U.S. patent application number 11/707569 was filed with the patent office on 2007-08-23 for dechuck using subpad with recess.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Anand N. Iyer, Garlen C. Leung, Peter McReynolds, Gregory E. Menk, Gopalakrishna B. Prabhu, Erik S. Rondum, Steven M. Zuniga.
Application Number | 20070197132 11/707569 |
Document ID | / |
Family ID | 38549354 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070197132 |
Kind Code |
A1 |
Menk; Gregory E. ; et
al. |
August 23, 2007 |
Dechuck using subpad with recess
Abstract
A method is described. The method includes supporting a
polishing sheet having a polishing surface on a subpad having a
recess formed therein, applying a vacuum to the recess sufficient
to pull portions of the polishing sheet into the recess to induce a
recess in the polishing surface, positioning a substrate in a
carrier head over the recess in the polishing surface, and lifting
the substrate away from the polishing surface while the substrate
is positioned over the recess.
Inventors: |
Menk; Gregory E.;
(Pleasanton, CA) ; Zuniga; Steven M.; (Soquel,
CA) ; Rondum; Erik S.; (San Ramon, CA) ;
McReynolds; Peter; (San Mateo, CA) ; Prabhu;
Gopalakrishna B.; (San Jose, CA) ; Leung; Garlen
C.; (San Jose, CA) ; Iyer; Anand N.; (Santa
Clara, CA) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
38549354 |
Appl. No.: |
11/707569 |
Filed: |
February 15, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60773950 |
Feb 15, 2006 |
|
|
|
Current U.S.
Class: |
451/5 ;
451/11 |
Current CPC
Class: |
B24B 21/04 20130101;
B24B 37/26 20130101; B24B 21/12 20130101; B24D 11/001 20130101;
B24B 37/12 20130101; B24B 21/06 20130101; B24B 37/205 20130101 |
Class at
Publication: |
451/005 ;
451/011 |
International
Class: |
B24B 51/00 20060101
B24B051/00 |
Claims
1. A polishing apparatus, comprising: a platen; a subpad on the
platen to support a polishing sheet having a polishing surface, the
subpad having a recess formed therein; a vacuum source connected to
the recess of the subpad and configured to apply a vacuum
sufficient to pull portions of the polishing sheet into the recess
of the subpad to induce a recess in the polishing surface; a
carrier head to hold a substrate against the polishing surface and
to lift the substrate away from the polishing surface; a motor to
move the carrier head across the polishing surface; and a
controller coupled to the carrier head and the motor and configured
to position the substrate over the recess in the polishing surface
and cause the carrier head to lift the substrate away from the
polishing surface.
2. The polishing apparatus of claim 1, wherein the platen is
rotatable.
3. The polishing apparatus of claim 1, further comprising a drive
mechanism to incrementally advance the polishing sheet in a linear
direction across the platen.
4. The polishing apparatus of claim 1, wherein the controller is
configured to position the substrate away from the recess during
polishing of the substrate.
5. The polishing apparatus of claim 1, wherein the recess comprises
a groove.
6. The polishing apparatus of claim 1, further comprising the
polishing sheet.
7. The polishing apparatus of claim 6, wherein the subpad is more
compressible than the polishing sheet.
8. A method of operating a polishing apparatus, comprising:
supporting a polishing sheet having a polishing surface on a subpad
having a recess formed therein; applying a vacuum to the recess
sufficient to pull portions of the polishing sheet into the recess
to induce a recess in the polishing surface; positioning a
substrate in a carrier head over the recess in the polishing
surface; and lifting the substrate away from the polishing surface
while the substrate is positioned over the recess.
9. The method of claim 8, further rotating a platen supporting the
polishing sheet to rotate the polishing sheet.
10. The method of claim 8, further comprising incrementally
advancing the polishing sheet in a linear direction relative to the
subpad.
11. The method of claim 8, wherein the recess comprises a groove.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/773,950, filed Feb. 15, 2006, which is hereby
incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] This invention relates to manufacturing semiconductor
devices.
BACKGROUND
[0003] The present invention relates to apparatus and methods for
chemical mechanical polishing a substrate.
[0004] An integrated circuit is typically formed on a substrate by
the sequential deposition of conductive, semiconductive or
insulative layers on a silicon wafer. One fabrication step involves
depositing a filler layer over a patterned stop layer, and
planarizing the filler layer until the stop layer is exposed. For
example, trenches or holes in an insulative layer may be filled
with a conductive layer. After planarization, the portions of the
conductive layer remaining between the raised pattern of the
insulative layer form vias, plugs and lines that provide conductive
paths between thin film circuits on the substrate.
[0005] Chemical mechanical polishing (CMP) is one accepted method
of planarization. This planarization method typically requires that
the substrate be mounted on a carrier or polishing head. The
exposed surface of the substrate is placed against a rotating
polishing pad. The polishing pad may be either a standard pad or a
fixed-abrasive pad. A standard pad has a durable roughened surface,
whereas a fixed-abrasive pad has abrasive particles held in a
containment media. The carrier head provides a controllable load,
i.e., pressure, on the substrate to push it against the polishing
pad. A polishing slurry, including at least one chemically-reactive
agent, and abrasive particles if a standard pad is used, is
supplied to the surface of the polishing pad.
[0006] An effective CMP process not only provides a high polishing
rate, but also provides a substrate surface which is finished
(lacks small-scale roughness) and flat (lacks large-scale
topography). The polishing rate, finish and flatness are determined
by the pad and slurry combination, the relative speed between the
substrate and pad, and the force pressing the substrate against the
pad. The polishing rate sets the time needed to polish a layer,
which in turn sets the maximum throughput of the CMP apparatus.
SUMMARY
[0007] In one aspect, a polishing article is described. The
polishing article includes a linear polishing sheet having a linear
transparent portion, wherein the linear transparent portion is
formed from a material that has the flexibility to pass around a
radius of about 2.5 inches without cracking.
[0008] Implementations of the invention may include one or more of
the following features. A top surface of the polishing sheet can be
substantially planar with a top surface of the linear transparent
portion. The linear transparent portion can be formed from a
polyurethane material. The material can have a hardness of about 60
on the Shore D scale. The material can have a thickness of about 50
mils. A top surface of the linear polishing sheet can be formed
from a material that is sufficiently durable to withstand
conditioning by a diamond-coated conditioning tool. A top surface
of the linear polishing sheet can be formed from a non-fixed
abrasive polishing material. The linear polishing sheet can include
a top layer and a bottom layer. The linear polishing sheet can
include a bonding layer between the lop layer and the bottom layer.
The polishing sheet can include a polishing layer, and the
transparent portion is molded to the polishing layer.
[0009] In another aspect, a polishing cartridge is described. The
polishing cartridge includes two rollers, a feed roller and a
take-up roller, and a linear polishing sheet, wherein a first end
of the linear polishing sheet is wrapped around the feed roller and
a second end of the linear polishing sheet is wrapped around the
take-up roller.
[0010] In one aspect, a polishing apparatus is described. The
polishing apparatus includes a rotatable platen, a drive mechanism
to incrementally advance a polishing sheet having a polishing
surface in a linear direction across the platen, a subpad on the
platen to support the polishing sheet, the subpad having a groove
formed therein, and a vacuum source connected to the groove of the
subpad and configured to apply a vacuum sufficient to pull portions
of the polishing sheet into the groove of the subpad to induce a
groove in the polishing surface.
[0011] Implementations of the invention may include one or more of
the following features. The subpad can include multiple grooves.
The grooves can form concentric circles, concentric ovals, or a
spiral. The grooves can form parallel lines or perpendicular lines.
The polishing apparatus can include the polishing sheet. The
polishing sheet can have multiple grooves in a polishing surface.
The polishing sheet can have a width and a length, wherein the
length is greater than the width, and the multiple grooves formed
in the polishing sheet can include grooves extending substantially
perpendicular to the length of the polishing sheet. The multiple
grooves formed in the polishing sheet can include grooves extending
substantially parallel to the length of the polishing sheet. The
subpad can be more compressible than the polishing sheet. The
subpad can be compressible.
[0012] In another aspect, a method is described. The method
includes supporting a polishing sheet having a polishing surface on
a subpad having a groove formed therein, and applying a vacuum to
the groove sufficient to pull portions of the polishing sheet into
the groove to induce a groove in the polishing surface.
[0013] Implementations of the invention may include one or more of
the following features. The method can include rotating a platen
supporting the polishing sheet to rotate the polishing sheet. The
method can include bringing a substrate into contact with the
polishing sheet and polishing the substrate. The method can include
releasing the polishing sheet from the platen, and incrementally
advancing the polishing sheet in a linear direction across the top
surface of the platen. The subpad can include multiple grooves. The
grooves can form concentric circles, concentric ovals, or a
spiral.
[0014] In one aspect, a polishing system is described. The
polishing system includes a polishing layer, and a subpad
supporting the polishing layer, the subpad having a spiral groove
formed therein.
[0015] Implementations of the invention may include one or more of
the following features. The subpad can be formed of multiple layers
of materials. The subpad can include an upper layer of polyurethane
material and a lower layer of foam. The upper layer can have a
thickness between about 60 mils and 100 mils and the lower layer
has a thickness of between about 40 mils and 60 mils. The spiral
groove can have a depth of between about 35 mils and 40 mils. The
groove can extend entirely through an upper layer of the subpad.
The subpad can have a thickness of about 150 mils. The spiral
groove can have a depth of about 50 mils and a width of about 500
mils. The subpad can include multiple spiral grooves, and each
spiral groove can originate from the center of the subpad. The
subpad can be more compressible than the polishing layer.
[0016] In another aspect, a polishing system is described. The
polishing system includes a rotatable platen, a drive mechanism to
incrementally advance a polishing sheet in a linear direction
across the platen, and a subpad on the platen to support the
polishing sheet, where the subpad has a spiral groove formed
therein.
[0017] Implementations of the invention may include one or more of
the following features. The polishing system can include a motor to
rotate the platen and a controller to control the motor, where the
controller can be configured to cause the platen to rotate in a
direction of increasing radius of the spiral groove. The controller
can be configured to cause the platen to rotate in a direction of
decreasing radius of the spiral groove.
[0018] In one aspect, a polishing system is described. The
polishing system includes a polishing layer having a polishing
surface with a first groove pattern, and a subpad supporting the
polishing layer, where the subpad has a second groove pattern
different than the first groove pattern.
[0019] In another aspect, a polishing article is described. The
polishing article includes an elongated polishing layer, and a
transparent carrier layer supporting the polishing layer, where the
transparent carrier layer has a projection extending into an
aperture in the polishing layer to provide a transparent window in
the polishing layer.
[0020] Implementations of the invention may include one or more of
the following features. The carrier layer can be integral with the
transparent window. The carrier layer and the transparent window
can be composed of a polymer material. The elongated polishing
layer can have a length and a width, and the projection can be
elongated in a direction parallel to the length. The window can
extend substantially the entire length of the polishing layer. The
polishing layer and the carrier layer can be adhered or welded
together. An exposed surface of the transparent window can be
substantially co-planar with an exposed surface of the polishing
layer. Two sides of the projection can contact adjacent sides of
the polishing layer. The carrier layer can extend across a width of
the polishing layer. The carrier layer and the projection can not
have a seam at the junction of the carrier layer and the
projection.
[0021] In one aspect, a method is described. The method includes
forming a polishing layer over a carrier layer having a raised
transparent portion, wherein the transparent portion is not covered
by the polishing layer.
[0022] Implementations of the invention may include one or more of
the following features. Forming the polishing layer with the raised
transparent portion can include one or more of molding, extruding,
casting, shaping with pinch rollers, ablating, or mechanical
milling. Forming a polishing layer over the carrier layer can
include forming grooves in an upper surface of the polishing layer.
The method can include drying or curing the carrier layer before
forming the polishing layer over the carrier layer.
[0023] In another aspect, a method is described. The method
includes forming a carrier layer with a raised transparent portion
that projects into an aperture of a polishing layer, wherein the
transparent portion is not covered by the polishing layer.
[0024] Implementations of the invention may include one or more of
the following features. Forming the carrier layer can include
fabricating an integral piece comprising a carrier portion and the
raised transparent portion, the raised transparent portion
providing a transparent window in the polishing layer, wherein the
carrier portion can be exposed on a main surface and can be covered
by the polishing layer on an opposite surface to the main surface
and the transparent window can be exposed on both a surface
substantially co-planar with a surface of the polishing layer and a
surface substantially co-planar with the main surface of the
carrier portion. Fabricating the piece can include removing
polishing layer material covering the transparent window. Forming
the carrier layer can include one or more of molding, extruding,
casting, shaping with pinch rollers, ablating, or mechanical
milling. The method can include drying or curing the polishing
layer before fabricating the carrier layer on the polishing
layer.
[0025] In one aspect, a method is described. The method includes
contacting a non-solid material to a non-linear edge of a sheet of
polishing material, and causing the non-solid material to solidify
to form a window that contacts the non-linear edge of the polishing
material.
[0026] Implementations of the invention may include one or more of
the following features. The method can include contacting the
non-solid material to a non-linear second edge of a second sheet of
polishing material and causing the non-solid material to solidify
to form a window that contacts the second non-linear edge of the
second sheet of polishing material. The method can include
supporting the first sheet and the second sheet with a gap there
between and depositing the non-solid material into the gap. The
window can extend substantially an entire length of the polishing
article. Contacting a non-solid material to the edge of the sheet
of polishing material and the second edge of the second sheet of
polishing material can include pouring a liquid precursor material
between the edge and the second edge. The solidified liquid
precursor material can form multiple projections which interlock
with projections of the polishing material. The window can extend
along a primary axis. The non-linear edge can include multiple
projections normal to the primary axis. Causing the non-solid
material to solidify can form a window that fits into the sheet
with a dovetail-like joint. An exposed surface of the window and an
exposed surface of the polishing material can be substantially
co-planar. The sheet of polishing material can be formed by cutting
the sheet of polishing material or skiving the sheet from a block
of polishing material. The window can extend a length of the
polishing sheet between the edge of the polishing sheet and the
center of the polishing sheet.
[0027] In another aspect, a polishing article is described. The
polishing article includes a polishing sheet, and a solid
light-transmissive window in the polishing sheet having a primary
axis and a non-linear edge that extends parallel to the primary
axis.
[0028] Implementations of the invention may include one or more of
the following features. The polishing sheet can be elongated with a
length and a width, where the length is greater than the width, and
the primary axis is parallel to the length. The window can extend
substantially the entire length of the polishing sheet. The
non-linear edge can include multiple projections normal to the
primary axis. The multiple projections can interlock with
projections of the polishing material. The window can fit into the
sheet with a dovetail-like joint. An exposed surface of the window
and an exposed surface of the polishing material can be
substantially co-planar.
[0029] In one aspect, a polishing apparatus is described. The
polishing apparatus includes a platen, a subpad on the platen to
support a polishing sheet having a polishing surface, the subpad
having a recess formed therein, a vacuum source connected to the
recess of the subpad and configured to apply a vacuum sufficient to
pull portions of the polishing sheet into the recess of the subpad
to induce a recess in the polishing surface, a carrier head to hold
a substrate against the polishing surface and to lift the substrate
away from the polishing surface, a motor to move the carrier head
across the polishing surface, and a controller coupled to the
carrier head and the motor and configured to position the substrate
over the recess in the polishing surface and cause the carrier head
to lift the substrate away from the polishing surface.
[0030] Implementations of the invention may include one or more of
the following features. The platen can be rotatable. The polishing
apparatus can include a drive mechanism to incrementally advance
the polishing sheet in a linear direction across the platen. The
controller can be configured to position the substrate away from
the recess during polishing of the substrate. The recess can
include a groove. The polishing apparatus can include the polishing
sheet. The subpad can be more compressible than the polishing
sheet.
[0031] In another aspect, a method is described. The method
includes supporting a polishing sheet having a polishing surface on
a subpad having a recess formed therein, applying a vacuum to the
recess sufficient to pull portions of the polishing sheet into the
recess to induce a recess in the polishing surface, positioning a
substrate in a carrier head over the recess in the polishing
surface, and lifting the substrate away from the polishing surface
while the substrate is positioned over the recess.
[0032] Implementations of the invention may include one or more of
the following features. The method can include rotating a platen
supporting the polishing sheet to rotate the polishing sheet. The
method can include incrementally advancing the polishing sheet in a
linear direction relative to the subpad. The recess can include a
groove.
[0033] Some of the embodiments described herein may include one or
more of the following advantages. An integrated window stripe in a
linear polishing sheet can be formed of a flexible and bendable
material to allow the composite polishing sheet to pass around
small bend radii without cracking, crazing, delaminating, or
splitting at the interface. Using a grooved subpad to support a
linear polishing sheet allows the linear sheet to develop groove
patterns in a polishing surface while still advancing in small
increments. Using a spiral-grooved subpad with deep grooves induces
a spiral groove pattern in overlying pad material, where the
induced groove pattern, in addition to providing local slurry
transport, can perform a global action of retaining slurry on the
platen or exhausting slurry and polish waste products off the
platen and away from the wafer. Fabricating a polishing sheet with
an integrated window stripe reduces the number of materials to two.
Additionally, the polishing sheet and the integrated window and
carrier can be fabricated of materials with similar chemical
properties. Incorporating optical window material in a polishing
sheet to create a dovetail-like joint increases the mechanical
strength of the interface between the window material and the
polishing sheet. Using a subpad with a feature to support a linear
polishing sheet allows the linear sheet to develop the feature in a
polishing surface while still advancing in small increments. The
subpad feature can be used to assist substrate dechuck after
polishing.
[0034] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0035] FIG. 1 is a schematic exploded perspective view of a
chemical mechanical polishing apparatus.
[0036] FIG. 2 is a top view of the CMP apparatus of FIG. 1.
[0037] FIG. 3A is a top view of the first polishing station of the
CMP apparatus of FIG. 1.
[0038] FIG. 3B is a schematic exploded perspective view of a
rectangular platen and a polishing cartridge.
[0039] FIG. 3C is a schematic perspective view of a polishing
cartridge attached to a rectangular platen.
[0040] FIG. 4 is a schematic cross-sectional view of a fixed
abrasive polishing sheet.
[0041] FIG. 5 is a schematic cross-sectional view of the polishing
station of FIG. 3A.
[0042] FIG. 6 is a schematic cross-sectional view of a polishing
station having an optical endpoint detection system.
[0043] FIG. 7 is a schematic cross-sectional view of a platen and
polishing pad of a second polishing station.
[0044] FIG. 8 is a schematic cross-sectional view of a platen and
polishing pad of a final polishing station.
[0045] FIGS. 9A, 9B, 10A, 10B show a polishing sheet with an
integrated window.
[0046] FIGS. 11A-11C show a polishing pad with grooves.
[0047] FIG. 12 shows a subpad with grooves on a rectangular
platen.
[0048] FIG. 13 shows variations of grooved subpads.
[0049] FIG. 14 shows a side view of a polishing sheet on a
rectangular platen.
[0050] FIG. 15 shows a side view of a grooved subpad.
[0051] FIGS. 16-19 show a surface with a feature for dechuck.
[0052] FIGS. 20-21 show a grooved subpad and a non-grooved
polishing surface.
[0053] FIGS. 22-24 show a method of forming a polishing sheet with
a window.
[0054] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0055] Referring to FIGS. 1 and 2, one or more substrates 10 will
be polished by a chemical mechanical polishing apparatus 20. An
exemplary polishing apparatus 20 includes a machine base 22 with a
table top 23 that supports a series of polishing stations,
including a first polishing station 25a, a second polishing station
25b, and a final polishing station 25c, and a transfer station 27.
Transfer station 27 serves multiple functions, including receiving
individual substrates 10 from a loading apparatus (not shown),
washing the substrates, loading the substrates into carrier heads,
receiving the substrates from the carrier heads, washing the
substrates again, and finally, transferring the substrates back to
the loading apparatus. A description of a similar polishing
apparatus may be found in U.S. Pat. No. 5,738,574, the entire
disclosure of which is incorporated herein by reference.
[0056] Each polishing station includes a rotatable platen. At least
one of the polishing stations, such as first station 25a, includes
a polishing cartridge 102 mounted to a rotatable, rectangular
platen 100. The polishing cartridge 102 includes a linearly
advanceable sheet or belt of fixed-abrasive polishing material. The
remaining polishing stations, e.g., second polishing station 25b
and final polishing station 25c, may include polishing pads 32 and
34, respectively, each attached to a circular platen 30. Each
platen may be connected to a platen drive motor (not shown) that
rotates the platen at thirty to two hundred revolutions per minute,
although lower or higher rotational speeds may be used. Assuming
that substrate 10 is a 300 mm diameter disk, then rectangular
platen 100 may be about thirty inches on a side, and circular
platen 30 and polishing pads 32 and 34 may be about thirty inches
in diameter.
[0057] Each polishing station 25a, 25b, and 25c also includes a
combined slurry/rinse arm 52 that projects over the associated
polishing surface. Each slurry/rinse arm 52 may include two or more
slurry supply tubes to provide a polishing liquid, slurry, or
cleaning liquid to the surface of the polishing pad. For example,
the polishing liquid dispensed onto the fixed-abrasive polishing
sheet at first polishing station 25a will not include abrasive
particles, whereas the slurry dispensed onto the standard polishing
pad at second polishing station 25b will include abrasive
particles. If final polishing station 25c is used for buffing, the
polishing liquid dispensed onto the polishing pad at that station
would not include abrasive particles. Typically, sufficient liquid
is provided to cover and wet the entire polishing pad. Each
slurry/rinse arm also includes several spray nozzles (not shown)
which provide a high-pressure rinse at the end of each polishing
and conditioning cycle.
[0058] The polishing stations may include an optional associated
pad conditioner apparatus 40. The polishing stations that include
polishing pad, i.e., polishing station 25a, may include an optional
unillustrated cleaning apparatus to remove grit or polishing debris
from the surface of the polishing sheet. The cleaning apparatus may
include a rotatable brush to sweep the surface of the polishing
sheet and/or a nozzle to spray a pressurized cleaning liquid, e.g.,
deionized water, onto the surface of the polishing sheet. The
cleaning apparatus can be operated continuously, or between
polishing operations. In addition, the cleaning apparatus could be
stationary, or it could sweep across the surface of the polishing
sheet.
[0059] In addition, optional cleaning stations 45 may be positioned
between polishing stations 25a and 25b, between polishing stations
25b and 25c, between polishing station 25c and transfer station 27,
and between transfer station 27 and polishing station 25a, to clean
the substrate as it moves between the stations.
[0060] In the exemplary polishing system, a rotatable multi-head
carousel 60 is supported above the polishing stations by a center
post 62 and is rotated about a carousel axis 64 by a carousel motor
assembly (not shown). Carousel 60 includes four carrier head
systems mounted on a carousel support plate 66 at equal angular
intervals about carousel axis 64. Three of the carrier head systems
receive and hold substrates, and polish them by pressing them
against the polishing sheet of station 25a and the polishing pads
of stations 25b and 25c. One of the carrier head systems receives a
substrate from and delivers a substrate to transfer station 27.
[0061] Each carrier head system includes a carrier or carrier head
80. A carrier drive shaft 78 connects a carrier head rotation motor
76 (shown by the removal of one quarter of the carousel cover) to
carrier head 80 so that each carrier head can independently rotate
about its own axis. In addition, each carrier head 80 independently
laterally oscillates in a radial slot 72 formed in carousel support
plate 66.
[0062] The carrier head 80 performs several mechanical functions.
Generally, the carrier head holds the substrate against the
polishing surface, evenly distributes a downward pressure across
the back surface of the substrate, transfers torque from the drive
shaft to the substrate, and ensures that the substrate does not
slip out from beneath the carrier head during polishing operations.
A description of a suitable carrier head may be found in U.S. Pat.
Nos. 6,183,354 and 6,857,945, filed May 21, 1997, the entire
disclosures of which are incorporated herein by reference.
[0063] Referring to FIGS. 3A, 3B, and 3C, polishing cartridge 102
is detachably secured to rectangular platen 100 at polishing
station 25a. Polishing cartridge 102 includes a feed roller 130, a
take-up roller 132, and a generally linear sheet or belt 110 of a
polishing pad material. An unused or a fresh portion 120 of the
polishing sheet is wrapped around feed roller 130, and a used
portion 122 of the polishing sheet is wrapped around take-up roller
132. A rectangular exposed portion 124 of the polishing sheet that
is used to polish substrates extends between the used and unused
portions 120, 122 over a top surface 140 of rectangular platen
100.
[0064] The rectangular platen 100 can be rotated (as shown by
phantom arrow A in FIG. 3A) to rotate the exposed portion of the
polishing sheet and thereby provide relative motion between the
substrate and the polishing sheet during polishing. Between
polishing operations, the polishing sheet can be advanced (as shown
by phantom arrow B in FIG. 3A) to expose an unused portion of the
polishing sheet. When the polishing material advances, polishing
sheet 110 unwraps from feed roller 130, moves across the top
surface of the rectangular platen 100, and is taken up by take-up
roller 132 (as shown in FIG. 14).
[0065] Referring to FIG. 4, in some embodiments, the polishing
sheet 110 includes two layers. An upper polishing layer 119 is
formed from a polishing material and a lower layer 116, such as a
backing layer or carrier layer is formed from a film. The upper
polishing layer 119 can be formed from a resin, such as a phenolic
resins, polyurethane, urea-formaldehyde resin, melamine
formaldehyde resin, acrylated urethane, acrylated epoxy,
ethylenically unsaturated compound, aminoplast derivative having at
least one pendant acrylate group, isocyanurate derivative having at
least one pendant acrylate group, vinyl ether, epoxy resin, and
combinations thereof. The sheet can also include fillers, such as
hollow microspheres or voids. Lower layer 116 is a backing layer
composed of a material such as a polymeric film, e.g., polyethylene
terephthalate (PET), paper, cloth, a metallic film or the like. In
some embodiments, the two layers are bonded together, such as with
an epoxy or an adhesive, e.g., a pressure sensitive adhesive, or by
welding the two layers together. The polishing layer can be between
10 and 150 mils, such as between 20 and 80 mils, such as around 40
mils thick. The polishing sheet 110 can be about twenty, twenty
five or thirty inches wide.
[0066] Referring to FIGS. 11A-11C, in some implementations, the
upper polishing layer of the polishing sheet 110 has grooves in the
top surface. The grooves can be of any configuration, but can be
rotationally and translationally invariant. The grooves can be
x-grooves, shown in FIG. 11B, that is, grooves that are arranged
perpendicular to the direction of travel of the sheet, xy-grooves,
shown in FIG. 11A, that is, grooves that are perpendicular and
parallel to the direction of travel of the sheet, diagonal grooves,
or other suitable groove pattern. In FIGS. 11A-11B, the arrows
indicate the direction of travel. The grooves can be between about
45 and 5 mils deep, such as between about 35 and 15 mils, such as
about 25 mils deep. In some implementations, the grooves are spaced
closely together to aid in bending the polishing sheet, as
described further herein.
[0067] Referring again to FIGS. 3A, 3B and 3C, a transparent strip
118 can be formed along the length of polishing sheet 110. The
transparent strip 118 or window may be positioned at the center of
the sheet, that is, the window can run the length of the polishing
pad and be approximately equidistant to each pad edge, and may be
between about 0.2 and 1 inch wide, such as between about 0.4 and
0.8 inches wide or about 0.6 inches wide. The transparent strip
will be aligned with an aperture or transparent window 154 in
rectangular platen 100 to provide optical monitoring of the
substrate surface for end point detection, as discussed in greater
detail below. The top surface of the transparent strip 118 can be
planar with the top surface of the polishing portion of the
polishing sheet 110. This arrangement prevents slurry from
collecting on the transparent strip 118 and adversely affecting any
metrology that is performed through the transparent strip 118.
[0068] The feed and take-up rollers 130 and 132 should be slightly
longer than the width of polishing sheet 110. The rollers 130, 132
may be plastic or metal cylinders about 20'' long and between about
2'' and 2.5'' in diameter. Because the polishing sheet 110 passes
around the rollers 130, 132 many times, the transparent strip 118
is formed of a material that is not prone to cracking, crazing,
delaminating or splitting, such as at the pad/strip interface.
Ideally, the transparent strip is formed of a material sufficiently
durable to hold up to conditioning with a diamond coated
conditioning tool. In some implementations, the transparent strip
118 is integral with the backing layer, that is, the transparent
strip 118 and the backing layer are made of the same material and
are a single unit. In some implementations, the transparent strip
can be molded to the polishing layer. In some implementations, the
top surface of the transparent strip 118 is substantially planar
with the top surface of the polishing sheet 110.
[0069] A commercially available material having many of the desired
properties of the transparent strip is Calthane ND 3200
polyurethane (Cal Polymers, Long Beach, Calif.). The material is a
two part clear non-ambering urethane elastomer, and it has a
transmittance of at least 80% (for a 150 mils thick sheet) for
wavelengths of 350 nm and greater (out to the end of the visible
light spectrum at about 700 nm). The material has a refractive
index of about 1.48. Without being limited to any particular
theory, it is believed that the high transmission of this
polyurethane material (in contrast to currently available
polyurethane window materials) is the use of a polyurethane
material that is substantially free of internal defects. Although
current polyurethanes used for windows are generally free of
additives, such materials can include internal defects, such as
bubbles or voids, cracks, or microdomains (e.g., small areas of
differing crystalline structure or orientation) that act to diffuse
or scatter the light. By forming the polyurethane substantially
free of internal defects, it is possible to achieve a high optical
clarity. In some implementations, the transparent strip 118 is
formed from a polyurethane material, for example, Calthane ND 3200.
The material forming the transparent strip can have hardness on the
Shore D scale of between about 50 and 80, such as 60. In some
implementations, the material forming the transparent strip has a
thickness of between about 50 mils and 55 mils.
[0070] Rectangular platen 100 includes a generally planar
rectangular top surface 140 bounded by a feed edge 142, a take-up
edge 144, and two parallel lateral edges 146. A groove 150 (shown
in phantom in FIGS. 3A and 3C) is formed in top surface 140. The
groove 150 may be a generally-rectangular pattern that extends
along edges 142-146 of top surface 140. A passage 152 through
platen 100 connects groove 150 to a vacuum source 200 (see FIG. 5).
When passage 152 is evacuated, exposed portion 124 of polishing
sheet 110 is vacuum-chucked to top surface 140 of platen 100. This
vacuum-chucking helps ensure that lateral forces caused by friction
between the substrate and the polishing sheet during polishing do
not force the polishing sheet off the platen. As discussed,
aperture 154 is formed in top surface 140 of rectangular platen
100. A compressible subpad 300 may be placed on the top surface of
the platen 100 to cushion the impact of the substrate against the
polishing sheet as shown in FIGS. 12 and 14. In addition, platen
100 may include an unillustrated shim plate. Shim plates of
differing thickness may be attached to the platen to adjust the
vertical position of the top surface of platen. The compressible
subpad can be attached to the shim plate.
[0071] The subpad can be separate from the polishing sheet, that
is, not integral with the polishing sheet or not adhered together.
The subpad 300 can be formed from a single material or can be
formed from multiple layers of materials. A pad formed of multiple
layers of materials can be a stacked pad. In one embodiment, a
stacked subpad has a layer of IC polishing material stacked on a
layer of foam, such as a soft foam, for example, SUBA IV, available
from Rohm and Haas of Newark, Del. The upper layer of the stacked
pad can be between about 40 and 120 mils thick, such as between 60
and 100 mils, such as around 80 mils thick. The lower layer of the
subpad can be between about 30 and 70 mils, such as between about
40 and 60 mils, such as around 50 mils thick.
[0072] Referring to FIG. 15, the subpad 300 can have grooves that
are the same or different from the grooves in the polishing layer.
Referring to FIG. 13, the grooves can be circular, oval, off-center
circular, or spiral. The grooves in the subpad 300 can be of
sufficient depth and width such that when a vacuum is pulled on the
subpad, grooves are introduced into the polishing sheet even if the
overlying polishing sheet does not have grooves. The grooves can
have a depth between about 30 and 50 mils, such as between about 35
and 40 mils. In some implementations, the grooves in the subpad can
have a greater width, pitch, and/or depth than the grooves in the
polishing surface. In some implementations, the groove pattern of
the polishing surface is different than the groove pattern of a
subpad. The subpad 300 can be circular, rectangular or any shape
that is suitable for use with the platen 100.
[0073] Referring to FIGS. 20-21, a pattern of grooves 306 is formed
in one or more layers of the subpad material that support a
polishing surface 302. The polishing surface 302 is pulled into the
groove pattern by vacuum (as shown by the vertical arrows). The
result is that a pattern of grooves is formed in the
polishing-surface 302. This groove pattern facilitates slurry
distribution between the wafer and the polishing surface 302, and,
consequently improves the process performance of the polisher.
Thus, grooves are not required in the polishing surface. One
advantage of forming grooves in the subpad 300 is that a web-style
pad or linear sheet can exhibit or provide a circular or spiral
groove pattern in the polishing surface and still be advanced in
small increments without changing the location of the groove
pattern.
[0074] The subpad has a surface that need not be a polishing layer.
That is, the surface roughness or coefficient of friction of the
subpad need not be sufficient for polishing a substrate surface.
Additionally, the polishing pad or polishing sheet alone may not
have much structural rigidity. The subpad can provide the
structural rigidity. The polishing performance of the polishing
sheet or pad is influenced by the mechanical properties of the
subpad. A stiff subpad and a softer subpad will provide different
polishing results with the same polishing sheet or polishing pad.
Because the subpad does not wear away as quickly as a polishing
sheet or polishing pad, the subpad can have a longer useful life
than the polishing layer. Thus, when the polishing sheet is
advanced or changed, the same subpad can be continued to be
used.
[0075] As illustrated by FIG. 5, rectangular platen 100 is secured
to a rotatable platen base 170. Rectangular platen 100 and platen
base 170 may be joined by several peripheral screws 174
counter-sunk into the bottom of platen base 170. A first collar 176
is connected by screws 178 to the bottom of platen base 170 to
capture the inner race of an annular bearing 180. A second collar
182, connected to table top 23 by a set of screws 183, captures the
outer race of annular bearing 180. Annular bearing 180 supports
rectangular platen 100 above table top 23 while permitting the
platen to be rotated by the platen drive motor.
[0076] A platen motor assembly 184 is bolted to the bottom of table
top 23 through a mounting bracket 186. Platen motor assembly 184
includes a motor 188 having an output drive shaft 190. Output shaft
190 is fitted to a solid motor sheath 192. A drive belt 194 winds
around motor sheath 192 and a hub sheath 196. Hub sheath 196 is
joined to platen base 170 by a platen hub 198. Thus, motor 188 may
rotate rectangular platen 100. Platen hub 198 is sealed to lower
platen base 170 and to hub sheath 196.
[0077] A pneumatic control line 172 extends through rectangular
platen 100 to connect passage 152, and thus grooves 150, to a
vacuum or pressure source. The pneumatic line 172 may be used both
to vacuum-chuck the polishing sheet and to power or activate a
polishing sheet advancement mechanism, which is further described
in U.S. Pat. No. 6,135,859, filed Apr. 30, 1999, the entire
disclosure of which is incorporated herein by reference.
[0078] The platen vacuum-chucking mechanism may be powered by a
stationary pneumatic source 200 such as a pump or a source of
pressurized gas. Pneumatic source 200 is connected by a fluid line
202 to a computer controlled valve 204. The computer controlled
valve 204 is connected by a second fluid line 206 to a rotary
coupling 208. The rotary coupling 208 connects the pneumatic source
200 to an axial passage 210 in a rotating shaft 212, and a coupling
214 connects axial passage 210 to a flexible pneumatic line
216.
[0079] Vacuum-chucking passage 152 can be connected to flexible
pneumatic line 216 via pneumatic line 172 through rectangular
platen 100, a passage 220 in platen base 170, a vertical passage
222 in platen hub 198, and a passageway 224 in hub sheath 196.
O-rings 226 may be used to seal each passageway.
[0080] A general purpose programmable digital computer 280 is
appropriately connected to valve 204, platen drive motor 188,
carrier head rotation motor 76, and a carrier head radial drive
motor (not shown). Computer 280 can open or close valve 204, rotate
platen 100, rotate carrier head 80 and move carrier head along slot
72.
[0081] Referring to FIG. 6, in some embodiments an aperture or hole
154 is formed in platen 100 and is aligned with transparent strip
118 in polishing sheet 110. The aperture 154 and transparent strip
118 are positioned such that they have a view of substrate 10
during a portion of the platen's rotation, regardless of the
translational position of the polishing head. An optical monitoring
system 90 is located below and secured to platen 100, e.g., between
rectangular platen 100 and platen base 170 so that it rotates with
the platen. The optical monitoring system includes a light source
94 and a detector 96. The light source generates a light beam 92
which propagates through aperture 154 and transparent strip 118 to
impinge upon the exposed surface of substrate 10.
[0082] Referring to FIGS. 9B and 10B, in some implementations, the
material that is used to form the transparent strip 118 in the
polishing sheet 110 also forms the lower layer 116 of the polishing
sheet 110. For example, the material can be a polymer material.
Referring to FIG. 9A, in some implementations, the transparent
strip 118 is formed with the lower layer 116. The material that
forms polishing layer 119 can then be formed on the lower layer
116, such as by casting. If any of the polishing layer material
covers the transparent strip 118, this material can be removed from
over the transparent strip 118. The exposed surface of the
transparent strip 118 can be substantially planar with the 30
exposed surface of the polishing layer 119.
[0083] Referring to FIG. 10A, in some implementations, the
polishing layer 119 is fabricated before the lower layer 116. A
recess is formed in the polishing layer 119 or the polishing layer
119 is formed of two separate pieces. The lower layer 116 and
transparent strip 118 are then fabricated on the polishing layer
119. The transparent strip 118 can therefore by formed
simultaneously with the lower layer 116 and can be integral with
the lower layer 116. There may not be a seam at the junction of the
lower layer 116 and the transparent strip 118. Either of the
polishing layer 119 or the lower layer 116 can be formed by
molding, extruding, casting, shaping with pinch rollers, ablating
or mechanical milling. In some instances, the layer that is formed
first is allowed to dry or cure. The second layer is then
fabricated on top of the first. In some implementations, the two
layers are formed separately and adhered or welded together. In any
of the implementations, the transparent strip 118 extends from the
top surface of the polishing sheet to the bottom surface of the
polishing sheet, yielding a window. The top surface of the
polishing layer is substantially free of abrasives. Grooves can be
formed in the polishing surface after or while the surface is being
formed. The transparent strip 118 can be free of grooves. However,
in some implementations, grooves are also formed in the transparent
strip 118. In some implementations, the window extends the entire
length of the polishing layer. In some implementations, the carrier
layer extends across the width of the polishing layer.
[0084] Referring to FIGS. 22-24, an alternative method is shown for
forming the window 404 in the polishing sheet 110. Referring to
FIG. 22, a polishing sheet is formed from a material suitable for
polishing a substrate. The polishing sheet can be formed by
molding, cutting or extruding. A plurality of dovetail-like
openings 402, fissures or grooves are formed in the polishing
sheet. The two halves are separated by the desired width of the
window 404. Referring to FIG. 23, material that can be dried, cured
or hardened is inserted into the groove (as indicated by the
arrow). The material, such as a liquid precursor of the window
material, is then dried, cured or hardened forming a composite
polishing sheet. Referring to FIG. 24, the window material is
intimately bonded to the polishing material, with projections of
the window material interlocking with projections of the polishing
material (not shown). The window material can be selected so that
the window material and polishing material of the composite
polishing sheet will wear evenly or uniformly and bend around the
same radii without delaminating. Other process steps may also be
required, such as cutting the sheet or skiving the sheet from a
cast block of pad material. The window can be centered and
generally equidistant from the edges of the sheet or be between the
edge of the polishing sheet and the center, as shown in FIG. 23.
The window can extend substantially the entire length of the
polishing sheet. In some implementations, a surface of the window
can be substantially planar with a surface of the polishing
sheet.
[0085] In operation, CMP apparatus 20 uses optical monitoring
system 90 to determine the thickness of a layer on the substrate,
to determine the amount of material removed from the surface of the
substrate, or to determine when the surface has become planarized.
The computer 280 may be connected to light source 94 and detector
96. Electrical couplings between the computer and the optical
monitoring system may be formed through rotary coupling 208. The
computer may be programmed to activate the light source when the
substrate overlies the window, to store measurements from the
detector, to display the measurements on an output device 98, and
to detect the polishing endpoint, as described in U.S. Pat. Nos.
6,159,073 and 6,280,289, filed Nov. 2, 1998, the entire disclosures
of which are incorporated herein by reference.
[0086] In operation, exposed portion 124 of polishing sheet 110 or
the subpad is vacuum-chucked to rectangular platen 100 by applying
a vacuum to passage 152. A substrate is lowered into contact with
polishing sheet 110 by carrier head 80, and both platen 100 and
carrier head 80 rotate to polish the exposed surface of the
substrate. After polishing, the substrate is lifted off the
polishing pad by the carrier head. The vacuum on passage 152 is
removed. The polishing sheet is advanced, such as by applying a
positive pressure to pneumatic line 172 to trigger, the advancement
mechanism. Alternatively, the positive pressure is used to blow the
sheet off the platen and ease sheet advancement. This exposes a
fresh segment of the polishing sheet. The polishing sheet is then
vacuum-chucked to the rectangular platen, and a new substrate is
lowered into contact with the polishing sheet. Thus, between each
polishing operation, the polishing sheet may be advanced
incrementally. If the polishing station includes a cleaning
apparatus, the polishing sheet may be washed between each polishing
operation.
[0087] The amount that the sheet may be advanced will depend on the
desired polishing uniformity and the properties of the polishing
sheet, but should be on the order of 0.05 to 1.0 inches, e.g., 0.4
inch, per polishing operation. Assuming that the exposed portion
124 of polishing sheet is 20 inches long and the polishing sheet
advances 0.4 inches after each polishing operation, the entire
exposed portion of the polishing sheet will be replaced after about
fifty polishing operations.
[0088] When the substrate has been polished, the carrier head
removes the substrate from the polishing layer, that is, the
carrier head dechucks the substrate from the polishing surface. The
substrate can be removed from the polishing surface by applying a
suction to the back of the substrate and lifting. The slurry in
combination with a flat wafer can make it difficult to remove the
substrate from the polishing surface because of the strong surface
tension.
[0089] In some implementations, the polishing sheet, polishing pad
or subpad has a feature, such as a groove or an embossed feature,
that can aid in wafer dechuck. During polishing, the substrate is
in contact with a portion of the polishing surface that does not
include or is not over the feature. After polishing, the edge of
the substrate is moved over the feature, where the feature can
serve as a dechuck enhancement feature.
[0090] Referring to FIGS. 16-19, in some implementations, a subpad
300 has a feature 304 suitable to assist with substrate dechuck.
When no platen vacuum is applied, the polishing surface 302 does
not follow the contour of the feature 304 in the subpad (FIG. 19).
When a vacuum is applied, the polishing surface 302 conforms to the
feature 304. A substrate is not over the feature during polishing.
During dechuck, a substrate is partially over the feature. FIGS.
18-19 show plan views of the substrate during polishing and during
dechuck, respectively.
[0091] In the polishing sheet, the dechuck feature can be formed
along the centerline of the sheet, along an edge or between the
edge and the centerline of the polishing sheet.
[0092] Referring to FIG. 7, at second polishing station 25b, the
circular platen may support a circular polishing pad 32 having a
roughened surface 262, an upper layer 264 and a lower layer 266.
Lower layer 266 may be attached to platen 30 by a
pressure-sensitive adhesive layer 268. Upper layer 264 may be
harder than lower layer 266. For example, upper layer 264 may be
composed of microporous polyurethane or polyurethane mixed with a
filler, whereas lower layer 266 may be composed of compressed felt
fibers leached with urethane. A two layer polishing pad, with the
upper layer composed of IC 1000 or IC-1400 and the lower layer
composed of SUBA IV, is available from Rohm and Haas of Newark,
Del. (IC 1000, IC-1400 and SUBA IV are product names of Rohm and
Haas). A transparent window 269 may be formed in polishing pad 32
over an aperture 36 in platen 30.
[0093] Referring to FIG. 8, at final polishing station 25c, the
platen may support a polishing pad 34 having a generally smooth
surface 272 and a single soft layer 274. Layer 274 may be attached
to platen 30 by a pressure-sensitive adhesive layer 278. Layer 274
may be composed of a napped poromeric synthetic material. A
suitable soft polishing pad is available from Rohm and Haas, under
the trade name Politex.TM.. Polishing pads 32 and 34 may be
embossed or stamped with a pattern to improve distribution of
slurry across the face of the substrate. Polishing station 25c may
otherwise be identical to polishing station 25b. A transparent
window 279 may be formed in polishing pad 34 over aperture 36.
[0094] In some implementations, the circular polishing pad 32, 34
can have a spiral groove or multiple spiral grooves, such as two
spiral grooves starting 180 degrees apart, giving a
groove-to-groove pitch in the radial direction, or three, four, or
more spiral grooves.
[0095] Although the CMP apparatus is described as vacuum chucking
the polishing sheet to the platen, other techniques could be used
to secure the polishing sheet to the platen during polishing. For
example, the edges of the polishing sheet could be clamped to the
sides of the platen by a set of clamps.
[0096] Also, although the rollers are described as connected to the
retainers by pins that are inserted through apertures, numerous
other implantations are possible to rotatably connect the rollers
to the platen. For example, a recess could be formed on the inner
surface of the retainer to engage a pin that projects from the end
face of the roller. The retainers 160 may be slightly bendable, and
the rollers might be snap-fit into the retainers. Alternately, the
recess in the inner surface of the retainer could form a labyrinth
path that traps the rollers due to tension. Alternately, the
retainer could be pivotally attached to the platen, and the roller
could engage the retainer once the retainer is locked in
position.
[0097] In addition, although the CMP apparatus is described as
having one rectangular platen with a grooved surface and two
circular platens with round polishing pads, other configurations
are possible. For example, the apparatus can include one, two or
three rectangular platens. The pad, sheet and subpad embodiments
described herein can be used with continuous belts, non-rotating
platen systems, and polishing systems with only one polishing
station. In fact, one advantage of CMP apparatus 20 is that each
platen base 170 is adaptable to receive either a rectangular platen
or a circular platen. The polishing sheet on each rectangular
platen may be a fixed abrasive or a non-fixed abrasive polishing
material. The polishing sheet can include multiple layers which are
bonded together. Similarly, each polishing pad on the circular
platen can be a fixed-abrasive or a non-fixed abrasive polishing
material. The standard polishing pads can have a single hard layer
(e.g., IC-1000), a single soft layer (e.g., as in a Politex.TM.
pad), or two stacked layers (e.g., as in a combined IC-1000/SUBA IV
polishing pad). Different slurries and different polishing
parameters, e.g., carrier head rotation rate, platen rotation rate,
carrier head pressure, can be used at the different polishing
stations.
[0098] One implementation of the CMP apparatus may include two
rectangular platens with fixed-abrasive polishing sheets for
primary polishing, and a circular platen with a soft polishing pad
for buffing. The polishing parameters, pad composition and slurry
composition can be selected so that the first polishing sheet has a
faster polishing rate than the second polishing sheet.
[0099] When a subpad and the polishing sheet 110 are used together,
the polishing sheet 110 slides across the subpad between or during
polishes.
[0100] With some of the polishing sheets described herein, a number
of wafers and each wafer will be polished by a portion of the
polishing sheet that has not previously been used to polish another
pad. Alternatively, the polishing sheet can be moved incrementally
rather than a full length between each substrate polish. Pad wear
will not be a factor in polishing subsequent wafers, because each
wafer is exposed to substantially the same polishing pad
conditions. A steady-state for the pad surface will result once the
sheet has been incremented the distance equal to the diameter of
the polishing area.
[0101] Grooves in the top surface of the polishing sheet that are
perpendicular to the direction of travel of the polishing sheet can
aid the polishing sheet in bending when the sheet is rolled or
stretches across the small radius of the feed roller 130 before
reaching the wafer. If a system has grooves in a subpad, the subpad
can form temporary grooves in the polishing surface, aiding in
slurry transport and flow across the surface of the pad. The
temporary grooves can be more pronounced when a vacuum is applied
to the subpad. Alternatively, or in addition, the polishing surface
of a polishing pad can have grooves.
[0102] The grooves of a pad or a subpad can have a spiral shape.
The spiral grooves can pump slurry toward the polishing surface.
The spiral grooves originate from the center of the pad or subpad
and move out towards the outer edge. As the platen rotates, the
spirals converge toward or away from the center of the polishing
area. The grooves perform a global action of either retaining
slurry on the platen or moving exhausted slurry and/or polish waste
products off the platen and away from the wafer. If the platen is
rotated in the direction of increasing spiral groove radius so that
the spiral appears to converge, that is move toward the center,
slurry is transported toward the center. If the platen is rotated
in the direction of decreasing spiral groove radius so that the
spiral appears to expand, spent slurry and waste products are moved
off of the platen more quickly than by centrifugal force alone. A
pad or subpad with multiple spirals, e.g., two spirals, can move
the slurry faster than a pad or subpad with a single groove.
[0103] In addition to any slurry transporting or pumping action,
spiral grooves in the polishing layer or subpad can control
polishing undulations or in homogeneities in removal of material
from the wafer surface. In some implementations, the subpad can
have a thickness of about 150 mils. In some implementations, the
spiral grooves can have a depth of between about 40 mils and 60
mils, such as about 50 mils, and a width of between about 400 mils
and 600 mils, such as 500 mils. The pitch of the grooves can be
about 1 inch.
[0104] Alternative embodiments of the platen can have a central
region of top surface free from grooves to prevent potential
deflection of the polishing sheet into the grooves from interfering
with the polishing uniformity.
[0105] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
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.
* * * * *