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 µm, a 10-point height (Rz) of 40 to 150 µm, a core
roughness depth (Rk) of 12 to 50 µm and a reduced peak height (Rpk) of 7 to 40 µm.
[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:
molding a polishing layer; and
sanding at least the surface to be polishing surface of the polishing layer.
[0011] 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
[0012]
Fig. 1 is a diagram showing the definition of 10-point height (Rz);
Fig. 2 is a diagram showing the definition of a material ratio curve;
Fig. 3 is a diagram showing the definition of core roughness depth (Rk); and
Fig. 4 is a diagram showing the definition of reduced peak height (Rpk).
Detailed Description of the Preferred Embodiment
[0013] The polishing surface of the chemical mechanical polishing pad of the present invention
has an arithmetic mean roughness (Ra) of 0.1 to 15 µm, a 10-point height (Rz) of 40
to 150 µm, a core roughness depth (Rk) of 12 to 50 µm and a reduced peak height (Rpk)
of 7 to 40 µm.
[0014] 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.
[0015] 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).
[0016] 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).
[0017] 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.
[0018] 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).
[0019] 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).
[0020] 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).
[0021] 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.
[0022] 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.
[0023] 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.
[0024] The above roughness profile can be measured by using a commercially available surface
roughness meter.
[0025] 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 µm. This value
is preferably 0.1 to 12 µm. The 10-point height (Rz) is 40 to 150 µm. It is preferably
40 to 130 µm. The core roughness depth (Rk) is 12 to 50 µm. It is preferably 12 to
45 µm. The reduced peak height (Rpk) is 7 to 40 µm. It is preferably 7 to 30 µm.
[0026] 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.
[0027] The chemical mechanical polishing pad of the present invention preferably has a thickness
distribution of 50 µm or less. The effect of the present invention is advantageously
exhibited by setting the thickness distribution of the chemical mechanical polishing
pad to 50 µm or less. This value is more preferably 40 µm or less, particularly preferably
30 µm 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.
[0028] 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.
[0029] 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.
[0030] 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).
[0031] 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).
[0032] 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.
[0033] 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.
[0034] 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 groove(s) or recessed portion(s) is not particularly
limited. It may be, for example, rectangular, trapezoidal, U-shaped or V-shaped.
[0035] The number of the grooves or the recessed portions may be one or more.
[0036] 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.
[0037] The surface roughness of the inner wall of the above groove (s) or recessed portion(s)
is preferably 20 µm or less, more preferably 15 µm 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.
[0038] 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.
[0039] 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).
[0040] 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.
[0041] 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.
[0042] 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
2.0mm, specifically 0.1 to 1.5 mm, more specifically 0.1 to 1.0 mm regardless of its/their
shape.
[0043] The number of the grooves or recessed portions may one or more.
[0044] The chemical mechanical polishing pad of the present invention has a thickness distribution
of 50 µm 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.
(1) the step of preparing a composition for a chemical mechanical polishing pad;
(2) the step of molding the above composition for a chemical mechanical polishing
pad into a polishing layer; and
(3) the step of sanding at least the polishing surface of the above polishing layer.
[0045] A detailed description is subsequently given of each of the above steps.
(1) step of preparing a composition for a chemical mechanical polishing pad
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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-α-olefin rubbers such as ethylene-propylene rubber and ethylene-propylene-diene
rubber, other rubbers such as butyl rubber, silicone rubber and fluorine rubber.
[0051] 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.
[0052] 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.
[0053] These organic materials may be used alone or in combination of two or more.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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° 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°C in accordance with the "vulcanized rubber tensile test method"
specified in JIS K 6251. The test is carried out at 80° C because heat is generated
by slide contact at the time of actual polishing.
[0058] 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.
[0059] 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.
[0060] 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 saccharldes
(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.
[0061] The water-soluble particles have an average particle diameter of preferably 0.1 to
500 µm, more preferably 0.5 to 100 µm. The pores are as big as preferably 0.1 to 500
µm, more preferably 0.5 to 100 µm. When the average particle diameter of the water-soluble
particles is smaller than 0. 1 µm, 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 µm, the formed pores become too big, whereby the mechanical strength and
polishing rate of the obtained chemical mechanical polishing pad may lower.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] The average size of the cavities dispersed in the water-insoluble matrix material
is preferably 0.1 to 500 µm, more preferably 0.5 to 100 µm.
[0067] 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.
[0068] 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).
[0069] 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.
(2) step of molding a polishing layer from the composition for a chemical mechanical
polishing pad
[0070] 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 µm or less easily.
[0071] 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.
(3) step of sanding at least the polishing surface of the above polishing layer
[0072] Thereafter, at least the polishing surface of the thus formed polishing layer is
sanded.
[0073] 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.
[0074] The size of the abrasive grains used for the above sanding step is preferably 20
to 200 µm, more preferably 25 to 150 µm. The grit size of the sandpaper is preferably
80 to 600, more preferably 120 to 400.
[0075] Sandpaper having a larger width than the polishing surface of the above polishing
layer is preferably used for sanding.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] A chemical mechanical polishing pad having a thickness distribution of 50 µm or less
and a polishing surface with an arithmetic mean roughness (Ra) of 0.1 to 15 µm, a
10-point height (Rz) of 40 to 150 µm, a core roughness depth (Rk) of 12 to 50 µm and
a reduced peak height (Rpk) of 7 to 40 µm can be easily obtained by carrying out this
sanding.
[0081] A description is subsequently given of the chemical mechanical polishing method of
the present invention.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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
[0087] 98 vol% of 1,2-polybutadiene (JSR RB830 of JSR Corporation) and 2 vol% of β-cyclodextrin
(Dexy Pearl β-100 of Bio Research Corporation of Yokohama) as a water-soluble substance
were kneaded together by an extruder heated at 155°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°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 µm, an arithmetic mean roughness (Ra) of 4.4 µm, a 10-point height (Rz) of 125
µm, a core roughness depth (Rk) of 16 µm and a reduced peak height (Rpk) of 14 µm
was obtained.
[0088] 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.
[0089] 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).
[0090] 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.
[0091] 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 µm.
[0092] 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.
Revolution of platen: 120 rpm
Supply rate of deionized water: 100 ml/min
Polishing time: 600 seconds
[0093] 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.
Revolution of platen: 120 rpm
Revolution of polishing head: 36 rpm
Polishing pressure:
Retainer ring pressure = 7.5 psi
Pressure of zone 1 = 6.0 psi
Pressure of zone 2 = 3.0 psi
Pressure of zone 3 = 3.5 psi
Supply rate of aqueous dispersion: 300 ml/min
Polishing time: 60 seconds
Aqueous dispersion for chemical mechanical polishing: CMS1101 (of JSR Corporation)
[0094] 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
[0095] 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
[0096] A molded product having an average thickness of 2.5 mm, a thickness distribution
of 20 µm, an arithmetic mean roughness (Ra) of 3.4 µm, a 10-point height (Rz) of 108
µm, a core roughness depth (Rk) of 18 µm and a reduced peak height (Rpk) of 16 µm
was obtained in the same manner as in Example 1 except that 80 vol% of 1,2-polybutadlene,
20 vol% of β-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.
[0097] 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 µm 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.
[0098] 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
[0099] A molded product having an average thickness of 2.5 mm, a thickness distribution
of 25 µm, an arithmetic mean roughness (Ra) of 3.8 µm, a 10-point height (Rz) of 115
µm, a core roughness depth (Rk) of 15 µmand a reduced peak height (Rpk) of 14 µm 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 β-cyclodextrin were used.
[0100] 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 µm 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.
[0101] 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
[0102] A molded product having an average thickness of 2.5 mm, a thickness distribution
of 70 µm, an arithmetic mean roughness (Ra) of 1.5 µm, a 10-point height (Rz) of 25
µm, a core roughness depth (Rk) of 8 µm and a reduced peak height (Rpk) of 6 µm 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.
[0103] 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 µm 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.
[0104] 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.
Table 1
|
Polishing rate (Å/min) |
in-plane uniformity (%) |
Example 1 |
2850 |
1.0 |
Example 2 |
2700 |
2.0 |
Example 3 |
2750 |
1.5 |
Comparative Example 1 |
2800 |
8.0 |
Example 4
[0105] 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
[0106] 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.
Table 2
Polishing order of wafers |
Polishing rate (Å/min) |
|
Example 4 |
Comparative 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 |
[0107] A chemical mechanical polishing pad having a polishing surface with an arithmetic
mean roughness (Ra) of 0.1 to 15 µm, a 10-point height, (Rz) of 40 to 150 µm, a core
roughness depth (Rk) of 12 to 50 µm and a reduced peak height (Rpk) of 7 to 40 µm,
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.