U.S. patent application number 13/050517 was filed with the patent office on 2011-09-22 for composite polishing pad.
This patent application is currently assigned to BOUTAGHOU LLC. Invention is credited to Zine-Eddine Boutaghou.
Application Number | 20110230126 13/050517 |
Document ID | / |
Family ID | 44647612 |
Filed Date | 2011-09-22 |
United States Patent
Application |
20110230126 |
Kind Code |
A1 |
Boutaghou; Zine-Eddine |
September 22, 2011 |
COMPOSITE POLISHING PAD
Abstract
An abrasive article referred to as composite polishing pad (CPP)
includes a plurality of fixed abrasive elements or a plurality of
chemical mechanical polishing (CMP) pads attached to a plurality of
pressure pads suspended to flexible structures capable to follow
the wafer topography. A plurality of stems with dimpled ends act on
the pressure pads to generate desired pressure acting on the wafer.
The stems are attached to a spring arrangement capable of
substantial vertical deflection under a desired load. In one
embodiment a plurality of pressure pads suspended to a plurality of
stems by revolute joints. The stems are attached to a spring
arrangement capable of substantial vertical deflection under a
desired load. In another embodiment, a plurality of pressure pads
are attached to a plurality of stems suspended to a series of
springs capable of substantial vertical deflection under a desired
load.
Inventors: |
Boutaghou; Zine-Eddine;
(North Oaks, MN) |
Assignee: |
BOUTAGHOU LLC
North Oaks
MN
|
Family ID: |
44647612 |
Appl. No.: |
13/050517 |
Filed: |
March 17, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
61315191 |
Mar 18, 2010 |
|
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|
61315210 |
Mar 18, 2010 |
|
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61315237 |
Mar 18, 2010 |
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Current U.S.
Class: |
451/527 |
Current CPC
Class: |
B24B 37/26 20130101;
B24B 37/22 20130101; B24B 37/245 20130101 |
Class at
Publication: |
451/527 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Claims
1. A polishing pad comprising: an abrasive element; a pivoting
flexure formed around the abrasive element and attached to the
abrasive element, the abrasive element including a plurality of
abrasive particles, the pivoting flexure including a dimple to
allow pivoting of the abrasive element; (d) a stem supported by a
preload flexure, the stem positioned to apply a load through the
dimple of the pivoting flexure, (e) a plurality of pillars affixed
to a plurality of preload flexures arranged in a layer to provide
fixed boundary conditions for the edges of pivoting flexure, and
(f) an opening made in the carrier that allows for the preload
flexure to move vertically.
2. The polishing pad of claim 1, wherein the fixed abrasive
elements are in a rectangular shape.
3. The polishing pad of claim 1, wherein the fixed abrasive
elements are in a circular shape
4. A polishing pad comprising: a polishing pad, a pivoting flexure
formed around the polishing pads hold the polishing pads, the
polishing pad affixed to pivoting flexure, a stem supported by a
preload flexure, the stem applying a load through a dimple pn the
pivoting flexure, a plurality of pillars affixed to a preload
flexure layer to provide fixed boundary conditions for the edges of
pivoting flexure, and an opening made in the carrier allows for the
preload flexure to move vertically with substantially no
interference.
5. The polishing pad of claim 4, wherein the polishing pad is one
of a plurality of polishing pads arranged in a rectangular
shape.
6. The polishing pad of claim 4, wherein the polishing pad is one
of a plurality of polishing pads arranged in a circular shape.
7. A polishing comprising a) a polishing pad element, b) the
polishing pad elements are affixed to a pivoting flexure, (c) a
pivoting flexure formed around the fixed abrasive elements hold the
abrasive element, (d) a stem supported by a preload flexure to
apply a load through a dimple on the pivoting flexure, (e) a
plurality of pillars affixed to the preload flexure layer provide
fixed boundary conditions for the edges of pivoting flexure, and
(f) an opening made in the carrier allows for the preload flexure
to move vertically with substantially no interference.
8. The polishing pad of claim 7, wherein the polishing pad is one
of a plurality of polishing pads arranged in a rectangular
shape.
9. The polishing pad of claim 7, wherein the polishing pad is one
of a plurality of polishing pads arranged in a circular shape.
10. The polishing pad of claim 7, wherein the polishing pad is one
of a plurality of polishing pads arranged in a rectangular
shape.
11. The polishing pad of claim 7, wherein the polishing pad is one
of a plurality of polishing pads arranged in a circular shape.
12. The polishing pad of claim 7, wherein at least one of the
polishing pads is fabricated for chemical mechanical polishing
(CMP) applications.
13. The polishing pad of claim 7, wherein at least on of the
polishing pads contains abrasive particles.
14. A polishing pad, comprising: a plurality of flexible flexures
with flexibility in a direction transverse to the plane defined by
the polishing plane, and a plurality of polishing elements each
attached via stems to a the flexible flexures applying a desired
pressure in the transverse direction with respect to the polishing
pad in order to contact and polish the workpiece.
15. The pad of claim 17, wherein at least one of the polishing
elements has a circular cross sections.
16. The pad of claim 17, wherein at least one of the polishing
elements has a rectangular cross sections.
17. A polishing pad, comprising: a plurality of flexible flexures
with flexibility in a substantially vertical direction to the plane
defined by the polishing plane, and a plurality of pressure pads
each connected via spherical joints to the stems attached to the
pivoting flexures applying a desired pressure in a vertical
direction with respect to the polishing pad in order to contact and
polish the workpiece.
18. The polishing pad of claim 17, wherein at least one of the
polishing elements has circular cross sections.
19. The polishing pad of claim 17, wherein at least one of the
polishing elements has rectangular cross sections.
20. A polishing pad comprising: a plurality of individual polishing
pads, and at least one in-plane non straight links connecting
adjacent polishing pads.
21. The polishing pad of claim 20, wherein the polishing pads are
in a rectangular shape.
22. The polishing pad of claim 20, wherein the polishing pads are
in a circular shape.
23. The polishing pad of claim 20, wherein at least on of the
polishing pads is fabricated for CMP applications.
24. The polishing pad of claim 20, wherein at least on of the
polishing pads contains abrasive particles.
25. The polishing pad of claim 20, wherein at least on of the
polishing pads is textured and substantially covered with a
deposited film, such as diamond like carbon (DLC).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefits of the filing date of
U.S. Provisional Patent Application Ser. No. 61/315,191 filed Mar.
18, 2010, which is entitled "Composite Polishing Pad", U.S.
Provisional Patent Application Ser. No. 61/315,210 filed Mar. 18,
2010, which is entitled "Method to enhance polishing performance of
abrasive charged structured polymer substrates" and U.S.
Provisional Patent Application Ser. No. 61/315,237 filed Mar. 18,
2010, which is entitled "Method to enhance polishing performance of
abrasive charged polymer substrates" all of which are hereby
incorporated herein in their entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed to an abrasive article
including a plurality of abrasive element independently attached to
gimbal structures.
BACKGROUND OF THE INVENTION
[0003] The invention relates to modifying the rigid substrate of a
fixed abrasive article or a chemical mechanical pad used in
semiconductor wafer polishing.
[0004] Chemical mechanical polishing (CMP) processes are used n
semiconductor wafer fabrication to polish and planarize a
semiconductor wafer. CMP processes involve placing an abrasive
between a relatively stiff pad and a semi-conductor wafer and
moving the pad and the semiconductor relatively to each of the to
modify the surface of the wafer. The abrasives used in CMP process
can in the form of a slurry or fixed abrasive particles, or a fixed
abrasive element.
[0005] CMP processes attempt to remove material selectively from
high location i.e. features having dimensions on the scale of those
features commonly produced by photolithography, to planarize the
wafer surface. CMP processes also attempt to remove material
uniformly on the scale of the semiconductor wafer so that each die
on the wafer is planarized to the same degree in an equivalent
amount of time. The rate of planarization for each die is
preferably constant over the entire wafer. It is difficult to
achieve both these objective simultaneously because semiconductor
wafers are often curved and warped. Semiconductor wafers present a
topography with roughness, short and long range waviness in the
radial and circumferential directions. At the microscopic level a
semiconductor wafer is analogous to a potato ship. In addition some
of the semiconductor wafers include numerous step height variations
and protrusions, which are produced during the fabrication sequence
of an integrated circuit on a wafer. These height variations and
the wafer topography of the semiconductor wafer can interfere with
the uniformity of the polishing process such that some regions of
the wafer become over polished while other regions remain under
polished.
[0006] In modern integrated circuit fabrication, layers of material
are applied to embedded structures previously formed on
semiconductor wafers. CMP is an abrasive process used to remove
these layers and polish the surface of a wafer flat to achieve the
desired structure. CMP may be performed on both oxides and metals
and generally involves the use of chemical slurries applied via a
polishing pad that is moved relative to the wafer (e.g., the pad
may rotate circularly relative to the wafer). The resulting smooth,
flat surface is necessary to maintain the photolithographic depth
of focus for subsequent steps and to ensure that the metal
interconnects are not deformed over contour steps.
[0007] The planarization/polishing performance of a pad/slurry
combination is impacted by, among other things, the mechanical
properties and slurry distribution ability of the polishing pad.
Typically, hard (i.e., stiff) pads provide good planarization, but
are associated with poor with-in wafer non-uniformity (WIWNU) film
removal. Soft (i.e., flexible) pads, on the other hand, provide
polishing with good WIWNU, but poor planarization. In conventional
CMP systems, therefore, harder pads are often placed on top of
softer pads to improve WIWNU. Nevertheless, this approach tends to
degrade planarization performance when compared to use of a hard
pad alone.
[0008] It is therefore the case that designing CMP polishing pads
requires a trade-off between WIWNU and planarization
characteristics of the pads. This trade-off has led to the
development of polishing pads acceptable for processing dielectric
layers (such as silicon dioxide) and metals such as tungsten (which
is used for via interconnects in subtractive processing schemes).
In copper processing, however, WIWNU directly impacts
over-polishing (i.e., the time between complete removal of copper
on any one area versus complete removal from across an entire wafer
surface) and, hence, metal loss and, similarly, planarization as
expressed by metal loss. This leads to variability in the metal
remaining in the interconnect structures and impacts performance of
the integrated circuit. It is therefore necessary that both
planarity and WIWNU characteristics of a pad be optimized for best
copper process performance.
[0009] Some of the above-described concepts can be illustrated
graphically. FIG. 1 illustrates the surface of a post-CMP wafer 100
with copper interconnects 101 defined in a low-K dielectric layer
103. Stress induced cracking damage 102 is seen on the surface of
the dielectric layer 103, as a result of using a conventional
polishing pad. Dishing and erosion increase with over-polishing,
hence there is a need to minimize over-polishing of copper
wafers.
[0010] CMP processes that employ slurry have been modified in an
effort to overcome the problem of non-uniform polishing as
summarized above. As proposed by Goetz (2008) a composite polishing
pad that includes a first elastic material carrying fixed abrasive
tiles. The elastic side of the first elastic layer is attached to a
second stiff layer. Fixed abrasive polishing do not rely on the
transport of loose abrasive particles over the surface of the pad
to effect polishing. The abrasive tiles include abrasive particles
disposed in a binder and bonded to the backing, which forms a
relatively high modulus fixed abrasive element. The proposed
approach by Goetz suffers from a lack of ability to follow the
topography of the semiconductor wafer to cause uniform cutting
pressure during the polishing process.
[0011] Pressure sensing elements 300 are also connected to a
pressure control mechanism to effect an appropriate pressure
profile during polishing is shown in FIG. 3 by Baraj et al. (2009).
Monitoring the pressures detected by the pressure sensing elements
301 and comparing that information to an established pressure model
apply a predetermined pressure profile. Differences between the
actual pressures and the pressure model may then be used to alter
the polishing operations to affect the desired pressure profile.
This approach is effective for long range waviness. The size of the
sensing device is substantially larger than the die size leading to
an average pressure detection not an instantaneous pressure
detection as required to compensate for dishing and over polishing
for small wafer features. In addition short range wavelength
pressure fluctuations cannot be readily detected.
SUMMARY OF THE INVENTION
[0012] The proposed solution suspends each polishing element to
comply with the semiconductor topography in a planar fashion while
applying a desired load and pressure independently of the location
on the wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates the surface of a post-CMP wafer.
[0014] FIG. 2 is a cross section view of a wafer is a schematic
cross sectional view of a portion of an abrasive article reported
in prior art.
[0015] FIG. 3 is a cross section view of a wafer is a schematic
cross sectional view of a portion of an abrasive article reported
in prior art.
[0016] FIG. 4 is a cross section view of an example embodiment of
the present invention.
[0017] FIG. 5 is an exploded view a single component forming the
composite universal polishing pad (CPP), according to an example
embodiment.
[0018] FIG. 6 gives a view of an assembled CPP, according to an
example embodiment.
[0019] FIG. 7 gives an exploded view of the layers forming a CPP,
according to an example embodiment.
[0020] FIG. 8 gives a close up view of the preload structure and
the gimaballing structure where a polishing pad attached, according
to an example embodiment.
[0021] FIG. 9 gives a close up view of the out of plane
(curvilinear) springs forming the gimbal structure, according to an
example embodiment.
[0022] FIG. 10 gives a close up of the preload structure with the
preload stem supported by a series of out of plane springs,
according to an example embodiment.
[0023] FIG. 11 gives a concept of using a continuous polishing pad,
according to an example embodiment.
[0024] FIG. 12 gives a view a single component forming a CPP with a
continuous polishing pad, according to an example embodiment.
[0025] FIG. 13 gives a view of a single component forming a CPP
with a continuous polishing pad, according to an example
embodiment.
[0026] FIG. 14 gives an exploded view of a single component forming
a CPP with a continuous polishing pad, according to an example
embodiment.
[0027] FIG. 15 gives a cross section of a CPP with preload stems
with a polishing pad attached to the end of the preload stems,
according to an example embodiment.
[0028] FIG. 16 gives a 3-d view of the load layer with each stem
connected to a preload spring, according to an example
embodiment.
[0029] FIG. 17 gives a close up view of the preload stems supported
by a series of springs to cause deflection under an externally
applied load onto the carrier pad, according to an example
embodiment.
[0030] FIG. 18 shows a polishing pad (with or without abrasives)
attached to the stem ends spring loaded and attached to a carrier
pad, according to an example embodiment.
[0031] FIG. 19 gives an exploded view polishing pad (with or
without abrasives) attached to the stem ends spring loaded and
attached to a carrier pad, according to an example embodiment.
[0032] FIG. 20 gives a cross section of a CPP concept with
individual pads or abrasives attached to the ends of load stems,
according to an example embodiment.
[0033] FIG. 21 gives a close up view of the preload stems
supporting polishing pads or abrasive elements, according to an
example embodiment.
[0034] FIG. 22 gives a cross section of a CPP concept with
individual polishing pads or abrasive elements supported by a
revolute or cylindrical joint, according to an example
embodiment.
[0035] FIG. 23 gives a cross section of a CPP concept with
polishing pads supported by a revolute or cylindrical joint,
according to an example embodiment.
[0036] FIG. 24 gives a close up view of the preload stems with an
end revolute joint connected to a supporting pad, according to an
example embodiment.
[0037] FIG. 25 gives a polishing pad arrangement with individual
pad connected though a non-straight link, according to an example
embodiment.
[0038] FIG. 26 gives an exploded view of the polishing pad
arrangement shown in FIG. 25, according to an example
embodiment.
DETAILED DESCRIPTION
[0039] Described herein is a pad suitable in a variety of CMP
processes. A plurality of independently suspended polishing pads
401 are assembled into a polishing article 400 referred to as
composite polishing pad (CPP). Each polishing pad is suspended to a
pressure pad 402 attached to a flexure 403 and subject to a
substantially constant preload. The preload is applied through a
stem end 406 referred to as dimple acting on the opposite side of
the flexure suspending the polishing pad. Each polishing pad
applies a substantially constant pressure via the stem
independently of its location on the semiconductor wafer. The
suspended polishing pad follows the contour of the semiconductor
wafer regardless of the waviness of the semiconductor wafer. The
preload apparatus is formed of a stem 406 attached to a spring
mechanism 407 allowing substantially constant load as a function of
vertical displacement. The ability of each polishing pad to comply
in the plane of the wafer and follow the wafer runnout causes
substantially uniform material removal.
[0040] In one embodiment, a series of independent pressure pads 602
attached to independent stems 603 supported by preload flexures. In
turn the polishing pads attached to the pressure allowing
substantially constant load as a function of vertical displacement
during polishing. The ability of each pressure pad to comply
vertically with respect to plane of the wafer assures a constant
pressure at each pressure pad 602.
[0041] In one embodiment, a series of independent pressure pads 802
attached via a spherical joints 803 to independent stems 804
supported to preload spring flexures 805. The flexures 805 deflect
under a normal load to the pressure pads. In turn the polishing
pads attached to the pressure pad allow substantially constant load
as a function of vertical displacement during polishing. The
ability of each polishing pad to comply in the vertical direction
of the wafer and in the plane of wafer assures a constant pressure
at each pressure pad independently of the wafer waviness and
runnout.
[0042] In one embodiment of the present invention, the pressure
applied by each polishing is made variable from inner diameter to
outer diameter to cause uniform material removal throughout the
semiconductor wafer as the travel contact length of each polishing
pad is not constant from inner diameter to outer diameter. For
example, the outer polishing pads can be envisioned to have a
larger preload to apply a larger pressure in order to remove more
material. The polishing pad may also include polishing fluid or
slurry distribution layer.
[0043] The present invention recognizes the importance of tailored
polishing pressure to maintain a uniform polishing action. Fragile
low-K materials can be easily damaged by high stresses resulting
from polishing operations. Nucleation of failure sites can occur at
local high-pressure spots. A constant pressure pad configured
according to the present invention provides the necessary
information to develop polishing processes which do not exceed
critical stress levels during processing operations. Designing the
preload spring to yield a constant preload is a strategy to achieve
uniform pressure to maintain a uniform polishing action.
[0044] In some embodiments of the present invention, the polishing
pad may be configured to apply a higher pressure at a specific
location or a variable pressure at various radii of the
semiconductor wafer. For example, the polishing pads can be made of
various materials such as polyurethane, polyester, polycarbonate,
delrin, etc. In varying embodiments of the present invention,
polishing elements are made of any suitable material such as
polymer, metal, ceramic or combination thereof and capable of
movement in the vertical axis and complying to the semiconductor
wafer topography. Alternatively, or in addition, the polishing
elements may be made in composite structures where a core is made
of one material and the shell is made of another material (e.g.,
one of which is transparent or conductive). For example, a
polishing element may contain a core made of a conductive material
such as graphite or conductive polymer.
[0045] Pressure control during polishing is critical especially for
nanometer feature sizes. Table 1 shows the decrease in required
pressure as a function of material type and die feature size.
[0046] FIG. 4 depicts a cross section of one embodiment of the
present invention. A first adhesive layer 408 is applied to a
backing element 409 supporting a preload flexure consisting of a
stem protruding from the base 411 and in contact with a pivoting
flexure supporting the polishing pad 403. An adhesive layer 404
holds the preload 411 and dimple structure 406 attached to the
backing layer 409. An opening is made in the backing layer beneath
the preload fixture to allow for the deformation of the preload
flexure 411 without interference during the pressure generation
during the polishing process. A series of protruding pillars 405
provide a fixed boundary condition supporting the outer edges of
the pivoting flexure. Finally the abrasives 401 are attached to the
pressure pads 402.
[0047] FIG. 5 is an exploded view of a single polishing pad
assembly 420 contained in the CPP concept. A backing layer 409 with
an opening 414 with an opening is assembled via an adhesive layer
408 to a preload flexure 407. The preload fixture has a preload
stem 406 attached to a preload flexure design 407 capable of
imparting a substantially constant preload for example. A series of
protruding pillars 405 provide support to the pivoting flexures 403
supporting the pressure pads 401. The embodiment disclosed allows
for the pressure pads 401 to follow the semiconductor wafer
topography while allowing a locally stiff pad capable of
planarazing the wafer.
[0048] FIG. 6 shows a series of individually suspended and
preloaded polishing elements 401 assembled in a polishing pad
referred to as CPP. A backing element 409 supports the preload
flexure 411 applying a substantially constant load if desired. It
is therefore the case that the proposed polishing pad design does
not require a trade-off between WIWNU and planarization
characteristics of the pads. This lack of required trade-off has
led to the development of polishing pads (CPP) acceptable for
processing dielectric layers (such as silicon dioxide) and metals
such as tungsten (which is used for via interconnects in
subtractive processing schemes). Avoiding over polishing in copper
processing is achieved by CPP.
[0049] An exploded view is offered in FIG. 7 shows the various
components involved in fabricating a composite universal polishing
pad (CPP). It is foreseen that the backing layer 409 is attached to
the preload flexure layer 411, followed by the attachment of the
pivoting flexure layer 403 and finally the polishing pads 401 (CMP
pads or abrasive pads) are finally added as the last step of the
process.
[0050] A close up view in FIG. 8 offers a view of the assembly of
each independent polishing structure 401. Note that the preload
stem 406 is pressed against the pivoting flexure 407 allowing the
polishing pad to move in the vertical direction while complying to
the semiconductor wafer. Such strategy allows for the use of a hard
polishing pad while providing compliance at the interface of the
semiconductor wafer. This strategy of decoupling the pad
characteristics from its ability to comply at the semiconductor
interface leads to removing the traditional trade-off between WIWNU
and planarization characteristics of the pads.
[0051] Detailed view of the pivoting flexure is provided in FIG. 9
includes a series of curvilinear springs 407 organized to allow
compliant motion with respect to the semiconductor wafer of the
attached polishing pad or polishing abrasive element 401. The
springs 407 have a curvilinear shape designed to allow for out of
plane motion while allowing for substantial pivoting to follow the
plane defined by the semi-conductor wafer; note that straight
springs do not flex out of plane causing tensile stresses in the
spring beams and are inadequate. The spring members must allow for
compliance out of plane under a normal load. Various examples of
spring members can be listed such as L-shaped and Z-shaped.
[0052] The preload flexure layer is shown in details in FIG. 10.
The preload stem 406 shows a spherical end to allow a dimple 413
like contact with the pivoting structure. A preload flexure 407
deforms under a preload applied by the stem 406. A series of
protruding pillars provide 405 support to the ends of the pivoting
flexure not shown herein. The preload stem can have many
embodiments such as flat top, spherical and cylindrical
structures.
[0053] FIG. 11 gives a cross section of a CPP concept with a
continuous flexible polishing pad 501 attached to the contact pads
502 of each pivoting flexure 503. Upon bringing the CPP in contact
with wafer a preload is generated from the preload flexure 507 to
the contacting pads 503 by deflecting the supporting springs 507.
The dimple end of the stems 515 contacts the back end of the
pivoting flexure 503. The preload flexure 508 applies a constant
load onto the contact pads 502.
[0054] FIG. 12 gives an exploded view of a polishing pad assembly
contained in the CPP. A backing plate 509 is assembled via an
adhesive layer 508 to a preload flexure 507. The preload fixture
has a preload stem attached to a spring flexure design capable of
imparting a substantially constant preload for example. A series of
protruding pillars provide support to the pivoting flexures. A
final layer of continuous polishing pad 501 is assembled to the
individual contacting pads 502 to provide constant preload at each
contacting pad during the polishing process. The embodiment
disclosed allows the continuous polishing pad to follow the
semiconductor wafer topography while allowing a locally stiff pad
capable of planarazing the wafer.
[0055] The preload flexure layer is shown in details in FIG. 13.
The preload stem shows dimple structure like in contact with the
gimballing structure. A preload flexure deforms under a preload
applied by the contacting pad 502 contacting the polishing pad 501.
A series of protruding pillars provide supports to the ends of the
pivoting springs 503. The preload stem can have many embodiments
such as flat top, spherical and cylindrical shapes. The contact pad
presses against the continuous polishing pad to provide a
substantially uniform pressure.
[0056] FIG. 14 gives an exploded view of the assembly shown in FIG.
13. A polishing pad 501 is in direct contact with a pressure pad
502 supported by a pivoting flexure 504. The pivoting flexure 504
is preloaded via the dimple 503 attached to the spring loaded stem
503.
[0057] FIG. 15 gives a cross section of a CPP concept with a
continuous polishing pad 601 at the end of the contacting pads 602.
Upon bringing the CPP in contact with wafer a preload is applied to
the polishing pad 601 by deflecting the supporting springs 604. The
preload springs apply a constant load onto the polishing pad
601.
[0058] FIG. 16 shows a series of pressure pads 602 organized to
form a circular pad 605. Each pressure pad 602 is attached to
spring structure 604 allowing for compliance in the vertical
direction. The preload fixture 604 has a preload stem attached to a
spring flexure design capable of imparting a substantially constant
preload for example. The embodiment disclosed allows the continuous
polishing pad to apply a substantially constant load on the
semiconductor wafer while allowing a locally stiff pad capable of
planarazing the wafer.
[0059] The preload flexure layer 605 is shown in details in FIG.
17. The end of the preload stem 603 holds a pressure pad 602. A
preload flexure 604 deforms under a load applied by the pressure
pads 602. The pressure pad pushes against the continuous polishing
pad to provide a substantially uniform pressure.
[0060] FIG. 19 gives an exploded view of the assembly shown in FIG.
18. A polishing pad 601 is in direct contact with a multitude of
pressure pads 602 supported by a backing layer 605.
[0061] FIG. 20 gives a cross section of a polishing pad with a
series of independent flexible pressure pads 703 at the end of the
load stems 705. The end of each pressure pad 702 is equipped with
abrasive pads 701 or a polishing pads 701. Each individual
polishing pad or abrasive pad deflects under an externally applied
load to provide a substantially constant pressure upon contact with
the wafer. The preload springs 703 apply a constant load onto the
polishing pad.
[0062] FIG. 21 shows a series of pressure pads 702 organized to
form a circular pad 700. Each pressure pad 702 is attached to
spring structure 703 allowing for compliance in the vertical
direction with respect to the wafer. The preload fixture 703 is
equipped with a preload stem 705 attached to a spring flexure
design 703 capable of imparting a substantially constant preload
for example. The embodiment disclosed allows the continuous
polishing pad to apply a substantially constant load on the
semiconductor wafer while allowing a locally stiff pad capable of
planarazing the wafer.
[0063] FIG. 22 shows a concept of a polishing pad 800 where the
pressure pad 802 is suspended by a revolute joint 803 to the load
stem 804. The load stem 804 is supported by a series of springs 805
design to deflect under a normal load. The pressure pad 804 is
equipped with an abrasive or polishing pad 801. The configuration
shown herein allows for the polishing pad or abrasive pad to follow
the wafer topography with 3 dimensional rotational freedoms. The
rotary joint allows the polishing pad to pivot with respect to the
wafer.
[0064] FIG. 23 shows a concept where the pressure pad is suspended
by a revolute joint to the load stem. The load stem is supported by
a series of springs design to deflect under a normal load. The
pressure pads support a continuous polishing pad. The configuration
shown herein allows for the polishing pad to follow the wafer
topography with 3 dimensional rotational freedoms at each pressure
pad.
[0065] FIG. 24 gives a detailed view of a single pressure pad 802.
A revolute joint 803 between the load stem 804 and the pressure pad
802 supports the pressure pad. The load stem is supported by a
series of vertically compliant springs 805 allowing the pressure
pad 802 to freely pivot with respect to the surface of the wafer
while keeping the ability to follow the runnout produced by the
wafer.
[0066] FIG. 25 gives a detailed view of a polishing pad 900 used in
conjunction with the present invention. The polishing pad assembly
910 is fabricated via an S-shaped link 920 to each others. The
S-shaped links are arranged to connect each polishing pad with
minimal out of plane resistance and contributes to decoupling the
motion of each polishing pad from each other. Cross talk between
polishing pads is minimized for example if polishing pad 910 is
deflected in the z plane perpendicular to the polishing pad
assembly 910, the displacement experienced by the surrounding pads
911, 912, 913, and 914 will be minimum. FIG. 26 gives a detailed
view of a polishing pad 900 used in conjunction with the present
invention showing the S-structure of the links and the polishing
pads. The S-shape feature 920 has a low bending stiffness due to S
shape allowing minimum cross talk between the pads when subjected
to an in-plane or out of plane deflection. Non-straight shaped
links such as Z, L, etc. can be arranged to further reduce the
bending moment. In contrast, a straight connector generates tension
on the adjacent polishing pads during a vertical or in-plane
motion. Displacement due to in plane stretching of a straight
connector requires very large forces to be produced thus limiting
the amount of vertical displacement or in-plane displacement
achieved by traditional configurations as shown in continuous
polishing pad (601). So instead of fabricating a continuous
polishing pad a discontinuous sheet with S shape connector
attaching adjacent independent pads is desirable for ease of
assembly and for providing a low coupling between individual
polishing pads. Such pad can be used to accept CMP polishing pads,
abrasive charged polishing pads, etc.
[0067] Useful adhesives include, e.g., pressure sensitive
adhesives, hot melt adhesives and glue. Suitable pressure sensitive
adhesives include a wide variety of pressure sensitive adhesives
including, e.g., natural rubber-based adhesives, (meth)acrylate
polymers and copolymers, AB or ABA block copolymers of
thermoplastic rubbers, e.g., styrene/butadiene or styrene/isoprene
block copolymers available under the trade designation KRATON
(Shell Chemical Co., Houston, Tex.) or polyolefins. Suitable hot
melt adhesives include, e.g., polyester, ethylene vinyl acetate
(EVA), polyamides, epoxies, and combinations thereof. The adhesive
preferably has sufficient cohesive strength and peel resistance to
maintain the components of the fixed abrasive article in fixed
relation to each other during use and is resistant to chemical
degradation under conditions of use.
[0068] Examples of useful commercially available backing, materials
include poly(ethylene-co-vinyl acetate) foams available under the
trade designations 3M SCOTCH brand CUSHIONMOUNT Plate Mounting Tape
949 double-coated high density elastomeric foam tape (Minnesota
Mining and Manufacturing Company, St. Paul, Minn.), EO EVA foam
(Voltek, Lawrence, Mass.), EMR 1025 polyethylene foam (Sentinel
Products, Hyannis, N.J.), HD200 polyurethane foam (Illbruck, Inc.
Minneapolis, Minn.), MC8000 and MC8000EVA foams (Sentinel
Products), SUBA IV Impregnated Nonwoven (Rodel, Inc., Newark,
Del.).
[0069] Thus, an improved fixed abrasive or CMP polishing pad and
process for polishing semiconductor wafers and structures layered
thereon has been described. Although the present polishing pad and
processes for using it have been discussed with reference to
certain illustrated examples, it should be remembered that the
scope of the present invention should not be limited by such
examples.
[0070] In one aspect, the invention features an abrasive article
including a) a fixed abrasive element including a plurality of
abrasive particles, b) the fixed abrasives are affixed to a
gimballing flexure, (c) a gimbal structure formed around the fixed
abrasive elements hold the abrasive element, (d) a stem supported
by a preload flexures applies a load through a dimple to back of
the gimballing flexure, (e) a plurality of pillars affixed to the
preload flexure layer provide fixed boundary conditions for the
edges of gimbal flexure, and (f) an opening made in the carrier
allows for the preload flexure to move vertically with no
interference.
[0071] In some embodiment, the invention features an abrasive
article including (a) a fixed abrasive element including a
plurality of abrasive particles, (b) the fixed abrasives are
affixed to a pressure pad, and (c) a stem supported by a preload
flexure applies a load to the pressure pad under normal
deflection.
[0072] In some embodiment, the invention features an abrasive
article including (a) a polishing pad, (b) the polishing pad is
affixed to a pressure pad, and (c) a stem supported by a preload
flexure applies a load to the pressure pad under normal
deflection.
[0073] In some embodiment, the invention features an abrasive
article including (a) a fixed abrasive element including a
plurality of abrasive particles, (b) the fixed abrasives are
affixed to a pressure pad, (c) the pressure pads are supported by a
revolute joint to (d) a stem supported by a preload flexure applies
a load to the pressure pad under normal deflection.
[0074] In some embodiment, the invention features a polishing pad
(a) a polishing pad, (b) the polishing pad is supported by a
spherical joint to (c) a stem supported by a preload flexure
applies a load to the pressure pad under normal deflection.
[0075] In some embodiments polishing pads replace the abrasive
articles. The pads interact with slurries to provide a CMP
operation as described previously. The pad geometry is typically
flat of shaped to enhance interaction with the slurry.
[0076] In other embodiments fluid bearing structures are formed on
the fixed abrasive structures or the soft pad structures to allow
for a lift between the lubricant present during polishing and the
semiconductor wafer. Such fluid bearing forms during the relative
motion of the composite polishing pad and the semiconductor wafer
due to the shearing of the lubricant.
[0077] In other embodiments the gimbal flexure allows the fixed
abrasive element of the pads to follow the semiconductor wafer
topography and exerts a uniform pressure. The gimbal flexure is
fabricated from a polymer or stainless steel material. The gimbal
structure allows uniform planar stiffness of the abrasive element
or the pads to enable following the contour of the semiconductor
wafer.
[0078] In other embodiments the preload stem dimple structure
applies a given preload onto each abrasive element or pad. The
geometry of the load dimple structure is designed such that the end
of the load dimple structure is spherical and allows for contact
against resilient element.
[0079] 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 described the methods
and/or materials in connection with which the publications are
cited.
[0080] 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.
[0081] 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.
[0082] 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 ought 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.
* * * * *