U.S. patent application number 10/311503 was filed with the patent office on 2003-09-11 for polishing pad.
Invention is credited to Imahara, Yasutaka, Komukai, Takuji, Osaki, Kouichi.
Application Number | 20030171081 10/311503 |
Document ID | / |
Family ID | 18684362 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030171081 |
Kind Code |
A1 |
Komukai, Takuji ; et
al. |
September 11, 2003 |
Polishing pad
Abstract
A polishing pad includes a pad body; and a transparent window
integrally formed in the pad body. The window is formed of a
material which is more susceptible to abrasion than a material of
the pad body. The pad body has a plurality of grooves formed in a
surface thereof, and the window has no grooves in a surface
thereof. A surface of the window is recessed with respect to a
surface of the pad. The polishing pad prevents a slurry from
settling on the window so as to improve the detection precision of
the polishing rate. Furthermore, the polishing pad prevents the
window from gradually projecting with respect to the pad body by
dressing during polishing so as to substantially eliminate adverse
effect on the polishing characteristic.
Inventors: |
Komukai, Takuji; (Mie,
JP) ; Imahara, Yasutaka; (Mie, JP) ; Osaki,
Kouichi; (Mie, JP) |
Correspondence
Address: |
SNELL & WILMER
ONE ARIZONA CENTER
400 EAST VAN BUREN
PHOENIX
AZ
850040001
|
Family ID: |
18684362 |
Appl. No.: |
10/311503 |
Filed: |
December 16, 2002 |
PCT Filed: |
June 18, 2001 |
PCT NO: |
PCT/JP01/05192 |
Current U.S.
Class: |
451/285 ;
451/526; 451/6 |
Current CPC
Class: |
B24B 37/26 20130101;
B24B 37/205 20130101; B24B 53/017 20130101 |
Class at
Publication: |
451/285 ; 451/6;
451/526 |
International
Class: |
B24B 049/00; B24D
011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2000 |
JP |
2000-183846 |
Claims
1. A polishing pad, comprising: a pad body; and a transparent
window integrally formed in the pad body, wherein the window is
formed of a material which is more susceptible to abrasion than a
material of the pad body.
2. A polishing pad, comprising: a pad body; and a transparent
window integrally formed in the pad body, wherein the pad body has
a plurality of grooves formed in a surface thereof, and the window
has no grooves in a surface thereof.
3. A polishing pad, comprising: a pad body; and a transparent
window integrally formed in the pad body, wherein a surface of the
window is recessed with respect to a surface of the pad body.
4. A polishing pad according to claim 3, wherein the pad body has a
plurality of grooves formed in a surface thereof, and the window
has no grooves in a surface thereof.
5. A polishing pad according to claim 1, wherein the pad body and
the window are integrally formed as a result of placing one of the
window and a resin block forming the window in a mold and then
injecting a resin forming the pad body into the mold.
6. A polishing pad according to claim 5, wherein the window and the
resin block are each formed of a transparent resin containing a
urethane resin.
7. A polishing pad according to claim 2, wherein the pad body and
the window are integrally formed as a result of placing one of the
window and a resin block forming the window in a mold and then
injecting a resin forming the pad body into the mold.
8. A polishing pad according to claim 7, wherein the window and the
resin block are each formed of a transparent resin containing a
urethane resin.
9. A polishing pad according to claim 3, wherein the pad body and
the window are integrally formed as a result of placing one of the
window and a resin block forming the window in a mold and then
injecting a resin forming the pad body into the mold.
10. A polishing pad according to claim 9, wherein the window and
the resin block are each formed of a transparent resin containing a
urethane resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to a polishing pad used for
polishing a semiconductor device or other electronic components.
Specifically, the present invention relates to a polishing pad used
in a polishing apparatus adopting a CMP (chemical mechanical
polishing) technology, the polishing pad having a transparent
window through which laser light or visible light is transmitted,
in order to allow a polishing rate of a wafer (i.e., the amount of
wafer removed by polishing) to be measured while polishing the
wafer.
BACKGROUND ART
[0002] A semiconductor multiple layer IC is preferably smoothed at
the semiconductor wafer stage during the production thereof.
[0003] A semiconductor wafer is usually smoothed by a CMP polishing
apparatus adopting a CMP technology. The CMP polishing apparatus
includes a lower board having a circular rotatable plate on which a
polishing pad is mounted, an upper board for pressing a
semiconductor wafer to the polishing pad, and a section for
supplying a slurry to the polishing pad.
[0004] Using such a CMP polishing apparatus, a polishing rate of
the wafer is measured while the wafer is polished. Since the
polishing rate is measured by irradiating a surface of the wafer to
be polished with laser light from a rear surface of the polishing
pad, the polishing pad needs to have a transparent window for
allowing the laser light to be transmitted through the polishing
pad. The rear surface of the polishing pad faces the lower
board.
[0005] A conventional polishing pad includes a pad body and a foam
layer stacked on the pad body with a pressure-sensitive adhesive
layer interposed therebetween. The pad body has an opening at a
prescribed position thereof, and a window formed of a transparent
resin is fit in the opening.
[0006] Conventionally, the window is provided by the following
method.
[0007] (1) The pad body is punched out to form a hole, and a
transparent plate is fit in the hole as a window.
[0008] However, this method has the following problems.
[0009] (i) A gap is made between the pad body and the window, and a
slurry flows into the gap so as to cloud the window, which prevents
the laser light from being clearly transmitted. This is fatal to
the measurement of the polishing rate.
[0010] (ii) The window is deformed, for example, warped, which may
cause malfunction.
[0011] (iii) A thickness of the window is set with respect to the
thickness of the pad body. Since the thickness of the window is
provided with a tolerance, the thickness of the window can be equal
to the thickness of the pad body. In this case, the window may
project out of the pad body depending on the manner of setting the
window.
[0012] (iv) The window, which is bonded to the foam layer with a
two-sided adhesive tape provided along only 3.0 to 4.0 mm-long
portions along the circumference of the window, is easily peeled
off.
[0013] In order to solve these problems, the following method of
forming a window is proposed.
[0014] (2) Before forming the pad body, a transparent resin plate
which will become a window is secured at a prescribed position in a
mold. Then, a resin for forming the pad body injected into the
mold, thus forming a resin cake. By slicing the resin cake, a pad
sheet integrally including the pad body and the window is produced.
There is no gap between the pad body and the window.
[0015] This production method solves the problems of (i), (ii) and
(iv) described above.
[0016] However, the polishing pad produced by this method has the
following problems.
[0017] (i) In general, fine grooves are formed in the entire
surface of the pad body in order to satisfactorily disperse the
slurry. The method (2) inevitably forms the grooves in the window
as well as the pad body. This causes the slurry to be in the
grooves in the window, and thus attenuates the intensity of the
transmitted light when an object to be detected (e.g., a wafer) is
formed of certain materials.
[0018] (ii) When newly produced, the pad body and the window are on
the same plane. Since the material of the window generally has a
higher density and thus less susceptible to abrasion than the
material of the pad body, the window gradually projects from the
pad body as the polishing pad is more and more used for polishing
the wafers. As a result, dressing during polishing may undesirably
scratch the window, which causes light transmission noise, i.e.,
clouds the window and attenuates the intensity of transmitted
light.
[0019] The present invention has an objective of providing a
polishing pad for preventing a slurry from settling in a groove of
a window and thus raising the detection precision of the polishing
rate.
[0020] The present invention has another objective of providing a
polishing pad for preventing a window from gradually projecting
from a pad body as a result of dressing during polishing and thus
improving the polishing characteristic.
DISCLOSURE OF THE INVENTION
[0021] According to one aspect of the invention, a polishing pad
includes a pad body; and a transparent window integrally formed in
the pad body. The window is formed of a material which is more
susceptible to abrasion than a material of the pad body.
[0022] According to another aspect of the invention, a polishing
pad includes a pad body; and a transparent window integrally formed
in the pad body. The pad body has a plurality of grooves formed in
a surface thereof, and the window has no grooves in a surface
thereof.
[0023] According to still another aspect of the invention, a
polishing pad includes a pad body; and a transparent window
integrally formed in the pad body. A surface of the window is
recessed with respect to a surface of the pad body.
[0024] In one embodiment of the invention, the pad body has a
plurality of grooves formed in a surface thereof, and the window
has no grooves in a surface thereof.
[0025] In one embodiment of the invention, the pad body and the
window are integrally formed as a result of placing one of the
window and a resin block forming the window in a mold and then
injecting a resin forming the pad body into the mold.
[0026] In one embodiment of the invention, the window and the resin
block are each formed of a transparent resin containing a urethane
resin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a cross-sectional view of a polishing pad in an
embodiment according to the present invention;
[0028] FIG. 2 is a plan view of the polishing pad shown in FIG.
1;
[0029] FIG. 3 is an enlarged plan view of a window of the polishing
pad shown in FIG. 1:
[0030] FIG. 4A is a cross-sectional view of a board on which the
polishing pad according to the present invention is mountable;
[0031] FIG. 4B is a plan view of the board shown in FIG. 4A;
[0032] FIG. 5A is a cross-sectional view of the board on which the
polishing pad according to the present invention is mountable;
[0033] FIG. 5B is a plan view of the board shown in FIG. 5A;
[0034] FIG. 6A is an enlarged plan view of the board shown in FIGS.
4A, 4B, 5A and 5B, showing a portion corresponding to a window of
the polishing pad;
[0035] FIG. 6B is an enlarged cross-sectional view of the portion
of the board shown in FIG. 6A;
[0036] FIG. 7 shows an recess of the portion of the board shown in
FIGS. 6A and 6B;
[0037] FIG. 8 shows a jig usable for a polishing pad according to
the present invention:
[0038] FIG. 9 shows an opening of the jig shown in FIG. 8;
[0039] FIG. 10 is a graph illustrating the susceptibility to
abrasion of a polishing pad according to the present invention;
[0040] FIG. 11 is a graph illustrating the susceptibility to
abrasion of a conventional polishing pad;
[0041] FIG. 12 is a cross-sectional view of a polishing pad in a
second embodiment according to the present invention; and
[0042] FIG. 13 is a cross-sectional view of a polishing pad in a
third embodiment according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0043] Hereinafter, the present invention will be described by way
of illustrative embodiments with reference to the accompanying
drawings.
[0044] (Embodiment 1)
[0045] A polishing pad 100 according to a first embodiment of the
present invention will be described.
[0046] As shown in FIGS. 1 and 2, the polishing pad 100 includes a
pad body 10 and a window 2 formed in the pad body 10. The pad body
10 is generally formed of a resin layer having fine air holes.
[0047] The polishing pad 100 further includes a pressure-sensitive
adhesive layer 12 provided on a lower surface of the pad body 10, a
base layer 13 formed of a foaming material and provided on the
pressure-sensitive adhesive layer 12, a pressure-sensitive adhesive
layer 14 provided on the base layer 13, and a release sheet (not
shown) provided on the pressure-sensitive adhesive layer 14. For
using the polishing pad 100, the release sheet is peeled off and
the pressure-sensitive adhesive layer 14 is bonded to a lower board
of a polishing apparatus (not shown).
[0048] In FIG. 2, reference numeral 8 represents a V-shaped cutout
used for peeling off the polishing pad 100 from the lower
board.
[0049] The pad body 10 can be formed of, for example, a urethane
resin, an acrylic resin, polycarbonate, polyamide, and polyester.
These materials can be used independently, or a combination of two
or more of these materials can be used. The pad body 10 can be
formed of, for example, an thermoplastic resin by an injection
molding method or an extrusion molding method. Alternatively, the
pad body 10 can be formed of a thermosetting resin by a heating and
curing method.
[0050] The molded resin body is sliced to produce a pad sheet. More
specifically, a block of a transparent material for forming the
window 2 is placed in a mold, and a non-transparent material for
forming the pad body 10 is injected into the mold, thereby forming
the molded resin body. By slicing the molded resin body, a pad
sheet is produced. On the pad sheet, the pressure-sensitive
adhesive layer 12, the base layer 13, the pressure-sensitive
adhesive layer 14, and the release sheet are sequentially provided,
thereby producing the polishing pad 100. The base layer 13 has an
opening 11 at a position corresponding to the position of the
window, 2.
[0051] Instead of the block of the transparent material for forming
the window 2, the window 2 can be placed in the mold.
[0052] The polishing pad 100 produced in this method has the pad
body 10 and the window 2 in an integrated state and does not have
the problem of the gap between the pad body 10 and the window 2 or
the problem of the window 2 projecting from the pad body 10.
[0053] The pad body 10 has a plurality of fine grooves in a surface
thereof. The shape, size and pattern of the grooves can be changed
in accordance with the purpose of use of the polishing pad 100. The
grooves can be, for example, concentric.
[0054] The window 2 is, for example, a transparent resin such as,
for example, polyvinyl chloride, polyvinylidene fluoride,
polyethersulfone, polystyrene, polyethylene,
polytetrafluoroethylene or any of the above-listed materials usable
for the pad body. 10. The block of the material for forming the
window 2 is produced by injection-molding or extrusion-molding one
of these materials and cutting the molded resin into a desired size
and thickness. FIG. 3 shows an example of the window 2. In FIG. 3,
L1 is about 57 mm, L2 is about 50 mm, L3 is about 12 mm, and L4 is
about 14 mm.
[0055] The material of the window 2 is more susceptible to abrasion
than the material of the body pad 10, so that the window 2 is
always recessed with respect to the pad body 10. Thus, the problem
that the window 2 is gradually projected from the pad body 10 as
the polishing pad is more and more used so as to prevent adversely
influencing the polishing characteristic.
[0056] The material of the window 2 can be made more susceptible to
abrasion than the material of the pad 10 by, for example, changing
the mixing ratios of a main component and a curing agent when the
block of the material of the window 2 (for example, urethane) is
polymerized from a urethane prepolymer. For example, the mixing
ratio can be 110% with respect to the usual amount for the main
component containing urethane prepolymer and 100% with respect to
the usual amount for the curing agent. In this case, the material
can be cured at a high temperature of 100.degree. C. or higher.
[0057] (Embodiment 2)
[0058] A polishing pad 200 according to a second embodiment of the
present invention will be described. Identical elements previously
discussed with respect to FIG. 1 bear identical reference numerals
and the detailed descriptions thereof will be omitted.
[0059] As shown in FIG. 12, the polishing pad 200 includes a pad
body 10 and a window 2 integrally formed in the pad body 10.
[0060] The pad body 10 has a plurality of fine grooves 4 in a
surface thereof. The shape, size and pattern of the grooves can be
changed in accordance with the purpose of use of the polishing pad
200. Each groove 4 can be, for example, ring-shaped, and the
plurality of fine grooves 4 can be, for example, concentric. The
window 2 has no grooves on a surface thereof.
[0061] As in the first embodiment, the polishing pad 200 further
includes a pressure-sensitive adhesive layer 12 provided on a lower
surface of the pad body 10, a base layer 13 formed of a foaming
material and provided on the pressure-sensitive adhesive layer 12,
a pressure-sensitive adhesive layer 14 provided on the base layer
13, and a release sheet (not shown) provided on the
pressure-sensitive adhesive layer 14. For using the polishing pad
200, the release sheet is peeled off and the pressure-sensitive
adhesive layer 14 is bonded to a lower board of a polishing
apparatus (not shown).
[0062] The pad body 10 and the window 2 are formed of the same
materials as those in the first embodiment. Preventing the grooves
from being formed in the surface of the window 2 solves the problem
of a slurry settling in the grooves causing light transmission
noise, i.e., clouds the window and attenuates the intensity of
transmitted light.
[0063] The polishing pad 200 is produced as follows.
[0064] FIGS. 4B and 5B are plan views of a board 17 of a curved
groove forming machine. FIG. 4A is a cross-sectional view of the
board 17 taken along lines X-X in FIG. 4B, and FIG. 5A is a
cross-sectional view of the board 17 taken along lines Y-Y in FIG.
5B.
[0065] A pad sheet is secured on the board 17 by a suction force.
The grooves 4 are formed by pressing a cutter knife 19 (FIG. 8) to
a surface of the pad sheet while rotating the board 17.
[0066] A rotation shaft 20 for rotating the board 17 has a suction
hole 21 formed therein which is connected to a suction apparatus
(not shown). The board 17 has a suction path 22 formed therein and
a plurality of suction openings 23 formed at a surface of the board
17. The suction openings 23 are communicated to the suction hole 21
through the suction path 22. In FIGS. 4B and 5B, reference numeral
16 represents a ring groove formed at the surface of the board
17.
[0067] The board 17 has a recess 24 at a position corresponding to
the position of the window 2. As shown in FIGS. 6A, 6B and 7, the
recess 24 has a flat portion 25 slightly recessed from the surface
of the rest of the board 17 and a tapered portion 26 tapering from
the flat portion 25 to the surface of the rest of the board 17. The
plurality of openings 23 described above are also formed in the
flat portion 25.
[0068] The flat portion 25 preferably has a width and a length
which are respectively equal to or greater than the width and the
length of the window 2. Referring to FIG. 7, L5 (width of the flat
portion 25) is, for example, preferably about 5 to 10 mm greater,
and is more preferably about 4 mm greater than the width (L4 in
FIG. 3) of the window 2. The width of the tapered portion 26 (L6)
is preferably about 1.0 to 2.0 mm, and the depth of tapered portion
26 (L7) is preferably about 500 .mu.m or more, more preferably
about 500 to 600 .mu.m. The inner pressure of the suction hole 21
when the pad sheet is absorbed toward surface of the board 17 at
the maximum is preferably 0 to 250 torr.
[0069] When the pad sheet is secured by a suction force on the
board 17, the window 2 is recessed along the topology of the
surface of the board 17. Accordingly, the cutting knife 19 reaches
the pad body 10 on the board 17 so as to form the grooves, but does
not reach the window 2. Thus, the grooves are not formed in the
window 2.
[0070] FIG. 8 shows a jig 27 for preventing the grooves from being
formed in the window 2. The jig 27 is usable instead of forming the
recess 24 as described above.
[0071] The jig 27 is formed of a metal plate or a resin plate
having a thickness of about 0.5 mm and having an opening 29 at a
position corresponding to the position of the window 2. The opening
29 preferably has a width (L11 in FIG. 9) and a length (L10) which
are respectively equal to or greater than the width and the length
of the window 2 by, for example, about 6 to 8 mm. The jig 27 has a
plurality of through-holes 30.
[0072] The jig 27 is placed on the board 17, and window 2 of the
pad sheet which is placed on the jig 27 is recessed due to the
suction force. Thus, the cutting knife 9 does not reach the window
2 and the grooves are prevented from being formed on the window
2.
[0073] (Embodiment 3)
[0074] A polishing pad 300 according to a third embodiment of the
present invention will be described. Identical elements previously
discussed with respect to FIG. 1 bear identical reference numerals
and the detailed descriptions thereof will be omitted.
[0075] As shown in FIG. 13, the polishing pad 300 includes a pad
body 10 and a window 2 integrally formed in the pad body 10.
[0076] The window 2 is recessed (indicated with a recessed portion
6) with respect to the pad body 10, and the pad body 10 has a
plurality of fine grooves 4 in a surface thereof. The shape, size
and pattern of the grooves can be changed in accordance with the
purpose of use of the polishing pad 300. Each groove 4 can be, for
example, ring-shaped, and the plurality of fine grooves 4 can be,
for example, concentric. The window 2 has no grooves on a surface
thereof.
[0077] As in the first embodiment, the polishing pad 300 further
includes a pressure-sensitive adhesive layer 12 provided on a lower
surface of the pad body 10, a base layer 13 formed of a foaming
material and provided on the pressure-sensitive adhesive layer 12,
a pressure-sensitive adhesive layer 14 provided on the base layer
13, and a release sheet (not shown) provided on the
pressure-sensitive adhesive layer 14. For using the polishing pad
300, the release sheet is peeled off and the pressure-sensitive
adhesive layer 14 is bonded to a lower board of a polishing
apparatus (not shown).
[0078] The conventional polishing pad has a pad body and a window
on the same plane. Therefore, the window gradually projects from
the pad body as the polishing pad is more and more used for
polishing the wafers. As a result, dressing during polishing may
undesirably scratch the window, which causes light transmission
noise, i.e., clouds the window and attenuates the intensity of
transmitted light. The polishing pad 300 is effective for
preventing such scratches.
[0079] Since the window 2 is recessed with respect to the pad body
10, the window 2 does not have grooves in a surface thereof even
when the pad body 10 has grooves 4 in a surface thereof. Therefore,
the light transmission noise caused by the slurry settling in the
grooves 4 can be prevented.
[0080] Since the window 2 is recessed with respect to the pad body
10, the window 2 does not need to be formed of a material
sufficiently susceptible to abrasion. Therefore, the window 2 can
be formed of a variety of material. For example, the material of
the window 2 can be selected from the viewpoint of
transparency.
[0081] Since the window 2 is recessed with respect to the pad body
10, a gap is made between the window 2 and a wafer. Thus, the
smooth dispersion of the slurry while the polishing operation is
promoted. This also prevents scratches of wafer surfaces.
[0082] The polishing pad 300 is produced as follows.
[0083] After the pad sheet including the pad body 10 and the window
2 is produced, the window 2 is gouged to form the recessed portion
6. The recessed portion 6 preferably has a depth of about 400 to
500 .mu.m. The recessed portion 6 preferably has a width and a
length which are respectively greater than the width and the length
of the window 2 by about 5 to 10 mm.
[0084] Among the above-listed substances usable for a polishing pad
according to the present invention, a polyurethane composition is
preferable. A preferable method for producing the polishing pad is
a prepolymer method or a one shot method.
[0085] According to a prepolymer method, first, a polyol component
and an isocyanate component are reacted with each other to form a
urethane prepolymer. Then, the resultant urethane prepolymer, a
diamine or a diol, a foaming agent and a catalyst are mixed to form
a urethane composition. The urethane composition is cured.
[0086] According to a one shot method, a polyol component, an
isocyanate component, a diamine or a diol, a foaming agent and a
catalyst are mixed to form a urethane composition. The urethane
composition is cured.
[0087] Examples of usable urethane prepolymer include
polyether-based urethane prepolymer, polyester-based urethane
prepolymer, and polyesterether-based urethane prepolymer.
EXAMPLE
[0088] Hereinafter, a specific example of the present invention
will be described.
[0089] A composition for the window 2 was prepared by mixing 3297 g
of a polyether-based urethane prepolymer (Uniroyal Adiprene L-325
available from Uniroyal Chemical) and 824 g of a curing agent
(MOCA; 3,3'-dichloro-4,4'-diaminodiphenylmethane).
[0090] The composition was injected into a mold and left at about
150.degree. F. for 15 minutes. Thus, a block of the composition for
the window 2 was produced.
[0091] A composition for the pad body 10 was prepared by mixing
3297 g of a polyether-based urethane prepolymer (Uniroyal Adiprene
L-325 available from Uniroyal Chemical) and 749 g of a curing agent
(MOCA; 3,3'-dichloro-4,4'-diaminodiphenylmethane).
[0092] The block of the composition for the window 2 was placed in
a mold and the composition for the pad body 10 was injected into
the mold. The block and the composition for the pad body 10 were
left at about 150.degree. F. for 15 minutes. The obtained molded
body was sliced into a prescribed thickness, thereby producing a
pad sheet.
[0093] The produced pad sheet was measured for the susceptibility
to abrasion by a polishing machine (Strasbaugh.cndot.6CA; diameter
of the board: 20 inches). The polishing was performed at a
seasoning pressure of 0.1 kgf/cm.sup.2, a rotation rate of a lower
board of 89 rpm, a rotation rate of the carrier for holding the
wafer mounted on an upper board of 60 rpm, and a supply of pure
water of 3,000 cm.sup.3/min. As the seasoning tool, R#80 (Kabushiki
Kaisha Fujimori Gijutsu Kenkyuusho) was used.
[0094] The results are shown in FIG. 10. FIG. 10 shows the
relationship between the final removed amount of the polished pad
and the seasoning time period. In FIG. 10, the "entrance" indicates
an area of the polishing pad 100 (FIG. 2) which is to the left of
an imaginary line extending from the window 2 to the V-shaped
cutout 8. The "exit" indicates an area of the polishing pad 100
(FIG. 2) which is to the right of an imaginary line extending from
the window 2 to the V-shaped cutout 8. As the lower board is
rotated, the polishing pad is polished by a seasoning tool always
in the order from the entrance to the window 2 and then to the
exit. The "outer periphery" indicates an outer circumferential edge
of the polishing pad 100, and the "center" indicates a central area
of the polishing pad 100.
Comparative Example
[0095] A polishing pad was produced in the same manner as in the
Example except that the window 2 was formed of the composition used
for forming the pad body 10.
[0096] The resultant pad sheet was measured for the susceptibility
to abrasion in the same manner as in the Example. The results are
shown in FIG. 11.
[0097] In the case of the pad sheet obtained in the Example (FIG.
10), as the polishing proceeds, the removed amount of the window 2
increases with respect to the removed amount of the pad body 10. In
the case of the pad sheet obtained in the comparative example (FIG.
11), the removed amount of the window 2 and the removed amount of
the pad body 10 are approximately the same even as the polishing
proceeds.
[0098] A polishing pad produced using the pad sheet obtained in the
Example and a polishing pad produced using the pad sheet obtained
in the comparative example were used for polishing wafers under the
conditions used for polishing silicon wafers with a conventional
polishing pad.
[0099] The grooves made in the window 2 caused noise in the case of
the polishing pad produced using the pad sheet obtained in the
comparative example, but not in the case of the polishing pad
produced using the pad sheet obtained in the Example.
[0100] Industrial Applicability
[0101] The present invention provides a polishing pad for
preventing a slurry from settling in a groove of a window and thus
raising the detection precision of the polishing rate, and for
preventing a window from gradually projecting from a pad body as a
result of dressing during polishing and thus improving the
polishing characteristic.
* * * * *