pad
[0183] The light-transmitting member obtained in (2) above was
placed in a metal mold having a disk-like cavity having a diameter
of 600 mm and a thickness of 3 mm at a position 100 mm away from
the center of the disk as the center thereof in such a manner that
the long diameter direction of the ellipse became the diameter
direction of the disk. Thereafter, the polishing substrate
composition produced in (3) above was injected to fill the
remaining cavity in the mold and maintained at 110.degree. C. for
30 minutes to carry out a polyurethanation reaction, and the
obtained molded product was removed from the mold. Further, the
molded product was post-cured in a gear oven set at 110.degree. C.
for 16 hours to obtain a polyurethane sheet having a diameter of
600 mm and a thickness of 3 mm and an elliptic window and
containing water-soluble particles dispersed therein.
[0184] Thereafter, grinding with sandpapers and the formation of
concentric grooves were carried out in the same manner as in "1-4.
manufacture of polishing pad" of Example 1 to manufacture a
polishing pad. The obtained pad had a thickness of 2.3 mm.
[0185] Test on Polishing Efficiency
[0186] A polishing test was made in the same manner as in "2. test
on polishing efficiency" of Example 1 except that the above
produced polishing pad was used. The results are shown in Table
1.
Example 5
[0187] A polishing pad was manufactured in the same manner as
in"1-4. manufacture of polishing pads of Example 1 except that a
metal mold having a projection with the same planar shape and size
as those of the elliptic hole of the polishing substrate and a
height of 0.78 mm at a position corresponding to the elliptic hole
of the polishing pad was used. The rear surface of the
light-transmitting area of this polishing pad was depressed by 0.7
mm from the rear surface of the polishing substrate.
[0188] A polishing test was carried out in the same manner as in"2.
test on polishing efficiency" of Example 1 except that this
polishing pad was used. The results are shown in Table 1.
Comparative Example 1
[0189] Manufacture of Polishing Pad
[0190] A polishing substrate having an elliptic hole was
manufactured in the same manner as in"1-2. manufacture of polishing
substrate having an elliptic hole" of Example 1.
[0191] Separately, a light-transmitting member composition produced
in the same manner as in n1-3. preparation of light-transmitting
member composition" of Example 1 was heated at 180.degree. C. for
10 minutes to be molded, and a hole having the same shape as the
above elliptic hole but smaller than the hole was cut out to
produce a light-transmitting portion. When the transmittance of the
light-transmitting portion was measured in the same manner as in
Example 1, the average integrated transmittance of five measurement
data was 25%.
[0192] After the #422 adhesive both-coated tape of 3M Limited was
laminated on the entire rear surface of the above polishing
substrate, the above produced light-transmitting portion was
inserted into the hole of the polishing substrate to manufacture a
polishing pad.
[0193] Test on Polishing Efficiency
[0194] A polishing test was made in the same manner as in"2. test
on polishing efficiency" of Example 1 except that the above
produced polishing pad was used. The results are shown in Table
1.
1 TABLE 1 polishing test on wafer Polishing test on water having a
copper film having a pattern and no pattern number of polishing
in-plane End-point scratches rate uniformity detection (per wafer)
(.ANG./min) (%) Example 1 Possible 0 8550 3.0 Example 2 Possible 0
8100 2.8 Example 3 Possible 10 8500 3.0 Example 4 Possible 20 7100
1.8 Example 5 Possible 0 8550 3.0 Comparative Possible 400 8400 2.5
Example 1
* * * * *