U.S. patent application number 10/974528 was filed with the patent office on 2006-04-27 for polyurethane urea polishing pad.
Invention is credited to William C. Allison, Robert G. Swisher, Alan E. Wang.
Application Number | 20060089095 10/974528 |
Document ID | / |
Family ID | 35005713 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060089095 |
Kind Code |
A1 |
Swisher; Robert G. ; et
al. |
April 27, 2006 |
Polyurethane urea polishing pad
Abstract
The present invention relates to an article for altering a
surface of a workpiece, or a polishing pad having a window. In
particular, the polishing pad includes a polyurethane urea material
wherein the polyurethane urea material contains cells which are at
least partially filled with gas. The polyurethane urea material can
be prepared by combining polyisocyanate and/or polyurethane
prepolymer, hydroxyl-containing material, amine-containing material
and blowing agent. The polishing pad according to the present
invention is useful for polishing articles, and is especially
useful for chemical mechanical polishing or planarization of
microelectronic and optical electronic devices such as but not
limited to semiconductor wafers. 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) ; Wang; Alan E.; (Gibsonia,
PA) ; Allison; William C.; (Murrysville, PA) |
Correspondence
Address: |
PPG Industries, Inc.;Law Department - Intellectual Property
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
35005713 |
Appl. No.: |
10/974528 |
Filed: |
October 27, 2004 |
Current U.S.
Class: |
451/533 |
Current CPC
Class: |
Y10T 156/1057 20150115;
B24B 37/205 20130101 |
Class at
Publication: |
451/533 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A polyurethane urea-containing pad adapted to polish a
microelectronic substrate, said pad comprising an at least
partially transparent window formed by a cast-in-place process,
wherein said polyurethane urea comprises at least partially
gas-filled cells, and wherein at least a portion of said at least
partially gas-filled cells is formed by an in-situ reaction.
2. The pad of claim 1 wherein said pad comprises the reaction
product of polyisocyanate, hydroxyl-containing material,
amine-containing material and blowing agent.
3. The pad of claim 1 wherein said pad comprises the reaction
product of polyurethane prepolymer amine-containing material and
blowing agent.
4. The pad of claim 1 wherein said pad comprises the reaction
product of polyisocyanate and polyurethane prepolymer, optional
hydroxyl-containing material, amine-containing material and blowing
agent.
5. The pad of claim 1 further comprising a sub-pad.
6. The pad of claim 5 wherein said sub-pad can be chosen from
non-woven fiber mat, woven fiber mat, or combinations thereof.
7. The pad of claim 6 wherein said sub-pad is chosen from
polyolefin, polyester, polyamide, or acrylic fibers which have been
impregnated with a resin, and combinations thereof.
8. The pad of claim 5 wherein said sub-pad is chosen from foam
sheet made of natural rubbers, synthetic rubbers, thermoplastic
elastomers; polyurethane and polyurethane urea impregnated felt;
and combinations thereof.
9. The pad of claim 5 wherein said pad is at least partially
connected to said sub-pad.
10. The pad of claim 1 further comprising a second layer.
11. The pad of claim 10 wherein said second layer is at least
partially connected to said pad.
12. The pad of claim 11 wherein said second layer is at least
partially connected to a sub-pad.
13. The pad of claim 10 wherein said second layer is chosen from
polyolefins, cellulose-based polymers, acrylics, polyesters and
co-polyesters, polycarbonates, polyamides, plastics, and
combinations thereof.
14. The pad of claim 10 wherein said second layer is chosen from
substantially non-compressible polymers, metallic films and foils,
and combinations thereof.
15. The pad of claim 1 wherein said window comprises a polymer
derived from a resin material.
16. The pad of claim 15 wherein said resin material is chosen from
polyurethane prepolymers with curative, epoxy resins with curative,
ultraviolet curable acrylics, and mixtures thereof.
17. The pad of claim 15 wherein said resin material is chosen from
thermoplastic acrylic resins, thermoset acrylic resins, urethane
systems, epoxy resins, polyester resins, and mixtures thereof.
18. The pad of claim 15 wherein said resin material is chosen from
hydroxyl-functional acrylic resins crosslinked with
urea-formaldehyde or melamine-formaldehyde resins,
hydroxyl-functional acrylic resins crosslinked with epoxy resins,
or carboxyfunctional acrylic resins crosslinked with carbodiimides
or polyimines or epoxy resins, hydroxyfunctional acrylic resins
crosslinked with polyisocyanate, diamine cured
isocyanate-terminated prepolymers, isocyanate-terminated
prepolymers crosslinked with polyamines, amine-terminated resins
crosslinked with polyisocyanates, carbamate-functional acrylic
resins crosslinked with melamine-formaldehyde resins, polyamide
resin crosslinked with bisphenol A epoxy resins, phenolic resins
crosslinked with bisphenol A epoxy resins, hydroxyl-terminated
polyesters crosslinked with melamine-formaldehyde resins or with
polyisocyanates or with epoxy crosslinkers, and mixtures
thereof.
19. The pad of claim 15 wherein said resin material comprises
amine-terminated oligomer, diamine, and polyisocyanate.
20. The pad of claim 1 wherein said window is at least partially
transparent to at least one wavelength in the range of from 190 to
3500 nanometers.
21. The pad of claim 1 wherein said cure temperature is from
5.degree. C. to 120.degree. C.
22. The pad of claim 1 wherein said cure temperature is from
10.degree. C. to 115.degree. C.
23. The pad of claim 1 wherein said cure temperature is from
15.degree. C. to 110.degree. C.
24. The pad of claim 1 wherein said cure temperature is from
22.degree. C. to 105.degree. C.
25. A device for polishing a microelectronic substrate, said device
comprising: a pad having a pair of spaced surfaces, at least a
portion of said pad comprising a closed-cell polyurethane urea foam
having gas-containing cells formed by an in-situ reaction; and a
window in said pad, said window comprising an aperture in said pad
extending through said surfaces, and a translucent panel attached
to said pad within the aperture, said panel being formed in said
aperture by a cast-in-place process.
26. The device of claim 25 wherein said pad further comprises a
sub-pad.
27. The device of claim 25 wherein said pad comprises the reaction
product of polyisocyanate, hydroxyl-containing material,
amine-containing material and blowing agent.
28. The device of claim 25 wherein said pad comprises the reaction
product of polyurethane prepolymer, amine-containing material and
blowing agent.
29. The device of claim 25 wherein said pad comprises the reaction
product of polyisocyanate and polyurethane prepolymer, optional
hydroxyl-containing material, amine-containing material and blowing
agent.
30. The device of claim 25 wherein said window comprises a resin
material.
31. The device of claim 25 wherein said resin material is chosen
from polyurethane prepolymers with curative, epoxy resins with
curative, ultraviolet curable acrylics, and mixtures thereof.
32. The device of claim 25 wherein said window is at least
partially transparent to at least one wavelength in the range of
from 190 to 3500 nanometers.
33. A method for producing a polishing pad comprising an at least
partially transparent window, comprising: a. forming a polyurethane
urea-containing pad wherein said polyurethane urea comprises at
least partially gas-filled cells, and wherein at least a portion of
said at least partially gas-filled cells is formed in-situ; b.
producing an opening into said pad; c. inserting a spacer into said
opening; d. filling said opening above said spacer with a resin
material; and e. allowing said resin material to cure at a
temperature of from 0.degree. C. to less than 125.degree. C.
34. The method of claim 33 further comprising: f. removing said
spacer.
35. The method of claim 33 wherein said pad is the reaction product
of polyisocyanate, hydroxyl-containing material, amine-containing
material and blowing agent.
36. The method of claim 31 wherein said pad is the reaction product
of polyurethane prepolymer, amine-containing material and blowing
agent.
37. The method of claim 33 wherein said pad is the reaction product
of polyisocyanate and polyurethane prepolymer, optional
hydroxyl-containing material, amine-containing material and blowing
agent.
38. The method of claim 33 further comprising at least partially
connecting to said pad a sub-pad; producing an opening in said
sub-pad; and at least partially aligning said opening of said pad
and said opening of said sub-pad.
39. The method of claim 33 further comprising at least partially
connecting said pad to a second layer and at least partially
connecting said second layer to a sub-pad; producing an opening in
said second layer and said sub-pad; and at least partially aligning
said opening in said polishing pad, said opening in said second
layer and said opening in said sub-pad.
40. The method of claim 33 wherein said resin material is chosen
from polyurethane prepolymers with curative, epoxy resins with
curative, ultraviolet curable acrylics, and mixtures thereof.
41. The method of claim 33 wherein said window is at least
partially transparent to wavelengths in the range of from 190 to
3500 nanometers.
42. The method of claim 33 wherein in step d, an amount of resin is
used to fill said spacer such that said resin is flush with a
polishing surface of said pad.
43. The method of claim 31 wherein in step e said temperature for
cure is from 5.degree. C. to 120.degree. C.
44. The method of claim 31 wherein in step e said temperature for
cure is from 10.degree. C. to 115.degree. C.
45. The method of claim 31 wherein in step e said temperature for
cure is from 15.degree. C. to 110.degree. C.
46. The method of claim 31 wherein in step e said temperature for
cure is from 22.degree. C. to 105.degree. C.
47. A polishing pad having an at least partially transparent window
wherein formation of said window comprises forming a polishing pad
and a second layer, at least partially connecting said polishing
pad to said second layer; producing an opening into said polishing
pad and said second layer such that said opening in said polishing
pad is at least partially aligned with said opening in said second
layer; inserting a spacer into said opening; filling opening above
said spacer with a resin material; allowing said resin material to
cure at a temperature of from 0.degree. C. to less than 125.degree.
C., and removing said spacer.
Description
[0001] The present invention relates to an article for altering a
surface of a workpiece. In particular, the present invention is
directed to a polishing pad having a window. More particularly, the
polishing pad can include a polyurethane urea material wherein
cells at least partially filled with gas are substantially
uniformly distributed throughout the material and/or pad. The
polyurethane urea material can be prepared by combining
polyisocyanate and/or polyurethane prepolymer; hydroxyl-containing
material; amine-containing material and blowing agent. The
polishing pad according to the present invention is useful for
polishing articles, and is especially useful for chemical
mechanical polishing or planarization of microelectronic and
optical electronic devices such as but not limited to semiconductor
wafers. 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] The polishing or planarization of a rough surface of an
article such as a microelectronic device, to a substantially smooth
surface generally involves rubbing the rough surface with the work
surface of a polishing pad using a controlled and repetitive
motion. A polishing fluid 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 can comprise the
formation of a plurality of integrated circuits on a semiconductor
substrate. The composition of the substrate can include silicon or
gallium arsenide. The integrated circuits generally can be formed
by a series of process steps in which patterned layers of
materials, such as conductive, insulating and semi-conducting
materials, are formed on the substrate. In order to maximize the
density of integrated circuits per wafer, it is desirable to have a
planar polished substrate at various stages throughout the
production process. As such, production of a microelectronic device
typically involves at least one polishing step and can often
involve a plurality of polishing steps, which can result in the use
of more than one polishing pad.
[0004] The polishing step can include rotating the polishing pad
and the semiconductor substrate against each other in the presence
of a polishing fluid. The polishing fluid can be mildly alkaline
and can optionally contain an abrasive particulate material such as
but not limited to particulate cerium oxide, particulate alumina,
or particulate silica. The polishing fluid can facilitate the
removal and transport of abraded material off and away from the
rough surface of the article.
[0005] Polishing pad characteristics such as pore volume and pore
size can vary from pad-to-pad and throughout the operating lifetime
of a particular pad. Variations in the polishing characteristics of
the pads can result in inadequately polished and planarized
substrates which can be unsuitable for fabricating semiconductor
wafers. Thus, it is desirable to develop a polishing pad that
exhibits reduced pad-to-pad variation in polishing and
planarization characteristics. It is further desirable to develop a
polishing pad that exhibits reduced variations in polishing and
planarization characteristics throughout the operating lifetime of
the pad.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] The present invention includes a pad having an at least
partially transparent cast-in-place window adapted to polish a
microelectronic substrate. The pad of the present invention
comprises polyurethane urea material. At least a portion of the
polyurethane urea contains cells that are at least partially filled
with gas, and at least a portion of the at least partially
gas-filled cells is formed by an in-situ reaction.
[0012] In a non-limiting embodiment, the cells can be substantially
uniformly distributed throughout the material and/or pad. In
another non-limiting embodiment, the polyurethane urea can be
prepared by combining polyisocyanate, hydroxyl-containing material,
amine-containing material and blowing agent. In another
non-limiting embodiment, the polyurethane urea can be formed by
condensation polymerization of polyisocyanate functional
polyurethane prepolymer with polyamine and blowing agent. In a
further non-limiting embodiment, the polyurethane urea can be
formed by combining polyisocyanate and polyurethane prepolymer,
optional hydroxyl-containing material, amine-containing material
and blowing agent. In a non-limiting embodiment, at least a portion
of the pad can comprise a window which is at least partially
transparent to wavelengths used by the metrology instrumentation of
polishing tools.
[0013] In alternate non-limiting embodiments, the amount of
polyisocyanate, hydroxyl-containing material and amine-containing
material can be selected such that the equivalent ratio of
(NCO+NCS):(NH+OH) can be greater than 0.95, or at least 1.0, or at
least 1.05, or less than 1.3, or less than 1.2, or less than
1.1.
[0014] Polyisocyanates useful in the preparation of the
polyurethane urea of the present invention are numerous and widely
varied. Suitable polyisocyanates can include but are not limited to
polymeric and C.sub.2-C.sub.20 linear, branched, cyclic and
aromatic polyisocyanates. Non-limiting examples can include
polyisocyanates having backbone linkages chosen from urethane
linkages (--NH--C(O)--O--).
[0015] The molecular weight of the polyisocyanate can vary widely.
In alternate non-limiting embodiments, the number average molecular
weight (Mn) can be at least 100 grams/mole, or at least 150
grams/mole, or less than 15,000 grams/mole, or less than 5000
grams/mole. The number average molecular weight can be determined
using known methods. The number average molecular weight values
recited herein and the claims were determined by gel permeation
chromatography (GPC) using polystyrene standards.
[0016] Non-limiting examples of suitable polyisocyanates can
include but are not limited to polyisocyanates having at least two
isocyanate groups.
[0017] Non-limiting examples of polyisocyanates can include but are
not limited to aliphatic polyisocyanates, cycloaliphatic
polyisocyanates wherein one or more of the isocyanato groups are
attached directly to the cycloaliphatic ring, cycloaliphatic
polyisocyanates wherein one or more of the isocyanato groups are
not attached directly to the cycloaliphatic ring, aromatic
polyisocyanates wherein one or more of the isocyanato groups are
attached directly to the aromatic ring, and aromatic
polyisocyanates wherein one or more of the isocyanato groups are
not attached directly to the aromatic ring.
[0018] In a non-limiting embodiment of the present invention, the
polyisocyanate can include but is not limited to aliphatic or
cycloaliphatic diisocyanates, aromatic diisocyanates, cyclic dimers
and cyclic trimers thereof, and mixtures thereof. Non-limiting
examples of suitable polyisocyanates can include but are not
limited to Desmodur N 3300A (hexamethylene diisocyanate trimer)
which is commercially available from Bayer; Desmodur N 3400 (60%
hexamethylene diisocyanate dimer and 40% hexamethylene diisocyanate
trimer).
[0019] In a non-limiting embodiment, the polyisocyanate can include
dicyclohexylmethane diisocyanate and isomeric mixtures thereof. As
used herein and the claims, the term "isomeric mixtures" refers to
a mixture of the cis-cis, trans-trans, and cis-trans isomers of the
polyisocyanate. Non-limiting examples of isomeric mixtures for use
in the present invention can include the trans-trans isomer of
4,4''-methylenebis(cyclohexyl isocyanate), hereinafter referred to
as "PICM" (paraisocyanato cyclohexylmethane), the cis-trans isomer
of PICM, the cis-cis isomer of PICM, and mixtures thereof.
[0020] In one non-limiting embodiment, the PICM used in this
invention can be prepared by phosgenating the
4,4'-methylenebis(cyclohexyl amine) (PACM) by procedures well known
in the art such as the procedures disclosed in U.S. Pat. Nos.
2,644,007 and 2,680,127 which are incorporated herein by reference.
The PACM isomer mixtures, upon phosgenation, can produce PICM in a
liquid phase, a partially liquid phase, or a solid phase at room
temperature. The PACM isomer mixtures can be obtained by the
hydrogenation of methylenedianiline and/or by fractional
crystallization of PACM isomer mixtures in the presence of water
and alcohols such as methanol and ethanol.
[0021] In a non-limiting embodiment, the isomeric mixture can
contain from 10-100 percent of the trans,trans isomer of
4,4'-methylenebis(cyclohexyl isocyanate) (PICM).
[0022] In a non-limiting embodiment, the polyisocyanate can include
2,4-tolylene diisocyanate; 2,6-tolylene diisocyanate and mixtures
of these isomers ("TDI").
[0023] Additional aliphatic and cycloaliphatic diisocyanates that
can be used in alternate non-limiting embodiments of the present
invention include 3-isocyanato-methyl-3,5,5-trimethyl
cyclohexyl-isocyanate ("IPDI") which is commercially available from
Arco Chemical, and meta-tetramethylxylene diisocyanate
(1,3-bis(1-isocyanato-1-methylethyl)-benzene) which is commercially
available from Cytec Industries Inc. under the tradename TMXDI.RTM.
(Meta) Aliphatic Isocyanate.
[0024] As used herein and the claims, the terms aliphatic and
cycloaliphatic diisocyanates refer to 6 to 100 carbon atoms linked
in a straight chain or cyclized having two diisocyanate reactive
end groups. In a non-limiting embodiment of the present invention,
the aliphatic and cycloaliphatic diisocyanates for use in the
present invention can include TMXDI and compounds of the formula
R--(NCO).sub.2 wherein R represents an aliphatic group or a
cycloaliphatic group.
[0025] Further non-limiting examples of suitable polyisocyanates
can include but are not limited to aliphatic polyisocyanates;
ethylenically unsaturated polyisocyanates; alicyclic
polyisocyanates; aromatic polyisocyanates wherein the isocyanate
groups are not bonded directly to the aromatic ring, e.g.,
.alpha.,.alpha.'-xylene diisocyanate; aromatic polyisocyanates
wherein the isocyanate groups are bonded directly to the aromatic
ring, e.g., benzene diisocyanate;halogenated, alkylated,
alkoxylated, nitrated, carbodiimide-modified, urea-modified and
biuret-modified derivatives of polyisocyanates thereof; and
dimerized and trimerized products of polyisocyanates thereof.
[0026] Further non-limiting examples of aliphatic polyisocyanates
can include ethylene diisocyanate, trimethylene diisocyanate,
tetramethylene diisocyanate, hexamethylene diisocyanate,
octamethylene diisocyanate, nonamethylene diisocyanate,
2,2'-dimethylpentane diisocyanate, 2,2,4-trimethylhexane
diisocyanate, decamethylene diisocyanate,
2,4,4,-trimethylhexamethylene diisocyanate,
1,6,11-undecanetriisocyanate, 1,3,6-hexamethylene triisocyanate,
1,8-diisocyanato-4-(isocyanatomethyl)octane,
2,5,7-trimethyl-1,8-diisocyanato-5-(isocyanatomethyl)octane,
bis(isocyanatoethyl)-carbonate, bis(isocyanatoethyl)ether,
2-isocyanatopropyl-2,6-diisocyanatohexanoate, lysinediisocyanate
methyl ester and lysinetriisocyanate methyl ester.
[0027] Examples of ethylenically unsaturated polyisocyanates can
include but are not limited to butene diisocyanate and
1,3-butadiene-1,4-diisocyanate. Alicyclic polyisocyanates can
include but are not limited to isophorone diisocyanate, cyclohexane
diisocyanate, methylcyclohexane diisocyanate, bis(isocyanatomethyl)
cyclohexane, bis(isocyanatocyclohexyl)methane,
bis(isocyanatocyclohexyl)-2,2-propane,
bis(isocyanatocyclohexyl)-1,2-ethane,
2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.-
1]-heptane,
2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.-
1]-heptane,
2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.-
1]-heptane,
2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.-
1]-heptane,
2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2-
.2.1]-heptane,
2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2-
.2.1]-heptane and
2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2-
.2.1]-heptane.
[0028] Examples of aromatic polyisocyanates wherein the isocyanate
groups are not bonded directly to the aromatic ring can include but
are not limited to bis(isocyanatoethyl)benzene,
.alpha.,.alpha.,.alpha.',.alpha.'-tetramethylxylene diisocyanate,
1,3-bis(1-isocyanato-1-methylethyl)benzene,
bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene,
bis(isocyanatomethyl)diphenyl ether, bis(isocyanatoethyl)
phthalate, mesitylene triisocyanate and
2,5-di(isocyanatomethyl)furan. Aromatic polyisocyanates having
isocyanate groups bonded directly to the aromatic ring can include
but are not limited to phenylene diisocyanate, ethylphenylene
diisocyanate, isopropylphenylene diisocyanate, dimethylphenylene
diisocyanate, diethylphenylene diisocyanate, diisopropylphenylene
diisocyanate, trimethylbenzene triisocyanate, benzene
triisocyanate, naphthalene diisocyanate, methylnaphthalene
diisocyanate, biphenyl diisocyanate, ortho-toluidine diisocyanate,
ortho-tolylidine diisocyanate, ortho-tolylene diisocyanate,
4,4'-diphenylmethane diisocyanate,
bis(3-methyl-4-isocyanatophenyl)methane,
bis(isocyanatophenyl)ethylene,
3,3'-dimethoxy-biphenyl-4,4'-diisocyanate, triphenylmethane
triisocyanate, polymeric 4,4'-diphenylmethane diisocyanate,
naphthalene triisocyanate, diphenylmethane-2,4,4'-triisocyanate,
4-methyldiphenylmethane-3,5,2',4',6'-pentaisocyanate, diphenylether
diisocyanate, bis(isocyanatophenylether)ethyleneglycol,
bis(isocyanatophenylether)-1,3-propyleneglycol, benzophenone
diisocyanate, carbazole diisocyanate, ethylcarbazole diisocyanate
and dichlorocarbazole diisocyanate.
[0029] In alternate non-limiting embodiments of the present
invention, polyisothiocyanate or a combination of polyisocyanate
and polyisothiocyanate can be used in place of polyisocyanate. In
these alternate non-limiting embodiments, isothiocyanate can have
at least two isothiocyanate groups.
[0030] In a non-limiting embodiment of the present invention, the
polyisocyanate for use in the present invention can include
polyurethane prepolymer.
[0031] In a non-limiting embodiment, polyisocyanate can be reacted
with hydroxyl-containing material to form polyurethane prepolymer.
Hydroxyl-containing materials are varied and known in the art.
Non-limiting examples can include but are not limited to polyols;
sulfur-containing materials such as but not limited to hydroxyl
functional polysulfides, and SH-containing materials such as but
not limited to polythiols; and materials having both hydroxyl and
thiol functional groups.
[0032] Suitable hydroxyl-containing materials for use in the
present invention can include a wide variety of materials known in
the art. Non-limiting examples can include but are not limited to
polyether polyols, polyester polyols, polycaprolactone polyols,
polycarbonate polyols, and mixtures thereof.
[0033] Polyether polyols and methods for their preparation are
known to one skilled in the art. Many polyether polyols of various
types and molecular weight are commercially available from various
manufacturers. Non-limiting examples of polyether polyols can
include but are not limited to polyoxyalkylene polyols, and
polyalkoxylated polyols. Polyoxyalkylene polyols can be prepared in
accordance with known methods. In a non-limiting embodiment, a
polyoxyalkylene polyol can be prepared by condensing an alkylene
oxide, or a mixture of alkylene oxides, using acid- or
base-catalyzed addition with a polyhydric initiator or a mixture of
polyhydric initiators, such as but not limited to ethylene glycol,
propylene glycol, glycerol, and sorbitol. Non-limiting examples of
alkylene oxides can include ethylene oxide, propylene oxide,
butylene oxide, amylene oxide, aralkylene oxides, such as but not
limited to styrene oxide, mixtures of ethylene oxide and propylene
oxide. In a further non-limiting embodiment, polyoxyalkylene
polyols can be prepared with mixtures of alkylene oxide using
random or step-wise oxyalkylation. Non-limiting examples of such
polyoxyalkylene polyols include polyoxyethylene, such as but not
limited to polyethylene glycol, polyoxypropylene, such as but not
limited to polypropylene glycol.
[0034] In a non-limiting embodiment, polyalkoxylated polyols can be
represent by the following general formula: ##STR1## wherein m and
n can each be a positive integer, the sum of m and n being from 5
to 70; R.sub.1 and R.sub.2 are each hydrogen, methyl or ethyl; and
A is a divalent linking group such as a straight or branched chain
alkylene which can contain from 1 to 8 carbon atoms, phenylene, and
C.sub.1 to C.sub.9 alkyl-substituted phenylene. The chosen values
of m and n can, in combination with the chosen divalent linking
group, determine the molecular weight of the polyol.
[0035] Polyalkoxylated polyols can be prepared by methods that are
known in the art. In a non-limiting embodiment, a polyol such as
4,4'-isopropylidenediphenol can be reacted with an
oxirane-containing material such as but not limited to ethylene
oxide, propylene oxide and butylene oxide, to form what is commonly
referred to as an ethoxylated, propoxylated or butoxylated polyol
having hydroxy functionality. Non-limiting examples of polyols
suitable for use in preparing polyalkoxylate polyols can include
those polyols described in U.S. Pat. No. 6,187,444 B1 at column 10,
lines 1-20, which disclosure is incorporated herein by
reference.
[0036] As used herein and the claims, the term "polyether polyols"
can include the generally known poly(oxytetramethylene) diols
prepared by the polymerization of tetrahydrofuran in the presence
of Lewis acid catalysts such as but not limited to boron
trifluoride, tin (IV) chloride and sulfonyl chloride. In a
non-limiting embodiment, the polyether polyol can include
Terathane.TM. which is commercially available from DuPont. Also
included are the polyethers prepared by the copolymerization of
cyclic ethers such as but not limited to ethylene oxide, propylene
oxide, trimethylene oxide, and tetrahydrofuran with aliphatic diols
such as but not limited to ethylene glycol, 1,3-butanediol,
1,4-butanediol, diethylene glycol, dipropylene glycol,
1,2-propylene glycol and 1,3-propylene glycol. Compatible mixtures
of polyether polyols can also be used. As used herein, "compatible"
means that the polyols are mutually soluble in each other so as to
form a single phase.
[0037] A wide variety of polyester polyols known in the art can be
used in the present invention. Suitable polyester polyols can
include but are not limited to polyester glycols. Polyester glycols
for use in the present invention can include the esterification
products of one or more dicarboxylic acids having from four to ten
carbon atoms, such as but not limited to adipic, succinic or
sebacic acids, with one or more low molecular weight glycols having
from two to ten carbon atoms, such as but not limited to ethylene
glycol, propylene glycol, diethylene glycol, 1,4-butanediol,
neopentyl glycol, 1,6-hexanediol and 1,10-decanediol.
Esterification procedures for producing polyester polyols is
described, for example, in the article D. M. Young, F. Hostettler
et al., "Polyesters from Lactone," Union Carbide F-40, p. 147.
[0038] In a non-limiting embodiment, the polyol for use in the
present invention can include polycaprolactone polyols. Suitable
polycaprolactone polyols are varied and known in the art. In a
non-limiting embodiment, polycaprolactone polyols can be prepared
by condensing caprolactone in the presence of difunctional active
hydrogen compounds such as but not limited to water or low
molecular weight glycols as recited herein. Non-limiting examples
of suitable polycaprolactone polyols can include commercially
available materials designated as the CAPA series from Solvay
Chemical which includes but is not limited to CAPA 2047A, and the
TONE.TM. series from Dow Chemical such as but not limited to TONE
0201.
[0039] Polycarbonate polyols for use in the present invention are
varied and known to one skilled in the art. Suitable polycarbonate
polyols can include those commercially available (such as but not
limited to Ravecarb.TM. 107 from Enichem S. p. A.). In a
non-limiting embodiment, the polycarbonate polyol can be produced
by reacting an organic glycol such as a diol, described hereinafter
and in connection with the glycol component of the polyurethane or
polyurethane urea, and a dialkyl carbonate, such as described in
U.S. Pat. No. 4,160,853. In a non-limiting embodiment, the polyol
can include polyhexamethyl carbonate such as
HO--(CH.sub.2).sub.6--[O--C(O)--O--(CH.sub.2).sub.6].sub.n--OH,
wherein n is an integer from 4 to 24, or from 4 to 10, or from 5 to
7.
[0040] In a non-limiting embodiment, the glycol material can
comprise low molecular weight polyols such as polyols having a
number average molecular weight of less than 500 grams/mole, and
compatible mixtures thereof. As used herein, the term "compatible"
means that the glycols are mutually soluble in each other so as to
form a single phase. Non-limiting examples of these polyols can
include but are not limited to low molecular weight diols and
triols. In a further non-limiting embodiment, the amount of triol
chosen can be such to avoid a high degree of cross-linking in the
polyurethane or polyurethane urea. In alternate non-limiting
embodiments, the organic glycol can contain from 2 to 16, or from 2
to 6, or from 2 to 10, carbon atoms. Non-limiting examples of such
glycols can include but are not limited to ethylene glycol,
propylene glycol, diethylene glycol, triethylene glycol,
tetraethylene glycol, dipropylene glycol, tripropylene glycol,
1,2-, 1,3- and 1,4-butanediol, 2,2,4-trimethyl-1,3-pentanediol,
2-methyl-1,3-pentanediol, 1,3- 2,4- and 1,5-pentanediol, 2,5- and
1,6-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol,
2,2-dimethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol,
1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol,
1,2-bis(hydroxyethyl)-cyclohexane, glycerin, tetramethylolmethane,
pentaerythritol, trimethylolethane and trimethylolpropane; and
isomers thereof.
[0041] In alternate non-limiting embodiments, the
hydroxyl-containing material can have a molecular weight of at
least 200 grams/mole, or at least 1000 grams/mole, or at least 2000
grams/mole. In alternate non-limiting embodiments, the
hydroxyl-containing material can have a number average molecular
weight of less than 10,000 grams/mole, or less than 15,000
grams/mole, or less than 20,000 grams/mole, or less than 32,000
grams/mole.
[0042] In a non-limiting embodiment, the hydroxyl-containing
material for use in the present invention can include teresters
produced from at least one low molecular weight dicarboxylic acid,
such as adipic acid.
[0043] In a non-limiting embodiment, the hydroxyl-containing
material can comprise block polymers including blocks of ethylene
oxide-propylene oxide and/or ethylene oxide-butylene oxide. In a
non-limiting embodiment, the hydroxyl-containing material can
comprise a block polymer of the following chemical formula:
HO--(O--CRRCRR--Y.sub.n).sub.a--(CRRCRR--Y.sub.n--O).sub.b--(CRRCRR--Y.su-
b.n--O).sub.c--H (II) wherein R can represent hydrogen or
C.sub.1-C.sub.6 alkyl; Y.sub.n can represent C.sub.0-C.sub.6
hydrocarbon; n can be an integer from 0 to 6; a, b, and c can each
be an integer from 0 to 300, wherein a, b and c are chosen such
that the number average molecular weight of the polyol does not
exceed 32,000 grams/mole.
[0044] In further alternate non-limiting embodiments,
hydroxyl-containing materials such as but not limited to
Pluronic.RTM R, Pluronic.RTM, Tetronic.RTM R and Tetronic.RTM Block
Copolymer Surfactants, which are commercially available from BASF,
can be used as the hydroxyl-containing material in the present
invention.
[0045] Further non-limiting examples of suitable polyols for use in
the present invention can include straight or branched chain alkane
polyols, such as but not limited to 1,2-ethanediol,
1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol,
glycerol, neopentyl glycol, trimethylolethane, trimethylolpropane,
di-trimethylolpropane, erythritol, pentaerythritol and
di-pentaerythritol; polyalkylene glycols, such as but not limited
to diethylene glycol, dipropylene glycol and higher polyalkylene
glycols such as but not limited to polyethylene glycols which can
have number average molecular weights of from 200 grams/mole to
2,000 grams/mole; cyclic alkane polyols, such as but not limited to
cyclopentanediol, cyclohexanediol, cyclohexanetriol,
cyclohexanedimethanol, hydroxypropylcyclohexanol and
cyclohexanediethanol; aromatic polyols, such as but not limited to
dihydroxybenzene, benzenetriol, hydroxybenzyl alcohol and
dihydroxytoluene; bisphenols, such as, 4,4'-isopropylidenediphenol;
4,4'-oxybisphenol, 4,4'-dihydroxybenzophenone, 4,4'-thiobisphenol,
phenolphthlalein, bis(4-hydroxyphenyl)methane,
4,4'-(1,2-ethenediyl)bisphenol and 4,4'-sulfonylbisphenol;
halogenated bisphenols, such as but not limited to
4,4'-isopropylidenebis(2,6-dibromophenol),
4,4'-isopropylidenebis(2,6-dichlorophenol) and
4,4'-isopropylidenebis(2,3,5,6-tetrachlorophenol); alkoxylated
bisphenols, such as but not limited to alkoxylated
4,4'-isopropylidenediphenol which can have from 1 to 70 alkoxy
groups, for example, ethoxy, propoxy, .alpha.-butoxy and
.beta.-butoxy groups; and biscyclohexanols, which can be prepared
by hydrogenating the corresponding bisphenols, such as but not
limited to 4,4'-isopropylidene-biscyclohexanol,
4,4'-oxybiscyclohexanol, 4,4'-thiobiscyclohexanol and
bis(4-hydroxycyclohexanol)methane; polyurethane or polyurethane
urea polyols, polyester polyols, polyether polyols, poly vinyl
alcohols, polymers containing hydroxy functional acrylates,
polymers containing hydroxy functional methacrylates, and polymers
containing allyl alcohols.
[0046] In a non-limiting embodiment, the polyol can be chosen from
multifunctional polyols, including but not limited to
trimethylolpropane, ethoxylated trimethylolpropane,
pentaerythritol.
[0047] In alternate non-limiting embodiments, the polyurethane
prepolymer can have a number average molecular weight (Mn) of less
than 50,000 grams/mole, or less than 20,000 grams/mole, or less
than 10,000 grams/mole. The Mn can be determined using a variety of
known methods. In a non-limiting embodiment, the Mn can be
determined by gel permeation chromatography (GPC) using polystyrene
standards.
[0048] In alternate non-limiting embodiments, the
hydroxyl-containing material for use in the present invention can
be chosen from polyether glycols and polyester glycols having a
number average molecular weight of at least 200 grams/mole, or at
least 300 grams/mole, or at least 750 grams/mole; or no greater
than 1,500 grams/mole, or no greater than 2,500 grams/mole, or no
greater than 4,000 grams/mole.
[0049] In a further non-limiting embodiment, polyether glycols for
use in the present invention can include but are not limited to
polytetramethylene ether glycol.
[0050] In a non-limiting embodiment, the hydroxyl-containing
material can include both hydroxyl and thiol groups, such as but
not limited to 2-mercaptoethanol, 3-mercapto-1,2-propanediol,
glycerin bis(2-mercaptoacetate) and
1-hydroxy-4-mercaptocyclohexane.
[0051] In general, polyurethanes and polyurethane prepolymers can
be polymerized using a variety of techniques known in the art. In a
non-limiting embodiment of the present invention, the
polymerization process can include the use of an amine-containing
material for curing.
[0052] Amine-containing curing agents for use in the present
invention are numerous and widely varied. Non-limiting examples of
suitable amine-containing curing agents can include but are not
limited to aliphatic polyamines, cycloaliphatic polyamines,
aromatic polyamines and mixtures thereof. In alternate non-limiting
embodiments, the amine-containing curing agent can be a polyamine
having at least two functional groups independently chosen from
primary amine (--NH.sub.2), secondary amine (--NH--) and
combinations thereof. In a further non-limiting embodiment, the
amine-containing curing agent can have at least two primary amine
groups. In another non-limiting embodiment, the amine-containing
curing agent can comprise a mixture of a polyamine and at least one
material selected from a polythiol and polyol. Non-limiting
examples of suitable polythiols and polyols include those
previously recited herein. In still another non-limiting
embodiment, the amine-containing curing agent can be a
sulfur-containing amine-containing curing agent. A non-limiting
example of a sulfur-containing amine-containing curing agent can
include Ethacure 300 which is commercially available from Albemarle
Corporation.
[0053] Suitable amine-containing curing agents for use in the
present invention can include but are not limited to materials
having the following chemical formula: ##STR2## wherein R.sub.1 and
R.sub.2 can each be independently chosen from methyl, ethyl,
propyl, and isopropyl groups, and R.sub.3 can be chosen from
hydrogen and chlorine. Non-limiting examples of amine-containing
curing agents for use in the present invention include the
following compounds, manufactured by Lonza Ltd. (Basel,
Switzerland): [0054] LONZACURE.RTM. M-DIPA:
R.sub.1.dbd.C.sub.3H.sub.7; R.sub.2.dbd.C.sub.3H.sub.7;
R.sub.3.dbd.H [0055] LONZACURE.RTM. M-DMA: R.sub.1.dbd.CH.sub.3;
R.sub.2.dbd.CH.sub.3; R.sub.3.dbd.H [0056] LONZACURE.RTM. M-MEA:
R.sub.1.dbd.CH.sub.3; R.sub.2.dbd.C.sub.2H.sub.5; R.sub.3.dbd.H
[0057] LONZACURE.RTM. M-DEA: R.sub.1.dbd.C.sub.2H.sub.5;
R.sub.2.dbd.C.sub.2H.sub.5; R.sub.3.dbd.H [0058] LONZACURE.RTM.
M-MIPA: R.sub.1.dbd.CH.sub.3; R.sub.2.dbd.C.sub.3H.sub.7;
R.sub.3.dbd.H [0059] LONZACURE.RTM. M-CDEA:
R.sub.1.dbd.C.sub.2H.sub.5; R.sub.2.dbd.C.sub.2H.sub.5;
R.sub.3.dbd.Cl wherein R.sub.1, R.sub.2 and R.sub.3 correspond to
the aforementioned chemical formula.
[0060] In a non-limiting embodiment, the amine-containing curing
agent can include but is not limited to a diamine curing agent such
as 4,4'-methylenebis(3-chloro-2,6-diethylaniline), (Lonzacure.RTM.
M-CDEA), which is available in the United States from Air Products
and Chemical, Inc. (Allentown, Pa.). In alternate non-limiting
embodiments, the amine-containing curing agent for use in the
present invention can include 2,4-diamino-3,5-diethyl-toluene,
2,6-diamino-3,5-diethyl-toluene and mixtures thereof (collectively
"diethyltoluenediamine" or "DETDA"), which is commercially
available from Albemarle Corporation under the trade name Ethacure
100; dimethylthiotoluenediamine (DMTDA) , which is commercially
available from Albemarle Corporation under the trade name Ethacure
300; 4,4'-methylene-bis-(2-chloroaniline) which is commercially
available from Kingyorker Chemicals under the trade name MOCA.
DETDA can be a liquid at room temperature with a viscosity of 156
cPs at 25.degree. C. DETDA can be isomeric, with the 2,4-isomer
range being from 75 to 81 percent while the 2,6-isomer range can be
from 18 to 24 percent.
[0061] Non-limiting examples of amine-containing curing agents can
include ethyleneamines. Suitable ethyleneamines can include but are
not limited to ethylenediamine (EDA), diethylenetriamine (DETA),
triethylenetetramine (TETA), tetraethylenepentamine (TEPA),
pentaethylenehexamine (PEHA), piperazine, morpholine, substituted
morpholine, piperidine, substituted piperidine, diethylenediamine
(DEDA), and 2-amino-1-ethylpiperazine. In alternate non-limiting
embodiments, the amine-containing curing agent can be chosen from
one or more isomers of C.sub.1-C.sub.3 dialkyl toluenediamine, such
as but not limited to 3,5-dimethyl-2,4-toluenediamine,
3,5-dimethyl-2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine,
3,5-diethyl-2,6-toluenediamine, 3,5-diisopropyl-2,4-toluenediamine,
3,5-diisopropyl-2,6-toluenediamine, and mixtures thereof. In
alternate non-limiting embodiments, the amine-containing curing
agent can be methylene dianiline or trimethyleneglycol
di(para-aminobenzoate).
[0062] In alternate non-limiting embodiments of the present
invention, the amine-containing curing agent can include one of the
following general structures: ##STR3##
[0063] In further alternate non-limiting embodiments, the
amine-containing curing agent can include one or more methylene bis
anilines which can be represented by the general formulas VII-XI,
one or more aniline sulfides which can be represented by the
general formulas XII-XVI, and/or one or more bianilines which can
be represented by the general formulas XVII-XX, ##STR4## ##STR5##
wherein R.sub.3 and R.sub.4 can each independently represent
C.sub.1 to C.sub.3 alkyl, and R.sub.5 can be chosen from hydrogen
and halogen, such as but not limited to chlorine and bromine. The
diamine represented by general formula VII can be described
generally as a 4,4'-methylene-bis(dialkylaniline). Suitable
non-limiting examples of diamines which can be represented by
general formula VII include but are not limited to
4,4'-methylene-bis(2,6-dimethylaniline),
4,4'-methylene-bis(2,6-diethylaniline),
4,4'-methylene-bis(2-ethyl-6-methylaniline),
4,4'-methylene-bis(2,6-diisopropylaniline),
4,4'-methylene-bis(2-isopropyl-6-methylaniline) and
4,4'-methylene-bis(2,6-diethyl-3-chloroaniline).
[0064] In a further non-limiting embodiment, the amine-containing
curing agent can include materials which can be represented by the
following general structure (XXI): ##STR6##
[0065] where R.sub.20, R.sub.21, R.sub.22, and R.sub.23 can be
independently chosen from H, C.sub.1 to C.sub.3 alkyl, CH.sub.3-S-
and halogen, such as but not limited to chlorine or bromine. In a
non-limiting embodiment of the present invention, the
amine-containing curing agent which can be represented by general
Formula XXI can include diethyl toluene diamine (DETDA) wherein
R.sub.23 is methyl, R.sub.20 and R.sub.21 are each ethyl and
R.sub.22 is hydrogen. In a further non-limiting embodiment, the
amine-containing curing agent can include
4,4'-methylenedianiline.
[0066] In alternate non-limiting embodiments, amine-containing
material and blowing agent can be mixed with the polyisocyanate and
hydroxyl-containing materials using a variety of methods and
equipment, such as but not limited to an impeller or extruder. In a
non-limiting embodiment, the mixing equipment can include a
mechanical stirrer operating at low pressure such as less than 20
bar. In another non-limiting embodiment, the components can be
mixed by impingement mixing wherein the components are injected at
high velocity and pressure into a mixing chamber, and the
components are then mixed in the chamber by kinetic energy. In this
embodiment, the components are typically injected at a velocity of
from 100 to 200 meters per second, and a pressure of from 20 to
3000 bar.
[0067] In alternate non-limiting embodiments, polyurethane
prepolymer and optionally polyisocyanate can be contained in a
first feed of a mixing unit, amine-containing material and
optionally hydroxyl-containing material in a second feed and the
blowing agent in a third feed; or the second feed can include
amine-containing material and blowing agent, and optionally
hydroxyl-containing material.
[0068] In another non-limiting embodiment, the polyurethane urea
can be prepared by a one-pot process by combining polyisocyanate,
hydroxyl-containing material, amine-containing material and blowing
agent. In a further non-limiting embodiment, the polyurethane urea
can be prepared by a one-pot process by combining polyisocyanate
and polyurethane prepolymer, optionally hydroxyl-containing
material, amine-containing material and blowing agent.
[0069] In a non-limiting embodiment of the present invention, a
mixing unit having three feeds can be used in combining the
polyisocyanate and/or polyurethane, hydroxyl-containing material,
amine-containing material and blowing agent. The ingredients can be
added into the feeds using a variety of configurations. In
alternate non-limiting embodiments, the first feed of a mixing unit
can contain polyisocyanate and/or polyurethane prepolymer and the
second feed can contain hydroxyl-containing material,
amine-containing material and blowing agent; or the second feed can
contain hydroxyl functional material and amine-containing material,
and a third feed can contain blowing agent; or the second feed can
contain amine-containing material, and the third feed can contain
hydroxyl-containing material and blowing agent; or the second feed
can contain hydroxyl-containing material, and the third feed can
contain amine-containing material and blowing agent. In a further
non-limiting embodiment, wherein polyurethane prepolymer is present
in a first feed, the presence of hydroxyl-containing material in
another feed is optional.
[0070] A blowing agent can be used in the present invention to form
cells at least partially filled with gas within the polyurethane
urea material. In a non-limiting embodiment, the cells are
substantially uniformly distributed throughout the polyurethane
urea material. The size of the cells can vary widely. In alternate
non-limiting embodiments, a cell can be from at least 1 micron, or
at least 20 microns, or at least 30 microns, or at least 40
microns; to less than 1000 microns, or less than 500 microns or
less than 100 microns.
[0071] In a non-limiting embodiment, the blowing agent can be
water. The water can react in-situ with isocyanate (NCO) to produce
carbon dioxide. In a further non-limiting embodiment, one or more
auxiliary blowing agents can be used in combination with the
blowing agent. Suitable auxiliary blowing agents for use in the
present invention can vary widely and can include substances which
can be substantially volatile at the reaction temperature. The
auxiliary blowing agent can be selected from those known in the
art. Non-limiting examples can include but are not limited to
acetone, ethyl acetate, halogen substituted alkanes such as
methylene chloride, chloroform, ethylidene chloride, vinylidene
chloride, monofluorotrichloromethane, chlorodifluoromethane,
dichlorodifluoromethane, dichloromonofluoromethane, butane,
pentane, cyclopentane hexane, heptane, diethylether, and mixtures
thereof.
[0072] The amount of blowing agent used in the present invention
can vary. In alternate non-limiting embodiments, the blowing agent
can be present in an amount such that a selected or desired density
and/or pore volume of the polishing pad can be achieved. In
alternate non-limiting embodiments, the density can be from 0.50 to
1.10 g/cc; the pore volume can be from 5% to 55% based on volume of
polyurethane urea material. Density can be measured using a variety
of methods known to one of ordinary skill in the art. The density
values recited herein are determined in accordance with ASTM
1622-88. Pore volume can also be measured using a variety of
methods known to a skilled artisan. The pore volume values recited
herein are determined in accordance with ASTM D 4284-88, using an
Autopore III mercury porosimeter manufactured by Micromeritics. In
a further non-limiting embodiment, the amount of blowing agent can
be from 0 to 5% by weight of the reaction mixture.
[0073] In a non-limiting embodiment, the amine-containing material
can contain at least a small concentration of residual moisture or
water sufficient to act as the blowing agent.
[0074] In another non-limiting embodiment, a urethane-forming
catalyst and/or blowing catalyst can be used in the present
invention to enhance the reaction of the polyurethane urea-forming
materials, and/or accelerate the reaction with blowing agent. In a
further non-limiting embodiment, one or more materials can be used
wherein each material can exhibit characteristics of a
urethane-forming and blowing catalyst.
[0075] Suitable urethane-forming catalysts can vary, for example,
suitable urethane-forming catalysts can include those catalysts
that are known in the art to be useful for the formation of
urethane by reaction of the NCO and OH-containing materials.
Non-limiting examples of suitable catalysts can be chosen from the
group of Lewis bases, Lewis acids and insertion catalysts as
described in Ullmann's Encyclopedia of Industrial Chemistry,
5.sup.th Edition, 1992, Volume A21, pp. 673 to 674. In a
non-limiting embodiment, the catalyst can be a stannous salt of an
organic acid, such as but not limited to stannous octoate, dibutyl
tin dilaurate, dibutyl tin diacetate, dibutyl tin mercaptide,
dibutyl tin dimaleate, dimethyl tin diacetate, dimethyl tin
dilaurate, and mixtures thereof. In alternate non-limiting
embodiments, the catalyst can be zinc octoate, bismuth, or ferric
acetylacetonate.
[0076] Non-limiting examples of suitable blowing catalysts can
include tertiary amines such as but not limited to
1,4-diazabicyclo[2.2.2]octane, bis-2-dimethyl aminoethyl ether,
pentamethyldiethylene triamine, triethylamine, triisopropylamine,
N-methylmorpholine and N,N-dimethylbenzylamine. Such suitable
tertiary amines are disclosed in U.S. Pat. No. 5,693,738 at column
10, lines 6-38, the disclosure of which is incorporated herein by
reference. Tertiary amine catalysts may also include those
containing hydroxyl functionality such as N,N-dimethylethanolamine,
2-(2-dimethylaminoethoxy-)ethanol,
N,N,N'-trimethyl-N'-hydroxyethyl-bisaminoether,
N,N-(dimethyl)-N,N'-diisopropanol-1,3-propanediamine, and
N,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine.
[0077] In a non-limiting embodiment the catalyst can be chosen from
phosphines, tertiary ammonium salts and tertiary amines, such as
but not limited to tributyl phosphine, triethylamine;
triisopropylamine and N,N-dimethylbenzylamine. Additional
non-limiting examples of suitable tertiary amines are disclosed in
U.S. Pat. No. 5,693,738 at column 10 lines 6 through 38, the
disclosure of which is incorporated herein by reference.
[0078] In another non-limiting embodiment, a surfactant can be
present during polymerization. Surfactants can influence the
formation and stabilization of the at least partially gas-filled
cells. In a non-limiting embodiment, the surfactant can be selected
such that it has high surface activity for nucleation and
stabilization of the cells. In another non-limiting embodiment, the
surfactant can be selected such that it has good emulsifying
abilities for a blowing agent. Suitable surfactants for use in the
present invention are wide and varied. In a non-limiting
embodiment, a silicone surfactant can be used. The silicone
surfactant can be selected from siloxane-polyoxyalkylene copolymer
surfactants. Non-limiting examples of such surfactants can include
but are not limited to polydimethylsiloxane-polyoxyalkylene block
copolymers which are available from GE Silicons Incorporated under
the designations Niax RTM. Silicone L-1800, L-5420 and L-5340; Dow
Corning Corporation under the designations DC-193, DC-5357 and
DC-5315; and Goldschmidt Chemical Corporation under the
designations B-8404 and B-8407.
[0079] In a further non-limiting embodiment, the
siloxane-polyoxyalkylene copolymer surfactant can be represented by
the following general formula, ##STR7## (XXII)
[0080] wherein x is a number from 1 to 150, y is a number of from 1
to 50, the ratio of x:y is from 10:1 to 1:1 and R is an alkyl
alkoxylate. With reference to the general formula I, x can be from
10 to 50, or from 10 to 42, or from 13 to 42; and y can be from 2
to 20, or from 5 to 20, or from 7 to 20, or from 7 to 10. The ratio
of x:y can be between 2.4 and 6.8.
[0081] wherein R can be an alkyl alkoxylate which can be
represented by the following general formula XXIII,
R'O(C.sub.2H.sub.4O).sub.m(C.sub.3H.sub.6O).sub.nH (XXIII)
[0082] wherein R' is an alkylene group containing from 3 to 6
carbon atoms, m is a number of from 5 to 200, and n is a number of
from 0 to 20, or from 2 to 18. The molecular weight of R is in the
range of from 400 to 4000, and the molecular weight of the
surfactant represented by general formula XXII can be from 6,000 to
50,000.
[0083] The siloxane-polyoxyalkylene copolymer surfactant can be
prepared as described in U.S. Pat. No. 5,691,392, column 3, line 25
through column 4, line 18, which is incorporated herein by
reference.
[0084] The amount of surfactant useful in the present invention can
vary widely. In alternate non-limiting embodiments, the amount is
such that the surfactant is from 0.001% to 10%, or 0.01% to 1%, or
from 0.05% to 0.5% by weight of the reaction mixture.
[0085] In another non-limiting embodiment, a nucleating agent can
be used during polymerization in preparing the polyurethane urea of
the present invention. Suitable nucleating agents for use in the
present invention can include materials which enhance the
generation of relatively small substantially uniform cells. The
nucleating agent can be selected from those known in the art.
Non-limiting examples can include but are not limited to relatively
small size polymer particles (e.g., ten microns or less) such as
but not limited to polypropylene, polyethylene, polystyrene,
polyurethane, polyester, and polyacrylates. The amount of
nucleating agent used can vary widely. In general, the nucleating
agent can be used in an amount which is effective to generate said
cells. In alternate non-limiting embodiments, the nucleating agent
can be present in an amount of from 0.01% to 1.00%, or from 0.05%
to 0.5%, by weight of the reaction mixture.
[0086] In a non-limiting embodiment, feeds containing
polyisocyanate and/or polyurethane prepolymer, hydroxyl-containing
material, amine-containing material, blowing agent and any optional
additives can be directed into a mixing unit. Optional additives
can include a wide variety of additives known to one having
ordinary skill in the art. Non-limiting examples can include but
are not limited to antioxidants, hindered amine UV stabilizers, UV
absorbers, plasticizers, internal mold release agents, dyes and
pigments. In further alternate non-limiting embodiments, any or all
of the feeds can be heated to reduce the viscosity of the feeds
and/or the resulting mixture. The reaction mixture exiting the
mixing unit can then be poured into an open cavity to form a
polishing pad. In a non-limiting embodiment, the cavity can be
controlled to a temperature of from 22.degree. C. to 150.degree.
C., or from 60.degree. C. to 110.degree. C.
[0087] The polishing pad of the present invention can have one or
more work surfaces, wherein "work surface" as used herein and the
claims refers to a surface of the pad that can come into contact
with the surface of the article that is to be polished and a
polishing slurry. In a non-limiting embodiment, the article to be
polished can be a silicon wafer. In further non-limiting
embodiments, the work surface of the polishing pad can have surface
features such as but not limited to channels, grooves, perforations
and combinations thereof.
[0088] Surface features can be incorporated into the work surface
of the polishing pad by means that are known to those of ordinary
skill in the art. In a non-limiting embodiment, the work surface of
the pad can be mechanically modified, for example, by abrading or
cutting. In another non-limiting embodiment, surface features can
be incorporated into the work surface of the pad during the molding
process, for example, by providing at least one interior surface of
the mold with raised features that can be imprinted into the work
surface of the pad during its formation. Surface features can be
distributed in the form of random or uniform patterns across the
work surface of the polishing pad. Non-limiting examples of surface
feature patterns can include but are not limited to spirals,
circles, squares, cross-hatches and waffle-like patterns.
[0089] In a non-limiting embodiment, the polyurethane urea can
comprise an abrasive particulate material. The abrasive particulate
material can be distributed substantially uniformly or
non-uniformly throughout the polyurethane urea. In alternate
non-limiting embodiments, the abrasive particulate material can be
present in an amount of less than 70 percent by weight, or at least
5 percent by weight, or from 5 percent to 65 percent by weight,
based on the total weight of the polishing pad.
[0090] In alternate non-limiting embodiments, the abrasive
particulate material can be in the form of individual particles,
aggregates of individual particles, or a combination of individual
particles and aggregates. In further alternate non-limiting
embodiments, the shape of the abrasive particulate material can
include but is not limited to spheres, rods, triangles, pyramids,
cones, regular cubes, irregular cubes, and mixtures and/or
combinations thereof.
[0091] In general, the average particle size of the abrasive
particulate material can vary widely. In alternate non-limiting
embodiments, the average particle size can be at least 0.001
micron, or at least 0.01 micron, or at least 0.1 micron. In further
alternate non-limiting embodiments, the average particle size of
the abrasive particulate material can be less than 50 microns, or
less than 10 microns, or less than 1 micron. In a non-limiting
embodiment, the average particle size of the abrasive particulate
material can measured along the longest dimension of the
particle.
[0092] Non-limiting examples of suitable abrasive particulate
materials for use in the present invention can include aluminum
oxide, such as but not limited to gamma alumina, fused aluminum
oxide, heat treated aluminum oxide, white fused aluminum oxide, and
sol gel derived alumina; silicon carbide, such as but not limited
to green silicon carbide and black silicon carbide; titanium
diboride; boron carbide; silicon nitride; tungsten carbide;
titanium carbide; diamond; boron nitride, such as but not limited
to cubic boron nitride and hexagonal boron nitride; garnet; fused
alumina zirconia; silica, such as but not limited to fumed silica;
iron oxide; cromia; ceria; zirconia; titania; tin oxide; manganese
oxide; and mixtures thereof. In a further non-limiting embodiment,
the abrasive particulate material can be chosen from aluminum
oxide, silica, cerium oxide, zirconia and mixtures thereof.
[0093] In a non-limiting embodiment, the abrasive particulate
material used in the present invention can have a surface modifier
thereon. Non-limiting examples of suitable surface modifiers can
include surfactants, coupling agents and mixtures thereof. In a
non-limiting embodiment, surfactants can be used to improve the
dispersibility of the abrasive particles in the polyurethane urea.
In another non-limiting embodiment, coupling agents can be used to
enhance binding of the abrasive particles to the matrix of the
polyurethane urea. In further non-limiting embodiments, the surface
modifier can be present in an amount of less than 25 percent by
weight, or from 0.5 to 10 percent by weight, based on the total
weight of the abrasive particulate material and surface
modifier.
[0094] Non-limiting examples of suitable surfactants for use as
surface modifiers in the present invention can include anionic,
cationic, amphoteric and nonionic surfactants, such as but not
limited to metal alkoxides, polalkylene oxides, salts of long chain
fatty carboxylic acids. Non-limiting examples of suitable coupling
agents for use in the present invention can include silanes, such
as but not limited to organosilanes, titanates and zircoaluminates.
In a non-limiting embodiment, the coupling agent can include
SILQUEST Silanes A-174 and A-1230, which are commercially available
from Witco Corporation.
[0095] The polishing pad of the present invention can have shapes
chosen from but not limited to circles, ellipses, squares,
rectangles and triangles. In a non-limiting embodiment, the
polishing pad can be in the form of a continuous belt. The
polishing pads according to the present invention can have a wide
range of sizes and thicknesses. In a non-limiting embodiment, a
circular polishing pad can have a diameter ranging from 3.8 cm to
137 cm. In a further non-limiting embodiment, the thickness of the
polishing pad can vary from 0.5 mm to 5 mm.
[0096] In a non-limiting embodiment, the polishing pad of the
present invention can have a density of from 0.5 grams per cubic
centimeter (g/cc) to 1.1 g/cc as measured by ASTM 1622-88. In
another non-limiting embodiment, the polishing pad can have a Shore
A Hardness value of at least 80, or from 85 to 98, and Shore D
Hardness value of at least 35, or 85 or less, or from 45 to 80, as
determined in accordance with ASTM D 2240.
[0097] While not intending to be bound by any theory, it is
believed that when in use, while polishing or planarizing the
surface of a silicon wafer, the porosity of the work surface of the
polishing pad of the present invention can remain substantially
constant. As the work surface of the polishing pad is worn away
during, for example a polishing or pad conditioning process, new
surface pores are formed as those embedded pores residing
proximately below the work surface are exposed. Further, as the
work surface of the polishing pad is worn away during the polishing
process, the gas contained within the at least partially gas-filled
cells can be exposed. The gas can be released into the work
environment and the remaining void(s) can be at least partially
filled with polishing slurry.
[0098] In a non-limiting embodiment, the polishing pad can be
placed directly on the platen of a motorized polishing tool,
machine, or apparatus. In a further non-limiting embodiment, the
polishing pad can be included in a polishing pad assembly, wherein
a backing layer can be adhered to the back surface of the polishing
pad. In a non-limiting embodiment, a polishing pad assembly can
comprise: [0099] (a) a polishing pad having a work surface and a
back surface; [0100] (b) a backing layer having an upper surface
and a lower surface; and [0101] (c) an adhesive means interposed
between and in contact with at least a portion of the back surface
of said polishing pad and at least a portion of the upper surface
of said backing layer.
[0102] In a non-limiting embodiment, the backing sheet of the
polishing pad assembly can be rigid or flexible, and can support or
stabilize or cushion the polishing pad during polishing operations.
The backing sheet can be fabricated from materials that are known
to the skilled artisan. In alternate non-limiting embodiments, the
backing sheet can be fabricated from organic polymeric materials,
such as but not limited to polyesters, such as polyethylene
terephthalate sheet, and polyolefins, such as polyethylene sheet
and polypropylene sheet.
[0103] In another non-limiting embodiment, the backing sheet of the
polishing pad assembly of the present invention can be a release
sheet, which can be peeled away from the adhesive means, thereby
allowing the pad to be adhered to another surface, for example, the
platen of a polishing apparatus, by means of the exposed adhesive
means. In general, release sheets are known to those of ordinary
skill in art. In a non-limiting embodiment, the release sheet can
be fabricated from paper or organic polymeric materials, such as
but not limited to polyethylene terephthalate sheet, polyolefins,
for example, polyethylene sheet and polypropylene sheet, and
fluorinated polyolefins, for example, polytetrafluoroethylene. In a
further non-limiting embodiment, the upper surface of the release
sheet can comprise a release coating thereon that can be in contact
with the adhesive means. Release coatings are well known to the
skilled artisan. Non-limiting examples of release coatings can
include fluorinated polymers and silicones.
[0104] The adhesive can be chosen from a wide variety of adhesive
materials known in the art. 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
polishing pad and/or an upper surface of the backing layer which
are parallel facing to one another.
[0105] Non-limiting examples of suitable adhesive means can include
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.
[0106] 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.
[0107] In a non-limiting embodiment, the adhesive layer can be
applied to the back surface of the polishing pad and/or the upper
surface of the backing sheet, prior to pressing the polishing pad
and backing sheet together.
[0108] In alternate non-limiting embodiments, the adhesive means of
the polishing pad assembly can be selected from an adhesive
assembly or an adhesive layer.
[0109] In further non-limiting embodiment, the adhesive assembly
can comprise an adhesive support sheet interposed between an upper
adhesive layer and a lower adhesive layer. The upper adhesive layer
of the adhesive assembly can be in contact with the back surface of
the polishing pad, and the lower adhesive layer can be in contact
with the upper surface of the backing sheet. Non-limiting examples
of adhesive support sheets can be fabricated from an organic
polymeric material, such as but not limited to polyesters, for
example, polyethylene terephthalate sheet, and polyolefins, for
example, polyethylene sheet and polypropylene sheet. In a further
non-limiting embodiment, the upper and lower adhesive layers of the
adhesive assembly can be chosen from those adhesives as recited
previously herein with regard to the adhesive layer. In a
non-limiting embodiment, the upper and lower adhesive layers can
each be contact adhesives. In a further non-limiting embodiment,
the adhesive assembly can be a two-sided or double-coated tape,
such as but not limited to double-coated film tapes, which can be
commercially obtained from 3M, Industrial Tape and Specialties
Division.
[0110] In another non-limiting embodiment, the polishing pad can be
connected to at least a portion of a second layer to produce a
stacked pad assembly. In a further non-limiting embodiment, the
polishing pad can be connected to at least a portion of the second
layer using an adhesive material. Non-limiting examples of suitable
adhesive materials include those previously disclosed herein. In a
further non-limiting embodiment, the second layer can comprise an
adhesive assembly.
[0111] 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.
[0112] 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;
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.
[0113] Non-limiting examples of metallic films can include but are
not limited to aluminum, copper, brass, nickel, stainless steel,
and combinations thereof.
[0114] 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.
[0115] 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 polishing pad
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.
[0116] 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 the 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.-1lb.sup.-1; or at least 100
in.sup.-1lb.sup.-1; or from 1 in.sup.-1lb.sup.-1 to 100
in.sup.-1lb.sup.-1.
[0117] 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.
[0118] The compressibility of the second layer can vary. The term
"compressibility" refers to the percent volume compressibility
measurement when a load of 20 psi is applied. 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. The percent volume compressibility
can be determined using a variety of conventional methods known in
the art.
[0119] In a non-limiting embodiment, the second layer is
substantially non-volume compressible.
[0120] In another non-limiting embodiment, the second layer can
distribute the compressive forces experienced by the polishing pad
over a larger area of a sub-pad.
[0121] In another non-limiting embodiment, the second layer can
function as a substantial barrier to fluid transport between the
polishing pad and a sub-pad 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 polishing pad to a sub-pad. In a
non-limiting embodiment, the second layer can be substantially
impermeable to the polishing slurry such that the sub-pad does not
become saturated with polishing slurry.
[0122] In an alternate non-limiting embodiment, the second layer
can be perforated such that polishing slurry can penetrate the
polishing pad and second layer to wet the sub-pad. In a further
non-limiting embodiment, the sub-pad 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 1/16 inch with at least
26 holes per square inch in a staggered-hole pattern.
[0123] In another non-limiting embodiment, the polishing pad of the
present invention can be connected to at least a portion of a
sub-pad forming a composite or multi-layered structure. In a
further non-limiting embodiment, the polishing pad can be connected
to at least a portion of a sub-pad using an adhesive material.
Non-limiting examples of suitable adhesive materials can include
those previously described herein.
[0124] In a non-limiting embodiment, a sub-pad can be used with a
polishing pad to increase the uniformity of contact between the
polishing pad and the surface of the substrate which is being
polished. The sub-pad can be made of a compressible material
capable of imparting substantially even pressure to the work
surface of the polishing pad. Non-limiting examples of sub-pads can
include but are not limited to polyurethane and polyurethane urea
such as but not limited to polyurethane or polyurethane urea
impregnated felt; and foam sheet made of natural rubber, synthetic
rubber, thermoplastic elastomer essentially resilient foam sheet;
or combinations thereof.
[0125] In alternate non-limiting embodiments, the material of the
sub-pad can be foamed or blown to produce a porous structure. The
porous structure can be open cell, closed cell, or combinations
thereof.
[0126] 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
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;
polyurethane foam sheets and polyolefin foam sheets, such as but
not limited to those which are available from Rogers Corporation,
Woodstock, Conn.
[0127] In a further non-limiting embodiment, the sub-pad 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, such as polyurethane
impregnated felt. A non-limiting example of a commercially
available non-woven sub-pad can be Suba.TM. IV, from Rodel, Inc.
Newark Del.
[0128] The thickness of the sub-pad can vary. In general, the
sub-pad thickness should be such that the stacked pad is not too
thick. A stacked pad which is too thick can be difficult to place
on and take off of the planarization equipment. Thus, in a
non-limiting embodiment, the thickness of the sub-pad can be from
0.2 to 2 mm.
[0129] In a non-limiting embodiment, the polishing pad of the
present invention can comprise a sub-pad, and the sub-pad can
function as the bottom layer of the pad which can be attached to
the platen of the polishing apparatus.
[0130] In a non-limiting embodiment, the sub-pad can be
substantially nonporous and substantially impermeable to polishing
slurry. 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.
[0131] In a non-limiting embodiment, the sub-pad can be connected
to at least a portion of the polishing pad. In a further
non-limiting embodiment, the polishing pad can be connected to at
least a portion of a second layer, and the second layer can be
connected to at least a portion of a sub-pad.
[0132] In a non-limiting embodiment, the polishing pad of the
present invention can be used in combination with 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 having 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 polishing 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 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.
[0133] In a non-limiting embodiment, the window of the polishing
pad of the present invention can be prepared using a cast-in-place
process. This process can include forming an aperture in the
polishing pad. The polishing pad can include a pair of spaced
surfaces. The aperture can extend through said surfaces. The
aperture can be made using a variety of methods identified
previously herein. A spacer then can be inserted in the aperture of
the pad. The aperture can be sealed at one end. In non-limiting
alternate embodiments, the spacer can be temporary and can be
removed following formation of the window, or the spacer can be
permanent and remain intact following formation of the window. The
material, size and shape of the spacer can vary widely. In a
non-limiting embodiment, the spacer can be constructed of a
material that is at least partially transparent. In another
non-limiting embodiment, the spacer can be constructed of polyester
film. In general, the size and shape of the spacer can be such that
it fits securely in the aperture of the pad. In a non-limiting
embodiment, the spacer can be at least partially connected to the
material used to seal the opening. In a further non-limiting
embodiment, an adhesive tape can be used to seal the opening and
the spacer can be at least partially adhered to an adhesive portion
of the tape.
[0134] The aperture above the spacer can be filled with a resin
material to form an at least partially transparent panel within the
aperture which is at least partially connected to the pad. In a
non-limiting embodiment, the resin can be poured into the aperture
above the spacer such that the introduction of air voids into the
resin is minimized. In another non-limiting embodiment, the amount
of resin used can be such that the resin level is essentially flush
with a surface of the pad. In a further non-limiting embodiment,
the resin level is essentially flush with the work surface of the
pad. In another non-limiting embodiment, the bottom surface of the
spacer can be essentially flush with the outer surface of the
polishing pad.
[0135] In a non-limiting embodiment, the resin material can be
selected such that the resulting window formed can be at least
partially transparent to the wavelengths of the in-situ metrology
instrumentation of a polishing apparatus. In a further non-limiting
embodiment, the window formed can be substantially transparent.
Suitable resin materials can comprise materials known to one having
ordinary skill in the art that either is at least partially
transparent or can be made at least partially transparent.
Non-limiting examples of resin materials for use in the present
invention can include but are not limited to polyurethane
prepolymers with curative, epoxy resins with curative, ultraviolet
curable acrylics, and mixtures thereof. Non-limiting examples of
suitable materials for the resin can include thermoplastic acrylic
resins, thermoset acrylic resins, such as hydroxyl-functional
acrylic resins crosslinked with urea-formaldehyde or
melamine-formaldehyde resins, hydroxyl-functional acrylic resins
crosslinked with epoxy resins, or carboxyfunctional acrylic resins
crosslinked with carbodiimides or polyimines or epoxy resins;
urethane systems, such as hydroxyfunctional acrylic resin
crosslinked with polyisocyanate; diamine cured
isocyanate-terminated prepolymers; isocyanate-terminated
prepolymers crosslinked with polyamines; amine-terminated resins
crosslinked with polyisocyanates; 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, and mixtures
thereof.
[0136] In a non-limiting embodiment, the resin material can
comprise amine-terminated oligomer such as VERSALINK P650 which is
commercially available from Air Products and Chemicals, Inc.,
diamine such as LONZACURE MCDEA which is commercially available
from Air Products and Chemicals, Inc., and polyisocyanate such as
DESMODUR N 3300A which is commercially available from Bayer
Corporation Coatings and Colorants Division.
[0137] In alternate non-limiting embodiments, the resin material
for use in the present invention can include various conventional
additives known in the art. Non-limiting examples can include but
are not limited to processing aids and degassing aids.
[0138] In a further non-limiting embodiment, the resin which can be
used to form the panel in the aperture of the pad can be cured. The
curing process can include allowing the pad containing the resin to
set for a specified amount of time at a specified temperature. The
time and temperature used to cure the window resin can vary widely
and can depend on the resin material chosen to form the window.
Generally, a cure time can be chosen such that the resin is not
tacky or sticky to the touch. In general, a cure temperature can be
chosen such that warp or deformation of the window which can be
produced due to a cure temperature that is too low or too high does
not render the pad inoperable for the purpose of polishing an
object. In a non-limiting embodiment, the cure time can be from 30
minutes to 48 hours, or from 18 hours to 36 hours, or from 6 hours
to 24 hours, or from 1 hour to 4 hours. In a non-limiting
embodiment, the cure temperature can be from 0.degree. C. to less
than 125.degree. C., or from 5.degree. C. to 120.degree. C., or
from 10.degree. C. to 115.degree. C., or from 15.degree. C. to
110.degree. C., or from 22.degree. C. to 105.degree. C.
[0139] In a non-limiting embodiment, the aperture can be at least
partially filled with a resin material; and the resin material can
be cured/polymerized to form a polymer panel to function as the
window of the pad. In another non-limiting embodiment, the window
can include a polymer panel wherein the polymer is derived from a
resin material.
[0140] Following the curing step, the spacer and the adhesive tape
which was used to seal the opening, can be removed. In an alternate
non-limiting embodiment, following the curing step only the
adhesive tape can be removed and the spacer can remain in tact. In
a non-limiting embodiment, the resulting window area can be made
coplanar with the pad work surface using a milling machine.
[0141] In a non-limiting embodiment, the backing layer can be at
least partially connected to the work surface of the pad using an
adhesive means as previously described herein, and a window can be
formed in this pad assembly by using the cast-in-place process as
previously described herein. In this embodiment, the aperture can
extend through the lower surface of the backing layer through the
adhesive means and through the work surface of the pad.
[0142] In a non-limiting embodiment, a second layer can be at least
partially connected to the polishing pad and, an aperture can be
formed in the polishing pad and second layer of a stacked pad as
previously described for the polishing pad. The aperture then can
be sealed on the side of the second layer that is not at least
partially connected to the polishing pad. The material used to
seal-off the aperture can be chosen from a wide variety of
materials known in the art. Suitable materials can include but are
not limited to adhesive materials such as adhesive tape.
[0143] In a non-limiting embodiment, the polishing pad can include
a stacked pad assembly which comprises additional layers. Each
additional layer can contain an aperture and the aperture(s) can be
substantially aligned with the aperture of the polishing pad. In a
non-limiting embodiment, a stacked pad assembly can have three
layers. In a further embodiment, the layers can include a polishing
pad, a second layer and a sub-pad. The three layers can be at least
partially connected to one another as previously described herein
(i.e., the polishing pad connected to at least a portion of the
second layer, and the second layer connected to at least a portion
of the sub-pad).
[0144] In a further non-limiting embodiment, a 22.0'' diameter SUBA
IV subpad commercially available from Rodel, Incorporated can
comprise the sub-pad. An aperture can be formed in the subpad, and
the aperture can at least partially align with the aperture of the
second layer and the aperture of the polishing pad. In a further
non-limiting embodiment, the aperture can be rectangular in shape,
having dimensions of 0.5''.times.2.0'', being positioned with the
long axis radially-oriented and centered 4'' from the center of the
pad. In alternate non-limiting embodiments, the aperture(s) can be
formed in the layers prior to at least partially connecting the
layers, or the aperture can be formed following at least partially
connecting the layers. In a non-limiting embodiment, the polishing
pad can be at least partially connected to the second layer, an
aperture can be formed in the polishing pad and second layer, the
release liner of the second layer can be removed, and the exposed
adhesive can be used to at least partially connect the second layer
to the SUBA IV sub-pad. An aperture can be formed in the sub-pad
prior to or after at least partially connecting the sub-pad to the
polishing pad and second layer assembly. The aperture in the
sub-pad can be at least partially aligned with the aperture in the
other two layers. A spacer can be inserted into the aperture of the
assembly, and the aperture above the spacer can be filled with
resin to form a window as previously described herein.
[0145] In another non-limiting embodiment, the window can be formed
in the polishing pad and second layer assembly as previously
described herein, and the sub-pad containing an aperture then can
be at least partially connected to the assembly such that the
aperture in the sub-pad is at least partially aligned with the at
least partially transparent panel in the polishing pad and second
layer.
[0146] Depending on the material of which the spacer is
constructed, the spacer can remain in the window area or it can be
removed. In alternate non-limiting embodiments, the spacer can be
constructed of a material that is at least partially transparent,
or substantially transparent, or transparent to at least one
wavelength from 190 to 3500 nanometers, and the spacer can remain
in the window pad assembly. In another non-limiting embodiment, the
spacer can be constructed of a material that may not be at least
partially transparent, and the spacer can be removed. A wide
variety of known materials are suitable for use as a spacer in the
present invention. Non-limiting examples can include but are not
limited to polyesters, polyethylene teraphalate sheet, polyolefins
such as but not limited to polyethylene sheet, polyamides, acrylics
and combinations thereof. In a non-limiting embodiment of the
invention, the spacer can be removed from the window area.
[0147] In another non-limiting embodiment, the spacer can be
positioned such that it is not flush with the outer surface of the
sub-pad.
[0148] 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.
[0149] 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.
[0150] The present invention is more particularly described in the
following examples, which are intended to be illustrative only,
since numerous modifications and variations therein will be
apparent to those skilled in the art. Unless otherwise specified,
all parts and all percentages are by weight.
EXAMPLES
Example 1
[0151] 36.00 kilograms of Airthane PHP-75D polyurethane prepolymer
, 1.26 kilograms of Desmodur N 3300A and 0.19 kilograms of Niax
L-1800 surfactant were charged into the first tank of a Baule'
three-component low pressure dispensing machine and held at
140.degree. F. with 15 PSI of nitrogen pressure. This tank was
mixed with low agitation. A curative mixture was prepared by
melting 35.5 kilograms of Lonzacure MCDEA at a temperature of
210.degree. F. then 5.5 kilograms of Versalink P-250 were added
with stirring. Next, 0.21 kilograms of Niax L1800 added and stirred
until uniformly mixed. This curative mixture was then charged into
the second tank and held at 210.degree. F. with 40 psi of nitrogen
pressure and mixed with low aggitation. Then a mixture of 219 grams
Versalink P-650, 60 grams of DABCO BL-19 catalyst and 21 grams of
deionized water were charged into the third tank at ambient
temperature and pressure. The fluids of the first, second and third
tanks were fed into a mixer, by constant delivery pumps, at a
weight ratio of 242 grams from the first tank : 100 grams from the
second tank : 1.80 grams from the third tank. The fluids were mixed
under high agitation and dispensed into an open circular mold
having a diameter of 31 inches and a thickness of 0.090 inches
which had been preheated to 160.degree. F. The open mold was placed
in an oven at 160.degree. F. for 15 minutes. After this time, the
product was removed from the mold. Curing was continued for 18
hours at 230.degree. F. The product was then allowed to cool to
ambient temperature. A double-coated film tape with release liner
was applied to one surface of the cured sheets. The film tape was
commercially obtained from 3M as type 9609 double-coated film
tape.
[0152] A circular pad having a 20'' diameter was cut from the
molded part. The pad was then cut to a thickness of 0.090 inches
and the upper and lower surfaces of the pad were made parallel
using a milling machine. Concentric circular grooves 0.020''
wide.times.0.030'' deep with a pitch of 0.060'' were machined into
the work surface. A window opening was then cut in the pad. The
shape of the opening was rectangular, having dimensions of
0.5''.times.2.0'', being positioned with the long axis radially
oriented and centered 4'' from the center of the pad. The pad
opening was sealed on the liner side with a 4''.times.4'' piece of
3M 9609 double-sided tape. A spacer, constructed of 0.010''
polyester film, cut with dimensions to fit securely in the pad
opening, was placed in the opening and firmly attached to the
exposed adhesive of the 4''.times.4'' 3M 9609 tape. A window resin
was then prepared from the ingredients listed in Table 1.
TABLE-US-00001 TABLE 1 Ingredients Weight (grams) Charge 1
LONZACURE MCDEA 11.3 VERSALINK P650 70.8 ETHACURE 100 7.7 Charge 2
AIRTHANE PHP-75D 42.0 DESMODUR N 3300A 48.0
AIRTHANE 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). DESMODUR N 3300A aliphatic polyisocyanate, obtained from
Bayer Corporation, Coatings and Colorants Division, which describes
it as a polyfunctional aliphatic isocyanate resin based on
hexamethylene diisocyanate. NIAX Silicone L-1800 was obtained from
GE Silicones. LONZACURE MCDEA diamine curative, obtained from Air
Products and Chemicals, Inc, which describes it as methylene
bis(chlorodiethylanaline). VERSALINK P250 oligomeric diamine
curative was obtained from Air Products and Chemicals, Inc.
VERSALINK P650 oligomeric diamine curative, obtained from Air
Products and Chemicals, Inc, which describes it as
polytetramethylene ether glycol-diamine. DABCO BL-19 catalyst,
obtained from Air Products and Chemicals, Inc, which describes it
as bis(2-dimethylamino ethyl) ether. ETHACURE 100, obtained from
Albemarle Corporation, which describes it as
diethyltoluenediamine.
[0153] Charge 1 was added to an open stainless steel container and
placed on a hot plate set at a temperature of 120.degree. C. until
the contents of the container became molten. The contents were
thoroughly mixed with a stainless steel spatula until uniform.
Charge 1 was then degassed to remove moisture and entrained air by
placing the container in a vacuum oven set at 80.degree. C. and
pulling a vacuum of 1 mm to 5 mm Hg until bubbling ceased and any
foaming subsided. The container was then removed from the vacuum
oven, Charge 2 was added to Charge 1 and mixed with a spatula until
uniform. The container was then placed in a second vacuum oven at
ambient temperature and a 1 mm to 5 mm Hg vacuum was pulled for 5
minutes to remove any entrained air resulting from mixing.
[0154] The container of resin was then removed from the vacuum oven
and a portion of the resin was carefully poured into the pad window
opening, containing a spacer, so as not to introduce air voids into
the resin. Sufficient resin was poured to bring the resin level
flush with the upper pad surface. The resin was then allowed to
cure overnight at ambient conditions. After curing, the
4''.times.4'' piece of 3M 9609 double sided tape and the spacer
were removed. The window area was then made coplanar with the pad
work surface using a milling machine.
Example 2
[0155] A stacked pad was constructed by mounting the polishing pad
assembly of Example 1 on a 22.0'' diameter subpad. The subpad
consisted of a polyurethane foam disk having a diameter of 20''
which was die cut from a sheet of PORON FH 48 available from Rogers
Corporation, Woodstock, Conn., having a thickness of 1.5
millimeters and a density of 0.48 g/cm.sup.3. Another double-coated
film tape with release liner was commercially obtained from
Adhesives Research, Inc. under the trade name ARclad 90334. The
adhesive side was applied to the surface of the polyurethane foam.
A window opening was then cut into the 20'' diameter foam pad and
double-coated film tape with release liner. The shape of the
opening was rectangular, having dimensions of 0.5''.times.2.0'',
being positioned with the long axis radially oriented and centered
4'' from the center of the pad. Next, the release liner of the
polishing pad assembly of Example 1 was removed, exposing the
adhesive. The polishing pad assembly was then firmly bonded, with
this adhesive, to the polyurethane foam side of the subpad. Care
was taken during mounting so that the window opening in the subpad
was aligned with the pad window. The remaining release liner on the
subpad can be removed to permit attachment to a commercial
planarizing apparatus.
* * * * *