U.S. patent application number 12/766473 was filed with the patent office on 2011-06-30 for abrasive article with array of gimballed abrasive members and method of use.
This patent application is currently assigned to First Principles LLC. Invention is credited to Zine-Eddine Boutaghou, Karl G. Schwappach.
Application Number | 20110159784 12/766473 |
Document ID | / |
Family ID | 43925927 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110159784 |
Kind Code |
A1 |
Boutaghou; Zine-Eddine ; et
al. |
June 30, 2011 |
ABRASIVE ARTICLE WITH ARRAY OF GIMBALLED ABRASIVE MEMBERS AND
METHOD OF USE
Abstract
An abrasive article with an array of independently gimballed
abrasive members that are capable of selectively engaging with
nanometer-scale and/or micrometer-scale height variations and
micrometer-scale and/or millimeter-scale wavelengths of waviness,
on the surfaces of substrates. Each abrasive member maintains a
fluid bearing (air is the typical fluid) with the substrate. The
spacing and pitch of the abrasive members can be adjusted to follow
the topography of the substrate to remove a generally uniform layer
of material; to engage with the peaks on the substrate to remove
target wavelengths of waviness; and/or to remove debris and
contamination from the surface of the substrate.
Inventors: |
Boutaghou; Zine-Eddine;
(North Oaks, MN) ; Schwappach; Karl G.; (North
Oaks, MN) |
Assignee: |
First Principles LLC
|
Family ID: |
43925927 |
Appl. No.: |
12/766473 |
Filed: |
April 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61174472 |
Apr 30, 2009 |
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61187658 |
Jun 16, 2009 |
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61220149 |
Jun 24, 2009 |
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61221554 |
Jun 30, 2009 |
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61232425 |
Aug 8, 2009 |
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61232525 |
Aug 10, 2009 |
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61248194 |
Oct 2, 2009 |
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61267031 |
Dec 5, 2009 |
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61267030 |
Dec 5, 2009 |
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Current U.S.
Class: |
451/28 ; 451/540;
451/64 |
Current CPC
Class: |
B24B 37/14 20130101;
B24D 18/00 20130101; B24B 53/12 20130101; B24B 53/017 20130101 |
Class at
Publication: |
451/28 ; 451/540;
451/64 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Claims
1. An abrasive article for lapping a surface of a substrate, the
abrasive article comprising: a gimbal structure including an array
of gimbal assemblies; a plurality of abrasive members each
comprising a first surface engaged with one of the gimbal
assemblies, and a second surface, the gimbal assemblies permitting
each abrasive member to move independently in at least pitch and
roll; a preload mechanism that biases the second surfaces of the
abrasive members toward the substrate; one or more fluid bearing
features on the second surfaces of the abrasive members configured
to generate lift forces during motion of the abrasive article
relative to the substrate; and abrasive features located at an
interface of the second surface of the abrasive members with the
substrate, the abrasive features applying cutting forces to the
substrate during motion of the abrasive article relative to the
substrate.
2. The abrasive article of claim 1 wherein the abrasive features
comprise one or more of an abrasive material attached to the second
surface of the abrasive members, a slurry of free abrasive
particles located at the interface of the second surface and the
substrate, or a combination thereof.
3. The abrasive article of claim 1 wherein the gimbal structure
comprises a polymeric film with a plurality of areas of weakness
bonded to the abrasive members.
4. The abrasive article of claim 1 wherein the plurality of
abrasive members comprises an array of abrasive members molded to a
backing layer.
5. The abrasive article of claim 1 wherein the abrasive members are
arranged in a circular array, a rectangular array, an off-set
pattern, or a random pattern.
6. The abrasive article of claim 1 wherein one or more of the fluid
bearing features and the abrasive features comprise abrasive
particles disbursed in a binder comprising abrasive composites.
7. The abrasive article of claim 1 wherein the lift force maintains
the leading edges of the abrasive members further away from the
substrate than the trailing edges.
8. The abrasive article of claim 1 wherein the lift forces generate
moments on the abrasive members that is greater than moments
generated by frictional forces at interfaces of the trailing edges
with the substrate.
9. The abrasive member of claim 1 wherein clearance between the
abrasive members and the substrate is maintained between about 25
nanometers to about 100 nanometers.
10. The abrasive article of claim 1 wherein the abrasive features
comprise a nano-scale roughened surface coated with a hard
coat.
11. The abrasive article of claim 1 wherein the abrasive features
comprise nano-scale diamonds attached to the fluid bearing features
at the trailing edges of the abrasive members.
12. The abrasive article of claim 1 wherein the abrasive members
comprise one of topography following or topography removing
abrasive members.
14. The abrasive article of claim 1 comprising a plurality of gas
conduits adapted to deliver pressurized gas to one or more pressure
ports positioned opposite the substrate, the pressurized gas
generating a lift force on the abrasive members relative to the
substrate.
15. The abrasive article of claim 14 wherein the conduits
selectively deliver the source of pressurized gas to the abrasive
members.
16. The abrasive system comprising: a first abrasive article of
claim 1 positioned opposite a first surface of the substrate; a
second abrasive article of claim 1 positioned opposite a second
surface of the substrate; and a mechanism positioning the substrate
so the first and second abrasive articles can simultaneously lap
the first and second surface of the substrate.
17. A method of lapping a surface of a substrate, the method
comprising the steps of: biasing an array of individually gimballed
abrasive members toward the surface of the substrate; permitting
each gimballed abrasive member to move independently in at least
pitch and roll; creating fluid bearings between each abrasive
member and the substrate; and positioning abrasive features at an
interface of the abrasive members and the substrate, the abrasive
features applying cutting forces to the substrate during motion of
the abrasive article relative to the substrate.
18. The method of claim 17 comprising one or more of attaching the
abrasive features to the abrasive members, and depositing a slurry
of free abrasive particles at the interface of the second surface
and the substrate.
19. The method of claim 17 comprising molding an array of abrasive
members to a backing layer; and forming areas of weakness in the
backing layer adjacent the abrasive members.
20. The method of claim 17 comprising maintaining a greater lift
force at leading edges of the abrasive members than at trailing
edges.
21. The method of claim 17 wherein the fluid bearings generate
moments on the abrasive members greater than moments generated at
the interface of the abrasive members with the substrate.
22. The method of claim 17 comprising delivering a pressurized gas
to one or more pressure ports positioned opposite the substrate to
create a hydrostatic fluid bearing.
23. The method of claim 17 comprising moving the array of abrasive
members relative to the substrate to create a hydrodynamic fluid
bearings.
24. The method of claim 17 comprising the steps of: delivering a
pressurized gas to one or more pressure ports positioned opposite
the substrate to create a hydrostatic fluid bearing during a
start-up phase; and moving the array of abrasive members relative
to the substrate to create a hydrodynamic fluid bearings.
25. The method of claim 24 comprising reducing or terminating the
flow of pressurized gas after the hydrodynamic fluid bearing is
formed.
Description
RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Patent Application Nos. 61/174,472 entitled Method and
Apparatus for Atomic Level Lapping, filed Apr. 30, 2009; 61/187,658
entitled Abrasive Member with Uniform Height Abrasive Particles,
filed Jun. 16, 2009; 61/220,149 entitled Constant Clearance Plate
for Embedding Diamonds into Lapping Plates, filed Jun. 24, 2009;
61/221,554 entitled Abrasive Article with Array of Gimballed
Abrasive Members and Method of Use, filed Jun. 30, 2009; 61/232,425
entitled Constant Clearance Plate for Embedding Abrasive Particles
into Substrates, filed Aug. 8, 2009; 61/232,525 entitled Method and
Apparatus for Ultrasonic Polishing, filed Aug. 10, 2009; 61/248,194
entitled Method and Apparatus for Nano-Scale Cleaning, filed Oct.
2, 2009; 61/267,031 entitled Abrasive Article with Array of
Gimballed Abrasive Members and Method of Use, entitled Dec. 5,
2009; and 61/267,030 entitled Dressing Bar for Embedding Abrasive
Particles into Substrates, filed Dec. 5, 2009, all of which are
hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present application is directed to an abrasive article
with an array of independently gimballed abrasive members that are
capable of selectively engaging with nanometer-scale and/or
micrometer-scale height variations and micrometer-scale and/or
millimeter-scale wavelengths of waviness, on the surfaces of
substrates. Each abrasive member maintains a fluid bearing (air is
the typical fluid) with the substrate. The spacing and pitch of the
abrasive members can be adjusted to follow the topography of the
substrate to remove a generally uniform layer of material, to
engage with the peaks on the substrate to remove target wavelengths
of waviness, and/or to remove debris and contamination from the
surface of the substrate. The abrasive members can include abrasive
features, or can interact with free abrasive particles at an
interface with the substrate, or a combination thereof.
BACKGROUND OF THE INVENTION
[0003] Semiconductor wafers are typically fabricated using
photolithography, which is adversely affected by inconsistencies or
unevenness in the wafer surface. This sensitivity is accentuated
with the current drive toward smaller, more highly integrated
circuit designs. After each layer of the circuit is etched on the
wafer, an oxide layer is put down as the base for the next layer.
Each layer of the circuit can create roughness and waviness to the
wafer that is preferably removed before depositing the next circuit
layer. For many semiconductor applications the chemical mechanical
processing ("CMP") is customized for each layer. A change in a
single processing parameter, such as for example, pad design,
slurry formulation, or pressure applied by the pad, can require the
entire CMP process to be redesigned and recertified.
[0004] Magnetic media have similarly stringent planarization
requirements as data densities approach 1 Terabyte/inch.sup.2 (1
Tbit/in.sup.2) and beyond, especially on bit patterned media and
discrete track media, such as illustrated in U.S. Pat. Publication
2009/0067082. FIGS. 1 and 2 illustrate the shape of bits formed by
etching, such as ion milling or reactive etching. Note that the
tops of the bits are rounded, leading to head media spacing loss,
roughness at the rounded areas, and magnetic damage due to etching
of magnetic materials. Such bits are not viable for magnetic
recording. The uneven material increases head media spacing and
potential damage to the diamond-like-carbon overcoats. CMP
processes have proven inadequate to achieving smooth and flat tops
both before and after magnetic material deposition.
[0005] CMP is currently the primary approach to planarizing wafers,
semiconductors, optical components, magnetic media for hard disk
drives, and bit patterned or discrete track media (collectively
"substrates"). CMP uses pads to press sub-micron sized particles
suspended in the slurry against the surface of the substrate. The
nature of the material removal varies with the hardness of the CMP
pad. Soft CMP pads conform to the nanotopography and tend to remove
material generally uniformly from the entire surface. Hard CMP pads
conform less to the nanotopography and therefore remove more
material from the peaks or high spots on the surface and less
material from low spots.
[0006] Traditionally, soft CMP pads have been used to remove a
uniform surface layer, such as removing a uniform oxide layer on a
semiconductor device. Polishing a substrate with a soft pad also
transfers various features from the polishing pad to the substrate.
Roughness and waviness is typically caused by uneven pressure
applied by the pad during the polishing process. The uneven
pressure can be caused by the soft pad topography, the run out of
the moving components, or the machined imperfections transferred to
the pads. Run-out is the result of larger pressures at the edges of
the substrate due to deformation of the soft pad. Soft pad
polishing of heterogeneous layered materials, such as semiconductor
devices, causes differential removal and damage to the electrical
devices.
[0007] A CMP pad is generally of a polyurethane or other flexible
organic polymer. The particular characteristics of the CMP pad such
as hardness, porosity, and rigidity, must be taken into account
when developing a particular CMP process for processing of a
particular substrate. Unfortunately, wear, hardness, uneven
distribution of abrasive particles, and other characteristics of
the CMP pad may change over the course of a given CMP process. This
is due in part to water absorption as the CMP pad takes up some of
the aqueous slurry when encountered at the wafer surface during
CMP. This sponge-like behavior of the CMP pad leads to alteration
of CMP pad characteristics, notably at the surface of the CMP pad.
Debris coming from the substrate and abrasive particles can also
accumulate in the pad surface. This accumulation causes a "glazing"
or hardening of the top of the pad, thus making the pad less able
to hold the abrasive particles of the slurry and decreasing the
pad's overall polishing performance. Further, with many pads the
pores used to hold the slurry become clogged, and the overall
asperity of the pad's polishing surface becomes depressed and
matted.
[0008] Shortcomings of current CMP processes affect other aspects
of substrate processing as well. The sub-micron particles used in
CMP tend to agglomerate and strongly adhere to each other and to
the substrate, resulting in nano-scale surface defects. Van der
Waals forces create a very strong bond between these surface debris
and the substrate. Once surface debris form on a substrate it is
very difficult to effectively remove them using conventional
cleaning methods. Various methods are known in the art for removing
surface debris from substrates after CMP, such as disclosed in U.S.
Pat. Nos. 4,980,536; 5,099,557; 5,024,968; 6,805,137 (Bailey);
5,849,135 (Selwyn); 7,469,443 (Liou); 6,092,253 (Moinpour et al.);
6,334,229 (Moinpour et al.); 6,875,086 (Golzarian et al.);
7,185,384 (Sun et al.); and U.S. Patent Publication Nos.
2004/0040575 (Tregub et al.); and 2005/0287032 (Tregub et al.), all
of which are incorporated by reference, but have proven inadequate
for the next generation semiconductors and magnetic media.
[0009] Current processing of substrates for semiconductor devices
and magnetic media treats uniform surface layer reduction,
planarization to remove waviness, and cleaning as three separate
disciplines. The incremental improvements in each of these
disciplines have not kept pace with the shrinking feature size of
features demanded by the electronics industry.
BRIEF SUMMARY OF THE INVENTION
[0010] The present application is directed to an abrasive article
with an array of independently gimballed abrasive members that are
capable of selectively engaging with nanometer-scale and/or
micrometer-scale height variations and micrometer-scale and/or
millimeter-scale wavelengths of waviness, on the surfaces of
substrates. Each abrasive member maintains a fluid bearing (air is
the typical fluid) with the substrate. The spacing, which includes
clearance, pitch, and roll, of the abrasive members can be adjusted
to follow the topography of the substrate to remove a generally
uniform layer of material; to engage with the peaks on the
substrate to remove target wavelengths of waviness; and/or to
remove debris and contamination from the surface of the
substrate.
[0011] The gimbals permit each abrasive member to move
independently in at least pitch and roll relative to the substrate.
The fluid bearing can be hydrodynamic, hydrostatic, or a
combination thereof. The fluid can be gas, liquid, or a combination
thereof. The present abrasive article can be used before or after
features are formed on the substrates.
[0012] A hydrodynamic and/or hydrostatic bearing is used to provide
vertical, pitch and roll stiffness to the abrasive member and to
control the spacing and pressure distribution across the fluid
bearing features on the abrasive members. Adjustments to certain
variables, such as for example, the spacing (which includes minimal
spacing and attitude of the abrasive members), pitch and roll
stiffness which control attitude, the preload, and/or the abrasive
features can be used to modify the cutting force applied to the
substrate
[0013] Fluid bearing structures are fairly complex with a
substantial number of variables involved in their design. The
primary forces involved in a given fluid bearing are the gimbal
structure and the preload. The gimbal structure applies both a
pitch and roll moments to the individual abrasive members, and
hence, the fluid bearing structures. If the gimbal is extremely
stiff, the fluid bearing may not be able to form a pitch or roll
angle. The preload and preload offset (location where the preload
is applied) bias the fluid bearing toward the substrate. The
preload is typically applied by a different structure than the
gimbal structure.
[0014] Fluid bearing surface geometries play a large role in
pressurization of the bearing. Possible geometries include tapers,
steps, trenches, crowns, cross curves, twists, wall profile, and
cavities. Finally, external factors such as viscosity of the
bearing fluid and linear velocity play an extremely important role
in pressurizing bearing structures.
[0015] The individual abrasive members are capable of selectively
engaging with nanometer-scale and micrometer-scale height
variations and/or micrometer-scale or millimeter-scale wavelengths
of waviness on the surface of substrates to perform one or more of
the following three overlapping and complementary functions: 1)
following the topography of the substrate to remove a generally
uniform layer of material; 2) engaging with the peaks on the
substrate to remove target wavelengths of waviness; and/or 3)
removing debris and contamination from the surface of the
substrate. Consequently, the present abrasive articles can be
engineered to perform a wide variety of functions, including
lapping, planarization, polishing, cleaning, and burnishing
substrates.
[0016] In connection with performing any of these three functions,
the abrasive members may 1) include abrasive features positioned to
interact with the substrate, 2) interact with free abrasive
particles at the interface with the substrate, or 3) a combination
thereof. Free abrasive particles can be used with either topography
following or topography removing abrasive members.
[0017] While the abrasive features generally have a hardness
greater than the substrate, this property is not required for every
embodiment since any two solid materials that repeatedly rub
against each other will tend to wear each other away. For example,
relatively soft polymeric abrasive features molded on the abrasive
members can be used to remove surface contaminants or can interact
with free abrasive particles to remove material from the surface of
a harder substrate. As used herein, "abrasive feature" refers to a
portion of an abrasive member that comes in physical contact with a
substrate or a contaminant on a substrate, independent of the
relative hardness of the respective materials and the resulting cut
rate.
[0018] FIG. 3A is a schematic illustration of a topography
following abrasive member 1000 in accordance with an embodiment of
the present invention. The abrasive member 1000 is typically
designed to follow the topography by assuring that the trailing
edge area has the largest pressure peak. For example, the fluid
bearing can be pitched to ensure that the leading edge is spaced
substantially higher above the substrate than the trailing edge.
The trailing edge 1006 of the abrasive member 1000 applies a
cutting force to nanometer-scale and/or micron-scale height
variations 1008 on the surface 1004, while following the
millimeter-scale and/or micrometer-scale wavelengths in the
waviness 1010 on the substrate. Consequently, the abrasive member
1000 removes a generally uniform layer of material 1012 from peaks
1014 as well as valleys 1016 on the surface 1004, such as for
example, removing or controlling the thickness of an oxide layer.
As used herein, "topography following" refers to an individually
gimbaled abrasive member that generally follows millimeter-scale
and/or micrometer-scale wavelengths of waviness on a substrate,
while engaging with nanometer-scale height variations to primarily
remove a generally uniform amount of material from the surface.
[0019] FIG. 3B is a schematic illustration of a topography removing
abrasive member 1050 in accordance with an embodiment of the
present invention. The leading edge 1056 and/or trailing edge 1058
of the abrasive member 1050 applies a cutting force to peaks 1060
of millimeter-scale and/or micrometer-scale wavelengths of the
waviness 1062 on the surface 1054 of the substrate, with minimal
engagement with the valleys 1064. Consequently, the abrasive member
1050 removes more material from the peaks 1060 than the valleys
1064. As used herein, "topography removing" refers to an
individually gimbaled abrasive member that primarily removes
nanometer-scale and/or micrometer-scale height variations from
peaks of millimeter-scale and/or micrometer-scale wavelengths in
the waviness on a substrate.
[0020] FIG. 3C is a schematic illustration of a cleaning abrasive
member 1100 in accordance with an embodiment of the present
invention. The leading edge 1114 and/or the trailing edge 1106 of
the abrasive member 1100 follows the millimeter-scale and/or
micrometer-scale wavelengths in the waviness 1108 on the substrate,
while applying a cutting force to nanometer-scale and/or
micron-scale contaminants 1110. The abrasive member 1100 preferably
has a spacing 1112 such that little or no material is removed from
the surface 1104 of the substrate other than the contaminants 1110.
As used herein, "cleaning" refers to an individually gimbaled
abrasive member that generally follows millimeter-scale and/or
micrometer-scale wavelengths in the waviness of a substrate, while
primarily engaging with nanometer-scale and/or micrometer-scale
height contaminant on the surface, with little or no material
removal from the surface.
[0021] Since the abrasive members engage with nanometer-scale and
micrometer-scale structures, it is unlikely that any particular
embodiment will perform one of the topography following, topography
removing, or cleaning functions to the exclusion of the other two.
Rather, the present application adopts a probabilistic approach
that a particular embodiment is more likely to perform one
function, recognizing that the other two functions are also likely
being performed in varying degrees.
[0022] For example, the topography following abrasive member 1000
of FIG. 3A can also remove some or all of the surface contaminants
1110 of FIG. 3C. In another example, the pressure applied to peaks
1014 in FIG. 3A may be greater than in the valleys 1016, resulting
in more material removal from the peaks 1014, such as illustrated
in FIG. 3B. The topography removing abrasive member 1050 may engage
sidewalls 1066 of the peaks 1060 or the valley 1064, such as
illustrated in FIG. 3A. The cleaning abrasive member 1100 may
contact the surface 1104 and remove a generally uniform layer of
material from the substrate, along with the contaminants 1110.
Therefore, the definitions of "topography following", "topography
removing", and "cleaning" should not be read as mutually exclusive.
It should be assumed that the design parameters of the abrasive
members can be modified to emphasize more of one function than the
others.
[0023] Various abrasive features are available for the present
abrasive members, such as for example, a surface roughness formed
on the leading and/or trailing edges of the abrasive members. That
surface roughness may include a hard coat, such as for example,
diamond-like-carbon. In another embodiment, the abrasive features
may be discrete abrasive particles, such as for example, fixed
diamonds. In yet another embodiment, the abrasive features may be
structured abrasives, discussed further below.
[0024] For example, to remove all the wavelengths smaller than a
desired value, the dimensions of the abrasive members can be
greater than the target wavelengths. The wavelengths are determined
by the gas pressure profile generated by the abrasive member and
the size of the abrasive member. As a rule of thumb, the smallest
circumferential wavelength is about one-fourth the length of the
abrasive members.
[0025] The dimensions of the abrasive members and the pressure
profile due to the hydrostatic and/or hydrodynamic lift (gas and/or
liquid) determine the ability of the abrasive member to follow the
waviness of the substrate. Assuming that the abrasive members can
follow 1/4 of its size, then all wavelengths smaller than the 1/4
will cause interference with the abrasive members and material
removal will ensue due to the interactions. Portions of the
abrasive members generate a hydrodynamic lift causing predictable
waviness following capability and stabilizing force countering the
cutting forces.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0026] FIG. 1 is the configuration of a single bit on a bit
patterned media for a hard disk drive.
[0027] FIG. 2 is a perspective view of an array of bits on a bit
patterned media.
[0028] FIG. 3A is a schematic illustration of a topography
following abrasive member in accordance with an embodiment of the
present invention.
[0029] FIG. 3B is a schematic illustration of a topography removing
abrasive member in accordance with an embodiment of the present
invention.
[0030] FIG. 3C is a schematic illustration of a cleaning abrasive
member in accordance with an embodiment of the present
invention.
[0031] FIG. 4 is a schematic illustration of an idealized bit for
bit patterned media in accordance with an embodiment of the present
invention.
[0032] FIG. 5 is an exploded view of an abrasive article with
gimbaled abrasive members in accordance with an embodiment of the
present invention.
[0033] FIG. 6 is a perspective view of a preload mechanism for the
abrasive article of FIG. 5.
[0034] FIG. 7 is a perspective view of a gimbal structure for the
abrasive article of FIG. 5.
[0035] FIG. 8 is a detailed perspective view of a gimbal structure
for the abrasive article of FIG. 5.
[0036] FIG. 9 is a perspective view of the abrasive members for the
abrasive article of FIG. 5.
[0037] FIG. 10 is another perspective view of the abrasive members
for the abrasive article of FIG. 5.
[0038] FIG. 11 is a perspective view of the abrasive article of
FIG. 5 polishing a substrate in accordance with an embodiment of
the present invention.
[0039] FIG. 12 is a perspective view of the fluid bearing surface
on the abrasive members of FIG. 5.
[0040] FIG. 13 is a detailed perspective view of the fluid bearing
surface on the abrasive members of FIG. 5.
[0041] FIG. 14 is a conceptual view of an abrasive member
interacting with a substrate in a topography following mode in
accordance with an embodiment of the present invention.
[0042] FIG. 15 is a conceptual view of an abrasive member
interacting with a substrate in a topography removing mode in
accordance with an embodiment of the present invention.
[0043] FIG. 16 is a conceptual drawing of a roughened abrasive
surface in accordance with an embodiment of the present
invention.
[0044] FIG. 17 is a side sectional view of an abrasive surface with
nano-scale diamonds attached to a polymeric backing in accordance
with an embodiment of the present invention.
[0045] FIGS. 18A and 18B are conceptual illustrations of a
structured abrasive surface in accordance with an embodiment of the
present invention.
[0046] FIG. 19 is a perspective view of a unitary abrasive article
in accordance with an embodiment of the present invention.
[0047] FIG. 20 is a perspective view of the gimbal assemblies of
the abrasive article of FIG. 19.
[0048] FIG. 21 is a perspective view of the fluid bearing surfaces
of the abrasive article of FIG. 19.
[0049] FIG. 22 is an exploded view of an abrasive article with an
integral hydrostatic bearing structure in accordance with an
embodiment of the present invention.
[0050] FIG. 23 is a top view of the abrasive article of FIG. 22
with the membrane removed.
[0051] FIG. 24 is a detailed top view of the abrasive article of
FIG. 22 with the membrane removed.
[0052] FIG. 25 illustrates the fluid bearing surfaces of the
abrasive article of FIG. 22.
[0053] FIG. 26 is a perspective view of an alternate abrasive
article with fluid bearing surfaces that comprise abrasive
composites in accordance with an embodiment of the present
invention.
[0054] FIGS. 27A and 27B are side schematic illustrations of
abrasive members with various abrasive composite structures at the
fluid bearing surfaces in accordance with an embodiment of the
present invention.
[0055] FIGS. 28 and 29 illustrate an alternate abrasive article
with grooved fluid bearing surface in accordance with an embodiment
of the present invention.
[0056] FIGS. 30A and 30B are schematic illustrations of double
sided substrate processing using an abrasive article in accordance
with an embodiment of the present invention.
[0057] FIG. 31 is a perspective view of a hydrostatic abrasive
member assembly in accordance with an embodiment of the present
invention.
[0058] FIG. 32 is a bottom perspective view of an abrasive member
in accordance with an embodiment of the present invention.
[0059] FIG. 33 is a bottom perspective view of the abrasive member
of FIG. 32.
[0060] FIG. 34 is a bottom perspective view of a gimbal mechanism
in accordance with an embodiment of the present invention.
[0061] FIG. 35 is an exploded view of the hydrostatic abrasive
member assembly of FIG. 31.
[0062] FIGS. 36 and 37 are perspective views of the hydrostatic
abrasive member assembly of FIG. 31.
[0063] FIG. 38 is a bottom perspective view of the hydrostatic
abrasive member assembly of FIG. 31.
[0064] FIG. 39A is a perspective view of an annular fluid bearing
surface in accordance with an embodiment of the present
invention.
[0065] FIG. 39B is a pressure profile graph of the fluid bearing of
FIG. 39A.
[0066] FIG. 40 is a perspective view of a hydrodynamic abrasive
member in accordance with an embodiment of the present
invention.
[0067] FIG. 41 is a pressure profile graph for the abrasive member
of FIG. 40.
[0068] FIG. 42 is an exploded view of a hydrodynamic abrasive
member assembly in accordance with an embodiment of the present
invention.
[0069] FIG. 43 is a perspective view of the hydrodynamic abrasive
member assembly of FIG. 42.
[0070] FIGS. 44A-44C are various views of a cylindrical array of
abrasive members in accordance with an embodiment of the present
invention.
[0071] FIG. 45 is an exploded view of the cylindrical array of
abrasive members of FIGS. 44A-44C.
[0072] FIG. 46 is a plurality of the cylindrical array abrasive
member assemblies of FIGS. 44A-44C in accordance with an embodiment
of the present invention.
[0073] FIG. 47A is a schematic illustration of an abrasive member
for topography following applications in accordance with an
embodiment of the present invention.
[0074] FIG. 47B is a pressure profile for the abrasive member of
FIG. 47A.
[0075] FIG. 48A is a schematic illustration of an abrasive member
for topography following applications in accordance with an
embodiment of the present invention.
[0076] FIG. 48B is a pressure profile for the abrasive member of
FIG. 48A.
[0077] FIG. 49A is a schematic illustration of an abrasive member
for topography removing applications in accordance with an
embodiment of the present invention.
[0078] FIG. 49B is a pressure profile for the abrasive member of
FIG. 49A.
[0079] FIGS. 50A and 50B illustrate a hydrodynamic abrasive member
for use in CMP in accordance with an embodiment of the present
invention.
[0080] FIG. 51 illustrates a hydrostatic abrasive member for use in
CMP in accordance with an embodiment of the present invention.
[0081] FIGS. 52A and 52B illustrate an alternate abrasive article
with curve fluid bearing surfaces in accordance with an embodiment
of the present invention.
[0082] FIGS. 53A and 53B illustrate a hydrostatic version of the
abrasive article of FIGS. 52A and 52B in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0083] The entire content of U.S. Provisional Patent Application
Nos. 61/174,472, filed Apr. 30, 2009; 61/187,658, filed Jun. 16,
2009; 61/220,149, filed Jun. 24, 2009; 61/221,554, filed Jun. 30,
2009; 61/232,425, filed Aug. 8, 2009; 61/232,525, filed Aug. 10,
2009; 61/248,194, filed Oct. 2, 2009; 61/267,031, filed Dec. 5,
2009; and 61/267,030, filed Dec. 5, 2009, is hereby incorporated by
reference.
[0084] FIG. 4 is a conceptual illustration of bit 20 showing an
ideal faun for bit pattern bit. Top 22 of the bit 20 is flat
promoting constant head media spacing during read and write
operations. An abrasive article with an array of gimballed abrasive
members in accordance with an embodiment of the present invention
will permit the bit 20 of FIG. 4 to be manufactured in a production
setting.
[0085] FIG. 5 is an exploded view of an abrasive article 50 with an
array of gimballed abrasive members 52 in accordance with an
embodiment of the present invention. The abrasive article 50
includes gimbal structure 54, preload mechanism 56, and the
abrasive members 52. The abrasive article 50 can be manufactured in
circular and non-circular shapes. The abrasive members 52 can be
arranged in a regular pattern a random configuration, an off-set
pattern or a variety of other configurations.
[0086] FIG. 6 provides a detailed view of the preload mechanism 56
of FIG. 5. The preload mechanism 56 includes a series of outer
rings 58 each with a plurality of preload beams 60 configured to
apply a preload on each of the abrasive members 52 (see e.g., FIG.
11). The preload applied by the beams 60 is preferably concentrated
toward the center of the abrasive members 52 so as to not interfere
with pitch and roll motions during polishing. Alternatively, the
preload beams 60 are positioned to promote topography following or
topography removing behavior in the abrasive members 52.
[0087] FIGS. 7 and 8 illustrate the gimbal structure 54 of FIG. 5.
Framework 62 supports an array of gimbal assemblies 64. In the
illustrated embodiment, each gimbal assembly 64 includes one or
more arms 66, a cross member 68 and spring members 70 with
attachment features 72. The gimbal assemblies 64 allow each of the
abrasive members 52 to independently follow millimeter-scale and
micrometer-scale waviness of the substrate during polishing.
[0088] The gimbal assemblies 64 control the static attitude or
pitch of each abrasive member 52. The arms 66, cross members 68,
and spring member 70 permit the abrasive members 52 to move through
at least pitch and roll, while assuring adequate torque is applied
to the abrasive members 52. The members 66, 68, and 70 can be
configured to promote topography following or topography removing
behavior in the abrasive members 52. Various alternate gimbal
assemblies are disclosed in U.S. Pat. Nos. 5,774,305; 5,856,896;
6,069,771; 6,459,260; 6,493,192; 6,714,386; 6,744,602; 6,952,330;
7,057,856; and 7,203,033, which are hereby incorporated by
reference.
[0089] FIG. 9 illustrates the array of abrasive members 52 prior to
assembly onto the gimbal assemblies 64. The abrasive members 52 can
be made from a variety of materials, such as for example, metal,
ceramic, polymers, or composites thereof. The abrasive members 52
are preferably arranged in a random or off-set pattern to impart a
uniform polishing pattern onto the substrate.
[0090] The abrasive members 52 can be fabricated individually as
discrete structures or ganged together such as illustrated in FIG.
10. For example, the abrasive members 52 can be fabricated using a
mold injection process. In the embodiment of FIG. 10, spacing
structures 80 are molded between the abrasive members 52. The
spacing structures 80 position the abrasive members 52 during
assembly with the gimbal structure 54. The spacing structures 80
can be maintained or removed after assembly is completed.
[0091] FIG. 11 illustrates the assembled abrasive article 50
positioned to lap substrate 106. The substrate 106 can be a wafer,
a wafer-scale semiconductor, magnetic media for hard disk drives,
bit patterned or discrete track media, a convention disk for a hard
disk drive, or any other substrate. The preload beams 60 on the
preload mechanism 56 apply preload 82 to the abrasive members 52.
In the illustrated embodiment, the preload beams 60 apply the
preload 82 directly to the respective attachment features 72 on the
gimbal assemblies 64.
[0092] As illustrated in FIG. 11, air shearing forces between the
rotating substrate 106 and the abrasive article 50 entrain an air
cushion that applies fluid dynamic lift 108 (referred to
hereinafter as "lift" or "dynamic lift") on fluid bearing surfaces
90 on the abrasive member 52. The lift 108 can be located at the
leading edge 94 and/or the trailing edge 98, although in the
illustrated embodiment the lift 108 is concentrated at the leading
edge 94 to each abrasive member 52. In an alternate embodiment, the
substrate 106 is stationary and the abrasive article 50 rotates.
Although the most common fluid used to generate the fluid dynamic
lift 108 is air, it is also possible that the lift 108 is generated
by a liquid, such as a lubricant. As used herein, the phrase "fluid
bearing" refers generically to a fluid (i.e., liquid or gas)
present at an interface between an abrasive member and a substrate
that applies a lift force on the abrasive member. Fluid bearings
can be generated hydrostatically, hydrodynamically, or a
combination thereof.
[0093] The dynamic lift 108 causes the abrasive members 52 to
assume an attitude or pitch during the relative rotation of a
substrate 106. The gimbal assemblies 64 allow the abrasive members
52 to follow the micrometer-scale and/or millimeter-scale
wavelengths of waviness ("waviness") on the substrate 106, while
removing nanometer-scale and/or micrometer-scale height variations.
Typically, the leading edges 94 of the abrasive members 52 generate
a hydrostatic lift countering the forces generated at the
interference 104 between the trailing edge 98 and the substrate
106.
[0094] Since each of the abrasive members 52 can independently
adjust to the waviness of the substrate 106 and maintain a constant
cutting force/pressure, the amount of material removed across the
substrate 106 is substantially uniform. The present embodiment is
particularly well suited to remove a uniform amount of an oxide
layer on a semiconductor. The ability of the abrasive members 52 to
follow the waviness enables uniform material removal at a level not
attainable by conventional CMP processes. In the case of an air
bearing, it is desirable to have a boundary layer of lubricant
between the abrasive members 52 and the substrate 106.
[0095] The preload force 82 is preferably a fraction of the amount
used during conventional lapping. The present system and method
typically reduces the preload force 82 by an order of magnitude or
more. In one embodiment, the preload 82 is in the range of about
0.1 grams/millimeter.sup.2 to about 10 grams/millimeter.sup.2 of
surface being lapped, compared to about 1 kg/millimeter.sup.2 for
conventional lapping using an oil flooded lapping media.
[0096] FIGS. 12 and 13 illustrate one possible geometry of the
fluid bearing surface 90 of the abrasive members 52. The fluid
bearing surfaces 90 include various fluid bearing features 92 that
promote the creation of a fluid bearing with the substrate 106. In
the illustrated embodiment, leading edge 94 of the fluid bearing
surface 90 includes a pair of pressure pads 96A, 96B (collectively
"96") separated by gap 97. The trailing edge 98 includes pressure
pad 100. A discussion of the lift created by rotating rigid disks
is provided in U.S. Pat. No. 7,218,478, which is hereby
incorporated by reference.
[0097] In one embodiment, the pads 96, 100 can be formed with a
crown and cross-curve. The leading edges 94 of the pressure pads
96A, 96B are optionally tapered or stepped to help initiate
aerodynamic lift (see, e.g., FIG. 47A). Negative suction force
areas can be fabricated in the fluid bearing surface 90 to
stabilize the abrasive members 52 during the flying. The fluid
bearing surface 90 can also include trenches to enable higher
pressurization during the flying.
[0098] FIG. 14 is a schematic illustration of the engagement
between the abrasive members 52 with the substrate 106 in the
topography following mode in accordance with an embodiment of the
present invention. The peaks 83 and valleys 81 are intended to
illustrate nanometer-scale and/or micrometer-scale height
variations, although their size relative to the abrasive member 52
is greatly exaggerated. The micrometer-scale and/or
millimeter-scale waviness is not illustrated for the sake of
simplicity.
[0099] The valleys 81 between the peaks 83 entrain sufficient air
to permit the abrasive members 52 to "fly" over the substrate 106,
even while the trailing edge 98 is in contact with general texture
level 105 of the substrate 106.
[0100] The leading edges 94 of the abrasive members 52 are raised
above the substrate 106 due to lift 108 acting on fluid bearing
surface 86. Engagement of the abrasive members 52 with the
substrate 106 is defined by pitch angle 79A and roll angle 79B of
the abrasive members 52, and clearance 101 with the substrate
106.
[0101] The gimbal assembly 56 (see FIG. 11) provides the abrasive
members 52 with roll and pitch stiffness that balance by the roll
and pitch moments 74 generated by the lift force 108. The
frictional forces 76 generated during lapping cause a tipping
moment 78 opposite to the moment 74, causing the leading edges 94
of the abrasive members 52 to move toward the substrate 106.
[0102] In some embodiments, the lift 108 may be purely aerodynamic,
creating a stable, uniform fluid bearing. In some embodiments, the
lift 108 may be caused, in part, by lubricant 84 on the substrate
106. Abrasive members 52 in full contact with the substrate 106
experience a large amount of forces and vibrations during the
polishing process. The cutting forces and moments tend to cause
vibrations and bouncing. The preload and gimbal stiffness need to
balance the cutting forces. A lubricant 84 is desirable to keep the
frictional forces and cutting forces low enough to prevent
chattering and the like.
[0103] A boundary layer lubrication regime of a thin film a few
atoms thick adhered to the surface of the substrate 106 can be
used. Alternatively, the lapping can occur in a fully flood
environment. Consequently, the fluid dynamic lift 108 according to
the present invention may be aerodynamic and/or hydrodynamic in
nature. Discussion of the lift created by rotating rigid disks is
provided in U.S. Pat. Nos. 7,93,805 and 7,218,478, which are hereby
incorporated by reference.
[0104] The moment 74 generated by the lift 108 is preferably
greater than the moment 78 generated by frictional forces 76 at the
interface of the pad 100 with the surface of the substrate 106. The
trailing edge 98 is located below the general texture level 105 of
the substrate 106 during interference lapping. In operation, the
interference between the abrasive members 52 and the substrate 106
is essentially continuous. As used herein, "interference lapping"
refers to a clearance with an abrasive member that is less than
about half a peak-to-valley roughness of a substrate.
[0105] In one embodiment, trailing edge 98 is located at about
mid-plane 103 of the peak-to-valley roughness 109. Clearance 101
between the mid-plane 103 and the trailing edge 98 is preferably
less than half the peak-to-valley roughness 109 of the substrate
106. For example, if the peak-to-valley roughness 109 is about 50
nanometers, the clearance 101 of the abrasive members 52 is less
than about 25 nanometers. As used herein, "clearance" refers to a
distance between an abrasive member and a mid-plane of a
peak-to-valley roughness of a substrate.
[0106] In one embodiment, actuators 120 are provided to thermally
expand portions of the abrasive member 52 to perform contact
detection with the substrate 106. Contact detection refers to
bringing an actuated portion of a fluid bearing surface into
contact with a substrate, and then decreasing the actuation to
establish a desired level of interference with nanometer-scale
and/or micrometer-scale height variations on a surface of a
substrate. Contact detection between the abrasive member and the
substrate can be performed with a variety of methods including,
position signal disturbance stemming from fluid bearing modulation,
amplitude ratio and harmonic ratio calculations based on Wallace
equations, and piezoelectric based acoustic emission sensors.
Various actuators and contact detection systems are disclosed in
commonly assigned U.S. patent Ser. No. 12/424,441 (Boutaghou, et
al.), filed Apr. 15, 2009, which is hereby incorporated by
reference.
[0107] FIG. 15 is a schematic illustration of the engagement
between the abrasive members 52 with the substrate 106 in the
topography removing mode in accordance with an embodiment of the
present invention. The nanometer-scale and/or micrometer-scale
height variations are not illustrated for the sake of
simplicity.
[0108] The abrasive members 52 have a length 52A measured relative
to the motion 107 with substrate 106 that is greater than an
approximate wavelength 85 of the peaks 83. The spaces 81 between
the peaks 83 entrain sufficient air to permit the abrasive members
52 to "fly" over the substrate 106 at fly height 89 so the trailing
edge 98, and in some embodiments the leading edge 94, impacts the
peaks 83 or debris 87 located above the fly height 89. The
lubricant 84 can be a mono-layer or a flooded environment.
[0109] As with the topography following embodiment, the gimbal
assembly 56 (see FIG. 11) and the lift force 108 provide the
abrasive members 52 with sufficient pitch and roll stiffness to
counteract the tipping moment 78 caused by collisions with the
peaks 83 or surface debris 87. The interference between the
abrasive members 52 and the substrate 106 may be continuous or
intermittent. In the illustrated embodiment, the peaks 83A have
been removed by the abrasive member 52.
[0110] The abrasive members 52 may include abrasive features at the
leading edges 94 and/or trailing edges 98, abrasive particles are
interposed between the abrasive members 52 and the substrate 106,
or a combination thereof.
[0111] As illustrated in FIG. 13, the pads 96, 100 may include
abrasive features 110 that cause interference with the substrate
106 in order to remove material at the desired rate. In one
embodiment, the abrasive features 110 are texture or patterns on
the pads 96, 100, such as illustrated in FIG. 16. The abrasive
features 110 are preferably in the nanometer range to allow for
fluid bearings to be formed. In one embodiment, the abrasive
features 110 have a peak-to-peak roughness of about 20 nanometers
to about 100 nanometers. The texture 110 can be formed on the pads
96, 100 or transferred from the mold used to manufacture the
abrasive members 52.
[0112] The abrasive features 110 are preferably covered with a hard
coat, such as for example, diamond-like-carbon or other hard
overcoats depending on the application. The desired peak-to-peak
roughness after application of the hard coat varies from about 10
nanometers to about 30 nanometers to provide effective cutting. The
peak-to-valley roughness is preferably about 25 nanometers to about
50 nanometers.
[0113] Abrasive members 52 constructed from polymers are compatible
with diamond-like-carbons. Diamond-like-carbon ("DLC") thickness
varies from about 50 nanometers to about 200 nanometers to provide
a hard surface capable of burnishing the substrate. It is highly
desirable to generate DLC hardness in the range of 70-90 GPa
(Giga-Pascals) to further improve the burnishing process.
[0114] In one embodiment the DLC is applied by chemical vapor
deposition. As used herein, the term "chemically vapor deposited"
and "CVD" refer to materials deposited by vacuum deposition
processes, including, but not limited to, thermally activated
deposition from reactive gaseous precursor materials, as well as
plasma, microwave, DC, or RF plasma arc jet deposition from gaseous
precursor materials. Various methods of applying a hard coat to a
substrate are disclosed in U.S. Pat. Nos. 6,821,189 (Coad et al.);
6,872,127 (Lin et al.); 7,367,875 (Slutz et al.); and 7,189,333
(Henderson), which are hereby incorporated by reference.
[0115] In another embodiment, nano-diamonds (i.e., with a major
diameter less than 1 micrometer) are attached to the pads 96, 100
via existing processes (CVD encapsulation, brazing, adhesives,
embedding, etc.). Methods of uniformly dispersing nanometer size
abrasive grains are disclosed in U.S. Pat. Pub. No. 2007/0107317
(Takahagi et al.), which is hereby incorporated by reference.
Various geometrical features and arrangement of abrasive particles
on abrasive articles are disclosed in U.S. Pat. Nos. 4,821,461
(Holmstrand), 3,921,342 (Day), and 3,683,562 (Day), and U.S. Pat.
Pub. No. 2004/0072510 (Kinoshita et al), which are hereby
incorporated by reference. A two-step adhesion process for
attaching diamonds to the pads 96, 100 is disclosed in U.S. Pat.
Nos. 7,198,553 and 6,123,612, which are hereby incorporated by
reference.
[0116] FIG. 17 illustrates abrasive particles 340, such as
nano-scale diamonds, attached to a polyamide backing layer 342
located on the pads 96, 100 that act as the abrasive features 110
in accordance with an embodiment of the present invention. In
another embodiment, a slurry of nano-scale diamonds and adhesive
are spin coated, sprayed coated, or otherwise deposited directly
onto the pads 96, 100. A method and system for fabricating the
nano-scale diamond abrasive is disclosed in U.S. Provisional Patent
Application No. 61/187,658 entitled Abrasive Member with Uniform
Height Abrasive Particles, filed on Jun. 16, 2009, which is hereby
incorporated by reference.
[0117] FIGS. 18A and 18B illustrate perspective and side views of
an engineered surface 130 imparted to the pads 96, 100 that act as
abrasive features 110 in accordance with an embodiment of the
present invention. The engineered surface 130 is preferably
nanometer-scale or micrometer-scale. The depth of the grooves 132
with respect to the peaks 134 must be controlled to within less
than about 100 nanometers to promote the formation of a fluid
bearing with the substrate 106. The peaks 134 can be textured to
promote interference and polishing while the grooves 132 contribute
to the fluid bearing lift. If the grooves 132 are too deep
(microns), the fluid bearing generation will not be possible and
the entire system will be in contact with uncontrolled gas film
thickness. A hard coat, such as DLC, is preferably applied to the
engineered surface 130.
[0118] The engineered surface 130 allows for precise stress
management between the polished substrate and the nano-features.
Such precise stress management yields a predictable surface finish
and the gap allows for residual material to be removed. Various
engineered surfaces 130 are disclosed in U.S. Pat. Nos. 6,194,317
(Kaisaki et al); 6,612,917 (Bruxvoort); 7,160,178 (Gagliardi et
al.); 7,404,756 (Ouderkirk et al.); and U.S. Publication No.
2008/0053000 (Palmgren et al.), which are hereby incorporated by
reference.
[0119] In another embodiment, a slurry of abrasive particles is
located at the interface 104 (see, e.g., FIGS. 11, 50A, 50B, and
51), such as for example, in a standard chemical-mechanical
polishing process. The abrasive members 52 with or without abrasive
features can be used with the abrasive slurry. Various methods of
chemical-mechanical processing are disclosed in U.S. Pat. No.
6,811,467 (Beresford et al.) and U.S. Pat. Publication Nos.
2004/0072510 (Kinoshita et al.) and 2008/0004743 (Goers et al.),
which are hereby incorporated by reference.
[0120] As noted above, the abrasive features 110 generally have a
hardness greater than the substrate 106, but this property is not
required since any two solid materials that repeatedly rub against
each other will tend to wear each other away. The abrasive features
can be any portion of an abrasive member 52 that forms an interface
with a substrate 106 or a contaminant 87 on a substrate 106,
independent of the relative hardness of the respective materials
and the resulting cut rate.
[0121] In some embodiments, the abrasive members 52 are
manufactured with one or more sensors to monitor the polishing
process, such as for example, acoustic emission or friction sensor.
The present interference lapping preferably results in a surface
finish or roughness (Ra) of less than about 20 Angstrom, and more
preferably less than about 0.2 Angstrom.
[0122] In applications using full oil lubrication an interface can
be designed to form an oil hydrodynamic film. Typically, the oil
film thickness is substantially thicker than an air film thickness
due to the viscosity of the lubricant. The height or roughness of
the abrasive features on the pads 96, 100 need to be higher than
the film thickness to guarantee interference with the substrate
106. Various hydrodynamic features are disclosed in U.S. Pat. No.
6,157,515 (Boutaghou), which is hereby incorporated by reference.
Oil hydrodynamic formation requires larger pressures and preloads
82 to be applied to overcome the lift 108 generated by the oil
viscosity. Pressure relief features are preferably formed in the
pads 96, 100.
[0123] In yet another embodiment, a hydrodynamic bearing is not
(fully) formed between the abrasive members 52 and the substrate
106. The abrasive members 52 are in full contact with the substrate
106. The gimballing structure 54 allows the abrasive members 52 to
follow the waviness of the substrate 106 during polishing, but not
the nanometer-scale or micrometer-scale height variations. In the
case of a full contacting abrasive members 52, nanometer-scale or
micrometer-scale height variations is defined with respect to the
length 52A of the abrasive members 52 (see FIG. 11). Since no gas
bearing features are fabricated on this embodiment, no hydrostatic
bearing is fowled and the abrasive members 52 will not be able to
follow the nanometer-scale or micrometer-scale height variations,
and these features are removed. The following characteristic of
this structure is controlled by the friction forces and the cutting
forces emanating from the interface. The friction forces can be
minimized by fabricating contacting pads (not shown) to lower the
contact area while providing a low friction interface especially in
the presence of a lubricant.
[0124] FIGS. 19-21 illustrate a fully integrated gimbaled abrasive
article 150 in accordance with an embodiment of the present
invention. Preload structure 152 includes circumferential ribs 154
and radial ribs 156 to impart a desired preload onto abrasive
members 158. Gimbal assemblies 160 include a collection of flexible
ribs 162, 164 connecting the preload structure 152 to the abrasive
members 158. The abrasive article 150 is preferably fabricated as a
single unit, such as by injection molding. The fabrication process
can include multiple mold injection steps to meet the system
requirements.
[0125] Instead of applying the preload directly to the abrasive
members 158, the preload is applied by the preload structure 152
through the gimbal assemblies 160. This configuration is ideal for
low preload applications. Care must be taken not to cause excessive
deformation of the gimbal assemblies 160 during preload
applications. FIG. 21 illustrates fluid bearing features 164
fabricated on the abrasive members 158, such as discussed above.
The fluid bearing surfaces 164 can include any of the abrasive
features discussed herein.
[0126] FIGS. 22-25 illustrate an alternate abrasive article 200
with an array of abrasive members 212 having an integrated
hydrostatic bearing structure 202 in accordance with an embodiment
of the present invention. Membrane 216 seals gas conduits 204 in
the bearing structure 202.
[0127] FIGS. 23 and 24 illustrate the integrated hydrostatic
bearing structure 202 without sealing membrane 216 shown. Gas
conduits 204 are fabricated in gimbal assembly 206 and along
preload ribs 208. Holes 210 extending through the abrasive members
212 to fluid bearing surfaces 214 (see FIG. 25). The gas conduits
204 are externally pressurized to provide a hydrostatic bearing on
each abrasive member 212. The fluid bearing surfaces 214 can
include any of the abrasive features discussed herein.
[0128] As best illustrated in FIG. 25, fluid bearing surfaces 214
of the abrasive members 212 are fabricated with button pressure
ports 218 to form a hydrostatic bearing on each abrasive member
212. The hydrostatic bearing generated at each fluid bearing
surface 214 is designed to counter the cutting forces during the
polishing process. For illustrative purposes, a button bearing
design is shown. See also, FIG. 39A. Additional configurations can
easily be adapted such as multiple ports onto each abrasive member
212 to enable the abrasive member to form a pitch and roll
moment.
[0129] In one preferred embodiment, a pressure port 218 is located
near the leading edges 220 to increase the pitch of the abrasive
members 212 for topography following applications. In another
embodiment, pressure ports 218 are located at both the leading
edges 220 and trailing edges 222 of the abrasive members 212 to
configure the pitch for topography removing applications.
[0130] The abrasive article 200 is particularly useful when the
relative speed between the substrate and the abrasive members 212
is not high enough to form a fluid bearing or hydrodynamic film.
The external pressure applied to the abrasive members 212 forms a
hydrostatic film capable of following the substrate waviness and
countering the cutting forces emanating from the interference
between the peaks of the abrasive member 200 and the substrate.
[0131] The hydrostatic fluid bearing may be used in combination
with a hydrodynamic fluid bearing. In one embodiment, the
hydrostatic fluid bearing is used during start-up rotation and/or
ramp-down of the abrasive article 200 relative to a substrate.
[0132] In another embodiment, the hydrostatic fluid bearing is used
simultaneously with a hydrodynamic fluid bearing. The pressure
ports 218 located near the inner edge 224 and outer edge 226 of the
abrasive article 200 can be pressurized to offset loss of pressure
at the fluid bearing in those locations. Consequently, the pressure
of the fluid bearing surfaces 214 across width 228 of the abrasive
article 200 can be precisely controlled to reduce run out.
[0133] FIG. 26 illustrates an alternate abrasive article 300 in
which the fluid bearing features 302A, 302B, 302C ("302") comprise
abrasive particles 304 dispersed within a binder 306 in accordance
with an embodiment of the present invention. The abrasive
composites 312 act as the abrasive features in the illustrated
embodiment.
[0134] In the illustrated embodiment, the fluid bearing features
302 are coextensive with abrasive members 308. The abrasive members
308 are also preferably coextensive with the backing layer 310. The
term "coextensive" refers to attachment, bonding, or permeation of
the materials comprising the various components 302, 308, and 310.
Additional details concerning the general characteristics of the
abrasive composites and methods of manufacture can be found in U.S.
Pat. Nos. 5,152,917 (Pieper et al.); 5,958,794 (Bruxvoort),
6,121,143 (Messner et al.) and U.S. Patent Publication Nos.
2005/0032462 (Gagliardi et al.) and 2007/0093181 (Lugg et al.), all
of which are hereby incorporated by reference.
[0135] The abrasive particles 304 are optionally located only at
the fluid bearing feature 302A at the trailing edge 316, but can
optionally be provided at the fluid bearing features 302B, 302C at
the leading edge 318 of the abrasive members 308. The abrasive
particles 304 may be non-homogeneously dispersed in a binder 306,
but it is generally preferred that the abrasive particles 304 are
homogeneously dispersed in the binder.
[0136] The abrasive particles 304 may be associated with at least
one fluorochemical agent. The fluorochemical agent may be applied
to the surface of the abrasive particles 304 by mixing the
particles in a fluid containing one or more fluorochemical agents,
or by spraying the one or more fluorochemical agents onto the
particles. The fluorochemical agents associated with abrasive
particles may be reactive or unreactive.
[0137] Fine abrasive particles 304 are preferred for the
construction of the fluid bearing features 302. The size of the
abrasive particles is preferably less than about 1 micrometer and
typically between about 10 nanometers to about 200 nanometers. The
size of the abrasive particle 304 is typically specified to be the
longest dimension. In almost all cases there will be a range or
distribution of particle sizes. In some instances, it is preferred
that the particle size distribution be tightly controlled such that
the resulting fixed abrasive article provides a consistent surface
finish on the wafer. The abrasive particles may also be present in
the form of an abrasive agglomerate. The abrasive particles in each
agglomeration may be held together by an agglomerate binder.
Alternatively, the abrasive particles may bond together by
inter-particle attraction forces. Examples of suitable abrasive
particles 304 include fused aluminum oxide, heat treated aluminum
oxide, white fused aluminum oxide, porous aluminas, transition
aluminas, zirconia, tin oxide, ceria, fused alumina zirconia, or
alumina-based sol gel derived abrasive particles.
[0138] The backing layer 310 preferably includes a plurality of
areas of weakness 314 that permit the abrasive members 308 to
gimbal (i.e., pitch, roll, and yaw) with respect to the backing
layer 310. The areas of weakness 314 can be perforations, slits,
grooves, and/or slots formed in the backing layer 310. The areas of
weakness 314 also permit the passage of the liquid medium before,
during, or after use.
[0139] The backing layer 310 is preferably uniform in thickness. A
variety of backing materials are suitable for this purpose,
including both flexible backings and backings that are more rigid.
Examples of typical flexible abrasive backings include polymeric
film, primed polymeric film, metal foil, cloth, paper, vulcanized
fiber, nonwovens and treated versions thereof and combinations
thereof. One preferred type of backing is a polymeric film.
Examples of such films include polyester films, polyester and
co-polyester films, microvoided polyester films, polyimide films,
polyamide films, polyvinyl alcohol films, polypropylene film,
polyethylene film, and the like. The thickness of the polymeric
film backing generally ranges between about 20 to about 1000
micrometers, preferably between about 50 to about 500
micrometers.
[0140] A preferred method for making the abrasive composites 312
having precisely shaped abrasive composites 312 is described in
U.S. Pat. No. 5,152,917 (Pieper et al) and U.S. Pat. No. 5,435,816
(Spurgeon et al.), both incorporated herein by reference. Other
descriptions of suitable methods are reported in U.S. Pat. Nos.
5,437,754; 5,454,844 (Hibbard et al.); U.S. Pat. No. 5,437,7543
(Calhoun); and U.S. Pat. No. 5,304,223 (Pieper et al.), all
incorporated herein by reference.
[0141] Production tools for making the abrasive members 308 may be
in the form of a belt, a sheet, a continuous sheet or web, a
coating roll such as a rotogravure roll, a sleeve mounted on a
coating roll, or die. The production tool may be made of metal,
(e.g., nickel), metal alloys, or plastic. The production tool is
fabricated by conventional techniques, including photolithography,
knurling, engraving, hobbing, electroforming, or diamond turning.
For example, a copper tool may be diamond turned and then a nickel
metal tool may be electroplated off of the copper tool.
Preparations of production tools are reported in U.S. Pat. No.
5,152,917 (Pieper et al.); U.S. Pat. No. 5,489,235 (Gagliardi et
al.); U.S. Pat. No. 5,454,844 (Hibbard et al.); U.S. Pat. No.
5,435,816 (Spurgeon et al.); PCT WO 95/07797 (Hoopman et al.); and
PCT WO 95/22436 (Hoopman et al.), all incorporated herein by
reference. In an alternate embodiment, the abrasive members 308 are
used in combination with the gimbal mechanism such as disclosed in
FIG. 5.
[0142] FIG. 27A is a side view of the abrasive members 308 of FIG.
26 in which the abrasive particles 304 do not extend above surface
320 of the fluid bearing features 302. FIG. 27B illustrates an
alternate embodiment in which some of the abrasive particles 304
extend above the surface 320 of the fluid bearing features 302. A
hard coat, such as diamond-like-carbon is optionally applied to the
protruding abrasive particles 304 of FIG. 27B. In both embodiments,
the backing layer 310 includes a plurality of areas of weakness
314.
[0143] Due to the rigidity of the abrasive members 308, a preload
322 can be applied directly to rear surfaces 324 of the backing
layer 310 opposite the abrasive members 308, such as for example,
the preload mechanism 56 illustrated in FIG. 5. The areas of
weakness 314 permit the abrasive members 308 to gimbal relative to
the backing layer 310. In another embodiment, the abrasive members
308 are combined with the gimbal structure 54 and the preload
mechanism 56 of FIG. 5 so that the backing layer 310 does not
provide the gimbal function.
[0144] In one embodiment, one or more protrusions 326 are
optionally located near leading edge 318 to prevent the fluid
bearing surfaces 302B, 302C from impacting the substrate. The
protrusions 326 can be created from a variety of materials, such as
for example, diamond-like-carbon.
[0145] FIGS. 28 and 29 are perspective views of an alternate
abrasive article 350 in which the fluid bearing features 352A,
352B, 352C ("352") include a plurality of grooves 354 oriented
generally parallel to the direction of travel 356 of the abrasive
members 358 relative to the substrate. The grooves 354 release
fluid located at the interface between the fluid bearing features
352, reducing the lift on the abrasive members 358.
[0146] The grooves 354 reduce the fly height of the abrasive
members 358. In applications where the fluid is a liquid, the
grooves 354 permit a low fly height and/or a low preload. The
grooved abrasive members 358 are particularly well suited to fully
flooded applications.
[0147] The depth of the grooves 354 must be sufficient to reduce
hydrodynamic pressure between the abrasive members 358 and the
substrate. In most cases, the grooves 354 have a depth of greater
than about 20 micrometers.
[0148] By reducing the hydrodynamic film, it is possible to use
lubricants with a higher viscosity and/or maintain a low preload on
each abrasive member 358, while still achieving interference with
the substrate. In some applications, the grooves 354 allow a
reduction in the hydrodynamic film while allowing the use of
nano-scale diamonds attached to the fluid bearing features 352.
[0149] In one embodiment, nano-scale diamonds attached to a
polymeric film, such as illustrated in FIG. 14B, are attached to
the fluid bearing features 352. The grooves 354 permit the load on
the abrasive members 358 to be sufficiently low so as to not
substantially deform the polymeric film 342. In another embodiment,
the fluid bearing features 352 are grooved abrasive composites.
[0150] Designing length 360 of the abrasive members 358 to be
greater than the target wavelength permits the abrasive members 358
to interact with the peaks of the waviness for topography removing
applications. Alternatively, reducing the length 360 will cause the
abrasive members 358 to follow the contour of the waviness and
provide more uniform material removal for topography following
applications.
[0151] The grooves 354 also permit the fly height to be engineered
for particular applications. Assuming all other processing
variables are held constant, increasing the size or number of
grooves 354 reduces fly height, and hence, increases interference
between the substrate.
[0152] The fly height of the abrasive members 358 above the
substrate can also be engineered, such as by changing the size and
shape of the fluid bearing features 352. Some variables critical to
fly height include the size and shape of gap 362 between the fluid
bearing features 352A, 352B, the length 364 and width 366 of the
fluid bearing features 352A, 352B, and the length 368 and width 370
of the fluid bearing features 352C.
[0153] In one embodiment, a series of different abrasive articles
350 are designed with different sized abrasive members 358 and/or
fluid bearing features 352 used to polish a substrate. For example,
the abrasive article 350 may initially target peaks only, followed
by an abrasive article 350 designed to follow the contour.
[0154] FIGS. 30A and 30B are schematic illustrations of a pair of
abrasive articles 400, 402 simultaneously lapping opposite surfaces
404, 406 of substrate 408 in accordance with an embodiment of the
present invention. The fixing process used to mount substrates
(e.g., wax mounting, vacuum chucking, etc.) causes topology from
the backside of the substrate to be transmitted to the front side
and causes nanotopography. While free mounting of substrates does
not transmit nanotopography, substrate flatness is not guaranteed.
The best flatness and nanotopography is obtained using double-sided
polishing. Since the substrate is polished in a free state,
nanotopography is minimized and good flatness is achieved. The
substrate 408 is preferably gripped by its edges 410 by mechanism
411 and rotated about axis 412, such as disclosed in U.S. Pat. Nos.
7,185,384 (Sun et al.); 6,334,229 (Moinpour et al.); and 6,092,253
(Moinpour et al.), all of which are incorporated by reference.
[0155] In the embodiment of FIG. 30A, leading edges 414 of the
individual abrasive members 416 are illustrated below the axis 412,
and trailing edges 418 above the axis 412. The fluid bearings
generated by the opposing abrasive articles 400, 402 generate
opposing forces 420, 422 that permit simultaneous lapping of both
surfaces 404, 406 with minimum deformation of the substrate 408.
Simultaneously lapping both surfaces 404, 406 of a substrate 406
held between opposing fluid bearings provides superior results over
current lapping techniques. In another embodiment, the abrasive
articles 400, 402 are rotated relative to the substrate 408.
[0156] In the embodiment of FIG. 30B, leading edges 414 of the
abrasive articles 402 are illustrated above the axis 412 permitting
the abrasive articles to be counter rotated. Counter rotating the
abrasive articles 400, 402 may permit the substrate 408 to be free
floating. In this embodiment, the mechanism 411 acts as a barrier
to the edges 410 to maintain the substrate 408 generally concentric
with the abrasive articles 400, 402, but does not otherwise
restrain the substrate 408.
[0157] FIG. 31 is a bottom perspective view of hydrostatic abrasive
article 550 with an array of hydrostatic abrasive members 552 in
accordance with an embodiment of the present invention. External
pressure source 554 is applied to each of the abrasive members 552
to control clearance 556 with the substrate 558. Preload 612 biases
the abrasive members 552 toward the substrate 558. Polishing is
accomplished by relative motion between the hydrostatic abrasive
article 550 and the substrate 558, such as linear, rotational,
orbital, ultrasonic, and the like. In one embodiment, that relative
motion is accomplished with an ultrasonic actuator such as
disclosed in commonly assigned U.S. Provisional Patent Application
Ser. No. 61/232,525, entitled Method and Apparatus for Ultrasonic
Polishing, filed Aug. 10, 2009, which is hereby incorporated by
reference.
[0158] FIG. 32 illustrates an embodiment of an individual abrasive
member 552 with both hydrostatic and hydrodynamic fluid bearing
capabilities designed into bottom surface 560 in accordance with an
embodiment of the present invention. The bottom surface 560 of the
abrasive member 552 includes both air bearing features 564 and
pressure ports 566.
[0159] Leading edge 562 of the abrasive member 552 includes a pair
of fluid bearing pads 564A, 564B (collectively "564") each with at
least one associated pressure port 566A, 566B. Trailing edge 570
also includes a pair of fluid bearing pads 572A, 572B (collectively
"572") and associated pressure ports 566C, 566D. The fluid bearing
surfaces 574 on the trailing edge 570 enhance the stability of the
abrasive member 552 at the interface with a surface defect.
[0160] The fluid bearing pads 572 on the trailing edge 570 have
less surface area than the fluid bearing pads 564 at the leading
edge 562. Consequently, the leading edge 562 typically flies higher
than the trailing edge 570, which sets the pitch of the abrasive
member 552 relative to the substrate 558 (see, e.g., FIG. 14). The
trailing edge 570 is typically designed to be in interference with
the surface defects on the substrate 558. Both leading edge and
trailing edge structures 564, 572 contribute to holding the
abrasive member 552 at a desired clearance 556 from the substrate
558 and controlling the amount of interference with surface
defects. It is also possible to control the pressure applied to the
pressure ports 566A, 566B at the leading edge 562 to increase or
decrease the pitch of the abrasive member 552.
[0161] The hybrid abrasive member 552 can operate with a
hydrostatic fluid bearing and/or a hydrodynamic fluid bearing. The
hydrostatic pressure ports 566 apply lift to the abrasive member
552 prior to movement of the substrate 558. The lift permits
clearance 556 to be set before the substrate 558 starts to move.
Consequently, preload 612 does not damage the substrate 558 during
start-up. Once the substrate 558 reaches its safe speed and the
hydrodynamic fluid bearing is fully formed, the hydrostatic fluid
bearing can be reduced or terminated. The procedure can also be
reversed at the end of the polishing process.
[0162] In another embodiment, both the hydrostatic and hydrodynamic
fluid bearings are maintained during at least a portion of the
polishing process. The pressure ports 566 can be used to supplement
the hydrodynamic bearing during the polishing process. For example,
the pressure ports 566 may be activated to add stiffness to the
fluid bearing during initial passes over the substrate 558. The
hydrostatic portion of the fluid bearing is then reduced or
terminated part way through the polishing process. The pressure
ports 566 can also be used to adjust or fine tune the attitude
and/or clearance of the abrasive members 552 relative to the
substrate 558.
[0163] As best illustrated in FIG. 35, the abrasive members 552 are
preferably formed in an array with a spacing structure 576. In one
embodiment, the abrasive members 552 and spacing structure 576 are
injection molded from a polymeric material to form an integral
structure. Alternatively, discrete abrasive members 552 can be
bonded or attached to the gimbal mechanisms 590. The bottom surface
560 optionally includes intermediate pad 574 to increase the
cutting surfaces to remove surface defects. To enhance the cutting
action abrasive features are optionally fabricated onto the pads
564, 572, 574, as discussed above.
[0164] FIG. 33 illustrates a top view of the abrasive member 552 of
FIG. 32. Pressure cavity 580 is fabricated on the back surface 582
of the abrasive member 552 that acts as a plenum for the delivery
of pressurized gas out through the pressure ports 566.
[0165] FIG. 34 illustrates a gimbal assembly 588 that contains an
array of gimbal mechanisms 590 of FIG. 31. Each gimbal mechanism
590 includes four L-shaped springs 592A, 592B, 592C, 592D
(collectively "592") that suspend the abrasive members 552 above
the substrate 558 in accordance with an embodiment of the present
invention. Box-like structure 594 is optionally fabricated on each
gimbal structure 590 to help align the abrasive members 552. The
box-like structure 594 also includes a port 596 that delivers the
pressurized gas to the backs of the abrasive members 552 and out
the pressure ports 566.
[0166] FIG. 35 is an exploded view of the hydrostatic abrasive
article 550 of FIG. 31. External pressure source 554 delivers
pressurized gas (e.g., air) to plenum 600 in preload structure 602.
Cover 604 is provided to enclose the plenum 600. A plurality of
pressure ports 606 in the plenum 600 are fluidly coupled to the
pressure ports on the gimbal mechanism 590 by bellows couplings
608.
[0167] Springs 610 transfer the preload 612 from the preload
structure 602 to each of the gimbal mechanisms 590. The externally
applied load 612, the geometry of the hydrostatic bearing 564, 572,
and the external pressure control the desired spacing 556 between
the abrasive members 552 and the substrate 558.
[0168] Holder structure 620 is attached to the preload structure
602 by stand-offs 622. The holder structure 620 sets the preload
624 applied on each abrasive member 552 and limits the deformation
of the gimbal mechanisms 590 in order to avoid damage while the
individual preload 624 is applied. An adhesive layer (not shown)
attaches the abrasive members 552 to the gimbal box-like structure
594. The external preload 612 applied to the array of abrasive
members 552 is greater than or equal to the preloads 624 generated
by the independently suspended abrasive members 552 in order to
allow the gimbal mechanisms 590 to comply with the substrate 558
and not interfere with the holder structure 620.
[0169] FIGS. 36 and 37 illustrates dimple structure 630 interposed
between the springs 610 and the gimbal mechanism 590. The dimple
structure 630 delivers the preload as a point source. Offset from
the springs 610 and the dimple 630 is a flexible bellow 608 that
delivers the external pressure to each individual abrasive member
552 via the gimbal mechanisms 590. The gimbal mechanisms 590,
preload structure 602, and holder structure 620 can also be used in
a hydrodynamic application without the pressure ports 566 and
bellows couplings 608.
[0170] FIG. 38 is a bottom view of the hydrostatic abrasive article
550 with the individual abrasive members 552 organized in a serial
fashion. Note that other configurations can easily be accommodated,
such as for example an off-set or random pattern.
[0171] Alternate hydrostatic slider height control devices are
disclosed in commonly assigned U.S. Provisional Patent Application
Ser. No. 61/220,149 entitled Constant Clearance Plate for Embedding
Diamonds into Lapping Plates, filed Jun. 24, 2009 and Ser. No.
61/232,425 entitled Dressing Bar for Embedding Abrasive Particles
into Substrates, which are hereby incorporated by reference. A
mechanism for creating a hydrostatic fluid bearing for a single
abrasive member attached to a head gimbal assembly is disclosed in
commonly assigned U.S. Provisional Patent Application Ser. No.
61/172,685 entitled Plasmon Head with Hydrostatic Gas Bearing for
Near Field Photolithography, filed Apr. 24, 2009, which is hereby
incorporated by reference.
[0172] Controlling the magnitude of the pressure applied to the
abrasive members changes the clearance between the substrate and
the abrasive members. The frequency response of the system is
independent of the compliance of the material selected for the
abrasive member but can be engineered by the selection of the
gimballing mechanism, including the hydrostatic bearing design. The
pressure generated by the hydrostatic bearing contributes to
forming pitch, z-height, and roll forces that counter the cutting
forces emanating from surface defects interaction and potential
contact with the substrate.
[0173] FIG. 39A illustrates a circular hydrostatic abrasive member
640 in accordance with an embodiment of the present invention. The
cylindrical shaped recess 642 and pressure port 644 create a
generally constant pressure at center, with a logarithmical
decaying pressure radially outward.
[0174] FIG. 39B is a graphical illustration of the pressure profile
for the circular abrasive member of FIG. 39A. The circular abrasive
member has a generally constant pressure profile 646 in center
region 642 adjacent to the pressure port 644. The pressure at the
outer edges 648 of the abrasive member matches ambient pressure.
This pressure profile operates similar to a spring. One embodiment
envisions a cylindrical shaped recess, such as 642, at each corner
of the abrasive member of FIG. 31.
[0175] FIG. 40 illustrates a hydrodynamic abrasive member 650 in
accordance with an embodiment of the present invention. The
abrasive member 650 is generally the same as discussed above,
except that no pressure ports are required. Fluid bearing surfaces
652A, 652B, 652C, 652D, 652E (collectively "652") located along the
leading edge 654 and trailing edge 656 create hydrodynamic lift
between the abrasive member 650 and the substrate 658 (see FIG.
43). The air for the fluid bearing enters along the leading edge
654 and exits along the trailing edge 656. The fluid bearing
surfaces 652 also enhance the stability at the interface and a
cutting surface to remove surface defects from the substrate
658.
[0176] The conditions promoting hydrodynamic lift are bearing
design, gas/liquid shearing, and linear velocity of the abrasive
member 650 relative to the substrate 658. Such conditions can
promote the formation of a fluid film (oil, water, gas) between the
abrasive member and the substrate. The relative velocity is
obtained by rotating the substrate 658 and/or the abrasive members
650.
[0177] Hydrodynamic abrasive article 670 of the present embodiment
is best illustrated in FIGS. 42 and 43. An array of abrasive
members 650 is attached to preload structure 660 by an array of
gimbal mechanisms 662. Preload 664 is transmitted to the gimbal
mechanisms 662 by dimpled springs 666, generally as discussed
above. The suspended abrasive members 650 have a static pitch and
roll stiffness through the hydrodynamic fluid bearing and a
z-stiffness through the gimbal mechanisms 662. The fluid bearing
surfaces 652 can include any of the abrasive features discussed
herein.
[0178] The hydrodynamic fluid film formed at each abrasive member
650 controls the dynamic response of the structure. The frequency
response of such system can be designed to be in the 10-100 kHz
range, which is sufficient to comply with the substrate surface 668
and to interact with surface debris. The spacing between the
polishing surfaces 652C, 652D, 652E can be controlled to cause
interaction with surface defects with little to no material removal
from the substrate 658. In order for the fluid bearing surfaces 652
to develop a stable interface, the hydrodynamic forces must be
greater than external disturbances caused by the interference or
contact between the polishing surfaces 652C, 652D, 652E and the
surface defects.
[0179] FIG. 41 illustrates a pressure curve generate by the
abrasive member 650 of FIG. 40. Note that the pressure vanishes to
atmospheric pressure at the edges of the fluid bearing surfaces and
builds-up to a maximum 672 at the trailing edge fluid bearing
surfaces 652C, 652D, 652E. Each of the fluid bearing surfaces
pressurizes under the shear force of the lubricating fluid (air or
liquid) to generate a force contributing to counter the preload 664
and the cutting forces emanating from the polishing or polishing
operation. The pressure formed under the fluid bearing surfaces
maintains a certain clearance between the substrate 658 and the
abrasive members 650.
[0180] FIGS. 44A-44C illustrate an abrasive member assembly 750
with an array of abrasive members 768 arranged in a cylindrical
array in accordance with an embodiment of the present invention.
FIG. 45 is an exploded view of the abrasive member assembly 750 of
FIGS. 44A-44C.
[0181] The abrasive member 750 preferably forms a contact interface
with the substrate, although this embodiment may be used with a
hydrodynamic or hydrostatic bearing. Cylinder preload fixture 752
includes a plurality of dimpled spring members 754 that apply an
outward radial preload 756 on each gimbal mechanism 758. The
preload 756 is transferred by dimple member 760 acting on rear
surface 762 of the gimbal mechanisms 758. The gimbal mechanisms 758
are interconnected into a gimbal assembly 764 by support structure
766. The individual abrasive members 768 are attached to the gimbal
mechanisms 758.
[0182] FIG. 46 illustrates a plurality of the abrasive member
assemblies 750 of FIG. 45 arranged in a stack configuration 782.
The cylindrical structure can be used to clean planar or non-planar
substrates. In one embodiment, axis of rotation 780 is oriented
parallel to the surface 784 of the substrate 786. The stacked
configuration 782 is optionally rotated while engaged with the
substrate 786. The substrate 786 can be stationary or moving.
[0183] A hydrostatic bearing can optionally be generated at the
interface of the abrasive members 768 and the substrate via
external pressurization means, as discussed above. The hydrostatic
approach permits the abrasive members 768 to hover over the
substrate surface at any desired clearance while still being able
to interact and remove surface defects. A stable contacting
interface can also be used with the abrasive members 768. The
abrasive members 768 can either be a porous sponge-like material or
a hard coated slider. The gimbal mechanisms 758 and preload
mechanisms 754 permit the abrasive members 768 to follow the
run-out and waviness of the substrate while the abrasive members
768 intimately contact and clean the substrate.
[0184] Alternate methods of controlling the height of the abrasive
members above the substrate are disclosed in commonly assigned U.S.
Provisional Patent Application Ser. No. 61/220,149 entitled
Constant Clearance Plate for Embedding Diamonds into Lapping
Plates, filed Jun. 24, 2009 and Ser. No. 61/232,425 entitled
Dressing Bar for Embedding Abrasive Particles into Substrates,
which are hereby incorporated by reference. A mechanism for
creating a hydrostatic fluid bearing for a single abrasive member
attached to a head gimbal assembly is disclosed in commonly
assigned U.S. Provisional Patent Application Ser. No. 61/172,685
entitled Plasmon Head with Hydrostatic Gas Bearing for Near Field
Photolithography, filed Apr. 24, 2009, which is hereby incorporated
by reference.
[0185] Controlling the magnitude of the pressure applied to the
abrasive members changes the clearance between the substrate and
the abrasive members. The frequency response of the system is
independent of the compliance of the material selected for the
abrasive members but can be engineered by the selection of the
gimballing mechanism, including the hydrostatic bearing design. The
pressure generated by the hydrostatic bearing contributes to
forming pitch, z-height and roll forces that counter the cutting
forces emanating from surface defects interaction and potential
contact with the substrate.
Example 1
[0186] FIG. 47A illustrates an abrasive member 800 modeled for
topography following applications. The leading edge 802 includes a
plurality of discrete features 804 separated by cavities 806 that
permit air flow and particles to enter. The cavity depth 812 is
about 2 micrometers to about 3 micrometers to promote a negative
suction force.
[0187] The leading edge pads 804 are formed with rounded surfaces
816 to promote the redistribution of debris and lubricant. This
example of a low contact force abrasive member 800 includes leading
edge step 818 that increases lift at the leading edge 802.
[0188] FIG. 47B is a graphical illustration of the contact pressure
of the abrasive member 800 with the substrate. The leading edge
pressure 802A is preferably zero. Trailing edge pressure 810A shows
a minor negative suction force. Upon application of large loads
(e.g., up to 12 grams) the leading edge 802 does not contact the
substrate, while the trailing edge 810 follows the topography of
the substrate.
[0189] Table 1 shows that the leading edge 802 clears the
substrate, while the trailing edge 810 is in contact. This approach
permits the trailing edge 810 to follow the substrate waviness. The
leading and trailing edge pressurization contribute to the
stability of the design during asperity interactions and debris
removal. This design is ideal for cleaning debris and removing nano
level amounts of material in the presence of a thin film
lubricant.
TABLE-US-00001 TABLE 1 Negative Positive Contact Pitch (micro
Preload pressure pressure force radians)/Fly (grams) (grams)
(grams) (grams) height (nm) 3 -0.89 3.88 0 318/24 5 -1.03 6.02 0.01
233/10 8 -1.18 8.93 0.24 163/4.2 10 -1.27 10.72 0.54 130/2.5 12
-1.31 12.47 0.83 113/1.7
Example 2
[0190] FIG. 48A illustrates an abrasive member 820 modeled for
topography following applications. The leading edge 822 includes a
plurality of discrete features 824 separated by slots 826 that
permit air flow and particles to enter. This example of a low
contact force abrasive member 820 includes leading edge step 828
and extended sides 830 to increase the negative pressure force
(suction force). The leading edge step 828 has a depth of about 0.1
micrometers to about 0.5 micrometers to promote the formation of
higher pressure at the leading edge 822. Note that the trailing
edge 832 is formed of discrete pads 834 to reduce the spacing
between the substrate and the abrasive member, and to allow for
circulation of lubricant and debris.
[0191] FIG. 48B is a graphical illustration of the contact pressure
for the abrasive member 820 against the substrate. The contact
forces are concentrated at the pads 834 located at trailing edge
832. The negative pressure saturates around 3.5 grams while the
positive pressure increases to balance the applied load while
keeping a pitch angle causing the spacing between the leading edge
822 and the substrate. The design provides very good contact
stiffness contributing to the stability of the abrasive member. The
abrasive member 820 has a pitch that permits the leading edge 822
to remain above the substrate. This design transmits about 15
percent of the applied load to the substrate, which is greater than
the force in Example 1. This design is ideal for cleaning and
removing debris from wafers in the presence of a thin film
lubricant. Nanometer-level removal from this design is
expected.
[0192] Table 2 provides a summary of various performance parameters
for the abrasive member as a function of preload.
TABLE-US-00002 TABLE 2 Negative Positive Contact Pitch (micro
Preload pressure pressure force radians)/Fly (grams) (grams)
(grams) (grams) height (nm) 3 -2.9 5.7 0.26 200/3.3 5 -3.18 7.5
0.6314 159/1.4 8 -3.4 10.2 1.14 118/0.5 11 -3.5 13.0 1.6 91/0.18 12
CRASH
Example 3
[0193] FIG. 49A illustrates an abrasive member 840 modeled for
topography removing applications. The leading edge 842 includes a
plurality of discrete features 844 separated by slots 846 that
permit air flow and particles to enter. The trailing edge 848
similarly includes a plurality of discrete features 850 separated
by slots 852. The features 844, 850 have a height 854 of about 2
micrometers and are formed with rounded leading edge surfaces to
distribute both lubricant and wear debris.
[0194] The height 854 is sufficient to create a positive pressure
profile at the top of the pads 844, 850 and a negative suction
force at the trailing side 845 of the features 844 in cases of air
as a lubricant. The proper selection of the pressure distributions
controls the pitch angle of the abrasive member 840 and the minimum
spacing above the substrate.
[0195] In the case of topography removing, the abrasive member 840
does not follow certain target wavelengths of waviness. The pitch
angle of the abrasive member 840 is therefore substantially reduced
to cause both the leading edges 842 and the trailing edges 848 to
not follow the target wavelengths of waviness and to cause wear of
the interacting surfaces.
[0196] A simple exercise demonstrates the capability of this design
given in Table 3. By varying the externally applied preloads from
about 0.1 grams to about 10 grams, a reduction in the pitch angle
and spacing is attained, causing a higher level of wear and
interactions between both the leading and trailing edges 842, 848
and the substrate. The low pitch angle also inhibits follow of the
target wavelengths.
[0197] Note that at 5 grams of preload a negative suction force and
a total positive pressure is generated to counter the contact force
of 2.56 grams and the 5 grams of preload. An increase in preload as
shown causes a substantially linear increase in contact force
responsible for the removal of material at the substrate. FIG. 49B
is a graphical illustration of the contact pressure of the abrasive
member 840 with the substrate. Note the negative pressure at the
leading edge 842.
[0198] Table 3 provides a summary of various performance parameters
for the abrasive member as a function of preload.
TABLE-US-00003 TABLE 3 Negative Positive Contact Pitch (micro-
Preload Pressure Pressure force radians)/fly (grams) (grams)
(grams) (grams) height (nm) .1 -2.33 2.43 0 31/21 1 -2.39 3.31
0.075 12/14 5 -2.4 4.91 2.56 4/4.8 7 -2.48 5.35 4.13 2.6/3.2 10
-2.50 5.97 6.53 8/1.5
Example 4
[0199] FIGS. 50A and 50B illustrate an abrasive member 870 for use
with free abrasive particles, such as in CMP. Leading edge
pressurization causes the abrasive member 870 to pitch upward so
leading edge 872 does not contact the substrate. The pitch also
contributes to the ability of the abrasive member 870 to follow the
topography of the substrate.
[0200] Rails 876 at trailing edge 874 help pressurize the bearing
and cause the trailing edge 874 to contact the substrate. Top
surfaces 878 of the rails 876 are in direct contact with the
substrate if desired. These surfaces 878 can be textured and coated
with hard coatings to cause defect removal and burnishing. The
rails 876 control the spacing between the abrasive member 870 and
the substrate and provide a predictable interference between the
trapped free abrasive particles and the substrate.
[0201] A series of shaped recessed pads 880 are fabricated at the
trailing edge 874 between the rails 876 to interact with the free
abrasive particles present in the chemical mechanical polishing
slurry. The recesses have a depth 882 of about 10 nanometers to
about 50 nanometers relative to rails 876, which is smaller than
the diameter of the free abrasive particles. The leading edges 884
of the recessed pads 880 are shaped to allow progressive entrance
of the free abrasive particles to the interface of the abrasive
member 870 with the substrate.
[0202] The design presents a leading edge 884 pressurized zone and
a trailing edge 874 pressurized zone. The trailing edge 874 is able
to both follow the topography while the recessed pads 880 cause the
free abrasive particles to be in intimate contact with the
substrate. The resulting contact pressure is substantially uniform
and independent of the substrate topography.
Example 5
[0203] FIG. 51 illustrates abrasive member 900 for use with free
abrasive particles, similar to CMP. In the case of conditions where
a hydrodynamic film is difficult to establish, such as for example
in the case of slow spinning plates and the presence of large
amount of debris interfering with the formation of a hydrodynamic
film, it is desirable to switch to a hydrostatic bearing
concept.
[0204] One or more button bearings 902, 904 are fabricated at the
leading edge 906, such as illustrated in FIGS. 39A and 39B. Pad 908
is formed at the trailing edge 910. The pad 908 includes ramp 912
that promotes movement of the free abrasive particles into the
interface with the substrate. The trailing edge 910 is in contact
with the slurry, causing the free abrasive particles to contact the
surface and remove material. The hydrostatic bearing establishes a
stable bearing and assures topography following. The hydrostatic
bearing provides a substantially constant polishing pressure across
the substrate.
[0205] Additional button bearings 914, 916 are optionally located
on the pad 908 to establish a desired spacing profile with the
substrate, including pitch, nominal spacing (minimum), and a roll
attitude of the abrasive member 900.
Example 6
[0206] FIGS. 52A and 52B illustrates an abrasive article 1150 with
an array of abrasive member 1152 with integrated preload 1154 and
gimbal structure 1156 in accordance with an embodiment of the
present invention. The illustrated abrasive members 1152 includes
spherical fluid bearing structures 1158 each with crown 1160
(curvature in the direction of travel) and camber 1162 (curvature
perpendicular to the crown) 1160. The illustrated curvature is
substantially exaggerated to illustrate the concept. The abrasive
members 1152 can be cylindrical or spherical in form.
[0207] The height differential from center 1164 of the fluid
bearing structure 1158 to the edge 1166 is preferably about 10
nanometers to about 100 nanometers to permit the fluid bearing to
form. The spherical nature of the fluid bearing surface 1158 is
desirable for interacting with free abrasive particles contained in
slurry for chemical mechanical polishing.
[0208] Each abrasive member 1152 includes a plurality of extensions
1168 that form the individual gimbal assemblies 1170. As best
illustrated in FIG. 52B, the extensions 1168 are mounted to tabs
1172 on preload pad 1174, such as for example, by an adhesive,
solvent bonding, ultrasonic welding, and the like. The extensions
1168 can flex and twist on either side of the tabs 1172 so the
abrasive members 1152 can be independently displace vertically, and
in pitch and roll. For ease of manufacturing the abrasive members
1152 and extension 1168 are molded as a unitary structure.
[0209] Preload members 1176 are positioned between the preload pad
1174 and rear surfaces 1159 of the abrasive members 1152. The
preload members 1176 are preferably resilient to permit deflection
of the abrasive members 1152 in the vertical direction. The preload
members 1176 are preferably attached to either the preload pad 1174
or the abrasive members 1152. In an alternate embodiment, the
preload pad 1174 is made of a resilient material. The preload 1184
is applied simply by pushing the entire assembly 1150 against the
substrate.
[0210] The abrasive members 1152 optionally include one or more
cavities or steps 1180 near leading edge 1182 to promote formation
of a fluid bearing. By changing the curvature of the fluid bearing
surface 1158, the shape or location of the cavities 1180, or a
variety of other variables, the abrasive members can be either
topography following or topography removing. If the curvature of
the fluid bearing surface 1158 is increased above about 100
nanometers, the maximum pressure tends to form at the center 1164.
The spherical configuration permits a progressive interaction with
free abrasives. The spherical shape also allows for a point like
contact with desirable topography following properties.
Example 7
[0211] FIGS. 53A and 53B illustrates an abrasive article 1200 with
an array of abrasive member 1202 substantially as shown in FIGS.
52A and 52B with hydrostatic ports 1204 in accordance with an
embodiment of the present invention. The hydrostatic ports 1204 are
preferably button bearings, such as disclosed in FIG. 39A, located
at leading edges 1206 of the abrasive members 1202.
[0212] Rear surfaces 1208 of each abrasive member 1202 includes
channels 1210 that fluidly communicate with opening 1212 in sealing
layer 1214. As best illustrated in FIG. 53A, the openings 1212
fluidly communicate with holes 1216 in preload members 1226. Rear
surface 1220 of preload pad 1218 includes a series of channels 1222
and backing layer 1224. As a result, a pressurized gas delivered to
the channels 1222 flows through the backing layer, to the channels
1210 in the abrasive members 1202 and out the pressure ports
1204.
[0213] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limit of that range and any other stated or intervening
value in that stated range is encompassed within the inventions.
The upper and lower limits of these smaller ranges which may
independently be included in the smaller ranges is also encompassed
within the inventions, subject to any specifically excluded limit
in the stated range. Where the stated range includes one or both of
the limits, ranges excluding either both of those included limits
are also included in the inventions.
[0214] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which these inventions belong.
Although any methods and materials similar or equivalent to those
described herein can also be used in the practice or testing of the
present inventions, the preferred methods and materials are now
described. All patents and publications mentioned herein, including
those cited in the Background of the application, are hereby
incorporated by reference to disclose and describe the methods
and/or materials in connection with which the publications are
cited.
[0215] The publications discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as an admission that
the present inventions are not entitled to antedate such
publication by virtue of prior invention. Further, the dates of
publication provided may be different from the actual publication
dates which may need to be independently confirmed.
[0216] Other embodiments of the invention are possible. Although
the description above contains much specificity, these should not
be construed as limiting the scope of the invention, but as merely
providing illustrations of some of the presently preferred
embodiments of this invention. It is also contemplated that various
combinations or sub-combinations of the specific features and
aspects of the embodiments may be made and still fall within the
scope of the inventions. It should be understood that various
features and aspects of the disclosed embodiments can be combined
with or substituted for one another in order to form varying modes
of the disclosed inventions. Thus, it is intended that the scope of
at least some of the present inventions herein disclosed should not
be limited by the particular disclosed embodiments described
above.
[0217] Thus the scope of this invention should be determined by the
appended claims and their legal equivalents. Therefore, it will be
appreciated that the scope of the present invention fully
encompasses other embodiments which may become obvious to those
skilled in the art, and that the scope of the present invention is
accordingly to be limited by nothing other than the appended
claims, in which reference to an element in the singular is not
intended to mean "one and only one" unless explicitly so stated,
but rather "one or more." All structural, chemical, and functional
equivalents to the elements of the above-described preferred
embodiment that are known to those of ordinary skill in the art are
expressly incorporated herein by reference and are intended to be
encompassed by the present claims. Moreover, it is not necessary
for a device or method to address each and every problem sought to
be solved by the present invention, for it to be encompassed by the
present claims. Furthermore, no element, component, or method step
in the present disclosure is intended to be dedicated to the public
regardless of whether the element, component, or method step is
explicitly recited in the claims.
* * * * *