U.S. patent application number 14/451936 was filed with the patent office on 2014-11-20 for wafer clamp assembly for holding a wafer during a deposition process.
The applicant listed for this patent is TEXAS INSTRUMENTS DEUTSCHLAND GmbH. Invention is credited to Hermann Bichler, Stefan Fries, Reinhard Hanzlik, Frank Mueller, Heinrich Wachinger.
Application Number | 20140339074 14/451936 |
Document ID | / |
Family ID | 37563448 |
Filed Date | 2014-11-20 |
United States Patent
Application |
20140339074 |
Kind Code |
A1 |
Bichler; Hermann ; et
al. |
November 20, 2014 |
WAFER CLAMP ASSEMBLY FOR HOLDING A WAFER DURING A DEPOSITION
PROCESS
Abstract
A wafer clamp assembly for holding a wafer during a deposition
process comprises an outer annular member defining a central recess
that has a diameter slightly greater than the diameter of the
wafer. A plurality of finger members are carried by the outer
annular member and extend radially inwardly from the outer annular
member into the central recess, wherein each of the finger members
has a free end for contacting the wafer during the deposition
process.
Inventors: |
Bichler; Hermann; (Rohrbach,
DE) ; Hanzlik; Reinhard; (Freising, DE) ;
Fries; Stefan; (Landshut, DE) ; Mueller; Frank;
(Freising, DE) ; Wachinger; Heinrich;
(Helfenbrunn, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEXAS INSTRUMENTS DEUTSCHLAND GmbH |
Freising |
|
DE |
|
|
Family ID: |
37563448 |
Appl. No.: |
14/451936 |
Filed: |
August 5, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11456722 |
Jul 11, 2006 |
8795479 |
|
|
14451936 |
|
|
|
|
Current U.S.
Class: |
204/192.25 |
Current CPC
Class: |
H01L 21/02631 20130101;
C23C 16/4585 20130101; H01L 21/68728 20130101; H01L 21/68721
20130101; C23C 14/34 20130101; C23C 14/50 20130101 |
Class at
Publication: |
204/192.25 |
International
Class: |
C23C 14/50 20060101
C23C014/50; H01L 21/687 20060101 H01L021/687; H01L 21/02 20060101
H01L021/02; C23C 14/34 20060101 C23C014/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2005 |
DE |
10 2005 032 547.5 |
Claims
1. A method fabricating dies on a wafer during a semiconductor
process, said method comprising: providing a plurality of
substantially flat planar finger member mounted in an annular step
defining a depression of a wafer clamp assembly; providing an outer
annular member, coupled to the plurality of finger members and the
wafer clamp assembly, the outer annular member having a) a first
annular projection, and b) a second annular projection; contacting
said wafer during the semiconductor fabrication process with the
plurality of substantially flat finger members, wherein each of the
finger members include: a) a first portion with an essentially
rectangular cross-section; and b) a second portion, the second
portion having a free end that includes a contact portion, the
second portion having a rounded tip; a central recess defined by
the first annular projection, wherein the central recess has a
diameter that is greater than d, the diameter of the wafer, and
wherein the wafer can be clamped so that the wafer is not contacted
by the outer annular member during a deposition process of the
semiconductor, wherein the contact portion overhangs the wafer to
be clamped; wherein the contact portion of each finger member
overhangs the wafer to be clamped only at selected areas, wherein
the finger members contact the wafer only at the selected areas
where the finger members overhang the wafer, thereby reducing an
edge exclusion of the wafer, and wherein the contact portion has a
hemispherical shape thereby establishing a point contact surface
with the wafer, wherein said outer annular member has
radially-spaced first and second annular projections directed
downwardly therefrom; and said finger members are screw-mounted at
said first and second annular projections; and wherein said dies
are manufactured on said wafer.
2. The method of claim 1, wherein said contact portion is
downwardly directed.
3. The method of claim 2, wherein said second portion has a
horizontal cross-section that decreases radially inwardly from a
first width value which matches a width value of a corresponding
essentially rectangular horizontal cross-section of said first
portion, down to a second width value which is zero.
4. A method for fabricating an integrated circuit by holding a
wafer during a semiconductor process, said method comprising:
providing an outer annular member defining a central recess that
has a diameter slightly greater than the diameter of said wafer;
and contacting said wafer during a semiconductor fabrication
process with a plurality of finger members carried by said outer
annular member and extending radially inwardly from said outer
annular member into said central recess; and sputtering the
wafer.
5. The method of claim 4, wherein each of said finger members has a
contact portion that is provided at a bottom surface of said
respective finger member facing said wafer and contacting said
wafer during the semiconductor fabrication process.
6. The method of claim 5, wherein said contact portion contacting
said wafer is provided at a radially inwardly directed end of said
respective finger member.
7. The method of claim 5, wherein said contact portion contacting
said wafer has a hemispherical shape.
8. The method of claim 7, wherein the contact portion is connected
to a wafer clamp assembly.
9. The method of claim 8, wherein the wafer contains a plurality of
dies.
10. The method of claim 9, wherein a lesser amount of heat flux
from a wafer clamp assembly is produced through the finger
members.
11. An method for fabricating dies on a wafer by holding the wafer
during a semiconductor process, said method comprising: providing
an outer annular member means defining a central recess that has a
diameter slightly greater than the diameter of said wafer; and
contacting said wafer during a semiconductor fabrication process
with a plurality of finger members carried by said outer annular
member and extending radially inwardly from said outer annular
member into said central recess; and sputtering the wafer, wherein
a heat flows through the finger members during this sputtering; and
generating dies on the wafer.
12. The method of claim 11, wherein each of said finger members has
a contact portion that is provided at a bottom surface of said
respective finger member facing said wafer and contacting said
wafer during the semiconductor fabrication process.
13. The method of claim 12, wherein said contact portion contacting
said wafer is provided at a radially inwardly directed end of said
respective finger member.
14. The method of claim 13, wherein said contact portion contacting
said wafer has a hemispherical shape.
15. The method of claim 14, wherein the contact portion is
connected to a wafer clamp assembly.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 11/456,722, filed Jul. 11, 2006 (now U.S. Pat. No. 8,795,479),
which claims priority from German Patent Application No. 10 2005
032 547.5, filed Jul. 12, 2005, the entireties of both of which are
hereby incorporated by reference.
BACKGROUND
[0002] The present invention relates to a wafer clamp assembly for
holding a wafer during a deposition process.
[0003] During most deposition processes. it is necessary to hold
the wafer firmly against a support surface. During a sputter
deposition process, for example, the wafer is held to a pedestal of
a heater unit which is located in a chamber filled with a noble gas
or reactive gas up to a pressure in the millitorr range. Usually, a
clamp ring is used for clamping the wafer to the support surface.
The clamp ring has an inside diameter slightly smaller than the
diameter of the wafer thus contacting the wafer all around its
circumferential edge. Due to the large contact surface the edge
exclusion, i.e., the wafer area where no sputter deposition takes
place or sputter deposition is minimized, is in a considerable
range thereby reducing the surface which can be used for good
electrical dies. In addition, the wafer clamp is heated during the
sputtering process due to ion bombardment from the plasma and a
heat flux from the wafer clamp to the wafer takes place which makes
the outer parts of the wafer overheated. The material deposited in
this area loses its specified property and will decrease the number
of good electrical dies per wafer. Another problem related to the
clamp ring is that of clamp ring/wafer sticking In the area of
minimum distance to the wafer the clamp ring may stick to the wafer
due to the growing thickness of the sputtered material on the wafer
clamp. One approach to minimize the possibility of sticking is to
form a portion that overhangs the contact surface between the wafer
and the clamp ring, thereby blocking sputtered material from being
deposited in the area where the clamp makes contact with the wafer.
However, the overhang portion does not completely eliminate the
possibility of wafer sticking to the clamp ring.
SUMMARY
[0004] The present invention provides an improved wafer clamp
assembly that provides minimum edge exclusion, a reduced risk of
clamp assembly/wafer sticking and minimum heat flux from the wafer
clamp assembly to the wafer.
[0005] According to the present invention the wafer clamp assembly
comprises an outer annular member that defines a central recess
that has a diameter slightly greater than the diameter of the
wafer. A plurality of finger members are carried by the outer
annular member and extend radially inwardly from the outer annular
member into the central recess, wherein each of the finger members
has a free end for contacting the wafer during the deposition
process. Thus, the wafer clamp assembly does not contact the wafer
all around its outer circumferential edge, but only at a few,
selected areas where the finger members overhang the wafer. This
leads to a reduced edge exclusion compared to that with a
conventional wafer clamp ring and to a minimized heat flux from the
wafer clamp assembly to the wafer thereby increasing the wafer
surface area in which good electrical dies can be produced.
[0006] According to a preferred embodiment each of the finger
members has a contact portion that is provided at a bottom surface
of the respective finger member facing the wafer during the
deposition process. Thus, the wafer is not contacted in the whole
area in which the finger members overhang the wafer, but only in
the area associated with the contact portions which leads to a
further reduction in wafer/clamp assembly contact surface. In a
further preferred embodiment the contact portion has a
hemispherical shape so that a point contact is established between
the wafer and the clamp assembly thereby reducing the contact area
to a minimum.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Further features and advantages of the invention read from
the following description of an embodiment in accordance with the
present invention and with reference to the drawings in which:
[0008] FIG. 1 schematically shows in a sectional view a
conventional wafer clamp ring contacting a wafer all around its
circumferential edge;
[0009] FIG. 2 schematically shows the preferred embodiment of a
wafer clamp assembly according to the present invention, with a
wafer being clamped to a heatable pedestal;
[0010] FIG. 3 schematically shows a part of the wafer clamp
assembly of FIG. 2 in an enlarged view;
[0011] FIG. 4 schematically shows another part of the wafer clamp
assembly of FIG. 2 in an enlarged view;
[0012] FIG. 5 schematically shows the preferred embodiment of a
wafer clamp assembly of FIG. 2 in a top view.
DETAILED DESCRIPTION OF EMBODIMENTS
[0013] FIG. 1 of the drawings shows a part of a conventional wafer
clamp ring 10 in a side view that has an inner diameter that is
slightly smaller than the diameter of a wafer 12 to be clamped. The
wafer clamp ring 10 has an annular contact portion 14 contacting
the wafer 12 all around its outer circumferential edge. The wafer
clamp ring 10 further has a portion 16 that overhangs the annular
contact portion 14. In a region 18 in which the wafer clamp ring 10
contacts the wafer surface and in which the overhang portion 16
overhangs the wafer 12 no or only minimized sputter deposition
takes place. The area of the covered region 18 defines the edge
exclusion in which the wafer 12 cannot be used to produce good
electrical dies. Further, due to the large contact surface between
the wafer clamp ring 10 and the wafer 12 a heat flux from the
heated wafer clamp ring 10 to the wafer 12 takes place which makes
the wafer 12 near the clamp ring 10 overheated thereby also
decreasing the number of good electrical dies per wafer 12.
[0014] FIGS. 2 to 5 show the preferred embodiment of a wafer clamp
assembly according to the present invention. A wafer 20 is clamped
to a heatable and vertically adjustable pedestal 22 by means of the
wafer clamp assembly 24. The wafer clamp assembly 24 comprises an
outer annular member 26. In the center of the outer annular member
a central recess 28 is provided which has a diameter D that is
slightly greater than the diameter d of the wafer 20 to be clamped
so that the wafer 20 is not contacted by the outer annular member
26 during the deposition process. The preferred wafer clamp
assembly 24 further comprises a number of finger members 30 that
are carried by the outer annular member 26 and that extend radially
inwardly from the outer annular member 26 into the central recess
28. The finger members 30 thus protrude from the outer annular
member 26 into the central recess 28 thereby partly overhanging the
wafer 20 with a free end 29. Each finger member 30 has a contact
portion 32 that contacts the wafer 20 during the deposition
process. The contact portion 32 is provided at a bottom surface 34
facing the wafer 20 during the deposition process and at a radially
inwardly directed end 36 of the respective finger portion 30. The
contact portion 32 has a hemispherical shape thereby establishing a
point contact surface with the wafer 20.
[0015] FIG. 3 of the drawings also shows a finger member 30 from a
top view. The finger member 30 comprises a flat planar member
having a first portion 40 with an essentially rectangular
horizontal cross-section and a second portion 42 that forms the
radially inwardly directed end 36 of the finger portion 30 at which
the contact portion 32 is provided. The second portion 42 has a
width that is gradually decreasing from a first width value, which
corresponds to the width value of the rectangular first portion, to
a second width value, which is preferably zero, in the radially
inwardly direction so that a rounded tip 44 is formed.
[0016] The outer annular member 26 has an annular first projection
48 and an annular second projection 50 that is located radially
outward from of the first projection 48. The first and second
annular projections 48, 50 are directed downward during the
deposition process. In the preferred embodiment the numerous finger
members 30 are connected to the outer annular member 26 by
screw-mounting as shown in FIG. 4. Preferably, each finger member
30 is screw-mounted to the outer annular member 26 by means of two
screws 52, wherein one of the screws 52 extends through the annular
first projection 48 and the other of the screws 52 extends through
the annular second projection 50 in a mounted state.
[0017] Each finger member 30 is mounted in an annular depression 54
defined by a step 55 and formed in the top surface of the outer
annular member 26. The step 55 forms a stop for the finger members
30. The annular depression 54 is a planar depression that has a
rectangular horizontal cross-section that extends radially inwardly
from the step 55 all the way over the inner circumferential edge of
the outer annular member 26. In the mounted state in which the
finger members 30 are placed into the annular depression 54 in and
mounted to the outer annular member 26, their rounded tips 44 (see
FIG. 3) project inwardly from the outer annular member 26 and thus
shadow the outer edge of the wafer 20. A top view of the wafer
clamp assembly is shown in FIG. 5.
[0018] The wafer clamp assembly 24 of the present invention
overcomes the problems that are involved with the use of a
conventional clamp ring 10 as shown in FIG. 1:
[0019] Firstly, the wafer clamp assembly 24 according to the
present invention does not cooperate with the wafer 20 so as to
shadow it all around its outer circumferential edge, but it only
shadows the wafer 20 at a few, selected areas where the free ends
of the finger members 30 overhang the wafer 20. Thus, compared with
the wafer clamp ring 10 of FIG. 1 with the wafer clamp assembly 24
of the present invention a minimized edge exclusion is achieved
thereby increasing the wafer surface that can be used for the
production of good electrical dies. This advantageous effect is
increased due to the shape of the second portions 42 which form
rounded tips 44 and thus further minimize the shadowed wafer
surface.
[0020] Secondly, the surface contact of the wafer clamp assembly 24
with the wafer 20 is also drastically reduced during the deposition
process. The wafer clamp assembly 24 of the present invention only
contacts the wafer 20 at the few, selected contact surfaces where
the contact portions 32 of the finger portions 30 contact the wafer
surface, instead of the contact surface all around the
circumferential edge of the wafer with the wafer clamp ring 10 of
FIG. 1. Due to the hemispherical shape of the contact portions 32
the contact surfaces are point contacts, thereby further reducing
the surface contact of the clamp assembly 24 with the wafer 10. Due
to this minimized surface contact the heat flow from the heated
wafer clamp assembly 24 to the wafer 20 is insignificant, so that
the parts of the wafer 20 near the wafer clamp assembly 24 do not
become overheated. Further, since the surface contact is limited to
just a few point contacts, there are only very few positions where
the wafer 20 and the wafer clamp assembly 24 are in close
proximity, so that the risk of wafer clamp assembly/wafer sticking
is clearly reduced compared to that of the clamp ring assemblies
known from the prior art.
[0021] The wafer clamp ring assembly 24 of the present invention
can be manufactured in a very simple manner from a standard wafer
clamp ring as shown, for example, in FIG. 1 of the drawings. The
inner circumferential edge of such a standard wafer clamp ring is
milled out so as to remove the annular contact portion 14 and the
portion 16 overhanging the annular contact portion 14 and so as to
form the depression 54 at the inner circumferential edge of the
clamp ring. After that, the finger members 30 that have had to be
manufactured particularly for the improved wafer clamp assembly 24
according to the present invention are mounted to the milled-out
wafer clamp by placing them into the depression 54 with
predetermined distances and connecting them to the milled-out wafer
clamp. The milled-out wafer clamp forms the outer annular member 26
of the wafer clamp assembly 24. In the preferred embodiment the
finger members 30 are screw-mounted to the milled-out wafer
clamp.
* * * * *