U.S. patent application number 10/449196 was filed with the patent office on 2004-01-22 for polishing pad and multi-layer polishing pad.
This patent application is currently assigned to JSR CORPORATION. Invention is credited to Hasegawa, Kou, Hosaka, Yukio, Kawahara, Kouji, Kawahashi, Nobuo, Koumura, Tomoo, Shiho, Hiroshi.
Application Number | 20040014413 10/449196 |
Document ID | / |
Family ID | 29554351 |
Filed Date | 2004-01-22 |
United States Patent
Application |
20040014413 |
Kind Code |
A1 |
Kawahashi, Nobuo ; et
al. |
January 22, 2004 |
Polishing pad and multi-layer polishing pad
Abstract
The present invention intends to provide a polishing pad and a
multi-layer polishing pad that can particularly effectively
suppress scratch from occurring. The polishing pad of the invention
comprises at least one part selected from a groove (a) having at
least one kind of shape selected from annular, lattice-like and
spiral form on a polishing surface side, a concave portion (b) and
a through hole (c). In the above, surface roughness of an inner
surface of the part is 20 .mu.m or less and the polishing pad is
used for chemical mechanical polishing.
Inventors: |
Kawahashi, Nobuo; (Mie,
JP) ; Hasegawa, Kou; (Mie, JP) ; Shiho,
Hiroshi; (Mie, JP) ; Koumura, Tomoo; (Mie,
JP) ; Kawahara, Kouji; (Mie, JP) ; Hosaka,
Yukio; (Mie, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JSR CORPORATION
Tokyo
JP
|
Family ID: |
29554351 |
Appl. No.: |
10/449196 |
Filed: |
June 2, 2003 |
Current U.S.
Class: |
451/527 |
Current CPC
Class: |
B24B 37/26 20130101 |
Class at
Publication: |
451/527 |
International
Class: |
B24D 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2002 |
JP |
2002-162142 |
Jun 28, 2002 |
JP |
2002-191401 |
Jun 28, 2002 |
JP |
2002-191402 |
Jun 28, 2002 |
JP |
2002-191403 |
Claims
What is claimed is:
1. A polishing pad comprising: at least one part selected from the
group consisting of a groove (a) having at least one kind of shape
selected from annular, lattice-like and spiral form on a polishing
surface side, a concave portion (b) and a through hole (c); wherein
surface roughness of an inner surface of said part is 20 .mu.m or
less; and wherein said polishing pad is used for chemical
mechanical polishing.
2. The polishing pad according to claim 1, wherein a depth of said
groove (a) is 0.1 mm or more and a width thereof is 0.1 mm or
more.
3. The polishing pad according to claim 1, wherein said groove (a)
is formed concentrically.
4. The polishing pad according to claim 1, wherein a depth of said
concave portion (b) is 0.1 mm or more, and a minimum length of an
opening thereof is 0.1 mm or more.
5. The polishing pad according to claim 1, wherein a minimum length
of an opening of said through hole (c) is 0.1 mm or more.
6. The polishing pad according to claim 1, wherein an area of an
opening of one said concave portion (b) is 0.0075 mm.sup.2 or
more.
7. The polishing pad according to claim 1, wherein an area of an
opening of one said through hole (c) is 0.0075 mm.sup.2 or
more.
8. The polishing pad according to claim 1, wherein a minimum length
between adjacent openings of each of said groove (a), said concave
portion (b) and said through hole (c) is 0.05 mm or more.
9. The polishing pad according to claim 1, wherein at least part of
said polishing pad comprises a water-insoluble matrix that contains
a crosslinked polymer and a water-soluble particle dispersed in
said water-insoluble matrix.
10. The polishing pad according to claim 1, wherein said groove
(a), said concave portion (b) and said through hole (c) are formed
by a method selected from cutting and die forming.
11. A multi-layer polishing pad comprising: a polishing layer
comprising at least one part selected from the group consisting of
a groove (a) having at least one kind of shape selected from
annular, lattice-like and spiral form on a polishing surface side,
a concave portion (b) and a through hole (c); wherein surface
roughness of an inner surface of said part is 20 .mu.m or less; and
a supporting layer laminated on a non-polishing surface side of
said polishing layer; wherein said multi-layer polishing pad is
used for chemical mechanical polishing.
12. The multi-layer polishing pad according to claim 11, wherein a
depth of said groove (a) is 0.1 mm or more and a width thereof is
0.1 mm or more.
13. The multi-layer polishing pad according to claim 11, wherein
said groove (a) is formed concentrically.
14. The multi-layer polishing pad according to claim 11, wherein a
depth of said concave portion (b) is 0.1 mm or more, and a minimum
length of an opening thereof is 0.1 mm or more.
15. The multi-layer polishing pad according to claim 11, wherein a
minimum length of an opening of said through hole (c) is 0.1 mm or
more.
16. The multi-layer polishing pad according to claim 11, wherein an
area of an opening of one said concave portion (b) is 0.0075
mm.sup.2 or more.
17. The multi-layer polishing pad according to claim 11, wherein an
area of an opening of one said through hole (c) is 0.0075 mm.sup.2
or more.
18. The multi-layer polishing pad according to claim 11, wherein a
minimum length between adjacent openings of each of said groove
(a), said concave portion (b) and said through hole (c) is 0.05 mm
or more.
19. The multi-layer polishing pad according to claim 11, wherein at
least part of said polishing layer comprises a water-insoluble
matrix that contains a crosslinked polymer and a water-soluble
particle dispersed in said water-insoluble matrix.
20. The multi-layer polishing pad according to claim 11, wherein
said groove (a), said concave portion (b) and said through hole (c)
are formed by a method selected from cutting and die forming.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing pad and a
multi-layer polishing pad. In more detail, the invention relates to
a polishing pad and a multi-layer polishing pad that have a groove
having a specific shape on a polishing surface side, or a concave
part having a specific shape that opens toward a polishing surface
side. The polishing pad and the multi-layer polishing pad of the
invention can be widely used in manufacture of semiconductor
devices, and particularly preferably used in chemical mechanical
polishing and the like of a surface of a material to be polished
such as a wafer.
[0003] 2. Description of the Prior Art
[0004] Recently, chemical mechanical polishing (CMP) attracts
attention as a polishing method that allows forming a surface
having excellent planarity. In the CMP, with a polishing pad and a
surface to be polished of a material to be polished sliding, a
slurry that is an aqueous dispersion therein abrasive is dispersed
is flowed from upward onto a surface of the polishing pad, and
thereby polishing is performed. In the CMP, it is known that a
polishing result is largely influenced depending on a state and
characteristics of the polishing pad.
[0005] Technique in which a removal rate and a polishing result can
be improved by disposing a groove on a surface of the polishing pad
is disclosed in JP-A H11-70463, H08-216029 and H08-39423. Even when
the technique is used, however, in some cases, scratch cannot be
sufficiently inhibited from being formed on a polished surface of a
material to be polished.
[0006] Furthermore, a polishing pad that can form pores on a
polishing surface of the polishing pad without using a foamed body,
is disclosed in JP-W No.8-500622, JP-A 2000-34416, 2000-33552 and
2001-334455. Even when these techniques are used, however, in some
cases, pores cannot be suppressed from being clogged by abrasive
and polishing wastages during polishing, or pores cannot be
suppressed from being clogged after dressing, and thereby, the
removal rate cannot be sufficiently improved. Still furthermore, in
some cases, the slurry cannot be sufficiently uniformly distributed
on the polishing pad; accordingly, the removal rate cannot be
sufficiently improved and a sufficiently uniform polished surface
cannot be obtained.
SUMMARY OF THE INVENTION
[0007] The present invention intends to overcome the above existing
problems and thereby to provide a polishing pad and a multi-layer
polishing pad that can particularly effectively suppress scratch
occurring.
[0008] The present invention is described as follows.
[0009] 1. A polishing pad comprising:
[0010] at least one part selected from the group consisting of a
groove (a) having at least one kind of shape selected from annular,
lattice-like and spiral form on a polishing surface side, a concave
portion (b) and a through hole (c):
[0011] wherein surface roughness of an inner surface of the part is
20 .mu.m or less; and
[0012] wherein the polishing pad is used for chemical mechanical
polishing.
[0013] 2. The polishing pad according to above 1, wherein a depth
of the groove (a) is 0.1 mm or more and a width thereof is 0.1 mm
or more.
[0014] 3. The polishing pad according to above 1, wherein the
groove (a) is formed concentrically.
[0015] 4. The polishing pad according to above 1, wherein a depth
of the concave portion (b) is 0.1 mm or more, and a minimum length
of an opening thereof is 0.1 mm or more.
[0016] 5. The polishing pad according to above 1, wherein a minimum
length of an opening of the through hole (c) is 0.1 mm or more.
[0017] 6. The polishing pad according to above 1, wherein an area
of an opening of one concave portion (b) is 0.0075 mm.sup.2 or
more.
[0018] 7. The polishing pad according to above 1, wherein an area
of an opening of one through hole (c) is 0.0075 mm.sup.2 or
more.
[0019] 8. The polishing pad according to above 1, wherein a minimum
length between adjacent openings of each of the groove (a), the
concave portion (b) and the through hole (c) is 0.05 mm or
more.
[0020] 9. The polishing pad according to above 1, wherein at least
part of the polishing pad comprises a water-insoluble matrix that
contains a crosslinked polymer and a water-soluble particle
dispersed in the water-insoluble matrix.
[0021] 10. The polishing pad according to above 1, wherein the
groove (a), the concave portion (b) and the through hole (c) are
formed by a method selected from cutting and die forming.
[0022] 11. A multi-layer polishing pad comprising:
[0023] a polishing layer comprising at least one part selected from
the group consisting of a groove (a) having at least one kind of
shape selected from annular, lattice-like and spiral form on a
polishing surface side, a concave portion (b) and a through hole
(c);
[0024] wherein surface roughness of an inner surface of the part is
20 .mu.m or less; and
[0025] a supporting layer laminated on a non-polishing surface side
of the polishing layer;
[0026] wherein the multi-layer polishing pad is used for chemical
mechanical polishing.
[0027] 12. The multi-layer polishing pad according to above 11,
wherein a depth of the groove (a) is 0.1 mm or more and a width
thereof is 0.1 mm or more.
[0028] 13. The multi-layer polishing pad according to above 11,
wherein the groove (a) is formed concentrically.
[0029] 14. The multi-layer polishing pad according to above 11,
wherein a depth of the concave portion (b) is 0.1 mm or more, and a
minimum length of an opening thereof is 0.1 mm or more.
[0030] 15. The multi-layer polishing pad according to above 11,
wherein a minimum length of an opening of the through hole (c) is
0.1 mm or more.
[0031] 16. The multi-layer polishing pad according to above 11,
wherein an area of an opening of one concave portion (b) is 0.0075
mm.sup.2 or more.
[0032] 17. The multi-layer polishing pad according to above 11,
wherein an area of an opening of one through hole (c) is 0.0075 mm
or more.
[0033] 18. The multi-layer polishing pad according to above 11,
wherein a minimum length between adjacent openings of each of the
groove (a), the concave portion (b) and the through hole (c) is
0.05 mm or more.
[0034] 19. The multi-layer polishing pad according to above 11,
wherein at least part of the polishing layer comprises a
water-insoluble matrix that contains a crosslinked polymer and a
water-soluble particle dispersed in the water-insoluble matrix.
[0035] 20. The multi-layer polishing pad according to above 11,
wherein the groove (a), the concave portion (b) and the through
hole (c) are formed by a method selected from cutting and die
forming.
[0036] According to the polishing pad of the invention, by
providing a groove (a) having a specific shape, a concave portion
(b) and a through hole (c), scratches owing to foreign matters
generated therein can be effectively suppressed from occurring, and
polished surface is excellent in planarity.
[0037] In addition, when the groove (a) has a specific depth and
width, the concave portion (b) a specific depth and minimum length
of an opening, and the through hole (c) a specific minimum length
of an opening, and furthermore when an area of one opening of the
concave portion (b) and that of the through hole (c) are 0.0075
mm.sup.2 or more, respectively, the scratch occurring can be more
assuredly suppressed.
[0038] Furthermore, when minimum lengths between adjacent openings
of the groove (a), the concave portion (b) and the through hole (c)
are 0.05 mm or more, efficient polishing can be forwarded while the
strength of a convex portion that corresponds to the polishing
surface is maintaining.
[0039] When at least part of the polishing pad includes a
water-insoluble matrix including a crosslinked polymer and a
water-soluble particle, surface roughness of an inner surface of
the groove (a), the concave portion (b) and the through hole (c)
can be easily suppressed to 20 .mu.m or less. Accordingly, the
pores are not clogged by dressing, the slurry is sufficiently held
and the removal rate can be made larger.
[0040] Furthermore, in case the groove (a), the concave portion (b)
and the through hole (c) are formed with a method selected from
cutting and molding, the surface roughness of the inner surface of
each part can be easily made smaller, resulting in sufficiently
suppressing the scratch from occurring.
[0041] According to the multi-layer polishing pad of the invention,
the polishing can be efficiently forwarded without deforming a
polishing layer during polishing. Furthermore, the scratch
occurring due to the foreign matters generated in the groove and
the like can be suppressed, and a polishing surface of the pad and
a surface to be polished of a wafer or the like can be sufficiently
brought into contact, accordingly, the removal rate can be
improved.
DETAILED DESCRIPTION OF THE INVENTION
[0042] In the following, the present invention will be
detailed.
[0043] A polishing pad of the present invention comprises at least
one part selected from the group consisting of a groove (a) having
at least one kind of shape selected from annular, lattice-like and
spiral form on a polishing surface side, a concave portion (b) and
a through hole (c).
[0044] The surface roughness of an inner surface of a groove (a), a
concave portion (b) and a through hole (c) provided to a polishing
pad of the invention is 20 .mu.m or less, preferably 15 .mu.m or
less, more preferably 10 .mu.m or less and particularly 7 .mu.m or
less. A lower limit thereof is normally 0.05 .mu.m. When the
surface roughness is 20 .mu.m or less, the scratch occurred during
polishing can be effectively inhibited from occurring. The surface
roughness means an averaged value (Ra) given by the sum of the
absolute values of all the areas above and below the mean line
divided by the sampling length and is measured by a measurement
method described below at least before the polishing pad of the
invention is used.
[0045] That the surface roughness Ra of the inner surface of the
groove (a), the concave portion (b) and the through hole (c) is 20
.mu.m or less means that there is no large unevenness therein. When
there is large unevenness, a particularly large convex portion
(made of, for instance, cutting residue generated when the groove
is formed) drops off during polishing, resulting in causing
scratches. Furthermore, foreign matters formed from the dropped off
convex portion by compressing or the like owing to a pressure and
friction heat during polishing, foreign matters formed from the
dropped off convex portion and polishing wastage, solid component
in the slurry and the like by interacting to form foreign matters
may occur the scratches in some cases. In addition, even during
dressing, in some cases, the convex portion may drops off,
resulting in the similar inconvenience.
[0046] When the surface roughness Ra is 20 .mu.m or less, in
addition to inhibiting the scratch from occurring, a function as
the groove (a), the concave portion (b) and the through hole (c), a
function of distributing the slurry on the polishing surface and a
function of exhausting waste outside can be particularly
efficiently exhibited.
[0047] The surface roughness Ra is an average value obtained by
measuring individual average values of the surface roughness of
different three viewing fields of a surface of a polishing pad
before use, with a measuring apparatus that can measure the surface
roughness, and by averaging three of the obtained average surface
roughness. The measuring apparatus being used is not particularly
limited, for instance, optical surface roughness measuring
apparatus such as a three-dimensional surface structure analytic
microscope, a scanning laser microscope, and an electron beam
surface morphology analysis instrument, and contact surface
roughness measuring apparatus such as a probe type surface
roughness meter can be used.
[0048] The groove (a) exists on a polishing surface side of the
polishing pad. The groove (a) has a function of retaining slurry
supplied during polishing and more uniformly distributing the
slurry on the polishing surface. In addition, it has a function as
an exhaustion path that temporarily stays waste such as polishing
wastage generated during polishing and used slurry, and exhausts
the waste outside of the system.
[0049] The groove (a) may have any shape selected from the group
consisting of an annular shape, a lattice-like shape and a spiral
shape. The polishing pad of the present invention may have one of
these separately or may have these in combination.
[0050] When the groove (a) is annularly formed, its planar shape is
not particularly limited and the shape may be, for instance, a
circular, a polygonal (trigonal, tetragonal, pentagonal and the
like), an elliptic and the like. The number of the grooves is
preferably two or more. Furthermore, although arrangement of these
grooves is not particularly limited, these may be, for instance, a
concentrically arrangement (concentric circle-like and the like)
with plural grooves 12 (FIG. 1), an eccentrically arrangement with
plural grooves 12 (FIG. 2), or in such a way that a plurality of
other annular grooves is arranged inside of a part surrounded by an
annular groove. Among these, one in which plural grooves are
concentrically arranged is preferable, and furthermore, one in
which plural grooves are concentric circularly arranged (a state in
which a plurality of circular grooves is concentrically arranged)
is more preferable. The polishing pad having the concentric
arrangement is superior to others in the above functions. In
addition, the polishing pad having the concentric circular
arrangement is more excellent in the above functions and the groove
thereof can be easily formed.
[0051] On the other hand, a sectional shape of the groove is not
particularly limited and may be, for instance, a shape formed of
flat side surfaces and a bottom surface (the length of the
respective width directions of an opening side and a bottom side
may be the same, or the opening side may be longer in the length
than the bottom side, or the bottom side may be longer in the
length than the opening side), a horseshoe shape, a V-shape and the
like.
[0052] When the groove (a) is annularly formed, its magnitude is
not particularly limited, and a width of the groove (22 in FIG. 3)
is preferably 0.1 mm or more, more preferably in the range of from
0.1 to 5 mm, and further more preferably in the range of from 0.2
to 3 mm. The groove having a width less than 0.1 mm is formed in
some cases with difficulty. On the other hand, a depth of the
groove is preferably 0.1 mm or more, more preferably in the range
of from 0.1 to 2.5 mm, and further more preferably in the range of
from 0.2 to 2.0 mm. When the depth of the groove is less than 0.1
mm, it is not preferable because the lifetime of the polishing pad
becomes excessively short. The depth of the groove may be different
depending on positions.
[0053] In addition, a minimum length between adjacent grooves (23
in FIG. 3) is preferably 0.05 mm or more, more preferably in the
range of from 0.05 to 100 mm, and more preferably from 0.1 to 10
mm. In some cases, it is difficult to form grooves having a minimum
length between the adjacent grooves of less than 0.05 mm.
Furthermore, a pitch (21 in FIG. 3) that is a sum of the width of
the groove and a length of a portion between adjacent grooves is
preferably 0.15 mm or more, more preferably in the range of from
0.15 to 105 mm, further more preferably from 0.3 to 13 mm, and
particularly preferably from 0.5 to 2.2 mm.
[0054] Each of the preferable ranges can combine with other
preferable ranges. That is, it is preferable, for instance, for the
width to be 0.1 mm or more, for the depth 0.1 mm or more, and for
the minimum length 0.05 mm or more; more preferable for the width
to be in the range of from 0.1 mm to 5 mm, for the depth from 0.1
to 2.5 mm, and for the minimum length from 0.05 to 100 mm; and
further more preferable for the width to be in the range of from
0.2 mm to 3 mm, for the depth from 0.2 to 2.0 mm, and for the
minimum length from 0.1 to 10 mm.
[0055] The width and depth of the annular grooves formed on a
polishing surface side of the polishing pad may be the same in the
respective grooves or may be different.
[0056] When the groove (a) is formed in lattice, it may be formed
of one continual groove or may be formed of two or more
discontinuous grooves. Furthermore, a planar shape of one pattern
that forms the lattice, not particularly limited, may be formed
into various polygons. As the polygons, for instance, tetragons
such as a square (FIG. 4), a rectangle, a trapezoid, and a lozenge
(FIG. 5), a triangle (FIG. 6), a pentagon, and a hexagon can be
cited. A sectional shape of the groove may be the same as that of
the annular one.
[0057] When the groove (a) is formed in lattice, its magnitudes can
be also the same as those of the annular one.
[0058] When a planar shape of one pattern that forms a lattice is a
square, a minimum length between adjacent grooves (23 in FIG. 3) is
preferably 0.05 mm or more, more preferably in the range of from
0.05 to 100 mm, and further more preferably from 0.1 to 10 mm. A
lattice-like groove having the minimum length of less than 0.05 mm
is in some cases formed with difficulty. Furthermore, a pitch that
is a sum of the width of the groove and a length of a portion
between adjacent grooves (21 in FIG. 3) is, in both of a vertical
direction and a lateral direction, preferably 0.15 mm or more, more
preferably in the range of from 0.15 to 105 mm, further more
preferably from 0.3 to 13 mm, and particularly preferably from 0.5
to 2.2 mm. However, a pitch in the vertical direction and that in
the lateral direction may be the same or different. Furthermore,
when the tetragon is a lozenge, the shorter one of lengths of two
pairs of parallel sides that face each other is taken as the
minimum length.
[0059] Each of the preferable ranges of the magnitudes of the
groove can combine with other preferable ranges. That is, it is
preferable, for instance, for the width to be 0.1 mm or more, for
the depth 0.1 mm or more, and for the minimum length 0.05 mm or
more; more preferable for the width to be in the range of from 0.1
mm to 5 mm, for the depth from 0.1 to 2.5 mm, and for the minimum
length from 0.05 to 100 mm; and further more preferable for the
width to be in the range of from 0.2 mm to 3 mm, for the depth from
0.2 to 2.0 mm, and for the minimum length from 0.1 to 10 mm.
[0060] Furthermore, when a planar shape of one pattern that forms a
lattice is a triangle, a length of the smallest side of the
triangle is preferably 0.05 mm or more, more preferably in the
range of from 0.05 to 100 mm, and further more preferably from 0.1
to 10 mm. When a length of the smallest side is less than 0.05 mm,
a lattice-like groove can be in some cases formed with
difficulty.
[0061] Each of the preferable ranges of the magnitudes of the
groove can combine with other preferable ranges. That is, it is
preferable, for instance, for the width to be 0.1 mm or more, for
the depth 0.1 mm or more, and for the length of the smallest side
0.05 mm or more; more preferable for the width to be in the range
of from 0.1 mm to 5 mm, for the depth from 0.1 to 2.5 mm, and for
the length of the smallest side from 0.05 to 100 mm; and further
more preferable for the width to be in the range of from 0.2 mm to
3 mm, for the depth from 0.2 to 2.0 mm, and for the length of the
smallest side from 0.1 to 10 mm.
[0062] In addition, when a planar shape of one pattern that forms a
lattice is a hexagon, a minimum length that is the shortest of
parallel sides that face each other is preferably 0.05 mm or more,
more preferably in the range of from 0.05 to 100 mm, and further
more preferably from 0.1 to 10 mm. A lattice-like groove whose
minimum length is less than 0.05 mm is in some cases formed with
difficulty.
[0063] Each of the preferable ranges can combine with other
preferable ranges. That is, it is preferable, for instance, for the
width to be 0.1 mm or more, for the depth 0.1 mm or more, and for
the smallest length 0.05 mm or more; more preferable for the width
to be in the range of from 0.1 mm to 5 mm, for the depth from 0.1
to 2.5 mm, and for the smallest length from 0.05 to 100 mm; and
further more preferable for the width to be in the range of from
0.2 mm to 3 mm, for the depth from 0.2 to 2.0 mm, and for the
smallest length from 0.1 to 10 mm.
[0064] The lattice-like grooves formed on a polishing surface side
of the polishing pad may be formed of one kind of grooves the same
in the width and depth, respectively, or may be formed of a
combination of two or more kinds of grooves different in the width
and the depth. Furthermore, the polishing surface may be provided
thereon with only one kind of lattice-like grooves the same in a
planar shape of one pattern that forms the lattice, or may be
provided with two or more kinds of lattice-like grooves different
in the planar shape.
[0065] When the groove (a) is spirally formed, it may be formed of
one continuous groove 12 (FIG. 7), or may be formed of two spiral
grooves 12a and 12b whose spiral directions are different each
other (FIG. 8). Furthermore, it may be formed of two spiral grooves
whose spiral directions are the same, or may be formed of three or
more spiral grooves whose spiral directions are the same each other
or different from each other. A sectional shape of the groove may
be the same as that of the annular one. And when the groove (a) is
spirally formed, its magnitudes can be also the same as those of
the annular one. In addition, a minimum length between adjacent
grooves and a pitch can be also the same as those of the annular
one.
[0066] The width and depth of the spiral groove formed on the
polishing surface side of the polishing pad may be the same over
all length or different. Furthermore, when two or more grooves are
formed, the width and the depth of the respective grooves may be
the same or different.
[0067] The "concave portion (b)" exists on a polishing surface side
of the polishing pad. Furthermore, the "through hole (c)" is opened
toward both surfaces of the polishing surface and a surface
opposite to the polishing surface. The concave portion (b) or the
through hole (c) (hereinafter, in some cases, referred to as
"concave portion and the like") has a function of retaining the
slurry supplied during polishing and more uniformly distributing
the slurry on the polishing surface. Furthermore, the concave
portion and the like has a function of an exhaustion path that
allows waste such as polishing wastage generated during polishing
and used slurry to temporarily stay and exhausts the waste outside
of the system. Even when the polishing pad has the through holes,
by fixing the polishing pad to a surface plate of polishing
apparatus owing to depression or the like, the slurry does not
outflow through the through holes without serving to polishing.
[0068] A planar shape of the concave portions and the like is not
particularly limited, but may be, for instance, a circle, a polygon
(trigon, tetragon, pentagon and the like), an ellipse and the like.
An arrangement of openings of the concave portions and the like on
the polishing surface is neither limited, but the openings are
preferable to be uniformly arranged over an entire surface of the
polishing surface. As a specific example of the polishing pad that
has the concave portions or the like, one in which on the polishing
surface thereof the concave portions 13 and the like having a
circular planar shape are uniformly opened (FIG. 9) can be cited. A
sectional shape of the concave portions or the like is not
particularly limited, but may be, for instance, one formed of flat
side surfaces and bottom surface (In the case of the concave
portion, the length of the respective horizontal sectional
directions of an opening side and a bottom side may be the same, or
the opening side may be longer in the length than the bottom side,
or the bottom side may be longer in the length than the opening
side. Furthermore, in the case of the through hole, length of the
respective horizontal directions of one opening side and the other
opening side may be the same, or the length of the polishing
surface side may be longer, or the length of the opposite surface
side may be longer.), a horseshoe shape, a V-shape, and the
like.
[0069] The magnitude of the concave portions or the like is not
particularly limited, but it may be, when the planar shape is, for
instance, circular one, a diameter thereof, and when the planar
shape is at least one selected from a polygon, an ellipse and the
like, the minimum length of the opening (25 in FIG. 10) is
preferably 0.1 mm or more, more preferably in the range of from 0.1
to 5 mm, and further more preferably from 0.2 to 3 mm. Usually, it
tends to be difficult to form the concave portion or the like whose
diameter or the minimum length is less than 0.1 mm. Furthermore,
the depth of the concave portion or the like is preferably 0.1 mm
or more, more preferably in the range of from 0.1 to 2.5 mm, and
further more preferably from 0.2 to 2.0 mm. The depth of the
concave portion or the like being less than 0.1 mm is not
preferable because the excessively short lifetime of the polishing
pad results. Still furthermore, for a separation of the concave
portions or the like, the smallest length between adjacent concave
portions or the like (26 in FIG. 10) is preferably 0.05 mm or more,
more preferably in the range of from 0.05 to 100 mm, and further
more preferably from 0.1 to 10 mm. It also tends to be difficult to
form the concave portion or the like whose smallest length is less
than 0.05 mm. Furthermore, a pitch that is a sum of the minimum
length of the opening of the concave portion or the like and a
length of a portion between adjacent concave portions or the like
(26 in FIG. 10) is preferably 0.15 mm or more, more preferably in
the range of from 0.15 to 105 mm, further more preferably from 0.3
to 13 mm, and particularly from 0.5 to 2.2 mm.
[0070] Each of the preferable ranges can combine with other
preferable ranges. That is, it is preferable, for instance, for the
minimum length of the opening to be 0.1 mm or more, for the depth
0.1 mm or more, and for the smallest length between the adjacent
concave portions or the like 0.05 mm or more; more preferable for
the minimum length of the opening to be in the range of from 0.1 mm
to 5 mm, for the depth from 0.1 to 2.5 mm, and for the smallest
length between the concave portions or the like from 0.05 to 100
mm; and further more preferable for the minimum length in a planar
direction to be in the range of from 0.2 mm to 3 mm, for the depth
from 0.2 to 2.0 mm, and for the smallest length between the
adjacent concave portions or the like from 0.1 to 10 mm.
[0071] The concave portion (b) is 0.0075 mm.sup.2 or more in an
area of an opening at the surface of the polishing pad, more
preferably 0.01 mm.sup.2, further more preferably 1 mm.sup.2 or
more, and normally 100 mm.sup.2 or less. Since the area of the
opening is 0.0075 mm.sup.2 or more, the slurry supplied during
polishing can be sufficiently retained, and waste such as the
polishing wastage that is generated owing to the polishing and the
used slurry can be allowed to temporarily stay and can be easily
exhausted outside.
[0072] The planar shapes, the minimum length of the opening, and
the depths of the concave portions or the like opened toward the
polishing surface side and the like may be same or may be varied.
In addition, the concave portions or the like may be formed with a
uniform separation over an entire polishing surface, or may not be
uniformly formed; however, in order to stably perform the
polishing, these are preferably uniformly formed. The polishing pad
of the invention can comprise a groove having a various shape
described above in addition to the concave portions or the
like.
[0073] The polishing pad of the invention may be formed of whatever
materials as far as the functions as the polishing pad can be
exhibited. However, among the functions as the polishing pad,
particularly, it is preferable for pores that has a function of
retaining the slurry during polishing and allowing the wastage to
temporarily stay to have been formed up to the time of polishing.
Accordingly, the polishing pad is preferably provided with a
water-insoluble matrix and a water-soluble particle dispersed in
the water-insoluble matrix, or with a water-insoluble matrix
therein vacancies are dispersingly formed (foamed body and the
like).
[0074] Of these, in the former, the water-soluble particles are
brought into contact with a water-based medium component of the
slurry (containing a medium component and a solid component) during
polishing, dissolve or swell, resulting in dropping-off. The slurry
is retained in the pores formed because of the dropping-off. On the
other hand, in the latter, the slurry is retained in the pores
previously formed as the vacancies.
[0075] A material that constitutes the "water-insoluble matrix" is
not particularly limited. In view of being easy to mold into a
predetermined shape, property and state, and being capable of
endowing appropriate hardness and appropriate elasticity, it is
usual to use an organic material. As the organic material,
thermoplastic resins, elastomers, rubbers (crosslinked rubbers) and
curable resins (resins cured owing to heat, light and the like such
as thermo-setting resins and photo-setting resins) can be used
alone or in combination.
[0076] Among these, as the thermoplastic resins, 1,2-polybutadiene
resin, polyolefinic resins such as polyethylene, polystyrene-based
resins, polyacrylic resins such as (meth)acrylate-based resins,
vinylester-based resins (except for acrylic-based resins),
polyester-based resins, polyamide-based resins, fluorinated resins
such as polyvinylidene fluoride, polycarbonate resins and
polyacetal resins can be cited.
[0077] As the elastomers, diene-based elastomers such as
1,2-polybutadiene, polyolefinic elastomers (TPO), styrene-based
elastomers such as styrene-butadiene-styrene block copolymers (SBS)
and hydrogenated block copolymers thereof (SEBS), thermoplastic
elastomers such as thermoplastic polyurethane-based elastomers
(TPU), thermoplastic polyester-based elastomers (TPEE), and
polyamide-based elastomers (TPAE), silicone resin-based elastomers,
fluorinated resin-based elastomers and the like can be cited.
[0078] As the rubbers, conjugated diene-based rubbers such as
butadiene-based rubbers (high-cis butadiene rubber, low-cis
butadiene rubber and the like), isoprene-based rubbers,
styrene-butadiene-based rubbers and styrene-isoprene-based rubbers,
nitrile-based rubbers such as acrylonitrile-butadiene-based rubbers
and the like, acrylic rubbers, ethylene-.alpha.-olefin-based
rubbers such as ethylene-propylene-based rubbers,
ethylene-propylene-diene-based rubbers, and other rubbers such as
butyl rubbers, silicone rubbers and fluororubbers can be cited.
[0079] As the curable resins, urethane-based resins, epoxy-based
resins, acrylic resins, unsaturated polyester-based resins,
polyurethane-urea-based resins, urea-based resins, silicone-based
resins, phenol-based resins, vinylester-based and the like resin
can be cited.
[0080] Furthermore, the organic material may be modified with an
acid anhydride group, a carboxyl group, a hydroxyl group, an epoxy
group, an amino group and the like. By modifying, the organic
material can be controlled in its affinity with the water-soluble
particles and the slurry.
[0081] The organic materials above can be used alone or in
combinations of two or more kinds.
[0082] Furthermore, the organic material may be a crosslinked
polymer that is partially or entirely crosslinked, or may be a
non-crosslinked polymer. Accordingly, the water-insoluble matrix
may be formed of a crosslinked polymer alone, a mixture of a
crosslinked polymer and a non-crosslinked polymer, or a
non-crosslinked polymer alone. However, it is preferable to contain
the crosslinked polymer (the crosslinked polymer alone, or the
mixture of the crosslinked polymer and the non-crosslinked
polymer). When the crosslinked polymer is contained, surface
roughness Ra of the inner surface of the groove (a), the concave
portion (b) and the through hole (c) can be easily suppressed to 20
.mu.m or less, and, at the same time, the water-insoluble matrix is
endowed with an elastic recovering force; accordingly, a
displacement due to the shearing-stress applied on the polishing
pad during polishing can be suppressed small. Furthermore, the
water-insoluble matrix can be effectively suppressed from being
excessively elongated and plastic-deformed to bury the pores during
polishing and dressing, and furthermore, a surface of the polishing
pad can be effectively suppressed from becoming excessively fluffy.
Accordingly, even during dressing, the pores can be effectively
formed, and the slurry retaining power during polishing can be
inhibited from deteriorating. Furthermore, since the surface of the
polishing pad is less fluffy, the polishing flatness is not
disturbed. A method of the crosslinking is not particularly
limited; that is, chemical crosslinking with organic peroxide,
sulfur, and sulfur compounds, radiation crosslinking due to
electron beam or the like can be applied.
[0083] As the crosslinked polymer, among the organic material
above, crosslinked rubbers, curable rubbers, crosslinked
thermoplastic resins and crosslinked elastomers can be used. Among
these, in view of being stable to strong acids and strong alkalis
contained in many slurries and being less in the softening due to
water absorption, one or both of the crosslinked thermoplastic
resins and crosslinked elastomers are preferable. Furthermore,
among the crosslinked thermoplastic resins and crosslinked
elastomers, ones that are crosslinked with organic peroxide are
particularly preferable, and furthermore crosslinked
1,2-polybutadiene is more preferable. With these, the groove (a),
the concave portion (b) and the through hole (c) whose surface
roughness Ra is 20 .mu.m or less can be easily formed.
[0084] A content of the crosslinked polymer is not particularly
limited. It is preferably contained by 30% by volume or more, more
preferably 50% by volume or more, further more preferably 70% by
volume or more, and may be 100% by volume relative to an entirety
of the water-insoluble matrix. When the content of the crosslinked
polymer in the water-insoluble matrix is less than 30% by volume,
in some cases, an effect of containing the crosslinked polymer
cannot be sufficiently exhibited.
[0085] The water-insoluble matrix containing the crosslinked
polymer, when a specimen made of the water-insoluble matrix is
broken at 80.degree. C. according to JIS K 6251, can make the
elongation that remains after the breaking (hereinafter, simply
referred to as "elongation remaining after breaking") 100% or less.
That is, a total length between markers after the breaking is two
times or less a length between markers before the breaking. The
elongation remaining after breaking is preferably 30% or less, more
preferably 10% or less, particularly preferably 5% or less, and
normally 0% more. When the elongation remaining after breaking
exceeds 100%, fine fragments scraped or stretched out from a
surface of the polishing pad during polishing or dressing
unfavorably tend to clog the pores. When, according to JIS K 6251
"Elongation Test Method of Vulcanized Rubber", with a test sample
having a shape of dumbbell No. 3, and under the conditions of a
pulling rate of 500 mm/min and a test temperature of 80.degree. C.,
a test sample is broken, the "elongation remaining after breaking"
is defined as an elongation rate of a length that is obtained by
subtracting a length between markers before the test from a total
length of the respective lengths from the markers to the broken
portion of the test sample that are separated by the breaking to
the length between markers before the test. Furthermore, in actual
polishing, there is heat generation due to the sliding;
accordingly, the test is carried out at 80.degree. C.
[0086] The "water-soluble particle" is a particle that drops off
from-the water-insoluble matrix when the polishing pad comes into
contact, in the polishing pad, with the slurry that is an aqueous
dispersion. The dropping-off may be caused by dissolving when the
water-soluble particles come into contact with water or the like
contained in the slurry, or may be caused by swelling and becoming
gel-like when the water-soluble particles contain water and the
like. Furthermore, the dissolution or the swelling may be caused
not only by contact with water but also with an aqueous mixture
medium containing an alcoholic solvent such as methanol.
[0087] The water-soluble particles have, other than the effect of
forming the pores, in the polishing pad, another effect of making
the indentation hardness of the polishing pad larger and thereby
making an amount of indentation of the material to be polished due
to the depression smaller. That is, when the polishing pad
according to the invention contains the water-soluble particles,
the Shore D hardness thereof can be made preferably 35 or more,
more preferably in the range of from 50 to 90, further more
preferably from 60 to 85, and usually 100 or less. When the Shore D
hardness is 35 or more, a pressure that can be applied on the
material to be polished can be made larger, and accompanying this,
the removal rate can be improved. In further addition to this, the
high polishing flatness can be obtained. Accordingly, the
water-soluble particles are particularly preferable to be solid
body that can secure sufficient indentation hardness in the
polishing pad.
[0088] A material that constitutes the water-soluble particle is
not particularly limited. And an organic water-soluble particle and
an inorganic water-soluble particle can be cited. As the organic
water-soluble particle, one that is made of saccharides
(polysaccharides such as starch, dextrin and cyclodextrin, lactose,
mannite and the like), celluloses (hydroxypropyl cellulose, methyl
cellulose and the like), proteins, polyvinyl alcohol, polyvinyl
pyrrolidone, polyacrylic acids and their salts, polyethylene oxide,
water-soluble photosensitive resins, sulfonated polyisoprene,
sulfonated polyisoprene copolymers and the like can be cited. In
addition, as the inorganic water-soluble particle, one made of
potassium acetate, potassium nitrate, potassium carbonate,
potassium hydrogen carbonate, potassium chloride, potassium
bromide, potassium phosphate, magnesium nitrate and the like can be
cited. The material constituting water-soluble particles may be
used alone or in combination of two or more kinds. Furthermore, the
water-soluble particles may be one kind of water-soluble particles
made of a predetermined material or two or more kinds of
water-soluble particles made of different materials.
[0089] An average particle diameter of the water-soluble particle
is preferably in the range of from 0.1 to 500 .mu.m, more
preferably from 0.5 to 100 .mu.m, and further more preferably from
1 to 50 .mu.m. That is, the magnitude of the pores is preferably in
the range of from 0.1 to 500 .mu.m, more preferably from 0.5 to 100
.mu.m, and further more preferably from 1 to 50 .mu.m. When the
average particle diameter of the water-soluble particle is less
than 0.1 .mu.m, the magnitude of the formed pores becomes smaller
than the abrasive to be used; accordingly, the polishing pad that
can sufficiently retain the slurry becomes difficult to obtain. On
the other hand, when the average particle diameter exceeds 500
.mu.m, the magnitude of the pores to be formed becomes excessively
large; as a result, the mechanical strength and the removal rate of
the obtained polishing pad tend to deteriorate.
[0090] The water-soluble particle may not be contained. A content
of the water-soluble particles in using is preferably in the range
of from 0.1 to 90% by volume, more preferably in the range of from
10 to 60% by volume, and further more preferably from 20 to 40% by
volume based on 100% by volume of a total of the water-insoluble
matrix and the water-soluble particle. When the content of the
water-soluble particle is less than 0.1% by volume, the pores
formed using the obtained polishing pad cannot be not be
sufficient, and the removal rate tends to decrease. On the other
hand, when the water-soluble particles are contained exceeding 90%
by volume, it tends to be difficult to sufficiently inhibit the
water-soluble particle present within the polishing pad from
swelling or dissolving; accordingly, it becomes difficult to
maintain the hardness and the mechanical strength of the polishing
pad at proper values.
[0091] Furthermore, the water-soluble particles are preferable to
be dissolved in water only when exposed on a surface layer in the
polishing pad, and not to absorb moisture and further swell when
being within the polishing pad. Accordingly, at least part of the
outermost part of the water-soluble particle may be provided with
an outer shell that can suppress the moisture absorption. The outer
shell may be physically absorbed by the water-soluble particle, or
may form a chemical bond with the water-soluble particle, or may
come into contact with the water-soluble particle through both of
the above. As a material that constitutes such outer shell, epoxy
resin, polyimide, polyamide, polysilicate and the like can be
cited. The outer shell, even when only part of the water-soluble
particle is provided therewith, can exhibit sufficiently the
effect.
[0092] The water-insoluble matrix, in order to control affinity
with the water-soluble particles and the dispersion properties of
the water-soluble particles in the water-insoluble matrix, may
contain a compatibilizing agent. As the compatibilizing agent, a
polymer that is modified by an acid anhydride group, carboxyl
group, hydroxyl group, epoxy group, oxazoline group, amino group
and the like, a block copolymer, a random copolymer, furthermore,
various kinds of a nonionic surfactant, a coupling agent and the
like can be cited.
[0093] Furthermore, the water-insoluble matrix can contain, other
than the compatibilizing agent, one kind or two or more kinds of
abrasive, oxidizer, hydroxide of alkali metal, acid, pH controller,
surfactant and anti-scratch agent that have been so far contained.
Still furthermore, the water-insoluble matrix may contain a salt
that forms an acid when used. Thereby, by supplying water alone,
the polishing can be carried out.
[0094] As the abrasive, particles made of silica, alumina, ceria,
zirconia, titania and the like can be cited. One kind or two or
more kinds of these can be used.
[0095] As the oxidizer, hydrogen peroxide, peracetic acid,
perbenzoic acid, organic peroxides such as tert-butyl
hydroperoxide, permanganates such as potassium permanganate,
dichromates such as potassium dichromate, halogen acid compounds
such as potassium iodate, nitrates such as nitric acid and iron
nitrate, perhalogen acid compounds such as perchloric acid,
persulfate such as ammonium persulfate, heteropolyacids and the
like can be cited. Among these oxidizers, other than hydrogen
peroxide and organic peroxides whose decomposition products are not
harmful, persulfate such as ammonium persulfate is particularly
preferable. One kind or two or more kinds thereof can be used.
[0096] As the hydroxide of alkali metals, sodium hydroxide,
potassium hydroxide, rubidium hydroxide, cesium hydroxide and the
like can be cited. One kind or two or more kinds of these can be
used.
[0097] As the acid, an organic acid and an inorganic acid can be
cited. Among these, as the organic acid, para-toluene sulfonic
acid, dodecyl-benzene sulfonic acid, isoprene sulfonic 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, phthalic acid and the like can be
cited. Furthermore, as the inorganic acid, nitric acid,
hydrochloric acid, sulfuric acid and the like can be cited. One
kind or two or more kinds of these can be used.
[0098] As the salt, ammonium salts, alkali metal salts such as
sodium salts and potassium salts, and alkali earth metal salts such
as calcium salts and magnesium salts of the above acids can be
cited. One kind or two or more kinds of these can be used.
[0099] As the surfactant, a cationic surfactant, an anionic
surfactant and the like can be cited. Of these, as the anionic
surfactant, carboxylates such as fatty acid soaps and alkyl ether
carboxylate, sulfonates such as alkyl benzene sulfonates, alkyl
naphthalene sulfonates and a-olefin sulfonates, sulfuric ester
salts such as sulfuric ester salt of higher alcohol, alkyl ether
sulfates, polyoxyethylene alkylphenyl ether sulfates, and
phosphoric ester salts such as alkyl phosphoric ester salt and the
like can be cited. One kind or two or more kinds of these can be
used.
[0100] As the anti-scratch agent, bisphenol, bipyridyl,
2-vinylpyridine, 4-vinylpyridine, salicylaldoxime,
o-phenylenediamine, m-phenylenediamine, catechol, o-aminophenol,
thiourea, N-alkyl group-containing (meth)acrylamide, N-aminoalkyl
group-containing (meth acrylamide,
7-hydroxy-5-methyl-1,3,4-triazaindolizine,
5-methyl-lH-benzotriazole, phthalazine, melamine,
3-amino-5,6-dimethyl-1,2,4-triazine and the like can be cited. One
kind or two or more kinds of these can be used.
[0101] Furthermore, the water-insoluble matrix can contain, other
than the compatibilizing agent and the various kinds of materials
that have been so far contained in the slurry, various kinds of
additives such as a filler, softener, anti-oxidizer, UV-absorber,
anti-static agent, lubricant and plasticizer. Among these, as a
material constituting the filler, materials that can improve the
rigidity such as calcium carbonate, magnesium carbonate, talc and
clay, and materials that have polishing effect such as silica,
alumina, ceria, zirconia, titanium oxide, manganese dioxide,
manganese sesquioxide, and barium carbonate may be used.
[0102] A shape of the polishing pad of the invention is not
particularly limited, and can be formed into, for instance, a
disc-like one, a belt-like one, and a roller-like one; it is
preferable to appropriately select according to polishing
apparatus. In addition, a magnitude of the polishing pad before
polishing is not particularly limited and in case of using a
disc-like polishing pad, for instance, a diameter can be formed in
the range of from 0.5 to 500 cm, more preferably in the range of
from 1.0 to 250 cm, and particularly preferably from 20 to 200 cm,
and a thickness can be made more than 0.1 mm and 100 mm or less,
particularly in the range of from 1 to 10 mm.
[0103] Neither a manufacturing method of the polishing pad of the
invention nor a method for forming a grove (a), a concave portion
(b) and a through hole (c) that the polishing pad has is
particularly limited. For instance, a composition for polishing pad
that becomes a polishing pad is obtained in advance; the
composition is formed into a desired rough shape; and thereafter,
the groove (a), the concave portion (b) and the through hole (c)
can be formed according to the cutting. Furthermore, when the
composition is molded with a die on which a pattern that becomes a
groove (a), a concave portion (b) and a through hole (c) is formed,
a rough shape of the polishing pad and the groove (a), the concave
portion (b) and the through hole (c) can be simultaneously formed.
Still furthermore, these cutting and die molding may be in
combination. According to the cutting and the die molding, surface
roughness Ra of an inner surface of the groove (a), the concave
portion (b) and the through hole (c) can be easily made 20 .mu.m or
less. When the polishing pad is one in which vacancies are
dispersed in the water-insoluble matrix such as a foamed body, in
the die molding, normally, a skin layer is formed on a surface, and
the pores are not formed; accordingly, it cannot be used as a
polishing pad.
[0104] A method of obtaining the composition for polishing pad is
not particularly limited. It can be obtained by, for instance,
kneading necessary materials such as predetermined organic
materials by use of a kneading machine. As the kneading machine,
one that has been known can be used. For instance, the kneading
machine such as a roller, a kneader, Banbary mixer, an extruder
(single shaft, multi-shaft) and the like can be cited.
[0105] The composition that contains the water-soluble particle can
be obtained by kneading, for instance, the water-insoluble matrix,
the water-soluble particle and other additives. In order to allow
easily working at kneading, these materials are usually heated and
kneaded. At a temperature at that time, the water-soluble particle
is preferably solid. When the water-soluble particle is solid,
irrespective of a magnitude of the compatibility with the
water-insoluble matrix, these can be dispersed with the preferable
average diameter. Accordingly, it is preferable to select, in
accordance with a working temperature of the water-insoluble matrix
to be used, a kind of the water-soluble particle.
[0106] A multi-layer polishing pad of the present invention
comprises a polishing layer comprising at least one part selected
from the group consisting of a groove (a) having at least one kind
of shape selected from annular, lattice-like and spiral form on a
polishing surface side, a concave portion (b) and a through hole
(c), in which the surface roughness Ra of an inner surface of the
part is 20 .mu.m or less, and a supporting layer laminated on a
non-polishing surface side of the polishing layer.
[0107] As modes of the present multi-layer polishing pad, (1) one
provided with a polishing layer that includes only a groove (a)
having at least one shape selected from an annular, a lattice-like
and a spiral and whose inner surface has the surface roughness Ra
of 20 .mu.m or less, and a supporting layer disposed on a
non-polishing surface side of the polishing layer, (2) one provided
with a polishing layer that includes only a concave portion (b)
whose inner surface has the surface roughness Ra of 20 .mu.m or
less, and a supporting layer disposed on a non-polishing surface
side of the polishing layer, (3) one provided with a polishing
layer that includes only a through hole (c) whose inner surface has
the surface roughness Ra of 20 .mu.m or less, and a supporting
layer disposed on a non-polishing surface side of the polishing
layer, and (4) one provided with a polishing layer that includes at
least two portions selected from a groove (a), a concave portion
(b) and a through hole (c) whose inner surfaces have the surface
roughness Ra of 20 .mu.m or less, and a supporting layer disposed
on a non-polishing surface side of the polishing layer, and the
like can be cited.
[0108] As the polishing layer of the multi-layer polishing pad of
the invention, the polishing pad of the invention above can be
applied.
[0109] The supporting layer is a layer that supports the polishing
layer and the like on a non-polishing surface side of the polishing
layer. The supporting layer is not particularly limited in the
characteristics, and it is preferable to be softer than the
polishing layer. When the supporting layer is made softer, even
when a thickness of the polishing layer is thin (for instance, 5 mm
or less), the polishing layer is inhibited from rising or a surface
of the polishing layer from curving during polishing; resulting in
stable polishing. The hardness of the supporting layer is
preferably 90% or less of that of the polishing layer, more
preferably 80% or less, particularly 70% or less, and normally 10%
or more.
[0110] Furthermore, the Shore D hardness is preferably 70 or less
(more preferably 60 or less, and further more preferably 50 or
less).
[0111] In addition, the supporting layer may be a porous body
(foamed body) or a non-porous body. Furthermore, its planar shape
is not particularly limited, and may be the same as the polishing
layer or different from the polishing layer. As a planar shape of
the supporting layer, for instance, a circle, a polygon (tetragon
and the like) and the like can be adopted. Furthermore, a thickness
of the supporting layer is neither particularly limited, but it can
be made, for instance, in the range of from 0.1 to 5 mm, more
preferably in the range of from 0.5 to 2 mm.
[0112] A material that constitutes the supporting layer is not
particularly limited. In view of easiness to form a predetermined
shape and state and capability of endowing appropriate elasticity,
an organic material is preferably used. As the organic material,
the organic materials that constitute the water-insoluble matrix in
the polishing pad above can be applied. However, the organic
material that constitutes the supporting layer may be a crosslinked
polymer or a non-crosslinked polymer.
[0113] The multi-layer polishing pad may be provided with only one
supporting layer or two or more layers. In addition, the supporting
layer and the polishing layer may be directly laminated or may be
laminated through another layer. Furthermore, the supporting layer
may be adhered to the polishing layer or other layer with an
adhesive, an adhesive material (adhesive tape and the like) and the
like, or may be integrally bonded thereto by partially fusing.
[0114] The present polishing pad and the multi-layer polishing pad
may be provided with a hole, a window and the like for end-point
detection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0115] FIG. 1 is a schematic plan view showing one example of a
polishing pad of the invention.
[0116] FIG. 2 is a schematic plan view showing another example of a
polishing pad of the invention.
[0117] FIG. 3 is a schematic diagram of a partial cross section
including a groove of the polishing pad of the invention.
[0118] FIG. 4 is a schematic plan view showing another example of a
polishing pad of the invention.
[0119] FIG. 5 is a schematic plan view showing another example of a
polishing pad of the invention.
[0120] FIG. 6 is a schematic plan view showing another example of a
polishing pad of the invention.
[0121] FIG. 7 is a schematic plan view showing another example of a
polishing pad of the invention.
[0122] FIG. 8 is a schematic plan view showing another example of a
polishing pad of the invention.
[0123] FIG. 9 is a schematic plan view showing another example of a
polishing pad of the invention.
[0124] FIG. 10 is a schematic diagram of a partial cross section
including a concave portion of the polishing pad of the
invention.
[0125] FIG. 11 is an explanatory diagram due to a micrograph image
of a partial section of the polishing pad according to Example
1-1.
[0126] FIG. 12 is an explanatory diagram due to a micrograph image
of a partial section of the polishing pad according to a
Comparative example 1-1.
[0127] FIG. 13 is an explanatory diagram due to a micrograph image
of a partial section of the polishing pad according to Example
2-1.
[0128] FIG. 14 is an explanatory diagram due to a micrograph image
of a partial section of the polishing pad according to Example
3-1.
[0129] FIG. 15 is an explanatory diagram due to a micrograph image
of a partial section of the polishing pad according to Example
4-1.
EXAMPLE
[0130] The present invention is specifically explained below by way
of Example.
[0131] [1] Polishing Pad Having Annular Groove
[0132] 1-1. Production of Polishing Pad
Example 1-1
[0133] 80 parts by volume of 1,2-polybutadiene (Trade name "JSR
RB830" manufactured by JSR Corp.) that becomes a water-insoluble
matrix by crosslinking and 20 parts by volume of
.beta.-cyclodextrin (Trade name "Dexipearl .beta.-100" manufactured
by Bio Research Corporation of Yokohama, average particle diameter;
20 .mu.m) that as a water-soluble particle were kneaded with a
screw extruder that is temperature-controlled at 160.degree. C.,
and thereby white pellet was obtained. Thereafter, 0.3 parts by
volume of organic peroxide (Trade name "Percumyl D-40" manufactured
by NOF Corp.) were compounded and further kneaded at 120.degree.
C.; the kneaded material was extruded into a die and heated at
170.degree. C. for 18 minutes to crosslink; and thereby a disc-like
molded body having a diameter of 60 cm and a thickness of 2.5 mm
was obtained. Thereafter, concentric circle-like grooves in which a
width is 0.5 mm, a depth is 1 mm, a pitch is 1.5 mm and a length
between adjacent grooves is 1 mm shown in FIG. 1 were formed on one
surface side of the molded body with a cutting machine manufactured
by Kato Kikai Co., Ltd.
[0134] In the next place, the surface roughness Ra of an inner
surface of the groove was measured in three different view fields
with a three-dimensional surface structure analytic microscope
(Trade name "Zygo New View 5032" manufactured by CANON Inc.). As a
result, the surface roughness Ra was 1.8 .mu.m.
[0135] A section of a part of the groove for the polishing pad was
enlarged and observed with an optical microscope. The obtained
micrograph image is shown in FIG. 11.
Example 1-2
[0136] 100 parts by volume of 1,2-polybutadiene (Trade name "JSR
RB840" manufactured by JSR Corp.) that becomes a water-insoluble
matrix by crosslinking and 100 parts by volume of a water-soluble
particle (average particle diameter: 20 .mu.m) obtained by coating
polypeptide on .beta.-cyclodextrin (Trade name "Dexipearl
.beta.-100" manufactured by Bio Research Corporation of Yokohama)
were kneaded with a screw extruder that is temperature-controlled
at 160.degree. C., and thereby white pellet was obtained.
Thereafter, 0.3 parts by volume of organic peroxide (Trade name
"Perhexine 25B" manufactured by NOF Corp.) were compounded with the
white pellet and further kneaded at 120.degree. C., and thereby
white pellet was obtained. In the next place, the organic
peroxide-added white pellet was introduced into a die and heated at
190.degree. C. for 10 minutes to crosslink; and thereby a disc-like
molded body having a diameter of 60 cm and a thickness of 2.5 mm
was obtained. Thereafter, on one surface side of the molded body,
concentric circle-like grooves in which a width is 0.5 mm, a depth
is 0.5 mm, a pitch is 1.2 mm and a length between adjacent grooves
is 0.7 mm were formed with a cutting machine similar to Example
1-1.
[0137] Next, the surface roughness Ra of an inner surface of the
groove was measured similarly to Example 1-1. As a result, the
surface roughness Ra was 1.5 .mu.m.
Comparative Example 1-1
[0138] The surface roughness Ra of an inner surface of a groove for
a polishing pad made of foamed polyurethane having an annular
groove that has a width of 0.25 mm, a depth of 0.4 mm and a pitch
of 1.5 mm (Trade name "IC1000" manufactured by Rodel Nitta Co.) was
measured similarly to Example 1-1. As a result, the surface
roughness Ra was 30 .mu.m.
[0139] In addition, a section of a part of the groove for the
polishing pad was enlarged and observed with an optical microscope.
The obtained micrograph image is shown in FIG. 12.
[0140] 1-2. Evaluation of Polishing Performance
[0141] The polishing pads according to Examples 1-1 and 1-2 and
Comparative example 1-1 each were mounted on a surface plate of
polishing apparatus (Trade name "Lap Master LM-15" manufactured by
SFT Corp.) and SiO.sub.2 film wafers were polished for two minutes
under the conditions of the number of revolution of 50 rpm and a
flow rate of 100 cc/min of a chemical mechanical polishing slurry
(Trade name "CMS 1101" manufactured by JSR Corp.) that was diluted
to three times. The polishing pads each were evaluated of the
removal rate, scratches, foreign matters and state of pores. The
respective measurement methods were performed as follows.
[0142] (1) Removal rate; Thicknesses before and after polishing
were measured with an optical thickness meter and a removal rate
was calculated from these thicknesses.
[0143] (2) Scratch and foreign matters; Polished surfaces of the
SiO.sub.2 film wafers after polishing were observed with an
electron microscope.
[0144] The evaluation criteria of the scratch were as follows; that
is, .largecircle.; no scratch was observed, X; scratch was
observed. And the evaluation criteria of the foreign matters was as
follows; that is, .largecircle.; no foreign matter was observed, X
foreign matter was observed.
[0145] (3) State of pores: A surface of each of the polishing pads
was polished for 5 minutes with #400 diamond abrasive followed by
dressing, and thereafter, a state of pores on a dressed surface was
observed with an electron microscope.
[0146] The evaluation criteria were as follows; that is,
.largecircle.; practically all pores were opened, X pores were
partially clogged.
[0147] Results of (1) through (3) are together shown in Table
1.
1 TABLE 1 Removal Surface roughness rate Foreign State of Ra
(.mu.m) (nm/min) Scratch matters pores Example 1-1 1.8 200
.largecircle. .largecircle. .largecircle. Example 1-2 1.5 250
.largecircle. .largecircle. .largecircle. Comparative 30 50 X X X
example 1-1
[0148] From measurement results of the surface roughness, it is
found that the groove of the polishing pad according to Comparative
example 1-1 is large in the unevenness of an inner surface, namely
non-uniform. In addition, according to FIG. 12, a large projection
is observed. Furthermore, FIG. 3.63 in Detailed Semiconductor CMP
Technology, ed. Doi Toshirou (Kogyo Chosakai, first printing), pp.
114 is a scanning electron micrograph of a foamed polyurethane
polishing pad (Trade name "IC1000" manufactured by Rodel Nitta Co.)
similar to the polishing pad used in Comparative example 1-1. Also
from this micrograph, it is found that there is larger unevenness
in the groove in comparison with FIG. 11 due to Example 1-1.
[0149] From results in Table 1, the scratches and foreign matters
were observed on the polished surface polished with the polishing
pad according to Comparative example 1-1. In addition, the pores
after dressing were partially clogged, that is, closed. In
particular, almost all of the pores in the surroundings of the
opening portion of the groove that is likely to be clogged by
dressing were clogged. Furthermore, it is found that the removal
rate of the Comparative example 1-1 was one fourth that of Example
1-1 and one fifth that of Example 1-2, that is, largely inferior to
these. This is considered because the pores were clogged with
foreign matters and the like during polishing.
[0150] On the other hand, in the polishing pads according to
Examples 1-1 and 1-2, a side surface and a bottom surface inside of
the groove were very small in the surface roughness, that is,
smooth. This can be confirmed from FIG. 11. Accordingly, the
scratches and the foreign matters were hardly observed on the
polished surface. Furthermore, almost all of the pores were
completely opened even after dressing, and all of the pores in the
surroundings of the opening of the groove were opened in
particular. The removal rate relative to that of Comparative
example 1-1 was 4 times for example 1-1 and 5 times for Example
1-2. This is considered because the pores were not clogged owing to
the foreign matters.
[0151] [2] Polishing Pad Having Lattice-Like Groove
[0152] 2-1. Production of Polishing Pad
Example 2-1
[0153] On one surface side of the disc-like molded body that was
obtained in Example 1-1 and had a diameter of 60 cm and a thickness
of 2.5 mm, lattice-like grooves in which a width is 0.5 mm, a depth
is 1 mm, a longitudinal pitch is 5 mm and a transverse pitch is 5
mm, and a planar shape of one pattern that forms a lattice is a
square shown in FIG. 4 were formed with a cutting machine
manufactured by Kato Kikai Co., Ltd.
[0154] In the next place, from the obtained polishing pad, a slice
for use in surface roughness measurement was cut so that a groove
might be included in a width direction. Thereafter, the surface
roughness Ra of an inner surface of the groove was measured in
three different view fields of the slice with the above-mentioned
three-dimensional surface structure analytic microscope. As a
result, the surface roughness Ra was 2.5 .mu.m.
[0155] A section of a part of the groove for the polishing pad was
enlarged and observed with an optical microscope. The obtained
micrograph image is shown in FIG. 13.
Example 2-2
[0156] On one surface side of the disc-like molded body that was
obtained in Example 1-2 and had a diameter of 60 cm and a thickness
of 2.5 mm, with a cutting machine similar to Example 2-1,
lattice-like grooves in which a width is 1 mm, a depth is 1 mm, a
longitudinal pitch is 10 mm and a transverse pitch is 10 mm, and a
planar shape of one pattern that forms a lattice is a square were
formed.
[0157] In the next place, the surface roughness Ra of an inner
surface of the groove were measured similarly to Example 2-1. As a
result, the surface roughness Ra was 2.2 .mu.m.
Comparative Example 2-1
[0158] The surface roughness Ra of an inner surface of a groove of
a polishing pad made of foamed polyurethane having a lattice-like
groove that has a width of 2 mm, a depth of 0.5 mm, a longitudinal
pitch of 15 mm and a transverse pitch of 15 mm (Trade name "IC1000"
manufactured by Rodel Nitta Co.) were measured similarly to Example
2-1. As a result, the surface roughness Ra was 25 .mu.m.
[0159] 2-2. Evaluation of Polishing Performance
[0160] Similarly to the [1], the polishing characteristics of the
polishing pads according to Examples 2-1 and 2-2 and Comparative
example 2-1 were evaluated. Results are shown in Table 2.
2 TABLE 2 Removal Surface roughness rate Foreign State of Ra
(.mu.m) (nm/min) Scratch matters pores Example 2-1 2.5 180
.largecircle. .largecircle. .largecircle. Example 2-2 2.2 135
.largecircle. .largecircle. .largecircle. Comparative 25 45 X X X
example 2-1
[0161] From measurement results of the surface roughness, it is
found that the groove of the polishing pad according to Comparative
example 1-1 is large in the unevenness of an inner surface, namely
non-uniform. In addition, FIG. 3.63 in Detailed Semiconductor CMP
Technology, ed. Doi Toshirou (Kogyo Chosakai, first printing), pp.
114 is a scanning electron micrograph of a foamed polyurethane
polishing pad (Trade name "IC1000" manufactured by Rodel Nitta Co.)
similar to the polishing pad used in Comparative example 1-1. Also
from this micrograph, it is found that there is larger unevenness
in the groove in comparison with FIG. 13 due to Example 2-1.
[0162] From results in Table 2, the scratches and foreign matters
were observed on the polished surface polished with the polishing
pad according to Comparative example 2-1. In addition, the pores
after dressing were partially clogged, that is, closed. In
particular, almost all of the pores in the surroundings of the
opening portion of the groove that is likely to be clogged by
dressing were clogged. Furthermore, it is found that the removal
rate of the Comparative example 2-1 was one fourth that of Example
2-1 and one third that of Example 2-2, that is, largely inferior to
these. This is considered because the pores were clogged with
foreign matters and the like during polishing.
[0163] On the other hand, in the polishing pads according to
Examples 2-1 and 2-2, a side surface and a bottom surface inside of
the groove were very small in the surface roughness, that is,
smooth. This can be confirmed from FIG. 13. Accordingly, the
scratches and the foreign matters were hardly observed on the
polished surface. Furthermore, almost all of the pores were
completely opened even after dressing, and all of the pores in the
surroundings of the opening of the groove were opened in
particular. The removal rate relative to that of Comparative
example 2-1 was 4 times for example 2-1 and 3 times for Example
2-2. This is considered because the pores were not clogged owing to
the foreign matters.
[0164] [3] Polishing Pad Having Spiral Groove
[0165] 3-1. Production of Polishing Pad
Example 3-1
[0166] On one surface side of the disc-like molded body that was
obtained in Example 1-1 and had a diameter of 60 cm and a thickness
of 2.5 mm, spiral grooves in which a width is 1 mm, a depth is 1
mm, a pitch is 2.5 mm and a length between adjacent grooves is 1.5
mm shown in FIG. 7 were formed with a cutting machine manufactured
by Kato Kikai Co., Ltd.
[0167] In the next place, from the obtained polishing pad, a slice
for use in surface roughness measurement was cut so that a groove
might be included in a width direction. Thereafter, the surface
roughness Ra of an inner surface of the groove was measured in
three different view fields of the slice with the above-mentioned
three-dimensional surface structure analytic microscope. As a
result, the surface roughness Ra was 2.0 .mu.m.
[0168] A section of a part of the groove for the polishing pad was
enlarged and observed with an optical microscope. The obtained
micrograph image is shown in FIG. 14.
Example 3-2
[0169] On one surface side of the disc-like molded body that was
obtained in Example 1-2 and had a diameter of 60 cm and a thickness
of 2.5 mm, with a cutting machine similar to Example 3-1, spiral
grooves in which a width is 0.5 mm, a depth is 0.5 mm, a pitch of
1.7 mm and a length between adjacent grooves is 1.2 mm were
formed.
[0170] In the next place, the surface roughness Ra of an inner
surface of the groove was measured similarly to Example 3-1. As a
result, the surface roughness Ra was 1.9 .mu.m.
Comparative Example 3-1
[0171] The surface roughness Ra of an inner surface of a groove of
a polishing pad made of foamed polyurethane having a spiral groove
that has a width of 0.25 mm, a depth of 0.4 mm, and a pitch of 1.5
mm (Trade name "IC1000" manufactured by Rodel Nitta Co.) was
measured similarly to Example 3-1. As a result, the surface
roughness Ra was 25 .mu.m.
[0172] 3-2. Evaluation of Polishing Performance
[0173] Similarly to the [1], the polishing characteristics of the
polishing pads according to Examples 3-1 and 3-2 and Comparative
example 3-1 were evaluated. Results are shown in Table 3.
3 TABLE 3 Removal Surface roughness rate Foreign State of Ra
(.mu.m) (nm/min Scratch matters pores Example 3-1 2.0 190
.largecircle. .largecircle. .largecircle. Example 3-2 1.9 260
.largecircle. .largecircle. .largecircle. Comparative 25 50 X X X
example 3-1
[0174] From measurement results of the surface roughness, it is
found that the groove of the polishing pad according to Comparative
example 3-1 is large in the unevenness of an inner surface, namely
non-uniform. In addition, FIG. 3.63 in Detailed Semiconductor CMP
Technology, ed. Doi Toshirou (Kogyo Chosakai, first printing), pp.
114 is a scanning electron micrograph of a foamed polyurethane
polishing pad (Trade name "IC1000" manufactured by Rodel Nitta Co.
has a groove on polishing surface side) similar to the polishing
pad used in Comparative example 3-1. Also from this micrograph, it
is found that there is larger unevenness in the groove in
comparison with FIG. 14 due to Example 3-1.
[0175] From results in Table 3, the scratches and foreign matters
were observed on the polished surface polished with the polishing
pad according to Comparative example 3-1. In addition, the pores
after dressing were partially clogged, that is, closed. In
particular, almost all of the pores in the surroundings of the
opening portion of the groove that is likely to be clogged by
dressing were clogged. Furthermore, it is found that the removal
rate of the Comparative example 2-1 was substantially one fourth
that of Example 3-1 and substantially one fifth that of Example
3-2, that is, largely inferior to these. This is considered because
the pores were clogged with foreign matters and the like during
polishing.
[0176] On the other hand, in the polishing pads according to
Examples 3-1 and 3-2, a side surface and a bottom surface inside of
the groove were very small in the surface roughness, that is,
smooth. This can be confirmed from FIG. 14. Accordingly, the
scratches and the foreign matters were hardly observed on the
polished surface. Furthermore, almost all of the pores were
completely opened even after dressing, and all of the pores in the
surroundings of the opening of the groove were opened in
particular. The removal rate relative to that of Comparative
example 3-1 was nearly 4 times for example 3-1 and so large as more
than 5 times for Example 3-2. This is considered because the pores
were not clogged owing to the foreign matters.
[0177] [4] Polishing Pad Having Concave Portion
[0178] 4-1. Production of Polishing Pad
Example 4-1
[0179] On one surface side of the disc-like molded body that was
obtained in Example 1-1 and had a diameter of 60 cm and a thickness
of 2.5 mm, many concave portions whose planar shape is a circle,
diameter is 0.5 mm, depth is 1 mm, and pitch is 1.5 mm [distances
between the respective concave portions in a circumferential
direction and in a diametrical direction were the same (1 mm),
respectively; that is, these concave portions were disposed
equidistant.] shown in FIG. 9 were formed with a cutting machine
manufactured by Kato Kikai Co., Ltd.
[0180] In the next place, from the obtained polishing pad, a slice
for use in surface roughness measurement was cut out so that a
section of a plurality of concave portions might be included.
Thereafter, the surface roughness Ra of an inner surface of the
groove was measured in three different view fields of the slice
with the above-mentioned three-dimensional surface structure
analytic microscope. As a result, the surface roughness Ra was 2.3
.mu.m.
[0181] A section of a part of the concave portion for the polishing
pad was enlarged and observed with an optical microscope. The
obtained micrograph image is shown in FIG. 15.
Example 4-2
[0182] On one surface side of the disc-like molded body that was
obtained in Example 1-2 and had a diameter of 60 cm and a thickness
of 2.5 mm, with a cutting machine similar to Example 3-1, many
concave portions whose planar shape is a circle, diameter is 0.5
mm, depth is 0.5 mm, and pitch is 1.2 mm [distances between the
respective concave portions in a circumferential direction and in a
diametrical direction were the same (0.7 mm), respectively; that
is, these concave portions were disposed equidistant.] were
formed.
[0183] In the next place, the surface roughness Ra of an inner
surface of the concave portion was measured similarly to Example
4-1. As a result, the surface roughness Ra was 1.5 .mu.m.
Comparative Example 4-1
[0184] The surface roughness Ra of an inner surface of a concave
portion of a polishing pad made of foamed polyurethane having many
concave portions whose diameter is 1.5 mm, depth is 1.0 mm and
pitch is 5.5 mm (Trade name "IC1000" manufactured by Rodel Nitta
Co.) was measured similarly to Example 4-1. As a result, the
surface roughness Ra was 25 .mu.m.
[0185] 4-2. Evaluation of Polishing Performance
[0186] Similarly to the [1], the polishing characteristics of the
polishing pads according to Examples 4-1 and 4-2 and Comparative
example 4-1 were evaluated. Results are shown in Table 4.
4 TABLE 4 Removal Surface roughness rate Foreign State of Ra
(.mu.m) (nm/min) Scratch matters pores Example 4-1 2.3 210
.largecircle. .largecircle. .largecircle. Example 4-2 1.5 260
.largecircle. .largecircle. .largecircle. Comparative 25 50 X X X
example 4-1
[0187] From measurement results of the surface roughness, it is
found that the groove of the polishing pad according to Comparative
example 4-1 is large in the unevenness of an inner surface, namely
non-uniform. In addition, FIG. 3.63 in Detailed Semiconductor CMP
Technology, ed. Doi Toshirou (Kogyo Chosakai, first printing), pp.
114 is a scanning electron micrograph of a foamed polyurethane
polishing pad (Trade name "IC1000" manufactured by Rodel Nitta Co.
has a groove on polishing surface side) similar to the polishing
pad used in Comparative example 4-1. Also from this micrograph, it
is found that there is larger unevenness in the concave portion in
comparison with FIG. 15 due to Example 4-1.
[0188] From results in Table 4, the scratches and foreign matters
were observed on the polished surface polished with the polishing
pad according to Comparative example 4-1. In addition, the pores
after dressing were partially clogged, that is, closed. In
particular, almost all of the pores in the surroundings of the
opening portion of the concave portion that is likely to be clogged
by dressing were clogged. Furthermore, it is found that the removal
rate of the Comparative example 4-1 was substantially one fourth
that of Example 4-1 and substantially one fifth that of Example
4-2, that is, largely inferior to these. This is considered because
the pores were clogged with foreign matters and the like during
polishing.
[0189] On the other hand, in the polishing pads according to
Examples 4-1 and 4-2, a side surface and a bottom surface inside of
the concave portion were very small in the surface roughness, that
is, smooth. This can be confirmed from FIG. 15. Accordingly, the
scratches and the foreign matters were hardly observed on the
polished surface. Furthermore, almost all of the pores were
completely opened even after dressing, and all of the pores in the
surroundings of the opening of the concave portion were opened in
particular. The removal rate relative to that of Comparative
example 4-1 was nearly 4 times for example 4-1 and so large as more
than 5 times for Example 4-2. This is considered because the pores
were not clogged owing to the foreign matters.
* * * * *