U.S. patent application number 11/582711 was filed with the patent office on 2007-04-19 for apertured conditioning brush for chemical mechanical planarization systems.
This patent application is currently assigned to TBW Industries, Inc.. Invention is credited to Stephen J. Benner.
Application Number | 20070087672 11/582711 |
Document ID | / |
Family ID | 37948719 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070087672 |
Kind Code |
A1 |
Benner; Stephen J. |
April 19, 2007 |
Apertured conditioning brush for chemical mechanical planarization
systems
Abstract
An apparatus for conditioning the polishing pad of a chemical
mechanical planarization (CMP) system including an apertured
conditioning disk that is formed to support a plurality of brush
bristles in any desired configuration. The bristles are utilized to
lift out debris and contaminants that have been lodged within the
deep pores of polishing pads, particularly "soft" polishing pads
(or polishing felts) that include relatively deep pores. The
apertures in the conditioning disk are used to allow for the
efficient evacuation of the effluent created during the
conditioning process. The apertures may also be used to introduce
conditioning fluids as the bristles are brushing the surface to
assist in the conditioning process. The utilization of the
apertures to evacuate the effluent (via an attached vacuum source)
overcomes problems associated with the prior art by immediately
removing the dislodged material from the pad surface before it has
an opportunity to be re-incorporated into the polishing pad.
Inventors: |
Benner; Stephen J.;
(Lansdale, PA) |
Correspondence
Address: |
Wendy W. Koba
PO. Box 556
Springtown
PA
18081
US
|
Assignee: |
TBW Industries, Inc.
|
Family ID: |
37948719 |
Appl. No.: |
11/582711 |
Filed: |
October 18, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60728126 |
Oct 19, 2005 |
|
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Current U.S.
Class: |
451/56 ; 451/285;
451/443 |
Current CPC
Class: |
B24B 53/017 20130101;
B24D 13/145 20130101; B24B 53/12 20130101; B24B 57/00 20130101 |
Class at
Publication: |
451/056 ;
451/285; 451/443 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24B 29/00 20060101 B24B029/00; B24B 21/18 20060101
B24B021/18 |
Claims
1. An apparatus for conditioning a polishing pad utilized in a
chemical mechanical planarization (CMP) system, the apparatus
comprising a conditioner head housing including an inlet port for
introducing conditioning fluids onto the polishing pad and an
outlet port for evacuating conditioning effluent from a conditioned
area of said polishing pad; and a conditioning disk disposed within
the housing so as to contact a top major surface of the polishing
pad surface during conditioning, the conditioning disk comprising a
brush for sweeping the top major surface of the polishing pad and
dislodging debris therefrom, and a plurality of apertures for
dispensing conditioning fluids to, and evacuating conditioning
effluent from, the polishing pad.
2. An apparatus as defined in claim 1 wherein the brush comprises a
plurality of bristles.
3. An apparatus as defined in claim 1 wherein the conditioning disk
comprises an abrasive material.
4. An apparatus as defined in claim 2 wherein the plurality of
bristles comprises an inert material.
5. An apparatus as defined in claim 4 wherein the inert material
comprises nylon.
6. An apparatus as defined in claim 2 wherein the plurality of
bristles comprises a composite abrasive-filled material.
7. An apparatus as defined in claim 2 wherein the plurality of
bristles is disposed in a series of nested V-patterns across the
conditioning disk, with the apertures disposed therebetween.
8. An apparatus as defined in claim 2 wherein the plurality of
bristles is disposed in a series of concentric circles across the
conditioning disk.
9. An apparatus as defined in claim 2 wherein the plurality of
bristles is disposed in a plurality of spiral arms emanating from a
central region of the conditioning disk.
10. An apparatus as defined in claim 2 wherein the plurality of
bristles stand off a predetermined distance below the conditioner
head housing so as to allow for the bristles to enter the polishing
pad material without interrupting the evacuation of effluent
therefrom.
11. An apparatus as defined in claim 1 wherein the conditioning
disk further comprises a hex key alignment structure for providing
aligned attachment between the conditioning disk and the
conditioner head housing, providing alignment between the plurality
of apertures of said conditioning disk and the inlet and outlet
ports of said conditioner head housing.
12. A conditioning disk for use in dressing a polishing pad within
a chemical mechanical planarization (CMP) apparatus, the
conditioning disk comprising a plurality of apertures for
dispensing conditioning fluids to, and evacuating conditioning
effluent from, the polishing pad surface; and a brush for sweeping
across the fibrous polishing pad and dislodging debris
therefrom.
13. A conditioning disk as defined in claim 12 wherein the brush
comprises a plurality of bristles.
14. A conditioning disk as defined in claim 12 wherein the disk
comprises an abrasive material suitable for dressing the polishing
pad.
15. A conditioning disk as defined in claim 13 wherein the
plurality of bristles comprises an inert material.
16. A conditioning disk as defined in claim 15 where the inert
material comprises nylon.
17. A conditioning disk as defined in claim 13 wherein the
plurality of bristles comprises a composite abrasive-filled
material.
18. A conditioning disk as defined in claim 13 wherein the
plurality of bristles is disposed in a series of nested V-patterns
across the conditioning disk, with the plurality of apertures
disposed therebetween.
19. A conditioning disk as defined in claim 13 wherein the
plurality of bristles is disposed in a series of concentric circles
across the conditioning disk.
20. A conditioning disk as defined in claim 13 wherein the
plurality of bristles is disposed in a plurality of spiral arms
emanating from a central region of the conditioning disk.
21. A method of conditioning a polishing pad utilized in a chemical
mechanical planarization system, the method comprising the steps
of: presenting an apertured conditioning brush against a top major
surface of the polishing pad, the apertured conditioning brush
comprising a plurality of bristles and a plurality of apertures;
providing a downforce on the apertured conditioning brush
sufficient to push the plurality of bristles into the pores of the
polishing pad; moving said apertured conditioning brush across the
surface of said polishing pad such that the plurality of bristles
dislodge accumulated debris from the pores; and applying a vacuum
force sufficient to evacuate the dislodged accumulated debris
through the plurality of apertures and away from the chemical
mechanical planarization system.
22. The method as defined in claim 21 wherein the method further
comprises the step of dispensing processing fluids onto the surface
of the polishing pad as the apertured conditioning brush is moved
across the surface of the polishing pad.
23. The method as defined in claim 21 wherein the applied downforce
and the vacuum force are controlled so as to allow for the
plurality of bristles to engage the pores of the polishing pad
without interrupting the vacuum-controlled evacuation of the
dislodged debris therefrom.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/728,126, filed Oct. 19, 2005 and herein
incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a conditioning brush for
use in cleaning the polishing pad of a chemical mechanical
planarization (CMP) apparatus and, more particularly, to a
conditioning brush formed as disk to include an arrangement of both
bristles and apertures to facilitate the cleaning operation.
BACKGROUND OF THE INVENTION
[0003] In the field of chemical mechanical planarization (CMP), a
process known as "pad conditioning" or "pad dressing" is used to
restore the surface of the polishing pad and remove surface glazing
by dislodging particulates and spent polishing slurry from the pad.
Pad conditioning may be performed "ex-situ" (i.e., conditioning the
polishing pad between wafer polishing cycles) or "in-situ" (i.e.,
concurrent with, or during, a wafer polishing cycle). In a typical
prior art "in-situ" pad conditioning process, a fixed abrasive
conditioning disk is moved across the pad surface to remove a small
amount of pad material and debris, thus creating new asperities in
the pad surface to allow for the free flow of the polishing slurry.
The removed pad material and debris then combine with the slurry
dispensed during the polishing process and are passively carried
away from the pad.
[0004] Particulate generation is an on-going problem with known
processes of conditioning CMP polishing pads, where particles from
any one of the CMP apparatus, slurry, wafer, pad or conditioner
remain on the pad's surface after conditioning. Any individual
particle remaining on the pad may later scratch a wafer surface
during polishing, creating a potential defect or contributing to
polishing non-uniformity. For example, a particle disposed on the
polishing pad may create a high spot that locally concentrates the
forces between the polishing pad and the wafer. If large numbers of
particles are present on the polishing pad, local disparities in
polishing rates may result in polishing non-uniformities.
[0005] In certain types of CMP, for example tungsten CMP or
post-planarization buffing, a relatively porous polishing pad is
utilized, where this type of pad is characterized by a
microstructure exhibiting vertically oriented, open pores.
Variously referred to as a "soft" polishing pad, fibrous polishing
pad, and the like, such pads may consist of a poromeric coating
over a felt substrate, the poromeric coating comprising vertically
oriented large pores sitting on top of a smaller, microporous felt
layer. The polishing slurry and debris that settles within the
lower regions of the pores within these pads can become nearly
stagnant and develop recirculating eddy flows that trap even more
material and limit the polishing/buffing capabilities of the pad.
Over time, the trapped/recirculated materials can resurface and
damage the wafer, dilute the process materials, or both. The
conventional diamond abrasive conditioning disk is not effective in
removing this deeply-trapped material, and has the additional
drawback of quickly wearing away the porous pad material. As an
alternative, a conditioning "brush" may be used to scour the porous
pad surface in a manner that is likely to dislodge deeply embedded
particles and move them into the waste stream. Prior art CMP
systems utilizing a conditioning brush, however, require a large
amount of slurry and rinse waters in an attempt to displace these
particulates.
[0006] U.S. Pat. NO. 6,386,963 issued to S. Kenji et al. on May 14,
2002 discloses a conditioning element that is formed to support a
combination of an abrasive surface and brush bristles. In the Kenji
et al. structure, abrasive conditioning material is formed on a
ring-shaped plate that is attached to the bottom surface of the
conditioner head, leaving the center region of the element open. A
plurality of brush bristles is formed on a small disk that is then
attached to the center region of the abrasive ring. One problem
with this particular arrangement, however, is that the limited
positioning of the bristles in the central region of the
conditioning element allows some particulate matter to be
unaffected by the bristles and thus remain embedded within the pad.
Further, the differential in height between the abrasive material
and the bristles will likely result in inconsistent conditioning
behavior and wear rates for the pad material.
[0007] Another prior art arrangement is disclosed in U.S. Pat. No.
7,033,253, issued to F. L. Dunn on Apr. 25, 2006. In the Dunn
arrangement, brush bristles are disposed in any desired pattern on
the bottom surface of a conditioning element, with the remaining
portion of the surface covered by an abrasive material. The
relative hardness of the bristles and the abrasive material may be
controlled to best condition a particular pad material.
[0008] While both the Dunn and Kenji et al. arrangements provide an
improvement in implementing a conditioning brush within a
conventional CMP conditioning element, problems remain in that the
material dislodged by the bristles (and the abrasive material) may
be re-introduced to the pad surface before the conditioning process
has an opportunity to flush the debris away.
[0009] Thus, a need remains in the art for a conditioning
arrangement that provides the brushing motion preferred for large
pore, fibrous or soft polishing pads/felts, while efficiently
removing the debris from the polishing pad surface.
SUMMARY OF THE INVENTION
[0010] The need remaining in the prior art is addressed by the
present invention, which relates to a conditioning brush for use in
cleaning the polishing pad of a chemical mechanical planarization
(CMP) apparatus and, more particularly, to a conditioning brush
formed as a disk to include an arrangement of both bristles and
apertures to facilitate the cleaning operation.
[0011] In accordance with the present invention, an apertured
conditioning disk is formed to support a plurality of brush
bristles in any desired configuration. The apertures in the
conditioning disk are used to allow for the efficient evacuation of
the effluent created during the conditioning process, including
both the debris dislodged by the bristles and slurry material
remaining in the pores. The apertures may also be used to introduce
conditioning fluids to assist in the conditioning process. The
utilization of the apertures to evacuate the effluent (via an
attached vacuum source) overcomes problems associated with the
prior art by immediately removing the dislodged and/or accumulated
material from the pad surface before it has an opportunity to be
re-incorporated into the polishing pad.
[0012] In one embodiment of the present invention, the conditioning
disk is formed of a stiff material capable of supporting the
bristles in position such that the bristles have a slight stand-off
from the bottom surface of the disk, allowing for the conditioner
head to maintain a vacuum seal while the bristles engage the pores
of the pad material. In an alternative embodiment, the conditioning
disk may be formed of an abrasive material to permit simultaneous
abrading and brushing of the polishing pad surface. In yet another
embodiment, the bristles themselves may be formed of an
abrasive-filled composite material.
[0013] Other and further embodiments and aspects of the present
invention will become apparent during the course of the following
discussion and by reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Referring now to the drawings,
[0015] FIG. 1 illustrates an exemplary CMP system including a
conditioning brush formed in accordance with the present
invention;
[0016] FIG. 2 is a top view of system of FIG. 1;
[0017] FIG. 3 is a top view of an exemplary conditioner
head/conditioning brush formed in accordance with the present
invention, include a plurality of bristles and a separate plurality
of apertures within the brush;
[0018] FIG. 4 is a cut-away side view of the conditioning brush of
FIG. 3;
[0019] FIG. 5 is a simplified view of the arrangement of FIG. 4,
illustrating in particular the intrusion of the bristles within the
pores of the polishing pad;
[0020] FIG. 6 is a top view of an alternative embodiment of the
present invention, with the bristles disposed in V patterns and the
apertures disposed therebetween, the view of FIG. 6 illustrating
the placement of only a few bristles;
[0021] FIG. 7 is a top view of the same embodiment as FIG. 6, in
this case with a complete set of bristles in place; and
[0022] FIG. 8 is a top view of yet another embodiment of a
conditioning brush formed in accordance with the present invention,
in this case, the bristles and apertures disposed as a plurality of
arms configured in a spiral pattern from the center.
DETAILED DESCRIPTION
[0023] FIG. 1 contains a perspective view of an exemplary CMP
system 10 formed in accordance with the present invention for
brushing the surface of a polishing pad used to polish/planarize
surface S of a semiconductor wafer 12. In operation, surface S of
wafer 12 is positioned against a polishing pad 14 through an
arrangement not shown (and not relevant to the subject matter of
the present invention). Wafer 12 is rotated on polishing pad 14, as
shown by the arrow in FIG. 1. Polishing pad 14 itself is secured to
a rotating, orbital or linear platen 16. A stream of polishing
slurry, generally containing an oxidizer, abrasive and/or ultrapure
water (UPW) is poured on polishing pad surface 18 from a
conventional polishing slurry delivery apparatus (not shown). The
polishing slurry, in cooperation with the rotating motion of wafer
12 and pad 14, acts to remove a portion of the wafer's surface
unevenness.
[0024] As mentioned above, it is necessary to "condition" or
"redress" surface 18 of polishing pad 14 to remove the
glaze/build-up of polishing slurry from the pad's surface, as well
as to remove accumulated debris and other materials associated with
the polishing process itself. In the arrangement as shown in FIG.
1, an end effector arm 20 is used to perform the conditioning
process, where arm 20 moves in an arc A about a fixed shaft 21 and
simultaneously provides a rotational motion R and a downward force
F on an attached conditioner head 22. FIG. 2 shows, in a top view,
the relative motions of arm 20, conditioner head 22 and polishing
pad 14, illustrating in particular arc movement A of arm 20 across
the surface of polishing pad 14. In an alternative embodiment, the
end effector can be configured to cover a full radius of polishing
pad 14, such that it conditions surface 18 without the need of the
arc-based sweeping motion. The apertured conditioning brush of the
present invention, as discussed in detail below, may be used with
either embodiment. The apertured conditioning brush of the present
invention is equally applicable for use in systems that include
polishing felts instead of polishing pads, where the felts have the
same deep nap configuration as the soft polishing pads discussed
above. That is, the polishing pads and polishing felts best suited
for conditioning with the apertured brush of the present invention
are characterized by a microstructure exhibiting vertically
oriented, open pores (e.g., poromeric coating), capable of trapping
debris and fluids in recirculating eddies, as discussed above.
[0025] Referring back to FIG. 1, conditioner head 22 is shown as
further comprising an apertured conditioning brush 30, formed in
accordance with the present invention to perform the functions of:
(1) brushing surface 18 of polishing pad 14 to loosen debris lodged
deep within pad 14; (2) evacuating the conditioning fluid,
dislodged debris and/or spent polishing fluid (hereinafter referred
to as "effluent") from the vicinity of polishing pad 14; and,
possibly, (3) introducing conditioning fluids onto surface 18 of
pad 14. Conventional abrasive conditioning disks are not always
successful in removing debris deeply embedded within the pores of
some of the more fibrous polishing pads and polishing felts. A
plurality of bristles, as described below, are included in
contacting surface 31 of conditioning brush 30 and will enter the
deep pores of the fibrous polishing pad to dislodge accumulated
debris. Apertures formed within conditioning brush 30 provide a
channel for the removal of effluent through a vacuum path, where in
FIG. 1 conditioner head 22 is illustrated as including a vacuum
outlet port 37 coupled to a vacuum source 50. Conditioning fluids
may be used in combination with the surface brush to efficiently
remove accumulated debris, where the conditioning fluids may be
disposed onto the surface of polishing pad 18 through an inlet port
39 in conditioner head 22.
[0026] FIG. 3 contains a top view of an exemplary apertured
conditioning brush 30 as fixed within conditioner head 22, where
illustrated surface 31 will contact the surface of a polishing pad
during conditioning. There exist various arrangements for attaching
conditioning brush 30 to conditioner head 22, where a particularly
suitable arrangement that maintains apertured alignment between
brush 30 and the remaining components of conditioning disk 22,
using a magnetic-based hex key arrangement, is disclosed in
co-pending application Ser. No. 10/819,754, filed Apr. 7, 2004, and
assigned to the assignee of this application. Referring to FIG. 3,
a plurality of apertures 34 are shown, where apertures 34 are
surrounded by a plurality of bristles 40 that function to provide
the soft pad brushing in accordance with the present invention.
FIG. 4 is a cut-away side view of the arrangement of FIG. 3.
Bristles 40 function to dislodge particulate matter from the
fibrous pores below surface 18 of pad 14 (see FIG. 5) and push the
effluent through apertures 34 toward vacuum outlets 35 around the
outer periphery of conditioner head 22, as shown in FIG. 4. The
rotation of conditioner head 22 will assist in moving the effluent
outward through vacuum outlets 35 into an evacuation channel 36.
The effluent is then pulled, by vacuum force, through vacuum exit
port 37 on conditioner head 22, providing an efficient cleaning of
polishing pad surface 18. In the particular embodiment as
illustrated in FIG. 4, conditioning brush 30 further comprises a
channel system 32 coupled to apertures 34 to allow for the
introduction of conditioning fluids, if desired, via inlet port 39
of conditioner head 22.
[0027] FIG. 5 illustrates, in a simplified view, the relationship
between pad 14, conditioner head 22 and bristles 40. As mentioned
above, bristles 40 are formed to stand off a predetermined distance
below conditioner head 22, allowing for bristles 40 to enter the
deep, soft-walled pores of polishing pad 14 during conditioning,
while maintaining the integrity of the vacuum connection or seal
between pad 14 and conditioner head 22. As shown, bristles 40
extend deep enough into vertically-oriented open pores P of pad 14
so that the accumulated debris may be dislodged as conditioning
brush 30 sweeps across the pad surface. The length of bristles 40
is controlled, however, so that sidewalls 22W of conditioner head
22 maintain contact with surface 18 of polishing pad 14. It is to
be understood that the particular dimensions of the bristles will
be a function of parameters such as, but not limited to, the depth
of the pores of the fibrous polishing material, the pad material
itself, the downforce applied by the conditioner head to the
polishing pad, and the applied vacuum force. The contact between
surface 18 and conditioner head sidewalls 22W is required so that
the vacuum force/leakage is controllable and the debris will
continue to be evacuated from pad surface 18, through conditioning
brush 30 and exit from vacuum outlet port 37 of conditioner head
22. Bristles 40 comprise an inert material, such as nylon, that
will not react with any of the chemicals that may be present at the
pad surface, such as polishing slurry, conditioning liquids, wafer
debris material and the like. In a specific embodiment, bristles 40
may be formed of an abrasive-filled composite material that will
provide an even greater amount of cleaning energy to surface 18 of
conditioning pad 14.
[0028] FIG. 6 is a top view of an alternative conditioning brush
60, where in this particular embodiment, bristles 40 are disposed
in V-like patterns 62 across surface 61 of brush 60. For the sake
of clarity, only a portion of bristles 40 are shown in position in
FIG. 6. FIG. 7 is a top view of conditioning brush 60 with a
complete set of bristles 40 in place. Referring back to FIG. 6, a
set of apertures 34, is shown as disposed between each V pattern 62
of bristles. Apertures 34 function in the manner discussed above to
dispense conditioning liquids and evacuate effluent from surface 18
of polishing pad 14.
[0029] FIG. 8 contains a top view of yet another embodiment of an
apertured conditioning brush formed in accordance with the present
invention. In this arrangement, a conditioning brush 70 comprises
bristles 40 arranged in a set of spiral arms 72 emanating from a
central area 74 of brush 70. Apertures 34 are similarly arranged in
a spiral arm configuration, with a separate set of apertures 34
disposed between adjacent sets of bristles 40. As with the
arrangement described above in association with FIG. 4, bristles 40
and apertures 34 of brush 70 are designed so as to channel the
debris toward the outer periphery for efficient removal through
evacuation.
[0030] It is to be understood that the apertured conditioning brush
of the present invention can be used in association with any type
of polishing pad, or polishing felt, but is preferably intended for
use with the fibrous polishing and/or buffing pads as discussed
above that consist of deep, soft-walled, vertically-oriented pores
conducive to the creation of recirculating eddy currents deep
within the pad that trap the debris and spent slurry. The apertured
conditioning brush of the present invention may also be utilized
with conventional (i.e., relatively "hard") polishing pads, where
abrasive bristles provide sufficient surface abrasion, with lower
pad wear rates, than traditional abrasive conditioning disks.
Moreover, the arrangement of the bristles and apertures across the
surface of the conditioning brush may be modified, as need be, to
suit the needs of the particular CMP system. Indeed, the subject
matter of the present invention is intended to be limited only by
the scope of the claims appended hereto.
* * * * *