U.S. patent application number 12/778760 was filed with the patent office on 2011-11-17 for pad window insert.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Dominic J. Benvegnu, Boguslaw A. Swedek.
Application Number | 20110281510 12/778760 |
Document ID | / |
Family ID | 44912183 |
Filed Date | 2011-11-17 |
United States Patent
Application |
20110281510 |
Kind Code |
A1 |
Swedek; Boguslaw A. ; et
al. |
November 17, 2011 |
Pad Window Insert
Abstract
A polishing pad includes a polishing layer having a polishing
surface, an adhesive layer on a side of the polishing layer
opposite the polishing layer, and a solid light-transmitting window
extending through and molded to the polishing layer. The solid
light-transmitting window has an upper portion with a first lateral
dimension and a lower portion with a second lateral dimension that
is smaller than the first lateral dimension. A top surface of the
solid light-transmitting window coplanar with the polishing surface
and a bottom surface of the solid light-transmitting window
coplanar with a lower surface of the adhesive layer.
Inventors: |
Swedek; Boguslaw A.;
(Cupertino, CA) ; Benvegnu; Dominic J.; (La Honda,
CA) |
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
44912183 |
Appl. No.: |
12/778760 |
Filed: |
May 12, 2010 |
Current U.S.
Class: |
451/527 ;
51/296 |
Current CPC
Class: |
B24B 37/26 20130101;
B24B 37/013 20130101; B24B 37/16 20130101; B24B 37/205
20130101 |
Class at
Publication: |
451/527 ;
51/296 |
International
Class: |
B24D 11/00 20060101
B24D011/00; B24D 3/00 20060101 B24D003/00 |
Claims
1. A polishing apparatus, comprising: a platen having a planar
upper surface, a recess formed in the upper surface, the recess
having a bottom surface, and a passage connected to the lower
surface of the recess; a polishing pad comprising a polishing layer
a polishing surface, and underside and an aperture therethrough,
the aperture having a smaller lateral dimension than the recess,
the aperture aligned with the passage; and a solid
light-transmitting window having a first portion positioned at
least partially in the aperture in the polishing pad and a second
portion positioned at least partially in the recess in the platen,
the second portion having a larger lateral dimension than the first
portion and extending below the polishing layer, the second portion
of the window adhesively attached to an underside of the polishing
pad.
2. The polishing apparatus of claim 1, wherein the first portion of
the window plugs the aperture in the polishing pad.
3. The polishing apparatus of claim 2, wherein a top surface of the
first portion of the window is coplanar with the upper surface of
the platen.
4. The polishing apparatus of claim 1, wherein the bottom surface
of the recess is parallel with the upper surface of the platen.
5. The polishing apparatus of claim 1, wherein a lower surface of
the second portion of window contacts the lower surface of the
recess.
6. The polishing apparatus of claim 5, wherein the lower surface of
the second portion of window is not adhered to the lower surface of
the recess.
7. The polishing apparatus of claim 1, further comprising an
adhesive layer spanning the polishing layer.
8. The polishing apparatus of claim 7, wherein the adhesive layer
comprises a double-sided adhesive tape.
9. The polishing apparatus of claim 7, wherein the adhesive layer
abuts the polishing layer.
10. The polishing apparatus of claim 7, wherein the underside of
the polishing pad is adhesively attached to the upper surface of
the platen by the adhesive layer.
11. The polishing apparatus of claim 10, wherein a top surface of
the second portion of the window is adhesively attached to
underside of the polishing pad by the adhesive layer.
12. The polishing apparatus of claim 7, wherein a top surface of
the second portion of the window is adhesively attached to
underside of the polishing pad.
13. The polishing apparatus of claim 1, wherein the polishing pad
consists of the polishing layer.
14. The polishing apparatus of claim 1, wherein the polishing pad
consists of the polishing layer and a lower layer that is less
compressible than the polishing layer.
15. The polishing apparatus of claim 1, wherein the second portion
has a lateral dimension between two and ten times larger than the
first portion.
16. The polishing apparatus of claim 15, wherein the second portion
has a lateral dimension about 8 times larger than the first
portion.
17. The polishing apparatus of claim 1, wherein the second portion
of the window laterally fills the recess in the platen.
18. The polishing apparatus of claim 1, wherein the polishing pad
has a thickness less than 1 mm.
19. The polishing apparatus of claim 1, further comprising an
optical fiber in the passage and positioned to direct or receive
light through the first portion of the window.
20. The polishing apparatus of claim 19, wherein the optical fiber
is wider than the first portion of the window.
21. The polishing apparatus of claim 1, wherein sides of the recess
are sloped and sides of the second portion of the window are
sloped.
22. A method of assembling a window for a polishing apparatus,
comprising: forming an aperture through a polishing pad, the
polishing pad comprising a polishing layer having a polishing
surface and underside; forming a solid light-transmitting window
having a first portion and a second portion having a larger lateral
dimension than the first portion; inserting the first portion of
the window into the aperture of the pad; adhering a top surface of
the second portion of the window to the underside of the polishing
pad; and positioning the polishing pad and window on a platen such
that the second portion of the window fits into a recess in a
planar upper surface of the platen and the underside of the
polishing pad is adhered to the planar upper surface of the
platen.
23. The method of claim 22, wherein a layer of adhesive is formed
on the bottom of the polishing layer and a liner covers the
adhesive, a portion of the liner is removed around the aperture,
and the top surface of the second portion of the window contacts
the adhesive in the removed portion of the liner.
24. The method of claim 23, further comprising removing a remainder
of the liner before positioning the polishing pad on the platen
such that the adhesive adheres the underside of the polishing pad
to the planar upper surface of the platen.
Description
TECHNICAL FIELD
[0001] A polishing pad with a window, a system containing such a
polishing pad, and a process for making and using such a polishing
pad are described.
BACKGROUND
[0002] In the process of fabricating modern semiconductor
integrated circuits (IC), it is often necessary to planarize the
outer surface of the substrate. For example, planarization may be
needed to polish away a conductive filler layer until the top
surface of an underlying layer is exposed, leaving the conductive
material between the raised pattern of the insulative layer to form
vias, plugs and lines that provide conductive paths between thin
film circuits on the substrate. In addition, planarization may be
needed to flatten and thin an oxide layer to provide a flat surface
suitable for photolithography.
[0003] One method for achieving semiconductor substrate
planarization or topography removal is chemical mechanical
polishing (CMP). A conventional chemical mechanical polishing (CMP)
process involves pressing a substrate against a rotating polishing
pad in the presence of an abrasive slurry.
[0004] In general, there is a need to detect when the desired
surface planarity or layer thickness has been reached or when an
underlying layer has been exposed in order to determine whether to
stop polishing. Several techniques have been developed for the
in-situ detection of endpoints during the CMP process. For example,
an optical monitoring system for in-situ measuring of uniformity of
a layer on a substrate during polishing of the layer has been
employed. The optical monitoring system can include a light source
that directs a light beam toward the substrate during polishing, a
detector that measures light reflected from the substrate, and a
computer that analyzes a signal from the detector and calculates
whether the endpoint has been detected. In some CMP systems, the
light beam is directed toward the substrate through a window in the
polishing pad.
SUMMARY
[0005] A window can be attached to the underside of a polishing pad
such that a portion of the window rests in a recess in a platen.
This can permit a large surface area contact between the window and
the pad so as to increase bonding strength between the window and
the polishing pad.
[0006] In one aspect, a polishing apparatus includes a platen
having a planar upper surface, a recess formed in the upper
surface, the recess having a bottom surface, and a passage
connected to the lower surface of the recess, as well as a
polishing pad comprising a polishing layer, a polishing surface,
and underside and an aperture therethrough, the aperture having a
smaller lateral dimension than the recess, the aperture aligned
with the passage. A solid light-transmitting window has a first
portion positioned at least partially in the aperture in the
polishing pad and a second portion positioned at least partially in
the recess in the platen, the second portion having a larger
lateral dimension than the first portion and extending below the
polishing layer, the second portion of the window adhesively
attached to an underside of the polishing pad.
[0007] Implementations can include one or more of the following
features. The first portion of the window can plug the aperture in
the polishing pad. A top surface of the first portion of the window
can be coplanar with the upper surface of the platen. The bottom
surface of the recess can be parallel with the upper surface of the
platen. A lower surface of the second portion of window can contact
the lower surface of the recess. The lower surface of the second
portion of window may not be adhered to the lower surface of the
recess. The polishing apparatus can also include an adhesive layer
spanning the polishing layer. The adhesive layer can include a
double-sided adhesive tape. The adhesive layer can abut the
polishing layer. The underside of the polishing pad can be
adhesively attached to the upper surface of the platen by the
adhesive layer. A top surface of the second portion of the window
can be adhesively attached to underside of the polishing pad by the
adhesive layer. A top surface of the second portion of the window
can be adhesively attached to underside of the polishing pad. The
polishing pad can include the polishing layer. The polishing pad
can include the polishing layer and a lower layer that is less
compressible than the polishing layer. The second portion can have
a lateral dimension between two and ten times larger, e.g., about
eight times larger, than the first portion. The second portion of
the window can laterally fill the recess in the platen. The
polishing pad can have a thickness less than 1 mm. The polishing
apparatus can also include an optical fiber in the passage and
positioned to direct or receive light through the first portion of
the window. The optical fiber can be wider than the first portion
of the window. The sides of the recess can be sloped and sides of
the second portion of the window can be sloped.
[0008] In another aspect, method of assembling a window for a
polishing apparatus includes forming an aperture through a
polishing pad, the polishing pad comprising a polishing layer
having a polishing surface and underside, forming a solid
light-transmitting window having a first portion and a second
portion having a larger lateral dimension than the first portion,
inserting the first portion of the window into the aperture of the
pad, adhering a top surface of the second portion of the window to
the underside of the polishing pad, and positioning the polishing
pad and window on a platen such that the second portion of the
window fits into a recess in a planar upper surface of the platen
and the underside of the polishing pad is adhered to the planar
upper surface of the platen.
[0009] Implementations can include one or more of the following
features. A layer of adhesive can be formed on the bottom of the
polishing layer and a liner covers the adhesive, a portion of the
liner can be removed around the aperture, and the top surface of
the second portion of the window can contact the adhesive in the
removed portion of the liner.
[0010] Implementations may include the following potential
advantages. A strong bond can be formed between the window and a
thin polishing pad, reducing the likelihood of slurry leakage and
reducing the likelihood of the window being pulled from the pad due
to shear force from the substrate being polished. In addition, the
polishing pad can improve wafer-to-wafer uniformity of spectrum
reflected from the substrate, particularly at short
wavelengths.
[0011] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other aspects,
features and advantages will be apparent from the description and
drawings, and from the claims.
DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a cross-sectional view of a CMP apparatus
containing a polishing pad.
[0013] FIG. 2 is a top view of an embodiment of a polishing pad
with a window.
[0014] FIG. 3A is a cross-sectional view of the polishing pad of
FIG. 2 installed on a platen.
[0015] FIG. 3B is a cross-sectional view of the polishing pad of
FIG. 2.
[0016] FIGS. 4-7 illustrate a method of forming a polishing
pad.
[0017] FIG. 8 is a cross-sectional view of another implementation
the polishing pad installed on a platen.
[0018] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0019] A window can be attached to the underside of a polishing pad
such that a portion of the window rests in a recess in a platen.
This can permit a large surface area contact between the window and
the pad so as to increase bonding strength between the window and
the polishing pad.
[0020] As shown in FIG. 1, the CMP apparatus 10 includes a
polishing head 12 for holding a semiconductor substrate 14 against
a polishing pad 18 on a platen 16. The CMP apparatus may be
constructed as described in U.S. Pat. No. 5,738,574, the entire
disclosure of which is incorporated herein by reference.
[0021] The substrate can be, for example, a product substrate
(e.g., which includes multiple memory or processor dies), a test
substrate, a bare substrate, and a gating substrate. The substrate
can be at various stages of integrated circuit fabrication, e.g.,
the substrate can be a bare wafer, or it can include one or more
deposited and/or patterned layers. The term substrate can include
circular disks and rectangular sheets.
[0022] The effective portion of the polishing pad 18 can include a
polishing layer 20 with a polishing surface 24 to contact the
substrate and a bottom surface 22 secured to the platen 16 by an
adhesive layer 28, e.g., an adhesive tape. The adhesive 28 can be a
pressure-sensitive adhesive. Other than the adhesive tape and any
liner, the polishing pad can be, e.g., consist of, a single-layer
pad, with the polishing layer 20 formed of a thin durable material
suitable for a chemical mechanical polishing process. Thus, the
layers of the polishing pad can consist of the single-layer
polishing layer 20 and the adhesive layer 28 (and optionally a
liner, which would be removed when the pad is installed on the
polishing platen).
[0023] The polishing layer 20 can be, e.g., consist of, a foamed
polyurethane, with at least some open pores on the polishing
surface 24. The adhesive layer 28 can be a double-sided adhesive
tape, e.g., a thin layer of polyethylene terephthalate (PET), e.g.,
Mylar.RTM., with adhesive, e.g., pressure-sensitive adhesive, on
both sides. Such a polishing pad is available under the trade name
H7000HN from Fujibo in Tokyo, Japan.
[0024] Referring to FIG. 2, in some implementations the polishing
pad 18 has a radius R of 15.0 (381.00 mm) to 15.5 inches (393.70
mm), with a corresponding diameter of 30 to 31 inches. In some
implementations, the polishing pad 18 can have a radius of 21.0
(533.4 mm) to 21.5 inches (546.1 mm), with corresponding diameter
of 42 to 43 inches.
[0025] Referring to FIG. 3A, in some implementations, grooves 26
can be formed in the polishing surface 24. The grooves can be in a
"waffle" pattern, e.g., a cross-hatched pattern of perpendicular
grooves with sloped side walls that divide the polishing surface
into rectangular, e.g., square, areas.
[0026] Returning to FIG. 1, typically the polishing pad material is
wetted with the chemical polishing liquid 30, which can include
abrasive particles. For example, the slurry can include KOH
(potassium hydroxide) and fumed-silica particles. However, some
polishing processes are "abrasive-free".
[0027] The polishing head 12 applies pressure to the substrate 14
against the polishing pad 18 as the platen rotates about its
central axis. In addition, the polishing head 12 is usually rotated
about its central axis, and translated across the surface of the
platen 16 via a drive shaft or translation arm 32. The pressure and
relative motion between the substrate and the polishing surface, in
conjunction with the polishing solution, result in polishing of the
substrate.
[0028] An optical aperture 34 is formed in the top surface of the
platen 16. An optical monitoring system, including a light source
36, such as a laser, and a detector 38, such as a photodetector,
can be located below the top surface of the platen 16. For example,
the optical monitoring system can be located in a chamber inside
the platen 16 that is in optical communication with the optical
aperture 34, and can rotate with the platen. One or more optical
fibers 50 can carry light from the light source 36 to the
substrate, and from the substrate to the detector 38. For example,
the optical fiber 50 can be a bifurcated optical fiber, with a
trunk 52 in proximity, e.g., abutting, the window 40 in the
polishing pad, a first leg 54 connected to the light source 36, and
a second leg 56 connected to the detector 38.
[0029] The optical aperture 34 can be filled with a transparent
solid piece, such as a quartz block (in which case the fiber would
not abut the window 40 but could abut the solid piece in the
optical aperture), or it can be an empty hole. In one
implementation, the optical monitoring system and optical aperture
are formed as part of a module that fits into a corresponding
recess in the platen. Alternatively, the optical monitoring system
could be a stationary system located below the platen, and the
optical aperture could extend through the platen. The light source
36 can employ a wavelength anywhere from the far infrared to
ultraviolet, such as red light, although a broadband spectrum,
e.g., white light, can also be used, and the detector 38 can be a
spectrometer.
[0030] A solid window 40 is formed in the overlying polishing pad
18 and aligned with the optical aperture 34 in the platen. The
window 40 and aperture 34 can be positioned such that they have a
view of the substrate 14 held by the polishing head 12 during at
least a portion of the platen's rotation, regardless of the
translational position of the head 12.
[0031] The light source 36 projects a light beam through the
aperture 34 and the window 40 to impinge the surface of the
overlying substrate 14 at least during a time when the window 40 is
adjacent the substrate 14. Light reflected from the substrate forms
a resultant beam that is detected by the detector 38. The light
source and the detector are coupled to an unillustrated computer
that receives the measured light intensity from the detector and
uses it to determine the polishing endpoint, e.g., by detecting a
sudden change in the reflectivity of the substrate that indicates
the exposure of a new layer, by calculating the thickness removed
from of the outer layer (such as a transparent oxide layer) using
interferometric principles, by monitoring the spectrum of the
reflected light and detecting a target spectrum, by matching a
sequence of measured spectra to reference spectra from a library
and determining where a linear function fit to index values of the
reference spectrum reaches a target value, or by otherwise
monitoring the signal for predetermined endpoint criteria.
[0032] One problem with placement of a normal large rectangular
window (e.g., a 2.25 by 0.75 inch window) into a very thin
polishing layer is delamination during polishing. In particular,
the lateral frictional force from the substrate during polishing
can be greater than the adhesive force of the molding of the window
to the sidewall of the pad.
[0033] Returning to FIG. 2, the window 40 can be small, e.g., less
than about 3 mm in diameter, e.g., so as to reduce the frictional
force applied by the substrate during polishing. For example, the
upper portion of the window 40 can be a circular area about 3 mm
wide centered a distance D of about 7.5 inches (190.50 mm) from the
center of a 30 to 31 inch diameter polishing pad 18, or centered a
distance D of about 9 to 11 inches from the center of a 42 to 43
inch diameter polishing pad 18.
[0034] The window 40 can have an approximately circular shape
(other shapes are possible, such as rectangular). If the window is
elongated, its longer dimension can be substantially parallel to
the radius of the polishing pad that passes through the center of
the window. The window 40 can have a ragged perimeter 42, e.g., the
perimeter can be longer than a perimeter of a similarly shaped
circle or rectangle, e.g., a zig-zag or other meandering pattern
(in a top view). This increases the surface area for contact of the
window to the sidewall of the polishing pad, and can thereby
improve adhesion of the window to the polishing pad.
[0035] Referring to FIG. 3A, the window 40 includes an upper
portion 40a and a lower portion 40b. The window 40, including the
upper portion 40a and lower portion 40b, can be a unitary
single-piece body of homogeneous material. The upper portion 40a is
vertically aligned with the lower portion 40b but is laterally
smaller (i.e., in one or both directions parallel to the polishing
surface) than the lower portion 40b. Thus, a portion of the
polishing layer 20 projects above the lower portion 40b so that the
rim of the lower portion 40b that projects beyond the upper portion
40a forms a ledge 49. The lower portion 40b can project laterally
beyond the upper portion 40a on all sides of the window 40, or
optionally the lower portion 40b can project laterally beyond the
upper portion 40a on two opposing sides of the window 40 but be
aligned along other sides of the window 40. The upper surface of
the lower portion 40b that projects beyond the upper portion 40a
can be a substantially planar surface. The upper portion 40a can be
located in the center of, e.g., be concentric with, the lower
portion 40b. The lower portion 40b can have a lateral dimension 2
to 10 times, e.g., about 8 times, as large as the lateral dimension
of the upper portion 40a. For example, if the window 40 is
circular, the upper portion 40a can have a diameter of 3 mm, and
the lower portion 40b can have a diameter of 25 mm.
[0036] The upper portion 40a can be about the same thickness as the
lower portion 40b. Alternatively, the upper portion 40a can be
thicker than, or be thinner than, the lower portion 40b.
[0037] The upper portion 40a of the window 40 can project into an
aperture in the adhesive layer 28. The edge of the adhesive layer
28, e.g., adhesive tape, can abut the sides of the upper portion
40a of the window 40. The lower portion 40b of the window can
project into a recess 78 in the top surface 76 of the platen
16.
[0038] The upper portion 40a of the window is as thick as the
combination of the polishing layer 20 and the adhesive layer 28. A
top surface 44 of the upper portion 40a of the window 40 is
coplanar with the polishing surface 24. A bottom of the upper
portion 40a of the window 40 can be coplanar with a bottom surface
of the adhesive layer 28.
[0039] The upper surface of the lower portion 40b is secured to the
underside of the polishing layer 20 by a portion of the adhesive
layer 28. Optionally the perimeter of the upper portion 40a of the
window 40 can be secured to the inner sidewall edges 48 of the
polishing layer 20, e.g., by additional adhesive.
[0040] The increased surface area of connection between the window
40 and the polishing layer 20 provided by the connection on the
ledge 49 can provide a strong bond, reducing the likelihood of
slurry leakage and reducing the likelihood of the window 40 being
pulled from the polishing pad 18 due to shear force from the
substrate being polished. The trunk 52 of the optical fiber abuts
or nearly abuts the lower portion 40b. In some implementations, the
trunk 52 may be wider than the upper portion 40a of the window
40.
[0041] The bottom surface of the lower portion 40b of the window
can abut, e.g., rests on, without being adhesively or otherwise
secured to the bottom of the recess 78 in the upper surface 76 of
the platen 16. In some implementations, the lower portion 40b of
the window fills the recess 78.
[0042] Referring to FIG. 3B, before installation on the platen 16,
the polishing pad 18 can also include a liner 70 that spans the
adhesive layer 28 on the bottom surface 22 of the polishing pad 18,
except in the region covered by the adhesive lower portion 40b of
the window 40. The liner 70 can be a thin flexible material, e.g.,
paper, with a release coating so that it can be peeled away from
the adhesive 28. In some implementations, the liner can be an
incompressible and generally fluid-impermeable layer, for example,
polyethylene terephthalate (PET), e.g., Mylar.RTM.. In use, the
liner 70 is manually peeled from the adhesive layer 28, and the
polishing layer 20 is applied to the platen 16 with the adhesive
layer 28. The liner 70, however, does not span the window 40, but
is removed in and immediately around the region of the lower
portion 40b of the window 40, e.g., in a region about 25 cm across,
to form a hole 72 into which the lower portion 40b of the window 40
fits.
[0043] The polishing pad 18 is very thin, e.g., less than 2 mm,
e.g., less than 1 mm. For example, the total thickness of the
polishing layer 20, adhesive 28 and liner 70 can be about 0.8 or
0.9 mm. The polishing layer 20 can be about 0.7 or 0.8 mm thick,
with the adhesive 28 and the liner 70 providing about another 0.1
mm. The grooves 26 can be about half the depth of the polishing
pad, e.g., roughly 0.5 mm.
[0044] To manufacture the polishing pad, initially the polishing
layer 20 is formed and the bottom surface of the polishing layer 20
is covered with the pressure sensitive adhesive 28 and a liner 70,
as shown by FIG. 4. Grooves 26 can be formed in the polishing layer
20 as part of a pad molding process before attachment of the
pressure sensitive adhesive 28, or cut into the polishing layer 20
after the pad is formed. The grooves 26 can be formed before or
after the liner 70 is attached.
[0045] Referring now to FIG. 5, in some implementations the window
40 may be formed by casting and curing a polymer in the shape of
the window 40. In one implementation, the polymer is a mixture of 2
parts Calthane A 2300 and 3 parts Calthane B 2300 (available from
Cal Polymers, Inc. of Long Beach, Calif.). The liquid polymer
mixture can be degassed, e.g., for 15-30 minutes, before being
placed into the aperture. The polymer can be cured at room
temperature for about 24 hours, or a heat lamp or oven can be used
to decrease cure time. In some implementations, the polymer can be
poured into a mold and cured or otherwise solidified to form the
window 40 in its final shape. In some implementations, the window
40 can cured in a large solid block, and then can be formed by
machining the solid block of polymer to form the final shape of the
window 40.
[0046] In some implementations, a sidewall 84 of the lower portion
40b may be substantially perpendicular to the bottom surface 46 of
the window 40. In some implementations, the sidewall 84 may be
formed at an angle to the bottom surface 46, as will be discussed
further in the description of FIG. 7.
[0047] A hole 82 is punched through the entire polishing pad 18,
including the polishing layer 20, the adhesive 28 and the liner 70.
The hole 82 is sized to accommodate the upper portion 40a of the
window 40. In some implementations, the upper portion 40a
substantially plugs the hole 82 of the polishing pad 18. The hole
82 can be punched from the top (i.e., the side with the polishing
surface) of the pad, e.g., by a machine press. This permits the
position of the hole 82 to be positioned and sized with a high
degree of accuracy and repeatability.
[0048] A portion 72 of the liner 70 is peeled away or otherwise
removed from the adhesive layer 28. The liner 70 need not be peeled
of the polishing pad 18 entirely at this time. The portion 72 of
the liner 70 that is peeled away exposes a portion of a bottom
surface 22 of the adhesive layer 28 around the hole 82. The portion
72 that is peeled off can also be cut away, e.g., in a region sized
to accommodate the ledge 49 of the bottom portion 40b of the window
40, although this step can be performed at a later time.
[0049] Referring to FIGS. 5 and 6, the window 40 is secured to the
polishing pad 18 such that the upper portion 40a extends into the
hole 82, and the upper surface of the bottom portion 40b (e.g., the
ledge 49) contacts the adhesive layer 28. In some embodiments, the
upper portion 40a is sized to extend substantially through and
substantially fill the hole 82 such that the upper surface 44 is
coplanar with the polishing surface 24 of the polishing layer 20
when the ledge 49 is adhered to the adhesive layer 28.
[0050] In addition to the liner 70, an optional window backing
piece 74 can be placed to span the window 40. For example, the
window backing piece 74 can be secured to a portion of the adhesive
layer 28 immediately around the window 40. The backing piece 74 can
be the same thickness as the liner 70, or thinner than the liner
70. The backing piece 74 can be polytetrafluoroethylene (PTFE),
e.g., Teflon.RTM., or another non-stick material. The combined
polishing pad 18 and window 40 can then be readied for shipment to
the customer, e.g., in a sealed plastic bag.
[0051] Referring now to FIG. 7, when the customer receives the
combined polishing pad 18 and window 40, the customer can remove
the liner 70 (and window backing piece 74 if present) and then
attach the polishing pad 18 on the platen 16 using the adhesive
layer 28. The lower portion 40b of the window 40 is inserted into a
recess 78 in the upper surface 76 of the platen 16. In some
methods, the liner 70 can be peeled away partially in an area
around the window 40, the lower portion 40b of the window 40 is
inserted into the recess, and then the remainder of the liner is
peeled away and the rest of the polishing pad is secured to the
platen 16.
[0052] The lower portion 40b can be shaped and sized to
substantially fill the recess 78, for example, the sidewall 84 of
the lower portion 40b can contact substantially all of a sidewall
86 of the recess 78, and the bottom surface 46 of the window 40
substantially contacts a floor 88 of the recess 78 while the upper
surface 76 of the platen 16 contacts the adhesive layer 28.
[0053] In some implementations, the floor 88 of the recess 78 may
be substantially parallel with the upper surface 76 of the platen
16. In some implementations, the sidewall 84 of the lower portion
40b is perpendicular to the bottom surface 46, and the sidewall 86
of the recess 78 is perpendicular to the polishing surface 75.
Referring to FIG. 8, in some implementations, the sidewall 84 of
the lower portion 40b may be formed at a non-perpendicular angle,
e.g., between 20.degree. and 80.degree., e.g., 45.degree., to the
bottom surface 46, and the sidewall 86 of the recess 78 may be
formed at a substantially similar angle such that the sidewall 84
and the sidewall 86 substantially contact each other when the lower
portion 40b is inserted into the recess 78. For example, the
sidewall 84 may slope inward from the ledge 49 to the bottom
surface 46, such that the lower portion 40b forms a conic section.
Similarly, the sidewall 86 may be formed to mate with the conic
section. As such, the sloped sidewall 84 may cause the window 40
and the polishing pad 18 to exhibit a self-centering property as
the window 40 is inserted into the recess 78 within the sloped
sidewall 86.
[0054] As such, the polishing pad 18 is adhered to the platen 16 by
the adhesive layer 28, thereby retaining the window 40 within the
recess 78 in the platen 16. The window 40 can be vertically
supported by the floor 88 of the recess 78 and can be retained
laterally by the sidewalls 86 of the recess 78. The window 40 can
be adhered to the polishing pad by the contact of the top surface
of the ledge 49 to the same adhesive layer that secures the
underside of the polishing pad to the platen 16.
[0055] While certain embodiments have been described, the invention
is not so limited. For example, although a window with a simple
circular shape is described, the window could be more complex, such
as a rectangle, oval or star. The top portion of the window can
project past one or more sides of the bottom portion. It will be
understood that various other modifications may be made without
departing from the spirit and scope of the invention. Accordingly,
other embodiments are within the scope of the following claims.
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