U.S. patent application number 09/741489 was filed with the patent office on 2002-06-20 for reinforced cmp carrier bladders.
This patent application is currently assigned to SpeedFam-IPEC Corporation. Invention is credited to Arai, Hatsuyuki, Dyer, Timothy S., Fruitman, Clinton O., Gopalan, Periya, Lougher, Wayne.
Application Number | 20020077049 09/741489 |
Document ID | / |
Family ID | 24980921 |
Filed Date | 2002-06-20 |
United States Patent
Application |
20020077049 |
Kind Code |
A1 |
Fruitman, Clinton O. ; et
al. |
June 20, 2002 |
Reinforced CMP carrier bladders
Abstract
A reinforced bladder for a chemical-mechanical planarization
(CMP) polishing device includes an elastomer infused with a
reinforcing material. The elastomer can be a rubber such as EPDM.
The reinforcing material can be a chopped fiber such as aramid.
Alternatively, the reinforcing material can be a sheet (such as a
triaxial or hexaxial weave of aramid) embedded in and infused with
the elastomer.
Inventors: |
Fruitman, Clinton O.;
(Chandler, AZ) ; Dyer, Timothy S.; (Tempe, AZ)
; Gopalan, Periya; (Chandler, AZ) ; Lougher,
Wayne; (Phoenix, AZ) ; Arai, Hatsuyuki;
(Zama-city, JP) |
Correspondence
Address: |
Laura Zeman
Snell & Wilmer L.L.P.
One Arizona Center
400 East Van Buren
Phoenix
AZ
85004
US
|
Assignee: |
SpeedFam-IPEC Corporation
|
Family ID: |
24980921 |
Appl. No.: |
09/741489 |
Filed: |
December 15, 2000 |
Current U.S.
Class: |
451/397 |
Current CPC
Class: |
B24B 41/061 20130101;
B24B 37/30 20130101 |
Class at
Publication: |
451/397 |
International
Class: |
B24B 005/00; B24B
047/02 |
Claims
We claim:
1. A bladder for use in a carrier of a CMP tool, comprising an
elastomer infused with a reinforcing material, wherein the
reinforcing material increases the rigidity of the bladder.
2. The bladder of claim 1 wherein the elastomer comprises an
ethylyne-propolyne-diene monomer compound.
3. The bladder of claim 1 wherein the reinforcing material
comprises a plurality of fibers.
4. The bladder of claim 3 wherein the plurality of fibers includes
multifilament spun fiber.
5. The bladder of claim 3 wherein the plurality of fibers comprises
woven fibers.
6. The bladder of claim 3 wherein the plurality of fibers comprises
chopped aramid fiber.
7. A bladder for use in a carrier of a chemical-mechanical
planarization (CMP) tool, comprising: an elastomer shaped to form
the bladder; and a sheet of reinforcing material, wherein the sheet
of reinforcing material is embedded in and infused with
elastomer.
8. The bladder of claim 7 wherein the elastomer comprises an
ethylyne-propolyne-diene monomer compound.
9. The bladder of claim 7 wherein the sheet of reinforcing material
comprises aramid fiber.
10. The bladder of claim 7 wherein the sheet of reinforcing
material comprises a triaxial weave of fiber.
11. The bladder of claim 7 wherein the sheet of reinforcing
material comprises a hexaxial weave of fiber.
12. A bladder for use in a CMP tool, comprising: an elastomer
shaped in the form of a bladder; and means, infused in the
elastomer, for reinforcing the elastomer, wherein the bladder has
increased rigidity.
13. The bladder of claim 12 wherein the means for reinforcing
comprises a plurality of fibers.
14. The bladder of claim 13 wherein the plurality of fibers
comprises chopped fiber.
15. The bladder of claim 12 wherein the means for reinforcing
comprises a sheet of reinforcing material.
16. The bladder of claim 15 wherein the sheet comp rises woven
aramid.
17. A method for polishing a workpiece using a CMP tool, the method
comprising: loading the workpiece in the CMP tool; polishing the
workpiece using the CMP tool, wherein the CMP tool includes a
reinforced bladder, wherein the reinforced bladder comprises an
elastomer infused with a reinforcing material.
18. The method of claim 17, wherein the reinforcing material
comprises a plurality of fibers.
19. The method of claim 18, wherein the plurality of fibers
includes multifilament spun fiber.
20. The method of claim 18, wherein the plurality of fibers
comprises chopped aramid fiber.
21. The method of claim 17, wherein the reinforcing material
comprises a sheet of reinforcing material.
22. The method of claim 21, wherein the sheet of reinforcing
material comprises aramid fiber.
23. A CMP tool for polishing a workpiece, comprising: means for
loading the workpiece; means for polishing the workpiece, the means
for polishing including a bladder, wherein the bladder comprises an
elastomer infused with a reinforcing material.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to chemical-mechanical
planarization (CMP) tools, and more particularly, to carriers for
holding semiconductor wafers during polishing periods, and
specifically to the bladders for use in carriers.
BACKGROUND
[0002] CMP tools are typically used to planarize the surface of a
semiconductor wafer or to remove the upper portion of a layer
formed on the semiconductor wafer (e.g., damascene processes). Some
conventional CMP tools also include a rotating or non-rotating
carrier to hold a wafer, and a rotating or orbiting platen or table
with a polish pad. The CMP tool causes the polish pad and the wafer
surface to come into contact, typically applying a specified
pressure between the polish pad and the wafer surface. The CMP tool
also imparts a relative motion between the wafer surface and the
polish pad. Additionally, the CMP tool typically introduces a
slurry at the interface between the polish pad and the wafer
surface. The slurry can have abrasive particles suspended in a
chemical solution that react with selected materials on the wafer
surface. The pressure, slurry and relative motion effectuate the
polishing.
[0003] This planarization or polishing is commonly accomplished by
securing the wafer to a carrier, rotating the carrier and placing
the rotating wafer in contact with a polishing pad mounted on a
platen. A conventional wafer carrier typically includes a hard flat
plate that does not conform to the surface of the wafer and is
therefore covered by a softer carrier film that allows the hard
plate to apply a more uniform polish pressure across the surface of
the wafer. This process is known in the industry as back
referencing technology. Back referencing is problematic in that in
practice, it does not do a good job of providing uniform pressure
on the wafer. In particular, when pressure is applied to the
backside of the wafer, any inconsistencies between the backside of
the wafer and the carrier film are translated to the front of the
wafer by virtue of the direct contact involved.
[0004] In an effort to reduce the amount of non-uniformity caused
by the back referencing technology, other systems use an inflatable
bladder instead of the soft carrier film. The bladder allows for a
two-way use of air. When a vacuum is applied and the bladder is in
contact with the wafer, the carrier will pick up and hold the wafer
in position. Next, the wafer is placed in contact with the
polishing pad. Finally, the airflow is then reversed so as to
provide a more uniform pressure between the wafer and the polish
pad. This technique is known as front referencing technology.
[0005] Conventional bladders tend to bunch up or wrinkle during the
polishing process. These wrinkles cause uneven local pressure to be
applied directly to the wafer, which in turn is translated to the
front side of the wafer to cause uneven polishing of the wafer.
Additionally, the sidewalls of the bladder are subject to bowing
and buckling during the polishing process, which contribute to the
problem. Therefore, there is a need for a simple and inexpensive
bladder that resists wrinkling, bowing and buckling compared to
conventional bladders without a loss in axial movement (needed when
vacuum and positive pressure are applied).
SUMMARY
[0006] In accordance with the aspects of the present invention, an
improved bladder for use in a CMP tool is provided. In one
embodiment of the present invention, the bladder is composed of an
elastomer infused with a reinforcing material. In a further aspect,
the elastomer is an ethylyne-propylene-diene monomer (EPDM) and the
reinforcing material is an aramid fiber. In one embodiment, the
aramid fiber is in the form of chopped fibers. The reinforcing
material advantageously increases the fatigue, tensile strength and
temperature tolerance performance of the bladder.
[0007] In another aspect of the invention, the bladder is formed
with a woven fiber sheet. In one embodiment, the fiber sheet is
formed using a triaxial/hexaxial weave where the sheet is infused
in the elastomer during the processing phase while the rubber is
still in a liquid state. This process allows the woven fabric to be
embedded in and bonded with the elastomer as opposed to being
laminated to the elastomer, resulting in similar advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a diagram illustrating a CMP polishing tool with a
back referencing bladder.
[0009] FIG. 2 is a cross-sectional view of the bladder and
retaining ring.
[0010] FIG. 2A is a diagram of the bladder and retaining ring
illustrating torque on the bladder surface.
[0011] FIG. 3 is a cross-sectional view of a bladder according to
one embodiment of the present invention.
[0012] FIG. 4 is a more detailed view of a section of the bladder
depicted in FIG. 3.
[0013] FIG. 5 is a cross-sectional view of a bladder according to
another embodiment.
[0014] FIG. 6 is a diagram illustrating a view of the inside
surface of the bottom of a bladder, according to one embodiment of
the present invention.
[0015] FIG. 7 is a diagram illustrating a view of the inside
surface of the bottom of a bladder according to another embodiment
of the present invention.
DETAILED DESCRIPTION
[0016] The present invention represents a significant departure
from conventional bladder technology employed in CMP tools by
infusing reinforcing material into the elastomer used to form the
bladders. This reinforcement provides, at a relatively low cost, a
chemical-mechanical polishing bladder that reduces both wrinkling
of the bladder face and buckle/bow of the bladder sidewall. In a
further refinement, the reinforcing material is a chopped fiber,
thereby facilitating the integration of the reinforcing material
into the elastomer. In another embodiment, woven fabric is infused
into the elastomer forming the bladder. This bladder technology is
detailed below.
[0017] FIG. 1 illustrates a standard CMP tool with a carrier 14,
platen 12, bladder 11, wafer 10, and a retaining ring 13, according
to one embodiment of the present invention. In this embodiment,
prior to polishing, a vacuum is applied between carrier 14 and
bladder 11. The vacuum is then transferred to wafer 10 by way of
the bladder 11 through perforations (not shown) in the bladder,
which in turn causes wafer 10 to maintain contact with bladder 11.
In another embodiment, selected areas of the bladder are molded to
be thinner to allow the vacuum to be transferred to the wafer. Once
the polishing process begins, the carrier 14 is moved so as to
cause wafer 10 to come into contact with platen 12, which typically
has a polishing pad mounted on its top surface. Positive air
pressure is then applied between the carrier 14 and bladder 11 to
inflate the bladder. The bladder provides uniform pressure to wafer
10, keeping the wafer in constant and uniform contact with platen
12.
[0018] FIG. 2 illustrates a cross-sectional view of the bladder 11
and its sidewall 22 component as well as retaining ring 13. During
the operation of the CMP tool, pressure and torque are exerted on
the bladder 11. When a vacuum is applied to the bladder, the
bladder surface experiences an inward pressure. This inward
pressure can cause a portion of the sidewall 22 to buckle in
conventional bladders. When contact is made between the wafer
10/bladder 11 combination and platen 12 this excess rubber between
the carrier 14 and platen 12 produces inconsistencies in the
pressure applied to the wafer 10. However, as will be described
below, a bladder according to the embodiments of the present
invention has reinforcing material that reduces buckling.
Similarly, when the bladder is inflated, the bladder surfaces
experience an outward pressure. This outward pressure can cause a
portion of the sidewall 22 to bow outward. This bowing stretches
the bladder 11 and its sidewall 22, thereby undesirably reducing
the useful life of bladder 11.
[0019] FIG. 2A illustrates the effect of torque .tau. on the
bladder face 11a. Bladder face 11A represents a three-dimensional
extension of the bottom surface of the bladder 11. During operation
both platen 12 and carrier 14 rotate to achieve optimal polishing.
Torque .tau. occurs when wafer 10 contacts platen 12 and rotates.
The bladder face 11a experiences torque due to the friction caused
by wafer 10 resisting rotation from platen 12. In conventional
bladders, this leads to wrinkling of the bottom surface of the
bladder face 11a. Unfortunately, due to the close proximity of
bladder face 11a to wafer 10 and platen 12, the wrinkles cause an
uneven buildup of rubber material along the back of the wafer.
These uneven buildups of rubber material are then translated to the
face of the wafer resulting in uneven polishing of the wafer. One
design objective of this invention is to limit wrinkling, bowing,
and buckling while allowing the bladder face 11a to have enough
axial movement to pick up and back-reference the wafer.
[0020] FIG. 3 illustrates a cross-sectional view of bladder 11 with
reinforcing material, according to one embodiment of the present
invention. The reinforcing material (e.g. see FIG. 4) is infused in
the elastomer of the bladder. In one embodiment, the bladder is
formed by adding the reinforcing material to an elastomer while the
elastomer is still in a liquid state. The elastomer is then formed
into a bladder using a standard injection molding process. Other
embodiments could use any elastomer so long as its chemical
properties are suitable for use in a CMP environment such as, for
example, ethylyne-propylene-diene monomer (EPDM) or styrene butyl
rubber (SBR) as well as other rubber materials.
[0021] FIG. 4 is a more detailed view of section 31 of bladder 11
(FIG. 3) and shows reinforcing material 41 infused in the elastomer
of bladder 11. In this embodiment, reinforcing material 41 is a
fiber material added during the injection molding process, as
previously described. In this embodiment, the reinforcing material
is chopped aramid fiber. Further, in this embodiment, the fibers
are about 2 mm in length with a diameter of 20 mm, and are added to
the elastomer to about 6% density by volume. In other embodiments,
the fiber length can range from 1 mm to 10 mm, with diameters
ranging from 20 mm to 50 mm, and density ranging from 3 to 10%,
depending on the size and application of the bladder, the
reinforcing material, etc. In a still further embodiment, chopped
KEVLAR.RTM. fiber is used. Although FIG. 4 shows the reinforcing
material 41 as being visible, in actual use, reinforcing material
41 is not visible when the 2 mm 6% density chopped KEVLAR.RTM. is
used. When the fiber density exceeds 10% the fiber in the bladder
can be visible to the naked eye, which may be undesirable in some
applications. Other embodiments could use other fibers including
any from the class of polyesters, or wool, cotton, or even glass
fibers. In general, multifilament spun fiber as well as para-aramid
fiber fabrics can be used so long as their properties meet the
requirements for use in a CMP tool.
[0022] FIG. 5 illustrates another embodiment of the present
invention. This embodiment uses a fiber sheet 51 embedded in the
face of the bladder for reinforcement. The sheet reinforcement 51
can be made of any suitable fiber listed above or of any fiber
whose properties would be suitable enough for use in a CMP tool. In
one embodiment, fiber sheet 51 is a fiber sheet formed using a
triaxial/hexaxial weave. The sheet is infused with the elastomer
during the processing phase while the rubber is still in a liquid
state. The triaxial/hexaxial weave of this embodiment of fiber
sheet 51 provides essential isotropic reinforcement of the bladder
face against wrinkling.
[0023] FIG. 6 is a diagram illustrating a view of the inside
surface of the bottom of a bladder, according to one embodiment of
the present invention and describes bladder 11 including sidewall
22 and bladder face 11a.
[0024] FIG. 7 is another embodiment of the invention illustrating a
multi-zone carrier bladder. FIG. 7 is similar to FIG. 6 with the
exception of an additional sidewall 72 that is used to define
another zone in the bladder. During the polishing process the
annular zone outside of sidewall 72 can have a different pressure
than the circular zone inside of sidewall 72. The pressures within
these zones may be varied as needed to achieve a desired removal
rate profile for a particular polishing application. Other
embodiments may have more than one sidewall, with four to five
zones being common.
[0025] Although the description above refers to wafers, other
embodiments of the present invention can be adapted for other types
of workpieces. For example, a workpiece may be semiconductor wafer,
a bare silicon or other semiconductor substrate with or without
active devices or circuitry, a partially processed wafer, a silicon
or insulator structure, a hybrid assembly, a flat panel display, a
micro electromechanical structure (MEMS), a disk for a hard drive
memory, or any other material that would benefit from cleaning or
planarization.
[0026] The above specification, examples and data provide a
complete description of the manufacture and use of the composition
of the invention. Since many embodiments of the invention can be
made without departing from the spirit and scope of the invention,
the invention resides in the claims hereinafter appended.
* * * * *