U.S. patent application number 11/132365 was filed with the patent office on 2005-11-24 for chemical mechanical polishing pad and chemical mechanical polishing method.
This patent application is currently assigned to JSR Corporation. Invention is credited to Hosaka, Yukio, Nishimura, Hideki, Shiho, Hiroshi, Tano, Hiroyuki.
Application Number | 20050260929 11/132365 |
Document ID | / |
Family ID | 34936689 |
Filed Date | 2005-11-24 |
United States Patent
Application |
20050260929 |
Kind Code |
A1 |
Shiho, Hiroshi ; et
al. |
November 24, 2005 |
Chemical mechanical polishing pad and chemical mechanical polishing
method
Abstract
A chemical mechanical polishing pad having a polishing surface,
a non-polishing surface opposite to the polishing surface and a
side surface for defining these surfaces, the polishing surface
having (i) a first group of grooves which intersect a single
virtual straight line extending from the center toward the
peripheral portion of the polishing surface and do not cross one
another, or a single first spiral groove which expands gradually
from the center portion toward the peripheral portion of the
polishing surface, and (ii) a second group of grooves which extend
from the center portion toward the peripheral portion of the
polishing surface, intersect the first group of grooves or the
first spiral groove and do not cross one another. Since this
chemical mechanical polishing pad fully suppresses the occurrence
of a scratch on the polished surface and has an excellent polishing
rate, it is advantageously used in a chemical mechanical polishing
method.
Inventors: |
Shiho, Hiroshi; (Chuo-ku,
JP) ; Tano, Hiroyuki; (Chuo-ku, JP) ; Hosaka,
Yukio; (Chuo-ku, JP) ; Nishimura, Hideki;
(Chuo-ku, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JSR Corporation
Tokyo
JP
|
Family ID: |
34936689 |
Appl. No.: |
11/132365 |
Filed: |
May 19, 2005 |
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24B 37/26 20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2004 |
JP |
2004-149884 |
Claims
What is claimed is:
1. A chemical mechanical polishing pad having a polishing surface,
a non-polishing surface opposite to the polishing surface and a
side surface for defining these surfaces, the polishing surface
having at least two groups of grooves, wherein the two groups of
grooves consist of (i) a first group of grooves which intersect a
single virtual straight line extending from the center portion
toward the peripheral portion of the polishing surface and do not
cross one another and (ii) a second group of grooves which extend
from the center portion toward the peripheral portion of the
polishing surface, intersect the first group of grooves and do not
cross one another.
2. The pad according to claim 1 which is shaped like a disk and has
a circular top surface and a circular bottom surface as the
polishing surface and the non-polishing surface, respectively.
3. The pad according to claim 1, wherein the first group of grooves
consists of a plurality of grooves which are arranged
concentrically and differ from one another in diameter, or a
plurality of spiral grooves on the polishing surface.
4. The pad according to claim 3, wherein the number of grooves
which are arranged concentrically and differ from one another in
diameter is 20 to 400.
5. The pad according to claim 3, wherein the number of spiral
grooves is 2 to 10.
6. The pad according to claim 1, wherein the grooves of the first
group have a width of 0.1 mm or more and a depth of 0.1 mm or more
and the shortest distance between intersections between the grooves
of the first group and the virtual straight line is 0.05 mm or
more.
7. The pad according to claim 1, wherein the second group of
grooves consists of a plurality of linear grooves extending from
the center portion toward the peripheral portion of the pad and at
least one of them reaches the side surface of the pad.
8. The pad according to claim 1, wherein the second group of
grooves consists of a plurality of linear grooves extending from
the center portion toward the peripheral portion of the pad and a
plurality of linear grooves extending from a halfway portion
between the center portion and the peripheral portion toward the
peripheral portion and at least one of them reaches the side
surface of the pad.
9. The pad according to claim 7 or 8, wherein the second group of
grooves includes paired parallel linear grooves.
10. The pad according to claim 7 or 8, wherein the second group of
grooves consists of 4 to 65 linear grooves.
11. The pad according to claim 7, wherein the grooves of the second
group have a width of 0.1 mm or more and a depth of 0.1 mm or
more.
12. A chemical mechanical polishing method making use of the
chemical mechanical polishing pad of claim 1.
13. A chemical mechanical polishing pad having a polishing surface,
a non-polishing surface opposite to the polishing surface and a
side surface for defining these surfaces, the polishing surface
having at least two groups of grooves, wherein the two groups of
grooves consist of (i) a single first spiral groove which expands
gradually from the center portion toward the peripheral portion of
the polishing surface and (ii) a second group of grooves which
extend from the center portion toward the peripheral portion of the
polishing surface, intersect the spiral groove and do not cross one
anther.
14. The pad according to claim 13 which is shaped like a disk and
has a circular top surface and a circular bottom surface as the
polishing surface and the non-polishing surface, respectively.
15. The pad according to, claim 13, wherein the number of turns of
the spiral groove is 20 to 400.
16. The pad according to claim 13, wherein the first spiral groove
has a width of 0.1 mm or more and a depth of 0.1 mm or more, and
the shortest distance between intersections between the first
spiral groove and a single virtual straight line extending from the
center portion to the peripheral portion of the polishing surface
is 0.05 mm or more.
17. The pad according to claim 13, wherein the second group of
grooves consists of a plurality of linear grooves extending from
the center portion toward the peripheral portion and at least one
of them reaches the side surface of the pad.
18. The pad according to claim 13, wherein the second group of
grooves consist of a plurality of linear grooves extending from the
center portion toward the peripheral portion and a plurality of
linear grooves extending from a halfway portion between the center
portion and the peripheral portion toward the peripheral portion
and at least one of them reaches the side surface of the pad.
19. The pad according to claim 17 or 18, wherein the second group
of grooves includes paired parallel linear grooves.
20. The pad according to claim 17 or 18, wherein the second group
of grooves consists of 4 to 65 linear grooves.
21. The pad according to claim 17, wherein the grooves of the
second group have a width of 0.1 mm or more and a depth of 0.1 mm
or more.
22. A chemical mechanical polishing method making use of the
chemical mechanical polishing pad of claim 13.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a chemical mechanical
polishing pad which can be advantageously used in a chemical
mechanical polishing step and a chemical mechanical polishing
method making use of the polishing pad.
DESCRIPTION OF THE PRIOR ART
[0002] In the manufacture of a semiconductor device, chemical
mechanical polishing (CMP) is attracting much attention as a
polishing technique capable of forming an extremely flat surface.
Chemical mechanical polishing is a technique for polishing by
letting an aqueous dispersion for chemical mechanical polishing,
for example, an aqueous dispersion of abrasive grains flow down
over the surface of a chemical mechanical polishing pad while the
polishing pad and the surface to be polished are brought into slide
contact with each other. It is known that the polishing result is
greatly affected by the performance characteristic and properties
of the polishing pad in this chemical mechanical polishing.
[0003] Heretofore, chemical mechanical polishing has been carried
out by using polyurethane foam containing pores as a polishing pad
to hold slurry in holes (to be referred to as "pores" hereinafter)
which are open to the surface of the resin. It is known that the
polishing rate and the polishing result are improved by forming
grooves in the surface (polishing surface) of the chemical
mechanical polishing pad (JP-A 11-70463, JP-A 8-216029 and JP-A
8-39423) (the term "JP-A" as used herein means an "unexamined
published Japanese patent application").
[0004] However, due to the improvement of the performance and the
downsizing of a semiconductor device, the wiring pattern is
becoming finer, the number of wiring layers is increasing and the
performance required for chemical mechanical polishing and a
chemical mechanical polishing pad is becoming higher. Although the
design of a chemical mechanical polishing pad is described in
detail in the above patent document 1, the polishing rate and the
state of the polished surface are still unsatisfactory. There is a
case where a surface defect like a scratch (to be referred to as
"scratch" hereinafter) occurs, and the improvement of this defect
is desired.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention which has solved
the above problems of the prior art to provide a chemical
mechanical polishing pad which fully suppresses the occurrence of a
scratch on the polished surface and has an excellent polishing rate
and a chemical mechanical polishing method making use of the
polishing pad.
[0006] Other objects and advantages of the present invention will
become apparent from the following description.
[0007] According to the present invention, firstly, the above
objects and advantages of the present invention are attained by a
chemical mechanical polishing pad (may be referred to as "first
polishing pad of the present invention" hereinafter) having a
polishing surface, a non-polishing surface opposite to the
polishing surface, and a side surface for defining these surfaces,
the polishing surface having at least two groups of grooves,
wherein
[0008] the two groups of grooves consist of (i) a first group of
grooves which intersect a single virtual straight line extending
from the center portion toward the peripheral portion of the
polishing surface and do not cross one another and (ii) a second
group of grooves which extend from the center portion toward the
peripheral portion of the polishing surface, intersect the first
group of grooves and do not cross one another.
[0009] According to the present invention, secondly, the above
objects and advantages of the present invention are attained by a
chemical mechanical polishing pad (may be referred to as "second
polishing pad of the present invention" hereinafter) having a
polishing surface, a non-polishing surface opposite to the
polishing surface, and a side surface defining these surfaces, the
polishing surface having (i) a single first spiral groove which
expands gradually from the center portion toward the peripheral
portion of the polishing surface and (ii) a second group of grooves
which extend from the center portion toward the peripheral portion
of the polishing surface, intersect the above spiral groove and do
not cross one anther.
[0010] According to the present invention, thirdly, the above
objects and advantages of the present invention are attained by a
chemical mechanical polishing method making use of the above
chemical mechanical polishing pad of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram showing an example of the arrangement of
grooves;
[0012] FIG. 2 is a diagram showing another example of the
arrangement of grooves;
[0013] FIG. 3 is a diagram showing still another example of the
arrangement of grooves;
[0014] FIG. 4 is a diagram showing a further example of the
arrangement of grooves;
[0015] FIG. 5 is a diagram showing a still further example of the
arrangement of grooves;
[0016] FIG. 6 is a diagram showing a still further example of the
arrangement of grooves;
[0017] FIG. 7 is a diagram showing a still further example of the
arrangement of grooves;
[0018] FIG. 8 is a diagram showing a still further example of the
arrangement of grooves; and
[0019] FIG. 9 is a diagram showing a still further example of the
arrangement of grooves.
[0020] FIG. 10 is a diagram showing a still further example of the
arrangement of grooves.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] The present invention will be described in detail
hereniunder with reference to the accompanying drawings. A
description is first given of the first polishing pad.
[0022] Although the grooves of the first group formed in the
polishing surface are not limited to a particular shape, they may
be, for example, two or more spiral grooves which expand gradually
from the center portion toward the peripheral portion of the
polishing surface, or annular or polygonal grooves which do not
cross one another and are arranged concentrically. The annular
grooves may be circular or elliptic, and the polygonal grooves may
be tetragonal, hexagonal, etc.
[0023] The grooves of the first group do not cross one another.
[0024] The grooves of the first group are formed in the polishing
surface in such a manner that they intersect a single virtual
straight line extending from the center portion toward the
peripheral portion of the polishing surface a plurality of times.
For example, when the grooves are annular and the number of the
annular grooves is 2, the number of intersections is 2, when the
number of the annular grooves is 3, the number of intersections is
3, and when the number of the annular grooves is "n", the number of
intersections is "n". When there are two spiral grooves, the number
of intersections is 2 before the second turn (one turn is
360.degree.), 3 after the start of the second turn and (n+1) after
the start of the "n"-th turn.
[0025] When the grooves are polygonal, the same can be said.
[0026] When the grooves are annular or polygonal, they are arranged
not to cross one another and may be arranged concentrically or
eccentrically but preferably concentrically. A polishing pad having
annular or polygonal grooves which are arranged concentrically is
superior in the above functions to other polishing pads. The
annular grooves are preferably circular grooves, more preferably
circular grooves which are arranged concentrically. When the
circular grooves are arranged concentrically, the obtained
polishing pad is excellent in the above functions and the formation
of the grooves is easy.
[0027] The sectional form in the width direction, that is, a
direction perpendicular to the groove direction of the grooves is
not particularly limited. It may be, for example, polygonal with
three or more sides consisting of flat sides and a bottom side,
U-shaped or V-shaped.
[0028] The number of the grooves (annular grooves) which differ
from one another in diameter and are arranged concentrically may
be, for example, 20 to 400 and the number of the spiral grooves may
be, for example, 2 to 10.
[0029] Although the size of the grooves is not particularly
limited, the width of the grooves of the first group may be 0.1 mm
or more, preferably 0.1 to 5 mm, more preferably 0.2 to 3 mm. The
depth of the grooves may be 0.1 mm or more, preferably 0.1 to 2.5
mm, more preferably 0.2 to 2.0 mm. As for the interval between
grooves, the shortest distance between adjacent intersections
between the above virtual straight line and the grooves of the
first group may be 0.05 mm or more, preferably 0.05 to 100 mm, more
preferably 0.1 to 10 mm. A chemical mechanical polishing pad having
the excellent effect of reducing the number of scratches on the
polished surface and a long service life can be facilely
manufactured by forming grooves having the above ranges.
[0030] The above preferred ranges may be combined in various ways.
For example, the width of the grooves may be set to 0.1 mm or more,
the depth of the grooves may be set to 0.1 mm or more, and the
interval between adjacent grooves may be set to 0.05 mm or more.
Preferably, the width of the grooves is set to 0.1 to 5 mm, the
depth of the grooves is set to 0.1 to 2.5 mm, and the interval
between adjacent grooves is set to 0.15 to 105 mm. More preferably,
the width of the grooves is set to 0.2 to 3 mm, the depth of the
grooves is set to 0.2 to 2.0 mm, and the interval between adjacent
grooves is set to 0.6 to 13 mm.
[0031] Although the sectional form of the grooves, that is, the
shape of the cut plane obtained when the grooves are cut in the
normal direction is not particularly limited, it is, for example,
polygonal or U-shaped. Examples of the polygonal shape include
triangle, tetragon and pentagon.
[0032] The pitch which is the sum of the width of the grooves and
the distance between adjacent grooves is preferably 0.15 mm or
more, more preferably 0.15 to 105 mm, much more preferably 0.5 to
13 mm, particularly preferably 0.5 to 5.0 mm, ideally 0.5 to 2.2
mm.
[0033] The surface roughness (Ra) of the inner wall of each of the
above grooves of the first group is preferably 20 .mu.m or less,
more preferably 0.05 to 15 .mu.m, particularly preferably 0.05 to
10 .mu.m. A scratch which may occur on the polished surface in the
chemical mechanical polishing step can be prevented more
effectively by setting this surface roughness to 20 .mu.m or
less.
[0034] The above surface roughness (Ra) is defined by the following
equation (1):
Ra=.SIGMA..vertline.Z-Z.sub.av.vertline./N (1)
[0035] wherein N is the number of measurement points, Z is the
height of a roughness profile and Z.sub.av is the average height of
the roughness profile.
[0036] The above second group of grooves consists of a plurality of
grooves extending from the center portion toward the peripheral
portion of the polishing surface. The expression "center portion"
as used herein means an area surrounded by a circle having a radius
of 50 mm from the center of gravity on the surface of the chemical
mechanical polishing pad as the center thereof. The grooves of the
second group may extend from any point within this "center portion"
toward the peripheral portion and may be linear or arcuate, or a
combination thereof.
[0037] The grooves of the second group may or may not reach the
peripheral end. Preferably, at least one of them reaches the
peripheral end, that is, the side surface of the pad. For example,
the second group of grooves may consist of a plurality of linear
grooves extending from the center portion toward the peripheral
portion and at least one of them may reach the side surface of the
pad, or the second group of grooves may consist of a plurality of
linear grooves extending from the center portion toward the
peripheral portion and a plurality of linear grooves extending from
a halfway portion between the center portion and the peripheral
portion toward the peripheral portion and at least one of them may
reach the side surface of the pad. Further, the second group of
grooves may consist of pairs of two parallel linear grooves.
[0038] The number of the grooves of the second group is preferably
4 to 65, more preferably 8 to 48.
[0039] The grooves of the second group existent on the surface of
the chemical mechanical polishing pad may or may not be in contact
with one another but do not cross one another. Preferably, 2 to 32
out of the grooves of the second group are in contact with other
grooves of the second group in the area of the above center
portion. More preferably, 2 to 16 out of the grooves of the second
group are in contact with other grooves of the second group. Some
of the second grooves may be in contact with other grooves of the
second group and other grooves at positions other than the center
portion of the surface of the pad.
[0040] The preferred width and depth of the grooves of the second
group are the same as those of the first group. The preferred range
of the surface roughness (Ra) of the inner wall of each of the
grooves of the second group is the same as that of the first
group.
[0041] The grooves of the second group are preferably arranged as
equally as possible on the surface of the chemical mechanical
polishing pad.
[0042] The grooves of the second group formed in the polishing
surface of the chemical mechanical polishing pad of the present
invention may be arranged as shown in the diagrams of FIGS. 1 to
7.
[0043] The second polishing pad of the present invention has a
single first spiral groove which expands gradually from the center
portion toward the peripheral portion of the polishing surface in
place of the first group of grooves of the above first polishing
pad.
[0044] The number of turns of the first spiral groove may be 20 to
400. 360.degree. corresponds to one turn.
[0045] The first spiral groove has a width of 0.1 mm or more and a
depth of 0.1 mm or more and the shortest distance between
intersections between the first spiral groove and a single virtual
straight line extending from the center portion toward the
peripheral portion of the polishing surface may be 0.05 mm or
more.
[0046] As for what is not described of the second polishing pad, it
should be understood that what has been described of the first
polishing pad can be applied to the second polishing pad as it is
or with modifications obvious to those skilled in the art.
[0047] Examples of the arrangement of the grooves of the chemical
mechanical polishing pad of the present invention will be described
with reference to the accompanying drawings.
[0048] In FIG. 1, the pad 1 has a second group of 16 linear grooves
2 extending from the center of the pad to the peripheral portion
and a first group of 10 concentrically circular grooves 3 which
differ from one another in diameter on the polishing surface. The
16 linear grooves 2 of the second group do not cross one another
and the 10 concentrically circular grooves 3 of the first group do
not cross one another but intersect the linear grooves. In the pad
of FIG. 1, all the 16 linear grooves reach the side surface of the
pad.
[0049] The pad of FIG. 2 has a second group of 32 linear grooves 2
and a first group of 10 concentrically circular grooves 3 which
differ from one another in diameter. 4 out of the 32 linear grooves
start from the center whereas the other 28 linear grooves start
from a portion slightly away from the center (this portion can be
judged as the center portion from the fact that the linear grooves
intersect the smallest circular groove of the first group) toward
the peripheral portion. In the pad of FIG. 2, all the 32 linear
grooves reach the side surface of the pad.
[0050] In FIG. 3, the pad 1 has a second group of 64 linear grooves
2 and a first group of 10 concentrically circular grooves 3 which
differ from one another in diameter. 8 out of the 64 linear grooves
start from the center whereas the other 56 linear grooves start
from a portion slightly away from the center toward the peripheral
portion. In the pad of FIG. 3, all the 64 linear grooves reach the
side surface of the pad as well.
[0051] In FIG. 4, the pad 1 has a second group of 16 grooves 2
extending from the center portion toward the peripheral portion. 4
out of the 16 grooves start from the center whereas the other 12
grooves start from a portion slightly away from the center toward
the peripheral portion. As shown in FIG. 4, the 16 grooves curve to
the left halfway from the center toward the periphery but they
extend almost linearly excluding these curved portions.
[0052] The pad of FIG. 5 is a variation of the pad of FIG. 1. That
is, all the 16 linear grooves 2 of the second group start from the
center portion, that is, a portion slightly away from the center
toward the peripheral portion. All the linear grooves 2 start from
their intersections with the smallest circular groove out of the
concentrically circular grooves of the first group.
[0053] The pad of FIG. 6 has a second group of 8 linear grooves 2
which start from the center. The 8 linear grooves do not reach the
side surface of the pad and ends at their intersections with the
largest circular groove out of the concentrically circular grooves
of the first group.
[0054] The pad of FIG. 7 has a second group of 8 linear grooves
which start from the center and branch into two linear grooves 2'
and 2" at a halfway position before they reach the peripheral
portion.
[0055] The pad of FIG. 8 has 32 linear grooves, which start from a
halfway portion between the center portion and the peripheral
portion, between adjacent all of the 32 linear grooves shown in
FIG. 2. The 32 linear grooves start from their intersections with
the fourth circular groove from the center in FIG. 2.
[0056] The pad of FIG. 9 has 28 pairs of two parallel linear
grooves which start from a portion slightly away from the center
toward the peripheral portion in place of the 28 linear grooves in
FIG. 2.
[0057] The pad of FIG. 10 has a single first spiral groove 4 which
makes 10 turns and a second group of 16 linear grooves 2. The
spiral groove starts from the center of the pad, expands gradually
and reaches the peripheral portion.
[0058] The arrangement of the grooves on the polishing surface of
the polishing pad of the present invention is preferably symmetric
about the center, for example, point symmetrical, line symmetrical
or plane symmetrical as understood from FIGS. 1 to 10.
[0059] The first polishing pad and the second polishing pad of the
present invention may have a recessed portion on the non-polishing
surface (rear side of the pad) as required. This recessed portion
has the function of dispersing a local pressure rise caused by the
pressure of the polishing head in the chemical mechanical polishing
step and contributes to the further reduction of the number of
scratches on the polished face. The position of the recessed
portion is not particularly limited but preferably located in the
center portion of the pad. The expression "located in the center
portion" means not only that the recessed portion is located at the
center in the mathematically strict sense but also that the center
of the non-polishing surface of the polishing pad may be located
within the area of the above recessed portion.
[0060] The above recessed portion is not limited to a particular
shape but preferably circular or polygonal, particularly preferably
circular. When the recessed portion is circular, the upper limit of
its diameter is preferably 100%, more preferably 75%, particularly
preferably 50% of the diameter of a wafer as an object to be
polished. When the recessed portion is circular, the lower limit of
its diameter is preferably 1 mm, more preferably 5 mm irrespective
of the size of the wafer as the object to be polished.
[0061] The shape of the chemical mechanical polishing pad of the
present invention is not particularly limited. It may be shaped
like a disk or polygonal pole. The shape of the chemical mechanical
polishing pad of the present invention may be suitably selected
according to a polishing machine to be used with the chemical
mechanical polishing pad of the present invention.
[0062] For example, when the chemical mechanical polishing pad is
shaped like a disk, its circular top surface and circular under
surface serve as the polishing surface and the non-polishing
surface, respectively.
[0063] The size of the chemical mechanical polishing pad is not
particularly limited. For example, a disk-like chemical mechanical
polishing pad has a diameter of 150 to 1,200 mm, particularly
preferably 500 to 800 mm and a thickness of 0.5 to 5.0 mm,
preferably 1.0 to 3.0 mm, particularly preferably 1.5 to 3.0
mm.
[0064] The chemical mechanical polishing pad of the present
invention may be made of any material if it has the above grooves.
For example, the chemical mechanical polishing pad may be a pad
comprising a water-insoluble matrix and water-soluble particles
dispersed in the water-insoluble matrix or a pad having fine pores
in a water-insoluble matrix.
[0065] In the former material, the water-soluble particles dissolve
or swell upon their contact with an aqueous medium of slurry
containing an aqueous medium and solid matter at the time of
polishing to be eliminated, and slurry can be held in pores formed
by elimination. In the latter material, the slurry can be held in
the pores formed as cavities.
[0066] The material for forming the above "water-insoluble matrix"
is not particularly limited but an organic material is preferably
used because it is easily molded to have a predetermined shape and
predetermined properties and can provide suitable hardness and
suitable elasticity. Examples of the organic material include
thermoplastic resins, elastomers, rubbers such as crosslinked
rubbers, and curable resins such as thermally or optically curable
resins and resins cured by heat or light. They may be used alone or
in combination.
[0067] Out of these, the above thermoplastic resins include
1,2-polybutadiene resin, polyolefin resins such as polyethylene,
polystyrene resins, polyacrylic resins such as (meth)acrylate-based
resins, vinyl ester resins (excluding acrylic resins), polyester
resins, polyamide resins, fluororesins such as polyvinylidene
fluoride, polycarbonate resins and polyacetal resins.
[0068] The above elastomers include diene elastomers such as
1,2-polybutadiene, polyolefin elastomer (TPO), styrene-based
elastomers such as styrene-butadiene-styrene block copolymer (SBS)
and hydrogenated block copolymers thereof (SEBS), thermoplastic
elastomers such as thermoplastic polyurethane elastomers (TPU),
thermoplastic polyester elastomers (TPEE) and polyamide elastomers
(TPAE), silicone resin elastomers and fluororesin elastomers. The
above rubbers include conjugated diene rubbers such as butadiene
rubber (high cis-butadiene rubber, low cis-butadiene rubber, etc.),
isoprene rubber, styrene-butadiene rubber and styrene-isoprene
rubber, nitrile rubbers such as acrylonitrile-butadiene rubber,
acrylic rubber, ethylene-.alpha.-olefin rubbers such as
ethylene-propylene rubber and ethylene-propylene-diene rubber,
butyl rubber, silicone rubber and fluorine rubber.
[0069] The above curable resins include urethane resins, epoxy
resins, acrylic resins, unsaturated polyester resins,
polyurethane-urea resins, urea resins, silicon resins, phenolic
resins and vinyl ester resins.
[0070] These organic materials may be modified by an acid anhydride
group, carboxyl group, hydroxyl group, epoxy group or amino group.
The affinity for the water-soluble particles to be described
hereinafter and slurry can be adjusted by modification.
[0071] These organic materials may be used alone or in combination
of two or more.
[0072] The organic material may be a partially or wholly
crosslinked polymer or non-crosslinked polymer. Therefore, the
water-insoluble matrix may be composed of a crosslinked polymer
alone, a mixture of a crosslinked polymer and a non-crosslinked
polymer, or a non-crosslinked polymer alone. It is preferably
composed of a crosslinked polymer alone or a mixture of a
crosslinked polymer and a non-crosslinked polymer. When a
crosslinked polymer is contained, elastic recovery force is
provided to the water-insoluble matrix and displacement caused by
shear stress applied to the polishing pad during polishing can be
reduced. Further, it is possible to effectively prevent the pores
from being filled by the plastic deformation of the water-insoluble
matrix when it is excessively stretched at the time of polishing
and dressing and the surface of the polishing pad from being
excessively fluffed. Therefore, the pores are formed efficiently
even during dressing, whereby the deterioration of the holding
properties of the slurry during polishing can be suppressed and
further the polishing pad is rarely fluffed, thereby not impairing
polishing flatness. The method of crosslinking the above material
is not particularly limited. For example, chemical crosslinking
making use of an organic peroxide, sulfur or sulfur compound, or
radiation crosslinking by applying an electron beam may be
employed.
[0073] Out of these, chemical crosslinking is preferred. In the
case of chemical crosslinking, an organic peroxide is preferably
used as a crosslinking agent because it is easy to handle and does
not contaminate an object to be polished. Examples of the organic
peroxide include dicumyl peroxide, diethyl peroxide, di-t-butyl
peroxide, diacetyl peroxide and diacyl peroxide. For chemical
crosslinking, the amount of the crosslinking agent is preferably
0.01 to 5.0 parts by mass, more preferably 0.2 to 4.0 parts by mass
based on 100 parts by mass of the crosslinkable polymer contained
in the water-insoluble member. A chemical mechanical polishing pad
which suppresses the occurrence of a scratch in the chemical
mechanical polishing step can be obtained by setting the amount of
the crosslinking agent to the above range. All of the material
constituting the water-insoluble member may be crosslinked at a
time, or part of the material constituting the water-insoluble
member is crosslinked and then mixed with the rest of the material.
Alternatively, several different types of specially crosslinked
products may be mixed together.
[0074] For chemical crosslinking, a mixture of organic materials
some of which the water-insoluble member are crosslinked and the
other are not can be easily obtained with a single crosslinking
operation by adjusting the amount of the crosslinking agent and
crosslinking conditions. For radiation crosslinking, by adjusting
the dose of radiation, the same effect as described above can be
easily obtained.
[0075] Out of the above organic materials, a crosslinked rubber,
curable resin, crosslinked thermoplastic resin or crosslinked
elastomer may be used as the crosslinked polymer. A crosslinked
thermoplastic resin and/or crosslinked elastomer all of which are
stable to a strong acid or strong alkali contained in many kinds of
slurry and are rarely softened by water absorption are/is
preferred. Out of the crosslinked thermoplastic resin and
crosslinked elastomer, what is crosslinked with an organic peroxide
is more preferred, and crosslinked 1,2-polybutadiene is
particularly preferred.
[0076] The amount of the crosslinked polymer is not particularly
limited but preferably 30 vol % or more, more preferably 50 vol %
or more, particularly preferably 70 vol % or more and may be 100
vol % of the water-insoluble matrix. When the amount of the
crosslinked polymer contained in the water-insoluble matrix is
smaller than 30 vol %, the effect obtained by containing the
crosslinked polymer may not be fully obtained.
[0077] The residual elongation after breakage (to be simply
referred to as "residual elongation at break" hereinafter) of the
above water-insoluble matrix containing a crosslinked polymer can
be 100% or less when a specimen of the above water-insoluble matrix
is broken at 80.degree. C. in accordance with JIS K 6251. That is,
the total distance between bench marks of the specimen after
breakage becomes 2 times or less the distance between the bench
marks before breakage. This residual elongation at break is
preferably 30% or less, more preferably 10% or less and
particularly preferably 5% or less. When the above residual
elongation at break is more than 100%, fine pieces scraped off from
the surface of the polishing pad or stretched at the time of
polishing and surface renewal tend to fill the pores
disadvantageously. The "residual elongation at break" is an
elongation obtained by subtracting the distance between bench marks
before the test from the total distance between each bench mark and
the broken portion of the broken and divided specimen in a tensile
test in which a dumbbell-shaped specimen No. 3 is broken at a
tensile rate of 500 mm/min and a test temperature of 80.degree. C.
in accordance with the "vulcanized rubber tensile test method"
specified in JIS K 6251. The test is carried out at 80.degree. C.
because heat is generated by slide contact at the time of actual
polishing.
[0078] The above "water-soluble particles" are particles which are
eliminated from the water-insoluble matrix upon their contact with
slurry as an aqueous dispersion in the polishing pad. This
elimination may occur when they dissolve in water contained in the
slurry upon their contact with water or when they swell and gel by
absorbing this water. Further, this dissolution or swelling is
caused not only by their contact with water but also by their
contact with an aqueous mixed medium containing an alcohol-based
solvent such as methanol.
[0079] The water-soluble particles have the effect of increasing
the indentation hardness of the polishing pad in addition to the
effect of forming pores in the polishing pad. For example, the
shore D hardness of the polishing pad of the present invention can
be set to preferably 35 or more, more preferably 50 to 90,
particularly preferably 50 to 80 and generally 100 or less by
adding the water-soluble particles. When the shore D hardness is 35
or more, pressure applied to the object to be polished can be
increased, and the polishing rate can be thereby improved. In
addition, high polishing flatness is obtained. Therefore, the
water-soluble particles are particularly preferably made of a solid
substance which can ensure sufficiently high indentation hardness
for the polishing pad.
[0080] The material for forming the water-soluble particles is not
particularly limited. They are, for example, organic water-soluble
particles or inorganic water-soluble particles. Examples of the
material of the organic water-soluble particles include saccharides
(polysaccharides such as starch, dextrin and cyclodextrin, lactose,
mannitol, etc.), celluloses (such as hydroxypropyl cellulose,
methyl cellulose, etc.), protein, polyvinyl alcohol, polyvinyl
pyrrolidone, polyacrylic acid, polyethylene oxide, water-soluble
photosensitive resins, sulfonated polyisoprene and sulfonated
polyisoprene copolymers. Examples of the material of the inorganic
water-soluble particles include potassium acetate, potassium
nitrate, potassium carbonate, potassium hydrogencarbonate,
potassium chloride, potassium bromide, potassium phosphate and
magnesium nitrate. These water-soluble particles may be used alone
or in combination of two or more. The water-soluble particles may
be made of a predetermined single material, or two or more
different materials.
[0081] The water-soluble particles have an average particle
diameter of preferably 0.1 to 500 .mu.m, more preferably 0.5 to 100
.mu.m. The pores are as big as preferably 0.1 to 500 .mu.m, more
preferably 0.5 to 100 .mu.m. When the average particle diameter of
the water-soluble particles is smaller than 0.1 .mu.m, the formed
pores become smaller in size than the abrasive grains in use,
whereby a polishing pad capable of holding slurry completely may be
hardly obtained. When the average particle diameter is larger than
500 .mu.m, the formed pores become too big, whereby the mechanical
strength and polishing rate of the obtained polishing pad may
lower.
[0082] The amount of the water-soluble particles is preferably 2 to
90 vol %, more preferably 2 to 60 vol %, particularly preferably 2
to 40 vol % based on 100 vol % of the total of the water-insoluble
matrix and the water-soluble particles. When the amount of the
water-soluble particles is smaller than 2 vol %, pores are not
fully formed in the obtained polishing pad and the polishing rate
may lower. When the amount of the water-soluble particles is larger
than 90 vol %, it may be difficult to completely prevent the
water-soluble particles existent in the interior of the obtained
polishing pad from swelling or dissolving, thereby making it
difficult to maintain the hardness and mechanical strength of the
obtained chemical mechanical polishing pad at appropriate
values.
[0083] It is preferred that the water-soluble particles should
dissolve in water only when they are exposed to the surface layer
of the polishing pad and should not absorb moisture or swell when
they are existent in the interior of the polishing pad. Therefore,
the water-soluble particles may have an outer shell for suppressing
moisture absorption on at least part of their outermost portion.
This outer shell may be physically adsorbed to the water-soluble
particle, chemically bonded to the water-soluble particle, or in
contact with the water-soluble particle by physical adsorption and
chemical bonding. The outer shell is made of epoxy resin,
polyimide, polyamide or polysilicate. Even when it is formed on
only part of the water-soluble particle, the above effect can be
fully obtained.
[0084] The above water-insoluble matrix may contain a
compatibilizing agent to control its affinity for the water-soluble
particles and the dispersibility of the water-soluble particles in
the water-insoluble matrix. Examples of the compatibilizing agent
include homopolymers, block copolymers and random copolymers
modified by an acid anhydride group, carboxyl group, hydroxyl
group, epoxy group, oxazoline group or amino group, nonionic
surfactants and coupling agents.
[0085] The water-insoluble matrix material constituting the
polishing pad comprising the latter water-insoluble matrix material
(foam, etc.) containing cavities dispersed therein is, for example,
a polyurethane, melamine resin, polyester, polysulfone or polyvinyl
acetate.
[0086] The average size of the cavities dispersed in the above
water-insoluble matrix material is preferably 0.1 to 500 .mu.m,
more preferably 0.5 to 100 .mu.m.
[0087] The process for manufacturing the chemical mechanical
polishing pad of the present invention is not particularly limited,
and the methods of forming the grooves of the chemical mechanical
polishing pad and the optional recessed portion in the rear surface
of the chemical mechanical polishing pad (both will be generally
referred to as "grooves" hereinafter) are not particularly limited
as well. For example, after a composition for forming a chemical
mechanical polishing pad which will become a chemical mechanical
polishing pad is prepared and molded into a substantially desired
form, grooves may be formed by cutting. Alternatively, a metal mold
having a groove pattern is used to mold the composition for forming
a chemical mechanical polishing pad, thereby making it possible to
form groves simultaneously with the manufacture of a desired form
for the chemical mechanical polishing pad. The surface roughness of
the inner wall of each of the grooves can be easily set to 20 .mu.m
or less by molding.
[0088] The method of obtaining the composition for forming a
chemical mechanical polishing pad is not particularly limited. For
example, the composition can be obtained by kneading together
required materials including a predetermined organic material by
means of a kneader. A conventionally known kneader may be used,
such as a roll, kneader, Banbury mixer or extruder (single-screw,
multiple-screw).
[0089] The composition for forming a chemical mechanical polishing
pad, which comprises water-soluble particles for obtaining a
polishing pad containing the water-soluble particles, can be
obtained, for example, by kneading together a water-insoluble
matrix, water-soluble particles and other additives. In general,
they are kneaded together under heating so that they can be easily
processed at the time of kneading. The water-soluble particles are
preferably solid at this kneading temperature. When they are solid,
they can be dispersed with the above preferred average particle
diameter irrespective of their compatibility with the
water-insoluble matrix. Therefore, the type of the water-soluble
particles is preferably selected according to the processing
temperature of the water-insoluble matrix in use.
[0090] The chemical mechanical polishing pad of the present
invention may be a multi-layer pad having a base layer formed on
the non-polishing surface of the above pad.
[0091] The above "base layer" is a layer formed on the rear surface
to support the chemical mechanical polishing pad. Although the
characteristic properties of this base layer are not particularly
limited, the base layer is preferably softer than the pad body.
When the pad has a soft base layer, if the pad body is thin, for
example, 1.0 mm or less, it is possible to prevent the pad body
from rising during polishing or the surface of the polishing layer
from curving, whereby polishing can be carried out stably. The
hardness of the base layer is preferably 90% or less, more
preferably 50 to 90%, much more preferably 50 to 80%, particularly
preferably 50 to 70% of the hardness of the pad body.
[0092] The base layer may be made of a porous material such as foam
or a non-porous material. The planar shape of the base layer is not
particularly limited and may be the same or different from that of
the polishing layer. The planar shape of the base layer may be
circular or polygonal, for example, tetragonal. Its thickness is
not particularly limited but preferably 0.1 to 5 mm, more
preferably 0.5 to 2 mm.
[0093] Although the material of the base layer is not particularly
limited, an organic material is preferably used because it can be
easily molded to have a predetermined shape and predetermined
properties and can provide suitable elasticity.
[0094] The above-described chemical mechanical polishing pad of the
present invention can provide an excellent polished surface at a
high polishing rate and has a long service life.
[0095] The mechanism that the chemical mechanical polishing pad of
the present invention reduces the number of scratches on the
polished surface of an object is not made clear yet. Since a
phenomenon that an aqueous dispersion for chemical mechanical
polishing and polishing chips are remained in the center portion of
the conventionally known chemical mechanical polishing pad is
observed in the chemical mechanical polishing step, it is assumed
that the above holdup serves as the source of a scratch. Meanwhile,
since the above phenomenon is not observed in the chemical
mechanical polishing step when the chemical mechanical polishing
pad of the present invention is used, it is considered that the
remains are effectively removed by the formation of the above
grooves in the polishing surface, thereby obtaining the effect of
reducing the number of scratches.
[0096] The chemical mechanical polishing method of the present
invention is characterized by making use of the chemical mechanical
polishing pad of the present invention. The chemical mechanical
polishing pad of the present invention can be used for chemical
mechanical polishing by means of known processes when it is set in
a commercially available polishing machine.
[0097] The type of the surface to be polished and the type of the
aqueous dispersion for chemical mechanical polishing in use are not
particularly limited.
EXAMPLES
Example 1
[0098] (1) Manufacture of Chemical Mechanical Polishing Pad
[0099] 80 parts by volume (equivalent to 72 parts by mass) of
1,2-polybutadiene (manufactured by JSR Corporation, trade name of
JSR RB830) which would be crosslinked to become a water-insoluble
matrix and 20 parts by volume (equivalent to 28 parts by mass) of
.beta.-cyclodextrin (manufactured by Bio Research Corporation of
Yokohama, trade name of Dexy Pearl .beta.-100, average particle
diameter of 20 .mu.m) as water-soluble particles were kneaded
together by an extruder set at 160.degree. C. Thereafter, 1.0 part
by volume (equivalent to 1.1 parts by mass) of dicumyl peroxide
(manufactured by NOF Corporation, trade name of Percumyl D) was
added to and kneaded with the above kneaded product at 120.degree.
C. to obtain a pellet. The resulting kneaded product was then
heated in a metal mold at 170.degree. C. for 18 minutes to be
crosslinked so as to obtain a disk-like molded product having a
diameter of 600 mm and a thickness of 2.5 mm. Concentrically
circular grooves having a width of 0.5 mm and a depth of 1.0 mm
were formed in the polishing surface of this molded product at a
pitch of 2.0 mm by using a cutting machine manufactured by Kato
Machinery Co., Ltd. (first group of grooves). Further, 16 linear
grooves (having a width of 1.0 mm and a depth of 1.0 mm) extending
from the center to the peripheral end of the pad were formed in the
polishing surface in such a manner that they were in contact with
one another at the center of the polishing surface of the pad and
the angle between adjacent linear grooves was 22.5.degree. (second
group of grooves). The arrangement of the formed grooves is shown
in the diagram of FIG. 1. When the surface roughness of the inner
wall of each of the formed grooves was measured with the Zygo New
View 5032 3-D surface configuration analyzing microscope of Canon
Inc., it was 4.2 .mu.m.
[0100] (2) Evaluation of Polishing Rate and the Number of
Scratches
[0101] The above manufactured chemical mechanical polishing pad was
set on the platen of a polishing machine (EPO112 of Ebara
Corporation), and a wafer (diameter of 8 inches) having an
SiO.sub.2 film (PETEOS film: SiO.sub.2 film formed from tetraethyl
orthosilicate (TEOS) by chemical vapor deposition using plasma as a
promoting condition) and no pattern was polished by using the
CMS-1101 (trade name, manufactured by JSR Corporation) diluted 3
times as chemical mechanical polishing slurry under the following
conditions to evaluate the polishing rate and the number of
scratches. As a result, the polishing rate was 210 nm/min and no
scratch was observed on the polished surface.
[0102] Platen revolution: 70 rpm
[0103] Head revolution: 63 rpm
[0104] Head pressure: 4 psi
[0105] Slurry feed rate: 200 ml/min
[0106] Polishing time: 2 minutes
[0107] The above polishing rate was calculated from the difference
in film thickness by measuring the thickness of the film before and
after polishing with an optical film thickness meter. The number of
scratches on the entire polished surface of the SiO.sub.2 film
wafer after polishing was counted with a wafer defect inspection
device (KLA2351 of KLA-Tencor Co., Ltd.).
Example 2
[0108] A chemical mechanical polishing pad was manufactured in the
same manner as in Example 1 except that 4 linear grooves (having a
width of 1.0 mm and a depth of 1.0 mm) were formed from the center
to the peripheral end of the pad as a second group of grooves in
such a manner that they were in contact with one another at the
center of the polishing surface of the pad and the angle between
adjacent linear grooves was 90.degree. and that 28 linear grooves
were formed from a portion 25 mm away from the center of the pad to
the peripheral end in such a manner that the angle between adjacent
linear grooves was 11.25.degree.. The arrangement of the formed
grooves is shown in the diagram of FIG. 2. The surface roughness of
the inner wall of each of the formed grooves was 3.9 .mu.m.
[0109] The polishing rate and the number of scratches were
evaluated in the same manner as in Example 1 except that the above
polishing pad was used. As a result, the polishing rate was 220
nm/min and no scratch was observed.
Example 3
[0110] 64 parts by volume (equivalent to 58 parts by mass) of
1,2-polybutadiene (manufactured by JSR Corporation, trade name of
JSR RB830), 16 parts by volume (equivalent to 14 parts by mass) of
a block copolymer of 1,2-polybutadiene and polystyrene
(manufactured by JSR Corporation, trade name of TR2827) and 20
parts by volume (equivalent to 28 parts by mass) of
.beta.-cyclodextrin (manufactured by of Bio Research Corporation of
Yokohama, trade name of Dexy Pearl .beta.-100, average particle
diameter of 20 .mu.m) as water-soluble particles were kneaded
together by an extruder set at 160.degree. C. Thereafter, 0.5 part
by volume (equivalent to 0.56 part by mass) of dicumyl peroxide
(manufactured by NOF Corporation, trade name of Percumyl D) was
added to and kneaded with the above kneaded product at 120.degree.
C. to obtain a pellet. The resulting kneaded product was then
heated in a metal mold at 180.degree. C. for 10 minutes to be
crosslinked so as to obtain a disk-like molded product having a
diameter of 600 mm and a thickness of 2.5 mm. Concentrically
circular grooves having a width of 0.5 mm and a depth of 1.0 mm
were formed in the polishing surface of this molded product at a
pitch of 1.5 mm by using a cutting machine manufactured by Kato
Machinery Co., Ltd. (first group of grooves). Further, 8 linear
grooves (having a width of 1.0 mm and a depth of 1.0 mm) were
formed from the center to the peripheral end of the pad in such a
manner that they were in contact with one another at the center of
the polishing surface of the pad and the angle between adjacent
linear grooves was 45.degree. (second group of grooves), and
further 56 linear grooves were formed from a portion 25 mm away
from the center of the pad to the peripheral end in such a manner
that the angle between adjacent linear grooves was 5.625.degree.
(second group of grooves). The arrangement of the formed grooves is
shown in the diagram of FIG. 3. When the surface roughness of the
inner wall of each of the formed grooves was measured, it was 4.7
.mu.m.
[0111] The polishing rate and the number of scratches were
evaluated in the same manner as in Example 1 except that the above
polishing pad was used. As a result, the polishing rate was 185
nm/min and no scratch was observed.
Example 4
[0112] 56 parts by volume (equivalent to 48 parts by mass) of
1,2-polybutadiene (manufactured by JSR Corporation, trade name of
JSR RB830), 14 parts by volume (equivalent to 12 parts by mass) of
polystyrene (manufactured by A and Enstyrene Co., Ltd., trade name
of GPPS HF55) and 30 parts by volume (equivalent to 40 parts by
mass) of .beta.-cyclodextrin (manufactured by of Bio Research
Corporation of Yokohama, trade name of Dexy Pearl .beta.-100,
average particle diameter of 20 .mu.m) as water-soluble particles
were kneaded together by an extruder set at 160.degree. C.
Thereafter, 0.5 part by volume (equivalent to 0.56 part by mass) of
dicumyl peroxide (manufactured by NOF Corporation, trade name of
Percumyl D) was added to and kneaded with the above kneaded product
at 120.degree. C. to obtain a pellet. The resulting kneaded product
then was heated in a metal mold at 180.degree. C. for 10 minutes to
be crosslinked so as to obtain a disk-like molded product having a
diameter of 600 mm and a thickness of 2.8 mm. Concentrically
circular grooves having a width of 0.5 mm and a depth of 1.4 mm
were formed in the polishing surface of this molded product at a
pitch of 2.0 mm by using a cutting machine manufactured by Kato
Machinery Co., Ltd. (first group of grooves). Further, a second
group of grooves were formed in the same manner as in Example 2
except that the depth of the grooves was changed to 1.4 mm. The
surface roughness of the inner wall of each of the formed grooves
was 3.5 .mu.m.
Example 5
[0113] A chemical mechanical polishing pad was manufactured in the
same manner as in Example 1 except that 4 linear grooves (having a
width of 1.0 mm and a depth of 1.0 mm) were formed from the center
to the periphery of the pad as a second group of grooves in such a
manner that they were in contact with one another at the center of
the polishing surface of the pad and the angle between adjacent
linear grooves was 90.degree., that 28 linear grooves were formed
from a portion 25 mm away from the center to the peripheral end of
the pad in such a manner that the angle between adjacent linear
grooves was 11.25.degree. and that 32 linear grooves were formed
from a portion 75 mm away from the center to the peripheral end of
the pad in such a manner that the angle between adjacent linear
grooves was 5.625.degree.. The arrangement of the formed grooves is
shown in the diagram of FIG. 8. The surface roughness of the inner
wall of each of the formed grooves was 4.0 .mu.m.
[0114] When the polishing rate and the number of scratches were
evaluated in the same manner as in Example 1 except that the above
polishing pad was used, the polishing rate was 225 nm/min and no
scratch was observed.
Example 6
[0115] 80 parts by volume (equivalent to 72 parts by mass) of
1,2-polybutadiene (manufactured by JSR Corporation, trade name of
JSR RB830) and 20 parts by volume (equivalent to 28 parts by mass)
of .beta.-cyclodextrin (manufactured by Bio Research Corporation of
Yokohama, trade name of Dexy Pearl .beta.-100, average particle
diameter of 20 .mu.m) as water-soluble particles were kneaded
together by an extruder set at 160.degree. C. Thereafter, 0.12 part
by volume (equivalent to 0.13 part by mass) of dicumyl peroxide
(manufactured by NOF Corporation, trade name of Percumyl D) was
added to and kneaded with the above kneaded product at 120.degree.
C. to obtain a pellet. The resulting kneaded product was then
heated in a metal mold at 170.degree. C. for 18 minutes to be
crosslinked so as to obtain a disk-like molded product having a
diameter of 800 mm and a thickness of 2.5 mm. The same grooves as
in Example 1 were formed in this molded product. The surface
roughness of the inner wall of each of the formed grooves was 3.5
.mu.m. A center portion having a diameter of 600 mm was cut out
from this polishing pad having a diameter of 800 mm to evaluate the
polishing rate and the number of scratches in the same manner as in
Example 1. As a result, the polishing rate was 254 nm/min and no
scratch was observed.
Example 7
[0116] A chemical mechanical polishing pad was manufactured in the
same manner as in Example 2 except that 28 pairs of linear grooves
were formed with an interval between the grooves of each pair of 2
mm in place of the 28 linear grooves in Example 2. The grooves are
shown in the diagram of FIG. 9. The polishing rate and the number
of scratches were evaluated in the same manner as in Example 1
except that this polishing pad was used. As a result, the polishing
rate was 233 nm/min and no scratch was observed.
[0117] Since the paired linear grooves were formed from the center
portion to the peripheral portion of the pad with an interval
between the grooves of each pair of 2 mm, it is understood that the
paired linear grooves slightly shifted from the diameter direction
of the pad though they started from the center portion of the
pad.
Example 8
[0118] 28.2 parts by mass of polytetramethylene glycol having two
hydroxyl groups at both terminals of the molecule and a number
average molecular weight of 650 (manufactured by Mitsubishi
Chemical Co., Ltd., trade name of PTMG650) and 21.7 parts by mass
of 4,4'-diphenylmethane diisocyanate (manufactured by Sumika Bayer
Urethane Co., Ltd., trade name of Sumidule 44S) were fed to a
reactor and maintained at 90.degree. C. for 3 hours under agitation
to carry out a reaction, and then cooled to obtain a prepolymer
having an isocyanate group at both terminals.
[0119] 14.5 parts by mass of .beta.-cyclodextrin (manufactured by
Bio Research Corporation of Yokohama, trade name of Dexy Pearl
.beta.-100, average particle diameter of 20 .mu.m) as water-soluble
particles was dispersed into 21.6 parts by mass of polypropylene
glycol having three hydroxyl groups and a number average molecular
weight of 330 (manufactured by NOF Corporation, trade name of Uniol
TG300, addition reaction product of glycerin and propylene oxide)
and 6.9 parts by mass of the PTMG650 polytetramethylene glycol as
crosslinking agents by agitation, and further 0.1 part by mass of
2-methyl triethylenediamine (manufactured by Sankyo Air Products
Co., Ltd., trade name of Me-DABCO) was dissolved in the obtained
dispersion as a reaction accelerator by agitation. The resulting
mixture was added to the reactor of the above prepolymer having an
isocyanate group at both terminals.
[0120] Further, 21.6 parts by mass of the Sumidule 44S
4,4'-diphenylmethane diisocyanate was added to the above reactor of
the prepolymer having an isocyanate group at both terminals,
stirred at 200 rpm at room temperature for 2 minutes and defoamed
under reduced pressure to obtain a raw material mixture.
[0121] This raw material mixture was injected into a metal mold
having a diameter of 60 cm and a thickness of 3 mm and maintained
at 80.degree. C. for 20 minutes to carry out the polymerization of
polyurethane and further post-cured at 110.degree. C. for 5 hours
to obtain a molded product having a diameter of 600 mm and a
thickness of 2.5 mm. Thereafter, the same grooves as in Example 1
were formed in this molded product. The surface roughness of the
inner wall of each of the formed grooves was 3.0 .mu.m.
[0122] The polishing rate and the number of scratches were
evaluated in the same manner as in Example 1 except that the above
polishing pad was used. As a result, the polishing rate was 231
nm/min and no scratch was observed.
Comparative Example 1
[0123] A disk-like molded product as large as that of Example 1 was
produced in the same manner as in Example 1 in order to manufacture
a chemical mechanical polishing pad in the same manner as in
Example 1 except that only concentrically circular grooves (first
group of grooves) having a width of 0.5 mm, a pitch of 2.0 mm and a
depth of 1.0 mm were formed in the polishing surface by using a
commercially available cutting machine. The surface roughness of
the inner wall of each of the formed grooves was 4.8 .mu.m.
[0124] The polishing rate and the existence of scratches were
evaluated in the same manner as in Example 1 except that this
polishing pad was used. As a result, the polishing rate was 200
nm/min and 15 scratches were seen.
Comparative Example 2
[0125] A disk-like molded product as large as that of Example 1 was
produced in the same manner as in Example 1 in order to manufacture
a chemical mechanical polishing pad in the same manner as in
Example 1 except that the first group of concentrically circular
grooves were not formed and only the second group of grooves were
formed in the polishing surface. The surface roughness of the inner
wall of each of the formed grooves was 4.5 .mu.m.
[0126] The polishing rate and the existence of scratches were
evaluated in the same manner as in Example 1 except that this
polishing pad was used. As a result, the polishing rate was 120
nm/min and 25 scratches were seen.
Comparative Example 3
[0127] A disk-like molded product as large as that of Example 1 was
produced in the same manner as in Example 1 in order to manufacture
a chemical mechanical polishing pad in the same manner as in
Example 1 except that grooves having a width of 1.0 mm and a depth
of 1.0 mm were formed in a lattice in the polishing surface at a
pitch of 10.0 mm by using a commercially available cutting machine.
The surface roughness of the inner wall of each of the formed
grooves was 5.5 .mu.m.
[0128] The polishing rate and the existence of scratches were
evaluated in the same manner as in Example 1 except that this
polishing pad was used. As a result, the polishing rate was 150
nm/min and 50 scratches were seen.
[0129] As described above, the chemical mechanical polishing pad of
the present invention fully suppresses the occurrence of a scratch
on the polished surface and has an excellent polishing rate, and
the chemical mechanical polishing method making use of the
polishing pad of the present invention provides a polished object
having an excellent surface state at a high polishing rate.
* * * * *