U.S. patent application number 13/694998 was filed with the patent office on 2014-07-24 for method and apparatus for cleaning grinding work chuck using a scraper.
The applicant listed for this patent is Malcolm K. Roe, Larry A. Spiegel, Michael Vogtmann. Invention is credited to Malcolm K. Roe, Larry A. Spiegel, Michael Vogtmann.
Application Number | 20140202491 13/694998 |
Document ID | / |
Family ID | 51206756 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140202491 |
Kind Code |
A1 |
Vogtmann; Michael ; et
al. |
July 24, 2014 |
Method and apparatus for cleaning grinding work chuck using a
scraper
Abstract
A scraper assembly for removing debris deposited on the surface
of a porous work chuck during a wafer grinding process.
Inventors: |
Vogtmann; Michael; (Paso
Robles, CA) ; Spiegel; Larry A.; (Atascadero, CA)
; Roe; Malcolm K.; (Creston, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vogtmann; Michael
Spiegel; Larry A.
Roe; Malcolm K. |
Paso Robles
Atascadero
Creston |
CA
CA
CA |
US
US
US |
|
|
Family ID: |
51206756 |
Appl. No.: |
13/694998 |
Filed: |
January 23, 2013 |
Current U.S.
Class: |
134/6 ;
451/67 |
Current CPC
Class: |
B24B 7/228 20130101;
B24B 55/00 20130101 |
Class at
Publication: |
134/6 ;
451/67 |
International
Class: |
B24B 55/00 20060101
B24B055/00 |
Claims
1. A method for cleaning particles from the surface of a circular
cylinder shaped and rotatable work chuck used in a grind apparatus
comprising the steps of: providing a work chuck having first and
second surfaces, said work chuck being operable in conjunction with
said grind apparatus; positioning a scraper device adjacent said
first surface of said work chuck; and activating said scraper
device whereby said particles are substantially removed from the
first surface of said work chuck.
2. The method of claim 1 wherein said work chuck has an edge
portion along its perimeter.
3. The method of claim 2 wherein said scraper device is positioned
above said edge portion of said work chuck.
4. A grind apparatus for grinding a surface of a workpiece
comprising: a grind wheel; a porous work chuck having top and
bottom surfaces; means for rotating said work chuck and said grind
wheel; a scraper device positioned adjacent to said top surface of
said work chuck; means for moving said scraper device across the
top surface of said work chuck; and means for energizing said
scraper device whereby particles on the top surface of said work
chuck remaining after grinding of said workpiece are substantially
removed.
Description
RELATED APPLICATIONS
[0001] This Application is based on Provisional Application No.
61/632,262 filed on Jan. 23, 2012.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
cleaning the porous ceramic grind work chuck used in semiconductor
wafer grinding machines.
[0004] 2. Background of the Invention
[0005] U.S. Pat. No. 7,118,446, issued to Thomas A. Walsh and
Salman Kassir and assigned to the assignee of the present invention
exemplifies the status of prior art grinder apparatus technology. A
chuck is provided in the apparatus to hold the work piece in place
so that the work piece does not slip or otherwise move while being
shaped by a grind wheel.
[0006] The chuck is porous i.e. holes are drilled therethrough it
or otherwise comprises a porous material; a partial vacuum being
provided below the chuck to hold the work piece in place. Coolant
is pumped directly onto an area of contact between a grind wheel
and the workpiece surface, providing cooling and cleaning of grind
debris (swarf) from the surface of the workpiece.
[0007] During the grinding process, vacuum is applied through the
porous portion of the work chuck to hold the wafer. If there is a
particle (from the work chuck or from the incoming wafer) between
the bottom of the wafer and the top of the work chuck, a crack in
the wafer will be produced. This type of crack is called a "star
crack" and propagating cracks originate at the particle.
[0008] Additionally, the wafers themselves may introduce particles
onto the work chuck. The particles can lead to star cracks and/or
non-uniformities in the grind.
[0009] What is thus desired is to provide a work chuck cleaning
particle removal procedure wherein the cleaning can be done either
automatically or manually.
SUMMARY OF THE INVENTION
[0010] The present invention provides method and apparatus for
removing particles from the surface of a chuck used to hold a
workpiece, such as a wafer, in position during grinding, the
process being accomplished manually or automatically. In
particular, a scraper assembly is positioned within a wafer grinder
apparatus adjacent the edge of the work chuck. The assembly
comprises a razor mechanism positioned on the face surface of a
gimbal block, a plurality of brush members being positioned
adjacent to the razor. The assembly further comprises a fluid
source which, when activated, directs fluid to the chuck surface
which in turn causes debris to be removed from work chuck surface.
The razor mechanism is then moved from the center of the work chuck
to the edge to remove any particles from the chuck surface. A
source of sonic energy may be positioned on the assembly, or in the
fluid path, the sonic energy loosening particles that may be
tightly adhering to the chuck surface.
DESCRIPTION OF THE DRAWINGS
[0011] For a better understanding of the present invention as well
as other objects and further features thereof, reference is made to
the following description which is to be read in conjunction with
the accompanying drawing therein:
[0012] FIGS. 1A and 1B are perspective and plan views,
respectively, of a prior art grinder assembly modified to
incorporate the scraper cleaning system of the present
invention;
[0013] FIG. 2 is a perspective view illustrating the scraper
assembly of the present invention positioned relative to the work
chuck;
[0014] FIG. 3 is a partial perspective, sectional view illustrating
the scraper assembly of the present invention;
[0015] FIG. 4 is similar to FIG. 3 showing the rotation of the
scraper assembly about a gimbal point, the arrow showing the
direction of motion of the work chuck;
[0016] FIG. 5 is a perspective view of the scraper assembly of
FIGS. 2, 3 and 4 illustrating the face of the gimbal block with the
razor and brushes shown;
[0017] FIG. 6 illustrates, in simplified form, how the present
invention can be incorporated with the prior art grinding
apparatus;
[0018] FIGS. 7(a)-7(c) illustrate various configurations for the
scraper blade; and
[0019] FIG. 8 illustrates a preferred mounting assembly to hold the
scrapper blade while cleaning the chuck surface.
DESCRIPTION OF THE INVENTION
[0020] In order to put the present invention in proper perspective,
FIGS. 1A and 1B illustrate a prior art grinder assembly, such as
that disclosed in the '446 patent, modified to incorporate the
cleaner assembly of the present invention.
[0021] Referring to FIGS. 1A and 1B, shown are perspective and plan
views respectively of the compact grinder assembly 100 disclosed in
the '446 patent. Shown is a grind spindle 102, a spindle support
column 104, a work spindle 106, a cabinet 108, a splash pan 110, a
work chuck 112, a thickness probe 111, a ball screw assembly 114, a
bed portion 118, rails 120 and a ball screw 122.
[0022] The grind spindle 102 is coupled with the spindle support
column 104, and the spindle support column 104 is engaged with the
rails 120 and the ball screw 122. The cabinet 108 supports the
rails 120, balls screw 122, the work spindle 106 and the splash pan
110. The thickness probe 111 is coupled with the work spindle 106
and is shown positioned above the work chuck 112.
[0023] The grind spindle 102 is moved along a vertical axis by the
ball screw assembly 114 and includes at least one grinding wheel
(not shown) in order to shape a work piece, for example,
semiconductor wafers.
[0024] The work chuck 112 holds the work piece in place so that the
work piece does not slip while rotating and being shaped by a
grinding wheel of the grind spindle 102. For example, the work
chuck 112 is porous, e.g. it has holes drilled through it or
otherwise comprises a porous material, and a partial vacuum is
provided by a device (not shown) positioned below the work chuck
112 to hold the work piece in place.
[0025] The spindle support column 104, supports the grind spindle
102, and is moveably engaged with the rails 120, bed 118 and ball
screw 122, to translate back and forth in a horizontal direction.
Specifically, the spindle support column 104, and the grind spindle
102 move with respect to the cabinet 108, the work spindle 106, and
thus a surface of a stationary work piece attached on the work
chuck 112.
[0026] The ability to translate the grind spindle assembly 102
allows shaping of a work piece to be achieved on both a face and an
edge of the work piece with a single machine. Specifically, a
grinding wheel of the grind spindle 102 is first positioned over an
edge of the work piece and then moved into contact with the edge of
the work piece until the edge is shaped as desired. The grind
spindle 102 is then raised vertically above the work piece,
translated horizontally over a face of the work piece so the
grinding wheel is positioned over the face of the work piece, and
then the grinding wheel is then placed in contact with the face of
the work piece by lowering the grind spindle 102 until the grinding
wheel is in contact with a portion of the face of the work piece,
typically contact with the center of the wafer mounted on work
chuck.
[0027] Referring to FIG. 2, the work chuck scraper assembly 200 of
the present invention is positioned above the top surface of work
chuck 112. The backflush operation that is part of the process
disclosed in the '446 patent cooperatively operates with assembly
200, the former forcing trapped particles from the bottom of the
work chuck whereas assembly 200 removes trapped particles from the
top surface of the work chuck 112. Particles may be trapped in
pores anywhere on the work chuck surface. The scraper devices may
be manipulated across the entire work chuck face as the work chuck
rotates to clean the entire wafer surface.
[0028] FIG. 3 shows details of one embodiment of the structure of
assembly 200 (work chuck 112 is supported on member 113).
Specifically, a scraper mechanism 210, illustrated as a razor in
the embodiment illustrated, is mounted within stationary (relative
to gimbal block 206) housing 204 forming a spherical gimbaling
surface. A port (not shown) may also be mounted within housing 204,
water or other liquid being supplied to the port to aid in carrying
debris off the top surface of the work chuck. Seal 212 is
positioned around a portion of the circumference of housing 204 as
illustrated and a gimbal block 206 with a matching spherical
surface is cooperated with and is secured within housing 204. A set
screw 208 functions to secure the scraper into the gimbal block.
The angle of the scraper to the work chuck is defined by the angle
machined into the gimbal block. The set screw can also be used to
allow setting of the scraper depth. A plurality of brush bristles
214 project from the surface 220 of gimbal block 206. Although
razor 210 is illustrated positioned at the perimeter of face
portion 220, the razor may be positioned at the center surrounded
by the brush bristles 214. As noted hereinabove, an alternate
technique using liquid to cause assembly 200 to hover above the
work chuck surface can be utilized, this technique being used in
conjunction with the bristles 214 which provide stability and
spacing. Although the preferred operating position of razor 210 is
as shown in FIG. 2, the razor can be moved anywhere on the work
chuck face as long s orientation of the blade to the rotation
direction is maintained. Further, razor 210 is designed to operate
on different materials that comprise the work chuck surface.
[0029] Referring to FIG. 4, as work chuck 112 rotates under
assembly 200 as illustrated by motion arrow B, a side force,
illustrated by arrow A, is induced on the assembly. In particular,
the side force is generated by the relative motion of the chuck
surface 202 under the assembly or by the movement of the indexing
table (not shown) that supports the chuck spindle mechanism. In
addition, the side force could also be caused by the scraping
device itself. Since the projected gimbal point 215, or center of
rotation, is below the top surface of work chuck 202, the leading
edge of assembly 200 will not impact surface 201 due to the
direction of the resulting moment. In particular, the projected
gimbal mechanism moment prevents the leading edge of assembly 200
from digging into the top surface of work chuck 202. Since the
projected gimbal point is below the surface of the work chuck, side
force A (in essence, caused by friction between the moving parts)
is exerted on assembly 200, the leading edge will rotate upward
instead of downward into the surface of work chuck 202. A
rotational driving mechanism 213 comprising slot and drive pin 217,
ensures that the blade is pointed in the correct direction.
[0030] The operation of the assembly 200 is shown in more detail in
FIG. 5. As noted above, in addition to brushes (bristles) 214,
fluid flow may be emitted through openings 232 and impinge on the
surface of work chuck 112 causing assembly 200 to hover above the
surface. The work chuck back flush could also be used to hover
assembly 200 above the surface of the work chuck.
[0031] Work chuck 112 then is then rotated and the tip of the razor
210 (adjusted so that the tip engages its surface) causing the
projecting debris particles to be removed.
[0032] Assembly 200 may be activated manually for most
applications. However, if cleaning is required for every work
piece, a control signal can be provided from the system control
software to actuate the scraper assembly 200 before grinding each
wafer (or every Nth wafer).
[0033] The operative cycle of assembly 200 is as follows:
[0034] After the wafer is removed from the top surface of work
chuck 202, the work chuck blow-off (air) and back flush fluid, such
as distilled water is turned on to purge the majority of the
particulates that were sucked into the porous work chuck material
during the grinding cycle. During this process, the work chuck is
spinned causing the particles to be removed from its edge. After
the majority of particulates now have been removed, scraper
assembly 200 is then actuated and placed on the work chuck. Most of
the remaining particulates will be trapped where the perimeter of
the wafer made contact with the porous section of work chuck 202.
Scraper assembly 200 typically starts in the center of the work
chuck 202 and moves radially outward until it reaches the location
where the most of the particulates are trapped. The scraper
assembly 200 stays in this position as work chuck 202 slowly
rotates. After the user defined scraper time has been reached, the
scraper assembly will lift and rotate back to the center home
position or away from the work chuck. Note that assembly 200 never
(other than the tip of razor 210 touches the surface of the work
chuck because of brushes 214, and/or if required, a layer of water.
Note that the scraper device itself may also be rotated although
this is not the preferred technique.
[0035] FIG. 6 is a simplified diagram illustrating how the scraper
assembly 200 of the present invention is typically coupled to the
grinder apparatus shown in FIGS. 1A and 1B. In particular, housing
400 is secured to arm 402, of the grinder tool via mounting screws
404 and 406. Within housing 400 is a spring loaded actuator 408
coupled to blade 410. Work chuck spindle 412 rotates the work chuck
in a conventional manner. A bearing or bushing (not shown) is
coupled between actuator 408 and special blade 410 to resist
lateral motion but allow up/down movement. Alternately, a motor
could be used to drive blade 410.
[0036] FIG. 7(a) illustrates two possible alternate shapes for the
blade 410, a flat blade 416 and a cone shaped blade 418. FIG. 7(b)
shows flat blade 416 with a brush support 420 and FIG. 7(c)
illustrates a curved blade 422.
[0037] FIG. 8 illustrates an alternative device 500 to mount
scraper blade 502. Spring 504 provides the force to hold blade 502
against the surface of the work chuck as it rotates. The blade 502
is designed to cover the center to edge of the entire work
chuck.
[0038] While the invention has been described with reference to its
preferred embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the true
spirit and scope of the invention. In addition, many modifications
may be made to adapt a particular situation or material to the
teachings of the invention without departing from its essential
teachings.
* * * * *