U.S. patent application number 11/110728 was filed with the patent office on 2005-10-27 for chemical mechanical polishing pad, manufacturing process thereof and chemical mechanical polishing method.
This patent application is currently assigned to JSR Corporation. Invention is credited to Hosaka, Yukio, Kawahashi, Nobuo, Shiho, Hiroshi, Shimoyama, Yuuji.
Application Number | 20050239380 11/110728 |
Document ID | / |
Family ID | 34935462 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050239380 |
Kind Code |
A1 |
Hosaka, Yukio ; et
al. |
October 27, 2005 |
Chemical mechanical polishing pad, manufacturing process thereof
and chemical mechanical polishing method
Abstract
A chemical mechanical polishing pad having a polishing surface
with an arithmetic mean roughness (Ra) of 0.1 to 15 .mu.m, a
10-point height (Rz) of 40 to 150 .mu.m, a core roughness depth
(Rk) of 12 to 50 .mu.m and a reduced peak height (Rpk) of 7 to 40
.mu.m, a manufacturing process thereof and a chemical mechanical
polishing method. Even when the chemical mechanical polishing of a
large-diameter wafer as an object to be polished is carried out by
this pad, a polished surface having excellent in-plane uniformity
and flatness can be formed.
Inventors: |
Hosaka, Yukio; (Chuo-ku,
JP) ; Shimoyama, Yuuji; (Chuo-ku, JP) ; Shiho,
Hiroshi; (Chuo-ku, JP) ; Kawahashi, Nobuo;
(Chuo-ku, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JSR Corporation
Tokyo
JP
|
Family ID: |
34935462 |
Appl. No.: |
11/110728 |
Filed: |
April 21, 2005 |
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24B 37/04 20130101;
B24B 37/042 20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2004 |
JP |
2004-125064 |
Claims
What is claimed is:
1. A chemical mechanical polishing-pad having a polishing surface
and a nonpolishing surface, the polishing surface having an
arithmetic mean roughness (Ra) of 0.1 to 15 .mu.m, a 10-point
height (Rz) of 40 to 150 .mu.m, a core roughness depth (Rk) of 12
to 50 .mu.m and a reduced peak height (Rpk) of 7 to 40 .mu.m.
2. The chemical mechanical polishing pad according to claim 1
having a thickness distribution of 50 .mu.m or less.
3. A process of manufacturing the chemical mechanical polishing pad
of claim 1 or 2, comprising the steps of: molding a polishing
layer; and sanding at least the surface to be polishing surface of
the polishing layer.
4. A chemical mechanical polishing method comprising chemical
mechanical polishing an object to be polished with the chemical
mechanical polishing pad of claim 1 or 2.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a chemical mechanical
polishing pad, a manufacturing process thereof and a chemical
mechanical polishing method.
[0002] More specifically, it relates to a chemical mechanical
polishing pad capable of providing a polished surface having
excellent in-plane uniformity and flatness when chemical mechanical
polishing is made on the surface, a manufacturing process thereof
and a chemical mechanical polishing method using the above chemical
mechanical polishing pad.
DESCRIPTION OF THE PRIOR ART
[0003] In the process for the manufacture of a semiconductor
device, CMP (Chemical Mechanical Polishing) is employed as a
technique capable of providing an extremely flat surface to a
wafer. CMP is a technique for the chemical mechanical polishing of
a surface by letting chemical mechanical polishing slurry which is
an aqueous dispersion of abrasive grains flow down over the surface
of a chemical mechanical polishing pad while the surface to be
polished is pressed against and brought into slide contact with the
surface of the chemical mechanical polishing pad. It is known that
the polishing result is greatly affected by the performance
characteristic and properties of the chemical mechanical polishing
pad in this CMP.
[0004] There are known chemical mechanical polishing pads such as a
polyurethane foamed resin pad containing a large number of pores
and a pad containing a large number of fine water-soluble particles
dispersed in a nonfoamed matrix (the former is disclosed by JP-A
11-70463 and JP-A 8-216029 and the latter is disclosed by JP-A
2000-34416, JP-A 2000-33552 and JP-A 2001-334455) (the term "JP-A"
as used herein means an "unexamined published Japanese patent
application").
[0005] Since the improvement of productivity is now desired in the
process for the manufacture of a semiconductor, a wafer which needs
chemical mechanical polishing is becoming larger in diameter.
[0006] When chemical mechanical polishing is made on a
large-diameter wafer by a conventionally known method, the in-plane
uniformity and flatness of the polished surface after chemical
mechanical polishing may become unsatisfactory.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention which has been made
in view of the above problem to provide a chemical mechanical
polishing pad capable of providing a polished surface having
excellent in-plane uniformity and flatness even when chemical
mechanical polishing is made on a large-diameter wafer as an object
to be polished, a manufacturing process thereof and a chemical
mechanical polishing method.
[0008] Other objects and advantages of the present invention will
become apparent from the following description.
[0009] According to the present invention, firstly, the above
objects and advantages of the present invention are attained by a
chemical mechanical polishing pad having a polishing surface and a
non-polishing surface, the polishing surface having an arithmetic
mean roughness (Ra) of 0.1 to 15 .mu.m, a 10-point height (Rz) of
40 to 150 .mu.m, a core roughness depth (Rk) of 12 to 50 .mu.m and
a reduced peak height (Rpk) of 7 to 40 .mu.m.
[0010] Secondly, the above objects and advantages of the present
invention are attained by a process of manufacturing the above
chemical mechanical polishing pad, comprising the steps of:
[0011] molding a polishing layer; and
[0012] sanding at least the surface to be polishing surface of the
polishing layer.
[0013] Thirdly, the above objects and advantages of the present
invention are attained by a chemical mechanical polishing method
comprising chemical mechanical polishing an object to be polished
with the above chemical mechanical polishing pad.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a diagram showing the definition of 10-point
height (Rz);
[0015] FIG. 2 is a diagram showing the definition of a material
ratio curve;
[0016] FIG. 3 is a diagram showing the definition of core roughness
depth (Rk); and
[0017] FIG. 4 is a diagram showing the definition of reduced peak
height (Rpk).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] The polishing surface of the chemical mechanical polishing
pad of the present invention has an arithmetic mean roughness (Ra)
of 0.1 to 15 .mu.m, a 10-point height (Rz) of 40 to 150 .mu.m, a
core roughness depth (Rk) of 12 to 50 .mu.m and a reduced peak
height (Rpk) of 7 to 40 .mu.m.
[0019] These values are defined as the averages of the following
numerical values calculated from roughness profiles obtained by
measuring a plurality of measurement lines set on the surface of
the pad. For example, they can be calculated by a method disclosed
by LM Manual (analog version), Version 3.62 published by Mitsuya
Shoji Co., Ltd.
[0020] The arithmetic mean roughness (Ra) is a value expressed by
the following equation (1) when the x axis of the roughness profile
of an evaluation length L is plotted in the direction parallel to
the mean line of the roughness profile, the y axis is plotted in
the direction of the longitudinal magnification of the roughness
profile, and the measured roughness profile is expressed by the
equation y=f(x). 1 Ra = 1 L 0 L y x ( 1 )
[0021] The 10-point height (Rz) is a value expressed by the
following equation (2) when the x axis of the roughness profile of
the evaluation length L is plotted in the direction parallel to the
mean line of the roughness profile, they axis is plotted in the
direction of the longitudinal magnification of the roughness
profile, the distances of the tops of the highest mountain to the
fifth highest mountain from the mean line in the direction of the
longitudinal magnification are represented by P1 to P5, and the
distances to the bottoms of the lowest valley to the fifth lowest
valley from the mean line are represented by V1 to V5, respectively
(see FIG. 1). 2 Rz = 1 5 ( i = 1 5 Pi - i = 1 5 Vi ) ( 2 )
[0022] The core roughness depth (Rk) and the reduced peak height
(Rpk) are defined by a material ratio curve derived from the
roughness profile of the evaluation length L.
[0023] The material ratio curve refers to a curve obtained by
plotting a section level as the longitudinal axis and a material
ratio as the horizontal axis. The term "section level" used herein
means a specific value of y when the roughness profile is expressed
by the same equation y=f(x) as in the above arithmetic mean
roughness (Ra). The term "material ratio" is a percentage of the
length of a cut portion to the evaluation length L when the
roughness profile is cut at a certain section level. The material
ratio is 0% when the section level is at the top of the highest
mountain in the roughness profile and 100% when the section level
is at the bottom of the lowest valley (see FIG. 2).
[0024] The core roughness depth (Rk) is a difference in section
level between points C and D when two points A and B the difference
in material ratio between which is 40% and the difference in
section level between which is the smallest are set on the material
ratio curve defined as described above, the point C is the
intersection between a straight line connecting the points A and B
and extending in both-directions and a line representing a material
ratio of 0%, and the point D is the intersection between the
straight line connecting the points A and B and a line representing
a material ratio of 100% (see FIG. 3).
[0025] The reduced peak height (Rpk) is a difference in section
level between the points C and J when the intersection between the
section level passing through the point C in the definition of the
above core roughness depth (Rk) and the material ratio curve is a
point H, the intersection between the material ratio curve and the
line representing a material ratio of 0% is point I, and a point J
is set on a straight line representing a material ratio of 0% to
ensure that the area surrounded by the line segment CH, line
segment CI and the curve HI becomes equal to the area of the
triangle CHJ (see FIG. 4. A1 in FIG. 4 is the area surrounded by
the line segment CH, line segment CI and the curve HI, that is, the
area of the triangle CHJ).
[0026] A plurality of measurement lines for measuring the above
arithmetic mean roughness (Ra), 10-point height (Rz), core
roughness depth (Rk) and reduced peak height (Rpk) are set on the
pad as follows.
[0027] First, the center points of the plurality of measurement
lines are set as follows. As for the center points of the
measurement lines, virtual straight lines whose length becomes the
longest are drawn from one arbitrary point at one end of the
polishing surface of the pad to another point (when the polishing
surface of the pad is circular, the above virtual straight lines
become the diameter of a circle forming the pad surface) to set 10
to 50 points on the virtual straight lines at roughly equal
intervals except for a 5% area of the length of the virtual
straight line from the center to the both sides and 5% areas of the
length of the virtual straight line from the both ends. The number
of the center points of the measurement lines is preferably 25 to
50.
[0028] A groove(s) may be formed in the polishing surface of the
chemical mechanical polishing pad of the present invention as will
be described hereinafter. In this case, the center points of the
measurement lines should be set such that the all the measurement
lines set as will be described hereinafter are existent in a
portion other than the groove(s) in the polishing surface. 10 to 50
measurement points may not be set at roughly equal intervals on the
above virtual straight lines according to the shape of the
groove(s) formed in the polishing surface. In this case, out of the
points set at equal intervals, the above number of points may be
secured by excluding the points of the measurement lines partially
overlapping with the groove portion. Straight lines intersecting
the virtual straight lines for setting the plurality of points and
passing through the "center points of the measurement lines" are
assumed and taken as measurement lines. The length of the
measurement lines may be 1 to 15 mm with the center point of the
above measurement line as the center thereof.
[0029] The above roughness profile can be measured by using a
commercially available surface roughness meter.
[0030] As for the chemical mechanical polishing pad of the present
invention, the arithmetic mean roughness (Ra) of the polishing
surface thus measured is 0.1 to 15 .mu.m. This value is preferably
0.1 to 12 .mu.m. The 10-point height (Rz) is 40 to 150 .mu.m. It is
preferably 40 to 130 .mu.m. The core roughness depth (Rk) is 12 to
50 .mu.m. It is preferably 12 to 45 .mu.m. The reduced peak height
(Rpk) is 7 to 40 .mu.m. It is preferably 7 to 30 .mu.m.
[0031] When the chemical mechanical polishing step is carried out
by using the chemical mechanical polishing pad having these values,
a polished surface having excellent in-plane uniformity and
flatness can be obtained. This effect is marked particularly when a
large-diameter wafer is chemically mechanically polished.
[0032] The chemical mechanical polishing pad of the present
invention preferably has a thickness distribution of 50 .mu.m or
less. The effect of the present invention is advantageously
exhibited by setting the thickness distribution of the chemical
mechanical polishing pad to 50 .mu.m or less. This value is more
preferably 40 .mu.m or less, particularly preferably 30 .mu.m or
less. By setting the thickness distribution of the chemical
mechanical polishing pad to this range, even when a large-diameter
wafer as an object to be polished is chemically mechanically
polished, a polished surface having excellent in-plane uniformity
and flatness can be obtained.
[0033] The thickness distribution can be calculated from the
following equation by measuring the thickness at a plurality of
measurement points set on the surface of the pad.
Thickness distribution=(largest measurement value of
thickness)-(smallest measurement value of thickness)
[0034] 10 to 50 measurement points are set at equal intervals on
virtual straight lines drawn from one arbitrary point at one end of
the polishing surface of the pad to another point such that its
length becomes the largest (when the polishing surface of the pad
is circular, the above virtual straight lines become the diameter
of a circle forming the pad surface) excluding a 5% area of the
length of the virtual straight line from the center to the both
sides and 5% areas of the length of the virtual straight line from
the both ends. The number of measurement points is preferably 25 to
50.
[0035] A groove(s) may be formed in the polishing surface of the
chemical mechanical polishing pad of the present invention as will
be described hereinafter. In this case, the measurement points
should be set in a portion other than the groove(s) on the
polishing surface. There is a case where 10 to 50 measurement
points cannot be set at roughly equal intervals on the above
virtual straight lines according to the shape of the groove(s)
formed in the polishing surface. In this case, out of the points
set at roughly equal intervals, the above number of measurement
points may be secured by excluding points in the groove(s).
[0036] The thickness at each measurement point can be known by
placing the chemical mechanical polishing pad on a horizontal plane
and measuring the distance between the measurement point and the
horizontal plane. A contact type distance meter may be used to
measure the distance between the measurement point and the
horizontal plane. One of commercially available products of the
above meter is Manual 3-D Meter (of Mitutoyo Corporation).
[0037] The shape of the chemical mechanical polishing pad of the
present invention is not particularly limited. It may be disk-like,
belt-like or roller-like. Preferably, the shape of the chemical
mechanical polishing pad is suitably selected according to a
polishing machine. The size of the chemical mechanical polishing
pad before use is not particularly limited. A disk-like chemical
mechanical polishing pad had a diameter of, for example, 0.5 to 500
cm, preferably 1.0 to 250 cm, more preferably 20 to 200 cm. It has
a thickness of, for example, more than 0.1 mm and 100 mm or less,
particularly preferably 1 to 10 mm.
[0038] The chemical mechanical polishing pad of the present
invention may have a groove(s) or recessed portion(s) having an
arbitrary shape in the polishing surface. The groove(s) or recessed
portion(s) serves to hold an aqueous dispersion for chemical
mechanical polishing supplied during chemical mechanical polishing
and uniformly distribute it to the polished surface of an object to
be polished, retains wastes such as chips and polishing liquid
waste generated by chemical mechanical polishing temporarily and
becomes a route for discharging the wastes to the outside.
[0039] The shape of the above groove(s) is not particularly limited
but may be circular, lattice-like or radial. The shape of the above
recessed portion(s) is circular or polygonal. The sectional form of
the grobve(s) or recessed portion(s) is not particularly limited.
It may be, for example, rectangular, trapezoidal, U-shaped or
V-shaped.
[0040] The number of the grooves or the recessed portions may be
one or more.
[0041] The size of the above groove(s) or recessed portion(s) is
not particularly limited. The width of the groove(s) or the
shortest diameter of the recessed portion(s) may be, for example,
0.1 mm or more, specifically 0.1 to 0.5 mm, more specifically 0.2
to 3.0 mm. The depth of the groove(s) or the recessed portion(s)
may be, for example, 0.1 mm or more, specifically 0.1 to 2.5 mm,
more specifically 0.2 to 2.0 mm.
[0042] The surface roughness of the inner wall of the above
groove(s) or recessed portion(s) is preferably 20 .mu.m or less,
more preferably 15 .mu.m or less. By setting the surface roughness
of the inner wall of the groove(s) or recessed portion(s) to this
range, when chemical mechanical polishing is carried out with this
pad, it is possible to prevent the polished surface of the object
from being scratched and to contribute to the improvement of the
polishing rate and the service life of the polishing pad. The
improvement of the polishing rate by setting the surface roughness
of the inner wall of the groove(s) or recessed portion(s) to the
above range is assumed to be because the function of distributing
an aqueous dispersion for chemical mechanical polishing to the
polished surface is carried out better. The improvement of the
service life of the polishing pad by setting the surface roughness
of the inner wall of the groove(s) or recessed portion(s) to the
above range is assumed to be because the function of discharging
wastes generated by chemical mechanical polishing is carried out
more efficiently.
[0043] The above surface roughness can be measured with an optical
surface roughness meter or contact type surface roughness meter.
Examples of the above optical surface roughness meter include a 3-D
surface structural analytical microscope, scanning laser microscope
and electron beam surface form analyzer. Examples of the above
contact type surface roughness meter include a tracer type surface
roughness meter.
[0044] The chemical mechanical polishing pad of the present
invention may further have a groove(s) or recessed portion(s) on
the non-polishing surface (rear side of the pad).
[0045] The groove(s) or recessed portion(s) contributes to the
suppression of the production of a surface defect on the polished
surface in the chemical mechanical polishing step. It is assumed
that even when foreign matter such as coarse particles which may be
contained in the aqueous dispersion for chemical mechanical
polishing or cutting chips derived from the production process of
the chemical mechanical polishing pad enter between the polishing
pad and the object to be polished, the recessed portion(s) serves
to ease excessively large pressure generated locally to thereby
reduce the number of surface defects on the polished surface.
[0046] The shape of the above groove(s) or recessed portion(s) is
not particularly limited. The shape of the groove(s) may be spiral,
annular or lattice-like. The shape of the recessed portion(s) may
be circular or polygonal.
[0047] The size of the groove(s) or recessed portion(s) may be
arbitrary. When the recessed portion(s) is/are circular, it/they
may have a diameter of 1 to 300 mm, specifically 5 to 200 mm, more
specifically 10 to 150 mm. When the groove(s) is/are spiral,
annular or lattice-like, it/they may have a width of 0.1 to 20 mm,
specifically 0.1 to 10 mm. The depth of the groove(s) or recessed
portion(s) may be, for example, 0.01 to 2.0 mm, specifically 0.1 to
1.5 mm, more specifically 0.1 to 1.0 mm regardless of its/their
shape.
[0048] The number of the grooves or recessed portions may one or
more.
[0049] The chemical mechanical polishing pad of the present
invention has a thickness distribution of 50 .mu.m or less as
described above and optionally has a groove(s) or recessed
portion(s) in the polishing surface and/or the non-polishing
surface. Although the process for manufacturing the pad is not
particularly limited, the pad can be manufactured by a process
comprising the following steps, for example.
[0050] (1) the step of preparing a composition for a chemical
mechanical polishing pad;
[0051] (2) the step of molding the above composition for a chemical
mechanical polishing pad into a polishing layer; and
[0052] (3) the step of sanding at least the polishing surface of
the above polishing layer.
[0053] A detailed description is subsequently given of each of the
above steps.
[0054] (1) Step or Preparing a Composition for a Chemical
Mechanical Polishing Pad
[0055] The chemical mechanical polishing pad of the present
invention may be made of any material as far as the object of the
present invention can be attained. It is preferred that pores
having the function of holding an aqueous dispersion for chemical
mechanical polishing during chemical mechanical polishing and the
function of retaining polishing chips temporarily out of the
functions of the chemical mechanical polishing pad should be formed
by the time of polishing. Therefore, the chemical mechanical
polishing pad is preferably made of a material consisting of
water-soluble particles and a water-insoluble matrix containing the
water-soluble particles dispersed therein, or a material consisting
of cavities and a water-insoluble matrix material containing the
cavities dispersed therein, for example, a foam.
[0056] In the former material out of these, the water-soluble
particles come into contact with an aqueous medium of slurry
containing the aqueous medium and a solid at the time of polishing
and dissolve or swell to be eliminated, and the slurry can be held
in pores formed by elimination. In the latter material, the slurry
can be held in pores formed as the cavities.
[0057] The material of the above "water-insoluble matrix" is not
particularly limited but an organic material is preferred 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.
[0058] 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.
[0059] 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
polyurethane elastomers (TPU), thermoplastic elastomers such as
polyester elastomers (TPEE) and polyamide elastomers (TPAE),
silicone resin elastomers and fluororesin elastomers. The rubbers
include conjugated diene rubbers such as butadiene rubber (high
cis-butadiene rubber, low cis-butadiene rubber, etc.), isoprene
rubber, styrene-butadiene rubber and styrene-isoprene rubber,
nitrile rubbers such as acrylonitrile-butadiene rubber, acrylic
rubber, ethylene-.alpha.-olefin rubbers such as ethylene-propylene
rubber and ethylene-propylene-diene rubber, other rubbers such as
butyl rubber, silicone rubber and fluorine rubber.
[0060] 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.
[0061] The above organic materials may be modified by an acid
anhydride group, carboxyl group, hydroxyl group, epoxy group or
amino group. The affinity for the water-soluble particles to be
described hereinafter and slurry of the organic material can be
adjusted by modification.
[0062] These organic materials may be used alone or in combination
of two or more.
[0063] Further, 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 chemical mechanical polishing pad
during polishing can be reduced. Further, it is possible to
effectively prevent the pores from being plastically deformed by
the excessive extension of the water-insoluble matrix during
polishing and dressing and the surface of the chemical mechanical
polishing pad from being excessively napped. Therefore, the pores
are formed efficiently even during dressing, whereby a reduction in
the retainability of the slurry during polishing can be suppressed
and further the pad is rarely napped, 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.
[0064] The crosslinked polymer may be a crosslinked rubber, curable
resin, crosslinked thermosetting resin or crosslinked elastomer out
of the above organic materials. Out of these, 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 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.
[0065] The content of the crosslinked polymer is not particularly
limited but preferably 30 vol % or more, more preferably 50 vol %
or more, particularly preferably 70 vol % or more and may be 100
vol % of the water-insoluble matrix. When the content of the
crosslinked polymer in the water-insoluble matrix is lower than 30
vol %, the effect obtained by containing the crosslinked polymer
may not be fully obtained.
[0066] The residual elongation after breakage (to be simply
referred to as "residual elongation at break" hereinafter) of the
above water-insoluble matrix containing a crosslinked polymer can
be 100% or less when a specimen of the above water-insoluble matrix
is broken at 80.degree. C. in accordance with JIS K 6251. That is,
the total distance between bench marks of the specimen after
breakage becomes 2 times or less the distance between the bench
marks before breakage. This residual elongation at break is
preferably 30% or less, more preferably 10% or less, particularly
preferably 5% or less and generally 0% or more. When the above
residual elongation at break is higher than 100%, fine pieces
scraped off from the surface of the chemical mechanical 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.
[0067] The above "water-soluble particles" are particles which are
eliminated from the water-insoluble matrix when they come into
contact with slurry as an aqueous dispersion in the chemical
mechanical 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.
[0068] The water-soluble particles have the effect of increasing
the indentation hardness of the chemical mechanical polishing pad
in addition to the effect of forming pores. For example, the shore
D hardness of the chemical mechanical polishing pad of the present
invention can be set to preferably 35 or more, more preferably 50
to 90, particularly preferably 60 to 85 and generally 100 or less
by adding the water-soluble particles. When the shore D hardness is
35 or more, pressure applied to the object to be polished can be
increased, and the polishing rate can be thereby improved. In
addition, high polishing flatness is obtained. Therefore, the
water-soluble particles are particularly preferably made of a solid
substance which can ensure sufficiently high indentation hardness
for the chemical mechanical polishing pad.
[0069] The material of 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 for forming 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 for forming 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.
[0070] 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 chemical mechanical 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
chemical mechanical polishing pad may lower.
[0071] The content of the water-soluble particles is preferably 1
to 90 vol %, more preferably 1 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
content of the water-soluble particles is lower than 1 vol %, pores
are not fully formed in the obtained chemical mechanical polishing
pad and the polishing rate may lower. When the content of the
water-soluble particles is higher than 90 vol %, it may be
difficult to completely prevent the water-soluble particles
existent in the interior of the obtained chemical mechanical
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.
[0072] It is preferred that the water-soluble particles should
dissolve in water only when they are exposed to the surface layer
of the chemical mechanical polishing pad and should not absorb
moisture or swell when they are existent in the interior of the
chemical mechanical 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.
[0073] 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.
[0074] The water-insoluble matrix material constituting the
chemical mechanical polishing pad comprising the latter
water-insoluble matrix material (foam, etc.) containing cavities
dispersed therein is, for example, a polyurehane, melamine resin,
polyester, polysulfone or polyvinyl acetate.
[0075] The average size of the cavities dispersed in the
water-insoluble matrix material is preferably 0.1 to 500 .mu.m,
more preferably 0.5 to 100 .mu.m.
[0076] There is a case where a chemical mechanical polishing pad
comprising a water-insoluble matrix material containing cavities
dispersed therein, for example, a foam may not satisfy the
requirements for the arithmetic mean roughness (Ra), 10-point
height (Rz), core roughness depth (Rk) and reduced peak height
(Rpk) of the pad surface that the chemical mechanical polishing pad
of the present invention should have according to the sizes of the
cavities. Therefore, the chemical mechanical polishing pad of the
present invention preferably has a polishing layer made of a
material consisting of water-soluble particles and a
water-insoluble matrix containing the water-soluble particles
dispersed therein.
[0077] The method of obtaining the composition for a chemical
mechanical polishing pad from the above material 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).
[0078] The composition for a chemical mechanical polishing pad
containing water-soluble particles for obtaining a chemical
mechanical polishing pad containing 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 the 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, in this case, the type of the
water-soluble particles is preferably selected according to the
processing temperature of the water-insoluble matrix in use.
[0079] (2) Step of Molding a Polishing Layer from the Composition
for a Chemical Mechanical Polishing Pad
[0080] The method of forming a polishing layer which should become
the chemical mechanical polishing pad of the present invention is
not particularly limited. For example, the composition for a
chemical mechanical polishing pad which will become a polishing
layer is prepared and molded into a desired rough form to produce
the polishing layer. At this point, a metal mold having a pattern
which should become a groove(s) and/or recessed portion(s) to be
formed on the front surface and/or rear surface of the polishing
layer is used to mold the composition for a chemical mechanical
polishing pad, thereby making it possible to form the groove(s)
and/or recessed portion(s) together with the rough form of the
polishing layer at the same time. When the groove(s) and/or
recessed portion(s) are/is formed by molding, this step can be
simplified and the surface roughness of the inner wall of the
groove(s) and/or recessed portion(s) can be made 20 .mu.m or less
easily.
[0081] The groove(s) and/or recessed portion(s) on the front
surface and/or rear surface of the polishing layer may be formed by
cutting or counterboring after a polishing layer having none of
them is produced. To form the groove(s) and/or recessed portion(s)
by cutting or counterboring, the step of forming the groove(s)
and/or recessed-portion(s) may be carried out before or after (3)
the sanding step which will be described next.
[0082] (3) Step of Sanding at Least the Polishing Surface of the
Above Polishing Layer
[0083] Thereafter, at least the polishing surface of the thus
formed polishing layer is sanded.
[0084] The term "sanding" means polishing with sandpaper. The
sandpaper is obtained by bonding abrasive grains to a backing
material such as sheet-like or belt-like paper or cloth by an
adhesive. The material of the abrasive grains is fine crystals of a
natural mineral or fine grains of an artificial inorganic compound.
Examples of the natural mineral include emery and garnet and
examples of the artificial inorganic compound include aluminum
oxide and silicon carbide.
[0085] The size of the abrasive grains used for the above sanding
step is preferably 20 to 200 .mu.m, more preferably 25 to 150
.mu.m. The grit size of the sandpaper is preferably 80 to 600, more
preferably 120 to 400.
[0086] Sandpaper having a larger width than the polishing surface
of the above polishing layer is preferably used for sanding.
[0087] Sanding can be carried out by fixing the above polishing
layer on a horizontal plane with the polishing surface facing up,
bringing the entire polishing surface into contact with the
sandpaper and moving the sandpaper relative to the polishing
surface at a relative rate of preferably 0.1 to 100 m/min, more
preferably 0.5 to 50 m/min. This movement may be rotational
movement or linear movement with the contact portion between the
polishing surface of the polishing layer and the sandpaper as a
standard.
[0088] The amount of the polishing layer sanded out, that is,
removed by sanding is preferably 0.05 to 3.0 mm, more preferably
0.1 to 2.0 mm.
[0089] Sanding may be carried out only with a single type of
sandpaper or with different types of sandpapers which differ in
grit size in multiple stages. Out of these, sanding is preferably
carried out with different types of sandpapers which differ in grit
size in multiple stages. The number of stages is preferably 2 to
10, more preferably 3 to 6. The thickness of the polishing layer
sanded out, that is, removed in each stage is preferably 0.01 to
1.5 mm, more preferably 0.1 to 1.0 mm. When sanding is carried out
with different types of sandpapers which differ in grit size in
multiple stages, a sandpaper having a larger grit size is
preferably first used, followed by a sandpaper having a smaller
grit size.
[0090] The above sanding can be carried out by using a sandblasting
apparatus, belt polishing machine, barrel polishing machine, puff
polishing machine, ring polishing machine, electrolytic polishing
machine or electrolytic and grain polishing machine. Out of these,
a belt polishing machine is preferably used. Commercially available
products of the belt polishing machine include the TS130D polishing
machine of Amitec Co., Ltd., the T-142DG wide belt sander of
Kikukawa Tekkosho Co., Ltd., and the wide belt sander of Meinan
Machinery Works, Inc.
[0091] A chemical mechanical polishing pad having a thickness
distribution of 50 .mu.m or less and a polishing surface with an
arithmetic mean roughness (Ra) of 0.1 to 15 .mu.m, a 10-point
height (Rz) of 40 to 150 .mu.m, a core roughness depth (Rk) of 12
to 50 .mu.m and a reduced peak height (Rpk) of 7 to 40 .mu.m can be
easily obtained by carrying out this sanding.
[0092] A description is subsequently given of the chemical
mechanical polishing method of the present invention.
[0093] The chemical mechanical polishing method of the present
invention is the same as a known chemical mechanical polishing
method except that the above chemical mechanical polishing pad of
the present invention is set in a commercially available polishing
machine.
[0094] The type of the surface to be polished is not particularly
limited but a metal film, barrier metal film or insulating film
which is a wire material may be used. Examples of the material of
the above metal film include tungsten, aluminum, copper and alloys
containing at least one of these metals. Examples of the material
of the above barrier metal film include tantalum, titanium,
tantalum nitride and titanium nitride. Examples of the material of
the insulating film include silicon oxide. The type of the aqueous
dispersion for chemical mechanical polishing should be suitably
selected according to the type of the surface to be polished and
the purpose of chemical mechanical polishing.
[0095] The object to be polished by the chemical mechanical
polishing method of the present invention is preferably a
semiconductor wafer having at least one of the above materials on
the surface to be polished. Although the semiconductor wafer may be
of any size, for the chemical mechanical polishing of a
large-diameter semiconductor wafer, the advantage of the chemical
mechanical polishing method of the present invention appears
markedly. The large-diameter semiconductor wafer means a
semiconductor wafer having a diameter larger than 8 inches,
preferably 10 inches or more.
[0096] As described above, the chemical mechanical polishing pad of
the present invention has an advantage that stability at the time
of polishing a wafer is increased by setting the surface roughness
of the pad to a certain range. That is, with a conventionally known
polishing pad, break-in dressing is necessary before a brand-new
pad is set in the polishing machine to polish a wafer. By setting
the above surface roughness, stable polishing performance is
obtained from the first wafer after the pad is set in the polishing
machine without carrying out break-in dressing or by carrying out
break-in dressing for a shorter period of time than in the prior
art.
[0097] According to the present invention, there are provided a
chemical mechanical polishing pad which can provide a polished
surface having excellent in-plane uniformity and flatness even when
chemical mechanical polishing is made on a large-diameter wafer as
an object-to be polished, a manufacturing process thereof and a
chemical mechanical polishing method.
EXAMPLES
Example 1
[0098] 98 vol % of 1,2-polybutadiene (JSR RB830 of JSR Corporation)
and 2 vol % of .beta.-cyclodextrin (Dexy Pearl .beta.-100 of Bio
Research Corporation of Yokohama) as a water-soluble substance were
kneaded together by an extruder heated at 155.degree. C.
Thereafter, Percumyl D40 (trade name, manufactured by NOF
Corporation, containing 40% by mass of dicumyl peroxide) was added
in an amount of 1.0 part by mass (equivalent to 0.4 parts by mass
in terms of pure dicumyl peroxide) based on 100 parts by mass of
1,2-polybutadiene and further kneaded with the above kneaded
product, and the resulting product was crosslinked in a press mold
at 170.degree. C. for 18 minutes to obtain a disk-like molded
product having a diameter of 810 cm and a thickness of 3.3 mm. This
molded product was set in the insertion port of a wide belt sanding
apparatus (of Meinan Machinery Works, Inc.) and moved at a rate of
0.1 m/sec to sand the surface of the molded product with sandpapers
having grit sizes of 120, 150, 220 and 320(of Novatec Co., Ltd.) by
turning a roller at a revolution of 500 rpm to remove 0.04 mm from
the surface with each step. As a result, a molded product having an
average thickness of 2.5 mm, a thickness distribution of 20 .mu.m,
an arithmetic mean roughness (Ra) of 4.4 .mu.m, a 10-point height
(Rz) of 125 .mu.m, a core roughness depth (Rk) of 16 .mu.m and a
reduced peak height (Rpk) of 14 .mu.m was obtained.
[0099] The relative speed between the molded product and the
sandpaper on the contact surface between the molded product and the
sandpaper for above sanding was 5 m/min.
[0100] The above thickness distribution was calculated based on the
following equation from thicknesses measured at 33 points equally
apart from one another of the polishing surface of the molded
product in the diameter direction excluding a 40 mm area from the
center to the both sides and 40 mm areas from the both ends by the
manual 3-D meter (of Mitutoyo Corporation).
Thickness distribution=(largest measurement value of
thickness)-(smallest measurement value of thickness)
[0101] The arithmetic mean roughness (Ra), 10-point height (Rz),
core roughness depth (Rk) and reduced peak height (Rpk) are all
average values calculated from the roughness profiles obtained by
measuring 10 measurement lines (evaluation length of 10 mm)
perpendicular to the diameter direction of the pad with 10 points
equally apart from one another in the diameter direction of the
polishing surface of the molded product excluding 40 mm areas from
the both ends as the centers by the 1LM21P of Laser Tech Co.,
Ltd.
[0102] Concentric grooves having a width of 0.5 mm, a pitch of 2 mm
and a depth of 1.0 mm were formed in the sanded surface of the
molded product with a cutting machine (of Kato Machinery Co., Ltd.)
to manufacture a chemical mechanical polishing pad. The surface
roughness of the inner walls of the grooves was 6 .mu.m.
[0103] This chemical mechanical polishing pad was set in the
Applied Reflexion chemical mechanical polishing machine of Applied
Material Co., Ltd. to carry out break-in dressing while deionized
water was supplied under the following conditions.
[0104] Revolution of platen: 120 rpm
[0105] Supply rate of deionized water: 100 ml/min
[0106] Polishing time: 600 seconds
[0107] Thereafter, chemical mechanical polishing was made on a
12-inch wafer having a PETEOS film as an object to be polished
under the following conditions. The PETEOS film was a silicon oxide
film formed from tetraethyl silicate (TEOS) by a chemical vapor
deposition method using plasma as a promoting condition.
[0108] Revolution of platen: 120 rpm
[0109] Revolution of polishing head: 36 rpm
[0110] Polishing pressured:
[0111] Retainer ring pressure=7.5 psi
[0112] Pressure of zone 1=6.0 psi
[0113] Pressure of zone 2=3.0 psi
[0114] Pressure of zone 3=3.5 psi
[0115] Supply rate of aqueous dispersion: 300 ml/min
[0116] Polishing time: 60 seconds
[0117] Aqueous dispersion for chemical mechanical polishing:
[0118] CMS1101 (of JSR Corporation)
[0119] The thickness of the PETEOS film before and after chemical
mechanical polishing was measured at 33 points equally apart from
one another in the diameter direction of the 12-inch wafer having a
PETEOS film excluding 5 mm areas from the both ends as the object
to be polished. The polishing rate and the in-plane uniformity were
calculated from the measurement results based on the following
equation.
Amount of polishing=thickness before polishing-thickness after
polishing
Polishing rate=.SIGMA.(amount of polishing)/polishing time In-plane
uniformity (standard deviation of amount of polishing.div.average
amount of polishing).times.100(%)
[0120] The results are shown in Table 1. It can be said that
in-plane uniformity is satisfactory when the in-plane uniformity is
3% or less.
Example 2
[0121] A molded product having an average thickness of 2.5 mm, a
thickness distribution of 20 .mu.m, an arithmetic mean roughness
(Ra) of 3.4 .mu.m, a 10-point height (Rz) of 108 .mu.m, a core
roughness depth (Rk) of 18 .mu.m and a reduced peak height (Rpk) of
16 .mu.m was obtained in the same manner as in Example 1 except
that 80 vol % of 1,2-polybutadiene, 20 vol % of .beta.-cyclodextrin
and 0.8 part by mass (equivalent to 0.32 part by mass in terms of
pure dicumyl peroxide) of Percumyl D40 based on 100 parts by mass
of 1,2-polybutadiene were used.
[0122] Concentric grooves having a width of 0.5 mm, a pitch of 2
mm, a depth of 1.0 mm and a surface roughness of the inner wall of
5 .mu.m were formed in the sanded surface of the molded product in
the same manner as in Example 1 to manufacture a chemical
mechanical polishing pad.
[0123] Evaluations were made by using this chemical mechanical
polishing pad in the same manner as in Example 1. The results are
shown in Table 1.
Example 3
[0124] A molded product having an average thickness of 2.5 mm, a
thickness distribution of 25 .mu.m, an arithmetic mean roughness
(Ra) of 3.8 .mu.m, a 10-point height (Rz) of 115 .mu.m, a core
roughness depth (Rk) of 15 .mu.m and a reduced peak height (Rpk) of
14 .mu.m was obtained in the same manner as in Example 1 except
that 64 vol % of 1,2-polybutadiene, 16 vol % of a styrene-butadiene
block copolymer (TR2827 of JSR Corporation) and 20 vol % of
.beta.-cyclodextrin were used.
[0125] Concentric grooves having a width of 0.5 mm, a pitch of 2
mm, a depth of 1.0 mm and a surface roughness of the inner wall of
4.5 .mu.m were formed in the sanded surface of the molded product
in the same manner as in Example 1 to manufacture a chemical
mechanical polishing pad.
[0126] Evaluations were made by using this chemical mechanical
polishing pad in the same manner as in Example 1. The results are
shown in Table 1.
Comparative Example 1
[0127] A molded product having an average thickness of 2.5 mm, a
thickness distribution of 70 .mu.m, an arithmetic mean roughness
(Ra) of 1.5 am, a 10-point height (Rz) of 25 .mu.m, a core
roughness depth (Rk) of 8 .mu.m and a reduced peak height (Rpk) of
6 .mu.m was obtained in the same manner as in Example 1 except that
a mold having an average thickness of 2.5 mm was used to obtain a
molded product and the molded product was not sanded.
[0128] Concentric grooves having a width of 0.5 mm, a pitch of 2
mm, a depth of 1.0 mm and a surface roughness of the inner wall of
5.5 .mu.m were formed in the polishing surface of the molded
product in the same manner as in Example 1 to manufacture a
chemical mechanical polishing pad.
[0129] Evaluations were made by using this chemical mechanical
polishing pad in the same manner as in Example 1. The results are
shown in Table 1.
1 TABLE 1 Polishing rate in-plane uniformity (.ANG./min) (%)
Example 1 2850 1.0 Example 2 2700 2.0 Example 3 2750 1.5
Comparative 2800 8.0 Example 1
Example 4
[0130] The chemical mechanical polishing of a 12-inch wafer having
a PETEOS film was carried out in the same manner as in Example 1
except that break-in dressing was not carried out. Subsequently,
chemical mechanical polishing was made continuously on 10 12-inch
wafers having a PETEOS film. The polishing rate of each wafer is
shown in Table 2.
Comparative Example 2
[0131] Chemical mechanical polishing was made on 10 wafers in the
same manner as in Example 4 except that the chemical mechanical
polishing pad manufactured in the same manner as in Comparative
Example 1 was used. The polishing rate of each wafer is shown in
Table 2.
2TABLE 2 Polishing rate Polishing (.ANG./min) order of Comparative
wafers Example 4 Example 2 1 2830 1830 2 2850 1850 3 2870 1910 4
2820 2100 5 2840 2510 6 2850 2840 7 2880 2860 8 2870 2870 9 2850
2840 10 2840 2830
* * * * *