U.S. patent application number 09/918667 was filed with the patent office on 2001-11-29 for apparatus for processing a wafer.
Invention is credited to Ravkin, Michael.
Application Number | 20010044979 09/918667 |
Document ID | / |
Family ID | 23041660 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010044979 |
Kind Code |
A1 |
Ravkin, Michael |
November 29, 2001 |
Apparatus for processing a wafer
Abstract
A method and apparatus for processing wafer edges is disclosed.
Pressure applied to the wafer at one end of A brush/pad assembly is
greater than at the opposite end of the brush/pad assembly. The
increased pressure causes wafer rotation to slow or to reverse
direction as compared to less pressure applied by the brush/pad
assembly. In one embodiment slowed rotation causes a difference in
tangential velocity between the roller(s) and the wafer edge/bevel
that causes pads in the roller(s) to process the edge/bevel of the
wafer. In another embodiment, the opposite direction of rotation
causes the wafer to rotate counter to rollers otherwise causing the
wafer to rotate. Cleaning surfaces in the rollers clean the edges
of the wafer whether rotation is slowed or reversed.
Inventors: |
Ravkin, Michael; (Sunnyvale,
CA) |
Correspondence
Address: |
MARTINE & PENILLA, LLP
710 LAKEWAY DRIVE
SUITE 170
SUNNYVALE
CA
94085
US
|
Family ID: |
23041660 |
Appl. No.: |
09/918667 |
Filed: |
July 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09918667 |
Jul 27, 2001 |
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09272874 |
Mar 19, 1999 |
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6290780 |
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Current U.S.
Class: |
15/77 ; 15/102;
15/88.2; 15/88.3 |
Current CPC
Class: |
H01L 21/67046 20130101;
Y10S 134/902 20130101 |
Class at
Publication: |
15/77 ; 15/88.2;
15/88.3; 15/102 |
International
Class: |
B08B 001/04 |
Claims
What is claimed is:
1. An apparatus for processing a wafer, the apparatus comprising: a
first brush assembly positioned beneath the wafer to clean a first
side of the wafer; and a second brush assembly positioned above the
wafer to clean a second side of the wafer; a positioning mechanism
to position the first and second brush assemblies to create a
pressure applied non-uniformly across the wafer.
2. The apparatus of claim 1 further comprising a roller disposed to
rotate the wafer.
3. The apparatus of claim 2 wherein the roller includes a pad to
clean edges of the wafer.
4. The apparatus of claim 3 wherein the first and second brush
assemblies simultaneously clean the first and second sides of the
buffer, and wherein the nonuniform pressure affects rotation to
cause a difference in tangential velocity between the roller and
the wafer to contribute to cleaning one edge of the wafer.
5. The apparatus of claim 2 wherein the non-uniform pressure slows
rotation of the wafer as compared to rotation caused by the roller
alone.
6. The apparatus of claim 2 wherein the non-uniform pressure
reverses rotation of the wafer as compared to rotation caused by
the roller alone.
7. The apparatus of claim 1 wherein a first pressure is applied at
a first end of the first pad assembly and a second pressure is
applied at a second end of the first pad assembly, further wherein
the first pressure is greater than the second pressure.
8. The apparatus of claim 7 wherein the first pressure is
approximately twice the second pressure.
9. The apparatus of claim 7 wherein the first pressure is
approximately four times the second.
10. The apparatus of claim 1 wherein a first pressure is applied at
a first end of the second pad assembly and a second pressure is
applied at the second end of the second pad assembly, further
wherein the first pressure is greater than the second pressure.
11. The apparatus of claim 10 wherein the first pressure is
approximately twice the second pressure.
12. The apparatus of claim 10 wherein the first pressure is
approximately four times the second pressure.
13. The apparatus of claim 1 wherein a first pressure is applied at
a first end of the first pad assembly and a second pressure is
applied at a second end of the second pad assembly, further wherein
the first end is opposite the second end.
14. The apparatus of claim 13 wherein the first pressure is greater
than the second pressure.
15. The apparatus of claim 13 wherein the second pressure is
greater than the first pressure.
16. The apparatus of claim 1 wherein the pads are used to buff the
wafer.
17. The apparatus of claim I wherein the pads are used to polish
the wafer.
18. A method of processing a wafer, the method comprising:
supporting a wafer to be processed; applying a first pressure to
the wafer at a first portion of the wafer; and applying a second
pressure to the wafer at a second portion of the wafer, wherein the
first and second pressures combine to provide a nonuniform pressure
across the wafer.
19. The method of claim 18 cleaning an edge of the wafer by
creating a difference in tangential velocity between a roller
rotating the wafer contributed to the non-uniform pressure.
20. The method of claim 18, wherein at least the first pressure is
applied by a first pad assembly disposed above the wafer.
21. The method of claim 20 wherein the first pressure is applied at
a first end of the first pad assembly and the second pressure is
applied at a second end of the first pad assembly.
22. The method of claim 20, wherein support for the wafer is
provided by a second pad assembly disposed below the wafer.
23. The method of claim 22 wherein the first pressure is applied at
a first end of the second pad assembly and the second pressure is
applied at a second end of the second pad assembly.
24. The method of claim 22 wherein the first pressure is applied at
a first end of the first pad assembly and the second pressure is
applied at a second end of the second pad assembly, and further
wherein the first end is opposite the second end.
25. The method of claim 18 wherein the first pressure is greater
than the second pressure.
26. The method of claim 18 further comprising rotating the wafer
with a roller.
27. The method of claim 26 wherein the non-uniform pressure causes
rotation of the wafer to slow as compared to rotation of the wafer
with the roller alone.
28. The method of claim 26 wherein the non-uniform pressure causes
rotation of the wafer to reverse as compared to rotation of the
wafer with the roller alone.
29. The method of claim 26 wherein the roller includes a pad to
clean edges of the wafer.
30. An apparatus for processing wafers, the apparatus comprising:
means for supporting a wafer to be processed; means for applying a
first pressure to the wafer at a first portion of the wafer; and
means for applying a second pressure to the wafer at a second
portion of the wafer, wherein the first and second pressures
combine to provide a non-uniform pressure across the wafer.
31. The method of claim 30 means for cleaning an edge of the wafer
by creating a difference in tangential velocity between a roller
rotating the wafer contributed to the non-uniform pressure.
32. The apparatus of claim 30 further comprising roller means for
rotating the wafer.
33. The apparatus of claim 32 wherein the non-uniform pressure
causes rotation of the wafer to slow as compared to rotating the
wafer with the roller means alone.
34. The apparatus of claim 32 wherein the non-uniform pressure
causes rotation of the wafer to reverse as compared to rotating the
wafer with the roller means alone.
35. An improvement in a system for processing semiconductor wafers,
the improvement comprising: an assembly configurable to apply
non-uniform pressure to the semiconductor wafer sufficient to cause
rotation of the semiconductor wafer to be affected and edges of the
semiconductor wafer to thereby be processed.
36. A system for processing a semiconductor wafer comprising: brush
station having a first brush assembly having a first brush disposed
above the semiconductor wafer, a second brush assembly having a
second brush disposed below the semiconductor wafer, and a roller
assembly to rotate the semiconductor wafer; a control unit having a
processor and a memory coupled to the processor, the memory to
store sequences of instructions, which when executed by the
processor cause the brush station to apply non-uniform pressure to
the semiconductor wafer with the first and second brush
assemblies.
37. The system of claim 36 wherein the roller further includes a
pad for cleaning edges of the semiconductor wafer.
38. The system of claim 36 wherein the processor controls the
roller assembly to rotate the semiconductor wafer.
39. The system of claim 36 wherein the non-uniform pressure causes
rotation of the semiconductor wafer to slow.
40. The system of claim 36 wherein the non-uniform pressure causes
rotation of the semiconductor wafer to reverse.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to semiconductor wafer
processing; more particularly, the present invention relates to an
apparatus for use in buffing and/or cleaning the edge/bevel of
semiconductor wafers.
BACKGROUND OF THE INVENTION
[0002] Double sided scrubbers clean the top and the bottom of a
wafer simultaneously. Double sided scrubbers are usually automated
and comprise a conveyor type mechanism, rollers, and brushes. In
general, the wafer lies flat on the conveyor mechanism and the
conveyor mechanism moves the wafer into the brushes. While being
scrubbed, the wafer is supported (or held horizontally) by the
conveyor mechanism, brushes, rollers, or a combination thereof.
[0003] FIG. 1 is a general view of a conventional double sided
wafer processing station. Wafer 10 is processed by brushes, one of
which is shown as brush 20 and the other (not shown in FIG. 1) is
beneath wafer 10 and directly below brush 20. Rollers 30 rotate
wafer 10 so the entire wafer surface may be processed. Each of
brushes 20 is rotated about its central axis by motor 40. The
rotary motion of roller 30 is then transferred to wafer 10 when the
edge of each roller 30 comes into contact with the outer edge of
wafer 10.
[0004] Brush cleaning systems can effectively process the top and
bottom of semiconductor substrates. However, brushes do not provide
a sufficient amount of mechanical energy at the edge/bevel to
remove contamination. In other words, although double sided
scrubber of FIG. 1 is effective at cleaning the front and back side
of a wafer, it can leave a residue on the edge/bevel of the
wafer.
[0005] One solution to cleaning the edge/based areas is shown in
U.S. Pat. No. 5,861,066, entitled "Method and Apparatus for
Cleaning Edges of Contaminated Substrates", issued Jan. 19, 1999 in
which the edge and/or based areas may be cleaned using rollers that
contact the outer edge of a wafer, similar to roller 30 coming into
contact with wafer 10 above, except that one of the rollers
includes an abrasive area and rotates such that the tangential
velocity at the point of contact between the one roller and the
wafer is different than the speed at which the other roller rotates
the wafer. It is because of this difference in speed that the
edge/bevel area is cleaned by the abrasive area.
SUMMARY OF THE INVENTION
[0006] A method and apparatus for processing the edge of
semiconductor wafers is described. In one embodiment, a first brush
assembly is disposed beneath the wafer to provide support for and
to process the wafer and a second brush assembly is disposed above
the wafer to process the wafer. Pressure applied to the wafer is
non-uniform across the wafer.
[0007] In one embodiment, one or more rollers rotate the wafer
between the first and second brush assemblies. The non-uniform
pressure causes rotation of the wafer to slow or reverse. A pad in
one or more of the rollers cleans the edge of the wafer. In one
embodiment, the non-uniform pressure causes the first brush
assembly and/or the second brush assembly to clean the edge of the
wafer.
[0008] In one embodiment, the non-uniform pressure is applied with
the second brush assembly from above the wafer. In alternative
embodiments, the non-uniform pressure is applied with the first
brush assembly from below the wafer or some combination of the
first and second brush assemblies.
DESCRIPTION OF THE DRAWINGS
[0009] The present invention will be understood more fully from the
detailed description given below and from the accompanying drawings
of various embodiments of the invention, which, however, should not
be taken to limit the invention to the specific embodiments, but
are for explanation and understanding only.
[0010] FIG. 1 is a general view a conventional double sided wafer
processing system.
[0011] FIG. 2 illustrates an exemplary processing system.
[0012] FIG. 3 illustrates a side view of one embodiment of a brush
box and a portion of the brush box containment apparatus.
[0013] FIG. 4A illustrates a perspective view of one embodiment of
the upper brush assembly of the present invention.
[0014] FIG. 4B illustrates a perspective view of one embodiment of
the lower brush assembly of the present invention.
[0015] FIG. 4C illustrates one embodiment of a rotating arm and its
coupling for attachment to a drive.
[0016] FIGS. 5A-5D illustrate a top views of embodiments of the
upper and lower brush assemblies and section views of the upper and
lower brush assemblies respectively.
[0017] FIG. 6 illustrates a side section view of a pad and roller
combination used for processing the edge of a substrate. FIGS.
7A-7C illustrate various pressure application schemes for
processing the edge of a substrate using non-uniformly distributed
pressure with upper and/or lower brush assemblies.
DETAILED DESCRIPTION
[0018] A system for processing the edge/bevel of semiconductor
wafers is described. In the following description, numerous details
are set forth, such as component materials, speeds, pressures etc.
It will be apparent, however, to one skilled in the art, that the
present invention may be practiced without these specific details.
In other instances, well-known structures and devices are shown in
block diagram form, rather than in detail, in order to avoid
obscuring the present invention.
[0019] Overview of the Present Invention
[0020] The present invention provides a method and apparatus for
processing semiconductor wafers. In one embodiment, the system
includes two scrubbing stations. In one embodiment, the scrubbing
stations perform brush scrubbing of the opposite sides of the wafer
simultaneously.
[0021] In one embodiment, each scrubbing station includes one or
more scrubbing elements, at least one of which is positioned by a
second assembly, where portions of the first and second assemblies
are substantially the same. The scrubbing elements are processing
elements that may comprise pads and/or brushes.
[0022] In one embodiment, at least one of the brush scrubbing
stations includes an assembly configurable to apply a processing
element, which may be a brush or a pad media, to a semiconductor
wafer at various pressures. These various pressures may include a
first set of pressures sufficient to scrub a semiconductor wafer.
Additionally, pressure applied can be different on opposite sides
of the brush or pad. In one embodiment, non-uniform pressure is
applied to the wafer to process (e.g., scrub, clean, buff) the
edge/bevel of the wafer.
[0023] In one embodiment, a processing box includes a brush
assembly and a positioning assembly. The brush assembly may
comprise a pair of pads and/or brushes for cleaning wafers and a
mechanism to control and drive the brushes and/or pads. The
positioning assembly may be used to position various components and
devices in a processing system. In one embodiment, such components
include wafer handling and manipulation devices, such as rollers,
wheels, guides, one or more robots. For example, see U.S. patent.
application Ser. No. 087/05,115, entitled "A Containment
Apparatus," filed Aug. 29, 1996; U.S. patent application Ser. No.
08/705,162, entitled "A Roller Positioning Apparatus," filed Aug.
29, 1996; and U.S. patent application Ser. No. 08/705,161, entitled
"A Brush Assembly Apparatus," filed Aug. 29, 1996, all assigned to
the corporate assignee of the present invention and incorporated
herein by reference.
[0024] The processing box may be incorporated into a wafer
processing system having multiple processing stations. For
instance, the wafer processing system may have one or more stations
for cleaning (e.g., scrubbing) and/or buffing substrates. Note that
although embodiments may be described in terms of cleaning by
performing brush scrubbing of wafers, wafer cleaning techniques
other than scrubbing may be employed in one or more of the
processing stations.
[0025] Although embodiments are described in conjunction with
scrubbing a wafer, it will be appreciated that any similarly
shaped, i.e. generally applied substrate, may be processed.
Further, it will be appreciated that reference to a wafer or
substrate may include a bare or pure semiconductor substrate with
or without doping, a semiconductor substrate with epitaxial layers,
a semiconductor substrate incorporating one or more device layers
at any stage of processing, or other types of substrates
incorporating one or more semiconductor layers such as substrates
having semiconductor-on-insulator (SOI) devices or substrates for
processing other apparatuses and devices, such as flat panel
displays, hard disks, multi-chip modules, etc.
[0026] In one embodiment, pressure applied at one end of the brush
assembly is 2-4 times greater than at the opposite end of the brush
assembly. The increased pressure at one end of the brush/pad
assembly causes the wafer to rotate more slowly or to rotate in the
opposite direction as compared to rotation caused by the roller(s)
alone. Slowed rotation causes a difference in tangential velocity
between the roller(s) and the wafer edge/bevel that causes pads in
the roller(s) to process (e.g., clean) the edge/bevel of the wafer.
In one embodiment, the opposite direction of rotation causes the
wafer to rotate counter to roller(s) that causes pads in the
roller(s) to process the edge/bevel of the wafer.
[0027] An Exemplary System
[0028] FIG. 2 illustrates a conceptual view of one embodiment of a
double sided wafer processing system. The system includes multiple
stations, each of which logically represents one or more steps in
the wafer buffing and cleaning process. These stations can also
include the hardware and software that completes one of the steps
in the process. The process includes the steps executed by the
system on the wafers.
[0029] In one embodiment, the system can process multiple wafers
simultaneously; one or more wafers are being processed in each of
the stations at a point in time (pipelined processing). In one
embodiment, the system provides an acidic (low pH) cleaning process
for wafers. The cleaning process may comprise a hydrofluoric (HF)
or standard clean 1 (SC2) cleaning process. In order to withstand
the corrosive effects of the acid, plastic components in the system
may be comprised of such materials such as PET, acetal (DELRIN),
teflon, polypropylene (polypro), polyuerethane, etc., and metal
components may comprise stainless steel, such as Hasteiloy C276.
Note that the system may apply other cleaning or buffing
processes.
[0030] It should be noted that the brush assembly operates on a
processing box that may facilitate the use of dionized (DI) water
in the process. In one embodiment, the processing box is fully
capable of running different chemistries. For instance,
hydrofluoric (HF) acid may be run in the processing box.
Importantly, the processing box provides the ability to apply
pressure similar to a polisher and still process all the chemicals
for cleaning.
[0031] Dirty wafers are loaded at one end of the scrubber; clean
wafers are unloaded from the other end of the scrubber. In load
station 110 (also known as the input station), the operator loads a
cassette 180 into the system. Cassette 180 contains a number of
dirty wafers that are moved from load station 110 to station 120 on
transport belt 115. Transport belt 115 is moved by DC motor 193.
Wafer 101 represents a dirty wafer being automatically removed from
cassette 180 and placed on transport belt 115.
[0032] As part of a cleaning process, in station 120, dirty wafer
102 is brushed and sprayed (water jets not shown in FIG. 2) to
remove some of the particles from dirty wafer 102. Brushes 121
scrub both sides of dirty wafer 102 simultaneously. The position of
the top brush is controlled by a stepper motor (not shown in FIG.
2). Roller 190 rotates dirty wafer 102. The height of the top brush
is controlled by a stepper motor (not shown but in greater detail
below). Roller 190 rotates wafer 102. Multiple rollers can be
included in station 120.
[0033] In one embodiment, the edge/bevel areas of a wafer are
cleaned using the roller 190. Wafer 102 is cleaned by applying
equal amounts of pressure to both ends of the brush/pad assembly
for a predetermined period of time. Pressure is applied unequally
to the ends of the brush/pad assembly such that the rotation of
wafer 102 is slowed or its rotation is reversed (i.e., in the
opposite direction of the direction that roller 190 would otherwise
cause wafer 102 to rotate). The slowed or counter rotation combined
with pads in roller 190 (described in greater detail below) clean
the edges of wafer 102. Edge cleaning by applying unequal pressure
with the brush/pad assembly can be performed before or after top
and bottom wafer cleaning by applying equal pressure to the
brush/pad assembly.
[0034] The once brushed wafers are then moved to station 130 by
transport belt 116, controlled by a second DC motor (not shown in
FIG. 2). In station 130, once brushed wafer 103 is brushed and
sprayed (water jets not shown in FIG. 2) to remove additional
particles from wafer 103. Brushes 131 scrub both sides of the once
brushed wafer 103. The position of the top brush of brushes 131 are
controlled by stepper motor 191. Edge cleaning can be performed at
station 130, in addition to or in place of, edge cleaning at
station 120. Edge cleaning at station 130 may require addition of
one or more rollers to station 130.
[0035] Spin & dry station 140 rinses, spins, and dries wafers,
such as wafer 103. Wafer 104 represents a wafer being processed in
spin & dry station 140. At station 140, the wafer has been
cleaned. Certain wafer types must be kept wet during the load
station 110, station 120, and station 130. Only after being brushed
and rinsed can these wafers be spun and dried. The spun and dried
wafer is then moved to output station 150.
[0036] At output station 150, the clean wafer is put into cassette
181. Wafer 105 represents a clean wafer being put into cassette
181. Cassette 181, when full of clean wafers, can then be removed
by the operator, which completes the cleaning process.
[0037] Control system housing 170 houses a number of components of
the control system for the system. Control system housing 170
includes cage 171 having board 172. Board 172 provides overall
control for the system. Board 172 typically includes one or more
processors and memory implemented in one or more physical packages.
Cage 171 may provide support for board 172 and other boards in cage
171 (e.g., sensor input boards, a video card for operator display
160, a board for communicating signals from the host board 172 to
the rest of the control system).
[0038] FIG. 3 illustrates a side view of one embodiment of brush
box 105. Brush box 105 is shown to contain brush assembly 210
comprising scrubbing brushes 211 and 212 for scrubbing both sides
of a wafer at the same time and brush drive mechanism 214 with
brush pivot point 213, as are described in more detail below. Brush
drive mechanism 214 is coupled to drive brush 211 and is also
described in greater detail below.
[0039] FIGS. 4A and 4B illustrate perspective views of the upper
brush assembly and the lower brush assembly respectively of a brush
assembly. FIG. 4C illustrates one portion of one embodiment of a
rotating arm and its coupling to a drive. FIGS. 5A-5D illustrate a
top view of the upper and lower brush assemblies and a section view
of the upper and lower brush assemblies respectively. For more
information on one embodiment of a brush box and a brush assembly,
see U.S. Pat. No. 5,806,126, entitled, "Method and Apparatus
Chemical Delivery Through the Brush," issued Sep. 15, 1998,
assigned to the corporate assignee of the present invention, and
incorporated herein by reference. It should be noted that the
actual brushes themselves (apart from the drive mechanism) are
well-known in the art. Note that FIGS. 4A and 4B and FIGS. 5A-5D
are described in terms of brushes, however, the assemblies may be
configured for pads for scrubbing or other processing (e.g.,
buffing). Each of these brushes includes multiple protrusions (not
shown) to facilitate the cleaning of wafers.
[0040] In one embodiment, the upper and lower brushes provide fluid
to the core of the brush to be dispersed to the outside of the
brush through the brush surface. Such brushes and fluid delivery
system will not be described in detail herein. For descriptions on
exemplary brushes and more information on the system for fluid
delivery through the brush, see U.S. Pat. No. 5,806,126, entitled,
"Method and Apparatus for Chemical Delivery Through the Brush,"
issued Sep. 15, 1998, assigned to the corporate assignee of the
present invention and incorporated by reference herein.
[0041] In FIGS. 4A and 4B and FIGS. 5A-5D, each of the brush cores
may be replaced by a pad roller assembly or other suitable material
for buffing of the wafer. In this manner, each of the brush
assemblies may be configured as a buffing assembly to buff one or
more sides of the wafer. It should be noted that in this case the
buffing pad roller assembly, much like the brush, is designed to
disburse fluid from its core to the outside of the pad through the
pad surface.
[0042] The materials used for the brushes may comprise PVA or
polyurethane type of material. The top and bottom brushes may be
the same or different materials. In another embodiment, the
material comprises a combination of PVA or polyurethane type
material with a polishing pad on top. The shape of the brush may be
in the form of a round cylinder and in such a case may be a flat
PVA brush. In another embodiment, a flat PVA brush may be wrapped
with a soft polishing pad.
[0043] In one embodiment, the contact area that occurs between the
brushes and the wafer is controlled by selecting materials of
different technologies. The position of the brush core and the
compressibility of the material determine the contact area and
pressure that are applied. Therefore, by selecting a brush or pad
with certain compressibility with the same brush core, the contact
area may be changed.
[0044] The brush positioning apparatus that causes brush core 301
to be applied to the wafer may be controlled to apply brush core
301 to the wafer at various pressures. In other words, the brushes
are physically attached so that they may be physically moved
(pushed down). By pushing up on the end of rotating arms 331 and
302 with greater force from the stepper motor, brush core 301 is
applied to the wafer with increased pressure.
[0045] The microsteps produce greater brush movement than in the
prior art. As illustrated, the amount of pressure that may be
applied is greater than that of the prior art, even4-5 times
greater. The increased pressure applied allows removal of embedded
particles on the wafer during scrubbing. Using the HF-based
process, in conjunction with the increased pressure, provides an
overall better cleaning process.
[0046] To clean the edges of the wafer, the stepper motor connected
to one of rotating arms 331 and 302 applies greater pressure than
the stepper motor connected to the opposite rotating arm. For
example, one of the stepping motors can be configured to raise the
corresponding rotating arm 1-3 mm more than the opposite rotating
arm, or to apply sufficient pressure to cause the wafer to rotate
in the opposite direction than the wafer would rotate if driven by
a roller.
[0047] In an alternative embodiment, lower brush assembly 350
includes rotating arms to allow lower brush assembly to be moved
and/or pressure to be applied to the bottom of the wafer. In such
embodiment, pressure can be applied unevenly as discussed above
with respect to upper brush assembly 300. Thus, pressure can be
applied from the top, from the bottom, or some combination
thereof.
[0048] FIG. 6 illustrates one embodiment of a roller with a pad. An
exemplary wafer 602 is also shown. In one embodiment, pad 601
comprises a SubaIV pad manufactured by Rodel of Newark, Del. Other
pads such as IC1000, suba500, politex (all manufactured by Rodel)
can also be used.
[0049] Note that pad 601 can be of different thickness and surface
texture to increase and/or even maximize the cleaning action. The
pad may also be shaped to remove particles only from an edge, where
for instance, the wafer is without bevel areas that cannot be
cleaned by the top and bottom brushes.
[0050] For more information, see U.S. Pat. No.5,861,066, entitled
"Method and Apparatus For Cleaning Edges of Contaminated
Substrates", issued Jan. 19, 1999, assigned to the corporate
assignee of the present invention and incorporated herein by
reference.
[0051] FIGS. 7A-7C illustrate various pressure application schemes
for cleaning the edge of a substrate using unequally distributed
pressure with upper and/or lower brush assemblies. FIGS. 7A-7C
illustrate three of many embodiments for applying non-uniform
pressure to a wafer with upper and lower brush assemblies. The
present invention is not strictly limited to the three embodiments
illustrated.
[0052] FIG. 7A illustrates one embodiment of applying non-uniform
pressure to wafer 710 with upper brush assembly 720. Referring to
FIG. 7A, lower brush assembly 715 provides support for wafer 710.
In one embodiment both upper brush assembly 720 and lower brush
assembly 715 have brushes to provide double sided wafer
processing.
[0053] Wafer 710 is rotated by roller 705. In one embodiment,
roller 705 includes a pad for cleaning the edges of wafer 710 in a
manner similar to the roller of FIG. 6. Alternatively, roller 705
does not have a pad for cleaning edges and upper brush assembly 720
cleans the edges of wafer 710. While the embodiment of FIG. 7A is
described in terms of a single roller, multiple rollers can be
used, with one or more of the rollers having a pad for cleaning the
edges of wafer 710.
[0054] Pressure vectors 730 and 735 indicate pressure applied by
upper brush assembly 720. The length of vectors 730 and 735
indicate the magnitude of pressure applied at the respective ends
of upper brush assembly 720. In one embodiment, pressure vector 735
is twice pressure vector 730 indicating that the pressure applied
at one end of upper brush assembly 720 is double the pressure
applied at the opposite end of upper brush assembly 720.
[0055] In an alternative embodiment, pressure vector 735 is four
times greater than pressure 730 (not shown in FIG. 7A), which
corresponds to the pressure at one end of upper brush assembly 720
being four times greater than the pressure applied at the opposite
end of upper brush assembly 720. Of course, other pressure ratios
between the ends of upper brush assembly 720 can also be used.
[0056] In one embodiment, pressure is applied with a stepper motor
raising and lowering rotating arms on upper brush assembly 720 in a
manner such as with the embodiments of FIGS. 4A and 4C. For
example, a stepper motor connected to one end of upper brush
assembly 720 can raise a connected rotating arm to a first
predetermined position thereby applying a first pressure to wafer
710. A stepper motor connected to the opposite end of upper brush
assembly 720 moves upper brush assembly 720 to a second
predetermined position thereby applying a second pressure to wafer
710 and providing non-uniform pressure across the surface of wafer
710.
[0057] In one embodiment, the pressure applied by upper brush
assembly 720 causes wafer 710 to rotate in the reverse direction as
compared to rotation with roller 705 alone. The greater pressure
indicated by pressure vector 735 is sufficient to grip wafer 710
and cause the rotation of wafer 710 to reverse. The reverse
rotation causes the edges of wafer 710 to be cleaned by the pad of
roller 705 (not shown in FIG. 7A).
[0058] In an alternative embodiment, the pressure indicated by
pressure vector 735 causes the rotation of wafer 710 to slow as
compared to rotation caused by roller 705 alone. The difference in
tangential velocity between wafer 710 and roller 705 causes the
edges of wafer 710 to be cleaned by the pad of roller 705.
[0059] FIG. 7B illustrates one embodiment of applying non-uniform
pressure to wafer 740 with both upper brush assembly 745 and lower
brush assembly 750. In such an embodiment, lower brush assembly 750
provides support for wafer 740 as well as applying pressure to
wafer 740. Wafer 740 is rotated by roller 765, which can include a
pad (not shown in FIG. 7B) for cleaning the edges of wafer 740.
[0060] In one embodiment, the amount of pressure applied at one end
of upper brush assembly 745 and at the opposite end of lower brush
assembly 750 is equal, as indicated by pressure vectors 755 and
760. Of course, the amount of pressure applied by upper brush
assembly 745 is not required to be equal to the amount of pressure
applied by lower brush assembly 750.
[0061] In order to apply pressure with both upper brush assembly
745 and lower brush assembly 750, both brush assemblies are movable
such as the brush assembly of FIG. 4A. In one embodiment, upper
brush assembly 745 is a brush assembly similar to the brush
assembly of FIG. 4A and lower brush assembly 750 has only a single
rotating arm to apply pressure to the lower surface of wafer
740.
[0062] The rotating arms of upper brush assembly 745 and lower
brush assembly 750 are connected to stepper motors that provide
movement of the rotating arms and thereby apply pressure to wafer
740.
[0063] FIG. 7C illustrates one embodiment for applying non-uniform
pressure to wafer 770 with lower brush assembly 780. Wafer 770 is
rotated by roller 775, which can include a pad (not shown in FIG.
7C) for cleaning the edges of wafer 770.
[0064] In one embodiment, upper brush assembly 785 is fixed and
provides a surface against which lower brush assembly 780 can be
used to apply non uniform pressure to wafer 770. Alternatively,
upper brush assembly 785 can be movable, but provide uniform
pressure across the surface contacting wafer 770.
[0065] In one embodiment, lower brush assembly 780 has two rotating
arms connected to stepper motors to provide pressure against the
lower surface of wafer 770. In one embodiment pressure is applied
as shown by pressure vectors 790 and 795. Any ratio of pressures
between pressure vectors 790 and 795 can be provided.
[0066] Whereas many alterations and modifications of the present
invention will no doubt become apparent to a person of ordinary
skill in the art after having read the foregoing description, it is
to be understood that the various embodiments shown and described
by way of illustration are in no way intended to be considered
limiting. Therefore, references to details of various embodiments
are not intended to limit the scope of the claims which in
themselves recite only those features regarded as essential to the
invention.
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