U.S. patent application number 12/309624 was filed with the patent office on 2009-12-31 for chemical mechanical polishing pads comprising liquid organic material encapsulated in polymer shell and methods for producing the same.
Invention is credited to Seung-Hun Bae, Sung-Min Jun, Ju-Yeol Lee, Jong-Soo Lim, In-Ha Park.
Application Number | 20090320379 12/309624 |
Document ID | / |
Family ID | 38981665 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090320379 |
Kind Code |
A1 |
Jun; Sung-Min ; et
al. |
December 31, 2009 |
Chemical Mechanical Polishing Pads Comprising Liquid Organic
Material Encapsulated in Polymer Shell and Methods For Producing
The Same
Abstract
There is provided a chemical mechanical polishing (CMP) pad
including a core of a polymer shell encapsulating a liquid organic
material having one of a boiling point and a decomposition point of
130.degree. C. or more in a polymer matrix, the CMP pad having open
pores formed by the core on a polishing surface thereof, and a
method of producing the CMP pad. The CMP pad having a high hardness
and a high density improves polishing efficiency and flatness of a
wafer and maintains a uniform size of the core, thereby producing
pads having high polishing efficiency and stable polishing
performance.
Inventors: |
Jun; Sung-Min;
(Choongcheongbook-do, KR) ; Lim; Jong-Soo;
(Daejeon, KR) ; Bae; Seung-Hun; (Seoul, KR)
; Lee; Ju-Yeol; (Gyeonggi-do, KR) ; Park;
In-Ha; (Ulsan, KR) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Family ID: |
38981665 |
Appl. No.: |
12/309624 |
Filed: |
July 20, 2007 |
PCT Filed: |
July 20, 2007 |
PCT NO: |
PCT/KR2007/003513 |
371 Date: |
January 21, 2009 |
Current U.S.
Class: |
51/298 |
Current CPC
Class: |
B24D 3/32 20130101; B24B
37/24 20130101 |
Class at
Publication: |
51/298 |
International
Class: |
B24D 3/00 20060101
B24D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2006 |
KR |
10-2006-0069164 |
Claims
1. A chemical mechanical polishing (CMP) pad comprising a core of a
polymer shell encapsulating a liquid organic material having a
boiling point and a decomposition point of 130.degree. C. or more
in a polymer matrix, the CMP pad having open pores formed by the
core on a polishing surface thereof, wherein the liquid organic
material is at least one member selected from the group consisting
of a hydrocarbon solvent and a modified hydrocarbon solvent formed
of a mixture of CnHm in which n is an integer from 9 to 16;
phthalate plasticizers; liquid oligomers with a molecular weight of
about 10,000 or less and a viscosity of about 5.times.10.sup.8
cps/20.degree. C. or less; solvents with a high boiling point such
as N,N-dimethylformamide (DMF); and the mixture thereof.
2. The CMP pad of claim 1, wherein the polymer shell has a density
of 0.5 to 1.5 g/cm.sup.3.
3. The CMP pad of claim 1, wherein the polymer shell is selected
from the group consisting of polystyrene-acrylate copolymer,
polyacrylonitrile, polyacrylate, polycarbonate, silicone, epoxy,
polyurethane, polyester, nylon, polyvinylchloride, polystyrene,
polypropylene, polyethylene, acrylic resin, and the mixture
thereof.
4. (canceled)
5. The CMP pad of claim 1, wherein the phthalate plasticizers are
selected from the group consisting of dioctyl phthalate, diisononyl
phthalate, dioctyl adipate, trioctyl trimellitate, dibutyl
phthalate, and diisodecyl phthalate.
6. The CMP pad of claim 1, wherein the liquid oligomers are
selected from the group consisting of polypropylene glycol,
polyethylene glycol, polymethylene glycol, ester polyol, carbonate
polyol, poly Hanstoff dispersion, and polyisocyanate
polyaddition.
7. The CMP pad of claim 1, wherein the polymer matrix is selected
from a the group consisting of polyurethane, polyester, nylon,
acryl, epoxy, silicone, polycarbonate, and a mixtures thereof.
8. The CMP pad of claim 1, wherein the core is contained in the
polymer matrix by 1 to 200 part per hundred resin (phr).
9. The CMP pad of claim 1, wherein the core has a size of 1 to 200
.mu.m.
10. The CMP pad of claim 1, wherein the pad has a hardness of 60
Shore D or greater.
11. A method of producing a CMP pad, the method comprising:
producing a polymer matrix by a two-liquid casting method using a
main material and a hardener; and mixing the polymer matrix with a
core of a polymer shell encapsulating a liquid organic material
having a boiling point and a decomposition point of 130.degree. C.
or greater, wherein the liquid organic material is at least one
member selected from the group consisting of a hydrocarbon solvent
and a modified hydrocarbon solvent formed of a mixture of CnHm in
which n is an integer from 9 to 16; phthalate plasticizers; liquid
oligomers with a molecular weight of about 10,000 or less and a
viscosity of about 5.times.10.sup.8 cps/20.degree. C. or less;
solvents with a high boiling point such as N,N-dimethylformamide
(DMF); and mixtures thereof.
12. The method of claim 11, wherein the core of the polymer shell
encapsulating the liquid organic material is mixed with at least
one of the main materials and the hardener.
13. The method of claim 11, wherein the core of the polymer shell
is contained in the polymer matrix by 1 to 200 phr.
14. The method of claim 11, wherein the polymer matrix is selected
from the group consisting of polyurethane, polyester, nylon, acryl,
epoxy, silicone, polycarbonate, and a mixtures thereof.
15. The method of claim 11, wherein the polymer shell has a density
of 0.5 to 1.5 g/cm.sup.3.
16. The method of claim 11, wherein the polymer shell is selected
from the group consisting of polystyrene-acrylate copolymer,
polyacrylonitrile, polyacrylate, polycarbonate, silicone, epoxy,
polyurethane, polyester, nylon, polyvinylchloride, polystyrene,
polypropylene, polyethylene, acrylic resin, and a mixtures
thereof.
17. The method of claim 11, wherein the phthalate plasticizer is
selected from the group consisting of dioctyl phthalate, diisononyl
phthalate, dioctyl adipate, trioctyl trimellitate, dibutyl
phthalate, and diisodecyl phthalate.
18. The method of claim 11, wherein the liquid oligomers are
selected from the group consisting of polypropylene glycol,
polyethylene glycol, polymethylene glycol, ester polyol, carbonate
polyol, poly hanstoff dispersion, and polyisocyanate polyaddition.
Description
TECHNICAL FIELD
[0001] The present invention relates to a chemical mechanical
polishing (CMP) pad, and more particularly, to a CMP pad formed of
a polymer matrix containing a liquid organic material encapsulated
in a polymer shell and a method of producing the same.
BACKGROUND ART
[0002] Generally, a polishing process includes abrading a rough
surface to form a flat surface such as glass. While repetitively
and regularly polishing a surface of an object with a polishing
pad, a fine-grain slurry existing in an interface between the
polishing pad and the object allows the object to be polished.
Particularly, in a process of manufacturing a semiconductor, since
planarization of a wafer has a great effect on semiconductor
integration, a chemical mechanical polishing (CMP) process has to
be performed for wafer planarization.
[0003] There are three conventional methods in technology with
respect to polishing pads used in a CMP process.
[0004] One is a urethane pad filled with one of natural felt such
as wool, natural weaved fiber, felt polyester mixed with urethane,
and all kinds of fillers. Another is a polishing pad including
bubbles or pores capable of storing slurry without a filler. The
other is a polishing pad using a uniform polymer matrix with micro
holes capable of storing slurry.
[0005] With respect to the urethane pad, U.S. Pat. No. 4,927,432
discloses a polishing pad formed of polyester felt mixed with
urethane to use pores and projected fibers. Though the pad
described above shows excellent flatness, since the pad has low
hardness, a polishing speed is low.
[0006] With respect to the another pad, U.S. Pat. No. 5,578,362
discloses a polishing pad with a surface structure of a sunken
portion in a semicircular shape formed by mixing polyurethane with
a hollow spherical subsidiary. Such pads have been generally used
due to excellent polishing speed and flatness. However, when mixing
with the different subsidiary, uniform distribution is difficult
due to low density of the subsidiary, which makes it difficult to
uniformly prepare a pad with a regular density deviation. Also, as
polishing progresses, an error of flatness increases. Due to the
hollow shape, it is difficult to prepare a pad with a high hardness
to improve polishing efficiency.
[0007] U.S. Pat. No. 6,685,540 discloses a polishing pad using
solid-phase polymer as a filler. However, there is no site for
collecting slurry in the pad, thereby deteriorating polishing
efficiency.
[0008] Also, U.S. Pat. No. 6,790,883 discloses a polishing pad
formed by mixing water-soluble organic and inorganic materials with
a polymer matrix. An empty space of materials solved in water acts
as a pore capable of collecting slurry. However, there is needed a
time for generating a space for collecting slurry, thereby causing
deterioration of polishing efficiency. Also, a life of the pad is
short due to deterioration of property of matter, due to water
solubility of water-soluble materials.
[0009] Also, Korean Patent No. 0495404 discloses a polishing pad
including embedded liquid micro elements and a method of producing
the polishing pad. It is described that a process of producing the
polishing pad is easy since all elements used in the producing
process are liquid. However, it has been known that the embedded
liquid micro elements initially mixed with a urethane polymer
matrix do not have a certain size. Therefore, it is required to
control a size of a space for collecting slurry, which is formed by
the liquid micro elements, during a urethane reaction. Since it is
required to form uniform slurry collecting spaces within a short
urethane reaction time, liquid incompatible with urethane is
required and it is difficult to control the size of uniform slurry
collecting spaces with a small change in a producing process. Also,
since liquid incompatible with a polymer matrix is used, adhesive
strength is deteriorated due to a phenomenon in which liquid
material is transferred toward a surface of the pad. Also, a life
of the pad is short due to deterioration of properties of the
urethane matrix and hardness of the pad itself is reduced since
only liquid exists in the space. Therefore, it is difficult to
satisfy a requirement of wafer planarization in a semiconductor
process.
[0010] Also, Korean Patent Publication No. 2001-0005435 discloses
urethane moldings for a polishing pad, the urethane molding
prepared by mixing and hardening one of expanded micro hollow
spheres and micro globoids expandable without foam when applying
heat, and water with an isocynate group terminal prepolymer and
compounds containing active hydrogen. However, there is problem in
which bubbles generated by micro globoids and water are expanded or
foamed during a urethane reaction, thereby deforming bubbles to
weaken density and hardness thereof. Also, since gases are used as
slurry collecting spaces, hardness and density of the pad are not
increased.
[0011] U.S. Pat. No. 6,777,455 discloses a polishing pad of micro
urethane foam prepared by mixing inert gases. In this case, it is
difficult to increase hardness of a polishing pad itself prepared
by mixing inert gases, dishing and erosion may be caused due to low
hardness, in a CMP process, and it is difficult to improve flatness
of wafers.
[0012] In addition, there is a polishing pad of uniform urethane
without bubbles, the pad given a polishing function by using a
surface texture. However, the pad makes a scratch on a polished
surface of an object and has a low polishing speed due to
insufficient amount of slurry during a polishing process.
[0013] Up to now, polishing pads, whose elasticity and hardness are
given thereto by mixing, solidifying, and impregnating pores, a
filler, and nonwoven, the pads using a polyurethane polymer matrix
considering easiness of production, are generally used. Also, pads
including some of heterogeneous materials as described above,
pores, bubbles, and a different material capable of forming a
concave portion during a CMP process, in addition to a polyurethane
matrix, are commonly used in planarization process of several
semiconductor processes or glass.
[0014] However, when a polyurethane matrix includes pores or
bubbles, deviation of density increases due to heterogeneity of
distribution, thereby generating a difference in a polishing
function for each lot and a difference in density for each portion
in the same lot and a problem of an error in flatness, the error
increasing as the polishing process progresses.
[0015] Together with improvement of semiconductor processes, there
is required a polishing pad having excellent functions such as high
polishing efficiency, stable polishing function, flatness of
wafers, and convenience in producing pads.
[0016] To satisfy a level of requirements for high-integration and
planarization of semiconductors, which increases day by day, it is
necessary that polishing pads have a high hardness, high polishing
efficiency, and a stable polishing function. However, generally,
though polishing efficiency of pads is high, the polishing
efficiency is deteriorated as time goes by. Also, it is difficult
to stably prepare the pads with a high hardness and high density,
due to a low density of hollow subsidiary materials.
[0017] On the other hand, urethane polishing pads without bubbles,
with stable polishing function, are capable of having a high
hardness and high density and maintaining flatness of wafers.
However, polishing efficiency of the pads is relatively low.
DISCLOSURE OF INVENTION
Technical Problem
[0018] As described above, it is difficult that general polishing
pads satisfy the level of requirements for high integration and
high planarization of semiconductors, increased day by day.
[0019] Accordingly, an aspect of the present invention provides a
polishing pad with a high hardness, high density, high polishing
efficiency, and stable polishing function and a method of producing
the polishing pad, together with convenience of producing the
polishing pad.
Technical Solution
[0020] According to an aspect of the present invention, there is
provided a chemical mechanical polishing (CMP) pad including a core
of a polymer shell encapsulating a liquid organic material with one
of a boiling point and a decomposition point of 130.degree. C. or
more in a polymer matrix, the CMP pad having open pores formed by
the core on a polishing surface thereof.
[0021] The polymer shell may have a density of 0.5 to 1.5
g/cm.sup.3.
[0022] The polymer shell may be selected from a group consisting of
polystyrene-acrylate copolymer, polyacrylonitrile, polyacrylate,
polycarbonate, silicone, epoxy, polyurethane, polyester, nylon,
polyvinylchloride, polystyrene, polypropylene, polyethylene,
acrylic resin, and a mixture thereof.
[0023] The liquid organic material may be selected from a group
consisting of one of a hydrocarbon solvent and a modified
hydrocarbon solvent formed of a mixture of CnHm in which n is an
integer from 9 to 16; phthalate plasticizers; liquid oligomers with
a molecular weight about 10,000 or less and a viscosity about
5.times.10.sup.8 cps/20.degree. C. or less; solvents with a high
boiling point such as N,N-dimethylformamide (DMF); and a mixture
thereof.
[0024] The phthalate plasticizers may be selected from a group
consisting of dioctyl phthalate, diisononyl phthalate, dioctyl
adipate, trioctyl trimellitate, dibutyl phthalate, and diisodecyl
phthalate. The liquid oligomers may be selected from a group
consisting of polypropylene glycol, polyethylene glycol,
polymethylene glycol, ester polyol, carbonate polyol, poly hanstoff
dispersion, and polyisocyanate polyaddition.
[0025] The polymer matrix may be selected from a group consisting
of polyurethane, polyester, nylon, acryl, epoxy, silicone,
polycarbonate, and a mixture thereof.
[0026] The core may be contained in the polymer matrix by 1 to 200
part per hundred resin (phr).
[0027] The core may have a size of 1 to 200 .mu.m.
[0028] The pad may have a hardness of 60 Shore D or more.
[0029] According to another aspect of the present invention, there
is provided a method of producing a CMP pad, the method including:
producing a polymer matrix by a two-liquid casting method using a
main material and a hardener; and mixing the polymer matrix with a
core of a polymer shell encapsulating a liquid organic
material.
[0030] More preferably, the core of the polymer shell encapsulating
the liquid organic material may be mixed with at least one of the
main material and the hardener.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic diagram illustrating a polishing pad
according to an exemplary embodiment of the present invention;
and
[0032] FIG. 2 is a graph illustrating decreases in hardnesses of
polishing pads.
BEST MODE FOR CARRYING OUT THE INVENTION
[0033] Hereinafter, an exemplary embodiment of the present
invention will be described in detail referring to the attached
drawings.
[0034] FIG. 1 is a schematic diagram illustrating a chemical
mechanical polishing (CMP) pad formed of a polymer matrix 3
including a core in the form of a polymer shell 1 encapsulating a
liquid organic material 2.
[0035] In the present invention, a polymer matrix may be formed of
one of polyurethane, polyester, nylon, acryl, epoxy, silicone,
polycarbonates, and a mixture thereof. Particularly, the polymer
matrix may be formed of the polyurethane.
[0036] The polyurethane may be prepared by casting two liquids
formed of a main material and hardeners. When mixing the main
material with the hardeners, the core containing the liquid organic
material encapsulated in the polymer shell may be mixed with at
least one of the main material and the hardeners.
[0037] In the polymer matrix, the core in the form of the polymer
shell encapsulating the liquid organic material is contained,
thereby increasing a hardness of the polishing pad to more than 60
D and exposing and opening the core in the pad to continuously
provide a space for storing slurry as the pad is abraded, during a
polishing process.
[0038] It is impossible to obtain a polishing pad with a high
hardness and high density by using conventional hollow pores.
According to an exemplary embodiment of the present invention, a
polishing pad with a high hardness and high density by containing a
core encapsulating a liquid organic material may be obtained and a
uniform polishing pad may be prepared by mixing materials having a
similar density to each other. In addition, though after a large
amount of time is taken up with polishing processes, it may be
controlled that a bottom of the polishing pad prepared as described
above is softened by attacks of slurry and the hardness of the pad
itself is deteriorated as time goes by, thereby obtaining stable
polishing efficiency.
[0039] A polymer material with a similar density to the polymer
matrix, such as urethane may be used as the polymer shell to reduce
defects in mixture of the matrix and reduce a flatness deviation of
wafers. In detail, the density may be 0.5 to 1.5 g/cm.sup.3. Also,
as the polymer shell may be formed of the polymer shell is selected
from a group consisting of polystyrene-acrylate copolymer,
polyacrylonitrile, polyacrylate, polycarbonate, silicone, epoxy,
polyurethane, polyester, nylon, polyvinylchloride, polystyrene,
polypropylene, polyethylene, acrylic resin, and a mixture thereof.
Particularly, the polymer shell may be polyacrylate.
[0040] The liquid organic material may be selected from a group
consisting of one of a hydrocarbon solvent and a modified
hydrocarbon solvent, which is a mixture of C.sub.nH.sub.m in which
n is an integer from 9 to 16 such as CX-2100, CX-2500, and CX-2700
produced by Hosung Chemex Co., Ltd; phthalate plasticizers such as
dioctyl phthalate, diisononyl phthalate, dioctyl adipate, trioctyl
trimellitate, dibutyl phthalate, and diisodecyl phthalate; liquid
oligomers with a molecular weight about 10,000 or less and a
viscosity about 5.times.10.sup.8 cps/20.degree. C. or less and a
decomposition point of 130.degree. C. or more, which is a modified
polyol such as polypropylene glycol, polyethylene glycol,
polymethylene glycol, ester polyol, carbonate polyol, poly hanstoff
dispersion, and polyisocyanate polyaddition; solvents with a high
boiling point such as N,N-dimethylformamide (DMF); and a mixture
thereof.
[0041] Also, a boiling point or decomposition point may be more
than 130.degree. C., and more particularly, more than 160.degree.
C., which is not easily volatilized by polymerization heat of the
polymer matrix. When the boiling point of the liquid organic
material is lower than 130.degree. C., a polishing pad with a high
density and high hardness may not be obtained due to a deformation
of the core during a urethane reaction.
[0042] The core may be contained in the polymer matrix by 1 to 200
phr, and more particularly, 10 to 60 phr based on the polymer
matrix. When an amount of the core is less than 1 phr, polishing
characteristics such as a polishing speed and a level of flatness
are low. When the amount of the core is more than 200 phr, it is
difficult to stably prepare polishing pads and to obtain stable
polishing efficiency since uniform distribution of the core is
difficult.
[0043] A size of the core may be 1 to 200 .mu.m, and more
particularly, 10 to 70 .mu.m. When the size is less than 1 .mu.m,
the polishing characteristics such as a polishing speed and
flatness are not improved due to a small amount of polishing
slurry. When the size is more than 200 .mu.m, it is not suitable
for urethane moldings for polishing pads.
EXAMPLES
[0044] Hereinafter, the present invention will be described in
detail with reference to examples. However, the present invention
will not be limited to the examples.
Example 1
[0045] Poly(tetramethylene glycol) (PTMEG) (a functional group 2,
Mw=1000) of 1000 g were poured into a reaction vessel, and
methylenediphenyl diisocynate (MDI) of 1262 g were poured into the
reaction vessel. A prepolymer, a main material, with both terminals
formed of isocynates was prepared by stirring the two liquids for
three hours at a temperature of 80.degree. C. Hereto, 500 g of
MS-220D Dongjin Semichem Co., Ltd. that was a liquid organic
material encapsulated in a polymer shell was poured and mixed using
a high-speed mixer. MS-220D was a core formed of a polyacrylate
shell encapsulating a liquid organic material that was a mixed
solvent of hydrocarbon liquid organic materials C.sub.nH.sub.m in
which n is an integer from 9 to 16 with a boiling point of
160.degree. C. or more.
[0046] A hardener to be mixed with the main material was prepared
by pouring and heating 4,4'-methylene-bis(O-chloroaniline) of 1080
g into the vessel at a temperature of 130.degree. C. for three
hours and removing pores therefrom.
[0047] The main material was mixed with the hardener by using a
high-speed mixer by an equivalent of urethane reaction as 1:1 and
poured into an open circular mold of 25 inches to be hardened. A
urethane cake prepared as described above was left as it was at a
temperature of 80.degree. C. for 24 hours and was perfectly reacted
to be ripened.
[0048] In this case, the prepared polyurethane had a density of
1.105 g/cm.sup.3 and a hardness of 67 D by Shore D A mass of the
polyurethane was cut and sliced into a length of 20 inches. A
groove formed in an XY shape with a width of 400 .mu.m and a pitch
of 0.5 inches was formed on a surface of the polyurethane by using
a laser. A polishing pad was prepared by attaching a buffer pad to
a bottom of the polyurethane by using a double stick tape.
Example 2
[0049] A urethane cake was prepared by using a method similar to
that of Example 1, exclusive of an input amount of MS-220D. In this
case, the input amount was 1000 g.
Example 3
[0050] A urethane cake was prepared by using a method similar to
that of Example 1, exclusive of an input amount of MS-220D. In this
case, the input was 1500 g.
Example 4
[0051] A polishing pad was prepared by preparing a urethane cake by
using a method similar to that of Example 1 and simultaneously
forming a micro hole with a size of 180 .mu.m and a pitch of 300
.mu.m and a groove by using a laser on a surface thereof.
[0052] In this case, the polyurethane cake had a density of 1.1
g/cm.sup.3 and a hardness of 66 Shore D.
Comparative Example 1
[0053] A urethane cake was prepared by using a method similar to
that of Example 1, exclusive of a core of a polymer shell
encapsulating the liquid organic material.
[0054] In this case, the polyurethane cake had a density of 1.145
g/cm.sup.3 and a hardness of 68 D by Shore D. The polyurethane cake
was cut and sliced into a length of 20 inches. A micro hole with a
size of 180 .mu.m and a pitch of 300 .mu.m was formed on a surface
of the polyurethane by using a laser. After that, a polishing pad
was prepared by attaching a buffer pad to a bottom of the
polyurethane by using a double-stick tape.
Comparative Example 2
[0055] A mixture was prepared by mixing 500 weight percent of
polyether prepolymers formed of Uniroyal ADIPENE.TM. L-325 and an
isocynate group having a concentration of 2.2 meg/g with 13 g of
EXPANCEL 551DE that was a micro shell formed of a copolymer of
chloride vinylidene and acrylonitrile, decompressing to remove
pores therefrom, and adding 145 g of
4,4'-methylene-bis(0-chloroaniline) previously melted at a
temperature of 120.degree. C. thereto while stirring. The mixture
was stirred for about 1 minute, put into an open circular mold, and
ripened in an oven at a temperature of 100.degree. C. for six
hours, thereby obtaining a polyurethane micro foam block with a
cell diameter of 40 .mu.m. The obtained polyurethane micro foam
block had a density of 0.75 g/cm.sup.3. A groove was formed by
using a laser.
[0056] Performances of polishing pads prepared by Examples 1 to 4
and Comparative Examples 1 and 2, respectively, were tested. As
conditions applied to a chemical-mechanical polishing (CMP) process
of the prepared pads, AVANTI-472 (IPEC Co., Ltd.) was used as a CMP
machine, silica slurry (Cheil Industries, Starplanar-4000) was used
as slurry, an amount of flow was 200 ml/minute, a polishing load
was 7 psi, the polishing pad rotated 46 times per minute, and a
wafer rotated 38 times per minute. Under the conditions as
described above, uniformity in wafer, an average of polishing
speed, and a number of scratches were measured. A result of the
measurement is shown in Table 1.
[0057] Average Polishing Speed
[0058] The average of polishing speed was tested by polishing a
silicone wafer of 8 inches, the wafer coated with a thermal oxide
layer of 1 .mu.m (10,000 .ANG.), under the described polishing
conditions for one minutes.
[0059] Uniformity in Wafer
[0060] The uniformity in wafer was obtained by measuring a
thickness of a layer at 98 locations in wafer after polishing a
silicone wafer of 8 inches, the wafer coated with a thermal oxide
layer of 1 .mu.m (10,000 .ANG.), under the described polishing
conditions for one minutes. The uniformity in wafer was obtained by
an equation as follows.
Uniformity in wafer(%)=(maximum thickness-minimum
thickness)/2.times.average layer thickness.times.100 Equation
[0061] Number of Scratches
[0062] The number of scratches was obtained by measuring a number
of micro scratches formed on one wafer by using KLA (TENCOR Co.,
Ltd. KLA2112) after polishing a silicone wafer of 8 inches, the
wafer coated with a thermal oxide layer of 1 .mu.m (10,000 .ANG.),
under the described polishing conditions for one minutes, and
cleaning and drying the wafer. As a number of the scratches is
smaller, the polishing pad has more excellent performance. A number
of the scratches, which can be commercially available, may be less
than 500.
TABLE-US-00001 TABLE 1 Hardness Density Additives Uniformity
Average Polishing Number of Scratches (Shore D) (g/cm.sup.3)
Contents (phr) in Wafer (%) Speed (.ANG./min) (Number per Wafer)
Example 1 67 D 1.105 15 3.5% or less 2500 130 Example 2 66 D 1.00
30 3.5% or less 2600 120 Example 3 65 D 0.95 45 3.5% or less 2700
80 Example 4 66 D 1.10 30 4.0% or less 2555 100 Comp. Example 1 68
D 1.145 0 4.5% or less 2450 130 Comp. Example 2 54 D 0.75 -- 5.0%
or less 2550 190
[0063] As shown in Table 1, the polishing pads obtained by Examples
1 to 4 have a high hardness and high density than those of
Comparative Example 2 and have more excellent values than those of
Comparative Examples 1 and 2 in the average polishing speed, the
uniformity in wafer, and the number of scratches. In the case of a
drop of hardness for each content, though mixing with 45 phr, which
is a large amount, the polishing pads of the present invention have
a high density of 0.95 g/cm.sup.3 and a hardness of 65 D far higher
than 54 D of Comparative Example 2 containing pores and just a
little lower than 68 D of Comparative Example 1 used as a hard pad
having a high hardness. Also, in the case of the polishing speed,
the number of scratches, and the uniformity in wafer, the polishing
pads of the present invention have relatively higher than those of
Comparative Examples 1 and 2 and show stable numerical values.
Example 5
[0064] A urethane cake was prepared by using a method similar to
that of Example 1 by mixing with the core formed of a liquid
organic material encapsulated in a polymer shell.
[0065] In this case, the MS-220D was added and mixed by a volume
ratio of 5%, 10%, 20%, 30%, and 40% of a volume of a polymer
matrix, thereby preparing five polishing pads. A hardness of each
of the polishing pads was measured. A result of the measurement is
shown in FIG. 2.
Comparative Example 3
[0066] A urethane cake was prepared by using a method similar to
that of Comparative Example 2 by using EXPANCEL 551DE that was a
micro shell formed of a copolymer of chloride vinylidene and
acrylonitrile instead of the liquid organic core encapsulated in a
polymer shell.
[0067] In this case, five polishing pads were prepared by adding
and mixing with contents of the EXPANCEL 551DE by volume ratios of
5%, 10%, 20%, 30%, and 40% of a volume of a polymer matrix,
respectively. A hardness of each of the polishing pads was
measured. A result of the measurement is shown in FIG. 2.
Comparative Example 4
[0068] A urethane cake was prepared by using a method similar to
Example 5 by using soybean oil instead of the liquid organic core
encapsulated in a polymer shell.
[0069] In this case, five polishing pads were prepared by adding
and mixing with contents of the soybean oil by volume ratios of 5%,
10%, 20%, 30%, and 40% of a volume of a polymer matrix,
respectively. A hardness of each of the polishing pads was
measured. A result of the measurement is shown in FIG. 2.
Comparative Example 5
[0070] A urethane cake was prepared by using a method similar to
Example 5 by using cyclo-dextrin instead of the liquid organic core
encapsulated in a polymer shell.
[0071] In this case, five polishing pads were prepared by adding
and mixing with contents of the cyclo-dextrin by volume ratios of
5%, 10%, 20%, 30%, and 40% of a volume of a polymer matrix,
respectively. A hardness of each of the polishing pads was
measured. A result of the measurement is shown in FIG. 2.
[0072] FIG. 2 is a graph illustrating the results of measuring
hardness changes of the polishing pads prepared by Example 5 and
Comparative Examples 3 to 5. Referring to FIG. 2, it may be known
that there is little difference between the polishing pad prepared
by mixing with the core of the liquid organic material and the
conventional polishing pads. Therefore, it may be known that the
hardness of the polishing pad is maintained, thereby maintaining
polishing efficiency and flatness of wafer.
INDUSTRIAL APPLICABILITY
[0073] An aspect of the present invention provides a polishing pad
prepared by mixing a polymer matrix with a core in the form of a
liquid organic material encapsulated in a polymer shell to obtain
higher polishing efficiency, more stable polishing performance, and
flatness of wafer. Accordingly, the polishing pad may have a
hardness more than 60 D to improve the polishing efficiency and the
flatness of wafer, which may be of importance to integrate a
semiconductor process. Defects caused by hollow subsidiary
materials having a low density may be reduced by using the liquid
organic material encapsulated in the polymer shell having a density
similar to a urethane. In a urethane reaction at a temperature of
130.degree. C., a size of the core may be uniformly maintained,
thereby obtaining high polishing efficiency and stably producing
polishing pads.
* * * * *