U.S. patent application number 13/978000 was filed with the patent office on 2014-06-19 for polishing pad.
This patent application is currently assigned to TORAY INDUSTRIES, INC.. The applicant listed for this patent is Seiji Fukuda, Shigetaka Kasai, Ryoji Okuda, Nana Takeuchi. Invention is credited to Seiji Fukuda, Shigetaka Kasai, Ryoji Okuda, Nana Takeuchi.
Application Number | 20140170943 13/978000 |
Document ID | / |
Family ID | 46672427 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140170943 |
Kind Code |
A1 |
Takeuchi; Nana ; et
al. |
June 19, 2014 |
POLISHING PAD
Abstract
A polishing pad comprising at least a polishing layer and a
cushion layer, wherein a groove is formed on a polishing surface of
the polishing pad, at least one of angles formed by the polishing
surface and a side surface of the groove which continues to the
polishing surface is 105-150.degree. inclusive, and the cushion
layer has a strain constant of 7.3.times.10.sup.-6 to
4.4.times.10.sup.-4 .mu.m/Pa inclusive. The use of the polishing
pad can achieve a purpose of preventing the fluctuation in a
polishing rate while keeping the polishing rate at a high
level.
Inventors: |
Takeuchi; Nana; (Otsu-shi,
JP) ; Fukuda; Seiji; (Otsu-shi, JP) ; Okuda;
Ryoji; (Otsu-shi, JP) ; Kasai; Shigetaka;
(Urayasu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Takeuchi; Nana
Fukuda; Seiji
Okuda; Ryoji
Kasai; Shigetaka |
Otsu-shi
Otsu-shi
Otsu-shi
Urayasu-shi |
|
JP
JP
JP
JP |
|
|
Assignee: |
TORAY INDUSTRIES, INC.
Tokyo
JP
|
Family ID: |
46672427 |
Appl. No.: |
13/978000 |
Filed: |
February 8, 2012 |
PCT Filed: |
February 8, 2012 |
PCT NO: |
PCT/JP2012/052843 |
371 Date: |
July 2, 2013 |
Current U.S.
Class: |
451/527 |
Current CPC
Class: |
B24B 37/26 20130101;
B24B 37/22 20130101 |
Class at
Publication: |
451/527 |
International
Class: |
B24B 37/26 20060101
B24B037/26 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2011 |
JP |
2011-029393 |
Claims
1. A polishing pad comprising at least a polishing layer and a
cushion layer, wherein a groove is formed on a polishing surface of
the polishing pad, at least one of angles formed by the polishing
surface and a side surface of the groove which continues to the
polishing surface is 105.degree. or more and 150.degree. or less,
and the cushion layer has a strain constant of at least
7.3.times.10.sup.-6 .mu.m/Pa and at most 4.4.times.10.sup.-4
.mu.m/Pa.
2. The polishing pad according to claim 1, wherein the cushion
layer has a strain constant of at most 3.0.times.10.sup.-4
.mu.m/Pa.
3. The polishing pad according to claim 1, wherein the cushion
layer has a strain constant of at most 1.5.times.10.sup.-4
.mu.m/Pa.
4. The polishing pad according to claim 1, wherein a pattern of the
groove of the polishing surface is grid-shaped.
5. The polishing pad according to claim 2, wherein a pattern of the
groove of the polishing surface is grid-shaped.
6. The polishing pad according to claim 3, wherein a pattern of the
groove of the polishing surface is grid-shaped.
Description
TECHNICAL FIELD
[0001] The present invention relates to a polishing pad. More
particularly, the present invention relates to a polishing pad
which is preferably used for forming a flat surface in a
semiconductor, a dielectric-metal composite and an integrated
circuit.
BACKGROUND ART
[0002] With increases in the density of semiconductor device,
technologies of multilayer wiring and the formation of an
interlayer insulation film associated therewith or the formation of
electrodes such as plug or damascene become more important. In
association with this, the importance of a process of planarizing
these interlayer insulation films and metal layers of electrodes
increases, and as an efficient technology for the planarization
process, a polishing technology referred to as CMP (Chemical
Mechanical Polishing) has been widespread.
[0003] In general, a chemical mechanical polishing apparatus is
composed of a polishing head for holding a semiconductor wafer of a
material to be processed, a polishing pad for carrying out
polishing of the material to be processed, and a polishing platen
holding the polishing pad. The polishing of the semiconductor wafer
is a process of using a slurry, and causing relative movement
between the semiconductor wafer and the polishing pad to remove a
projected portion on the surface layer of the semiconductor wafer
to planarize the surface layer of the wafer.
[0004] In polishing characteristics of CMP, there are various
required characteristics typified by securement of local flatness
and global flatness of a wafer, prevention of scratches, or
securement of a high polishing rate. Hence, in order to achieve
these characteristics, various contrivances were made concerning a
configuration of a groove (a pattern of a groove and a
cross-sectional shape of a groove) of the polishing pad, which is
one of large factors among factors affecting polishing
characteristics.
[0005] For example, a pattern of the groove formed on the polishing
layer surface is concentric, and by employing an approximately
rectangular shape as a cross-sectional shape of the groove, the
flatness of a wafer or the polishing rate is improved (for example,
Patent Document 1).
[0006] However, a corner portion in a cross-sectional shape of the
groove, or burrs formed at the corner portion resulting from
dressing performed before or after polishing or during polishing
may cause scratches on the surface of the wafer. It is described to
dispose an inclined surface at a boundary part between the
polishing surface and the groove in order to solve this problem
(for example, Patent Documents 2, 3).
PRIOR ART DOCUMENTS
Patent Documents
[0007] Patent Document 1: Japanese Patent Laid-open Publication No.
2002-144219
[0008] Patent Document 2: Japanese Patent Laid-open Publication No.
2004-186392
[0009] Patent Document 3: Japanese Patent Laid-open Publication No.
2010-45306
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0010] Here, the present inventors found that by providing an
inclined surface at a boundary portion between the polishing
surface and the groove, not only the scratches are decreased, but
also an attractive force works between the wafer and the polishing
pad to increase the polishing rate at a specific inclination angle.
However, we also found that this may cause an increase in the
fluctuation in a polishing rate too.
[0011] In view of such problems of the prior art, it is an object
of the present invention to provide a polishing pad which can
particularly suppress the fluctuation in a polishing rate while
maintaining a high polishing rate among polishing
characteristics.
Solutions to the Problems
[0012] The present inventors thought that an irregular attractive
force causes the fluctuation in a polishing rate, and it can be
solved by combining a cushion layer with a substance having
rigidity.
[0013] Hence, the present invention employs the following means in
order to solve the above-mentioned problems. That is, the present
invention pertains to a polishing pad comprising at least a
polishing layer and a cushion layer, wherein a groove is formed on
a polishing surface of the polishing pad, angles formed by the
polishing surface and a side surface of the groove which continues
to the polishing surface is 105.degree. or more and 150.degree. or
less, and the cushion layer has a strain constant of at least
7.3.times.10.sup.-6 .mu.m/Pa and at most 4.4.times.10.sup.-4
.mu.m/Pa.
Effects of the Invention
[0014] In accordance with the present invention, it is possible to
provide a polishing pad which can suppress the fluctuation in a
polishing rate while maintaining a high polishing rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows an example of a top surface configuration of a
groove formed on a polishing pad of the present invention.
[0016] FIG. 2 shows an example of a cross-sectional surface
configuration of the groove formed on the polishing pad of the
present invention.
[0017] FIG. 3 shows an example of a cross-sectional surface
configuration of the groove formed on the polishing pad of the
present invention.
[0018] FIG. 4 shows an example of a cross-sectional surface
configuration of the groove formed on the polishing pad of the
present invention.
[0019] FIG. 5 shows an example of a cross-sectional surface
configuration of the groove formed on the polishing pad of the
present invention.
[0020] FIG. 6 shows an example of a cross-sectional surface
configuration of the groove formed on the polishing pad of the
present invention.
EMBODIMENTS OF THE INVENTION
[0021] The present invention is completed by finding out, as a
result of the earnest investigations concerning a polishing pad
capable of suppressing the fluctuation in a polishing rate while
maintaining a high polishing rate, that the problem can be solved
at once by a polishing pad comprising at least a polishing layer
and a cushion layer, wherein a groove is formed on a polishing
surface of the polishing pad, angles formed by the polishing
surface and a side surface of the groove which continues to the
polishing surface is 105.degree. or more and 150.degree. or less,
and the cushion layer has a strain constant of at least
7.3.times.10.sup.-6 .mu.m/Pa and at most 4.4.times.10.sup.-4
.mu.m/Pa.
[0022] In the present invention, it is important that the polishing
pad has at least a polishing layer and a cushion layer. When the
polishing pad does not have the cushion layer, since strain due to
water absorption of the polishing layer cannot be cushioned, a
polishing rate and in-plane uniformity of a material to be polished
are fluctuated unstably. In the present invention, the strain
constant of the cushion layer is in the range of at least
7.3.times.10.sup.-6 .mu.m/Pa and at most 4.4.times.10.sup.-4
.mu.m/Pa. When the strain constant of the cushion layer falls
within this range, the fluctuation in a polishing rate can be
significantly suppressed while maintaining the effect of improving
a polishing rate by the groove having an inclination. From the
viewpoint of the fluctuation in a polishing rate and local flatness
of the material to be polished, an upper limit of the strain
constant is more preferably 3.0.times.10.sup.-4 .mu.m/Pa or less,
and moreover preferably 1.5.times.10.sup.-4 .mu.m/Pa or less. A
lower limit of the strain constant is more preferably
1.0.times.10.sup.-5 .mu.m/Pa or more, and moreover preferably
1.2.times.10.sup.-5 .mu.m/Pa or more. When the fluctuation in a
polishing rate is large, a polished amount of the material to be
polished is fluctuated, and consequently a thickness of a remaining
layer of the material to be polished is fluctuated to adversely
affect semiconductor device performance. Accordingly, the
fluctuation in a polishing rate is preferably 40.0 nm/min or less,
and more preferably 20.0 nm/min or less.
[0023] In addition, the strain constant in the present invention
was determined by a method in which using an indenter having a tip
of 5 mm in diameter, a thickness at the time of applying a pressure
of 27 kPa for 60 seconds with a dial gage is taken as (T1) .mu.m,
and subsequently a thickness at the time of applying a pressure of
177 kPa for 60 seconds is taken as (T2) .mu.m, and the strain
constant is calculated according to the following equation:
Strain constant (.mu.m/Pa)=(T1-T2)/(177-27)/1000.
[0024] Examples of materials of such the cushion layer include
nonfoamed elastomers such as natural rubbers, nitrile rubbers,
"neoprene (registered trademark)" rubbers, polybutadiene rubbers,
thermosetting polyurethane rubbers, thermoplastic polyurethane
rubbers, silicone rubbers and "Hytrel (registered trademark)";
polyolefin foams such as "TORAYPEF (registered trademark, PEF
produced by Toray Industries, Inc.)"; and nonwoven fabrics such as
"suba 400" produced by Nitta Haas Incorporated, but the material is
not limited to these materials.
[0025] The strain constant of the cushion layer can be adjusted
according to a material of the cushion layer. For example, when the
cushion layer is a foamed body, if a degree of foaming is
increased, the strain constant tends to increase because of
tendency to be soft. Further, when the cushion layer is nonfoamed,
it is possible to adjust hardness by adjusting a degree of
crosslinking within the cushion layer.
[0026] A thickness of the cushion layer is preferably in a range of
0.1 to 2 mm. The thickness is preferably 0.25 mm or more, and more
preferably 0.3 mm or more from the viewpoint of in-plane uniformity
of the entire surface of a semiconductor substrate. The thickness
is preferably 2 mm or less, and more preferably 1 mm or less from
the viewpoint of local flatness.
[0027] The surface of the polishing layer of the polishing pad in
the present invention has grooves. The configuration of the groove
viewed from the surface of the polishing layer includes grid-like,
concentric circle-like, spiral, and radial grooves, but the
configuration is not limited to these. Since the groove of an open
system in which the groove extends in a radial direction can renew
the slurry more effectively, a radial groove or a grid-like groove
is the most preferable. An example of the grid-like groove is shown
in FIG. 1. The grid-like groove 2 is formed on a polishing pad 1.
The pitch or the width of the groove is not particularly limited,
and the shape of a section divided by the grid-like groove may be
square or rectangular.
[0028] Further, at least one of angles (hereinafter, sometimes
referred to as "an inclination angle") formed by the polishing
surface and a side surface of the groove which continues to the
polishing surface is 105.degree. or more and 150.degree. or less,
and thereby, it is possible to suppress the fluctuation in a
polishing rate while maintaining a high polishing rate. A lower
limit of the angle is preferably 115.degree. or more from the
viewpoint of the retention and fluidity of the slurry. Further, an
upper limit of the angle is preferably 140.degree. or less, more
preferably 135.degree. or less, and particularly preferably
130.degree. or less. Since the slurry can be substantially supplied
stably to the inclined surface by improving the retention and
fluidity of the slurry, the fluctuation in a polishing rate can be
suppressed. Since the slurry is flown by a centrifugal force, it is
more effective that the inclination is provided at a side surface
located at least on a circumference side of opposed side surfaces
which form the groove. When one of the inclination angles of the
groove is in the above range, the other inclination angle is also
not particularly limited, but, similarly, is preferably 105.degree.
or more and 150.degree. or less. At this time, the lower limit of
the angle is more preferably 115.degree. or more. The upper limit
of the angle is more preferably 140.degree. or less, moreover
preferably 135.degree. or less, and particularly preferably
130.degree. or less. A groove configuration in which both
inclination angles are approximately the same is a more preferable
aspect. However, both inclination angles do not have to be
approximately the same. A shape of a groove bottom is not
particularly limited, and a cross-sectional shape may be V-shaped,
U-shaped or trapezoidal.
[0029] A specific configuration of the groove in the present
invention described above will be described by way of drawings.
FIG. 2 to FIG. 6 are partial sectional views obtained by enlarging
a groove 14 portion of a polishing pad having a polishing layer 10
on a cushion layer 20. The polishing layer 10 has a polishing
surface 11 and a side surface 12 which continues to the polishing
surface 11. The angle .alpha. is the above-mentioned inclination
angles, and at least one of the angles is 105.degree. or more and
150.degree. or less. A shape (cross-sectional shape) of a groove
bottom 13 is V-shaped in FIG. 2, U-shaped in FIG. 3, and
trapezoidal in FIG. 4, but the shape is not limited to these shapes
as described above. Further, in FIG. 2 to FIG. 4, inclination
angles .alpha. on both sides are approximately the same, and this
is a more preferable embodiment, but the present invention is not
limited to this embodiment. For example, in FIG. 5, the inclination
angles .alpha. on both sides are different, and any embodiment may
be employed. In addition, as shown in FIG. 6, when a boundary
between the polishing surface and the side surface of the groove
which continues to the polishing surface is in the form of a curved
line, the respective surfaces are linearly extended, and the angle
of intersection at the intersection of the two extended straight
lines is taken as an inclination angle.
[0030] As the polishing layer composing the polishing pad, a
polishing layer having a structure including independent air
bubbles is preferred since the polishing layer forms a flat surface
in a semiconductor, a dielectric-metal composite and an integrated
circuit. The hardness of the polishing layer is preferably 45 to 65
degrees in terms of measurement by an ASKER D hardness tester. When
the ASKER D hardness is less than 45 degrees, planarity of the
material to be polished is deteriorated, and when the ASKER D
hardness is more than 65 degrees, the planarity is good, but
uniformity of the material to be polished tends to decrease.
[0031] The material forming the polishing layer having the
above-mentioned structure is not particularly limited, and examples
thereof include polyethylene, polypropylene, polyester,
polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal,
polycarbonate, polymethyl methacrylate, polytetrafluoroethylene,
epoxy resins, ABS resin, AS resins, phenol resins, melamine resins,
"neoprene (registered trademark)" rubbers, butadiene rubbers,
styrene-butadiene rubbers, ethylene-propylene rubbers, silicone
rubbers, fluorine-containing rubbers and resins predominantly
composed of these materials. These materials may be used in
combination of two or more thereof. In these resins, a material
predominantly composed of polyurethane is more preferred in that a
diameter of an independent air bubble can be relatively easily
controlled.
[0032] The polyurethane is a polymer synthesized by a polyaddition
reaction or a polymerization reaction of polyisocyanate. A compound
used as a reference of polyisocyanate is a compound containing
activated hydrogen, that is, a compound containing two or more
polyhydroxy groups or amino groups. Examples of the polyisocyanate
include, but not limited to, tolylene diisocyanate, diphenylmethane
diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate,
and isophorone diisocyanate. These compounds may be used in
combination of two or more thereof.
[0033] As the compound containing polyhydroxy groups, polyols are
typical, and examples thereof include polyether polyol,
polyteramethylene ether glycol, epoxy resin-modified polyol,
polyester polyol, acrylic polyol, polybutadiene polyol, and
silicone polyol. These polyols may be used in combination of two or
more thereof. It is preferred to determine a combination of
polyisocyanate and polyol, and a combination or an optimum amount
of these compounds, a catalyst, a foaming agent and a foam
stabilizer according to the hardness, the bubble diameter and the
expansion ratio.
[0034] As a method of forming independent air bubbles in these
polyurethanes, a chemical foaming process in which various foaming
agents are mixed in a resin at the time of producing polyurethane
is common, but a method of foaming a resin by mechanical stirring
and then curing the resin can also be preferably used.
[0035] An average bubble diameter of the independent air bubbles is
preferably 30 .mu.m or more from the viewpoint of reducing
scratches. On the other hand, the average bubble diameter of the
independent air bubbles is preferably 150 .mu.m or less, more
preferably 140 .mu.m or less, and moreover preferably 130 .mu.m or
less from the viewpoint of the flatness of local projection and
depression of the material to be polished. In addition, the average
bubble diameter can be obtained by observing a sample cross-section
at a magnification of 400 times with an ultra-deep shape measuring
microscope VK-8500 manufactured by KEYENCE Corporation, selecting
images of circle bubbles excluding bubbles which are positioned at
an end of a field of view and lacks partially among bubbles
observed in one field of view, and processing the selected images
of circle bubbles with an image processing apparatus to determine
circle equivalent diameters from the cross-sectional areas of the
bubbles to calculate a number average value.
[0036] A preferable embodiment of the polishing pad in the present
invention is a pad containing a polymer of a vinyl compound and
polyurethane and having independent air bubbles. The polymer of a
vinyl compound alone can enhance the toughness and the hardness of
the pad, but hardly attain a homogeneous polishing pad having
independent air bubbles, and polyurethane becomes brittle when the
hardness is increased. By impregnating polyurethane with a vinyl
compound, a polishing pad including independent air bubbles and
having high toughness and high hardness can be formed.
[0037] The vinyl compound is a compound having a polymerizable
carbon-carbon double bond. Specific examples of the vinyl compound
include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl
methacrylate, isodecyl methacrylate, n-lauryl methacrylate,
2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate,
diethylaminoethyl methacrylate, glycidyl methacrylate, ethylene
glycol dimethacrylate, acrylic acid, methacrylic acid, fumaric
acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate,
maleic acid, dimethyl maleate, diethyl maleate, dipropyl maleate,
phenyl maleimide, cyclohexyl maleimide, isopropyl maleimide,
acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride,
styrene, .alpha.-methyl styrene, divinyl benzene, ethylene glycol
dimethacrylate, diethylene glycol dimethacrylate and the like.
These vinyl compounds may be used in combination of two or more
thereof.
[0038] Among the above-mentioned vinyl compounds,
CH.sub.2.dbd.CR.sup.1COOR.sup.2 (R.sup.1: methyl group or ethyl
group, R.sup.2: methyl group, ethyl group, propyl group or butyl
group) is preferred. Among these, methyl methacrylate, ethyl
methacrylate, n-butyl methacrylate and isobutyl methacrylate are
preferred in that the formation of independent air bubbles in
polyurethane is easy, the ability to be impregnated with a monomer
is good, polymerization/curing is easy, and the hardness of a
polymer of a vinyl compound polymerized/cured and a foam structure
containing polyurethane is high and planarization characteristics
are good.
[0039] Examples of polymerization initiators to be preferably used
for obtaining these polymers of a vinyl compound include radical
initiators such as azobisisobutyronitrile,
azobis(2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile,
benzoylperoxide, lauroyl peroxide, and isopropylperoxy dicarbonate.
These initiators may be used in combination of two or more thereof.
Further, an oxidation-reduction based polymerization initiator, for
example, a combination of peroxide and amines can also be used.
[0040] Examples of a method of impregnating polyurethane with the
vinyl compound include a method of immersing polyurethane in a
container containing a vinyl compound. In addition, in such a case,
it is also preferred to perform a treatment such as heating,
pressurizing, depressurizing, stirring, shaking, and ultrasonic
vibration for the purpose of increasing an impregnating speed.
[0041] An amount of the vinyl compound with which polyurethane is
impregnated has to be decided depending on the type of the vinyl
compound and polyurethane resin to be used or the characteristics
of the polishing pad to be manufactured, and the content ratio of
the polymer obtained from a vinyl compound and polyurethane in a
foamed structure polymerized/cured is preferably 30/70 to 80/20 by
weight, although one cannot speak generally. When the content ratio
of the polymer obtained from a vinyl compound is 30/70 or more, the
hardness of the polishing pad can be adequately high. When the
content ratio is less than 80/20, the elasticity of the polishing
layer can be adequately high.
[0042] In addition, the contents of the polymer obtained from a
vinyl compound polymerized/cured in polyurethane and polyurethane
can be measured by a technique of pyrolysis gas
chromatography/pyrolysis mass spectrometry. An apparatus which can
be used in this technique includes a double shot pyrolyzer
"PY-2010D" (manufactured by Frontier Laboratories Ltd.) as a
pyrolysis apparatus, and includes "TRIO-1" (manufactured by VG
SCIENTA Co., Ltd.) as a gas chromatograph/mass spectrometer.
[0043] In the present invention, it is preferred that a phase of
the polymer obtained from a vinyl compound is not separated from a
phase of polyurethane, and contained in a phase of polyurethane
from the viewpoint of the flatness of local projection and
depression of the semiconductor substrate. Quantitatively
describing, the spectra obtained by observing the polishing pad
with a micro-infrared spectroscope with a spot size of 50 .mu.m has
an infrared absorption peak of the polymer polymerized from a vinyl
compound and an infrared absorption peak of polyurethane, and
infrared spectra of various locations are substantially the same.
The micro-infrared spectroscope used herein includes IR.mu.s
manufactured by SPECTRA-TECH Inc.
[0044] The polishing pad may contain various types of additives
such as a polishing agent, an antistatic agent, a lubricant, a
stabilizer and a dye for the purpose of improving
characteristics.
[0045] In the present invention, the density of the polishing layer
is preferably 0.3 g/cm.sup.3 or more, more preferably 0.6
g/cm.sup.3 or more, and moreover preferably 0.65 g/cm.sup.3 or more
from the viewpoint of reducing defective local flatness or global
difference in height. On the other hand, from the viewpoint of
reducing scratches, the density of the polishing layer is
preferably 1.1 g/cm.sup.3 or less, more preferably 0.9 g/cm.sup.3
or less, and moreover preferably 0.85 g/cm.sup.3 or less. In
addition, the density of the polishing layer in the present
invention was measured by using a Harvard type picnometer (JIS
R-3503) and using water as a medium.
[0046] Examples of the material to be polished in the present
invention include an insulating layer formed on the semiconductor
wafer or the surface of a metal-wiring. Examples of the insulating
layer include an interlayer insulation film of the metal-wiring, a
lower insulating layer of the metal-wiring, and a shallow trench
isolation to be used for isolating elements. Examples of a material
of the metal-wiring include aluminum, tungsten, copper and alloys
thereof, and a structure of the metal-wiring includes damascene,
dual damascene and plug. When copper is used as the metal-wiring, a
barrier metal such as silicon nitride is also an object of
polishing. The main stream of the insulating layer is currently
silicon oxide, and a low dielectric insulating layer is also used.
The polishing pad of the present invention can also be used for
polishing a magnetic head, a hard disc, sapphire, SiC, and MEMS
(micro electro mechanical system) other than the semiconductor
wafer.
[0047] The polishing method of the present invention is suitably
used for forming a flat surface on the glass, the semiconductor,
the dielectric/metal composite, and the integrated circuit.
EXAMPLES
[0048] Hereinafter, the present invention will be described in more
detail by way of examples. However, the present examples are not to
be construed to limit the invention. In addition, measurement was
performed as follows.
<Measurement of Bubble Diameter>
[0049] As the average bubble diameter, a number average value was
used, which was obtained by observing a sample cross-section at a
magnification of 400 times with an ultra-deep shape measuring
microscope VK-8500 manufactured by KEYENCE Corporation, selecting
images of circle bubbles excluding bubbles which were positioned at
an end of a field of view and lacked partially among bubbles
observed in one field of view, and processing the selected images
of circle bubbles with an image processing apparatus to determine
circle equivalent diameters from the cross-sectional areas of the
bubbles to calculate an average value.
<Measurement of Hardness>
[0050] Hardness was measured according to JIS K 6253 (1997). The
prepared polyurethane resin was cut out into a size of 2 cm.times.2
cm (thickness: arbitrary) and left standing for 16 hours as a
sample for hardness measurement under environments of temperature
of 23.degree. C..+-.2.degree. C. and humidity of 50%.+-.5%. When
being measured, the samples were overlaid to keep a thickness of 6
mm or more. The hardness was measured by use of a hardness tester
(manufactured by KOBUNSHI KEIKI CO., LTD., ASKER D type hardness
tester).
<Measurement of Microrubber a Hardness>
[0051] The cushion layer was cut out into a size of 3 cm.times.3 cm
and left standing for 16 hours as a sample for hardness measurement
under environments of temperature of 23.degree. C..+-.2.degree. C.
and humidity of 50%.+-.5%. Microrubber A hardness was measured at
different three points in a sample by use of a microrubber hardness
tester MD-1 manufactured by KOBUNSHI KEIKI CO., LTD., and a
calculated average value was taken as a microrubber A hardness.
<Measurement of Inclination Angle>
[0052] A pad in which grooves were formed on the polishing layer
surface was placed so that a razor's blade was arranged to be
perpendicular to a direction of the groove, and sliced in a
direction of a groove depth, and a cross-section of the groove was
observed with an ultra-deep shape measuring microscope VK-8500
manufactured by KEYENCE Corporation to measure an angle formed by
the polishing surface and the side surface of the groove which
continues to the polishing surface. Two grooves which were the
closest to the position distance of a third of radius and the
position distance of two-thirds of radius from a center of the pad
were measured, and an average of these two grooves was taken as an
inclination angle.
<Determination of Strain Constant>
[0053] Using an indenter having a tip of 5 mm in diameter, a
thickness at the time of applying a pressure of 27 kPa for 60
seconds with a dial gauge was taken as (T1) .mu.m, and subsequently
a thickness at the time of applying a pressure of 177 kPa for 60
seconds was taken as (T2) .mu.m, and the strain constant was
calculated according to the following equation:
Strain constant (.mu.m/Pa)=(T1-T2)/(177-27)/1000.
<Average Polishing Rate>
[0054] Using MIRRA 3400 manufactured by Applied Materials, Inc.,
polishing was carried out under predetermined polishing conditions
while detecting an end point. Polishing characteristics were
measured in a direction of a diameter excluding an outermost 1
mm-circumference of an 8-inch wafer. Polishing characteristics were
measured at 37 points which were located for every 5 mm within a
radius of 90 mm from a center in the plane and 18 points which were
located for every 1 mm outside a radius of 91 mm from a center in
the plane to determine an average polishing rate (nm/min).
<Determination of Fluctuation in Polishing Rate>
[0055] Five hundred of wafers were polished, an average polishing
rate of each wafer was measured, and the fluctuation in a polishing
rate was calculated according to the following equation:
Fluctuation in polishing rate (n,/min)=(Maximum average polishing
rate of wafer)-(Minimum average polishing rate of wafer).
Example 1
[0056] In a molding machine RIM, 30 parts by weight of
polypropylene glycol, 40 parts by weight of diphenylmethane
diisocyanate, 0.5 part by weight of water, 0.3 part by weight of
triethylamine, 1.7 parts by weight of a silicone foam stabilizer,
and 0.09 part by weight of tin octylate were mixed, and the
resulting mixture was discharged to a die and molded by pressure
molding to prepare a foamed polyurethane sheet including
independent air bubbles.
[0057] The foamed polyurethane sheet was immersed for 60 minutes in
methyl methacrylate containing 0.2 part by weight of
azobisisobutyronitrile. Then, the foamed polyurethane sheet was
immersed in a solution composed of 15 parts by weight of polyvinyl
alcohol "CP" (polymerization degree: about 500, produced by NACALAI
TESQUE, INC.), 35 parts by weight of ethyl alcohol (reagent special
grade, produced by KATAYAMA CHEMICAL INDUSTRIES Co., Ltd.) and 50
parts by weight of water, and dried to coat the surface layer of
the foamed polyurethane sheet with polyvinyl alcohol.
[0058] Next, the foamed polyurethane sheet was sandwiched between
two glass sheets with a vinyl chloride gasket interposed between
the sheet and the glass sheet and heated at 65.degree. C. for 6
hours and at 120.degree. C. for 3 hours, and thereby, the sheet was
polymerized/cured. The polymerized sheet was released from between
glass sheets and washed with water, and then vacuum-dried at
50.degree. C. A hard foamed sheet thus obtained was sliced into a
thickness of 2.00 mm, and both surfaces were ground to prepare a
polishing layer. The content of methyl methacrylate in the
polishing layer was 66% by weight. The polishing layer had the D
hardness of 54 degrees and the density of 0.81 g/cm.sup.3, and an
average bubble diameter of the independent air bubbles was 45
.mu.m.
[0059] Thermoplastic polyurethane (cushion layer thickness: 0.3 mm)
having a strain constant of 0.15.times.10.sup.-4 .mu.m/Pa
(microrubber A hardness 89 degrees) produced by Nihon Matai Co.,
Ltd. as a cushion layer was laminated on the polishing layer
obtained by the above method with an adhesive layer MA-6203
produced by Mitsui Chemicals Polyurethanes, Inc. therebetween by
using a roll coater, and further a double-faced tape 5604 TDM
manufactured by SEKISUI CHEMICAL CO., LTD. was bonded to a backside
as a backside tape. This laminate was punched out into a circle
with a diameter of 508 mm, and grooves having an inclination angle
of 123 degrees and a depth of 1.5 mm were formed on the surface of
the polishing layer at a groove pitch of 15 mm in the form of XY
lattice to prepare a polishing pad.
[0060] The polishing pad obtained by the above method was attached
to a platen of a polishing machine ("MIRRA 3400" manufactured by
Applied Materials, Inc.). Five-hundred pieces of 8-inch wafers of
oxide film were polished under the conditions in which a retainer
ring pressure=41 kPa (6 psi), an inner tube pressure=28 kPa (4
psi), a membrane pressure=28 kPa (4 psi), a platen rotational
speed=76 rpm, a polishing head rotational speed=75 rpm, and a
diluted slurry formed by diluting slurry (SS-25 manufactured by
Cabot Corporation) with an equal volumetric amount of pure water
was flown at a flow rate of 150 ml/min, and in-situ dressing was
carried out for 30 seconds after the start of polishing at a load
of 17.6 N (4 lbf) and at a polishing time of 1 minute by using a
dresser manufactured by Saesol CHEMICAL CO., LTD. The average
polishing rate of the five hundredth of the oxide film was 216.6
nm/min. The fluctuation in a polishing rate of 500 oxide films was
as good as 10.5 nm/min.
Example 2
[0061] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 110.degree.. An average
polishing rate was 185.0 nm/min, and the fluctuation in a polishing
rate was as good as 25.4 nm/min.
Example 3
[0062] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 140.degree.. An average
polishing rate was 227.3 nm/min, and the fluctuation in a polishing
rate was as good as 23.8 nm/min.
Example 4
[0063] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the cushion layer to a polyolefin
foam (TORAYPEF produced by Toray Industries, Inc., expansion ratio
3 times, cushion layer thickness: 1.0 mm) having a strain constant
of 2.6.times.10.sup.-4 .mu.m/Pa (microrubber A hardness)
65.degree.. An average polishing rate was 193.0 nm/min, and the
fluctuation in a polishing rate was as good as 31.0 nm/min.
Example 5
[0064] A wafer of an oxide film was polished in the same manner as
in Example 1 except for forming twenty of grooves which were
arranged radially and equally spaced on the polishing layer
surface. An average polishing rate was 191.4 nm/min, and the
fluctuation in a polishing rate was as good as 24.3 nm/min.
Example 6
[0065] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the pitch and the inclination
angle of the groove on the polishing layer surface to 11.5 mm and
135.degree., respectively. An average polishing rate was 225.0
nm/min, and the fluctuation in a polishing rate was as good as 12.6
nm/min.
Example 7
[0066] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 135.degree.. An average
polishing rate was 223.2 nm/min, and the fluctuation in a polishing
rate was as good as 18.7 nm/min.
Example 8
[0067] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the cushion layer to a polyolefin
foam (TORAYPEF produced by Toray Industries, Inc., expansion ratio
4 times, cushion layer thickness: 1.0 mm) having a strain constant
of 3.8.times.10.sup.-4 .mu.m/Pa (microrubber A hardness)
57.degree.. An average polishing rate was 192.1 nm/min, and the
fluctuation in a polishing rate was as good as 36.4 nm/min.
Example 9
[0068] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 135.degree. and changing
the cushion layer to a polyolefin foam (TORAYPEF produced by Toray
Industries, Inc., expansion ratio 3 times, cushion layer thickness:
1.0 mm) having a strain constant of 2.6.times.10.sup.-4 .mu.m/Pa
(microrubber A hardness 65.degree.). An average polishing rate was
201.3 nm/min, and the fluctuation in a polishing rate was as good
as 33.1 nm/min.
Example 10
[0069] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 135.degree. and changing
the cushion layer to a polyolefin foam (TORAYPEF produced by Toray
Industries, Inc., expansion ratio 4 times, cushion layer thickness:
1.0 mm) having a strain constant of 3.8.times.10.sup.-4 .mu.m/Pa
(microrubber A hardness 57.degree.). An average polishing rate was
208.4 nm/min, and the fluctuation in a polishing rate was as good
as 38.2 nm/min.
Example 11
[0070] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing two inclination angles facing each
other across the groove on the polishing layer surface to
135.degree. and 130.degree., respectively. An average polishing
rate was 220.9 nm/min, and the fluctuation in a polishing rate was
as good as 19.0 nm/min.
Example 12
[0071] A polyester film having a thickness of 188 .mu.m was bonded
to a backside of a polishing layer with an adhesive sandwiched, and
a cushion layer was bonded to the polyester film surface. A wafer
of an oxide film was polished in the same manner as in Example 1
except for changing the inclination angle of the groove on the
polishing layer surface to 135.degree.. An average polishing rate
was 233.3 nm/min, and the fluctuation in a polishing rate was as
good as 21.8 nm/min.
Comparative Example 1
[0072] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 90.degree.. An average
polishing rate was 182.1 nm/min, and the fluctuation in a polishing
rate was as large as 107.7 nm/min.
Comparative Example 2
[0073] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the cushion layer to suba 400
produced by Nitta Haas Incorporated (cushion layer thickness: 1.25
mm) having a strain constant of 6.5.times.10.sup.-4 .mu.m/Pa
(microrubber A hardness 51.degree.) and changing the inclination
angle of the groove on the polishing layer surface to 135.degree..
An average polishing rate was 234.3 nm/min, and the fluctuation in
a polishing rate was as large as 184.7 nm/min.
Comparative Example 3
[0074] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the cushion layer to NIPPARON EXT
produced by NHK SPRING CO., LTD. (cushion layer thickness: 0.8 mm)
having a strain constant of 5.2.times.10.sup.-4 .mu.m/Pa
(microrubber A hardness 59.degree.) and changing the inclination
angle of the groove on the polishing layer surface to 135.degree..
An average polishing rate was 221.8 nm/min, and the fluctuation in
a polishing rate was as large as 165.5 nm/min.
Comparative Example 4
[0075] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the inclination angle of the
groove on the polishing layer surface to 155.degree.. An average
polishing rate was 215.5 nm/min, and the fluctuation in a polishing
rate was as large as 63.2 nm/min.
Comparative Example 5
[0076] A wafer of an oxide film was polished in the same manner as
in Example 1 except for changing the cushion layer to suba 400
produced by Nitta Haas Incorporated, (cushion layer thickness: 1.25
mm) having a strain constant of 6.5.times.10.sup.-4 .mu.m/Pa
(microrubber A hardness 51.degree.). An average polishing rate was
226.1 nm/min, and the fluctuation in a polishing rate was as large
as 173.0 nm/min.
[0077] The results of Examples and Comparative Examples are
summarized in Table 1.
TABLE-US-00001 TABLE 1 Fluctuation Strain Pol- in Incli- Constant
.times. ishing Polishing nation 10.sup.-4 Microrubber Rate Rate
Angle .mu.m/Pa A Hardness nm/min nm/min Example 1 123 0.15 89 216.6
10.5 Example 2 110 0.15 89 185.0 25.4 Example 3 140 0.15 89 227.3
23.8 Example 4 123 2.6 65 193.0 31.0 Example 5 123 0.15 89 191.4
24.3 Example 6 135 0.15 89 225.0 12.6 Example 7 135 0.15 89 223.2
18.7 Example 8 123 3.8 57 192.1 36.4 Example 9 135 2.6 65 201.3
33.1 Example 10 135 3.8 57 208.4 38.2 Example 11 135/130 0.15 89
220.9 19.0 Example 12 135 0.15 89 233.3 21.8 Comparative 90 0.15 89
182.1 107.7 Example 1 Comparative 135 6.5 51 234.3 184.7 Example 2
Comparative 135 5.2 59 221.8 165.5 Example 3 Comparative 155 0.15
89 215.5 63.2 Example 4 Comparative 125 6.5 51 226.1 173.0 Example
5
DESCRIPTION OF REFERENCE SIGNS
[0078] 1 polishing pad [0079] 2 grid-like groove [0080] 10
polishing layer [0081] 11 polishing layer [0082] 12 side surface
[0083] 13 groove bottom [0084] 14 groove [0085] 20 cushion
layer
* * * * *