U.S. patent application number 10/820123 was filed with the patent office on 2004-10-14 for abrasive pad, method and metal mold for manufacturing the same, and semiconductor wafer polishing method.
This patent application is currently assigned to JSR Corporation. Invention is credited to Hasegawa, Kou, Hosaka, Yukio, Kawahashi, Nobuo, Shiho, Hiroshi.
Application Number | 20040203320 10/820123 |
Document ID | / |
Family ID | 32866756 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040203320 |
Kind Code |
A1 |
Hosaka, Yukio ; et
al. |
October 14, 2004 |
Abrasive pad, method and metal mold for manufacturing the same, and
semiconductor wafer polishing method
Abstract
An abrasive pad capable of transmitting light for end point
detection without reducing polishing efficiency in the polishing of
a semiconductor wafer using an optical end-point detection device,
method of manufacturing the abrasive pad, a metal mold for
manufacturing the abrasive pad, and a method of polishing a
semiconductor wafer. This abrasive pad comprises an abrasive
substrate and a light transmitting member. The light transmitting
member comprises a crosslinked polymer such as crosslinked
1,2-polybutadiene and a water-soluble substance such as
.beta.-cyclodextrin dispersed in the crosslinked polymer. Since the
light transmitting member and the abrasive substrate are fused
together as an integrated unit, slurry does not leak to the rear
side of the abrasive pad during the abrasive pad used. This
manufacturing method comprises setting the light transmitting
member in the metal mold for insert molding and crosslinking a
matrix dispersion for forming the abrasive substrate in this mold.
The polishing method using this abrasive pad employs an optical
end-point detection device.
Inventors: |
Hosaka, Yukio; (Tokyo,
JP) ; Shiho, Hiroshi; (Tokyo, JP) ; Hasegawa,
Kou; (Tokyo, JP) ; Kawahashi, Nobuo; (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: |
32866756 |
Appl. No.: |
10/820123 |
Filed: |
April 8, 2004 |
Current U.S.
Class: |
451/6 ;
451/41 |
Current CPC
Class: |
B24D 18/0009 20130101;
B24B 37/205 20130101 |
Class at
Publication: |
451/006 ;
451/041 |
International
Class: |
B24B 049/00; B24B
051/00; B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2003 |
JP |
2003-105924 |
Claims
What is claimed is:
1. An abrasive pad comprising an abrasive substrate having a
polishing surface and a light transmitting member which is fused to
the abrasive substrate and comprises a water-insoluble matrix
material and a water-soluble substance dispersed in the
water-insoluble matrix material.
2. The abrasive pad of claim 1, wherein at least part of the
water-insoluble matrix material is a crosslinked polymer.
3. The abrasive pad of claim 2, wherein the crosslinked polymer is
crosslinked 1,2-polybutadiene.
4. The abrasive pad of claim 1, wherein the light transmitting
member is made thin in a direction perpendicular to the polishing
surface of the abrasive substrate.
5. The abrasive pad of claim 1, wherein the materials of the light
transmitting material and the abrasive substrate differ from each
other in type and/or ratio.
6. The abrasive pad of claim 1 which has a fixing layer for fixing
the abrasive pad on a polishing machine, which is formed on the
rear surface opposite to the polishing surface of the abrasive
pad.
7. A method of manufacturing the abrasive pad of claim 1,
comprising holding a previously formed light transmitting member
for an abrasive pad at a predetermined position in the cavity of a
metal mold for insert molding and injecting the material of an
abrasive substrate into the remaining space in the cavity to fuse
the light transmitting member to the abrasive substrate.
8. A method of manufacturing the polishing pad of claim 1,
comprising holding a previously formed abrasive substrate having a
hole for accepting a light transmitting member in the cavity of a
metal mold for insert molding and injecting the material of the
light transmitting member into the hole for accepting the light
transmitting member to fuse the abrasive substrate to the light
transmitting member.
9. A metal mold for insert molding for the manufacture of the
abrasive pad of claim 1, which has a projection portion(s) and/or a
depressed portion(s) for holding a light transmitting member or an
abrasive substrate for an abrasive pad in a cavity.
10. An abrasive laminated pad comprising the abrasive pad of claim
1 and a base layer having light transmission properties formed on
the rear surface opposite to the polishing surface of the abrasive
pad.
11. An abrasive laminated pad comprising the abrasive pad of claim
1, a base layer formed on the rear surface opposite to the
polishing surface of the abrasive pad, and a fixing layer for
fixing the pad on a polishing machine, formed on the side opposite
to the abrasive pad of the base layer.
12. A method of polishing a semiconductor wafer with an abrasive
pad, characterized in that the abrasive pad of claim 1 or the
abrasive laminated pad of claim 10 or 11 is used, and the polishing
end point of the semiconductor wafer is detected by an optical
end-point detection device through the light transmitting member of
the abrasive pad or the abrasive laminated pad.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an abrasive pad, a method
and a metal mold for manufacturing the same, and a semiconductor
wafer polishing method.
[0002] More specifically, it relates to an abrasive pad which can
transmit light without reducing polishing efficiency, a method of
manufacturing the abrasive pad, a metal mold for manufacturing the
abrasive pad, an abrasive laminated pad which can transmit light,
and a semiconductor wafer polishing method.
[0003] The present invention is used to polish a semiconductor
wafer, making use of an optical end-point detection device.
DESCRIPTION OF THE PRIOR ART
[0004] In the polishing of a semiconductor wafer, after the purpose
of polishing is accomplished, the decision of the polishing end
point for terminating polishing can be made based on a time
obtained empirically. However, various materials are used to form
surfaces to be polished and 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 empirically the
each polishing time from the various polishings. To cope with this,
research into optical end-point detection device and process using
an optical method capable of directly observing the state of the
surface to be polished is now under way (JP-A 9-7985,
JP-A2000-326220 and JP-A11-512977) (the term "JP-A" as used herein
means an "unexamined published Japanese patent application").
[0005] In the optical end-point detection device and process, a
window which is made from a hard and homogeneous resin capable of
transmitting light for end-point detection and has substantially no
ability to absorb and carry a slurry substance is generally formed
in an abrasive pad, and the surface to be polished is observed only
from this window (JP-A 11-512977).
[0006] However, since the window has substantially no ability to
hold and discharge slurry in the above abrasive pad, it is
apprehended that the polishing efficiency of the abrasive pad may
be reduced or become nonuniform by forming the window. Therefore,
it is difficult to form a large ring window or to increase the
number of windows.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention which has solved
the above problem to provide an abrasive pad which can transmit
light for end-point detection without reducing polishing efficiency
in the polishing of a semiconductor wafer, a method of
manufacturing the abrasive pad, a metal mold for manufacturing the
abrasive pad, an abrasive laminated pad, and a semiconductor wafer
polishing method.
[0008] Other objects and advantages of the present invention will
become apparent from the following description.
[0009] The inventors of the present invention have studied an
abrasive pad used for polishing, making use of an optical end-point
detection device, and have found that when a light transmitting
member having light transmission properties is used as a window in
place of a prior art window made from a hard and homogeneous resin
which has no ability to hold and discharge slurry, satisfactory
light transmission properties can be ensured and further that the
polishing end point can be detected. They have also found that when
a water-soluble substance is dispersed and contained in the matrix
material of the window, the window is provided with the ability to
hold and discharge slurry at the time of polishing. Further, they
have discovered that slurry does not leak from the polishing
surface when an abrasive substrate and a light transmitting member
are fused and fixed together.
[0010] That is, according to the present invention, firstly, the
above objects and advantages of the present invention are attained
by an abrasive pad comprising an abrasive substrate having a
polishing surface and a light transmitting member which is fused to
the abrasive substrate and comprises a water-insoluble matrix
material and a water-soluble substance dispersed in the
water-insoluble matrix material.
[0011] According to the present invention, secondly, the above
objects and advantages of the present invention are attained by a
method of manufacturing the abrasive pad of the present invention,
comprising holding a previously formed light transmitting member
for an abrasive pad at a predetermined position in the cavity of a
metal mold for insert molding and injecting the material of an
abrasive substrate into the remaining space in the cavity to fuse
the light transmitting member to the abrasive substrate.
[0012] According to the present invention, thirdly, the above
objects and advantages of the present invention are attained by a
method of manufacturing the abrasive pad of the present invention,
comprising holding a previously formed abrasive substrate having a
hole for accepting a light transmitting member in the cavity of a
metal mold for insert molding and injecting the material of the
light transmitting member into the hole for accepting the light
transmitting member to fuse the abrasive substrate to the light
transmitting member.
[0013] According to the present invention, in the fourth place, the
above objects and advantages of the present invention are attained
by a metal mold for insert molding for the manufacture of the
abrasive pad of the present invention, which has a projection
portion(s) and/or a depressed portion(s) for holding a light
transmitting member or an abrasive substrate for an abrasive pad in
a cavity.
[0014] According to the present invention, in the fifth place, the
above objects and advantages of the present invention are attained
by an abrasive laminated pad comprising the abrasive pad of the
present invention and a base layer having light transmission
properties formed on the rear surface opposite to the polishing
surface of the abrasive pad.
[0015] According to the present invention, in the sixth place, the
above objects and advantages of the present invention are attained
by an abrasive laminated pad comprising the abrasive pad of the
present invention, a base layer formed on the rear surface opposite
to the polishing surface of the abrasive pad, and a fixing layer
for fixing the pad on a polishing machine, formed on the side
opposite to the abrasive pad of the base layer.
[0016] According to the present invention, finally, the above
objects and advantages of the present invention are attained by a
method of polishing a semiconductor wafer with an abrasive pad,
characterized in that the abrasive pad or the abrasive laminated
pad of the present invention is used, and the polishing end point
of the semiconductor wafer is detected by an optical end-point
detection device through the light transmitting member of the
abrasive pad or the abrasive laminated pad.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0018] FIG. 2 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0019] FIG. 3 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0020] FIG. 4 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0021] FIG. 5 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0022] FIG. 6 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0023] FIG. 7 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0024] FIG. 8 is a schematic diagram showing the shapes and fusion
state of an abrasive substrate and a light transmitting member;
[0025] FIG. 9 is a plan view of an example of the abrasive pad of
the present invention;
[0026] FIG. 10 is a plan view of another example of the abrasive
pad of the present invention;
[0027] FIG. 11 is a plan view of still another example of the
abrasive pad of the present invention;
[0028] FIG. 12 is a partial sectional view of a metal mold for
molding the abrasive pad of the present invention;
[0029] FIG. 13 is a sectional view showing that a light
transmitting member is fixed in a metal mold for molding an
abrasive pad;
[0030] FIG. 14 is a sectional view showing that an abrasive
substrate dispersion is injected into a metal mold for molding an
abrasive pad, having a light transmitting member fixed therein;
[0031] FIG. 15 is a sectional view of the abrasive pad of the
present invention;
[0032] FIG. 16 is a partial sectional view of a metal mold having a
projection portion of the present invention;
[0033] FIG. 17 is a sectional view showing that an abrasive
substrate is fixed in a metal mold for molding an abrasive pad,
having a projection portion;
[0034] FIG. 18 is a sectional view showing that a light
transmitting member dispersion is injected into a metal mold for
molding an abrasive pad, having an abrasive substrate fixed
therein;
[0035] FIG. 19 is a partial sectional view of a metal mold having a
depressed portion;
[0036] FIG. 20 is a sectional view showing that an abrasive
substrate dispersion is injected into a metal mold for molding an
abrasive pad, having a light transmitting member fixed therein;
[0037] FIG. 21 is a diagram of the abrasive pad of the present
invention;
[0038] FIG. 22 is a diagram of an abrasive pad having fixing
layers;
[0039] FIG. 23 is a diagram of an abrasive pad having a base
layer;
[0040] FIG. 24 is a diagram of an abrasive pad having a base layer
and fixing layers;
[0041] FIG. 25 is a diagram for explaining a polishing method using
the abrasive pad or abrasive laminated pad of the present
invention; and
[0042] FIG. 26 is a sectional view of a material to be polished
suitably by the polishing method of the present invention.
[0043] FIG. 27 is a diagram for showing a position of a through
hole formed to an abrasive pad substrate in Examples 4 to 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] The present invention will be described in detail
hereinunder.
[0045] Abrasive Pad
[0046] The abrasive pad of the present invention comprises an
abrasive substrate and a light transmitting member.
[0047] Abrasive Substrate
[0048] The abrasive substrate can hold slurry on the surface and
can retain the residual dust after polishing temporarily. It
doesn't matter whether this abrasive substrate has light
transmission properties or not. The planar shape of the abrasive
substrate is not particularly limited and may be circular or
polygonal (quadrilateral, etc.). The size of the abrasive substrate
is not particularly limited as well.
[0049] Preferably, slurry can be held during polishing and the
residual dust can be retained temporarily on the surface of this
abrasive substrate. Therefore, the abrasive substrate may have at
least one member selected from minute holes (to be referred to as
"pores" hereinafter), grooves and fluff formed by dressing. They
may be formed in advance or formed at the time of polishing. That
is, the abrasive substrate is selected from (1) an abrasive
substrate which comprises a water-insoluble matrix material and a
water-soluble substance dispersed in the water-insoluble matrix
material, (2) an abrasive substrate (foamed material) which
comprises a water-insoluble matrix material and pores dispersed in
the water-insoluble matrix material, and (3) an abrasive substrate
which consists only of a water-insoluble matrix (non-foamed
material) and can be fluffed by dressing.
[0050] The material of the water-insoluble matrix in the above
abrasive substrates (1) to (3) is not particularly limited and
various materials may be used. It is preferably an organic material
because it can be easily molded to have a predetermined shape or
properties and can be provided with suitable elasticity. As the
organic material may be used various materials which are suitably
used as the matrix material of the abrasive substrate to be
described hereinafter.
[0051] The materials for forming the abrasive substrate may be the
same or different in type from the materials for forming the light
transmitting member. An abrasive substrate made from materials
different in type from the materials for forming the light
transmitting member or an abrasive substrate made from materials
which are the same in type but different in ratio from the
materials for forming the light transmitting member is preferably
used.
[0052] To prevent the light transmitting member from projecting or
depressing at the time of polishing, it is preferred that the
abrasion resistance of the abrasive substrate should not greatly
differ from that of the light transmitting member.
[0053] As the above "water-insoluble matrix material" (may also
simply referred to as "matrix material" hereinafter), a
thermoplastic resin, thermosetting resin, elastomer and rubber are
preferably used alone or in combination.
[0054] Examples of the above thermoplastic resin include polyolefin
resin, polystyrene resin, polyacrylic resin such as {(meth)acrylate
resin}, vinyl ester resin (excluding acrylic resin), polyester
resin, polyamide resin, fluororesin, polycarbonate resin and
polyacetal resin.
[0055] Examples of the above thermosetting resin include phenolic
resin, epoxy resin, unsaturated polyester resin, polyurethane
resin, polyurethane-urea resin, urea resin and silicon resin.
[0056] Examples of the above elastomer include styrene elastomers
such as styrene-butadiene-styrene block copolymer (SBS) and
hydrogenated block copolymer thereof (SEBS); thermoplastic
elastomers such as polyolefin elastomer (TPO), thermoplastic
polyurethane elastomer (TPU), thermoplastic polyester elastomer
(TPEE), polyamide elastomer (TPAE) and diene elastomer (such as
1,2-polybutadiene); silicone resin elastomer and fluororesin
elastomer.
[0057] Examples of the above rubber include butadiene rubber,
styrene.cndot.butadiene rubber, isoprene rubber,
isobutylene.cndot.isopre- ne rubber, acrylic rubber,
acrylonitrile.cndot.butadiene rubber, ethylene propylene rubber,
ethylene.cndot.propylene.cndot.diene rubber, silicone rubber and
fluorine rubber.
[0058] The matrix material may be a crosslinked polymer or
noncrosslinked 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.
[0059] 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 abrasive 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 abrasive 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.
[0060] Examples of the above crosslinked polymer include polymers
obtained by crosslinking resins such as polyurethane resin, epoxy
resin, polyacrylic resin, unsaturated polyester resin and vinyl
ester resin (excluding polyacrylic resin), diene-based elastomer
(1,2-polybutadiene), butadiene rubber, isoprene rubber, acrylic
rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber,
ethylene-propylene rubber, silicone rubber, fluorine rubber and
styrene-isoprene rubber, out of the above thermoplastic resins,
thermosetting resins, elastomers and rubbers, and polymers obtained
by crosslinking polyethylene or polyvinylidene fluoride in the
presence of a crosslinking agent or through exposure to ultraviolet
radiation or electron beam. Ionomers may also be used.
[0061] These matrix materials may be used in combination of two or
more.
[0062] Further, polymers modified by at least one hydrophilic
functional group such as acid anhydride group, carboxyl group,
hydroxyl group, epoxy group or amino group to improve hydrophilic
nature with slurry may be used as the matrix material.
[0063] Examples of the above matrix material include polymers such
as maleic anhydride modified polyethylene, maleic anhydride
modified polypropylene, polybutadiene having a terminal hydroxyl
group and polybutadiene having a terminal carboxyl group; and
polymers and copolymers obtained by polymerizing a monomer having
the above functional group. Polybutadiene having a terminal
hydroxyl group and polybutadiene having a terminal carboxyl group
are particularly preferred. They may be used alone or in
combination of two or more.
[0064] Further, the matrix material may be a mixture of a polymer
having any one of the above functional groups and a polymer having
none of the above functional groups.
[0065] The above "modification" may be carried out, for example, by
(a) a method in which a polymer is heated in the presence of a
monomer having an acid anhydride group and a peroxide (hydrogen
peroxide, organic peroxide, etc.) to add a side chain having an
acid anhydride structure to a polymer having no acid anhydride
structure in the main chain, or (b) a method in which a polymer is
heated in the presence of a compound having at least two acid
anhydride structures in the molecular and/or a compound having an
acid anhydride structure and a carboxyl group in the molecular and
a catalyst such as an acidic, alkali or metal catalyst to add a
side chain having an acid anhydride structure to a polymer having
no acid anhydride structure in the main chain.
[0066] Examples of the monomer having an acid anhydride structure
used in the method (a) include maleic anhydride, itaconic
anhydride, citraconic anhydride and endomethylenetetrahydrophthalic
anhydride.
[0067] Examples of the compound having at least two acid anhydride
structures in the molecule used in the method (b) include
pyromellitic anhydride and 3,3', 4,4'-benzophenonetetracarboxyilc
dianhydride; and examples of the compound having an acid anhydride
structure and carboxyl group in the molecule include trimellitic
anhydride.
[0068] The member constituting the above abrasive substrate may
further comprise a water-soluble substance.
[0069] This water-soluble substance can form pores for holding
slurry for polishing by separating from the surface of the matrix
material when it contacts water. The average diameter of the pores
formed after the water-soluble substance separates from the
abrasive pad, that is, the average diameter of the water-soluble
substance contained in the matrix before it is eliminated may be
0.1 to 500 .mu.m, preferably 0.5 to 100 .mu.m, more preferably 5 to
50 .mu.m.
[0070] The water-soluble substance includes what can be liberated
when it is gelled by contact to water, such as water absorbing
resins, in addition to water-soluble substances such as
water-soluble polymers. This water-soluble substance may dissolve
or gel in a medium containing water as the main ingredient and
methanol or the like. The water-soluble substance is generally
dispersed in the matrix material.
[0071] The water-soluble substance is often solid but may be
liquid. The solid water-soluble substance is generally particulate
but may be fibrous such as whisker-shaped, other linear-shaped, or
odd-shaped such as tetrapod-shaped. The water-soluble substance is
preferably particulate, more preferably solid particulate so that
it can retain its shape even at a thermal kneading temperature.
[0072] The average particle diameter of the water-soluble particles
may be 0.1 to 500 .mu.m, preferably 0.5 to 100 .mu.m, more
preferably 5 to 50 .mu.m. When this average particle diameter is
smaller than 0.1 .mu.m, the formed pores are small and an abrasive
pad capable of holding abrasive grains completely may not be
obtained. When the average particle diameter is larger than 500
.mu.m, the mechanical strength of the obtained abrasive pad may
lower. The average particle diameter is the average value of
maximum lengths of the water-soluble particles contained in the
matrix.
[0073] The water-soluble substance may be inorganic or organic. Out
of these, it is preferably organic.
[0074] Examples of the organic water-soluble substance include
dextrin, cyclodextrin, mannitol, saccharides such as lactose,
celluloses such as hydroxypropyl cellulose and methyl cellulose,
starch, protein, polyvinyl alcohol, polyvinyl pyrrolidone,
polyvinylsulfonic acid, polyacrylic acid, polyethylene oxide,
water-soluble photosensitive resin and sulfonated polyisoprene.
They may be used alone or in admixture of two or more.
[0075] Examples of the inorganic water-soluble substance include
potassium acetate, potassium nitrate, potassium carbonate,
potassium hydrogencarbonate, potassium bromide, potassium
phosphate, potassium sulfate, magnesium sulfate and calcium
nitrate. They may be used alone or in admixture of two or more.
[0076] The liquid water-soluble substance is not limited to a
particular type but preferably what does not have a bad influence
upon polishing efficiency when it dissolves in slurry during use.
The liquid water-soluble substance includes a water-soluble
substance which is liquid itself and also a water-soluble substance
which is not liquid but solid at normal temperature and dissolves
in water to become an aqueous solution. Examples of the liquid
water-soluble substance include organic acids such as formic acid,
acetic acid, an aqueous solution of tartaric acid, aqueous solution
of succinic acid and aqueous solution of malonic acid, and
oxidizing agents such as aqueous solution of hydrogen peroxide,
aqueous solution of peracetic acid and nitric acid.
[0077] When the water-soluble substance is contained in the
water-insoluble matrix material, it is dispersed in the entire
matrix material. Pores are formed in an abrasive pad comprising the
matrix containing this water-soluble substance by the dissolution
of the water-soluble substance existent on the most surface layer
of the abrasive pad through contact to water. The pores have the
function of holding slurry and retaining the residual dust after
polishing temporarily. The water-soluble substance dissolves or
gels when it contacts slurry which is an aqueous dispersion
contained in the abrasive pad and separates from the matrix
material.
[0078] Preferably, the water-soluble substance dissolves or gels in
water only when it is exposed to the surface layer of the abrasive
pad and does not absorb moisture or gel in the abrasive pad.
Therefore, the water-soluble substance preferably has an outer
shell for suppressing moisture absorption on at least part of its
outer surface. This outer shell may be physically adsorbed to or
chemically bonded to the water-soluble substance, or may be in
contact with the water-soluble substance by physical adsorption or
chemical bonding. Examples of the material forming this outer shell
include epoxy resin, polyimide, polyamide and polysilicate. Even
when this outer shell is formed only on part of the water-soluble
substance, the above effect can be fully obtained.
[0079] This water-soluble substance in the abrasive pad has the
function of increasing the indentation hardness of the abrasive pad
(to 35 to 100 in terms of Shore D hardness) in addition to the
above function of forming pores. As this indentation hardness is
high, pressure applied to the surface to be polished by the
abrasive pad can be increased. Therefore, not only the polishing
rate can be improved but also high polishing flatness can be
obtained. Accordingly, this water-soluble substance is particularly
preferably a solid material which can secure sufficiently high
indentation hardness for the abrasive pad.
[0080] The content of the water-soluble substance in this abrasive
substrate is preferably 90 vol % or less, more preferably 80 vol %
or less, much more preferably 0.1 to 80 vol %, particularly
preferably 1 to 50 vol %, ideally 1 to 30 vol % based on 100 vol %
of the total of the water-insoluble matrix material and the
water-soluble substance. When the content of the water-soluble
substance is higher than 90 vol %, it may be difficult to
completely prevent the water-soluble substance contained in the
matrix material from being gelled or dissolved one after another
and therefore to maintain the hardness and mechanical strength of
the abrasive pad at appropriate values.
[0081] The method of dispersing the above hydrophilic substance and
the water-soluble substance into the matrix material at the time of
production is not particularly limited. For instance, the matrix
material, hydrophilic substance and water-soluble substance 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 hydrophilic substance and the water-soluble
substance are preferably solid.
[0082] When they are solid, the hydrophilic substance is easily
dispersed though it has compatibility with the matrix material and
also the water-soluble substance is easily dispersed while it shows
the above preferred average particle diameter. Therefore, the types
of the hydrophilic substance and the water-soluble substance are
preferably selected according to the processing temperature of the
used matrix material.
[0083] Light Transmitting Member
[0084] The light transmitting member refers to a member for forming
a portion having light transmission properties in part of the
abrasive pad. A description is subsequently given of the light
transmitting member with reference to the accompanying
drawings.
[0085] The shape of this light transmitting member is not
particularly limited. The planar shape of the light transmitting
member on the polishing surface side of the abrasive pad may be
circular, elliptic, triangular, quadrilateral or polygonal. The
sectional form perpendicular to the polishing surface of the light
transmitting member is not particularly limited. Any shape is
acceptable if light can be transmitted between the polishing
surface side and the non-polishing surface side. For example, it
may have sectional forms shown in FIGS. 1 to 8. This light
transmitting member 12 and the abrasive substrate 11 are fused
together as an integrated unit.
[0086] The term "fused" refers to a state in which the light
transmitting member and the abrasive substrate are bonded together
by melting at least the bonding surface(s) of both or one of them
without using an adhesive. For the production of the abrasive pad,
not only the bonding surface but also the entire light transmitting
member may be molten to be bonded, or the entire abrasive substrate
may be molten to be bonded.
[0087] The method of fusing together the light transmitting member
and the abrasive substrate is not particularly limited. For
example, it may be (1) an insert molding method in which one of the
light transmitting member and the abrasive 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 abrasive 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 abrasive
substrate to bond them together.
[0088] Since the light transmitting member and the abrasive
substrate of the abrasive pad of the present invention are fused
together, there is no gap between the light transmitting member and
the abrasive substrate, whereby slurry does not leak to the rear
side of the abrasive pad.
[0089] The thickness of this light transmitting member may not be
smaller than the thickness of the abrasive substrate as shown in
FIGS. 1 and 3, may be smaller than the maximum thickness of the
abrasive substrate as shown in FIGS. 2, 4, 5, 6 and 8, or part of a
light transmitting portion of the light transmitting member may be
smaller in the thickness as shown in FIG. 7.
[0090] To transmit light through the light transmitting member, the
intensity of the light attenuates in proportion to the square of
the thickness of the light transmitting member. Therefore, by
reducing the thickness of the light transmitting member, light
transmission properties can be greatly improved. For example, even
when it is difficult to obtain light having sufficiently high
intensity for the detection of an end point from this light
transmitting member which has the same thickness as other portions
of the abrasive pad used for polishing making use of optical
end-point detection, sufficiently high light intensity can be
ensured for the detection of an end point by reducing the thickness
of the light transmitting member. The thickness of the light
transmitting member which has been made thin is preferably 0.1 mm
or more, more preferably 0.2 mm to 4 mm, much more preferably 0.3
mm to 3 mm. When the thickness is smaller than 0.1 mm, it may be
difficult to secure sufficiently high mechanical strength for the
light transmitting member.
[0091] A depressed portion, where the light transmitting member is
not existent, formed by reducing the thickness of the light
transmitting member (for example, a portion below the light
transmitting member 12 in FIG. 2) or a depressed portion of the
light transmitting member (for example, a portion whose top, right
and left sides are surrounded by the light transmitting member 12
in FIG. 7) may be formed on either one of the front and rear sides
of the abrasive pad. When it is formed on the rear side of the
abrasive pad, the thickness of the light transmitting member can be
reduced without affecting polishing efficiency.
[0092] The number of the light transmitting members is not
particularly limited and may be one or more. The position of the
light transmitting member is not particularly limited. For example,
when the abrasive pad has one light transmitting member, it may be
arranged as shown in the plan views of FIG. 9 and FIG. 10. Further,
when the abrasive pad has two or more light transmitting members,
they may be arranged concentric to one another as shown in the plan
view of FIG. 11.
[0093] 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 to 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.
[0094] In the abrasive pad used for polishing using an optical
end-point detection device, 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, it is preferable that a transmittance at a wavelength
between 400 and 800 nm satisfies the above requirements.
[0095] This transmittance is a value measured at each wavelength
with an UL 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.
[0096] The "water-insoluble matrix material" (may be simply
referred to as "matrix material" hereinafter) for forming 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.
[0097] 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 abrasive substrate. These matrix materials may be
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 abrasive substrate.
[0098] Preferably, these matrix materials contain a hydrophilic
substance having a functional group to improve its compatibility
with the water-soluble substance, abrasive grains, aqueous medium,
etc. as required. What are enumerated for the above abrasive
substrate may be used as the hydrophilic substance.
[0099] These hydrophilic substances may be used in combination of
two or more.
[0100] 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.
[0101] 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 abrasive 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 abrasive 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.
[0102] These crosslinked polymers are the same as those listed for
the above abrasive-substrate.
[0103] Out of these crosslinked polymers, crosslinked
1,2-polybutadiene is particularly preferred because it can provide
sufficiently high light transmission properties, is stable to a
strong acid or strong alkali contained in many kinds of slurry and
further is 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.
[0104] 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. This means that the
matrix material has 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,
much more preferably 5% or less and 0% or more. As the residual
elongation at break is higher than 100%, fine pieces scraped off
from the surface of the abrasive pad or stretched at the time of
polishing or surface renewal tend to fill the pores.
[0105] The term "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.
[0106] The water-soluble substance is dispersed in the light
transmitting member. It is 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.
[0107] The shape, size, content in the light transmitting member
and material of the water-soluble substance are the same as the
water-soluble substance described in detail for the above abrasive
substrate.
[0108] Preferably, the water-soluble substance which is exposed to
the surface of the light transmitting member dissolves or gels in
water and the water-soluble substance which is contained in the
light transmitting member without surfacing does not absorb
moisture or gel in the abrasive pad. 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 substance.
[0109] This water-soluble substance has the function of matching
the indentation hardness of the light transmitting member with that
of other portion of the abrasive pad in addition to the function of
forming pores. The Shore D hardness of the entire abrasive pad is
preferably 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 abrasive pad by containing the water-soluble
substance, besides the formation of pores. For this reason, the
water-soluble substance is preferably a solid material capable of
securing sufficiently high indentation hardness for the abrasive
pad.
[0110] The method of dispersing the above hydrophilic substance and
the water-soluble substance in the matrix material at the time of
production may be the same as the method described for the above
abrasive substrate.
[0111] A compatibilizing agent such as a homopolymer, block
copolymer or random copolymer modified by an acid anhydride group,
carboxyl group, hydroxyl group, epoxy group, oxazoline group or
amino group, which is optionally added at the time of production to
improve compatibility between the matrix material and the
water-soluble substance and the dispersibility in the matrix
material of the water-soluble substance, a nonionic surfactant and
a coupling agent may be contained, in addition to the matrix
material and the water-soluble substance.
[0112] At least one selected from an abrasive grain, oxidizing
agent, polyvalent metal ion, organic acid, hydroxide or acid of an
alkali metal, pH modifier, surfactant and scratch prevention agent
all of which have been contained in slurry may be contained in the
abrasive pad of the present invention, that is, the light
transmitting member and the abrasive pad substrate, in addition to
the matrix material and the water-soluble substance. Thereby, when
this abrasive pad is used, polishing can be carried out by
supplying only water. Further, to the abrasive pad of the present
invention may be optionally added additives such as a filler,
softening agent, antioxidant, ultraviolet light absorber,
antistatic agent, lubricant and plasticizer in limits that do not
impair the effect of the present invention.
[0113] Examples of the above abrasive grain include inorganic
particles such as silica particle, alumina particle, ceria
particle, zirconia particle and titania particle, organic particles
such as polystyrene, and organic/inorganic composite particles such
as polystyrene/silica.
[0114] The above oxidizing agent is not particularly limited if it
is water-soluble. Examples of the oxidizing agent include organic
peroxides such as hydrogen peroxide, peracetic acid, perbenzoic
acid and tert-butyl hydroperoxide, permanganic acid compounds such
as potassium permanganate, bichromic acid compounds such as
potassium bichromate, halogen acid compounds such as potassium
iodate, nitric acid compounds such as nitric acid and iron nitrate,
perhalogen acid compounds such as perchloric acid, transition metal
salts such as potassium ferricyanide, persulfuric acid salts such
as ammonium persulfate, salts of a polyvalent metal such as iron
nitrate and cerium ammonium nitrate, and heteropoly-acids such as
tungstosilicic acid, tungstophosphoric acid, molybdosilicic acid
and molybdophosphoric acid. They may be used alone or in
combination of two or more. Out of these, hydrogen peroxide and
organic peroxides are particularly preferred because they do not
contain any elemental metal and their decomposed products are
harmless. By containing any one of these oxidizing agents, the
polishing rate can be greatly improved when a metal layer such as a
film to be processed of a wafer is polished.
[0115] The content of the oxidizing agent may be 0 to 10 parts by
mass (may be simply referred to as "parts" hereinafter),
particularly preferably 0 to 5 parts by mass based on 100 parts by
mass of the whole pad as far as the effect of the present invention
is not impaired.
[0116] Examples of the above polyvalent metal ion include ions of
metals such as aluminum, titanium, vanadium, chromium, manganese,
iron, cobalt, nickel, copper, zinc, germanium, zirconium,
molybdenum, tin, antimony, tantalum, tungsten, lead and cerium.
They may be used alone or in combination of two or more. The
polyvalent metal ion is preferably an ion of at least one metal
selected from aluminum, titanium, chromium, manganese, iron,
copper, zinc, tin and cerium because a high polishing rate can be
obtained. Out of these, iron ion and copper ion are particularly
preferred. One or more out of nitrates, sulfates, acetates and
gluconates of aluminum, nitrates, sulfates, acetates and gluconates
of iron (III), and nitrates, sulfates, acetates and gluconates of
copper (II) may be used as the metal salt(s) constituting the above
polyvalent metal ion. These iron nitrates (III) also serve as an
oxidizing agent. The content of the polyvalent metal ion in the
whole pad is 0 to 10% by mass, particularly preferably 0 to 5% by
mass.
[0117] The above organic acid can stabilize the above oxidizing
agent and further improve the polishing rate. Preferred examples of
the organic acid include paratoluenesulfonic acid,
dodecylbenzenesulfonic acid, isoprenesulfnoic acid, gluconic acid,
lactic acid, citric acid, tartaric acid, malic acid, glycolic acid,
malonic acid, formic acid, oxalic acid, succinic acid, fumaric
acid, maleic acid and phthalic acid. Out of these, gluconic acid,
lactic acid, citric acid, tartaric acid, malic acid, glycolic acid,
malonic acid, formic acid, oxalic acid, succinic acid, fumaric
acid, maleic acid and phthalic acid are preferred. Particularly
preferred are tartaric acid, malic acid, succinic acid and phthalic
acid. These organic acids may be used alone or in combination of
two or more. The content of the organic acid in the whole pad is
preferably 0 to 10% by mass, particularly preferably 0 to 5% by
mass.
[0118] The above surfactant may be cationic, anionic or nonionic.
Examples of the cationic surfactant include aliphatic amine salts
and aliphatic ammonium salts. Examples of the anionic surfactant
include fatty acid soap, carboxylic acid salts such as alkyl ether
carboxylates, sulfonic acid salts such as alkylbenzenesulfonates,
alkylnaphthalenesulfonates and .alpha.-olefinsulfonates, sulfuric
acid ester salts such as higher alcohol sulfuric acid ester salts,
alkyl ether sulfates and polyoxyethylene alkylphenyl ethers, and
phosphoric acid ester salts such as alkyl phosphates. Examples of
the nonionic surfactant include ethers such as polyoxyethylene
alkyl ethers, ether esters such as polyoxyethylene ethers of a
glycerin ester, and esters such as polyethylene glycol fatty
esters, glycerin esters and sorbitan esters. The content of the
surfactant in the whole pad is preferably 0 to 10% by mass,
particularly preferably 0 to 5% by mass.
[0119] Examples of the above filler include materials which improve
stiffness, such as calcium carbonate, magnesium carbonate, talc and
clay, and materials having a polishing effect such as manganese
dioxide, manganese trioxide and barium carbonate.
[0120] The abrasive pad of the present invention may have a fixing
layer 13 for fixing the abrasive pad on a polishing machine for
polishing on the rear surface opposite to the polishing surface as
shown in FIG. 22. The fixing layer is not particularly limited if
it can fix the abrasive pad itself.
[0121] This fixing layer may be a layer consisting of a layer
formed by using an adhesive double-coated tape, for example, an
adhesive layer 131 and a peel layer 132 formed on the outer surface
of the adhesive layer 131, or an adhesive layer 131 formed by
applying an adhesive. The peel layer 132 may be formed on the outer
surface of the adhesive layer formed by applying an adhesive.
[0122] The adhesive material for forming the fixing layer is not
particularly limited. It is, for example, a thermoplastic,
thermosetting or photo 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.
[0123] 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 abrasive pad on
the polishing machine by removing the peel layer at the time of
use.
[0124] 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.
[0125] It is preferred that a fixing layer should not be formed in
the path of transmitted light when a through hole is formed in the
fixing layer.
[0126] 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.
[0127] The above additives which have been contained in slurry may
be contained in the whole abrasive pad of the present invention,
particularly its abrasive substrate or light transmitting member.
Other additives may further be contained. A groove or dot pattern
may be formed on the polishing surface in a predetermined
shape.
[0128] The planar shape of the abrasive pad is not particularly
limited and may be circular (disk-like) or polygonal such as
quadrilateral (belt-like, roller-like). The size of the abrasive
pad is not particularly limited but may be 500 to 900 mm in
diameter when it is disk-shaped.
[0129] The method of manufacturing the abrasive pad of the present
invention is not particularly limited but the abrasive pad of the
present invention may be manufactured by using mainly the following
metal mold for insert molding.
[0130] Metal Mold for Insert Molding
[0131] The metal mold for insert molding of the present invention
has a projection portion(s) and/or a depressed portion(s) for
positioning the light transmitting member or the abrasive substrate
which is molded in advance.
[0132] The position, shape, size and number of the projection
portions and/or depressed portions for positioning the light
transmitting member or the abrasive substrate are not particularly
limited if they can position the light transmitting member or the
abrasive substrate.
[0133] 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 are arranged to
surround the light transmitting member as shown in FIG. 12 and FIG.
13, (2) the above projections are each fitted in a depression
formed in the center of the bottom of the light transmitting
member, or (3) a ring-shaped projection, partially ring-shaped
projection or quadrilateral projections, for example, prolonged
projections are arranged to surround the light transmitting member
in a ring-shaped or quadrilateral form so that they are mated with
the light transmitting member having a circular bottom or
quadrilateral bottom. As for the projection portion(s) for
positioning the abrasive substrate, a disk-like or small
quadrilateral pillar-like projection is fitted in a hole for
accepting the light transmitting member in the abrasive substrate
as shown in FIG. 16 and FIG. 17, or a dot-like, point-like or
prolonged projection is fitted in a depression formed in the
abrasive substrate.
[0134] Since the surface of the projection for fixing the abrasive
substrate is a surface for forming the surface layer of the light
transmitting member, the surface of the projection desirably has
excellent flatness to improve the light transmission properties of
the light transmitting member. It is particularly preferably a
mirror finish surface.
[0135] As for the depressed portion(s) for positioning the light
transmitting member, as shown in FIG. 19 and FIG. 20, a circular or
quadrilateral depression is formed to be mated with the light
transmitting member, or depressions are arranged to be mated with
dot-like, point-like or prolonged projections formed in the light
transmitting member.
[0136] Further, as for the depressed portion(s) for positioning the
abrasive substrate, depressions are arranged to be mated with
dot-like, point-like and prolonged projections formed on the bottom
portion of the abrasive substrate.
[0137] Method of Manufacturing Abrasive Pad
[0138] The method of manufacturing the abrasive pad of the present
invention is not particularly limited if the light transmitting
member or the abrasive substrate can be held in the metal mold and
the material for forming the light transmitting member or the
abrasive substrate can be injected into the cavity. To facilitate
the manufacture of the abrasive pad of the present invention, the
above metal mold for insert molding is preferably used.
[0139] This manufacturing method is mainly the following method (1)
or (2).
[0140] (1) A dispersion is obtained by pre-kneading a matrix, a
water-soluble substance and the like 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.
[0141] Then, this light transmitting member is set in a metal mold
having a cavity and a dispersion for forming the abrasive
substrate, obtained by kneading or the like, is injected and molded
to obtain an abrasive pad.
[0142] The above method (1) will be described in detail with
reference to FIG. 13 to FIG. 15. The molded light transmitting
member is held between the projection portions of the metal mold
for insert molding having projection portions 721 for positioning
as shown in FIG. 13. Thereafter, the metal mold 71 is fastened and
the dispersion for forming the abrasive substrate, obtained by
kneading or the like, is injected from an injection port (not
shown) as understood from FIG. 14. This dispersion is solidified by
cooling to mold an abrasive pad. Before the above metal mold is
fastened, the dispersion for forming the abrasive substrate may be
directly injected and then the above mold 71 may be fastened before
molding.
[0143] Thereby, an abrasive pad having a sectional form shown in
FIG. 15 is obtained.
[0144] (2) An abrasive 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 abrasive substrate and molded in the metal
mold to manufacture the light transmitting member, thereby
obtaining an abrasive pad. The above hole may be a hole having a
bottom or a through hole without a bottom. An abrasive substrate
having a through hole is commonly used.
[0145] The above method (2) will be described with reference to
FIG. 17. An abrasive substrate molded in a predetermined shape is
held onto the projection portion 721 of a metal mold for insert
molding having a projection portion for positioning as shown in
FIG. 17. Thereafter, the mold 71 is fastened and the dispersion for
forming the abrasive substrate, obtained by kneading or the like,
is injected from an injection port (not shown) to be molded. Before
the above mold is fastened, the dispersion for forming the abrasive
substrate may be directly injected and the above mold 71 may be
fastened to mold it.
[0146] The abrasive pad shown in FIG. 2 is thereby obtained.
[0147] In the above methods (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.
[0148] The height of the light transmitting member and the
thickness of the abrasive substrate do not need to be the same.
Further, they may be processed to a desired thickness with abrasive
paper, et al.
[0149] By this insert molding method, abrasive pads having a
complex sectional form as shown in FIGS. 1 to 8 can be easily
manufactured. The abrasive substrate and the light transmitting
member can be firmly and easily bonded together.
[0150] A groove or dot pattern may be formed in a predetermined
shape on the polishing surface of the abrasive pad of the present
invention as required in order to facilitate the discharge 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 abrasive
pad by reducing the thickness of the above light transmitting
member.
[0151] Abrasive Laminated Pad
[0152] The abrasive laminated pad of the present invention
comprises the abrasive pad of the present invention and a base
layer formed on the rear surface of the abrasive pad and has light
transmission properties in the lamination direction.
[0153] The above "base layer" is a layer 81 formed on the rear
surface opposite to the polishing surface of the abrasive pad as
shown in FIG. 23. It doesn't matter whether the base layer has
light transmission properties or not. For example, a base layer
made of a material having the same or higher light transmission
properties than the light transmitting member is used to secure
light transmission properties for the abrasive laminated pad. In
this case, a cut-away (through hole) may be or may not be formed.
Further, when a base layer having no light transmission properties
is used, the light transmission properties of the abrasive
laminated pad can be secured by cutting away part of the base layer
for transmitting light.
[0154] The shape of the base layer is not particularly limited and
its planar shape may be quadrate, for example, quadrilateral, or
circular. In general, it can be formed as a thin sheet. This base
layer may be the same in planar shape as the abrasive pad. When it
has a cut-away portion for securing light transmission, this
portion is excluded.
[0155] 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 abrasive substrate.
[0156] 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
abrasive pad. Thereby, the abrasive laminated pad has sufficiently
high flexibility and suitable conformability to the unevenness of
the surface to be polished as a whole.
[0157] The same fixing layers 131 and 132 as in the abrasive pad
may be formed on the abrasive laminated pad of the present
invention as shown in FIG. 24. They are generally formed on the
rear surface of the base layer of the abrasive laminated pad, that
is, the surface opposite to the polishing surface. They may be the
same as that used in the above abrasive pad.
[0158] Further, the abrasive laminated pad is not limited to a
particular shape and may be the same in shape and size as
above.
[0159] Method of Polishing a Semiconductor Wafer
[0160] The method of polishing a semiconductor wafer of the present
invention is to polish a semiconductor wafer with the abrasive pad
or abrasive laminated pad of the present invention, using an
optical end-point detection device for detecting the polishing end
point of the semiconductor wafer.
[0161] The above "optical end-point detection device" 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 transmitting light to the polishing surface through the light
transmitting member from the rear surface side of the abrasive pad.
Other measurement principles are not particularly limited.
[0162] In the method of polishing a semiconductor wafer of the
present invention, the detection of an end point can be carried out
without reducing polishing efficiency. For example, when the
abrasive pad or the abrasive laminated pad, is disk-shaped, light
transmitting members are arranged in a loop and 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.
[0163] In the method of polishing a semiconductor wafer of the
present invention, a polishing machine shown in FIG. 25 may be
used. That is, the machine comprises a rotatable base 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 base 2, and an optical
end-point detection unit 6 installed below the base 2.
[0164] In this polishing machine, the abrasive pad (including the
abrasive laminated pad) 1 of the present invention is fixed on the
base 2, and the semiconductor wafer 4 is fixed to the lower end
face of the pressure head 3 and pressed on the abrasive pad at a
predetermined pressure. Slurry is dropped on the base 2 from the
slurry feed unit 5 in a predetermined amount each time, and the
base 2 and the pressure head 3 are turned to bring the
semiconductor wafer in slide contact with the abrasive pad for
polishing.
[0165] End-point detection radiation R.sub.1 having a predetermined
wavelength or wavelength range from the optical end-point detection
unit 6 is applied to the surface to be polished of the
semiconductor wafer 4 from the back of the base 2 through the light
transmitting member 11 for polishing. That is, the base 2 itself
has light transmission properties or the end-point detection
radiation can be transmitted through a cut-away portion of the base
2. Reflected radiation R.sub.2 obtained by reflecting this
end-point detection radiation R.sub.1 from the surface to be
polished 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 surface to be polished is monitored from
this reflected light.
[0166] 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. 26. This laminated substrate
comprises a substrate made of silicon et al, a fist insulating film
made of silicon oxide et al, a second insulating film having a
groove (insulating material is selected from TEOS oxide film
(silicon oxide-based insulating film prepared by a chemical vapor
deposition method using tetraethoxysilane as raw material)
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.).
[0167] 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.
[0168] 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
in at least 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 and
may further comprise a stopper layer as a stopper for polishing
formed on the insulating film) having a groove on at least its
front surface. For the polishing of this object to be polished,
after the buried material deposited excessively is removed by
polishing with the abrasive pad of the present invention, the
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 at the same
time.
[0169] The buried material is, for example, (1) an insulating
material used in the STI (Shallow Trench Isolation) step, (2) at
least one metal wiring material selected from Al and Cu used in the
damascene step, (3) at least one via plug material selected from W,
Al and Cu used in the step of forming a via plug, or (4) an
insulating material used in the step of forming an interlayer
insulating film.
[0170] 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.
[0171] The above insulating material is a silicon oxide (SiO.sub.2)
film, a boron phosphorus silicate film (BPSG film) which comprises
SiO.sub.2 and small amounts of boron and phosphorus, an insulating
film called "FSG (Fluorine doped Silicate Glass)" formed by doping
SiO.sub.2 with fluorine, or a silicon oxide-based insulating film
having a small dielectric constant.
[0172] 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.
[0173] The above thermal oxide film can be formed by exposing
high-temperature silicon to an oxidizing atmosphere and chemically
reacting silicon with oxygen or silicon with water.
[0174] The above PETEOS film can be formed from tetraethyl
orthosilicate (TEOS) by CVD making use of plasma as accelerating
means.
[0175] The above HDP film can be formed from tetraethyl
orthosilicate (TEOS) by CVD making use of high-density plasma as
accelerating means.
[0176] The above silicon oxide film obtained by thermal CVD can be
obtained by normal-pressure CVD (AP-CVD) or low-pressure CVD
(LP-CVD).
[0177] The above boron phosphorus silicate film (BPSG film) can be
obtained by normal-pressure CVD (AP-CVD) or low-pressure CVD
(LP-CVD).
[0178] The above insulating film called "FSG" can be formed by CVD
making use of high-density plasma as an accelerator.
[0179] Further, the above silicon oxide-based insulating film
having a small dielectric constant can be obtained by applying a
raw material to a substrate by rotational coating or the like and
heating it in an oxidizing atmosphere. Examples of the silicon
oxide-based insulating film include an HSQ film (Hydrogen
Silsequioxane film) made from triethoxysilane and MSQ film (Methyl
Silsequioxane film) containing tetraethoxysilane and methyl
trimethoxysilane as one of its raw materials.
[0180] Insulating films having a small dielectric constant made
from an organic polymer such as polyarylene-based polymer,
polyarylene ether-based polymer, polyimide-based polymer or
benzocyclobutene polymer are also included.
[0181] This flush type laminate is shown in FIG. 26. That is, the
laminated substrate 9 comprises a substrate 91 made of silicon et
al, an insulating film 92 made of silicon oxide et al formed on the
silicon substrate 91, an insulating film 93 formed of silicon
nitride et al 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 et al 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.
[0182] The object to be polished including no buried material is a
substrate made of polysilicon, bare silicon et al.
EXAMPLES
[0183] The following examples are provided to further illustrate
the present invention.
Example 1
[0184] (1) Manufacture of Light Transmitting Member
[0185] 97 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
and 3 vol % of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio
Research Corporation of Yokohama) as a water-soluble substance were
kneaded together by a kneader heated at 120.degree. C. Thereafter,
dicumyl peroxide (Percumyl D of NOF Corporation) was added to the
kneaded product in an amount of 0.8 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene and .beta.-cyclodextrin
and further kneaded, a crosslinking reaction was carried out in a
press mold at 170.degree. C. for 20 minutes to mold the kneaded
product, and the molded product was cut to obtain a light
transmitting member measuring 58 mm.times.21 mm.times.2.5 mm.
[0186] (2) Kneading of Abrasive Substrate Material
[0187] 80 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
which would be crosslinked later to become a matrix material and 20
vol % of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio Research
Corporation of Yokohama) as a water-soluble substance were kneaded
together by a kneader heated at 120.degree. C. Thereafter, dicumyl
peroxide (Percumyl D of NOF Corporation) was added to the kneaded
product in an amount of 0.8 part by mass based on 100 parts by mass
of the total of 1,2-polybutadiene and .beta.-cyclodextrin and
further kneaded.
[0188] (3) Manufacture of Abrasive Pad
[0189] The light transmitting member obtained in (1) above was set
between the projection portions (721) of a metal mold for insert
molding as shown in FIG. 13, the remaining space in the cavity of
the above metal mold was filled with the abrasive substrate
material kneaded in (2) above, the metal mold (71) was fastened,
and a crosslinking reaction was carried out at 170.degree. C. for
20 minutes to mold a disk-like abrasive pad having a diameter of 60
cm and a thickness of 2.5 mm.
[0190] (4) Evaluation of Abrasive Pad
[0191] The abrasive pad manufactured as described above had a Shore
D hardness of 70 and a tensile residual elongation of 2%.
[0192] This abrasive pad was mounted on the base of a polishing
machine to polish a thermal oxide film water at a base revolution
of 50 rpm and a slurry flow rate of 100 cc/min. When the polishing
rate was measured, it was 980 .ANG./min.
[0193] The light transmitting member obtained in the above Example
(1) was measured for its transmittance at a wavelength of 650 nm
with a UV absorptiometer (U-2010 of Hitachi, Ltd.). As a result,
the average integrated transmittance of 5 times of measurement was
30%.
Comparative Example 1
[0194] 80 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
which would be crosslinked later to become a matrix material and 20
volt of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio Research
Corporation of Yokohama) as a water-soluble substance were kneaded
together by a kneader heated at 120.degree. C. Thereafter, dicumyl
peroxide (Percumyl D of NOF Corporation) was added to the kneaded
product in an amount of 0.8 part by mass based on 100 parts by mass
of the total of 1,2-polybutadiene and .beta.-cyclodextrin and
further kneaded, and a crosslinking reaction was carried out in a
press mold at 170.degree. C. for 20 minutes to mold a disk-like
abrasive pad having a diameter of 60 cm and a thickness of 2.5
mm.
[0195] This polishing rate of this abrasive pad was 1,010
.ANG./min.
Comparative Example 2
[0196] A commercially available foamed polyurethane abrasive pad
(IC1010 of Rodel Co., Ltd.; Rohm and Haas Electronic Materials)
having no light transmission properties was designated as
Comparative Example 2. The polishing rate of this abrasive pad was
950 .ANG./min.
[0197] It can be understood from comparison between the polishing
rate of Comparative Examples 1 and 2 and the polishing rate of
Example 1 that the abrasive pad of the present invention is by no
means inferior to an abrasive pad having no light transmitting
member in polishing rate.
[0198] Since the light transmitting member and the abrasive
substrate are fused together in the abrasive pad of the present
invention, slurry does not leak to the rear side of the abrasive
pad while the abrasive pad is used and the optical end-point
detection unit (6) shown in FIG. 25 is not contaminated.
Example 2
[0199] (1) Manufacture of Light Transmitting Member
[0200] 95 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
and 5 vol % of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio
Research Corporation of Yokohama) as a water-soluble substance were
kneaded together by a kneader heated at 160.degree. C. Thereafter,
dicumyl peroxide (Percumyl D of NOF Corporation) was added to the
kneaded product in an amount of 1.0 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene and .beta.-cyclodextrin
and further kneaded, a crosslinking reaction was carried out in a
press mold at 170.degree. C. for 20 minutes to mold the kneaded
product, and the molded product was cut to obtain a light
transmitting member measuring 58 mm.times.21 mm.times.2.5 mm.
[0201] (2) Kneading of Abrasive Substrate Material
[0202] A mixture was prepared by dry blending 80 wt % of
1,2-polybutadiene (JSR RB830 of JSR Corporation) with 20 wt % of a
styrene-butadiene elastomer (JSR TR2827 of JSR Corporation). 70
volt of the mixture which would be crosslinked later to become a
matrix material was kneaded with 30 volt of .beta.-cyclodextrin
(Dexy Pearl .beta.-100 of Bio Research Corporation of Yokohama) as
a water-soluble substance by a double-screw extruder. Thereafter,
dicumyl peroxide (Percumyl D of NOF Corporation) was added to the
kneaded product in an amount of 0.8 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene, styrene-butadiene
elastomer and .beta.-cyclodextrin and further kneaded.
[0203] (3) Manufacture of Abrasive Pad
[0204] The light transmitting member obtained in (1) above was
set-between the projection portions (721) of the metal mold for
insert molding as shown in FIG. 13, and the remaining space in the
cavity of the metal old was filled with the abrasive substrate
material kneaded in (2) above. The metal mold (71) was fastened,
and a crosslinking reaction was carried out at 170.degree. C. for
20 minutes to mold a disk-like abrasive pad having a diameter of 60
cm and a thickness of 2.5 mm.
[0205] (4) Evaluation of Abrasive Pad
[0206] The abrasive pad manufactured as described above had a Shore
D hardness of 65 and a tensile residual elongation of 2%.
Example 3
[0207] A disk-like abrasive pad having a diameter of 60 cm and a
thickness of 2.5 mm was obtained in the same manner as in Example 1
except that potassium sulfate (manufactured by Otsuka Chemical Co.,
Ltd.) was used in place of .beta.-cyclodextrin.
[0208] This abrasive pad had a Shore D hardness of 68 and a tensile
residual elongation of 2%.
Example 4
[0209] (1) Manufacture of Abrasive Pad Substrate
[0210] 80 vol % of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
which would be crosslinked later to become a matrix material and 20
volt of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio Research
Corporation of Yokohama) as a water-soluble substance were kneaded
together by a kneader heated at 120.degree. C. Thereafter, dicumyl
peroxide (Percumyl D of NOF Corporation) was added to the kneaded
product in an amount of 0.8 part by mass based on 100 parts by mass
of the total of 1,2-polybutadiene and .beta.-cyclodextrin and
further kneaded, and a crosslinking reaction was carried out in a
press mold at 170.degree. C. for 10 minutes to obtain an abrasive
substrate having a diameter of 820 mm. A 59.4 mm.times.21.0 mm hole
was made at a position 195 mm away from the center of the molded
product as shown in FIG. 27. In FIG. 27, "a" is the central point
of the abrasive pad substrate and "b" is the central point of the
through hole formed to the central point of the abrasive pad
substrate.
[0211] (2) Kneading of Light Transmitting Member Material
[0212] 97 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
and 3 volt of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio
Research Corporation of Yokohama) as a water-soluble substance were
kneaded together by a kneader heated at 120.degree. C. Thereafter,
dicumyl peroxide (Percumyl D of NOF Corporation) was added to the
kneaded product in an amount of 0.8 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene and .beta.-cyclodextrin
and further kneaded.
[0213] (3) Manufacture of Abrasive Pad
[0214] The abrasive pad substrate manufactured in (1) above was set
onto the projection portion (721) of the metal mold for insert
molding as shown in FIG. 17 to ensure that the hole of the abrasive
substrate was situated at a position corresponding to the light
transmitting member.
[0215] Further, the light transmitting member material kneaded in
(2) above was injected into the space above the projection portion
in the cavity of the metal mold, the metal mold (71) was fastened,
and a crosslinking reaction was carried out at 170.degree. C. for
20 minutes to mold an abrasive pad having a diameter of 820 mm in
which the rear surface of the light transmitting member was
recessed from the rear surface of the abrasive substrate.
[0216] (4) Evaluation of Abrasive Pad
[0217] This abrasive pad had a Shore D hardness of 70 and a tensile
residual elongation of 2%.
Example 5
[0218] (1) Manufacture of Abrasive Pad Substrate
[0219] A mixture was prepared by dry blending 80 wt % of
1,2-polybutadiene (JSR RB830 of JSR Corporation) with 20 wt % of a
styrene-butadiene elastomer (JSR TR2827 of JSR Corporation). 70
volt of the mixture which would be crosslinked later to become a
matrix material was kneaded with 30 volt of .beta.-cyclodextrin
(Dexy Pearl .beta.-100 of Bio Research Corporation of Yokohama) as
a water-soluble substance by a double-screw extruder. Thereafter,
dicumyl peroxide (Percumyl D of NOF Corporation) was added to the
kneaded product in an amount of 0.8 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene, styrene-butadiene
elastomer and .beta.-cyclodextrin and further kneaded, and a
crosslinking reaction was carried out in a metal mold for insert
molding having above light transmitting member at 170.degree. C.
for 20 minutes to mold an abrasive substrate having a diameter of
820 mm. A 59.4 mm.times.21.0 mm hole was made at a position 195 mm
away from the center of the molded product as shown in FIG. 27.
[0220] (2) Kneading of Light Transmitting Member Material
[0221] 97 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
and 3 volt of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio
Research Corporation of Yokohama) as a water-soluble substance were
kneaded together by a kneader heated at 120.degree. C. Thereafter,
dicumyl peroxide (Percumyl D of NOF Corporation) was added to the
kneaded product in an amount of 0.8 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene and .beta.-cyclodextrin
and further kneaded.
[0222] (3) Manufacture of Abrasive Pad
[0223] The abrasive pad substrate manufactured in (1) above was set
onto the projection portion (721) of the metal mold for insert
molding as shown in FIG. 17 to ensure that the hole of the abrasive
substrate manufactured in (1) above was situated at a position
corresponding to the light transmitting member.
[0224] Further, the light transmitting member material kneaded in
(2) above was injected into the space above the projection portion
in the cavity of the metal mold, the metal mold (71) was fastened,
and a crosslinking reaction was carried out at 170.degree. C. for
20 minutes to mold an abrasive pad having a diameter of 820 mm in
which the rear surface of the light transmitting member was
recessed from the rear surface of the abrasive substrate.
[0225] (4) Evaluation of Abrasive Pad
[0226] This abrasive pad had a Shore D hardness of 70 and a tensile
residual elongation of 2%.
Example 6
[0227] After an abrasive pad was manufactured in the same manner as
in Example 5, a double-tuck tape (Double Tuck Tape #512 of Sekisui
Chemical Co., Ltd.) essentially composed of foamed polyethylene was
formed as a base layer on the non-polishing side of the abrasive
pad. Further, a 60 mm.times.23 mm through hole was made in the base
layer at a position corresponding to the light transmitting member
to secure light transmission properties.
Example 7
[0228] (1) Manufacture of Abrasive Pad Substrate
[0229] A mixture was prepared by dry blending 70 wt % of
1,2-polybutadiene (JSR RB830 of JSR Corporation) with 30 wt % of
commercially available polystyrene (HF55 of PS Japan Co., Ltd.). 95
vol % of the mixture which would be crosslinked later to become a
matrix material was kneaded with 5 vol % of .beta.-cyclodextrin
(Dexy Pearl .beta.-100 of Bio Research Corporation of Yokohama) as
a water-soluble substance by a double-screw extruder. Thereafter,
dicumyl peroxide (Percumyl D40 of NOF Corporation) was added to the
kneaded product in an amount of 0.4 part by mass based on 100 parts
by mass of the total of 1,2-polybutadiene, polystyrene and
P-cyclodextrin and further kneaded, and a crosslinking reaction was
carried out in a metal mold for insert molding having above light
transmitting member at 170.degree. C. for 10 minutes to mold an
abrasive substrate having a diameter of 820 mm. A 59.4
mm.times.21.0 mm rectangular hole was made at a position 195 mm
away from the center of the molded product as shown in FIG. 27.
[0230] (2) Kneading of Light Transmitting Member Material
[0231] 98 volt of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
which would be crosslinked later to become a matrix material and 2
vol % of .beta.-cyclodextrin (Dexy Pearl P-100 of Bio Research
Corporation of Yokohama) as a water-soluble substance were kneaded
together by a double-screw extruder heated at 160.degree. C.
Thereafter, dicumyl peroxide (Percumyl D40 of NOF Corporation) was
added to the kneaded product in an amount of 0.3 part by mass based
on 100 parts by mass of the total of 1,2-polybutadiene and
.beta.-cyclodextrin and further kneaded.
[0232] (3) Manufacture of Abrasive Pad
[0233] The abrasive pad substrate manufactured in (1) above was set
onto the projection portion (721) of the metal mold for insert
molding as shown in FIG. 17 to ensure that the hole of the abrasive
substrate manufactured in (1) above was situated at a position
corresponding to the light transmitting member.
[0234] Further, the light transmitting member material kneaded in
(2) above was injected into the space above the projection portion
in the cavity of the metal mold. The metal mold (71) was then
fastened, and a crosslinking reaction was carried out at
170.degree. C. for 18 minutes to mold an abrasive pad having a
diameter of 820 mm in which the rear surface of the light
transmitting member was recessed from the rear surface of the
abrasive pad substrate.
[0235] The top surface of the projection portion (721) of the metal
mold used in this example was a mirror finish surface.
[0236] (4) Evaluation of Abrasive Pad
[0237] This abrasive pad had a Shore D hardness of 65 and a tensile
residual elongation of 2%.
[0238] As described above, optical end-point detection can be
carried out without reducing polishing efficiency when the abrasive
pad of the present invention is used. Not only the polishing end
point but also all the polishing states can be optically monitored.
During the use of the abrasive pad, slurry does not leak to the
rear side of the abrasive pad.
[0239] When at least part of the water-insoluble matrix material of
the light transmitting member is a crosslinked polymer, it is
possible to prevent pores from being filled at the time of
polishing and dressing. It is also possible to prevent the surface
of the abrasive pad from being fluffed excessively. Therefore, the
retainability of the slurry is high at the time of polishing, the
retainability of the slurry can be easily recovered by dressing,
and scratching can be prevented.
[0240] When the crosslinked polymer for forming the light
transmitting member is crosslinked 1,2-polybutadiene, the above
effect can be fully obtained and sufficiently high light
transmission properties can be obtained by containing the above
crosslinked polymer. The crosslinked 1,2-polybutadiene is stable to
a strong acid or strong alkali contained in many kinds of slurry
and further has excellent durability as it is rarely softened by
water absorption.
[0241] By reducing the thickness of the light transmitting member,
light transmission properties can be improved. When the materials
for forming the light transmitting member and the abrasive
substrate are different in type or when they are the same in type
but different in ratio, as the materials for forming the light
transmitting member can be changed, it is possible to improve the
light transmission properties of the light transmitting member as
required.
[0242] Further, with the method of manufacturing an abrasive pad of
the present invention, an abrasive pad having a complex shape can
be easily manufactured because a light transmitting member and an
abrasive substrate are manufactured as an integrated unit by using
a metal mold and slurry does not leak to the rear side because the
light transmitting member and the abrasive substrate are fused
together.
[0243] The metal mold for insert molding of the present invention
makes it easy to manufacture an abrasive pad comprising an abrasive
substrate and a light transmitting member.
[0244] Optical end-point detection can be carried out without
reducing polishing efficiency when the abrasive laminated pad of
the present invention is used. Not only the polishing end point but
also all the polishing states can be optically observed. The
abrasive laminated pad has sufficiently high flexibility and
suitable conformability to the unevenness of the surface to be
polished.
[0245] Further, when the abrasive laminated pad has a fixing layer,
it can be fixed on a polishing machine easily and quickly. Since it
has light transmission properties, it does not impair the light
transmission properties of the light transmitting member.
[0246] With the polishing method of the present invention, optical
end-point detection can be carried out without reducing polishing
efficiency.
* * * * *