U.S. patent application number 11/420512 was filed with the patent office on 2006-09-14 for process and apparatus for thinning a semiconductor workpiece.
This patent application is currently assigned to SEMITOOL, INC.. Invention is credited to Kert L. Dolechek, Raymon F. Thompson.
Application Number | 20060203418 11/420512 |
Document ID | / |
Family ID | 35910148 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060203418 |
Kind Code |
A1 |
Dolechek; Kert L. ; et
al. |
September 14, 2006 |
PROCESS AND APPARATUS FOR THINNING A SEMICONDUCTOR WORKPIECE
Abstract
The present invention provides system and apparatus for use in
processing wafers. The new system and apparatus allows for the
production of thinner wafers that at same time remain strong. As a
result, the wafers produced by the present process are less
susceptible to breaking. The unique system also offers an improved
structure for handling thinned wafers and reduces the number of
processing steps. This results in improved yields and improved
process efficiency.
Inventors: |
Dolechek; Kert L.;
(Kalispell, MT) ; Thompson; Raymon F.; (Kalispell,
MT) |
Correspondence
Address: |
WALLENSTEIN & WAGNER, LTD.
311 SOUTH WACKER DRIVE
53RD FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
SEMITOOL, INC.
655 West Reserve Drive
Kalispell
MT
|
Family ID: |
35910148 |
Appl. No.: |
11/420512 |
Filed: |
May 26, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10923131 |
Aug 20, 2004 |
|
|
|
11420512 |
May 26, 2006 |
|
|
|
Current U.S.
Class: |
361/234 ;
257/E21.219; 257/E21.233 |
Current CPC
Class: |
H01L 21/30604 20130101;
H01L 29/06 20130101; H01L 21/3083 20130101; H01L 21/67126 20130101;
H01L 21/302 20130101; H01L 21/68735 20130101; Y10S 438/959
20130101 |
Class at
Publication: |
361/234 |
International
Class: |
H01L 21/683 20060101
H01L021/683 |
Claims
1. A chuck for receiving and supporting a workpiece having a device
side and a back side, the device side having a rim disposed on a
peripheral portion thereof, the chuck comprising: a body for
supporting the workpiece having a groove formed in a surface of the
body for receiving the rim of the workpiece; and a compressible
member disposed in the groove, the compressible member forming a
seal with the rim.
2. The chuck of claim 1, wherein the body is comprised of a
material selected from the group consisting of
polytetrafluoroethylene, silicon carbide and ceramic.
3. The chuck of claim 1, wherein the retainer is comprised of a
chemically resistant polymer.
4. The chuck of claim 3, wherein the chemically resistant polymer
is polyvinylidenefluoride.
5. The chuck of claim 1, wherein the body is comprised of a porous
material.
6. The chuck of claim 1, wherein the body has at least one channel
connected to a vacuum actuator.
7. The chuck of claim 1, wherein the workpiece is secured to the
body by a vacuum seal.
8. A chuck for receiving and supporting a workpiece having a device
side and a back side, the device side having a rim disposed on a
peripheral portion thereof, the chuck comprising: a body for
supporting the workpiece and adapted to sealably engage the
workpiece, the body having a groove formed in a surface for
receiving the rim of the workpiece; and a member disposed in the
groove, the member forming a seal between the rim and the body when
the rim of the workpiece is received in the groove.
9. A chuck for receiving and supporting a workpiece having a device
side and a back side, the device side having a rim extending
outwardly from a peripheral portion thereof, the chuck comprising:
a body for supporting the workpiece, the body having a groove
formed therein; a retainer removeably attached to the body and
adapted to engage the rim and the body thereby securing the
workpiece to the body; and a compressible member disposed in the
groove in the body and forming a seal with the rim.
10. The chuck of claim 9, wherein the retainer comprises at least
two engaging members.
11. The chuck of claim 10, wherein the first engaging member
contacts the rim and the second engaging member contacts the
body.
12. The chuck of claim 9, wherein the rim is comprised of a
polymer.
13. The chuck of claim 12, where the polymer is epoxy.
14. The chuck of claim 12, wherein the polymer is a polyolefin.
15. The chuck of claim 14, wherein the polyolefin is selected from
the group consisting of polyethylene, polyvinylchloride and
polyvinyldienefluoride.
16. The chuck of claim 9, wherein the body is comprised of a
material selected from the group consisting of
polytetrafluoroethylene, silicon carbide and ceramic.
17. The chuck of claim 9, wherein the retainer is comprised of a
chemically resistant polymer.
18. The chuck of claim 17, wherein the chemically resistant polymer
is polyvinylidenefluoride.
19. The chuck of claim 9, wherein the body has a step formed at the
outer periphery thereof for receiving the rim.
20. The chuck of claim 9, wherein the compressible member is
comprised of a perfluoroelastomer material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a Division of U.S. patent application
Ser. No. 10/923,131 filed Aug. 20, 2004, now pending. Priority to
this Application is claimed under 35 U.S.C. .sctn. 121. The
above-identified Application is also incorporated herein by
reference.
TECHNICAL FIELD
[0002] The invention relates to a process and apparatus for use
with workpieces, such as semiconductor wafers, flat panel displays,
rigid disk or optical media, thin film heads or other workpieces
formed from a substrate on which microelectronic circuits, data
storage elements or layers, or micro-mechanical elements may be
formed. These and similar articles are collectively referred to
herein as a "wafer" or "workpiece." Specifically, the present
invention relates to a process and apparatus for use in thinning
semiconductor workpieces.
BACKGROUND OF THE INVENTION
[0003] State of the art electronics (e.g., cellular phones,
personal digital assistants, and smart cards) demand thinner
integrated circuit devices ("ICD"). In addition, advanced packaging
of semiconductor devices (e.g., stacked dies or "flip-chips")
provide dimensional packaging constraints which require an
ultra-thin die. Moreover, as operating speeds of ICDs continue to
increase heat dissipation becomes increasingly important. This is
in large part due to the fact that ICDs operated at extremely high
speeds tend to generate large amounts of heat. That heat must be
removed from the ICD to prevent device failure due to heat stress
and to prevent degradation of the frequency response due to a
decrease in carrier mobility. One way to enhance thermal transfer
away from the ICD, thereby mitigating any deleterious temperature
effects, is by thinning the semiconductor wafer from which the ICD
is fabricated. Other reasons for thinning the semiconductor wafer
include: optimization of signal transmission characteristics;
formation of via holes in the die; and minimization of the effects
of thermal coefficient of expansion between an individual
semiconductor device and a package.
[0004] Semiconductor wafer thinning techniques have been developed
in response to this ever increasing demand for smaller, higher
performance ICDs. Typically, semiconductor devices are thinned
while the devices are in wafer form. Conventional wafer thicknesses
vary depending on the size of the wafer. For example, the thickness
of a 150 mm diameter silicon semiconductor wafer is typically about
650 microns, while wafers having a diameter of 200 or 300 mm are
generally about 725 microns thick. Mechanical grinding of the back
side of a semiconductor is one standard method of thinning wafers.
Such thinning is referred to as "back grinding." Generally, the
back grinding process employs methods to protect the front side or
device side of the semiconductor wafer. Conventional methods of
protection of the device side include the application of a
protective tape or a photoresist layer to the device side of the
wafer. The back side of the wafer is then ground until the wafer
reaches a desired thickness.
[0005] However, conventional back grinding processes have
drawbacks. Mechanical grinding induces stress in the surface and
edge of the wafer, including micro-cracks and edgechipping. This
induced wafer stress can lead to performance degradation and wafer
breakage resulting in low yield. In addition, there is a limit to
how much a semiconductor wafer can be thinned using a back grinding
process. For example, semiconductor wafers having a conventional
thickness (as mentioned above) can generally be thinned to a range
of approximately 250-150 microns.
[0006] Accordingly, it is common to apply a wet chemical etch
process to a semiconductor wafer after it has been thinned by back
grinding. This process is commonly referred to as stress relief
etching, chemical thinning, chemical etching, or chemical
polishing. The aforementioned process relieves the induced stress
in the wafer, removes grind marks from the back side of the wafer
and results in a relatively uniform wafer thickness. Additionally,
chemical etching after back grinding thins the semiconductor wafer
beyond conventional back grinding capabilities. For example,
utilizing a wet chemical etch process after back grinding allows
standard 200 and 300 mm semiconductor wafers to be thinned to 100
microns or less. Wet chemical etching typically includes exposing
the back side of the wafer to an oxidizing/reducing agent (e.g.,
HF, HNO.sub.3, H.sub.3PO.sub.4, H.sub.2SO.sub.4) or alternatively
to a caustic solution (e.g., KOH, NaOH, H.sub.2O.sub.2). Examples
of wet chemical etching processes may be found in co-pending U.S.
patent application Ser. No. 10/631,376, assigned to the assignee of
the present invention. The teachings of patent application Ser. No.
10/631,376 are incorporated by reference.
[0007] Although methods for thinning semiconductor wafers are
known, they are not without limitations. For example, mounting a
semiconductor wafer to a submount or "chuck" (as it is commonly
known) so that the wafer can be thinned requires expensive coating
and bonding equipment and materials, increased processing time, and
the potential for introducing contaminates into the process area.
Additionally, adhesives for bonding a wafer to a chuck that may be
useful in a mechanical grinding process will not withstand the
chemical process fluids used in wet chemical etching. Furthermore,
the current use of a photoresist or adhesive tape fails to provide
mechanical support for very thin wafers either during the back
grind process or in subsequent handling and processing. The use of
tape also creates obstacles in the removal process. For example,
tape removal may subject a wafer to unwanted bending stresses. In
the case of a photoresist, the material is washed off the device
side of a wafer with a solvent, adding to the processing time and
use of chemicals, and increasing the risk of contamination. The use
of taping and protective polymers are also costly, since both
equipment and materials are necessary to apply and remove the
protective media.
[0008] Further, thinned semiconductor wafers are prone to warping
and bowing. And because thinned semiconductor wafers can be
extremely brittle, they are also prone to breakage when handled
during further processing. Thinned semiconductor wafers (e.g.,
below 250 microns) also present complications in automated wafer
handling because, in general, existing handling equipment has been
designed to accommodate standard wafer thicknesses (e.g., 650
microns for 150 mm wafer and 725 microns for 200 and 300 mm
wafers).
[0009] Accordingly there is a need for a process and equipment for
producing thinner semiconductor workpieces. At the same time, there
in a need to provide thinner workpieces that are strong enough to
be handled by conventional equipment to minimize the threat of
breakage. Finally, it would be advantageous to develop a system
that reduces the number of processing steps for thinning a
semiconductor workpiece.
SUMMARY OF THE INVENTION
[0010] The present invention provides a method and apparatus for
use in processing wafers. The new system and apparatus allows for
the production of thinner wafers that at the same time remain
strong. As a result, the wafers produced by the present process are
less susceptible to breaking. The unique system also offers an
improved workpiece structure for handling thinned wafers and
reduces the number of processing steps. This results in, among
other things, improved yields and improved process efficiency.
[0011] In one aspect, the present invention provides a chuck for
receiving and supporting a workpiece having a device side and a
back side. The device side of the workpiece includes a rim disposed
on a peripheral portion thereof. The chuck includes a body for
supporting the workpiece that has a groove or aperture formed in a
surface of the body for receiving the rim of the workpiece. The
chuck also includes a compressible member disposed in the groove
for forming a seal between the body and the rim of polymeric
material. A vacuum seal is created between the workpiece and the
chuck body, securing the workpiece to the chuck for processing.
[0012] In another aspect, the present invention provides a chuck
for receiving and supporting a workpiece having a rim disposed on a
peripheral portion thereof. The chuck includes a body for
supporting the workpiece and a retainer removeably attached to the
body that is adapted to snap over and surround a portion of the rim
securing the workpiece to the body. The chuck further includes a
compressible member that forms a seal between the body and the rim.
The chucks disclosed by the present invention can be used to
process semiconductor workpieces that are strong, can be handled by
conventional automated handling equipment and have thicknesses of
less than 125 microns.
[0013] Several processes for thinning a semiconductor workpiece are
also provided. The process includes the steps of placing the
semiconductor workpiece having a rim onto a chuck body so that a
back side of the workpiece is exposed. Using a mechanical retainer
or a vacuum seal, the workpiece is secured to the chuck. The back
side of the workpiece is then thinned to a desired thickness
(preferably less than 125 microns).
[0014] These and other objects, features and advantages of this
invention are evident from the following description of preferred
embodiments of this invention, with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view of a chuck according to the
present invention with a workpiece having a polymer rim bonded to
the workpiece disposed thereon.
[0016] FIG. 2 is a partial enlarged of the chuck and workpiece
assembly show in FIG. 1, demonstrating the cooperation between the
chuck and the workpiece.
[0017] FIG. 3 is a top view of the chuck shown in FIG. 1.
[0018] FIG. 4 is a cross-sectional view of yet another embodiment
of a chuck according to the present invention with a workpiece
having a polymer rim disposed thereon.
[0019] FIG. 5 is a partial enlarged view of the area designated A
in FIG. 4 showing a vacuum actuator.
[0020] FIG. 6 is a partial enlarged view of the area designated B
in FIG. 4 showing the cooperation between the chuck and the
workpiece.
[0021] FIG. 7 is a cross-sectional view of yet another embodiment
of a chuck according to the present invention with a workpiece
having a polymer rim disposed thereon.
[0022] FIG. 8 is a partial enlarged view of the area designated A
in FIG. 7 showing the cooperation between the chuck and the
workpiece.
[0023] FIG. 9 is a top perspective view of the chuck shown in FIG.
7.
[0024] FIG. 10 is a partial enlarged view of a variation of the
engagement seal show in FIG. 8.
[0025] FIG. 11 is a cross-sectional view of yet another embodiment
of a chuck according to the present invention with a workpiece
having a polymer rim disposed thereon.
[0026] FIG. 12 is a partial enlarged view of the area designated A
in FIG. 11 showing the cooperation between the chuck and the
workpiece.
[0027] FIG. 13 is a top perspective view of the chuck show in FIG.
11.
[0028] FIG. 14 is a cross-sectional view of yet another embodiment
of a chuck according to the present invention with a workpiece
having a polymer rim disposed thereon.
[0029] FIG. 15 is a partial enlarged view of the area designated A
in FIG. 14 showing the cooperation between the chuck and the
workpiece.
[0030] FIG. 16 is a top perspective view of the chuck shown in FIG.
14.
[0031] FIG. 17 is a cross-sectional of yet another embodiment of a
chuck according to the present invention with a workpiece having a
polymer rim disposed thereon.
[0032] FIG. 18 is a partial enlarged view of the area designated A
in FIG. 17 showing the cooperation between the chuck and the
workpiece.
[0033] FIG. 19 is a top perspective view of the chuck shown in FIG.
17.
[0034] FIG. 20 is a cross-sectional of yet another embodiment of a
chuck according to the present invention with a workpiece having a
polymer rim disposed thereon.
[0035] FIG. 21 is a partial enlarged view of the area designated A
in FIG. 20 showing the cooperation between the chuck and the
workpiece.
[0036] FIG. 22 is a cross-sectional view of an engagement seal
between the chuck and the workpiece according to another embodiment
of the present invention.
[0037] FIG. 23 is a flow diagram illustrating a process for
thinning a workpiece according to one embodiment of the present
invention.
[0038] FIG. 24 is a flow diagram illustrating a process for
thinning a workpiece according to another embodiment of the present
invention.
DETAILED DESCRIPTION
[0039] With reference to FIGS. 1-6, there is shown a chuck 10 for
supporting a workpiece 50 during processing in accordance with one
embodiment of the present invention. In accordance with the
embodiment, the chuck 10 is comprised of an outer body 12 removably
engaged to an inner body 14. When engaged, the outer body 12 and
inner body 14 define a groove 16 around a peripheral portion of the
chuck 10. The groove 16 houses an annular gasket 22 and accepts the
polymer rim 60 that is bonded to the workpiece 50. A vacuum must be
applied to secure the workpiece 50 to the chuck 10.
[0040] As best illustrated in FIG. 3, the chuck 10 of present
invention has a cylindrical shape. The top of the chuck body 18
includes a series of channels 20 which communicate a vacuum to the
workpiece, thus creating a seal between the workpiece and the inner
body 14 of the chuck 10. The chuck 10 further comprises an annular
gasket 22 formed from a compressible material to create a seal
between the polymer rim 60 and the outer body 12 of the chuck 10.
As illustrated in FIGS. 2 and 6, the annular gasket 22 is shaped
like an "O-ring" but it is contemplated that other shapes can be
used as well. The annular gasket 22 is preferably formed from a
suitable elastomeric material, for example: a perfluoroelastomer
sold by DuPont under the tradename Kalrez or sold by Greene, Tweed
& Co. under the tradename Chemraz; fluoruelastomers sold by
DuPont under the tradename Viton; and hydrocarbon elastomers sold
under the tradename EPDM. The annular gasket 22 creates a flexible
interface between the workpiece 50 and the chuck 10 to relieve some
of the stress that is exerted on the workpiece 50 during assembly
and disassembly of the chuck 10.
[0041] Referring to FIGS. 1, 4 and 5, the chuck 10 also includes a
spring 24 and elastomer poppet 26 to actuate and release the vacuum
source. As explained above, a vacuum is applied to create the seal
formed between the workpiece 50 and the chuck 10.
[0042] The outer body 12 of the chuck 10 can be made from a number
of different polymer materials. Preferably the outer body 12
comprises polytetrafluoroethylene. The inner body 14 of the chuck
10 preferably comprises a fluoropolymer such as polyvinylidene
fluoride sold by Atofina Chemicals under the KYNAR tradename, or a
silicon carbide, or ceramic material, which is channeled or porous
to create volume for the vacuum seal between the chuck 10 and the
workpiece 50. The preferred materials for fabrication are those
that are both stable and highly chemically resistant.
[0043] While the chuck 10 can be used to support a variety of
workpieces, it is particularly suited for use with semiconductor
wafers, flat panel displays, rigid disk or optical media, thin film
heads or other workpieces formed from a substrate on which
microelectronic circuits, data storage elements or layers, or
micro-mechanical elements may be formed. The workpiece 50 for use
with the chuck 10 shown in FIGS. 1-6 is generally in the form of
circular wafers, such as circular semiconductor wafers.
Accordingly, the workpiece 50 has a front side 52, commonly
referred to as a device side, and a back side 54 which is typically
the side that is processed, by for example a back grinding or etch
method. A detailed explanation of semiconductor etching processes
is disclosed in U.S. Pat. No. 6,632,292, assigned to the assignee
of the present invention, and incorporated herein by reference.
Much like conventional wafers, the workpiece 50 of the present
invention will generally have a thickness within the range of 650
to 725 microns before processing; however, a workpiece having
thicknesses below 625 microns may also be used.
[0044] Unlike previous workpieces used in the art, the workpieces
50 in accordance with the invention include a polymer rim 60 bonded
to either the device side 52 or the back side 54 thereof. As
illustrated in FIGS. 2 and 6, the workpiece 50 has a polymer rim 60
bonded to the outer periphery 56 of the device side 54. The polymer
rim 60 will be bonded to a peripheral portion of the device side of
the workpiece section and preferably occupy less than 5% of the
device side surface area (DSSA), more preferably less than 3% of
the DSSA, or even less than 1% of the DSSA. Most preferably, the
polymer rim will be bonded to the device side on an area commonly
referred to in the art as the "exclusion zone".
[0045] The polymer rim 60 will generally have a thickness in a
range of about 0.030-0.190 inch and most preferably around
approximately 0.125 inch. The polymer rim 60 has two straight edges
62, 64 in this example. However, as will be discussed below, other
shapes and configurations for the polymer rim 60 may also be used.
The polymer rim 60 provides both support and strength to the
workpiece 50, particularly to workpieces that have undergone a
conventional back-grinding or etching process. Workpieces in
accordance with the present invention after processing can have
thicknesses of between 25 to 500 microns and still remain strong
enough to be handled by conventional processing equipment. The
thickness of the polymer rim 60 remains constant and the wafer is
thinned from a pre-thinned thickness of about 650-725 microns to
any desired final thickness; for example, less than 300 microns,
preferably less than 150 microns, more preferably less than 125
microns, especially less than 100 microns, even less than 50
microns, or less than 25 microns.
[0046] In addition, the polymer rim 60 protects the edge 58 of the
workpiece 50 from damage during processing, improves process
uniformity and simplifies workpiece handling by allowing equipment
to interface with the polymer rim rather than the workpiece. As
seen in FIGS. 2 and 6, the polymer rim 60 interfaces with the
annular gasket 22 instead of the workpiece thus reducing the
probability of damage to the workpiece during processing.
[0047] The polymer rim 60 preferably comprises a thermoset polymer,
e.g., an epoxy or similar material. A preferred epoxy for use in
accordance with the present invention is sold by 3D Systems under
the ACCURA SI-40 Nd tradename. While the polymer rim may be applied
to the workpiece by a number of different methods, the preferred
method utilizes an epoxy stereolithography machine. Such a process
generally involves placing the workpiece into a stereolithography
machine and growing the polymer rim onto the workpiece using a
laser that develops the liquid epoxy into the required geometry of
the polymer rim. The workpiece with the polymer rim is then
thermally baked to cure the epoxy. By curing the epoxy the chemical
resistance and the strength of the epoxy are enhanced.
[0048] Alternative methods of bonding the polymer rim 60 to the
workpiece 50 include machining the rim from an appropriate
thermoplastic polymer, such as polyvinyldienefluoride (PVDF),
polyvinylchloride (PVC) or polyethylene, and then bonding the rim
to the workpiece using a suitable bonding agent. A number of
adhesives can be used as bonding agents to secure the polymer rim
to the workpiece including: Corro-Coat FC 2100 N epoxy, Crystalbond
509 Hot Stick, Crystalbond 590 Hot Stick and 3M Jet-Melt Adhesive
3796. In the alternative, tape can be used to secure the polymer
rim to the workpiece. Suitable tapes for use with the present
invention include double coated tapes sold by 3M under the product
numbers 3M 9495MP 5 mm double-coated, 3M 444 4 mm double-coated, 3M
9490LE 6 mm double-coated, and ultra violet tapes, for example a UV
tape sold by Furukawa under product number SP-552M-130.
[0049] Turning specifically to FIGS. 7-9 an alternative embodiment
of the present invention is shown. In accordance with that
embodiment, the chuck 10 has a body 18 having a raised inner
portion 28 for supporting the workpiece 50. The chuck 10 also
includes a lower portion 30 and a groove 32 extending around the
outer periphery of the chuck. The groove 32 is adapted to house the
annular gasket or O-ring 22 which helps to seal the workpiece 50 to
the chuck 10.
[0050] The chuck 10 also includes a retainer 100. As illustrated in
FIG. 8, the retainer 100 includes two engagement members 101 and
102. The first engagement member 101 is adapted to fit over an
exposed contact edge 66 of the polymer rim 60. The second
engagement member 102 is adapted to fit under a ridge 34 on the
lower body the chuck 10 to mechanically seal the workpiece 50 to
the chuck 10. Unlike the chuck discussed above in relation to FIGS.
1-6, no vacuum is required to secure the workpiece to the chuck
shown in FIGS. 7-9. Instead, a simple snap engagement retains the
workpiece to the chuck. The mechanical seal offers a more robust
seal between workpiece and the chuck ensuring that any processing
fluid is prevented from migrating to the device side of the
workpiece benefits.
[0051] The retainer 100 includes a series of rinse holes 104 for
allowing any processing fluid to escape from any cavities formed
between the chuck 10 and the retainer 100. Recesses 36 are provided
on the lower body of the chuck 10 where the retainer 100 is secured
to the body of the chuck. A tool (not shown) can be inserted into
the recesses 36 so that the retainer 100 can be simply popped off
the chuck 10 after processing is completed.
[0052] As illustrated in FIG. 8, the workpiece 50 has a polymer rim
60 bonded to the outer periphery 56 having an "L-shaped"
configuration. The polymer rim 60 is bonded to the workpiece in the
same manner as described above and is within the same range of
thickness previously discussed. In this embodiment, the polymer rim
60 includes a beveled edge 68 for 3D fixturing and a flat edge 70
for ring fixturing. When the workpiece 50 is placed on the chuck
10, the polymer rim 60 acts as a primary sealing surface for
connecting the workpiece 50 to the chuck 10 thereby protecting the
edge 58 of the workpiece 50 from being damaged after processing. In
addition, the annular gasket or O-ring 22 interfaces with only with
an outer contact edge 66 of the polymer rim 60 further preventing
the likelihood of damage to the workpiece during processing. FIG.
10 illustrates a modification of the workpiece 50 shown in FIGS.
7-8. At one portion of the workpiece 50, the polymer rim 60 has an
extended flat edge 70. The extended flat edge 70 accommodates the
flat formed in conventional 150 mm semiconductor wafers.
[0053] FIGS. 11-13 illustrate still another configuration for the
chuck in which the annular gasket or O-ring 22 includes a flange
38. The flange 38 is adapted to be inserted into an aperture 40
provided in the body of the chuck 10. This helps secure the annular
gasket 22 within the groove 32, retaining the seal or annular
gasket 22 on the chuck body. In addition, the polymer rim 60 is
simplified having no flat or beveled edge as shown in FIG. 7.
Instead, the polymer rim 60 has a single contact edge 66. Referring
now to FIG. 13, the retainer 100 is provided with a plurality of
reliefs 106 along the periphery for assisting in the removal of the
retainer 100 from the body. The reliefs 106 are intended to
cooperate with fixturing tabs (not shown) or a tool (not shown) to
facilitate removal of the retainer 100. The configuration
illustrated in FIGS. 11-13 allows for simpler rim geometry while at
the same time retaining the seal or gasket to the body to ensure a
robust seal.
[0054] FIGS. 14-16 illustrate several alternative configurations
for the workpiece in which the polymer rim 60 is simplified having
no flat or beveled edge. In addition, the retainer 100 does not
include the reliefs seen in FIG. 16. While the polymer rim 60 in
FIG. 15 has a relatively short outer contact edge 66, a longer edge
may be provided as can be seen in FIGS. 17-18. The work piece 50
having a polymer rim 60 with a longer contact edge 66 can be used
in conjunction with the chuck 10 shown in FIG. 19. The chuck 10
includes a cutaway section 42 from the raised inner portion 28 that
accommodates the longer contact edge 66.
[0055] Referring now to FIGS. 20-22 additional configurations for
the retainer 100 for use with the present invention are shown. In
this embodiment, the retainer 100 has only one engagement member
101 that fits over the contact edge 66 of the polymer rim 60 on the
workpiece 50. The retainer 100 further includes a curved edge 108
which sealingly connects to a curved surface 40 on the body of the
chuck 10.
[0056] Turning now to the workpiece thinning processes, FIG. 23
illustrates one embodiment of a process that may be implemented
when the chuck and workpiece, having a polymer rim described above
are used, for example, to thin the back side of the workpiece. At
step 200, the workpiece that is to be thinned is placed onto the
chuck so that the back side of the wafer is left exposed. At step
205, a retainer is attached to the chuck body and the polymer rim
so that the workpiece is secured to the chuck. At step 210, the
chuck and workpiece are placed into a manual or automated process
chamber within a spray acid tool platform like those available from
Semitool, Inc., of Kalispell, Mont.
[0057] As indicated at step 215, a process fluid is then applied to
the back side of the workpiece to thin the workpiece to a desired
thickness. In a preferred embodiment the final desired thickness is
less than 50% of the original workpiece thickness, for example less
than 300 microns, preferably less than 125 microns, more preferably
less than 100 microns, especially less than 50 microns and even
less than 25 microns. Preferred process fluids for use with the
methods according to the present invention include deionized water,
hydrogen peroxide, ozone, potassium hydroxide, sodium hydroxide,
hydrofluoric acid, nitric acid, sulfuric acid, acidic acid and
phosphoric acid. Although preferred process fluids for the
disclosed application are discussed above, other treatment fluids
may also be used. For example, a number of other acidic and basic
solutions may be used, depending on the particular surface to be
treated and the material that is to be removed.
[0058] At step 220, the thinned workpiece is rinsed and dried. For
example, the workpiece may be sprayed with a flow of deionized
water during the rinsing step and may then be subject to any one or
more known drying techniques thereafter. The retainer is then
disengaged from the body and the workpiece is removed from the
chuck (See step 225). Finally, at step 230, the polymer rim is
removed from the thinned workpiece. The polymer rim can be cut off
the workpiece using a laser or the rim may be left on the workpiece
and cut off as scrap during the process of dicing the workpiece
into a plurality of dies.
[0059] FIG. 24 illustrates another embodiment of a process that may
be implemented when the chuck and workpiece, having a polymer rim
described above are used, for example, to thin the back side of the
workpiece. At step 300, the workpiece that is to be thinned is
placed onto the chuck so that the back side of the wafer is left
exposed. At step 305, a vacuum seal is created between the
workpiece and the chuck, securing the workpiece to the chuck. At
step 310, the chuck and workpiece are placed into a manual or
automated process chamber within a spray acid tool platform like
those available from Semitool, Inc., of Kalispell, Mont.
[0060] As indicated at step 315, a process fluid is then applied to
the back side of the workpiece to thin the workpiece to a desired
thickness. In a preferred embodiment the final desired thickness is
less than 300 microns, preferably less than 125 microns, more
preferably less than 100 microns, especially less than 50 microns
and even less than 25 microns. Preferably the workpiece is thinned
at a first semiconductor etch rate, and then as the semiconductor
workpiece nears the desired thickness, at a second semiconductor
etch rate preferably less than the first semiconductor etch rate.
The preferred process fluids for use in step 315 are the same as
those identified above with respect to step 215. Although preferred
process fluids for the disclosed application are disclosed, other
treatment fluids may also be used. For example, a number of other
acidic and basic solutions may be used, depending on the particular
surface to be treated and the material that is to be removed.
[0061] At step 320, the thinned workpiece is rinsed and dried. For
example, the workpiece may be sprayed with a flow of deionized
water or phosphoric acid during the rinsing step and may then be
subject to any one or more known drying techniques thereafter. The
workpiece is then removed from the chuck (See step 325). Finally,
at step 330, the polymer rim is removed from the thinned workpiece.
As mentioned above, the polymer rim can be cut off the workpiece
using a laser or the rim may be left on the workpiece and cut off
as scrap when the workpiece is diced into a plurality of dies.
[0062] Numerous modifications may be made to the foregoing
invention without departing from the basic teachings thereof.
Although the present invention has been described in substantial
detail with reference to one or more specific embodiments, those of
skill in the art will recognize that changes may be made thereto
without departing from the scope and spirit of the invention.
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