U.S. patent application number 11/492409 was filed with the patent office on 2007-02-15 for polishing pad having a sealed pressure relief channel.
Invention is credited to Charles C. Kuo, Jennifer M. O'Sullivan.
Application Number | 20070037487 11/492409 |
Document ID | / |
Family ID | 37743126 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070037487 |
Kind Code |
A1 |
Kuo; Charles C. ; et
al. |
February 15, 2007 |
Polishing pad having a sealed pressure relief channel
Abstract
The present invention provides a chemical mechanical polishing
pad comprising a window formed in the polishing pad, the window
having a void provided on a side thereof. The invention further
provides a pressure relief channel provided in the polishing pad
from the void to a periphery of the polishing pad. In addition, a
membrane is provided in the channel to prevent contamination of the
void.
Inventors: |
Kuo; Charles C.; (Westlake,
OH) ; O'Sullivan; Jennifer M.; (Wilmington,
DE) |
Correspondence
Address: |
ROHM AND HAAS ELECTRONIC MATERIALS;CMP HOLDINGS, INC.
451 BELLEVUE ROAD
NEWARK
DE
19713
US
|
Family ID: |
37743126 |
Appl. No.: |
11/492409 |
Filed: |
July 25, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60706873 |
Aug 10, 2005 |
|
|
|
Current U.S.
Class: |
451/6 ;
451/527 |
Current CPC
Class: |
B24B 37/205
20130101 |
Class at
Publication: |
451/006 ;
451/527 |
International
Class: |
B24B 49/00 20060101
B24B049/00; B24D 11/00 20060101 B24D011/00 |
Claims
1. A chemical mechanical polishing pad comprising: a window formed
in the polishing pad, the window having a void provided on a side
thereof; a pressure relief channel provided in the polishing pad
from the void to a periphery of the polishing pad; and a membrane
provided in the channel to prevent contamination of the void.
2. The polishing pad of claim 1 wherein the membrane is selected
from the group comprising polyester, polyethylene, polypropylene,
fluoropolymers, polyurethane foamed films, silicone, nylon, silk,
woven materials and polyethylene terephthalate.
3. The polishing pad of claim 2 wherein the membrane is
polytetrafluoroethylene.
4. The polishing pad of claim 3 wherein the membrane is expanded
polytetrafluoroethylene.
5. The polishing pad of claim 1 wherein the pressure relief channel
has a width between 0.70 mm to 6.50 mm.
6. The polishing pad of claim 5 wherein the width varies between
the void to the periphery of the polishing pad.
7. The polishing pad of claim 1 wherein the pressure relief channel
has a depth between 0.38 mm to 1.53 mm.
8. A chemical mechanical polishing pad comprising: a polishing
layer having a window formed therein, the window being exposed to a
void on a side thereof; a pressure relief channel provided in the
polishing layer from a portion of the void-exposed side of the
window to a periphery of the polishing layer; and a membrane
provided in the channel to prevent contamination of the void.
9. A chemical mechanical polishing pad comprising: a polishing
layer overlying a bottom layer, and an adhesive layer disposed
between the polishing layer and the bottom layer; a window formed
in the polishing layer, the window being exposed to a void on a
side thereof; a pressure relief channel provided in the adhesive
layer from the void to a periphery of the adhesive layer; and a
membrane provided in the channel to prevent contamination of the
void.
10. A chemical mechanical polishing pad comprising: a polishing
layer overlying a bottom layer, and an adhesive layer disposed
between the polishing layer and the bottom layer; a window formed
in the polishing layer, the window being exposed to a void on a
side thereof; a pressure relief channel provided in the bottom
layer from the void to a periphery of the bottom layer; and a
membrane provided in the channel to prevent contamination of the
void.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/706,873 filed Aug. 10, 2005.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to polishing pads for chemical
mechanical planarization (CMP), and in particular, relates to
polishing pads having reduced stress windows formed therein for
performing optical end-point detection. Further, the present
invention relates to polishing pads having a sealed pressure relief
channel to reduce stress on the windows and prevent contamination
of the window area.
[0003] In the fabrication of integrated circuits and other
electronic devices, multiple layers of conducting, semiconducting
and dielectric materials are deposited on or removed from a surface
of a semiconductor wafer. Thin layers of conducting,
semiconducting, and dielectric materials may be deposited by a
number of deposition techniques. Common deposition techniques in
modem processing include physical vapor deposition (PVD), also
known as sputtering, chemical vapor deposition (CVD),
plasma-enhanced chemical vapor deposition (PECVD), and
electrochemical plating (ECP).
[0004] As layers of materials are sequentially deposited and
removed, the uppermost surface of the wafer becomes non-planar.
Because subsequent semiconductor processing (e.g., metallization)
requires the wafer to have a flat surface, the wafer needs to be
planarized. Planarization is useful in removing undesired surface
topography and surface defects, such as rough surfaces,
agglomerated materials, crystal lattice damage, scratches, and
contaminated layers or materials.
[0005] Chemical mechanical planarization, or chemical mechanical
polishing (CMP), is a common technique used to planarize
substrates, such as semiconductor wafers. In conventional CMP, a
wafer carrier is mounted on a carrier assembly and positioned in
contact with a polishing pad in a CMP apparatus. The carrier
assembly provides a controllable pressure to the wafer, pressing it
against the polishing pad. The pad is moved (e.g., rotated)
relative to the wafer by an external driving force. Simultaneously
therewith, a chemical composition ("slurry") or other polishing
solution is provided between the wafer and the polishing pad. Thus,
the wafer surface is thus polished and made planar by the chemical
and mechanical action of the pad surface and slurry.
[0006] An important step in planarizing a wafer is determining an
end-point to the process. Accordingly, a variety of planarization
end-point detection methods have been developed, for example,
methods involving optical in-situ measurements of the wafer
surface. The optical technique involves providing the polishing pad
with a window for select wavelengths of light. A light beam is
directed through the window to the wafer surface, where it reflects
and passes back through the window to a detector (e.g., a
spectrophotometer). Based on the return signal, properties of the
wafer surface (e.g., the thickness of films) can be determined for
end-point detection.
[0007] Roberts, in U.S. Pat. No. 5,605,760, discloses a polishing
pad having a window formed therein. In Roberts, a window is cast
and inserted into a flowable polishing pad polymer. This polishing
pad may be utilized in a stacked configuration (i.e., with a
subpad) or used alone, directly adhered on the platen of a
polishing apparatus with an adhesive. In either case, there is a
"void" or space that is created between the window and the platen.
Unfortunately, during polishing, undue stress is applied to the
window from the pressure that is generated in the void and may
cause unwanted residual stress deformations (e.g., "bulges" or
"caving-in") in the window. These stress deformations may result in
non-planar windows and cause poor end-point detection, defectivity
and wafer slippage.
[0008] Hence, what is needed is a polishing pad having a reduced
stress window for robust end-point detection or measurement during
CMP over a wide range of wavelengths.
STATEMENT OF THE INVENTION
[0009] In a first aspect of the present invention, there is
provided a chemical mechanical polishing pad comprising: a window
formed in the polishing pad, the window having a void provided on a
side thereof; a pressure relief channel provided in the polishing
pad from the void to a periphery of the polishing pad; and a
membrane provided in the channel to prevent contamination of the
void.
[0010] In another aspect of the present invention, there is
provided a chemical mechanical polishing pad comprising: a
polishing layer having a window formed therein, the window being
exposed to a void on a side thereof; a pressure relief channel
provided in the polishing layer from a portion of the void-exposed
side of the window to a periphery of the polishing layer; and a
membrane provided in the channel to prevent contamination of the
void.
[0011] In another aspect of the present invention, there is
provided a chemical mechanical polishing pad comprising: a
polishing layer overlying a bottom layer, and an adhesive layer
disposed between the polishing layer and the bottom layer; a window
formed in the polishing layer, the window being exposed to a void
on a side thereof; a pressure relief channel provided in the
adhesive layer from the void to a periphery of the adhesive layer;
and a membrane provided in the channel to prevent contamination of
the void.
[0012] In another aspect of the present invention, there is
provided a chemical mechanical polishing pad comprising: a
polishing layer overlying a bottom layer, and an adhesive layer
disposed between the polishing layer and the bottom layer; a window
formed in the polishing layer, the window being exposed to a void
on a side thereof; a pressure relief channel provided in the bottom
layer from the void to a periphery of the bottom layer; and a
membrane provided in the channel to prevent contamination of the
void.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates a polishing pad having a pressure relief
channel of the present invention including a membrane;
[0014] FIG. 2A illustrates a sectional view along line I-II of the
polishing pad of FIG. 1;
[0015] FIG. 2B illustrates another embodiment of a sectional view
along line I-II of the polishing pad of FIG. 1;
[0016] FIG. 3 illustrates another embodiment of a polishing pad
having a pressure relief channel of the present invention;
[0017] FIG. 4 illustrates another embodiment of a polishing pad
having a pressure relief channel of the present invention; and
[0018] FIG. 5 illustrates a CMP system utilizing the polishing pad
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Referring now to FIG. 1, a polishing pad 1 of the present
invention is shown. Polishing pad 1 comprises a polishing layer 4
and an optional bottom layer 2. Note, polishing layer 4 and bottom
layer 2 may individually serve as a polishing pad. In other words,
the present invention may be utilized in the polishing layer 4
alone, or in the polishing layer 4 in conjunction with the bottom
layer 2, as a polishing pad. The bottom layer 2 may be made of
felted polyurethane, such as SUBA-IV.TM. pad manufactured by Rohm
and Haas Electronic Materials CMP Inc. ("RHEM"), of Newark, Del.
The polishing layer 4 may comprise a polyurethane pad (e.g., a pad
filled with microspheres), such as, IC 1000.TM. pad by RHEM.
Polishing layer 4 may optionally be texturized as desired. A thin
layer of pressure sensitive adhesive 6 may hold the polishing layer
4 and the bottom layer 2 together. The adhesive 6 may be
commercially available from 3M Innovative Properties Company of St,
Paul, Minn.
[0020] Polishing layer 4 has a transparent window 14 provided over
the bottom layer 2 and the pressure sensitive adhesive 6. Polishing
layer 4 may have a thickness T between 0.70 mm to 2.65 mm. Note,
window 14 is provided over the void 10 that creates a pathway for
the signal light utilized during end-point detection. Accordingly,
laser light from a laser spectrophotometer (not shown) may be
directed through the void 10 and transparent window block 14, and
onto a wafer or substrate to facilitate end-point detection. Note,
although the present invention is described with reference to a
polishing pad having an integrally formed window, the invention is
not so limited. For example, the entire polishing layer 4 may be
transparent ("clear pad") and the void, including pressure, may be
created at any point where, for example, the laser
spectrophotometer is placed. In other words, the present invention
is applicable to a window-less pad. Also, although the present
invention is described with respect to end-point detection through
a window 14 utilizing a laser spectrophotometer, the invention is
not so limited. For example, the polishing layer 4 may be suitably
adapted to accommodate other end-point detection methods, for
example, measuring the resistance across a polishing surface of the
wafer.
[0021] In an exemplary embodiment of the invention, polishing pad 1
comprises a pressure relief channel 11, including a membrane 12,
having an inlet 11a and an outlet 11b. The pressure relief channel
11 extends from a portion of the window 14, on side 14a that is
exposed to the pressure created in void 10, to a periphery 4a of
the polishing pad 1, in particular, a periphery 4a of the polishing
layer 4. Hence, pressure that is generated in the void 10 during
the polishing operation may be evacuated through the membrane 12,
and inlet 11a and outlet 11b of pressure relief channel 11. In
other words, any pressure that is generated in void 10 does not
materially affect the transparent window 14 since the pressure
escapes through the pressure relief channel 11. Therefore, the
transparent window 14 is not stressed or deformed due to the
pressure build-up and accurate end-pointing is facilitated. Note,
although the invention is described here as having a single
pressure relief channel, the invention is not so limited. For
example, there may be more than one pressure relief channel
provided in the polishing layer 4. Alternatively, a single or
multiple pressure relief channels may be provided in each of the
separate layers (i.e., the adhesive layer and the bottom layer) or
any combinations thereof without departing from the scope of the
invention. In addition, although the invention is described as
having a pressure relief channel that extends to the periphery of
the polishing pad, the invention is equally applicable to a
polishing pad having a pressure relief channel that extends from
the void 10 to the polishing surface of the polishing layer 4.
Alternatively, the polishing pad may have a pressure relief channel
(including membrane 12) that extends from the void 10, through the
window 14, to the polishing surface of the polishing layer 4.
[0022] Advantageously, membrane 12 prevents contamination (e.g.
slurry flow) through the channel and into the void area. Membrane
12 is impermeable to contaminants, for example, slurry, but allows
heat and pressure to escape from the void area and through the
channel. In essence, membrane 12 acts as a filter, allowing certain
undesired items to be released while preventing certain other
undesired items from entering.
[0023] Membrane 12 of the polishing pad of the present invention
may be manufactured from polyester, polyethylene, polypropylene,
fluoropolymers, polyurethane foamed films, silicone, nylon, silk,
woven materials and polyethylene terephthalate (PET), or any other
biocompatible material. In one embodiment of the present invention,
the membrane material is a fluoropolymer, in particular,
polytetrafluoroethylene (PTFE). More preferably, the membrane
material is expanded polytetrafluoroethylene (ePTFE) having a
node-fibril structure (e.g., GORE-TEX.RTM. membrane vents,
manufactured by W. L. Gore and Associates, Inc., Elkton, Md.).
Other commercially available membranes include modified acrylic
copolymer membranes (VERSAPOR.RTM. R membranes, manufactured by
Gelman Sciences, Ann Arbor, Mich.), modified polyvinylidene
fluoride (DURAPEL.RTM. membranes, manufactured by the Millipore
Corporation, Bedford, Mass.) and other microporous materials that
are commonly used to relieve pressure from enclosures.
[0024] The membrane used in the present invention may be
manufactured from thin films of ePTFE that are each approximately
0.0025 to 0.025 mm thick. From 1 to about 200 plys (layers) of
ePTFE film may be stacked up and laminated to one another to obtain
a membrane with the desired mechanical and structural properties.
An even number of layers are preferably stacked together (e.g., 2,
4, 6, 8, 10, etc.), with approximately 2 to 20 layers being
desirable. Cross-lamination occurs by placing superimposed sheets
on one another such that the film drawing direction, or stretching
direction, of each sheet is angularly offset by angles between 0
degrees and 180 degrees from adjacent layers or plies. Since the
base ePTFE is thin, as thin as 0.0025 mm thick, superimposed films
can be rotated relative to one another to improve the mechanical
properties of the membrane. In one embodiment of the present
invention the membrane is manufactured by laminating 8 plies of
ePTFE film, each film ply being 0.0125 mm thick. In another
embodiment of the present invention the membrane is manufactured by
laminating 4 plies of ePTFE film, each film ply being 0.0125 mm
thick. The laminated ePTFE sheets are then sintered together at
temperatures of about 370.degree. C., under vacuum to adhere the
film layers to one another.
[0025] Advantageously, the pressure relief channel 11 may be formed
by, for example, milling the channel utilizing a
computer-numerically controlled tool ("cnc tool"), laser cutting,
knife cutting, pre-molding the pad with the channel in place or
melting/burning the channel into the pad. Most preferably, the
pressure relief channel 11 is formed by milling or laser cutting
the channel. Thereafter, membrane 12 may be inserted into the
channel, as desired. Depending on the location of the channel
(i.e., polishing layer, adhesive layer or the bottom layer) the
membrane 12 may be provided in the channel 11 at various steps
during the manufacturing process of the polishing pad. In addition,
the membrane 12 may be located anywhere along the channel 11, as
desired.
[0026] Referring now to FIG. 2A, a sectional view along line I-II
of polishing layer 4 of FIG. 1 is provided. In this embodiment, the
pressure relief channel 11 has a semi-circular profile. Note,
however, that the particular shape of the profile of the pressure
relief channel 11 may be varied without departing from the scope of
the invention. For example, the profile of the pressure relief
channel 11 may be semi-square or semi-rectangular. In addition, the
pressure relief channel 11 has a predetermined width W and depth D.
Preferably, the width W is between 0.70 mm to 6.50 mm. More
preferably, the width W is between 0.80 mm to 4.00 mm. Most
preferably, the width W is between 0.85 mm to 3.50 mm. In addition,
the pressure relief channel 11 preferably has a depth D between
0.38 mm to 1.53 mm. More preferably, the depth D is between 0.50 mm
to 1.27 mm. Most preferably, the depth D is between 0.55 mm to 0.90
mm. Also, the width W and depth D may be varied along the length of
the pressure relief channel 11 to facilitate pressure evacuation.
For example, the width W may be narrower near the window 14 as
compared to the periphery 4a, creating a capillary action to
prevent slurry contamination.
[0027] Referring now to FIG. 2B, an alternative embodiment of the
pressure relief channel 11 of the present invention is provided.
Similar features as in FIG. 2A are denoted by the same numerals.
Here, the profile of the pressure relief channel 11 is
semi-rectangular. As discussed above with reference to FIG. 2A, the
pressure relief channel 11 has a predetermined width W and depth D.
In addition, the width W and depth D may be varied along the length
of the pressure relief channel 11 to facilitate pressure
evacuation.
[0028] Referring now to FIG. 3, there is provided another
embodiment of a polishing pad having a pressure relief channel of
the present invention. Similar features as in FIG. 1 are denoted by
the same numerals. Here, a polishing pad 3 is provided comprising a
pressure relief channel 31, having an inlet 31a and an outlet 31b,
formed in the adhesive 6. The pressure relief channel 31 extends
from the void 10, to a periphery 6a of the polishing pad 3. More
particularly, the pressure relief channel 31 extends from the void
10, to a periphery 6a of the adhesive 6. Hence, pressure that is
generated in the void 10 during the polishing operation may be
evacuated through inlet 31a and outlet 31b of pressure relief
channel 31. In other words, any pressure that is generated in void
10 does not materially affect the transparent window 14 since the
pressure escapes through the pressure relief channel 31. Therefore,
the transparent window 14 is not stressed or deformed due to the
pressure build-up and accurate end-pointing is facilitated,
including reduced defectivity and wafer slippage.
[0029] Referring now to FIG. 4, there is provided another
embodiment of a polishing pad having a pressure relief channel of
the present invention. Similar features as in FIG. 1 are denoted by
the same numerals. Here, a polishing pad 5 is provided comprising a
pressure relief channel 51, having an inlet 51a and an outlet 51b,
formed in the bottom layer 2. The pressure relief channel 51
extends from the void 10, to a periphery 2a of the polishing pad 5.
More particularly, the pressure relief channel 51 extends from the
void 10, to a periphery 2a of the bottom layer 2. Hence, pressure
that is generated in the void 10 during the polishing operation may
be evacuated through inlet 51a and outlet 51b of pressure relief
channel 51. In other words, any pressure that is generated in void
10 does not materially affect the transparent window 14 since the
pressure escapes through the pressure relief channel 51. Therefore,
the transparent window 14 is not stressed or deformed due to the
pressure build-up and accurate end-pointing is facilitated.
[0030] Accordingly, the present invention provides a chemical
mechanical polishing pad having reduced stress windows. In
addition, the present invention provides a chemical mechanical
polishing pad comprising, a window formed in the polishing pad, the
window having a void provided on a side thereof. The polishing pad
further comprises a pressure relief channel provided from the void
to a periphery of the polishing pad to relieve undue stress on the
window. In addition, a membrane is provided in the channel to
prevent contamination of the void. Also, the pressure relief
channel may be formed in the adhesive layer or the bottom layer.
Similarly, one or more pressure relief channels may be formed in
the polishing layer, adhesive layer and the bottom layer together
or any combination thereof.
[0031] Additionally, in an exemplary embodiment of the present
invention, the transparent material of window 14 is made from a
polyisocyanate-containing material ("prepolymer"). The prepolymer
is a reaction product of a polyisocyanate (e.g., diisocyanate) and
a hydroxyl-containing material. The polyisocyanate may be aliphatic
or aromatic. The prepolymer is then cured with a curing agent.
Preferred polyisocyanates include, but are not limited to, methlene
bis 4,4' cyclohexylisocyanate, cyclohexyl diisocyanate, isophorone
diisocyanate, hexamethylene diisocyanate,
propylene-1,2-diisocyanate, tetramethylene-1,4-diisocyanate,
1,6-hexamethylene-diisocyanate, dodecane-1,12-diisocyanate,
cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate,
cyclohexane-1,4-diisocyanate,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methyl
cyclohexylene diisocyanate, triisocyanate of hexamethylene
diisocyanate, triisocyanate of 2,4,4-trimethyl-1,6-hexane
diisocyanate, uretdione of hexamethylene diisocyanate, ethylene
diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate,
2,4,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane
diisocyanate, and mixtures thereof. The preferred polyisocyanate is
aliphatic. The preferred aliphatic polyisocyanate has less than 14%
unreacted isocyanate groups.
[0032] Advantageously, the hydroxyl-containing material is a
polyol. Exemplary polyols include, but are not limited to,
polyether polyols, hydroxy-terminated polybutadiene (including
partially/fully hydrogenated derivatives), polyester polyols,
polycaprolactone polyols, polycarbonate polyols, and mixtures
thereof.
[0033] In one preferred embodiment, the polyol includes polyether
polyol. Examples include, but are not limited to,
polytetramethylene ether glycol ("PTMEG"), polyethylene propylene
glycol, polyoxypropylene glycol, and mixtures thereof. The
hydrocarbon chain can have saturated or unsaturated bonds and
substituted or unsubstituted aromatic and cyclic groups.
Preferably, the polyol of the present invention includes PTMEG.
Suitable polyester polyols include, but are not limited to,
polyethylene adipate glycol, polybutylene adipate glycol,
polyethylene propylene adipate glycol, o-phthalate-1,6-hexanediol,
poly(hexamethylene adipate) glycol, and mixtures thereof. The
hydrocarbon chain can have saturated or unsaturated bonds, or
substituted or unsubstituted aromatic and cyclic groups. Suitable
polycaprolactone polyols include, but are not limited to,
1,6-hexanediol-initiated polycaprolactone, diethylene glycol
initiated polycaprolactone, trimethylol propane initiated
polycaprolactone, neopentyl glycol initiated polycaprolactone,
1,4-butanediol-initiated polycaprolactone, PTMEG-initiated
polycaprolactone, and mixtures thereof. The hydrocarbon chain can
have saturated or unsaturated bonds, or substituted or
unsubstituted aromatic and cyclic groups. Suitable polycarbonates
include, but are not limited to, polyphthalate carbonate and
poly(hexamethylene carbonate) glycol.
[0034] Advantageously, the curing agent is a polydiamine. Preferred
polydiamines include, but are not limited to, diethyl toluene
diamine ("DETDA"), 3,5-dimethylthio-2,4-toluenediamine and isomers
thereof, 3,5-diethyltoluene-2,4-diamine and isomers thereof, such
as 3,5-diethyltoluene-2,6-diamine,
4,4'-bis-(sec-butylamino)-diphenylmethane,
1,4-bis-(sec-butylamino)-benzene,
4,4'-methylene-bis-(2-chloroaniline),
4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) ("MCDEA"),
polytetramethyleneoxide-di-p-aminobenzoate, N,N'-dialkyldiamino
diphenyl methane, p,p'-methylene dianiline ("MDA"),
m-phenylenediamine ("MPDA"), methylene-bis 2-chloroaniline
("MBOCA"), 4,4'-methylene-bis-(2-chloroaniline) ("MOCA"),
4,4'-methylene-bis-(2,6-diethylaniline) ("MDEA"),
4,4'-methylene-bis-(2,3-dichloroaniline) ("MDCA"),
4,4'-diamino-3,3'-diethyl-5,5'-dimethyl diphenylmethane,
2,2',3,3'-tetrachloro diamino diphenylmethane, trimethylene glycol
di-p-aminobenzoate, and mixtures thereof. Preferably, the curing
agent of the present invention includes
3,5-dimethylthio-2,4-toluenediamine and isomers thereof. Suitable
polyamine curatives include both primary and secondary amines.
[0035] In addition, other curatives such as, a diol, triol,
tetraol, or hydroxy-terminated curative may be added to the
aforementioned polyurethane composition. Suitable diol, triol, and
tetraol groups include ethylene glycol, diethylene glycol,
polyethylene glycol, propylene glycol, polypropylene glycol, lower
molecular weight polytetramethylene ether glycol,
1,3-bis(2-hydroxyethoxy) benzene, 1,3-bis-[2-(2-hydroxyethoxy)
ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)
ethoxy]ethoxy}benzene, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, resorcinol-di-(beta-hydroxyethyl) ether,
hydroquinone-di-(beta-hydroxyethyl) ether, and mixtures thereof.
Preferred hydroxy-terminated curatives include
1,3-bis(2-hydroxyethoxy) benzene, 1,3-bis-[2-(2-hydroxyethoxy)
ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)
ethoxy]ethoxy}benzene, 1,4-butanediol, and mixtures thereof. Both
the hydroxy-terminated and amine curatives can include one or more
saturated, unsaturated, aromatic, and cyclic groups. Additionally,
the hydroxy-terminated and amine curatives can include one or more
halogen groups. The polyurethane composition can be formed with a
blend or mixture of curing agents. If desired, however, the
polyurethane composition may be formed with a single curing
agent.
[0036] In a preferred embodiment of the invention, window 14 may be
formed of, for example, polyurethanes, both thermoset and
thermoplastic, polycarbonates, polyesters, silicones, polyimides
and polysulfone. Example materials for window 14 include, but are
not limited to, polyvinyl chloride, polyacrylonitrile,
polymethylmethacrylate, polyvinylidene fluoride, polyethylene
terephthalate, polyetheretherketone, polyetherketone,
polyetherimide, ethylvinyl acetate, polyvinyl butyrate, polyvinyl
acetate, acrylonitrile butadiene styrene, fluorinated ethylene
propylene and perfluoralkoxy polymers.
[0037] Referring now to FIG. 5, a CMP apparatus 20 utilizing the
polishing pad of the present invention, including the pressure
relief channel with membrane 12 (not shown) is provided. Apparatus
20 includes a wafer carrier 22 for holding or pressing the
semiconductor wafer 24 against the polishing platen 26. The
polishing platen 26 is provided with pad 1, including window 14,
pressure relief channel 11 and membrane 12, of the present
invention. As discussed above, pad 1 has a bottom layer 2 that
interfaces with the surface of the platen 26, and a polishing layer
4 that is used in conjunction with a chemical polishing slurry to
polish the wafer 24. Note, although not pictured, any means for
providing a polishing fluid or slurry can be utilized with the
present apparatus. The platen 26 is usually rotated about its
central axis 27. In addition, the wafer carrier 22 is usually
rotated about its central axis 28, and translated across the
surface of the platen 26 via a translation arm 30. Note, although a
single wafer carrier is shown in FIG. 5, CMP apparatuses may have
more than one spaced circumferentially around the polishing platen.
In addition, a transparent hole 32 is provided in the platen 26 and
overlies the void 10 and the window 14 of pad 1. Accordingly,
transparent hole 32 provides access to the surface of the wafer 24,
via window 14, during polishing of the wafer 24 for accurate
end-point detection. Namely, a laser spectrophotometer 34 is
provided below the platen 26 that projects a laser beam 36 to pass
and return through the transparent hole 32 and high transmission
window 14 for accurate end-point detection during polishing of the
wafer 24.
[0038] Accordingly, the present invention provides a chemical
mechanical polishing pad having reduced stress windows. In
addition, the present invention provides a chemical mechanical
polishing pad comprising, a window formed in the polishing pad, the
window having a void provided on a side thereof. The polishing pad
further comprises a pressure relief channel provided from the void
to a periphery of the polishing pad to relieve undue stress on the
window. In addition, a membrane is provided in the channel to
prevent contamination of the void. Also, the pressure relief
channel may be formed in the adhesive layer or the bottom layer.
Similarly, one or more pressure relief channels may be formed in
the polishing layer, adhesive layer and the bottom layer together
or any combination thereof.
* * * * *