U.S. patent application number 10/981231 was filed with the patent office on 2005-05-26 for ceramic end effector for micro circuit manufacturing.
This patent application is currently assigned to Axcelis Technologies, Inc.. Invention is credited to Baumann, Paul W., Deak, Mihaly IV, Pharand, Michel, Polner, Donald N..
Application Number | 20050110292 10/981231 |
Document ID | / |
Family ID | 46303215 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050110292 |
Kind Code |
A1 |
Baumann, Paul W. ; et
al. |
May 26, 2005 |
Ceramic end effector for micro circuit manufacturing
Abstract
An end effector for installation on a robotic arm for
transporting a plurality of semiconductor wafers from one location
to another features a ceramic end effector body portion that
includes a plurality of wafer engaging fingers that each feature
wafer support pads. The wafer support pads are adapted to support a
semiconductor wafer surface, and at least one of the support pads
has a vacuum orifice. The pads are replaceable and/or removable in
case of damage or contamination. The support pads are attached to
the body in such a way as to allow differential thermal expansion
so as to prevent introduction of stress into the components.
Typically, a wire spring is employed to secure the pad to the end
effector. The body portion features an interior vacuum passageway
having a first end that is adapted to connect to a vacuum source
and a second end that terminates at the vacuum orifices such that a
reduced gas pressure at the first end causes a vacuum to be exerted
at the vacuum orifices. The interior passageway is formed from a
groove in the end effector body portion and an end effector
backplate that is sealingly connected to the end effector body
portion to completely cover the groove from the first end to the
second end. The ceramic body portion can be made of alumina or
silicon carbide.
Inventors: |
Baumann, Paul W.;
(Georgetown, MA) ; Deak, Mihaly IV; (Leander,
TX) ; Pharand, Michel; (Chelmsford, MA) ;
Polner, Donald N.; (Marblehead, MA) |
Correspondence
Address: |
WATTS HOFFMANN CO., L.P.A.
PO Box 99839
Cleveland
OH
44199-0839
US
|
Assignee: |
Axcelis Technologies, Inc.
|
Family ID: |
46303215 |
Appl. No.: |
10/981231 |
Filed: |
November 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10981231 |
Nov 4, 2004 |
|
|
|
10305731 |
Nov 26, 2002 |
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Current U.S.
Class: |
294/188 |
Current CPC
Class: |
B25J 9/0012 20130101;
H01L 21/6838 20130101; B25J 15/0616 20130101 |
Class at
Publication: |
294/064.1 |
International
Class: |
B65H 003/08 |
Claims
We claim:
1. For use in the processing of semiconductor wafers, an end
effector for installation on a robotic arm for transporting a
plurality of semiconductor wafers from one location to another, the
end effector comprising: a ceramic end effector; a plurality of
removable wafer support pads disposed at a distal end of said end
effector said support pads being adapted to support a semiconductor
wafer surface, wherein at least one of the support pads comprises a
vacuum orifice in communication with a vacuum source for exerting a
vacuum on the wafer surface; and a retaining structure for
removably securing the removable support pads to the end
effector.
2. The end effector of claim 1 wherein said end effector body
includes an interior vacuum passageway having a first end that is
adapted to connect to a vacuum source and a second end that
terminates at a vacuum aperture, said aperture communicating with
the support pad vacuum orifice such that a reduced gas pressure at
the first end causes a vacuum to be exerted at the vacuum orifice
of the support pad.
3. The end effector of claim 2 wherein the interior passageway is
formed from a groove in the end effector body portion and an end
effector backplate that is sealingly connected to the end effector
body portion to completely cover the groove from the first end to
the second end.
4. The end effector of claim 1 wherein the ceramic body is made of
alumina.
5. The end effector of claim 1 wherein the ceramic body is made of
silicon carbide.
6. The end effector of claim 1 wherein the end effector body
comprises a plurality of wafer engaging fingers at the distal
end.
7. The end effector of claim 6 wherein the wafer support pads are
disposed at an axial end of the wafer engaging fingers.
8. The end effector of claim 6 comprising three wafer engaging
fingers, two of which comprise wafer support pads that include
vacuum orifices.
9. The end effector of claim 6 wherein at least one of the wafer
engaging fingers includes a cavity which houses a vacuum support
pad.
10. The end effector of claim 1 wherein said retaining structure is
a spring clip, said spring clip extending through a portion of the
body of the wafer engaging finger, into said cavity and making
torsional engagement with the vacuum pad such that said spring clip
secures the pad in the cavity.
11. The end effector of claim 1 wherein the vacuum support orifice
includes a counterbore to enhance a seal between the vacuum pad and
end effector during expansion or contraction of the end effector
components.
12. The end effector of claim 1 wherein the vacuum pad is ground
flat at that portion which engages the end effector to create a
vacuum seal with low leakage.
13. For use in the processing of semiconductor wafers, an end
effector for installation on a robotic arm for transporting at
least one of semiconductor wafers from one location to another, the
end effector comprising: a ceramic end effector body portion
including a plurality of wafer engaging fingers; a plurality of
removable wafer support pads disposed at an axial end of the wafer
engaging fingers, said support pads being adapted to support a
semiconductor wafer surface, wherein at least one of the support
pads comprises a vacuum orifice in communication with a vacuum
source for exerting a vacuum on the wafer surface; and a retaining
structure for removably securing the removable support pads to the
end effector.
14. The end effector of claim 13 wherein the ceramic body is made
of alumina.
15. The end effector of claim 13 wherein the ceramic body is made
of silicon carbide.
16. The end effector of claim 13 wherein at least one of the wafer
engaging fingers includes a cavity which houses a vacuum support
pad.
17. The end effector of claim 13 wherein said retaining structure
is a spring clip, said spring clip extending through a portion of
the body of the wafer engaging finger, into said cavity and making
torsional engagement with the vacuum pad such that said spring clip
secures the pad in the cavity.
18. The end effector of claim 13 wherein the vacuum support orifice
includes a counterbore to enhance a seal between the vacuum pad and
end effector during expansion or contraction of the end effector
components.
19. The end effector of claim 13 comprising three wafer engaging
fingers, two of which comprise wafer support pads that include
vacuum orifices.
20. The end effector of claim 13 wherein at least one of the wafer
engaging fingers includes a cavity which houses the vacuum support
pad.
21. For use in the processing of semiconductor wafers, an end
effector for installation on a robotic arm for transporting at
least one of semiconductor wafers from one location to another, the
end effector comprising: a ceramic end effector body including
three wafer engaging fingers, at least one of which comprise wafer
support pads that include vacuum orifices; a plurality of removable
wafer support pads disposed in a cavity at an axial end of the
wafer engaging fingers, said support pads being adapted to support
a semiconductor wafer surface, wherein at least one of the support
pads comprises a vacuum orifice in communication with a vacuum
source for exerting a vacuum on the wafer surface; and a retaining
structure comprising a spring clip, said spring clip extending
through a portion of the body of the wafer engaging finger, into
said cavity and making torsional engagement with the pad such that
said spring clip secures the pad in the cavity.
22. For use in the processing of semiconductor wafers, an end
effector for installation on a robotic arm for transporting at
least one of semiconductor wafers from one location to another, the
end effector comprising: a ceramic end effector body including an
interior vacuum passageway having a first end that is adapted to
connect to a vacuum source and a second end that terminates at a
first vacuum orifice such that a reduced gas pressure at the first
end causes a vacuum to be exerted at the fist vacuum orifice; a
plurality of removable wafer support pads secured to said end
effector body portion said support pads being adapted to support a
semiconductor wafer surface, wherein at least one of the support
pads comprises a second vacuum orifice in communication with said
first vacuum orifice such that a vacuum is exerted on the wafer
surface; and a retaining structure for securing the removable
support pads to the end effector.
23. A method of securing a semiconductor wafer support pad to an
end effector, said end effector for use in thermal processing of
the semiconductor wafer wherein the end effector is installed on a
robotic arm for transporting at least one of semiconductor wafers
from one location to another, the method comprising the steps of:
placing a plurality of wafer support pads in contact with the end
effector, wherein at least one of said pads including a vacuum
orifice in communication with a vacuum source; and securing the
wafer support pads to the end effector with a retaining
structure.
24. The method of claim 23 wherein the end effector comprises a
plurality of wafer engaging fingers.
25. The end effector of claim 24 wherein the wafer support pads are
disposed at an axial end of the wafer engaging fingers.
26. The method of claim 25 wherein at least one of the wafer
engaging fingers includes a cavity which houses the vacuum support
pad.
27. The method of claim 26 wherein said retaining structure is a
spring clip, said spring clip extending through a portion of the
body of the wafer engaging finger, into said cavity and making
torsional engagement with the pad such that said spring clip
secures the pad in the cavity
Description
RELATED APPLICATION
[0001] The present application is a continuation-in-part
application of U.S. application Ser. No. 10/305,731, filed Nov. 26,
2002 and entitled CERAMIC END EFFECTOR FOR MICRO CIRCUIT
MANUFACTURING.
TECHNICAL FIELD
[0002] The present invention relates generally to semiconductor
wafer processing and more specifically to an end effector for
handling semiconductor wafers during processing.
BACKGROUND OF THE INVENTION
[0003] Thermal processing systems are widely used in various stages
of semiconductor fabrication. Basic thermal processing applications
include chemical deposition, diffusion, oxidation, annealing,
silicidation, nitridation, and solder re-flow processes. Many of
these thermal processes involve extremely high temperatures. For
example, vertical rapid thermal processing (RTP) systems comprise a
vertically oriented processing chamber that is heated by a heat
source such as a resistive heating element or a bank of high
intensity light sources. The heat source is capable of heating the
interior of the processing chamber to temperatures in the range of
450-1400 degrees Centigrade at ramp rates of up to about 50 degree
C./sec.
[0004] Semiconductor thermal processing must be performed in an
environment that is relatively free of contamination. One source of
contamination that is detrimental to thermal processes is metal.
For example, metals such as iron, sodium, and chromium in
concentrations as little as 1.times.e.sup.10 atoms per cubic
centimeter will significantly lower the yield from a wafer. Some
vacuum type end effectors have metal components such as vacuum
lines that make them susceptible to metal contamination within the
processing chamber.
[0005] To maximize throughput and minimize contamination, all of
the operations that occur during thermal processing of
semiconductor wafers are automated. Robotic handlers routinely move
wafers into and out of processing chambers. These handlers often
employ end effectors disposed at the end of a robotic arm to grip
and manipulate the wafer. Key features of end effectors include
reliable gripping and minimal impact on the wafer surface. One type
of end effector features one or more vacuum devices mounted on the
end effector that use suction to grip the wafer and to give a
positive indication that the wafer is positioned properly. Some
existing vacuum type end effectors have plastic components such as
wafer support pads that are not suitable for high temperature
thermal processes because they would melt on contact with the
heated wafer.
SUMMARY OF THE INVENTION
[0006] A ceramic end effector with an interior passage for vacuum
provides relatively low cost, lightweight, and contaminate free
wafer handling for high temperature thermal processing
applications.
[0007] An end effector for installation on a robotic arm for
transporting a plurality of semiconductor wafers from one location
to another is provided that features a ceramic end effector body
portion that includes a plurality of wafer support pads. The wafer
support pads are adapted to support a semiconductor wafer surface,
and at least one of the support pads has a vacuum orifice.
[0008] The support pads are secured to the end effector utilizing a
unique spring which through its action forces the support pad in a
downward direction against the body portion. The spring
additionally forces that pad forward against an angled surface on
the body. The pad is thus forced downward and into contact with the
body at the angled interface as well. The surface of the bottom of
the pad and that of the mating surface of the body are ground to a
high degree of flatness to effect a seal that has very low leakage.
The pad and body in this configuration may expand or contract at
different rates as well as move relative to each other without
affecting the seal or introducing stressed into either component.
The underside of the vacuum pad features a counterbore which when
exposed to negative pressure results in a net downward force
against the end effector body thus improving the effectiveness of
the seal between the pad and the end effector body. The pads are
conveniently removable and/or replaceable in the event of damage or
contamination.
[0009] The body portion features an interior vacuum passageway
having a first end that is adapted to connect to a vacuum source
and a second end that terminates at the vacuum aperture such that a
reduced gas pressure at the first end causes a vacuum to be exerted
at the vacuum aperture. In one embodiment, the interior passageway
is formed from a groove in the end effector body portion and an end
effector backplate that is sealingly connected to the end effector
body portion to completely cover the groove from the first end to
the second end. The ceramic body portion can be made of alumina or
silicon carbide. In an exemplary embodiment, the end effector has
three wafer engaging fingers, two of which have wafer support pads
that include vacuum orifices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an overview drawing of a robot featuring an end
effector constructed according to an embodiment of the present
invention loading an RTP process chamber;
[0011] FIG. 2 is a perspective view of the body portion of an end
effector constructed in accordance with an embodiment of the
present invention;
[0012] FIG. 2A is a bottom view of an end effector showing the
vacuum channels constructed in accordance with an embodiment of the
present invention;
[0013] FIG. 3 is a close-up top view of a vacuum support pad cavity
of the end effector body of FIG. 2 constructed in accordance with
an embodiment of the present invention;
[0014] FIG. 4 is a cross-sectional view of the vacuum support pad
cavity of FIG. 3;
[0015] FIG. 5 is a top view of a non-vacuum support pad cavity of
the end effector body of FIG. 2 constructed in accordance with an
embodiment of the present invention;
[0016] FIG. 6 is a cross-sectional view of the non-vacuum support
pad cavity of FIG. 5;
[0017] FIG. 7 is a close-up top view of a vacuum support pad
mounted in its operating position constructed in accordance with an
embodiment of the present invention;
[0018] FIG. 8 is a cross-sectional view of the vacuum support pad
cavity of FIG. 7;
[0019] FIG. 9 is a close-up top view of a non-vacuum support pad
mounted in its operating position constructed in accordance with an
embodiment of the present invention; and
[0020] FIG. 10 is a cross-sectional view of the non-vacuum support
pad cavity of FIG. 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] FIG. 1 shows an overview of an end effector 20 installed on
a typical wafer handling robot 15 that is loading an RTP machine
30. The end effector 20 grips a wafer 17 and installs it through a
slot 36 into the RTP processing chamber. Upon completion of the
thermal process, the end effector is inserted into the processing
chamber and retrieves the wafer 17 for transport to the next step
in fabrication.
[0022] FIGS. 2-6 show the end effector 20 according to the present
invention in more detail. The end effector 20 includes a body
portion 25 that is made of a ceramic material such as, alumina, or
silicon carbide, but preferably alumina. The body portion 25 is
generally planar in shape and features a robot arm mounting end 19,
and two outer wafer engaging fingers 27 and a center wafer support
finger 29 at an axial end. The outer wafer engaging fingers 27 and
support 29 each have a wafer support pad cavity which houses a
wafer support pad that support the wafer during handling without
damaging the wafer surface. The wafer supporting end of each wafer
engaging finger 27 includes a flared wall portion 27a in the same
plane as the finger 27. This flared wall region 27a encompasses the
vacuum support pad cavity 31. The center wafer supporting finger 29
includes a non-vacuum support pad cavity 81.
[0023] Within the body portion 25, an interior vacuum passageway 37
(shown in phantom in FIG. 2) passes from the robot mounting end 19
to vacuum apertures 34 located on each wafer engaging finger 27.
The vacuum passageway 37 is formed from a groove that is machined
in the surface of the body portion 25 that is opposite the surface
that includes the wafer vacuum support pads 33 (FIGS. 7 and 8). A
backplate 35 (FIG. 2b) is fused to the body portion over the groove
37 to seal the passageway so that vacuum can pass from the robot
mounting end 19 to the vacuum apertures 34. Known vacuum fittings
are located in the robot mounting end 19 to connect the interior
vacuum passageway to an exterior vacuum supply 21. Of course,
exterior vacuum lines (not shown) could be used in conjunction with
or in lieu of the interior vacuum passageways described herein in
accordance with the present invention. The center support 29 does
not include vacuum grooves. The center support 29 does include a
non-vacuum support pad cavity 81 which houses a non-vacuum support
pad 77
[0024] FIGS. 3 and 4 show the details of the vacuum support pad
cavity 31. The vacuum support pad cavity 31 is a substantially
circular cavity, the bottom of which is a flat vacuum sealing
surface 57. The vacuum support pad cavity 31 further includes a
front beveled wall portion 54 which angles into the body of the
support finger 27 and away from a central axis of the vacuum
support pad cavity 31. This makes the opening cavity diameter
smaller than the diameter of the cavity along the vacuum sealing
bottom portion 57. As described, a vacuum passageway 37 runs the
length of the supporting finger 27 and terminates at a vacuum
aperture 34 in the sealing surface 57 of the vacuum support pad
cavity 31. In this configuration, vacuum is supplied to the vacuum
support pad cavity 31 through the vacuum aperture 34.
[0025] Referring now to FIGS. 7 and 8, a vacuum support pad 33 is
secured in the vacuum support pad cavity 31 by a removable
nickel-chromium alloy wire spring 50, typically Inconel wire. The
arrangement of the vacuum support pad 33 and wire 50 permit
differential thermal expansion between the vacuum support pad 33
and the end effector body 27 while maintaining the integrity of the
seal between the vacuum support pad 33 and the base 57. The vacuum
support pads 33, in turn, are consumable and/or replaceable in the
event that they become damaged or contaminated.
[0026] The wire spring 50 extends through a first section of the
flared wall portion 27a in a bore 53a. The bore 53a terminates at
the outer peripheral edge of the vacuum support pad cavity 31 thus
exposing the wire spring 50 to the vacuum support pad cavity 31.
The wire spring 50 further extends across the entire length of the
vacuum support pad cavity 31 into a bore 53b in a second section of
the flared wall portion 27a. The bore 53b extends through the
second section of the flared wall portion 27b providing a path for
the wire spring 50 to extend through and protrude out of the flared
wall portion 27b. The area of the wire spring 50 that is exposed in
the vacuum support pad cavity 31 provides torsional forces on a
vacuum support pad 33 within the vacuum support pad cavity 31. The
torsional forces from the spring 50 are a result of the vacuum
support pad 33 in the vacuum support pad cavity 31 displacing the
wire spring 50 from its natural position within the vacuum support
pad cavity 31. In this arrangement, the wire spring 50 forces the
vacuum support pad 33 forward and downward to make contact the
beveled wall 54 of the vacuum support pad cavity 31.
[0027] FIG. 8 shows the vacuum support pad 33 in its proper
operating position. The vacuum support pad 33 includes top surface
61 having a raised annular wafer engaging surface 63. A vacuum
enhancing chamber is created between the top surface 61 and the
raised annular surface 63 which aids in securing a wafer against
the annular surface 63 during operation and movement of the robotic
arm. At the central axis of the vacuum support pad 33 is a vacuum
orifice 65 which extends completely through the body of the vacuum
support pad 33. The outside perimeter of the vacuum support pad 33
includes a beveled wall 67 which angles away from the central axis
A of the vacuum support pad 33 from the top of the annular surface
63 to the bottom of the vacuum support pad 33. When the vacuum
support pad 33 is positioned in the vacuum support pad cavity 31 as
described above, the wire spring 50 applies a torsional force that
urges the vacuum support pad 33 towards the beveled wall portion 54
of the interior of the vacuum support pad cavity 31. The beveled
wall 67 of the vacuum support pad 33 is caused to come into contact
with the beveled wall 54 of the interior of the vacuum support pad
cavity 31 in manner that locks a portion of the vacuum support pad
33 within the vacuum support pad cavity 31. The wire spring 50
rests on the outer perimeter of the pad including the bevel which
causes the wire spring 50 to further exert a downward force on the
vacuum support pad 33.
[0028] The pad further includes a bottom surface 71 having a
portion of which is raised creating an annular sealing surface 73.
The sealing surface 73 sealingly engages the bottom surface 57 of
the vacuum support pad cavity 31. Both the annular sealing surface
73 of the vacuum support pad 33 and the bottom surface 57 of the
vacuum support pad cavity 31 are ground to a relatively high degree
of flatness to provide a seal with very low leakage. The bottom
surface 71 further includes a counter bore area 75 having the
vacuum orifice 65 generally it's center. During operation, the
vacuum aperture 34 is in fluid communication with the vacuum
orifice 65 of the vacuum support pad 33 such that a vacuum pressure
can be communicated through the vacuum support pad 33 to a wafer
contacting the wafer engaging surface 63. Further, the counter bore
area 75 when exposed to the negative pressure of the vacuum
enhances the net downward force of the vacuum support pad 33
resulting in the annular sealing surface 73 of the vacuum support
pad 33 to sealingly engage with very low leakage the bottom 57
surface of the vacuum support pad cavity 31.
[0029] FIGS. 5 and 6 illustrate the pad holding end of the central
support finger 29. As with the holding end of the wafer engaging
fingers 27, the support finger 29 includes a non-vacuum support pad
cavity 81 which is used to house a non-vacuum support pad 77. The
non-vacuum support cavity 81 further includes the front bevel wall
54 and a flat bottom 61. However, the wafer support finger 29 does
not include vacuum passageways and for this reason, the flat bottom
61 of the vacuum support pad cavity 31 does not include a vacuum
aperture.
[0030] Turning now to FIGS. 9 and 10, a support finger 29 is
illustrated. The support finger 29 includes a non-vacuum support
pad cavity 81 at a portion of the support finger 29 distal to the
robot mounting end 19. The non-vacuum support pad cavity 81 is
generally circular in shape. The non-vacuum support pad 77 is held
in place within the non-vacuum support pad cavity 81 in the same
manner as described for the wafer engaging finger 27. The cavity
wall 29a includes bores 83a and 83b, extending through the entire
wall 29a. A spring clip 50 extends through a first section of the
cavity wall 29a, across the entire length of the non-vacuum support
pad cavity 81 and further through the second section of the cavity
wall 29b, as shown. The spring clip 50 is exposed to the non-vacuum
support pad cavity 84 and, as described with respect to the
wafer-engaging finger 27, arranged to make torsional contact with
the non-vacuum support pad 77.
[0031] The non-vacuum support pad cavity 81 extends partially into
the body of the support finger 29 and includes a wall bevel 85 that
angles into the body and away from the central axis of the
non-vacuum support pad cavity 81. The non-vacuum support pad 77
includes a wafer engaging surface 87 and a support engaging surface
89. The support engaging surface 89 has a greater diameter than the
wafer engaging surface 87 creating the wall bevel 85 around the
outer perimeter of the non-vacuum support pad 77. When the
non-vacuum support pad 77 is in its operational location, the wire
spring 50 rests on the bevel 85 providing torsional force to the
non-vacuum support pad 77. This force, because of the bevel, causes
the non-vacuum support pad 77 to be forced downward against the
non-vacuum support pad cavity bottom 91 and forward into the
beveled wall 85. The bevel on the outer perimeter of the non-vacuum
support pad 77 interlocks with the wall bevel 85 in the non-vacuum
support pad cavity wall, thus locking the non-vacuum support pad 77
in the non-vacuum support pad cavity 81. The support finger 29 does
not include a vacuum passageway and, as such, the non-vacuum
support pad 77 does not require a vacuum orifice nor does the
cavity bottom 91 include a vacuum aperture. The non-vacuum support
pad 77 merely supports a portion of a wafer during operation of the
robotic arm 20.
[0032] Although the present invention has been described with a
degree of particularity, it is the intent that the invention
include all modifications and alterations from the disclosed design
falling within the spirit or scope of the appended claims.
* * * * *