U.S. patent application number 10/664951 was filed with the patent office on 2004-05-27 for polishing pad with window for planarization.
Invention is credited to Allison, William C., Swisher, Robert G., Wang, Alan E..
Application Number | 20040102141 10/664951 |
Document ID | / |
Family ID | 32043244 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040102141 |
Kind Code |
A1 |
Swisher, Robert G. ; et
al. |
May 27, 2004 |
Polishing pad with window for planarization
Abstract
The present invention relates to a polishing pad. In particular,
the polishing pad of the present invention can include a window.
The polishing pad of the present invention can be useful for
polishing articles and can be especially useful for chemical
mechanical polishing or planarization of a microelectronic device,
such as a semiconductor wafer. The window of the polishing pad is
at least partially transparent and thus, can be particularly useful
with polishing or planarizing tools that are equipped with
through-the-platen wafer metrology.
Inventors: |
Swisher, Robert G.;
(Pittsburgh, PA) ; Allison, William C.;
(Murrysville, PA) ; Wang, Alan E.; (Gibsonia,
PA) |
Correspondence
Address: |
PPG Industries, Inc.
Law-Intellectual Property 39S
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
32043244 |
Appl. No.: |
10/664951 |
Filed: |
September 22, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60413367 |
Sep 25, 2002 |
|
|
|
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24B 37/205
20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 007/22 |
Claims
In the claims:
1. A polishing pad comprising: a. a first layer having an opening;
and b. a second layer wherein at least a portion of said second
layer comprises an at least partially transparent window, and
wherein said first layer is at least partially connected to said
second layer, and wherein said first layer absorbs at least two
percent by weight of polishing slurry based on total weight of said
first layer.
2. The polishing pad of claim 1 wherein said first layer absorbs
50% or less by weight of polishing slurry based on total weight of
said first layer.
3. The polishing pad of claim 1 wherein said first layer is
selected from particulate polymer and crosslinked polymer binder;
particulate polymer and an organic polymer binder; sintered
particles of thermoplastic resin; pressure sintered powder compacts
of thermoplastic polymer; polymeric matrices impregnated with a
plurality of polymeric microelements wherein each polymeric
microelement can have a void space therein, or combinations
thereof.
4. The polishing pad of claim 1 wherein said first layer has a
thickness of at least 0.020 inches.
5. The polishing pad of claim 4 wherein said first layer has a
thickness of 0.150 inches or less.
6. The polishing pad of claim 1 wherein said second layer is
selected from substantially non-volume compressible polymers and
metallic films and foils.
7. The polishing pad of claim 1 wherein said second layer is
selected from polyolefins; cellulose-based polymers; acrylics;
polyesters and co-polyesters; polycarbonate; polyamides; high
performance plastics; or mixtures thereof.
8. The polishing pad of claim 1 wherein said second layer is
selected from low density polyethylene, high density polyethylene
ultra-high molecular weight polyethylene or polypropylene;
cellulose acetate or cellulose butyrate; PET or PETG; nylon 6/6 or
nylon 6/12; polyetheretherketone, polyphenylene oxide, polysulfone,
polyimide, or polyetherimide; or mixtures thereof.
9. The polishing pad of claim 1 wherein said second layer has a
thickness of at least 0.0005 inches.
10. The polishing pad of claim 9 wherein said second layer has a
thickness of 0.0650 inches or less.
11. The polishing pad of claim 1 wherein said first and second
layers are at least partially connected by an adhesive
material.
12. The polishing pad of claim 11 wherein said adhesive material is
selected from contact adhesives, pressure sensitive adhesives,
structural adhesives, hot melt adhesives, thermoplastic adhesives,
and curable adhesives, thermosetting adhesives; and combinations
thereof.
13. The polishing pad of claim 1 wherein said opening in said first
layer is at least partially aligned with said window in said second
layer.
14. The polishing pad of claim 1 further comprising a third layer
at least partially connected to said second layer, said third layer
having an opening.
15. The polishing pad of claim 14 wherein said third layer is
selected from natural rubber, synthetic rubbers, thermoplastic
elastomer, foam sheet and combinations thereof.
16. The polishing pad of claim 14 wherein said third layer has a
thickness of at least 0.04 inches.
17. The polishing pad of claim 16 wherein said third layer has a
thickness of 0.100 inches or less.
18. The polishing pad of claim 14 wherein said first, second and
third layers are at least partially connected by an adhesive
material.
19. The polishing pad of claim 14 wherein said opening in said
first layer, said window in said second layer and said opening in
said third layer are at least partially aligned.
20. A polishing pad comprising: a. a first layer having an opening;
and b. a second layer wherein at least a portion of said second
layer comprises an at least partially transparent window, and
wherein said first layer is at least partially connected to said
second layer, and wherein said first layer has a porosity of at
least two percent by volume based on total volume of said first
layer.
21. The polishing pad of claim 20 wherein said first layer has a
porosity of 50% or less by volume based on total volume of said
first layer.
22. The polishing pad of claim 20 wherein said first layer is
selected from particulate polymer and crosslinked polymer binder;
particulate polymer and an organic polymer binder; sintered
particles of thermoplastic resin; pressure sintered powder compacts
of thermoplastic polymer; polymeric matrices impregnated with a
plurality of polymeric microelements wherein each polymeric
microelement can have a void space therein, or combinations
thereof.
23. The polishing pad of claim 20 wherein said first layer has a
thickness of at least 0.020 inches.
24. The polishing pad of claim 23 wherein said first layer has a
thickness of 0.150 inches or less.
25. The polishing pad of claim 20 wherein said second layer is
selected from substantially non-volume compressible polymers and
metallic films and foils.
26. The polishing pad of claim 20 wherein said second layer is
selected from polyolefins; cellulose-based polymers; acrylics;
polyesters and co-polyesters; polycarbonate; polyamides; high
performance plastics; or mixtures thereof.
27. The polishing pad of claim 1 wherein said second layer is
selected from low density polyethylene, high density polyethylene
ultra-high molecular weight polyethylene or polypropylene;
cellulose acetate or cellulose butyrate; PET or PETG; nylon 6/6 or
nylon 6/12; polyetheretherketone, polyphenylene oxide, polysulfone,
polyimide, or polyetherimide; or mixtures thereof.
28. The polishing pad of claim 20 wherein said second layer has a
thickness of at least 0.0005 inches.
29. The polishing pad of claim 28 wherein said second layer has a
thickness of 0.0650 inches or less.
30. The polishing pad of claim 20 wherein said first and second
layers are at least partially connected by an adhesive
material.
31. The polishing pad of claim 30 wherein said adhesive material is
selected from contact adhesives, pressure sensitive adhesives,
structural adhesives, hot melt adhesives, thermoplastic adhesives,
curable adhesives, thermosetting adhesives and combinations
thereof.
32. The polishing pad of claim 20 wherein said opening in said
first layer is at least partially aligned with said window in said
second layer.
33. The polishing pad of claim 20 further comprising a third layer
at least partially connected to said second layer, said third layer
having an opening.
34. The polishing pad of claim 33 wherein said third layer is
selected from natural rubber, synthetic rubbers, thermoplastic
elastomer, foam sheet and combinations thereof.
35. The polishing pad of claim 33 wherein said third layer has a
thickness of at least 0.04 inches.
36. The polishing pad of claim 35 wherein said third layer has a
thickness of 0.100 inches or less.
37. The polishing pad of claim 30 wherein said first, second and
third layers are at least partially connected by an adhesive
material.
38. The polishing pad of claim 30 wherein said opening in said
first layer, said window in said second layer and said opening in
said third layer are at least partially aligned.
39. A polishing pad comprising: a. a first layer having an opening;
and b. a second layer wherein at least a portion of said second
layer comprises an at least partially transparent window, and
wherein said first layer is at least partially connected to said
second layer, and wherein said first layer has a percent volume
compressibility greater than said second layer.
40. The polishing pad of claim 39 wherein said first layer has a
percent volume compressibility of at least 0.3% when a load of 20
psi is applied.
41. The polishing pad of claim 40 wherein said first layer has a
percent volume compressibility of 3% or less when a load of 20 psi
is applied.
42. The polishing pad of claim 39 wherein said second layer is
substantially non-volume compressible.
43. The polishing pad of claim 39 wherein said first layer is
selected from particulate polymer and crosslinked polymer binder;
particulate polymer and an organic polymer binder; sintered
particles of thermoplastic resin; pressure sintered powder compacts
of thermoplastic polymer; polymeric matrices impregnated with a
plurality of polymeric microelements wherein each polymeric
microelement can have a void space therein, or combinations
thereof.
44. The polishing pad of claim 39 wherein said second layer is
selected from substantially non-volume compressible polymers and
metallic films and foils.
45. The polishing pad of claim 39 wherein said second layer is
selected from polyolefins; cellulose-based polymers; acrylics;
polyesters and co-polyesters; polycarbonate; polyamides; high
performance plastics; or mixtures thereof.
46. The polishing pad of claim 39 wherein said second layer is
selected from low density polyethylene, high density polyethylene
ultra-high molecular weight polyethylene or polypropylene;
cellulose acetate or cellulose butyrate; PET or PETG; nylon 6/6 or
nylon 6/12; polyetheretherketone, polyphenylene oxide, polysulfone,
polyimide, or polyetherimide; or mixtures thereof.
47. The polishing pad of claim 39 wherein said first and second
layers are at least partially connected by an adhesive
material.
48. The polishing pad of claim 47 wherein said adhesive material is
selected from contact adhesives, pressure sensitive adhesives,
structural adhesives, hot melt adhesives, thermoplastic adhesives,
curable adhesives, thermosetting adhesives and combinations
thereof.
49. The polishing pad of claim 39 wherein said opening in said
first layer is at least partially aligned with said window in said
second layer.
50. The polishing pad of claim 39 further comprising a third layer
at least partially connected to said second layer, said third layer
having an opening.
51. The polishing pad of claim 50 wherein said third layer is
selected from natural rubber, synthetic rubbers, thermoplastic
elastomer, foam sheet and combinations thereof.
52. The polishing pad of claim 50 wherein said first, second and
third layers are at least partially connected by an adhesive
material.
53. The polishing pad of claim 50 wherein said opening in said
first layer, said window in said second layer and said opening in
said third layer are at least partially aligned.
54. The polishing pad of claim 39 wherein at least a portion of
said window comprises a coating.
55. The polishing pad of claim 54 wherein said coating comprises a
resin coating.
56. The polishing pad of claim 55 wherein said resin coating is
selected from thermoplastic acrylic resins, thermoset acrylic
resins, urethane systems, epoxy resins, polyester resins, or
mixtures thereof.
57. The polishing pad of claim 39 wherein said first layer
comprises grooves on a polishing surface.
58. The polishing pad of claim 39 wherein said first layer
comprises a pattern on a polishing surface.
59. A method of preparing a polishing pad comprising at least
partially connecting a first layer having an opening to a second
layer, wherein at least a portion of said second layer comprises an
at least partially transparent window, and wherein said first layer
absorbs at least two percent by weight of polishing slurry based on
total weight of said first layer.
60. The method of claim 59 further comprising at least partially
connecting a third layer having an opening to said second
layer.
61. The method of claim 59 wherein said first and second layers are
at least partially connected by an adhesive material.
62. A method of preparing a polishing pad comprising at least
partially connecting a first layer having an opening to a second
layer, wherein at least a portion of said second layer comprises an
at least partially transparent window, and wherein said first layer
has a porosity of at least two percent by volume based on total
volume of said first layer.
63. The method of claim 62 further comprising at least partially
connecting a third layer having an opening to said second
layer.
64. The method of claim 62 wherein said first and second layers are
at least partially connected by an adhesive material.
65. A method of preparing a polishing pad comprising at least
partially connecting a first layer having an opening to a second
layer, wherein at least a portion of said second layer comprises an
at least partially transparent window, and wherein first layer has
a percent volume compressibility greater than said second
layer.
66. The method of claim 65 further comprising at least partially
connecting a third layer having an opening to said second
layer.
67. The method of claim 65 wherein said first and second layers are
at least partially connected by an adhesive material.
68. A polishing pad comprising: a. a first layer having an opening;
b. a second layer wherein at least a portion of said second layer
comprises an at least partially transparent window; and c. a third
layer having an opening, wherein said first layer is at least
partially connected to said second layer and said second layer is
at least partially connected to said third layer, and wherein said
third layer is softer than said first layer.
Description
[0001] The present invention relates to a polishing pad. In
particular, the polishing pad of the present invention can include
a window. The polishing pad of the present invention can be useful
for polishing articles and can be especially useful for chemical
mechanical polishing or planarization of a microelectronic device,
such as a semiconductor wafer. The window of the polishing pad is
at least partially transparent and thus, can be particularly useful
with polishing or planarizing tools that are equipped with
through-the-platen wafer metrology.
[0002] In general, the polishing or planarization of a non-planar
surface of a microelectronic device to an essentially planar
surface involves rubbing the non-planar surface with the work
surface of a polishing pad using a controlled and repetitive
motion. A polishing slurry can be interposed between the rough
surface of the article that is to be polished and the work surface
of the polishing pad.
[0003] The fabrication of a microelectronic device such as a
semiconductor wafer generally involves the formation of a plurality
of integrated circuits on the wafer comprising, for example,
silicon or gallium arsenide. The integrated circuits can be formed
by a series of process steps in which patterned layers of
materials, such as conductive, insulating and semiconducting
materials, are formed on the substrate. In order to maximize the
density of integrated circuits per wafer, it is desirable to have
an essentially planar polished substrate at various stages
throughout the semiconductor wafer production process. Thus,
semiconductor wafer production can include at least one, and more
typically a plurality of polishing steps, which can use one or more
polishing pads.
[0004] A chemical mechanical polishing (CMP) process can include
placing the microelectronic substrate in contact with a polishing
pad; rotating the pad while a force is applied to the backside of
the microelectronic device; and applying an abrasive-containing
chemically-reactive solution commonly referred to as a "slurry" to
the pad during polishing. A CMP polishing slurry can contain an
abrasive material, such as silica, alumina, ceria or mixtures
thereof. The rotational movement of the pad relative to the
substrate as slurry is provided to the device/pad interface can
facilitate the polishing process. In general, polishing can be
continued in this manner until the desired film thickness is
removed.
[0005] Depending on the choice of polishing pad and abrasive, and
other additives, the CMP process can provide effective polishing at
desired polishing rates while reducing or minimizing surface
imperfections, defects, corrosion, and erosion.
[0006] Polishing or planarization characteristics can vary from
pad-to-pad, and throughout the operating lifetime of a given pad.
Variations in the polishing characteristics of the pads can result
in inadequately polished or planarized substrates which are not
useful. Thus, it is desirable in the art to develop a polishing pad
that exhibits reduced pad-to-pad variation in polishing or
planarization characteristics. It is further desirable to develop a
polishing pad that exhibits reduced variations in polishing or
planarization characteristics throughout the operating life of the
pad.
[0007] Planarizing tools having the ability to measure the progress
of the planarization process while the wafer is held in the tool
and in contact with the pad are known in the art. Measuring the
progress of planarizing a microelectronic device during the
planarizing process can be referred to in the art as "in-situ
metrology". U.S. Pat. Nos. 5,964,643 and 6,159,073; and European
Patent 1,108,501 describe polishing or planarizing tools and
in-situ metrology systems. In general, in-situ metrology can
include directing a beam of light through an at least partially
transparent window located in the platen of the tool; the beam of
light can be reflected off the surface of the wafer, back through
the platen window, and into a detector. The polishing pad can
include a window that is at least partially transparent to the
wavelengths used in the metrology system, and essentially aligned
with the planten window.
[0008] Thus, it is desirable to develop a polishing pad that
comprises a window area useful for in-situ metrology. It is further
desirable that the window provides suitable transparency throughout
the operating life of the pad.
[0009] One disadvantage with known pads having windows which are
coplanar with the polishing surface, can include wearing of the
window portion at a slower rate than the pad surface. A further
disadvantage with known pads having a coplanar window can include
scratching of the window as a result of its contact with abrasive
particles in the slurry during the polishing or planarization
process. A scratched window can generally reduce the transparency
of the window and can cause an attenuation of the metrology
signal.
[0010] The present invention includes a polishing pad having a
window. In a non-limiting embodiment, the polishing pad can
comprise a first layer and a second layer. The first layer can
function as the work surface or polishing layer of the pad. At
least a portion of the second layer can comprise a window which is
at least partially transparent to wavelengths used by the metrology
instrumentation of polishing tools. Furthermore, the first layer
can absorb at least 2 percent by weight of polishing slurry based
on the total weight of the first layer.
[0011] The polishing pad of the present invention can comprise a
first layer and a second layer. The first layer can function as the
polishing or working surface of the pad such that the first layer
can at least partially interact with the substrate to be polished
and the polishing slurry. In a non-limiting embodiment, the first
layer can be porous and permeable to polishing slurry. In a
non-limiting embodiment, the second layer can be substantially
nonporous and substantially impermeable to polishing slurry.
[0012] As used herein and the claims the term "substantially
nonporous" means generally impervious to the passage of liquid,
gas, and bacteria. On a macroscopic scale, a substantially
nonporous material exhibits few if any pores. As used herein and
the claims, the term "porous" means having pore(s) and the term
"pore(s)" refers to minute opening(s) through which matter
passes.
[0013] It is noted that, as used in this specification, the
singular forms "a," "an," and "the" include plural referents unless
expressly and unequivocally limited to one referent.
[0014] For the purposes of this specification, unless otherwise
indicated, all numbers expressing quantities of ingredients,
reaction conditions, and so forth used in the specification and
claims are to be understood as being modified in all instances by
the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the following specification
and attached claims are approximations that may vary depending upon
the desired properties sought to be obtained by the present
invention. At the very least, and not as an attempt to limit the
application of the doctrine of equivalents to the scope of the
claims, each numerical parameter should at least be construed in
light of the number of reported significant digits and by applying
ordinary rounding techniques.
[0015] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contain certain errors necessarily resulting from the
standard deviation found in their respective testing
measurements.
[0016] The first layer can include a variety of materials known in
the art. Non-limiting examples of suitable materials comprising the
first layer can include but are not limited to particulate polymer
and crosslinked polymer binder as described in U.S. Pat. No.
6,477,926B1; particulate polymer and an organic polymer binder as
described in U.S. patent application Ser. No. 10/317,982; sintered
particles of thermoplastic resin as described in U.S. Pat. Nos.
6,062,968; 6,117,000; and 6,126,532; and pressure sintered powder
compacts of thermoplastic polymer as described in U.S. Pat. Nos.
6,231,434B1; 6,325,703B2; 6,106,754; and 6,017,265. Further
non-limiting examples of suitable materials comprising the first
layer can include polymeric matrices impregnated with a plurality
of polymeric microelements, wherein each polymeric microelement can
have a void space therein, as described in U.S. Pat. Nos. 5,900,164
and 5,578,362.
[0017] The thickness of the first layer can vary. In alternate
non-limiting embodiments, the first layer can have a thickness of
at least 0.020 inches, or at least 0.040 inches; or 0.150 inches or
less, or 0.080 inches or less.
[0018] In another non-limiting embodiment, the first layer can
include pores such that polishing slurry can be at least partially
absorbed by the first layer. The number of pores can vary. In
alternate non-limiting embodiments, the first layer can have a
porosity, expressed as percent pore volume, of at least 2 percent
by volume based on the total volume of the first layer, or 50
percent or less by volume based on the total volume of the first
layer, or from 2 to 50 percent by volume based on the total volume
of the first layer.
[0019] The percent pore volume of the polishing pad layer can be
determined using a variety of techniques known in the art. In a
non-limiting embodiment, the following expression can be used to
calculate percent pore volume:
100.times.(density of the pad layer).times.(pore volume of the pad
layer).
[0020] The density can be expressed in units of grams per cubic
centimeter, and can be determined by a variety of conventional
methods known in the art. In a non-limiting embodiment, the density
can be determined in accordance with ASTM D 1622-88. The pore
volume can be expressed in units of cubic centimeters per gram, and
can be determined using conventional methods and equipment known in
the art. In a non-limiting embodiment, pore volume can be measured
in accordance with the mercury porosimetry method in ASTM D
4284-88, using an Autopore III mercury porosimeter from
Micromeritics can be used. In a further non-limiting embodiment,
the pore volume measurements can be made under the following
conditions: a contact angle of 140.degree.; a mercury surface
tension of 480 dynes/cm; and degassing of the polishing pad layer
sample under a vacuum of 50 micrometers of mercury.
[0021] In a non-limiting embodiment, the first layer can have an at
least partially open structure such that it can absorb slurry. In
alternate non-limiting embodiments, the first layer can absorb at
least 2 percent by weight of polishing slurry based on the total
weight of the first layer, or not more than 50 percent by weight,
or from 2 percent by weight to 50 percent by weight.
[0022] In another non-limiting embodiment of the present invention,
the first layer of the polishing pad can have a compressibility
greater than the second layer. As used herein, the term
"compressibility" refers to the percent volume compressibility
measurement. In a further non-limiting embodiment, the percent
volume compressibility of the first layer can be at least 0.3
percent; or 3 percent or less; or from 0.3 to 3 percent; when a
load of 20 psi is applied.
[0023] The percent volume compressibility of a pad layer can be
determined using various methods known in the art. In a
non-limiting embodiment, the percent volume compressibility of a
pad layer can be determined using the following expression. 1 100
.times. ( pad layer volume without load - pad layer volume under
load ) ( pad layer volume without load )
[0024] In a non-limiting embodiment, the area of the pad layer does
not change when the load is placed on it; thus, the preceding
equation for volume compressibility can be expressed in terms of
pad layer thickness by the following expression. 2 100 .times. (
pad layer thickness without load - pad layer thickness under load )
( pad layer thickness without load )
[0025] The pad layer thickness can be determined using a variety of
known methods. In a non-limiting embodiment, the pad layer
thickness can be determined by placing a load (such as, but not
limited to, calibrated weights) on the pad sample and measuring the
change in thickness of the pad layer as a result of the load. In a
further non-limiting embodiment, a Mitutoyo Electronic Indicator,
Model ID-C112EB can be used. The indicator has a spindle or
threaded rod which can be fitted at one end with a flat contact
under which the pad layer is placed. The spindle can be fitted at
the other end with a device for applying specified loads to the
contact area, such as but not limited to a balance pan which
accepts calibrated weights. The Indicator displays the displacement
of the pad layer resulting from applying the load. The Indicater
display is typically representative of inches or millimeters. The
Electronic Indicator can be mounted on a stand, such as a Mitutoyo
Precision Granite Stand, to provide stability while taking the
measurements. The lateral dimensions of the pad layer can be
sufficient to permit measurements at least 0.5" from any edge. The
surface of the pad layer can be flat and parallel over a sufficient
area to permit uniform contact between the test pad layer and the
flat contact. The pad layer to be tested can be placed under the
flat contact. The thickness of the pad layer can be measured prior
to applying the load. Calibrated balance weights can be added to
the balance pan for a specific resultant load. The pad layer then
can be compressed under the specified load. The Indicator can
display the thickness/height of the pad layer under the specified
load. The thickness of the pad layer prior to applying the load
minus the thickness of the pad layer under the specified load can
be used to determine the displacement of the pad layer. In a
non-limiting embodiment, a load of 20 psi can be applied to the pad
layer. Measurements can be made at a standardized temperature such
as room temperature. In a non-limiting embodiment, measurements can
be taken at a temperature of 22.degree. C+/-2.degree. C.
[0026] In alternate non-limiting embodiments, the above-described
method of measuring pad layer thickness can be applicable to a
stacked pad assembly or layer(s) comprising the stacked pad
assembly.
[0027] In a non-limiting embodiment, a procedure for measuring
percent volume compressibility can include placing the contact on
the granite base and adjusting the indicator to read zero. The
contact can then be raised and the specimen placed on the granite
stand under the contact with the edge of the contact at least 0.5"
from any edge of the specimen. The contact can be lowered onto the
specimen and the specimen thickness measurement can be taken after
5+/-1 seconds. Without moving the specimen or the contact,
sufficient weight can be added to the pan to cause a force of 20
psi to be applied to the specimen by the contact. The reading for
the specimen thickness under load measurement can be made after
15+/-1 seconds. The measurement procedure can be repeated, making
five measurements at different positions on the specimen at least
0.25" apart using 20 psi of compressive force.
[0028] In a non-limiting embodiment, the softness of the first
layer can be determined. As used herein and the claims, the term
"softness" refers to the Shore A Hardness of the material. In
general, the softer the material, the lower the Shore A Hardness
value. In alternate non-limiting embodiments, the first layer can
have a Shore A Hardness of at least 85; or 99 or less, or from 85
to 99. The Shore A Hardness value can be determined using various
methods and equipment known in the art. In a non-limiting
embodiment, Shore A Hardness can be determined in accordance with
the procedure recited in ASTM D 2240, using a Shore "Type A"
Durometer having a maximum indicator (available from PCT
Instruments, Los Angeles, Calif.). In a non-limiting embodiment,
the test method for Shore A Hardness can include the penetration of
a specific type of indentor being substantially forced into the
test material under specified conditions. In this embodiment, the
Shore A Hardness can be inversely related to the penetration depth
and can be dependent on the elastic modulus and viscoelastic
behavior of the test material.
[0029] In a non-limiting embodiment, the first layer can comprise
grooves or pattern on the work or polishing surface. The types of
grooves and/or patterns can vary and can include the various types
of grooves and/or patterns known in the art. The process for making
the grooves and patterns can also vary and can include the various
conventional methods known in the art.
[0030] The polishing pad of the present invention further comprises
a second layer. In a non-limiting embodiment, the second layer can
be connected to at least a portion of the first layer. In a further
non-limiting embodiment, the first layer can be connected to at
least a portion of the second layer, and the second layer can be
connected to at least a portion of an optional third layer.
[0031] The second layer can include a variety of materials known in
the art. The second layer can be selected from substantially
non-volume compressible polymers and metallic films and foils. As
used herein and the claims, "substantially non-volume compressible"
means that the volume can be reduced by less than 1% when a load of
20 psi is applied. In a non-limiting embodiment, the method for
applying the load and measuring the reduction in volume is
previously described herein can be employed.
[0032] Non-limiting examples of substantially non-volume
compressible polymers can include polyolefins, such as but not
limited to low density polyethylene, high density polyethylene
ultra-high molecular weight polyethylene and polypropylene;
[0033] polyvinylchloride; cellulose-based polymers, such as but not
limited to cellulose acetate and cellulose butyrate; acrylics;
polyesters and co-polyesters, such as but not limited to PET and
PETG; polycarbonate; polyamides, such as but not limited to nylon
6/6 and nylon 6/12; and high performance plastics, such as but not
limited to polyetheretherketone, polyphenylene oxide, polysulfone,
polyimide, and polyetherimide; and mixtures thereof.
[0034] Non-limiting examples of metallic films can include but are
not limited to aluminum, copper, brass, nickel, stainless steel,
and combinations thereof.
[0035] The thickness of the second layer can vary. In alternate
non-limiting embodiments, the second layer can have a thickness of
at least 0.0005, or at least 0.0010; or 0.0650 inches or less, or
0.0030 inches or less.
[0036] In a non-limiting embodiment, the second layer can be
flexible to enhance or increase the uniformity of contact between
the polishing pad and the surface of the substrate being polished.
A consideration in selecting the material for the second layer can
be the capability of a material to provide compliant support to the
work surface of the polishing pad such that the first layer
substantially conforms to the macroscopic contour or long-term
surface of the device being polished. A material having said
capability can be desirable for use as the second layer in the
present invention.
[0037] The flexibility of the second layer can vary. The
flexibility can be determined using a variety of conventional
techniques known in the art. As used herein and the claims the term
"flexibility" (F) refers to the inverse relationship of second
layer thickness cubed (t.sup.3) and the flexural modulus of the
second layer material (E), i.e. F=1/t.sup.3E. In alternate
non-limiting embodiments, the flexibility of the second layer can
be at least 0.5 in.sup.-1 lb.sup.-1; or at least 100 in.sup.-1
lb.sup.-1; or from 1 in.sup.-1 lb.sup.-1 to 100 in.sup.-1
lb.sup.-1.
[0038] In a non-limiting embodiment, the second layer can have a
compressibility which allows the polishing pad to substantially
conform to the surface of the article to be polished. The surface
of a microelectronic substrate, such as a semiconductor wafer, can
have a "wave" contour as a result of the manufacturing process. It
is contemplated that if the polishing pad cannot adequately conform
to the "wave" contour of the substrate surface, the uniformity of
the polishing performance can be degraded. For example, if the pad
substantially conforms the ends of the "wave", but cannot
substantially conform and contact the middle portion of the "wave",
only the ends of the "wave" can be polished or planarized and the
middle portion can remain substantially unpolished or
unplanarized.
[0039] The compressibility of the second layer can vary. As
previously described, the term "compressibility" refers to the
percent volume compressibility measurement. In alternate
non-limiting embodiments, the percent volume compressibility of the
second layer can be at least one percent; or three percent or less;
or from one to three percent.
[0040] The percent volume compressibility can be determined using a
variety of conventional methods known in the art. In a non-limiting
embodiment, the percent volume compressibility is determined as
previously described herein.
[0041] In another non-limiting embodiment, the second layer can
distribute the compressive forces experienced by the first layer
over a larger area of an optional third layer. In a non-limiting
embodiment, the second layer is substantially non-volume
compressible.
[0042] In another non-limiting embodiment, the second layer can
function as a substantial barrier to fluid transport between the
first layer and an optional third layer at least partially
connected to the second layer. Thus, a consideration in selecting
the material comprising the second layer can be the ability of the
material to substantially reduce, minimize or essentially prevent
the transport of polishing slurry from the first layer to an
optional third layer. In a non-limiting embodiment, the second
layer can be substantially impermeable to the polishing slurry such
that the optional third layer does not become saturated with
polishing slurry.
[0043] In an alternate non-limiting embodiment, the second layer
can be perforated such that polishing slurry can penetrate the
first and second layers to wet an optional third layer. In a
further non-limiting embodiment, the optional third layer can be
substantially saturated with polishing slurry. The perforations in
the second layer can be formed by a variety of techniques known to
the skilled artisan, such as but not limited to punching, die
cutting, laser cutting or water jet cutting. The hole size, number
and configuration of the perforations can vary. In a non-limiting
embodiment, the perforation hole diameter can be at least {fraction
(1/16)} inch with at least 26 holes per square inch in a staggered
hole pattern.
[0044] In a non-limiting embodiment, the first layer can be
connected to at least a portion of the second layer to produce a
stacked pad assembly. As used herein and the claims, the term
"connected to" means to link together or place in relationship
either directly, or indirectly by one or more intervening
materials. In a non-limiting embodiment, the first and second
layers are at least partially connected such that the opening of
the first layer can be at least partially aligned with the at least
partially transparent window of the second layer.
[0045] In a non-limiting embodiment, the first layer of the
polishing pad can be connected to at least a portion of the second
layer using an adhesive. A suitable adhesive for use in the present
invention can provide sufficient peel resistance such that the pad
layers essentially remain in place during use. Further, the
adhesive can be selected to sufficiently withstand shear stresses
which are present during the polishing or planarization process and
moreover, can sufficiently resist chemical and moisture degradation
during use. The adhesive can be applied using conventional
techniques known to the skilled artisan. In a non-limiting
embodiment, the adhesive can be applied to a lower surface of the
first layer and/or an upper surface of the second layer which are
parallel facing to one another.
[0046] The adhesive can be chosen from a wide variety of adhesive
materials known in the art, such as but not limited to contact
adhesives, pressure sensitive adhesives, structural adhesives, hot
melt adhesives, thermoplastic adhesives, and curable adhesives,
such as thermosetting adhesives. Non-limiting examples of
structural adhesives can be chosen from polyurethane adhesives, and
epoxy resin adhesives; such as those based on the diglycidyl ether
of bisphenol A. Non-limiting examples of pressure sensitive
adhesives can include an elastomeric polymer and a tackifying
resin.
[0047] The elastomeric polymer can be chosen from natural rubber,
butyl rubber, chlorinated rubber, polyisobutylene, poly(vinyl alkyl
ethers), alkyd adhesives, acrylics such as those based on
copolymers of 2-ethylhexyl acrylate and acrylic acid, block
copolymers such as styrene-butadiene-styrene, and mixtures thereof.
In a non-limiting embodiment, a pressure sensitive adhesive can be
applied to a substrate using an organic solvent such as toluene or
hexane, or from a water-based emulsion or from a melt. As used
herein, "hot melt adhesive" refers to an adhesive comprised of a
nonvolatile thermoplastic material that can be heated to a melt,
then applied to a substrate as a liquid. Non-limiting examples of
hot melt adhesives can be chosen from ethylene-vinyl acetate
copolymers, styrene-butadiene copolymers, ethylene-ethyl acrylate
copolymers, polyesters, polyamides such as those formed from the
reaction of a diamine and a dimer acid, and polyurethanes.
[0048] In a non-limiting embodiment of the present invention, the
first layer can comprise an opening. In a further non-limiting
embodiment, at least a portion of the second layer can comprise a
window which is at least partially transparent to wavelengths used
by the metrology instrumentation of the planarizing equipment. The
size, shape, and positioning of the opening in the first layer
and/or the window in the second layer can be dependent upon the
metrology instrumentation and polishing apparatus being employed to
polish and/or planarize the pad. The opening can be produced by a
variety of conventional methods known in the art. In alternate
non-limiting embodiments, the opening can be made by punching, die
cutting, laser cutting or water jet cutting. In a further
non-limiting embodiment, the opening can be formed by molding the
first layer. In an alternate non-limiting embodiment, the openings
can be die cut into the first layer using an NAEF Model B die press
fitted with dies of suitable size and shape, which are commercially
available from MS Instruments Company, Stony Brook, N.Y.
[0049] In a non-limiting embodiment, the opening in the first layer
can be produced prior to stacking together and/or at least
partially connecting the first layer with the second layer.
[0050] At least a portion of the second layer can comprise an at
least partially transparent window. In a non-limiting embodiment,
the second layer can comprise an at least partially transparent
material. In another non-limiting embodiment, the second layer can
comprise a substantially non-transparent material; an opening can
be cut into the second layer to remove a portion of the second
layer; an at least partially transparent material can be inserted
into the opening in the second layer. The opening can be made using
a variety of methods previously described herein. In a non-limiting
example, the second layer can include a metal foil; an opening can
be cut into the metal foil to remove a portion of the metal foil; a
piece of polyester can be cut into a size and shape that
substantially corresponds to the opening; the polyester can be
fitted into the opening in the metal foil to form an at least
partially transparent window.
[0051] In a non-limiting embodiment, the second layer can comprise
an adhesive assembly. The adhesive assembly can include interposing
the second layer between an upper adhesive layer and a lower
adhesive layer. In a non-limiting embodiment, the upper adhesive
layer of the adhesive assembly can be at least partially connected
to the lower surface of the first layer. The lower adhesive layer
of the adhesive assembly can be at least partially connected to the
upper surface of an optional third layer. The second layer of the
adhesive assembly can be selected from the aforementioned suitable
materials for the second layer of the polishing pad. The upper and
lower adhesive layers of the adhesive assembly can be selected from
the non-limiting examples of adhesives previously mentioned herein.
In a non-limiting embodiment, the upper and lower adhesive layers
each can be contact adhesives. The adhesive assembly can be
referred to in the art as two-sided or double coated tape.
Non-limiting examples of commercially available adhesive assemblies
include those from 3M, Industrial Tape and Specialties
Division.
[0052] In a further non-limiting embodiment, at least a portion of
the adhesive layer can be removed from the second layer of the
adhesive assembly exposing at least a portion of the at least
partially transparent middle layer of the adhesive assembly,
thereby forming an at least partially transparent window in the
second layer. In alternate non-limiting embodiments, the removal of
the adhesive can be performed prior to stacking the layers or after
the layers are stacked. The removal process can include a variety
of methods known to the skilled artisan, including but not limited
to dissolution of the adhesive in solvent or aqueous detergent
solution, or physically stripping the adhesive from the second
layer. In a non-limiting embodiment, physically stripping the
adhesive can be include contacting the adhesive with a material to
which the adhesive substantially adheres, and then pulling the
material from the second layer, whereby the adhesive is removed
with the material.
[0053] In a further non-limiting embodiment, the window of the
second layer can be recessed below the polishing surface of the pad
by a distance equal to the thickness of the first layer of the
pad.
[0054] In another non-limiting embodiment, the pad assembly can
include a coating on at least a portion of the top and/or bottom
sides of the window of the second layer. The coating can be at
least partially applied with an adhesive in place or following
removal of the adhesive. The coating can be at least partially
applied prior to stacking the layers or after the layers have been
stacked. The coating can provide any one of the following
properties, for example: improved transparency of the window area,
improved abrasion resistance, improved puncture resistance. In a
non-limiting embodiment, the coating can include a resin film, or a
cast-in-place resin coating.
[0055] Non-limiting examples of suitable resin films for use in the
present invention can include the materials described above for the
second layer. In alternative non-limiting embodiments, the resin
film chosen for the coating can be the same material or different
material as that comprising the second pad layer. The resin film
can be at least partially adhered to the window area of the second
layer by any means known to the skilled artisan, such as the
adhesive methods and materials listed above for pad stack
adhesives. In a non-limiting embodiment, the coating can be a layer
of resin film that can be the same as the material used for the
second layer. The coating can be at least partially applied after
assembly of the pad stack. The coating can be at least partially
applied to both the top and bottom surfaces of the window area of
the second layer, and the adhesive can be at least partially
adhered using a contact adhesive used as the stack adhesive.
[0056] In a non-limiting embodiment, the coating can be a
cast-in-place resin coating, which can be applied as a liquid, as a
solvent solution, dispersion, or aqueous latex; as a melt, or as a
blend of resin precursors that can react to form the coating. The
application of the liquid can be accomplished by a variety of known
methods, including spraying, padding, and pouring. Non-limiting
examples of suitable materials for the coating include
thermoplastic acrylic resins, thermoset acrylic resins, such as
hydroxyl-functional acrylic latexes crosslinked with
urea-formaldehyde or melamine-formaldehyde resins,
hydroxyl-functional acrylic resins crosslinked with epoxy resins,
or carboxyfunctional acrylic latexes crosslinked with carbodiimides
or polyimines or epoxy resins; urethane systems, such as
hydroxyfunctional acrylic resin crosslinked with polyisocyanate,
moisture-cured isocyanate-terminated resins; carbamate-funtional
acrylic resins crosslinked with melamine-formaldehyde resins; epoxy
resins, such as polyamide resin crosslinked with bisphenol A epoxy
resins, phenolic resins crosslinked with bisphenol A epoxy resins;
polyester resins, such as hydroxyl-terminated polyesters
crosslinked with melamine-formaldehyde resins or with
polyisocyanates or with epoxy crosslinkers.
[0057] In a non-limiting embodiment, the coating can be an aqueous
acrylic latex, which can be applied following stacking of the pad
assembly. The coating can be at least partially applied to the top
and bottom surfaces of the window area of the second layer.
Application of the coating can be performed following removal of an
adhesive from the window area.
[0058] The window pad of the present invention can be used with a
variety of polishing equipment known in the art. In a non-limiting
embodiment, a Mirra polisher, produced by Applied Materials Inc,
Santa Clara Calif., can be used wherein the shape of the opening is
a rectangle, having a size 0.5".times.2", being positioned with the
long axis radially oriented and centered 4" from the center of the
pad. The platen for the Mirra polisher is 20" in diameter. A pad
for use with this polisher can comprise a circle of a 20-inch
diameter having a window located in the area as described.
[0059] In a further non-limiting embodiment, a Teres polisher
commercially available from Lam Research Corporation, Fremont,
Calif., can be employed. This polisher uses a continuous belt
instead of a circular platen. The pad for this polisher can be a
continuous belt of 12" width and 93.25" circumference, which has a
window area suitably sized and positioned to align with the
metrology window of the Teres polisher can be such that it can be
at least partially aligned with the at least partially transparent
window in the second layer.
[0060] As identified previously herein, the polishing pad of the
present invention can comprise additional optional layer(s). The
additional layer(s) can contain opening(s) that are substantially
aligned with the opening in the first layer and the at least
partially transparent window in the second layer.
[0061] In a non-limiting embodiment, the polishing pad of the
present invention can comprise a third layer. The third layer can
function as the bottom layer of the pad which can be attached to
the platen of the polishing apparatus.
[0062] In a non-limiting embodiment, the third layer can comprise a
material that is softer than the first layer. As used herein, the
term "softness" refers to the Shore A Hardness of the material. The
softer the material, the lower the Shore A Hardness value. Thus, in
the present invention, the Shore A Hardness value of the third
layer can be lower than the Shore A Hardness value of the first
layer. In a non-limiting embodiment, the third layer can have a
Shore A Hardness of at least 15. In alternate non-limiting
embodiments, the Shore A Hardness of the third layer can be at
least 45, or 75 or less, or from 45 to 75. The Shore A Hardness can
be determined using a variety of conventional methods known in the
art. In a non-limiting embodiment, the Shore A Hardness can be
determined as previously described herein.
[0063] In a non-limiting embodiment, the third layer can be used to
increase the uniformity of contact between the polishing pad and
the surface of the substrate undergoing polishing.
[0064] In a non-limiting embodiment of the present invention, the
material comprising the third layer of the polishing pad can have a
compressibility greater than the material comprising the first
layer. As previously described, the term "compressibility" refers
to the percent volume compressibility measurement. Thus, the
percent volume compressibility of the third layer is greater than
the percent volume compressibility of the first layer. In a
non-limiting embodiment, the percent volume compressibility of the
third layer can be less than 20 percent when a load of 20 psi is
applied. In alternate non-limiting embodiments, the percent volume
compressibility of the third layer can be less than 10 percent when
a load of 20 psi is applied, or less than 5 percent when a load of
20 psi is applied. As previously identified percent volume
compressibility can be determined by a variety of conventional
methods known in the art. In a non-limiting embodiment, percent
volume compressibility can be determined as previously described
herein.
[0065] The thickness of the third layer can vary. In general, the
third layer thickness should be such that the pad is not too thick.
A pad which is too thick can be difficult to place on and take off
of the planarization equipment. Thus, in alternate non-limiting
embodiments, the thickness of the first layer can be at least 0.040
inches, or at least 0.045 inches; or 0.100 inches or less, or 0.080
inches or less, or 0.065 inches or less.
[0066] The sublayer can comprise a wide variety of materials known
in the art. Suitable materials can include natural rubber,
synthetic rubbers, thermoplastic elastomer, foam sheet and
combinations thereof. The material of the sublayer can be foamed or
blown to produce a porous structure. The porous structure can be
open cell, closed cell, or combinations thereof. Non-limiting
examples of synthetic rubbers can include neoprene rubber, silicone
rubber, chloroprene rubber, ethylene-propylene rubber, butyl
rubber, polybutadiene rubber, polyisoprene rubber, EPDM polymers,
styrene-butadiene copolymers, copolymers of ethylene and ethyl
vinyl acetate, neoprene/vinyl nitrile rubber, neoprene/EPDM/SBR
rubber, and combinations thereof. Non-limiting examples of
thermoplastic elastomers can include polyolefins, polyesters,
polyamides, polyurethanes such as those based on polyethers and
polyesters, and copolymers thereof. Non-limiting examples of foam
sheet can include ethylene vinyl acetate sheets and polyethylene
foam sheets, such as but not limited to those which are
commercially available from Sentinel Products, Hyannis, N.J.;
polyurethane foam sheets, such as but not limited to those which
are commercially available from Illbruck, Inc., Minneapolis, Minn.;
and polyurethane foam sheets, and polyolefin foam sheets, such as
but not limited to those which are available from Rogers
Corporation, Woodstock, Conn. In a further non-limiting embodiment,
the sublayer can include non-woven or woven fiber mat, and
combinations thereof; such as but not limited to polyolefin,
polyester, polyamide, or acrylic fibers, which have been
impregnated with a resin. The fibers can be staple or substantially
continuous in the fiber mat. Non-limiting examples can include but
are not limited to non-woven fabric impregnated with polyurethane
as describe in U.S. Pat. No. 4,728,552, such as polyurethane
impregnated felt. A non-limiting example of a commercially
available non-woven subpad can be Suba.TM. IV, from Rodel, Inc.
Newark Del.
[0067] In the present invention, the optional third layer can
comprise an opening. In alternate non-limiting embodiments, the
opening can be produced by any suitable means known in the art,
such as those previously identified relative to the opening in the
first layer. Further, as previously identified, the size, shape and
position of the opening can be dependent upon the metrology
instrumentation and polishing apparatus employed.
[0068] In a non-limiting embodiment, the third layer can be at
least partially connected to the second layer and can be in contact
with the base of the planarizing machine. The third layer can
contain an opening that is at least partially aligned with the
opening of the first layer and the at least partially transparent
or window area of the second layer.
[0069] In an alternate non-limiting embodiment, the first layer of
the polishing pad can be connected to at least a portion of the
second layer and the second layer can be connected to at least a
portion of a third layer using an adhesive. Suitable adhesives can
include those previously recited herein.
[0070] In a further non-limiting embodiment, the polishing pad of
the present invention can comprise a first layer, a second layer,
and a third layer. The first and third layers each comprise an
opening. The opening of the first and third layers can be at least
partially aligned with one another. At least a portion of the
second layer can include an at least partially transparent window.
The window can be at least partially coated on both sides with
contact adhesive, and the layers can be pressed together to form a
stacked pad assembly. The adhesive can then be physically stripped
from the top and bottom surface of the window area of the second
layer using a material to which the adhesive substantially adheres.
A non-limiting example of a material to which the adhesive
substantially adheres is Teslin.RTM. SP-100 0, a synthetic sheet
material which is commercially available from PPG Industries, Inc,
Pittsburgh, Pa.
[0071] The polishing pads of the present invention can be used in
combination with polishing slurrys, such as polishing slurries,
which are known in the art. Non-limiting examples of suitable
slurries for use with the pad of the present invention, include but
are not limited to the slurries disclosed in U.S. patent
application Ser. Nos. 09/882,548 and 09/882, 549, which were both
filed on Jun. 14, 2001 and are pending. In a non-limiting
embodiment, the polishing slurry can be interposed between the
first layer of the pad and the substrate to be polished. The
polishing or planarizing process can include moving the polishing
pad relative to the substrate being polished. A variety of
polishing slurrys or slurries are known in the art. Non-limiting
examples of suitable slurries for use in the present invention
include slurries comprising abrasive particles. Abrasives that can
be used in the slurries include particulate cerium oxide,
particulate alumina, particulate silica and the like. Examples of
commercial slurries for use in the polishing of semiconductor
substrates include but are not limited to ILD1200 and ILD1300
available from Rodel, Inc. Newark Del. and Semi-Sperse AM100 and
Semi-Sperse 12 available from Cabot Microelectronics Materials
Division, Aurora, Ill.
[0072] In a non-limiting embodiment, the polishing pad of the
present invention can be utilized with an apparatus for planarizing
an article having a non-planar surface. The planarizing apparatus
can include a retaining means for holding the article; and a motive
power means for moving the pad and the retaining means with respect
to the other such that movement of the pad and the retaining means
causes the slurry and the planarizing surface of the pad to contact
and planarize the non-planar surface of the article. In a further
non-limiting embodiment, the planarizing apparatus can include a
means of renewing the polishing or planarizing surface of the pad.
A non-limiting example of a suitable renewing means includes a
mechanical arm equipped with an abrasive disk which abrades the
work surface of the pad.
[0073] In an alternate non-limiting embodiment, the planarizing
apparatus can include an apparatus for conducting in-situ metrology
of the article being polished or planarized. Commercial polishing
or planarizing apparatuses are available from equipment
manufacturers such as Applied Materials, LAM Research,
SpeedFam-IPEC, and Ebara Corp.
[0074] In a non-limiting embodiment, the pad of the present
invention can be placed on a cylindrical metal base; and can be
connected to at least a portion of the base with a layer of
adhesive. Suitable adhesives can include a wide variety of known
adhesives. In a further non-limiting example, the pad can be placed
on the cylindrical metal base or platen of a polishing or
planarizing apparatus that includes a means of conducting in-situ
metrology of the article being polished. The pad can be placed such
that its window can be aligned with the metrology window of the
platen.
EXAMPLE 1
[0075] A polishing pad with a window was prepared as follows:
[0076] 1. A first layer was prepared according to Recipe A
described below.
[0077] 2. A 1/2".times.2" rectangular hole was cut into the first
layer using a straight-edge and a scalpel-style utility knife.
[0078] 3. A second layer was formed using High Performance Double
Coated Tape 9500PC, commercially obtained from 3M Industrial Tape
and Specialties Division. The adhesive layer of the tape was
adhered to the bottom side of the first layer such that the
rectangular opening in the first layer was substantially spanned by
the tape.
[0079] 4. A third layer was formed using a 0.060" thick sheet of
polyurethane foam, having trade name PORON 4701-50, commercially
obtained from Rogers Corporation. A 1/2".times.2" rectangular hole
was cut into the third layer using a straight-edge and a
scalpel-style utility knife.
[0080] 5. The third layer was adhered to the second layer by
removing the release paper from the second layer and applying the
third layer to the adhesive film thus exposed. The third layer was
positioned such that the rectangular openings in the first layer
and the third layer were substantially aligned.
[0081] 6. The three-layer stack assembly was then pressed together
and passed through a calendar roll set.
[0082] 7. A window was formed by removing a portion of the adhesive
on the upper and lower sides of the second layer. The adhesive was
removed by contacting it with a 1/2".times.2" rectangular piece of
Teslin SP-1000, commercially available from PPG Industries,
Incorporated, pressing the piece by hand to ensure good contact
between the adhesive and the Teslin SP-1000, then peeling away the
Teslin SP-1000. The adhesive selectively adhered to the Teslin
SP-1000, leaving the substantially clear film of the window free of
adhesive.
[0083] The resulting pad stack had a rectangular window having a
size of 1/2".times.2".
[0084] Recipe A for Pad First Layer:
[0085] Step 1
[0086] Particulate crosslinked polyurethane was prepared using the
ingredients listed in Table A.
1 TABLE A Ingredients Weight (grams) Charge 1 diamine curative (a)
810 surfactant (b) 30.6 methyl isobutyl ketone solvent 822 Charge 2
isocyanate functional prepolymer (c) 2112 (a) LONZACURE MCDEA
diamine curative obtained from Air Products and Chemicals, Inc,
which describes it as methylene bis(chlorodiethylanaline). (b)
PLURONIC F108 surfactant, obtained from BASF Corporation. (c)
ARITHANE PHP-75D prepolymer, obtained from Air Products and
Chemicals, Inc, which describes it as the isocyanate functional
reaction product of toluene diisocyanate and poly(tetramethylene
glycol).
[0087] Charge 1 was added to an open container and warmed with
stirring on a hot plate until the contents of the container reached
a temperature of 35.degree. C. Stirring was continued at this
temperature until the ingredients formed a substantially
homogeneous solution. The container was then removed from the hot
plate. Charge 2 was warmed to a temperature of 55.degree. C. using
a water bath then added to Charge 1. The contents were mixed for a
period of three (3) minutes with a motor driven impeller until
uniform. The contents of the container were then quickly poured
into 10 kilograms of deionized water at a temperature of 40.degree.
C., with concurrent vigorous stirring of the deionized water. Upon
completion of the addition of the contents of the container,
vigorous mixing of the deionized water was continued for an
additional 60 minutes. The wet particulate crosslinked polyurethane
was classified using a stack of two sieves. The top sieve had a
mesh size of 50 mesh (300 micron sieve openings), and the bottom
sieve had a mesh size of 140 mesh (105 micron sieve openings). The
isolated particulate crosslinked polyurethane from the 140 mesh was
dried overnight in an oven at a temperature of 80.degree. C.
[0088] Step 2:
[0089] A polishing pad comprising particulate crosslinked
polyurethane and crosslinked polyurethane binder was prepared using
the ingredients summarized in the following Table B.
2 TABLE B Ingredients Weight (grams) Charge 1 particulate
crosslinked polyurethane 918 of Step 1 Charge 2 isocyanate
functional prepolymer (c) 265 aliphatic polyisocyanate (d) 8.5
additive (e) 8.5 acetone solvent 62 (d) DESMODUR N 3300 aliphatic
polyisocyanate, obtained from Bayer Corporation, Coatings and
Colorants Division, which describes it as a polyfunctional
aliphatic isocyanate resin based on hexamethylene diisocyanate. (e)
Lanco PP1362D micronized modified polypropylene wax, obtained from
The Lubrizol Corporation.
[0090] Charge 2 was mixed until substantially homogeneous, using a
motor driven stainless steel impeller. The substantially homogenous
mixture of Charge 2 was then combined with Charge 1 in a suitable
container and mixed together by means of a motor driven mixer. A
1040 gram portion of the combination of Charges 1 and 2 was then
introduced onto a 26".times.26" flat mold. The mold was fed through
a pair of rollers at ambient temperature to form a sheet that was
0.100" thick. The sheet was cured at a temperature of 25.degree. C.
and 80% relative humidity for 18 hours, followed by a temperature
of 130.degree. C. for 1 hour. Circular pads with a 22.5" diameter
were cut from the sheet then the upper and lower surfaces of the
pad were made parallel using a milling machine.
[0091] The resulting pad was used as the first layer in Example
1.
* * * * *