U.S. patent application number 09/730872 was filed with the patent office on 2001-11-15 for heat exchanger apparatus for a semiconductor wafer support and method of fabricating same.
Invention is credited to Bercaw, Craig A., Duddy, Thomas M., Ellis, Robin M..
Application Number | 20010040157 09/730872 |
Document ID | / |
Family ID | 22639094 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010040157 |
Kind Code |
A1 |
Duddy, Thomas M. ; et
al. |
November 15, 2001 |
Heat exchanger apparatus for a semiconductor wafer support and
method of fabricating same
Abstract
A heat exchanger apparatus including a heat exchange element and
a substrate support. A clamp member is coupled to the heat exchange
element and the substrate support by expanding the clamp member to
an expanded state sufficient to surround a portion of the substrate
support and the heat exchange element, and contracting the clamp
member to couple the clamp member to the substrate support.
Inventors: |
Duddy, Thomas M.; (Foster
City, CA) ; Ellis, Robin M.; (San Bruno, CA) ;
Bercaw, Craig A.; (Sunnyvale, CA) |
Correspondence
Address: |
Patent Counsel
Applied Materials, Inc.
3050 Bowers Avenue
P.O. Box 450A
Santa Clara
CA
95052
US
|
Family ID: |
22639094 |
Appl. No.: |
09/730872 |
Filed: |
December 5, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09730872 |
Dec 5, 2000 |
|
|
|
09175143 |
Oct 19, 1998 |
|
|
|
Current U.S.
Class: |
219/444.1 ;
118/725 |
Current CPC
Class: |
H01L 21/67109 20130101;
C23C 16/4586 20130101; C23C 16/4585 20130101; Y10T 29/4935
20150115; C23C 16/463 20130101; Y10T 29/49373 20150115; C23C 16/46
20130101 |
Class at
Publication: |
219/444.1 ;
118/725 |
International
Class: |
H05B 003/68 |
Claims
What is claimed is:
1. A heat exchanger apparatus comprising: a substrate support
having a heat exchange element mounting portion; a heat exchange
element positioned within said heat exchange element mounting
portion; and a clamp member providing a compression fit to retain
said heat exchange element within the heat exchange element
mounting portion. .
2. The apparatus of claim 1 wherein said substrate support has a
substantially cylindrical outer surface that is circumscribed by
the clamp member.
3. The apparatus of claim 2 wherein said outer surface contains a
corkscrew channel.
4. The apparatus of claim 3 further comprising a cylindrical seal
member that is positioned about said outer surface and said clamp
element circumscribes said seal member.
5. The apparatus of claim 1 wherein the clamp member is cup-shaped
and supports the substrate support.
6. The apparatus of claim 1 wherein the heat exchange element is a
resistive heater.
7. The apparatus of claim 1 wherein the heat exchange element is a
tubular element carrying a cooling or a heating fluid.
8. The apparatus of claim 1 wherein the substrate support further
comprises a hollow shaft and the heat exchange element has three
portions, where a first portion extends through said hollow shaft,
a second portion extends from the first portion to a third portion
that resides in the heat exchange element mounting portion of the
substrate support.
9. A method of manufacturing a heat exchanger apparatus, the
apparatus including a substrate support, a heat exchange element,
and a clamp member, comprising: (a) mounting the heat exchange
element about a portion of the substrate support; (b) expanding the
clamp member relative to the substrate support; (c) positioning the
clamp member about a portion of the substrate support; and (d)
contracting the clamp member into contact with a portion of the
substrate support and the heat exchange element to maintain the
heat exchange element in contact with the substrate support.
10. The method of claim 9 wherein step (b) further comprises the
step of: (b1) heating the clamp member to expand the clamp member
relative to the substrate support.
11. The method of claim 10 wherein step (d) further comprises the
step of: (d1) cooling the clamp member to contract the clamp
member.
12. The method of claim 9 wherein the substrate support includes at
least one gas conduit coupled to a corkscrew channel formed on an
outer cylindrical surface of the substrate support, the corkscrew
channel positioned to transfer gas from a shaft portion of the heat
exchanger apparatus to the conduit, and wherein the heat exchanger
apparatus further includes a seal member, the method further
includes the steps, after step (a) and prior to step (b), of: (a1)
expanding the seal member; (a2) positioning the seal member about
the corkscrew channel in the outer cylindrical surface of the
substrate support; and (a3) contracting the seal member about the
substrate support to form a corkscrew conduit.
13. The method of claim 12 wherein step (a1) further comprises the
step of: (a11) heating the seal member to expand the seal member
relative to the substrate support.
14. The method of claim 10 wherein step (d1) further comprises the
step of: (d11) cooling the seal member to contract the seal
member.
15. The method of claim 9 wherein the substrate support includes at
least one gas conduit coupled to a corkscrew channel formed on an
outer cylindrical surface of the substrate support, the corkscrew
channel positioned to transfer gas from a shaft portion of the heat
exchanger apparatus to the conduit, and the portion of the
substrate support about which the clamp member is positioned
includes the corkscrew channel to form a corkscrew conduit.
16. The method of claim 9 wherein the clamp member is fabricated of
stainless steel and the substrate support is fabricated of
aluminum.
17. A method of manufacturing a wafer heater assembly comprising
the steps of: (a) providing a heater element within a channel
formed in a wafer platen; (b) heating a clamp member to expand the
clamp member to a size that enables the clamp member to
circumscribe the platen; (c) placing the clamp member about a
portion of the heater element and a portion of the platen; and (d)
cooling the clamp member to retain the heater element in the
channel of the platen.
18. The method of claim 17 wherein the platen includes at least one
gas conduit coupled to a corkscrew channel formed on an outer
cylindrical surface of the platen, the channel positioned to
transfer gas from a shaft portion of the heater assembly to the
conduit, and wherein the heater assembly further includes a seal
member, the method further including the steps, after said step (a)
and prior to step (b), of: (a1) heating the seal member to expand
the seal member; (a2) positioning the seal member about the
corkscrew channel; and (a3) cooling the seal member to affix the
seal member about the corkscrew channel and form a corkscrew
conduit.
19. The method of claim 18 wherein the platen includes at least one
gas conduit coupled to a corkscrew channel formed on an outer
cylindrical surface of the platen, the corkscrew channel positioned
to transfer gas from a shaft portion of the heat exchanger
apparatus to the conduit, and the portion of the platen about which
the clamp member is positioned includes the corkscrew channel to
form a corkscrew conduit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to wafer temperature control apparatus
for semiconductor wafer processing systems and, more specifically,
the invention relates to a heat exchanger apparatus for a
semiconductor wafer support in a semiconductor processing system
that maintains the wafer at a substantially constant temperature
during processing of the wafer.
[0003] 2. Description of the Related Art
[0004] Semiconductor wafer temperature control apparatus is useful
in a variety of applications, particularly in the manufacturing of
semiconductor devices using processes that require the wafers to be
maintained at stable temperatures. In particular, a resistive
heater may be utilized in, for example, chemical vapor deposition
(CVD) processing chambers to heat a wafer during processing and
maintain the wafer at an elevated temperature to facilitate film
deposition.
[0005] Typically, a heater assembly is a portion of a semiconductor
wafer support (known as a susceptor) and is comprised of a platen
that is fabricated of aluminum or other thermally conductive
material with a top surface having a generally circular shape for
supporting a semiconductor wafer within a process chamber. The
wafer support also includes a shaft which is coupled to the bottom
of the platen and supports the platen in the process chamber. A
heating element is mounted in or under the platen and is arranged
to be in thermally conductive contact with the surface of the
platen such that a wafer supported by the platen can be heated
during processing.
[0006] One manufacturing technique for a heater assembly is a
cast-in method wherein the heating element is cast-into the platen
as the platen is formed, i.e., a resistive heating element is
inserted into molten platen material (aluminum) during the platen
manufacturing process. To accomplish the insertion of the heating
element into the molten platen material without melting the heating
element, the melting point of the heating element must be
substantially higher than the melting point of the platen material.
This means that if stainless steel or aluminum are used as the
heating element, the types of materials which may be used for the
platen are limited.
[0007] Another manufacturing technique for a heater assembly is a
machined platen manufacturing technique wherein the heating element
is placed in a channel that is milled into the bottom surface of
the platen. The channel is filled with a high temperature epoxy and
a cover plate is then secured (welded) over the channel to seal the
heating element and epoxy into the platen. Unfortunately, the high
temperature epoxy has a limited life expectancy over which it
sufficiently supports the heating element and provides good thermal
conductivity to the platen. Over time, the epoxy breaks down and
ceases to be a good thermal conductor. As such, the useful life of
a platen is limited by the useful life of the heater element and
its mounting structure.
[0008] Therefore, there is a need in the art for an improved
temperature control apparatus that provides effective thermal
conductivity between a platen and a heat exchange element (e.g., a
heating element) without the use of epoxy or without strict limits
on the materials used to fabricate the platen and heat exchange
element.
SUMMARY OF THE INVENTION
[0009] The invention comprises a heat exchanger apparatus including
a heat exchange element coupled to a substrate support. To retain
the heat exchange element within the substrate support, a clamp
member is coupled to both the heat exchange element and the
substrate support. To assemble the heat exchanger apparatus, a
thermal differential is created between the clamp member and the
substrate support such that the clamp member is enlarged to
circumscribe the substrate support. Illustratively, the clamp
member is heated to expand it to an enlarged state sufficient to
surround the substrate support and the heat exchange element, and
then the clamp member is cooled to couple the clamp member to the
substrate support.
[0010] In an alternative embodiment, the substrate support
comprises a platen, being substantially cylindrical, with a
substantially flat wafer support surface and a bottom surface. The
bottom surface contains a channel into which a heat exchange
element is inserted and clamped, as discussed above, using a clamp
member. In this embodiment, a corkscrew channel is formed about the
outer surface of the cylindrical platen. A seal member, being a
substantially cylindrical ring, is heated to expand the ring, the
ring is positioned about the corkscrew channel and then the ring is
cooled to affix the seal member about the corkscrew channel. The
seal member in combination with the corkscrew channel forms a
corkscrew conduit. The clamp member is fitted over the seal member
to retain the heat exchange element in the platen as discussed
above. The corkscrew conduit is useful for providing an inert gas,
having a temperature defined by the temperature of the platen, to
the backside of the wafer located on the wafer support surface of
the platen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The teachings of the present invention can be readily
understood by considering the following detailed description in
conjunction with the accompanying drawings, in which:
[0012] FIG. 1 depicts a cross-sectional view of a heat exchanger
apparatus for use in a semiconductor wafer processing system in
accordance with the present invention;
[0013] FIG. 2 depicts a bottom view of the apparatus shown in FIG.
1;
[0014] FIG. 3 depicts a cross sectional view of an alternative
embodiment of the heat exchanger apparatus of the present
invention; and
[0015] FIG. 4 is a top view of the apparatus shown in FIG. 3;
[0016] FIG. 5 is a cross sectional view of a further embodiment of
the heat exchanger invention of the present invention.
[0017] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures.
DETAILED DESCRIPTION
[0018] FIG. 1 depicts a side cross sectional view of a heat
exchanger apparatus 10 in accordance with the present invention.
FIG. 2 depicts a bottom view of the heat exchanger apparatus 10 of
FIG. 1. To best understand the present invention, the reader should
simultaneously refer to FIGS. 1 and 2.
[0019] Apparatus 10 includes a hollow shaft 12 and a platen 14
suitable for supporting a substrate 5, such as a semiconductor
wafer, within a semiconductor wafer processing system such as
chemical vapor deposition (CVD) systems, physical vapor deposition
(PVD) systems, etch systems, plasma cleaning systems and the like.
Platen 14 has a substrate support surface 16 on which a substrate 5
may rest during processing. A heat exchange element 20 is
positioned proximate the surface 16 such that the temperature of
the element 20 is substantially the same as the temperature of the
surface 16. The element 20 includes a first portion 20A extending
substantially the length of and in shaft 12, a second
circumferential portion 20C that abuts the platen 14 and a third
portion 20B that interconnects the first portion 20A with the
second portion 20C. The lower portion 22 of the platen 14 includes
a recessed region 24 to allow a portion 20B of the heat exchange
element 20 to traverse the distance between the shaft 12 and the
circular ledge 18. The circumferential portion 20C of heat exchange
element 20 rests in a substantially circular depression 26 in
platen 14, which is defined in part by a circular ledge 18, and
allows the circumferential portion 20C of the element 20 to be
positioned to couple heat to or from the surface 16 of the heat
exchanger apparatus 10. The platen 14 is fabricated from a forged,
plate, cast or extruded metal body (e.g., aluminum) and the various
conduits, holes, depressions, recesses and channels are milled into
the body. Alternatively, the platen 14 is formed of non-metallic,
thermally conductive materials, i.e., a ceramic material such as
aluminum-nitride.
[0020] The heat exchange element 20 is an element that can control
the platen temperature, i.e., an element that heats and/or cools
the platen 14. For example, the element 20 may be a resistive
heater, i.e., a coil of resistive material that heats when
electrical current flows through it, a fluidic heater, i.e., a tube
or conduit through which a hot liquid flows, or a fluidic cooler,
i.e., a tube or conduit through which a coolant flows. The element
20 generally has a cross section that is circular, but may be of
any shape such as oval, square, triangular and the like. The
selection of the type and shape of heat exchange element 20 is a
design choice that depends upon the type of processing that will be
performed by the system in which the heat exchanger apparatus is
ultimately installed. The present invention ensures that the heat
exchange element 20, no matter what type or shape, is maintained in
thermally conductive contact with the platen 14 such that the
element temperature is substantially similar to the platen
temperature.
[0021] To maintain the element 20 in contact with the platen 14, a
clamp member 50 circumscribes the platen 14 and the circumferential
portion 20C of the heat exchange element 20. The clamp member 50
comprises a platen clamp portion 50A that circumscribes the outer
surface 21 of the platen 14, a heat exchange element clamp portion
50B that maintains the element 20 within channel 26 and a
depression cover portion 50C that covers the depression 24. The
clamp member 50 is installed using a "shrink fit" method that is
described in detail below. The heat exchange element clamp portion
50B contains holes 70 for allowing the lift pins 72 to freely move
vertically through the platen 14.
[0022] Thermal coupling between the heat exchange element 20 and
the platen 14 is greatly improved by providing a uniform
compressive force between the circumferential portion 20C of the
heat exchange element 20 and the platen 14. Element 20 is formed
such that the circumferential portion 20C of the element 20 has a
minimal tolerance which will allow the inner edge of the
circumferential portion 20C of the element 20 to engage the ledge
18. To facilitate thermal conduction, the ledge 18 has a
cross-sectional shape that approximately matches the shape of the
inner surface 20D of the circumferential portion 20C of the element
20. Also, it should be recognized that the effective diameter of
the heat exchange element 20 is such that an inner surface 20D of
the element 20 at the interior diameter of the circumferential
portion 20C is manufactured to match the diameter of the circular
ledge 18.
[0023] In accordance with the present invention, the method for
assembling the heat exchanger apparatus begins by placing the heat
exchange element 20 adjacent to the circular ledge 18, abutting the
depression 26 in the platen 14.
[0024] In order to impart a mechanical compressive force against
the heat exchange element 20 in a direction against the ledge 18,
the clamp member 50 is heated to a temperature that thermally
expands the clamp member 50. The amount of heating required must
result in an expansion of the clamp member 50 that is sufficient to
slip the clamp member 50 over the outer surface 21 of the platen
14. The amount of heating will vary depending upon the type of
material used to fabricate the clamp ring. The clamp member 50 is,
while in the expanded state, positioned about the circumferential
ledge 18 and into engagement with heat exchange element 20. Once in
position, the clamp member 50 is allowed to cool and hence shrink
to fit the ledge 18. Once cooled, clamp member 50 provides a
uniform compressive force on the heat exchange element 20 in
abutment with the depression 26 of platen 14. This compressive
force improves heat transfer between element 20 and platen 14
without using any thermally conductive filler material, e.g.,
epoxy. Moreover, this allows the heater assembly to be used at
temperatures in excess of 75% of the melting point of the platen
material, i.e., there is not a thermal drop across an epoxy
necessitating the use of a high temperature heat exchange element
to compensate for the heat loss. As such, the element can be
operated at a lower temperature than previously available and avoid
damage to both the element and the platen.
[0025] Although the clamp ring 50 was heated in the foregoing
description, the invention merely requires a thermal differential
to be achieved between the platen 14 and the clamp ring 50.
Consequently, the platen 14 could be chilled to contract its
physical size and the clamp member 50 slipped over the platen 14,
or the platen 14 could be chilled and the clamp ring 50 heated to
achieve the thermal differential that is necessary to interfit the
clamp ring 50 and platen 14.
[0026] The materials utilized in the heat exchange element 20 will
generally be stainless steel or aluminum. If the heat exchange
element 20 is a resistive heater, the heater may be a nickel
cadmium wire that is coated with magnesium amongst other well known
resistive heater materials. The platen 14 will generally be
manufactured of metal such as aluminum, stainless steel or other
alloys of these metals. The clamp member 50 is generally comprised
of aluminum or stainless steel.
[0027] The clamp member 50 may be fabricated of a different
material than the platen 14. For example, the clamp member 50 could
be stainless steel and the platen 14 could be aluminum. Using a
clamp member with a higher melting point, the clamp member 50
provides structural support to the platen 14. To enhance the
structural support, the clamp member 50 can be cup shaped to
substantially support the entire bottom surface of the platen 14 as
well as provide the clamping function for the heat exchange element
20. Consequently, with the clamp member 50 providing physical
support to the platen 14, the apparatus can be used at temperatures
that approach the melting point of the platen material and the
platen 14 will not "droop" or otherwise deform at these high
temperatures.
[0028] FIG. 3 depicts a cross sectional view of an alternative
embodiment of the present invention and FIG. 4 depicts a top plan
view of the alternative embodiment of FIG. 3. To best understand
this alternative embodiment, the reader should simultaneously refer
to FIGS. 3 and 4.
[0029] The alternative embodiment of FIGS. 3 and 4 adds to the
first embodiment of FIGS. 1 and 2 a corkscrew conduit 34 that is
used to control the temperature of a so-called "backside gas" that
is supplied to the surface 16 of the platen 14, i.e., beneath the
backside of a wafer. To form the conduit 34, a corkscrew channel 40
is cut into the outer surface 21 of the platen 14. A seal ring 45,
having a smooth inner surface 45A, is positioned to abut the
surface 21 of the platen 14 and form a cover for the channel 40
such that the corkscrew conduit 34 is formed. Of course, in an
equivalent manner, the corkscrew channel could be formed in the
inner surface 45A of the seal member and the surface 21 could be
smooth.
[0030] The corkscrew conduit 34 is coupled to conduits 42 and 44
which connect via bores 62 and 64 that extend to the surface 16 of
the platen 14. The corkscrew conduit 34 is also coupled to a heat
transfer gas source (not shown) via plenum 60 and conduit 37. As
such, the heat transfer gas, typically an inert gas such as helium
or argon, is applied to the backside of the wafer during processing
of the wafer to produce more effective thermal coupling between the
wafer and the platen 14. The flow of backside gas also prevents
process gases from contacting the backside of the wafer. As the gas
traverses the corkscrew conduit 34, it is heated or cooled to the
temperature of the platen 14. As such, the gas between the surface
16 and the wafer is substantially the same temperature as the
platen 14 and the heat exchange element 20. As such, additional
temperature uniformity is provided.
[0031] In order to seal the gas conduits 42 and 44 and the
corkscrew conduit 34, the seal ring 45 is secured to the platen
using the differential heating assembly technique that was
described above. Specifically, the seal ring 45, which is generally
fabricated of aluminum or stainless steel, is heated to a high
temperature in order to expand its physical size and the seal ring
45 is fitted about the platen 14. When cooled, the seal ring 45
will "shrink fit" about the outer surface 21 with compressive
force. It should be readily understood that the seal ring 45 is
generally installed prior to application of the heat exchange
element 20 in recess 18 as described above. In this alternative
embodiment, the clamp member 50 is then secured about the seal
member 45. All other components and assembly techniques discussed
above are substantially the same.
[0032] FIG. 5 depicts a cross sectional view of a further
embodiment of the present invention. In this embodiment, a clamp
member is integrated with a seal member to form a single element, a
clamp/seal member 500. The member 500 has a cylindrical portion
500A that abuts the surface 21 of the platen 14 to form the
corkscrew conduit 34. The member 500, similar to member 50 of FIG.
1, also has a portion 500B that abuts the heat exchange element 20
and a portion 500C that covers the depression 26. In addition, the
clamp/seal member 500 of this embodiment is depicted as being
cup-shaped such that the portion 500C extends completely beneath
the platen 14 and abuts the shaft 12. As such, the cup-shaped
clamp/seal member supports the platen 14 to provide structural
rigidity to the heat exchanger apparatus 10. As mentioned above,
the clamp members of the embodiments shown in FIGS. 1 and 3 can
also be adapted to extend completely beneath the platen as shown in
FIG. 5. Conversely, the clamp/seal member 500 can be adapted to
partially extend beneath the platen in the same manner as the clamp
members of FIGS. 1 and 3.
[0033] The many features and advantages of the present invention
will be apparent to one of average skill in the art. Moreover
numerous modifications to the structure and method are
contemplated. Each of such modifications apparent to one of average
skill in the art, and all such features and advantages are intended
to be within the scope of the invention as defined by the present
application and the following claims.
* * * * *