U.S. patent application number 09/844991 was filed with the patent office on 2002-10-31 for method for planarizing organosilicate layers.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Gaillard, Frederic, Lutti, Charles, Rivoire, Maurice, Yieh, Ellie.
Application Number | 20020160692 09/844991 |
Document ID | / |
Family ID | 25294138 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020160692 |
Kind Code |
A1 |
Rivoire, Maurice ; et
al. |
October 31, 2002 |
Method for planarizing organosilicate layers
Abstract
A method for planarizing an organosilicate layer is provided.
The organosilicate material layer is planarized using a slurry in
conjunction with a chemical mechanical polishing (CMP) process. The
slurry comprises an abrasive material dispersed in a suitable
solvent. The slurry preferably has a pH greater than about 9. The
abrasive material preferably has an average particle size greater
than about 35 nm (nanometers).
Inventors: |
Rivoire, Maurice; (Meylan,
FR) ; Gaillard, Frederic; (Meylan, FR) ;
Lutti, Charles; (Grenoble, FR) ; Yieh, Ellie;
(San Jose, CA) |
Correspondence
Address: |
APPLIED MATERIALS, INC.
2881 SCOTT BLVD. M/S 2061
SANTA CLARA
CA
95050
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
25294138 |
Appl. No.: |
09/844991 |
Filed: |
April 27, 2001 |
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24B 49/006 20130101;
C09K 3/1463 20130101; B24B 37/044 20130101; C09G 1/02 20130101;
B24B 37/0056 20130101 |
Class at
Publication: |
451/41 |
International
Class: |
B24B 007/22 |
Claims
What is claimed is:
1. A composition for planarizing an organosilicate layer,
comprising: a slurry including an abrasive material dispersed in a
solvent, wherein the slurry has a pH greater than about 9.
2. The composition of claim 1 wherein the abrasive material is
selected from the group consisting of silica (SiO.sub.2), aluminum
oxide (Al.sub.2O.sub.3), zirconium oxide (ZrO.sub.2), titanium
oxide (TiO.sub.2), and combinations thereof.
3. The composition of claim 1 wherein the abrasive material has an
average particle size greater than about 35 nm (nanometers).
4. The composition of claim 1 wherein the pH of the slurry is
adjusted by adding a source of hydroxyl ions thereto.
5. The composition of claim 4 wherein the source of hydroxyl ions
is selected from the group consisting of potassium hydroxide (KOH),
ammonium hydroxide (NH.sub.4OH), sodium hydroxide (NaOH), calcium
hydroxide (CaOH), magnesium hydroxide (MgOH), and combinations
thereof.
6. The composition of claim 1 wherein the slurry further comprises
one or more materials selected from the group consisting of
chelating agents, buffers, oxidizers, and corrosion inhibitors.
7. The composition of claim 1 wherein the concentration of the
abrasive material in the slurry is within a range of about 10% by
weight to about 60% by weight.
8. A method for planarizing an organosilicate layer, comprising:
positioning a substrate having an organosilicate layer thereon in a
polishing system; providing a slurry including an abrasive material
dispersed in a solvent to the polishing system, wherein the slurry
has a pH greater than about 9.0; and polishing the organosilicate
layer using the slurry.
9. The method of claim 8 wherein the abrasive material is selected
from the group consisting of silica (SiO.sub.2), aluminum oxide
(Al.sub.2O.sub.3), zirconium oxide (ZrO.sub.2), titanium oxide
(TiO.sub.2), and combinations thereof.
10. The method of claim 8 wherein the abrasive material has an
average particle size greater than about 35 nm (nanometers).
11. The method of claim 8 wherein the pH of the slurry is adjusted
by adding a source of hydroxyl ions thereto.
12. The method of claim 11 wherein the source of hydroxyl ions is
selected from the group consisting of potassium hydroxide (KOH),
ammonium hydroxide (NH.sub.4OH), sodium hydroxide (NaOH), calcium
hydroxide (CaOH), magnesium hydroxide (MgOH).
13. The method of claim 8 wherein the slurry further comprises one
or more materials selected from the group consisting of chelating
agents, buffers, oxidizers, corrosion inhibitors, and combinations
thereof.
14. The method of claim 8 wherein the concentration of abrasive
material in the slurry is within a range of about 10% by weight to
about 60% by weight.
15. The method of claim 8 wherein the organosilicate layer is
polished by placing it in contact with a polishing pad, the
polishing pad having the slurry thereon, and wherein the polishing
pad is disposed upon a rotatable platen.
16. The method of claim 15 wherein the polishing pad comprises
polyurethane.
17. The method of claim 15 wherein the organosilicate layer
contacts the polishing pad with a pressure within range of about 1
psi (pounds/square inch) to about 14 psi.
18. The method of claim 15 wherein the platen rotates at a speed
within the range of about 0.1 m/s (meters/second) to about 2
m/s.
19. A method for fabricating a device, comprising: providing a
substrate having conductive features formed thereon with an
organosilicate layer deposited between and on top of the conductive
features; positioning the substrate in a polishing system;
providing a slurry including an abrasive material dispersed in a
solvent to the polishing system, wherein the slurry has a pH
greater than about 9; and polishing the organosilicate layer using
the slurry.
20. The method of claim 19 wherein the abrasive material is
selected from the group consisting of silica (SiO.sub.2), aluminum
oxide (Al.sub.2O.sub.3), zirconium oxide (ZrO.sub.2), titanium
oxide (TiO.sub.2), and combinations thereof.
21. The method of claim 19 wherein the abrasive material has an
average particle size greater than about 35 nm (nanometers).
22. The method of claim 19 wherein the pH of the slurry is adjusted
by adding a source of hydroxyl ions thereto.
23. The method of claim 22 wherein the source of hydroxyl ions is
selected from the group consisting of potassium hydroxide (KOH),
ammonium hydroxide (NH.sub.4OH), sodium hydroxide (NaOH), calcium
hydroxide (CaOH), and magnesium hydroxide (MgOH).
24. The method of claim 19 wherein the slurry further comprises one
or more materials selected from the group consisting of chelating
agents, buffers, oxidizers, corrosion inhibitors, and combinations
thereof.
25. The method of claim 19 wherein the concentration of abrasive
material in the slurry is within a range of about 10% by weight to
about 60% by weight.
26. The method of claim 19 wherein the organosilicate layer is
polished by placing it in contact with a polishing pad having the
slurry thereon, and wherein the polishing pad is disposed upon a
rotatable platen.
27. The method of claim 26 wherein the polishing pad comprises
polyurethane.
28. The method of claim 26 wherein the organosilicate layer
contacts the polishing pad with a pressure within a range of about
1 psi (pounds/square inch) to about 4 psi.
29. The method of claim 26 wherein the platen rotates at a speed
within a range of about 0.1 m/s (meters/second) to about 2.0 m/s.
Description
BACKGROUND OF THE DISCLOSURE
[0001] 1. Field of the Invention
[0002] The present invention relates to organosilicate layers and,
more particularly to a method for planarizing organosilicate
layers.
[0003] 2. Description of the Background Art
[0004] In the fabrication of integrated circuits, substrate surface
planarity is of critical importance. This is especially so as the
scale of integration increases and device features are reduced in
size (e. g., sub-micron sizes). Integrated circuits typically
include metal conductor lines that are used to interconnect
discrete devices formed thereon. The metal conductor lines may be
isolated from each other by one or more dielectric material layers.
Holes (vias) formed through the dielectric layers provide
electrical access between successive conductive interconnection
layers.
[0005] In such integrated circuit fabrication processes, it is
necessary for the dielectric layers to have a flat surface (e. g.,
planar surface topography). This is because it is difficult to
image and pattern material layers applied over non-planar surfaces
using conventional photolithographic techniques.
[0006] Chemical mechanical polishing (CMP) processes have been
developed to produce surface topographies that are sufficiently
planar to satisfy the demands of conventional photolithographic
techniques used in integrated circuit fabrication processes. CMP
processes use a chemical polishing slurry in conjunction with
mechanical energy to planarize the surface of a material layer.
[0007] As the dimensions of the integrated circuit components are
reduced, the choice of material used to fabricate such components
becomes increasingly critical. For example, when the distance
between adjacent metal interconnects and/or the thickness of the
dielectric material has sub-micron dimensions, capacitive coupling
potentially occurs between such interconnects. Capacitive coupling
between adjacent metal interconnects may cause cross talk and/or
resistance-capacitance (RC) delay which degrades the overall
performance of the integrated circuit.
[0008] In order to prevent capacitive coupling between adjacent
metal interconnects, low dielectric constant (low k) insulating
materials (e. g., dielectric constants less than about 4.5) are
needed. Suitable low k dielectric materials may include
organosilicate materials. However, organosilicate materials are
prone to form defects, such as scratches and cracks when subjected
to chemical mechanical polishing (CMP). Such defects are
undesirable because they may cause integrated circuit
malfunction.
[0009] Therefore, a need exists in the art for a method of
planarizing organosilicate material layers.
SUMMARY OF THE INVENTION
[0010] A method for planarizing an organosilicate layer is
provided. The organosilicate material layer is planarized using a
slurry in conjunction with a chemical mechanical polishing (CMP)
process. The slurry comprises an abrasive material dispersed in a
suitable solvent. The slurry preferably has a pH greater than about
9. The abrasive material preferably has an average particle size
greater than about 35 nm (nanometers).
[0011] The organosilicate material layer may be planarized using
the slurry in conjunction with a CMP process. In one CMP process, a
substrate having an organosilicate layer is placed in contact with
a polishing pad on a rotatable platen. The polishing pad has the
slurry thereon. The organosilicate material layer is planarized by
moving the substrate and platen relative to one another.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The teachings of the present invention can be readily
understood by considering the following detailed description in
conjunction with the accompanying drawings, in which:
[0013] FIG. 1 depicts a schematic illustration of a chemical
mechanical polishing (CMP) apparatus that can be used for the
practice of embodiments described herein; and
[0014] FIGS. 2a-2b depict schematic cross-sectional views of a
substrate at different stages of integrated circuit
fabrication.
DETAILED DESCRIPTION
[0015] Embodiments described herein relate to a planarization
process that may be performed using a chemical mechanical polishing
(CMP) process system, such as, for example, the Mirra.RTM. CMP
System, available from Applied Materials, Inc., Santa Clara, Calif.
Details of the Mirra.RTM. CMP System are described in commonly
assigned U.S. Pat. No. 5,738,574, entitled, "Continuous Processing
System for Chemical Mechanical Polishing," which is herein
incorporated by reference. Although, the CMP process system
described herein is illustrated utilizing the Mirra.RTM. CMP
System, other CMP systems which may be used to perform chemical
mechanical polishing are also contemplated.
[0016] FIG. 1 is a schematic perspective view of a chemical
mechanical polishing system 20. The polishing system 20 includes a
lower machine base 22 with a table top 28 mounted thereon and a
removable outer cover (not shown). The table top 28 supports a
series of polishing stations 25a, 25b, 25c as well as a transfer
station 27.
[0017] The transfer station 27 performs multiple functions, such
as, for example, receiving individual substrates 10 from a loading
apparatus (not shown), washing substrates, and loading/unloading
substrates to/from carrier heads 80.
[0018] Each polishing station 25a, 25b, 25c includes a rotatable
platen 30 having a polishing pad 100, 110 disposed thereon. The
platen 30 may be a rotatable aluminum or stainless steel plate
connected to a platen drive motor (not shown).
[0019] The polishing stations 25a, 25b, 25c may optionally include
a pad conditioner 40. The pad conditioner 40 comprises a rotatable
arm 42 holding an independently rotating conditioner head 44 and an
associated washing basin 46. The pad conditioner 40 is used to
maintain the condition of the polishing pad 100, 110.
[0020] The polishing stations 25a, 25b, 25c may also include a
slurry/rinse arm 52 having two or more supply tubes 53 to provide
one or more chemical slurries and/or water to the surface of the
polishing pad 100, 110. The slurry/rinse arm 52 delivers the one or
more chemical slurries in amounts sufficient to cover and wet the
entire polishing pad surface 100, 110. Each slurry/rinse arm 52
also includes several spray nozzles (not shown) that can provide a
high-pressure fluid rinse to the polishing pad at the end of each
polishing and/or conditioning cycle.
[0021] Two or more intermediate washing stations 55a, 55b, 55c may
optionally be positioned between adjacent polishing stations 25a,
25b, 25c to clean a substrate 10 as it passes from one polishing
station to the next.
[0022] A rotatable multi-head carousel 60 is positioned above the
lower machine base 22. The carousel 60 includes four carrier head
systems 70a, 70b, 70c, 70d. Three of the carrier head systems
function to hold substrates 10 against the polishing pads 100, 110,
during a polishing process. The fourth carrier head system
functions to move substrates 10 to/from the transfer station
27.
[0023] The carousel 60 is supported by a center post 62, and is
rotated about a carousel axis 64 by a motor assembly (not shown)
located within the machine base 22. The center post 62 also
supports a carousel support plate 66 and a cover 88.
[0024] The four carrier head systems 70a, 70b, 70c, 70d are mounted
on the carousel support plate 66 at equal angular intervals about
the carousel axis 64. The center post 62 permits the carousel motor
(not shown) to rotate the carousel support plate 66 and orbit the
carrier head systems 70a, 70b, 70c, 70d about the carousel axis
64.
[0025] Each carrier head system 70a, 70b, 70c, 70d includes a
carrier head 80. A carrier drive shaft 78 couples a carrier head
rotation motor 76 to each carrier head 80, so that the carrier head
80 can be rotated about its own axis. In addition, each carrier
head 80 may be oscillated laterally in a radial slot 72 formed in
the bottom of the carousel support plate 66.
[0026] The carrier head 80 is used to hold substrates 10 against
the polishing pads 100, 110, by evenly distributing a downward
pressure across the back surface thereof. This downward pressure
transfers torque from the drive shaft 78 to the substrates 10, and
ensures that the substrate 10 does not slip out from beneath the
carrier head 80 during the polishing process.
[0027] Chemical Mechanical Polishing Slurry for Planarizing
Organosilicate Material Layers
[0028] A polishing slurry suitable for planarizing an
organosilicate material layer is described. Organosilicate
materials comprise silicon (Si), carbon (C), oxygen (O), and
hydrogen (H). The general formula for an organosilicate material is
Si.sub.WO.sub.XC.sub.YH.sub.Z,, where w, x, y, and z are integers
that define the ratio of silicon, oxygen, carbon, and hydrogen in
the material layer.
[0029] The polishing slurry for planarizing the organosilicate
material comprises an abrasive material dispersed in a suitable
solvent. The abrasive material is preferably insoluble in the
solvent.
[0030] Water is an example of a suitable solvent for the abrasive
material. Suitable abrasive materials may include, for example,
silica (SiO.sub.2), aluminum oxide (Al.sub.2O.sub.3), zirconium
oxide (ZrO.sub.2), titanium oxide (TiO.sub.2), and combinations
thereof, among others.
[0031] The average particle size for the abrasive material is
preferably greater than about 35 nm (nanometers). Additionally, the
concentration of abrasive material in the slurry should be about
10% by weight to about 60% by weight.
[0032] Polishing rates of organosilicate material layers polished
using the polishing slurry described herein are increased by
increasing the pH of the slurry. The polishing slurry should
preferably have a pH greater than about 9.
[0033] The pH of the polishing slurry may be varied by adding a
source of hydroxyl ions to the slurry. Suitable sources of hydroxyl
ions may include potassium hydroxide (KOH), ammonium hydroxide
(NH.sub.4OH), sodium hydroxide (NaOH), magnesium hydroxide (MgOH),
calcium hydroxide (CaOH), and combinations thereof, among
others.
[0034] The source of hydroxyl ions is also believed to prevent pH
drift in the slurry during the polishing processes. pH drift is
undesirable because it may result in inconsistent polishing rates
during the polishing process.
[0035] Additionally, the polishing slurry may optionally include
one or more materials selected from the group consisting of
chelating agents, buffers, oxidizers, and corrosion inhibitors.
Suitable chelating agents may include, for example,
ethylenediaminetetraacetic acid, ethylenediamine, and
methylformamide, among others. Suitable oxidizers may include, for
example, hydrogen peroxide and ferric nitrate, among others.
Suitable corrosion inhibitors may include, for example,
benzotriazole, mercaptobenzotriazole, and 5-methyl-1-benzotriazole,
among others. Suitable buffers may include organic or inorganic
acids such as, for example, acetic acid, phosphoric acid, and
nitric acid, among others.
EXAMPLE 1 Comparative
[0036] An aqueous polishing slurry comprising about 30% by weight
silica particles having an average particle size of about 20 nm
(nanometers) was prepared. The aqueous slurry had a pH of about
2.5, buffered with ammonium hydroxide (NH.sub.4OH).
[0037] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for the organosilicate layer
was about 100 .ANG./min.
EXAMPLE 2
[0038] An aqueous polishing slurry comprising about 30% by weight
silica particles having an average particle size of about 35 nm
(nanometers) was prepared. The aqueous slurry had a pH of about 10,
buffered with ammonium hydroxide (NH.sub.4OH).
[0039] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for the organosilicate layer
was about 400 .ANG./min.
EXAMPLE 3
[0040] An aqueous polishing slurry comprising about 30% by weight
silica particles having an average particle size of about 35 nm
(nanometers) was prepared. The aqueous slurry had a pH of about 11,
buffered with ammonium hydroxide (NH.sub.4OH).
[0041] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for the organosilicate layer
was about 600 .ANG./min.
EXAMPLE 4
[0042] An aqueous polishing slurry comprising about 30% by weight
silica particles having an average particle size of about 70 nm
(nanometers) was prepared. The aqueous slurry had a pH of about 10,
buffered with ammonium hydroxide (NH.sub.4OH).
[0043] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for the organosilicate layer
was about 950 .ANG./min.
EXAMPLE 5
[0044] An aqueous polishing slurry comprising about 30% by weight
silica particles having an average particle size of about 70 nm
(nanometers) was prepared. The aqueous slurry had a pH of about 11,
buffered with ammonium hydroxide (NH.sub.4OH).
[0045] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for the organosilicate layer
was about 3080 .ANG./min.
EXAMPLE 6
[0046] An aqueous polishing slurry comprising about 22% by weight
silica particles having an average particle size of about 70 nm
(nanometers) was prepared. The aqueous slurry had a pH of about 11,
buffered with ammonium hydroxide (NH.sub.4OH).
[0047] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for the organosilicate layer
was about 2100 .ANG./min.
EXAMPLE 7
[0048] An aqueous polishing slurry comprising about 30% by weight
silica particles having an average particle size of about 70 nm
(nanometers) was prepared. The aqueous slurry had a pH of about 11,
buffered with potassium hydroxide (KOH).
[0049] An organosilicate material layer formed on a substrate was
planarized using the aqueous polishing slurry described above in
conjunction with a CMP process. The organosilicate layer was
planarized by providing the aqueous slurry to a Mirra.RTM. CMP
system (commercially available from Applied Materials, Inc., Santa
Clara, Calif.), having a IC 1400 polyurethane polishing pad therein
(commercially available from Rodel Inc., Newark, Del.). The
organosilicate layer was polished by contacting it with the
polishing slurry using a polishing pressure of about 4 psi
(pounds/square inch) and a platen speed of about 0.8 m/s
(meters/second). The polishing rate for an organosilicate layer was
about 3300 .ANG./min.
[0050] Planarization of an Organosilicate Intermetal Dielectric
Material Layer
[0051] FIGS. 2a-2b illustrate schematic cross-sectional views of a
substrate at different stages of an integrated circuit fabrication
incorporating a planarization process. In general, the substrate
200 refers to any workpiece on which processing is performed, and a
substrate structure 250 is used to denote the substrate 200
together with other material layers formed thereon. Depending on
the specific stage of processing, the substrate 200 may correspond
to a silicon wafer, or other material layer that has been formed on
the silicon wafer.
[0052] FIG. 2a, for example, illustrates a cross-sectional view of
a substrate structure 250, having conductive metal features 202 and
an organosilicate layer 204, thereon. The organosilicate layer 204
is formed between and on top of each conductive metal feature 202.
The organosilicate layer 202 is an intermetal dielectric for the
conductive metal features 202.
[0053] The conductive metal features 202 may be formed of a metal
(e.g. copper (Cu), aluminum (Al), tungsten (W)). The conductive
metal features 202 have aspect ratios greater than about 4:1. As
used in this disclosure the term aspect ratio is defined as the
ratio of the height of the metal feature to its width.
[0054] The organosilicate layer 204 may be formed using
conventional processes such as, for example, chemical vapor
deposition (CVD) techniques, spin-coating techniques, sol-gel
techniques, and dip coating techniques, among others. The thickness
of the organosilicate layer 204 is variable, depending upon the
specific stage of integrated circuit fabrication. Typically, the
organosilicate layer 204 has a thickness of about 1,000 .ANG. to
about 10,000 .ANG..
[0055] Referring to FIG. 2b, the organosilicate layer 204 is
planarized. The organosilicate layer 204 is planarized using a
polishing slurry in conjunction with a CMP system similar to that
shown in FIG. 1. The polishing slurry may be, for example, as
described above in any of Examples 2-8. Suitable polishing
conditions includes a polishing pressure of about 1 psi to about 14
psi, and a platen speed of about 0.1 m/s to about 2.0 m/s.
[0056] Although several preferred embodiments, which incorporate
the teachings of the present invention, have been shown and
described in detail, those skilled in the art can readily devise
many other varied embodiments that still incorporate these
teachings.
* * * * *