U.S. patent application number 11/466641 was filed with the patent office on 2007-01-25 for polyurethane urea polishing pad with window.
This patent application is currently assigned to PPG INDUSTRIES OHIO, INC.. Invention is credited to William C. Allison, Robert G. Swisher, Alan E. Wang.
Application Number | 20070021045 11/466641 |
Document ID | / |
Family ID | 34972592 |
Filed Date | 2007-01-25 |
United States Patent
Application |
20070021045 |
Kind Code |
A1 |
Swisher; Robert G. ; et
al. |
January 25, 2007 |
Polyurethane Urea Polishing Pad with Window
Abstract
The present invention relates to an article for altering a
surface of a work piece, 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: |
Deborah M. Altman;PPG Industries, Inc.
Law- Intellectual Property 39S, One PPG Place
Pittsburgh
PA
15272
US
|
Assignee: |
PPG INDUSTRIES OHIO, INC.
3800 WEST 143RD STREET
CLEVELAND
OH
|
Family ID: |
34972592 |
Appl. No.: |
11/466641 |
Filed: |
August 23, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10974517 |
Oct 27, 2004 |
|
|
|
11466641 |
Aug 23, 2006 |
|
|
|
Current U.S.
Class: |
451/527 |
Current CPC
Class: |
B32B 27/065 20130101;
B32B 2457/14 20130101; B32B 2432/00 20130101; B32B 2475/00
20130101; B32B 3/18 20130101; B32B 2307/412 20130101; B24D 3/32
20130101; B32B 5/18 20130101; B32B 27/36 20130101; B32B 2264/102
20130101; B24B 37/205 20130101; B32B 2266/08 20130101; B32B 5/20
20130101; B32B 2307/554 20130101; B32B 2266/0278 20130101 |
Class at
Publication: |
451/527 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A pad adapted to polish a microelectronic substrate, said pad
comprising: a. a polyurethane urea-containing polishing layer, said
polishing layer comprising at least partially gas-filled cells, at
least a portion of said at least partially gas-filled cells formed
by an in-situ reaction, wherein an opening is formed in said
polishing layer; and b. a second layer wherein at least a portion
of said second layer comprises an at least partially transparent
window, wherein said polishing layer is at least partially
connected to said second layer, and said opening in said polishing
layer is at least partially aligned with said window of said second
layer.
2. The pad of claim 1, wherein said polishing layer is formed by
reaction of hydroxyl-containing material, amine-containing
material, blowing agent and at least one material selected from the
group consisting of polyisocyanate, polyurethane prepolymer and
mixtures thereof.
3. The pad of claim 1, wherein gas in at least a portion of said at
least partially gas-filled cells is exposed when at least a portion
of a work surface of said pad is at least partially worn away when
said work surface is in contact with a substrate to be
polished.
4. The pad of claim 1, further comprising at least one material
selected from urethane catalyst, blowing catalyst, surfactant, and
nucleating agent.
5. The pad of claim 1 wherein said pad has a work surface and said
surface comprises at least one feature selected from the group
consisting of channels, grooves and perforations.
6. The pad of claim 1 wherein said polyurethane urea comprises
abrasive particulate material.
7. The pad of claim 6 wherein said abrasive particulate material is
distributed substantially uniformly throughout said polyurethane
urea.
8. The pad of claim 6 wherein said abrasive particulate material is
present in an amount of from 5% by weight to less than 70% by
weight based on the total weight of the pad.
9. The pad of claim 6 wherein said abrasive particulate material
has an average particle size of from 0.001 micron to less than 50
microns.
10. The pad of claim 6 wherein said abrasive particulate material
is silica.
11. The pad of claim 1 wherein said second layer is selected from
polyolefins, cellulose-based polymers, acrylics, polyesters and
co-polyesters, polycarbonates, polyamides, plastics, and
combinations thereof.
12. The pad of claim 1 wherein said second layer is selected from
substantially non-compressible polymers, metallic films and foils,
and combinations thereof.
13. The pad of claim 1 further comprising a sub-pad layer having an
opening formed therein, said sub-pad layer at least partially
connected to said second layer, and wherein said opening in said
sub-pad layer at least partially aligns with said window of said
second layer and said opening in said polishing layer.
14. The pad of claim 13 wherein said sub-pad layer is chosen from
non-woven fiber mat, woven fiber mat, or combinations thereof.
15. The pad of claim 13 wherein said sub-pad layer is chosen from
polyurethane impregnated felt, polyurethane urea impregnated felt,
or combinations thereof.
16. The pad of claim 13 wherein said sub-pad layer is selected from
foam sheet containing natural rubbers, synthetic rubbers,
thermoplastic elastomers or combinations thereof.
18. A pad assembly comprising: a. a polishing layer comprising
polyurethane urea wherein at least a portion of said polyurethane
urea comprises at least partially gas-filled cells wherein at least
a portion of said cells are formed by an in-situ reaction, said
polishing layer having a work surface and a back surface; and b. a
backing sheet having an upper surface and a lower surface; and c.
an adhesive means interposed between and at least partially
connecting said back surface of said polishing layer and an upper
surface of said backing sheet, at least a portion of said adhesive
means being at least partially transparent, wherein an opening is
formed in each of said polishing layer and said backing sheet, and
wherein said openings in each polishing layer and backing sheet are
at least partially aligned with said transparent portion of said
adhesive means, and wherein said polishing layer is at least
partially connected to said adhesive means and said adhesive means
is at least partially connected to said backing sheet.
19. The pad assembly of claim 18 wherein said polyurethane urea is
formed by combining hydroxyl-containing material, amine-containing
material, blowing agent and at least one material selected from the
group consisting of polyisocyanate, polyurethane prepolymer and
mixtures thereof.
20. A stacked pad adapted to polish a microelectronic substrate,
said pad comprising: a. a polyurethane urea-containing polishing
layer, said polishing layer comprising at least partially
gas-filled cells, wherein an opening is formed in said polishing
layer; b. a second layer wherein at least a portion of said second
layer comprises an at least partially transparent window, wherein
said polishing layer is connected to said second layer, and said
opening in said polishing layer is aligned with said window of said
second layer; and c. a subpad layer connected to said second layer.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of pending U.S. patent
application Ser. No. 10/974,517 filed on Oct. 27, 2004 entitled
"Polyurethane Urea Polishing Pad" which published Apr. 27, 2006 as
publication number 2006-0089094 that is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an article for altering a
surface of a work piece. In particular, the present invention is
directed to a polishing pad having a window. More particularly, the
polishing layer of the pad can include a polyurethane urea material
wherein cells at least partially filled with gas are substantially
uniformly distributed throughout at least a portion of 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.
[0004] 2. Background Information
[0005] 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.
[0006] 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
material, 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.
[0007] 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.
[0008] 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.
[0009] 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 platen window.
[0010] 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.
[0011] 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.
SUMMARY OF THE INVENTION
[0012] 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.
[0013] 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.
[0014] The present invention includes a pad adapted to polish a
microelectronic substrate. The pad includes a polyurethane
urea-containing polishing layer. The polishing layer can include at
least partially gas-filled cells and at least a portion of the at
least partially gas-filled cells can be formed by an in-situ
reaction. The polishing layer has an opening formed therein. The
pad of the present invention includes a second layer wherein at
least a portion of the second layer can include an at least
partially transparent window. The polishing layer is at least
partially connected to the second layer, and the opening in the
polishing layer is at least partially aligned with the window of
the second layer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] The present invention includes a pad adapted to polish a
microelectronic substrate. The pad includes a polyurethane
urea-containing polishing layer. The polishing layer can include at
least partially gas-filled cells, at least a portion of the at
least partially gas-filled cells can be formed by an in-situ
reaction. The polishing layer has an opening formed therein. The
pad of the present invention includes a second layer wherein at
least a portion of the second layer can include an at least
partially transparent window. The polishing layer is at least
partially connected to the second layer, and the opening in the
polishing layer is at least partially aligned with the window of
the second layer.
[0016] The present invention includes a polishing pad having a
window. The polishing pad can include a first layer and a second
layer. The second layer can be at least partially connected to the
first layer. The term "connected to" means to link together or
place in relationship either directly, or indirectly, by one or
more intervening materials. The first layer can function as the
work surface or the polishing layer of the pad. The polishing layer
can at least partially interact with the substrate to be polished
and the polishing slurry. In a non-limiting embodiment, at least a
portion of the second layer of the pad can comprise a window which
is at least partially transparent to wavelengths used by the
metrology instrumentation of polishing tools. In a non-limiting
embodiment, the polishing pad of the present invention can include
a sub-pad layer at least partially connected to the second layer.
In a non-limiting embodiment, the cells can be substantially
uniformly distributed throughout the material and/or polishing
layer.
[0017] In alternate non-limiting embodiments, the polyurethane urea
of the present invention can be prepared by combining a
polyisocyanate with hydroxyl-containing material, amine-containing
material and blowing agent; or by reacting a two-component
composition comprising combining polyisocyanate and
hydroxyl-containing material to form a polyurethane prepolymer, and
then reacting the prepolymer with amine-containing material and
blowing agent; or by combining polyisocyanate and/or polyurethane
prepolymer, optional hydroxyl-containing material, amine-containing
material and blowing agent.
[0018] 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.
[0019] 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--).
[0020] 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.
[0021] Non-limiting examples of suitable polyisocyanates can
include but are not limited to polyisocyanates having at least two
isocyanate groups.
[0022] 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.
[0023] 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).
[0024] 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.
[0025] 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.
[0026] 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).
[0027] In a non-limiting embodiment, the polyisocyanate can include
2,4-tolylene diisocyanate; 2,6-tolylene diisocyanate and mixtures
of these isomers ("TDI").
[0028] 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.TM.
(Meta) Aliphatic Isocyanate.
[0029] 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 the TMXDI brand and compounds of the
formula R--(NCO).sub.2 wherein R represents an aliphatic group or a
cycloaliphatic group.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] In a non-limiting embodiment of the present invention, the
polyisocyanate for use in the present invention can include
polyurethane prepolymer.
[0036] In a non-limiting embodiment, polyisocyanate can be reacted
with hydroxyl-containing material to form polyurethane prepolymer,
and said prepolymer can be reacted with amine-containing material
and blowing agent to produce the polyurethane urea of the present
invention. In another non-limiting embodiment, polyisocyanate and
polyurethane prepolymer can be reacted with hydroxyl-containing
material, amine-containing material and blowing agent. In a further
non-limiting embodiment, polyisocyanate and polyurethane prepolymer
can be reacted with amine-containing material and blowing
agent.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] In a non-limiting embodiment, polyalkoxylated polyols can be
represent by the following general formula: ##STR1##
[0041] 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.
[0042] 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.
[0043] 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. polyether glycol 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.
[0044] A 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.
[0045] 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.
[0046] 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.
[0047] 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, 1,4- 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.
[0048] 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.
[0049] 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.
[0050] 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)
[0051] 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 material does not exceed 32,000
grams/mole.
[0052] In further alternate non-limiting embodiments,
hydroxyl-containing materials such as but not limited to
Pluronic.TM. R, Pluronic.TM., Tetronic.TM. R and Tetronic.TM. Block
Copolymer Surfactants, which are commercially available from BASF,
can be used as the hydroxyl-containing material in the present
invention.
[0053] 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.
[0054] In a non-limiting embodiment, the polyol can be chosen from
multifunctional polyols, including but not limited to
trimethylolpropane, ethoxylated trimethylolpropane,
pentaerythritol.
[0055] 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.
[0056] 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.
[0057] In a further non-limiting embodiment, polyether glycols for
use in the present invention can include but are not limited to
polytetramethylene ether glycol.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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##
[0062] 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):
[0063] LONZACURE.RTM. M-DIPA: R.sub.1=C.sub.3H.sub.7;
R.sub.2=C.sub.3H.sub.7; R.sub.3=H
[0064] LONZACURE.RTM. M-DMA: R.sub.1=CH.sub.3;
[0065] LONZACURE.RTM. M-MEA: R.sub.1=CH.sub.3;
R.sub.2=C.sub.2H.sub.5; R.sub.3=H
[0066] LONZACURE.RTM. M-DEA: R.sub.1=C.sub.2H.sub.5; R.sub.3=H
[0067] LONZACURE.RTM. M-MIPA: R.sub.1=CH.sub.3;
R.sub.2=C.sub.3H.sub.7; R.sub.3=H
[0068] LONZACURE.RTM. M-CDEA: R.sub.1=C.sub.2H.sub.5;
R.sub.2=C.sub.2H.sub.5; R.sub.3=Cl
[0069] wherein R.sub.1, R.sub.2 and R.sub.3 correspond to the
aforementioned chemical formula.
[0070] 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.
[0071] 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).
[0072] In alternate non-limiting embodiments of the present
invention, the amine-containing curing agent can include one of the
following general structures: ##STR3##
[0073] 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##
##STR6##
[0074] wherein R.sub.3 and 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 XII 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).
[0075] In a further non-limiting embodiment, the amine-containing
curing agent can include materials which can be represented by the
following general structure (XXI): ##STR7##
[0076] 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.
[0077] In alternate non-limiting embodiments, the 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.
[0078] In alternate non-limiting embodiments, polyurethane
prepolymer and optionally polyisocyanate can be contained in a
first feed of a mixing unit, the amine-containing agent and
optionally hydroxyl-containing material in a second feed and the
blowing agent in a third feed; or the second feed can include both
the amine-containing material and the blowing agent, and optionally
hydroxyl-containing material.
[0079] In another non-limiting embodiment, the polyurethane urea
can be prepared by a one-pot process by combining polyisocyanate
and/or polyurethane prepolymer, hydroxyl-containing material,
amine-containing material and blowing agent.
[0080] 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 prepolymer, 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-curing agent and blowing agent;
or the second feed can contain hydroxyl-containing 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 further non-limiting embodiments, wherein
polyurethane prepolymer is present in a first feed, the presence of
hydroxyl-containing material in another feed is optional.
[0081] 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.
[0082] 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, and diethylether.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] Suitable urethane-forming catalysts can vary widely, 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.
[0087] 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.
[0088] 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.
[0089] 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 Silicon Incorporated under
the designations Niax.TM. 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.
[0090] In a further non-limiting embodiment, the
siloxane-polyoxyalkylene copolymer surfactant can be represented by
the following general formula, ##STR8##
[0091] 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.
[0092] 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)
[0093] 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.
[0094] 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.
[0095] 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.
[0096] 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 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.
[0097] 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 then can 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.
[0098] 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 layer can have
surface features such as but not limited to channels, grooves,
perforations and combinations thereof.
[0099] Surface features can be incorporated into the work surface
of the polishing layer by means that are known to those of ordinary
skill in the art. In a non-limiting embodiment, the work surface
can be mechanically modified, for example, by abrading or cutting.
In another non-limiting embodiment, surface features can be
incorporated into the work surface 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
during its formation. Surface features can be distributed in the
form of random or uniform patterns across the work surface.
Non-limiting examples of surface feature patterns can include but
are not limited to spirals, circles, squares, cross-hatches and
waffle-like patterns.
[0100] 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.
[0101] 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.
[0102] 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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] In a further non-limiting embodiment, the thickness of the
polishing layer can vary from 0.5 mm to 5 mm.
[0107] In a non-limiting embodiment, the polishing layer 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 layer 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.
[0108] 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 layer 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.
[0109] The polishing pad of the present invention includes a second
layer at least partially connected to the polishing layer. 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.
[0110] 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.
[0111] Non-limiting examples of metallic films can include but are
not limited to aluminum, copper, brass, nickel, stainless steel,
and combinations thereof.
[0112] 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.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] In a non-limiting embodiment, the second layer is
substantially non-volume compressible.
[0118] 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 layer.
[0119] In a non-limiting embodiment, the polishing pad of the
present invention can be used without a sub-pad layer. The
polishing pad without a sub-pad layer 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:
[0120] (a) a polishing pad having a work surface and a back
surface;
[0121] (b) a backing layer having an upper surface and a lower
surface; and
[0122] (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.
[0123] 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.
[0124] 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.
[0125] 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 second layer which are
parallel facing to one another.
[0126] 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.
[0127] 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.
[0128] 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.
[0129] In alternate non-limiting embodiments, the adhesive means of
the polishing pad assembly can be selected from an adhesive
assembly or an adhesive layer.
[0130] 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.
[0131] At least a portion of the polishing pad of the present
invention includes an at least partially transparent window. In a
non-limiting embodiment of the present invention, the polishing
layer can comprise an opening. In a further non-limiting
embodiment, at least a portion of the second layer can comprise a
window which is at least partially transparent to wavelengths used
by the metrology instrumentation of the planarizing equipment. The
opening in the polishing layer can at least partially align with
the window in the second layer. The size, shape, and positioning of
the opening in the polishing layer and/or the window in the second
layer can be dependent upon the metrology instrumentation and
polishing apparatus being employed to polish and/or planarize the
pad. The opening in the polishing layer can be produced by a
variety of conventional methods known in the art. In alternate
non-limiting embodiments, the opening can be made by punching, die
cutting, laser cutting or water jet cutting. In a further
non-limiting embodiment, the opening can be formed when molding the
polishing layer. In an alternate non-limiting embodiment, the
opening can be die cut into the polishing layer using an NAEF Model
B die press fitted with dies of suitable size and shape, which are
commercially available from MS Instruments Company, Stony Brook,
N.Y.
[0132] In a non-limiting embodiment, the opening in the polishing
layer can be produced prior to stacking together and/or at least
partially connecting the polishing layer with the second layer.
[0133] At least a portion of the second layer can comprise an at
least partially transparent window. In a non-limiting embodiment,
the second layer can comprise an at least partially transparent
material. In another non-limiting embodiment, the second layer can
comprise a substantially non-transparent material; an opening can
be cut into the second layer to remove a portion of the second
layer; an at least partially transparent material can be inserted
into the opening in the second layer. The opening can be made using
a variety of methods previously described herein. In a non-limiting
example, the second layer can include a metal foil; an opening can
be cut into the metal foil to remove a portion of the metal foil; a
piece of polyester can be cut into a size and shape that
substantially corresponds to the opening; the polyester can be
fitted into the opening in the metal foil to form an at least
partially transparent window.
[0134] In a non-limiting embodiment, the second layer can comprise
an adhesive assembly. The adhesive assembly can include interposing
a middle layer between an upper adhesive layer and a lower adhesive
layer. In a non-limiting embodiment, the upper adhesive layer of
the adhesive assembly can be at least partially connected to the
lower surface of the polishing layer. In a non-limiting embodiment,
the lower adhesive layer of the adhesive assembly can be at least
partially connected to the platen of the polishing tool. In another
non-limiting embodiment, the lower adhesive layer of the adhesive
assembly can be at least partially connected to the upper surface
of a sub-pad layer. The middle layer of the adhesive assembly can
be selected from the aforementioned suitable materials for the
second layer of the polishing pad. The upper and lower adhesive
layers of the adhesive assembly can be selected from the
non-limiting examples of adhesives previously mentioned herein. In
a non-limiting embodiment, the upper and lower adhesive layers each
can be contact adhesives. The adhesive assembly can be referred to
in the art as two-sided or double-coated tape. Non-limiting
examples of commercially available adhesive assemblies include
those from 3M, Industrial Tape and Specialties Division.
[0135] In a further non-limiting embodiment, at least a portion of
the adhesive layer can be removed from the second layer of the
adhesive assembly exposing at least a portion of the at least
partially transparent middle layer of the adhesive assembly,
thereby forming an at least partially transparent window in the
second layer. In alternate non-limiting embodiments, the removal of
the adhesive can be performed prior to stacking the layers or after
the layers are stacked. The removal process can include a variety
of methods known to the skilled artisan, including but not limited
to dissolution of the adhesive in solvent or aqueous detergent
solution, or physically stripping the adhesive from the second
layer. In a non-limiting embodiment, physically stripping the
adhesive can be include contacting the adhesive with a material to
which the adhesive substantially adheres, and then pulling the
material from the second layer, whereby the adhesive is removed
with the material.
[0136] In a further non-limiting embodiment, the window of the
second layer can be recessed below the surface of the pad by a
distance equal to the thickness of the polishing layer of the pad.
In another non-limiting embodiment, the pad can include a coating
on at least a portion of a side of the window of the second layer.
The coating can be at least partially applied with an adhesive in
place or following removal of the adhesive. The coating can be at
least partially applied prior to stacking the layers or after the
layers have been stacked. The coating can provide any one of the
following properties, for example: improved transparency of the
window area, improved abrasion resistance, improved puncture
resistance.
[0137] In a non-limiting embodiment, the coating can include a
resin film, or a cast-in-place resin coating. Non-limiting examples
of suitable resin films for use in the present invention can
include the materials described above for the second layer. In
alternative non-limiting embodiments, the resin film chosen for the
coating can be the same material or different material as that
comprising the second pad layer. The resin film can be at least
partially adhered to the window area of the second layer by any
means known to the skilled artisan, such as the adhesive methods
and materials listed above for pad stack adhesives. In a
non-limiting embodiment, the coating can be a layer of resin film
that can be the same as the material used for the second layer. The
coating can be at least partially applied after assembly of the pad
stack. The coating can be at least partially applied to both the
top and bottom surfaces of the window area of the second layer, and
the adhesive can be at least partially adhered using a contact
adhesive used as the stack adhesive.
[0138] In a non-limiting embodiment, the coating can be a
cast-in-place resin coating, which can be applied as a liquid, as a
solvent solution, dispersion, or aqueous latex, as a melt, or as a
blend of resin precursors that can react to form the coating. The
application of the liquid can be accomplished by a variety of known
methods, including spraying, padding, and pouring. Non-limiting
examples of suitable materials for the coating include
thermoplastic acrylic resins, thermoset acrylic resins, such as
hydroxyl-functional acrylic latexes crosslinked with
urea-formaldehyde or melamine-formaldehyde resins,
hydroxyl-functional acrylic resins crosslinked with epoxy resins,
or carboxyfunctional acrylic latexes crosslinked with carbodiimides
or polyimines or epoxy resins; urethane systems, such as
hydroxyfunctional acrylic resin crosslinked with polyisocyanate,
moisture-cured isocyanate-terminated resins; carbamate-funtional
acrylic resins crosslinked with melamine-formaldehyde resins; epoxy
resins, such as polyamide resin crosslinked with bisphenol A epoxy
resins, phenolic resins crosslinked with bisphenol A epoxy resins;
polyester resins, such as hydroxyl-terminated polyesters
crosslinked with melamine-formaldehyde resins or with
polyisocyanates or with epoxy crosslinkers.
[0139] In a non-limiting embodiment, the coating can be an aqueous
acrylic latex, which can be applied following stacking of the pad
assembly. The coating can be at least partially applied to the top
and bottom surfaces of the window area of the second layer.
Application of the coating can be performed following removal of an
adhesive from the window area.
[0140] In another non-limiting embodiment, the polishing pad of the
present invention can include a sub-pad layer. The sub-pad layer
can be at least partially connected to the second layer, and the
second layer can be at least partially connected to the polishing
layer. In a non-limiting embodiment, the second and/or sub-pad
layers can be at least partially connected by an adhesive means.
Suitable adhesive means can include those previously described
herein. In a further non-limiting embodiment, a sub-pad layer can
be used to increase the uniformity of contact between the polishing
pad and the surface of the substrate which is being polished. The
sub-pad layer 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-pad layers can include
but are not limited to polyurethane or polyurethane urea
impregnated felt, and foam sheet made of natural rubber, synthetic
rubber, thermoplastic elastomer; or combinations thereof.
[0141] In alternate non-limiting embodiments, the material of the
sub-pad layer can be foamed or blown to produce a porous structure.
The porous structure can be open cell, closed cell, or combinations
thereof.
[0142] 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
polyurethane foam sheet and polyolefin foam sheets, such as but not
limited to those which are commercially available from Rogers
Corporation, Woodstock, Conn.
[0143] In a further non-limiting embodiment, the sub-pad layer 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 layer can be Suba.TM. IV, from Rodel,
Inc. Newark, Del.
[0144] The thickness of the sub-pad layer can vary widely. In
general, the sub-pad layer 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 layer can be from 0.2 to 2 mm.
[0145] In a non-limiting embodiment, the polishing pad of the
present invention can comprise a sub-pad layer, and the sub-pad
layer can function as the bottom layer of the pad which can be
attached to the platen of the polishing tool.
[0146] In a non-limiting embodiment, the sub-pad layer 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.
[0147] In another non-limiting embodiment, a three-layer stacked
pad can be constructed by at least partially connecting the
polishing layer to the second layer and at least partially
connecting the second layer to a sub-pad layer. In a further
non-limiting embodiment, a 22.0'' diameter SUBA IV subpad
commercially available from Rodel, Incorporated can comprise the
sub-pad layer. An opening can be cut into the polishing layer,
second layer and sub-pad layer as described previously herein. In a
further non-limiting embodiment, the opening 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. A window can be formed in the second layer as
previously described herein. In alternate non-limiting embodiments,
the opening can be cut into the SUBA IV pad prior to at least
partially connecting it to the second layer, or the opening can be
cut following at least partially connecting the polishing layer,
second layer and sub-pad layer.
[0148] In another non-limiting embodiment, the window can be formed
in the polishing layer and second layer assembly as previously
described herein, and the sub-pad layer containing an opening then
can be at least partially connected to the second layer such that
the opening in the sub-pad layer is at least partially aligned with
the opening in the polishing pad and window in the second layer. An
opening can be cut into the sub-pad prior to or after at least
partially connecting the sub-pad to the polishing pad and second
layer assembly. In alternate non-limiting embodiments, the opening
can be produced by any suitable means known in the art, such as
those previously identified relative to the opening in the
polishing layer. Further, as previously identified, the size, shape
and position of the opening can be dependent upon the metrology
instrumentation and polishing apparatus employed.
[0149] In another non-limiting embodiment, the polishing pad of the
present invention can comprise a polishing layer, a second layer,
and a sub-pad layer. The polishing and sub-pad layers can each
comprise an opening. The openings in these two layers can be at
least partially aligned with one another. At least a portion of the
second layer can include an at least partially transparent window.
The window can be at least partially coated on both sides with
contact adhesive, and the layers can be pressed together to form a
stacked pad assembly. The adhesive can then be physically stripped
from the top and bottom surface of the window area of the second
layer using a material to which the adhesive substantially adheres.
A non-limiting example of a material to which the adhesive
substantially adheres is Teslin.TM. SP-1000, a synthetic sheet
material which is commercially available from PPG Industries, Inc,
Pittsburgh, Pa.
[0150] 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. No. 09/882,548 (now U.S. Pat. No.
6,656,241) and Ser. No. 09/882,549 (CIP published as U.S. Patent
Publication 2004-0067649), which were both filed on Jun. 14, 2001.
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.
[0151] 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.
[0152] 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.
[0153] 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 pad 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.
[0154] 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
[0155] 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 agitation. 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 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.
A layer of double-coated film tape with release liner was then
applied to the surface of the disk which was not grooved such that
the rectangular opening in the first layer was substantially
spanned by the tape. The film tape was commercially obtained from
3M as High Performance Double Coated Tape type 9500PC.
[0156] A stacked pad was constructed by mounting the polishing pad
assembly on a third layer of subpad with opening. 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.sub.3. Another double-coated
film tape with release liner was commercially obtained from
Adhesives Research, Inc. under the trade name ARclad 90334 was
applied to one surface of the polyurethane foam. A window opening
was then cut into the 20'' diameter foam pad and ARclad 90334 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 3M 9500PC on the polishing pad
assembly 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 three-layer stack assembly was then passed
through a calendar roll set. The adhesive on the upper and lower
sides of the second layer in the window area was removed by
contacting it with a 1/2.times.2'' rectangular piece of Teslin
SP-1000, commercially available from PPG Industries, Incorporated.
This was accomplished by pressing the piece by hand to ensure good
contact between the adhesive and the Teslin SP-1000, then peeling
away the Teslin SP-1000. The adhesive selectively adhered to the
Teslin SP-1000, leaving the substantially clear film of the window
free of adhesive. The resulting pad stack had a transparent
rectangular window having a size of 1/2.times.2''. The remaining
release liner on the subpad can be removed to permit attachment to
a commercial planarizing apparatus.
[0157] The descriptions set forth herein describe and explain the
principle, preferred construction, and mode of operation of the
invention, and illustrate and describe what is considered to
represent its best embodiments. However, it should be understood
that various changes in the details, materials, and arrangements of
parts or the method described herein may be made by those skilled
in the art within the principle and scope of the invention.
* * * * *