U.S. patent application number 09/896525 was filed with the patent office on 2001-11-15 for thermal processing chamber for heating and cooling wafer-like objects.
This patent application is currently assigned to FSI International Inc.. Invention is credited to Ibrani, Sokol, Kasahara, Jack S., Kumar, Devendra, Nguyen, Vuong P., Womack, Jeffrey D..
Application Number | 20010040155 09/896525 |
Document ID | / |
Family ID | 23381509 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010040155 |
Kind Code |
A1 |
Womack, Jeffrey D. ; et
al. |
November 15, 2001 |
Thermal processing chamber for heating and cooling wafer-like
objects
Abstract
A processing chamber and methods for employing this processing
chamber to thermally treat wafer-like objects. The chamber
comprises a double walled shell, a pedestal style heater, internal
passages for the transport of cooling gases and removal of exhaust
gases, independently variable gas introduction patterns, and a
movable door for sealing the chamber. The chamber is designed to
permit in situ cooling of wafer-like objects and to provide means
for precise optimization of this cooling. The methods provide for
the processing of the wafer-like object in an environment where the
temperature, rate of change of the temperature, composition of
gases and the relative timings of changes to these variables may be
controlled to achieve the desired material properties in the
wafer-like object or in films contained on this wafer-like
object.
Inventors: |
Womack, Jeffrey D.;
(Pleasanton, CA) ; Nguyen, Vuong P.; (San Jose,
CA) ; Kumar, Devendra; (Los Altos, CA) ;
Kasahara, Jack S.; (Los Gatos, CA) ; Ibrani,
Sokol; (Pleasanton, CA) |
Correspondence
Address: |
Mark W. Binder, Esq.
Kagan Binder, PLLC
Suite 200
221 Main Street North
Stillwater
MN
55082-5021
US
|
Assignee: |
FSI International Inc.
|
Family ID: |
23381509 |
Appl. No.: |
09/896525 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09896525 |
Jun 29, 2001 |
|
|
|
09351586 |
Jul 12, 1999 |
|
|
|
Current U.S.
Class: |
219/390 ;
219/444.1 |
Current CPC
Class: |
H01L 21/67109
20130101 |
Class at
Publication: |
219/390 ;
219/444.1 |
International
Class: |
F27B 005/14; H05B
003/68 |
Claims
What is claimed is:
1. An apparatus for thermally processing wafer-like objects
comprising: a thermal processing chamber having a walled structure
within which an internal chamber is defined and a transfer opening
through which a wafer-like object can be insert or removed from the
internal chamber, the walled structure including at least an
insulating portion thereof comprising spaced inner and outer wall
portions; a platen operatively positioned within the thermal
processing chamber and including a heat generation device and
having a support surface for supporting a wafer-like object in heat
transfer contact; a gas inlet permitting gas flow into the internal
chamber; and a gas outlet through which gas can be exhausted from
the internal chamber, the gas outlet having a location that is
spaced from a location of the gas inlet with respect to the platen
so that gas will flow at least partially about the platen when gas
is exhausted from the internal chamber.
2. The apparatus of claim 1, wherein the thermal processing chamber
comprises a bottom wall and at least one side wall, and the
insulating portion of the walled structure is provided within the
side wall.
3. The apparatus of claim 2, wherein the thermal processing chamber
further comprises a lid, and the lid also includes a portion having
inner and outer spaced wall portions.
4. The apparatus of claim 3, wherein the lid comprises at least one
supply chamber formed by its inner and outer spaced wall portions,
and at least one gas inlet open from the supply chamber into the
internal chamber of the thermal processing chamber.
5. The apparatus of claim 4, wherein the lid comprises a plurality
of supply chambers that are fluidly isolated from one another, each
supply chamber being formed by inner and outer spaced wall portions
of the lid, and each having at least one gas inlet that opens into
the internal chamber of the thermal processing chamber.
6. The apparatus of claim 2, wherein the platen is operatively
supported by the bottom of the thermal processing chamber by way of
a pedestal base, and the bottom includes a cooling channel
extending over at least a portion of the bottom and connectable
with a source of cooling fluid for controlling the temperature of
the portion of the bottom.
7. The apparatus of claim 6, wherein the cooling channel
substantially surrounds the pedestal base.
8. The apparatus of claim 2, wherein the bottom of the thermal
processing chamber further includes an exhaust channel extending
along at least a portion of the bottom and which is open to the
internal chamber by at least one gas outlet.
9. The apparatus of claim 8, wherein the gas outlet is provided
through an exhaust plate that is removably connected with the
thermal processing chamber so that exhaust flow can be modified by
changing the exhaust plate with a different gas outlet fluid flow
capacity.
10. The apparatus of claim 9, wherein the platen is operatively
supported by the bottom of the thermal processing chamber by way of
a pedestal base, and the bottom includes a cooling channel
extending over at least a portion of the bottom and connectable
with a source of cooling fluid for controlling the temperature of
the portion of the bottom, and the exhaust plate separates at least
a portion of the exhaust plate from the cooling channel.
11. The apparatus of claim 10, wherein the bottom includes a
relatively thicker central region and a peripheral thinner region,
and the exhaust channel and the cooling channel extend within the
thicker central region.
12. The apparatus of claim 11, further including an outside bottom
wall that is spaced from the peripheral thinner region of the
bottom, which is connected thereto so as to provide another
insulating portion of the thermal processing chamber.
13. The apparatus of claim 2, further including a movable element
that is operatively movably supported relative to the support
surface of the platen for engaging a wafer-like object when
supported within the thermal processing chamber and for moving the
wafer-like object from heat transfer contact with the platen to a
spaced cooling position.
14. An apparatus for thermally processing wafer-like objects
comprising: a thermal processing chamber having a walled structure
comprising a bottom and at least one side wall within which an
internal chamber is defined and a transfer opening through the side
wall so that a wafer-like object can be insert or removed from the
internal chamber; a platen operatively positioned within the
thermal processing chamber and including a heat generation device
and having a support surface for supporting a wafer-like object in
heat transfer contact; a gas inlet permitting gas flow into the
internal chamber; and a gas outlet through which gas can be
exhausted from the internal chamber, the gas outlet having a
location that is spaced from a location of the gas inlet with
respect to the platen so that gas will flow at least partially
about the platen when gas is exhausted from the internal chamber,
wherein the platen is operatively supported by the bottom of the
thermal processing chamber by way of a pedestal base, and the
bottom includes a cooling channel extending over at least a portion
of the bottom and connectable with a source of cooling fluid for
controlling the temperature of the portion of the bottom.
15. The apparatus of claim 14, wherein the cooling channel
substantially surrounds the pedestal base.
16. The apparatus of claim 15, wherein the bottom of the thermal
processing chamber further includes an exhaust channel extending
along at least a portion of the bottom and which is open to the
internal chamber by at least one gas outlet.
17. The apparatus of claim 16, wherein the gas outlet is provided
through an exhaust plate that is removably connected with the
thermal processing chamber so that exhaust flow can be modified by
changing the exhaust plate with a different gas outlet fluid flow
capacity.
18. The apparatus of claim 17, wherein the bottom includes a
relatively thicker central region and a peripheral thinner region,
and the exhaust channel and the cooling channel extend within the
thicker central region.
19. The apparatus of claim 14, wherein the side wall structure of
the thermal processing chamber includes at least an insulating
portion thereof comprising spaced inner and outer wall
portions.
20. An apparatus for thermally processing wafer-like objects
comprising: a thermal processing chamber having a walled structure
comprising a bottom, at least one side wall and a lid within which
an internal chamber is defined and a transfer opening through the
side wall so that a wafer-like object can be insert or removed from
the internal chamber; a platen operatively positioned within the
thermal processing chamber and including a heat generation device
and having a support surface for supporting a wafer-like object in
heat transfer contact; a gas inlet permitting gas flow into the
internal chamber; and a gas outlet through which gas can be
exhausted from the internal chamber, the gas outlet having a
location that is spaced from a location of the gas inlet with
respect to the platen so that gas will flow at least partially
about the platen when gas is exhausted from the internal chamber,
wherein the lid of the thermal processing chamber includes a
portion thereof having inner and outer spaced wall portions that
provide at least one supply chamber formed by the inner and outer
spaced wall portions, and the gas inlet is open from the supply
chamber into the internal chamber of the thermal processing
chamber.
21. The apparatus of claim 20, wherein the lid comprises a
plurality of supply chambers that are fluidly isolated from one
another, each supply chamber being formed by inner and outer spaced
wall portions of the lid, and each having at least one gas inlet
that opens into the internal chamber of the thermal processing
chamber, the platen is operatively supported by the bottom of the
thermal processing chamber by way of a pedestal base, and the
bottom includes a cooling channel extending over at least a portion
of the bottom and connectable with a source of cooling fluid for
controlling the temperature of the portion of the bottom.
22. The apparatus of claim 21, wherein the side wall structure of
the thermal processing chamber includes at least an insulating
portion thereof comprising spaced inner and outer wall
portions.
23. An apparatus for thermally processing wafer-like objects
comprising: a thermal processing chamber having a walled structure
comprising a bottom and at least one side wall within which an
internal chamber is defined and a transfer opening through the side
wall so that a wafer-like object can be insert or removed from the
internal chamber; a platen operatively positioned within the
thermal processing chamber and including a heat generation device
and having a support surface for supporting a wafer-like object in
heat transfer contact; a gas inlet permitting gas flow into the
internal chamber; and a gas outlet through which gas can be
exhausted from the internal chamber, the gas outlet having a
location that is spaced from a location of the gas inlet with
respect to the platen so that gas will flow at least partially
about the platen when gas is exhausted from the internal chamber,
wherein the bottom of the thermal processing chamber further
includes an exhaust channel extending along at least a portion of
the bottom and which is open to the internal chamber by the gas
outlet.
24. The apparatus of claim 23, wherein the gas outlet is provided
through an exhaust plate that is removably connected with the
thermal processing chamber so that exhaust flow can be modified by
changing the exhaust plate with a different gas outlet fluid flow
capacity.
25. The apparatus of claim 24, wherein the platen is operatively
supported by the bottom of the thermal processing chamber by way of
a pedestal base, and the bottom includes a cooling channel
extending over at least a portion of the bottom and connectable
with a source of cooling fluid for controlling the temperature of
the portion of the bottom.
26. The apparatus of claim 25, wherein the exhaust plate separates
at least a portion of the exhaust plate from the cooling
channel.
27. The apparatus of claim 25, wherein the bottom includes a
relatively thicker central region and a peripheral thinner region,
and the exhaust channel and the cooling channel extend within the
thicker central region.
28. The apparatus of claim 27, further including an outside bottom
wall that is spaced from the peripheral thinner region of the
bottom, which is connected thereto so as to provide another
insulating portion of the thermal processing chamber.
29. The apparatus of claim 23, wherein the side wall structure of
the thermal processing chamber includes at least an insulating
portion thereof comprising spaced inner and outer wall
portions.
30. A method of thermally processing a wafer-like object within a
thermal processing chamber having an internal chamber, a transfer
opening through which a wafer-like object can be insert or removed
from the internal chamber and a platen operatively positioned
within the thermal processing chamber and including a heat
generation device and having a support surface for supporting a
wafer-like object in heat transfer contact, the method including
the steps of: providing a wafer-like object in heat transfer
contact with the support surface of the platen within the internal
chamber of the thermal processing chamber; heating the wafer-like
object by heat generated by the heat generation device; moving the
wafer-like object from heat transfer contact with the support
surface of the platen by a displacement mechanism operatively
provided with the thermal processing chamber to a cooling position;
circulating cooling gas through the internal chamber from a gas
inlet, over at least a portion of the wafer-like object and thus
cooling at least the portion of the wafer-like object and through a
gas outlet.
31. The method of claim 30, wherein the step of circulating gas
through the internal chamber includes supplying gas by way of a
supply channel defined within a lid of the thermal processing
chamber and through a plurality of gas inlets.
32. The method of claim 31, wherein the step of circulating gas
through the internal chamber further includes supplying gas by way
of a plurality of supply channels that are defined within a lid of
the thermal processing chamber and through a plurality of gas
inlets for each supply channel.
33. The method of claim 30, wherein the step of circulating gas
through the internal chamber further includes exhausting gas
through a channel defined within a bottom of the thermal processing
chamber by way of a plurality of gas outlets provided through an
exhaust plate.
34. The method of claim 33, further including the step of
transferring the wafer-like object from within the internal chamber
through the transfer opening after it is heated and cooled.
35. The method of claim 34, further including the step of removing
the exhaust plate and replacing it with another exhaust plate
having a different gas outlet flow capacity.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to systems and methods for
thermally processing a wafer-like object through a temperature
profile that preferably includes both heating and cooling the
wafer-like object. In particular, the present invention is directed
to an apparatus having a thermal processing chamber which can
support, heat and cool such an object with thermal uniformity and
effective heat transfer even when the heating requirements are
high. The present invention also allows the creation and
maintenance of a processing environment constituted of precisely
controlled mixtures of gases that may vary widely from the ambient
environment.
BACKGROUND OF THE INVENTION
[0002] The present invention has been developed for its particular
applicability in the processing of semiconductor wafers, such as
for making microelectronic devices, where such processing requires
precise temperature control and temperature changes. This
processing may also require control of the gas mixtures allowed to
contact the wafer during the process. Many other types of products
and processes involve thermal processing with accurate temperature
control of an object, such objects hereinafter referred to as
"wafer-like" objects.
[0003] In the manufacture of microelectronic devices, such as
integrated circuits, flat panel displays, thin film heads, and the
like, processing often involves the application of a layer of some
material, such as a dielectric, onto the surface of a substrate,
such as a semiconductor wafer in the case of integrated circuits.
Dielectrics, for example, may need to be baked and then cooled to
cure. To prevent oxidation of such a dielectric material, for
example, after any processing there of by a baking step, the wafer
must be cooled to a certain temperature in an environment of
reduced oxygen (an anaerobic environment). Cooling of the wafer
also reduces the risk of thermal damage to the wafer transfer
mechanism during wafer transfer after processing. The baking and
cooling steps must be precisely controlled within exacting
temperature constraints to ensure that the selected portions of the
dielectric properly set with its desired material properties.
Baking and cooling operations for microelectronic devices typically
involves cycling a wafer-like object through a desired temperature
profile in which the object is maintained at an elevated
equilibrium temperature in a controlled environment, cooled to a
relatively cool equilibrium temperature, and/or subjected to
temperature changes of varying rates (in terms of .degree. C./s)
between the equilibrium temperatures. To accomplish baking and
cooling, previously known bake/chill operations have included
separate bake and chill plates that have required the use of a
wafer transport mechanism in order to physically lift and transfer
the wafer itself from one place to the other. This approach
presents a number of drawbacks. First, wafer temperature is not
controlled during transfer between the bake and chill plates.
Second, the overall time required to complete the bake/chill
process cannot be precisely controlled because of the variable time
required to move the wafer to and from the respective plates.
Third, the required movement takes time and thus reduces the
throughput of the manufacturing process. Fourth, the cost of
equipment is higher than necessary because the apparatus requires
extra components to handle the wafer during transport from plate to
plate. Fifth, the mechanical move from plate to plate introduces
the possibility of contaminating the wafer. Sixth, the wafer is
exposed to atmospheric oxygen while it is at elevated temperatures,
increasing the risk of oxidation. Seventh, the wafer transfer
mechanism is exposed to elevated temperatures, reducing its
reliability and/or increasing the complexity and expense of its
design.
[0004] To overcome these deficiencies, a combination bake/chill
apparatus has been previously developed by the assignee of the
present invention, which is described in copending U.S. patent
application Ser. No. 09/035,628, filed Mar. 5, 1998 and entitled
"Combination Bake/Chill Apparatus Incorporating Low Thermal Mass,
Thermally Conductive Bakeplate", the entire disclosure of which is
incorporated herein by reference. That combination bake/chill
apparatus includes a low thermal mass, thermally conductive
bakeplate to support a wafer during both its baking and chilling
operations. With the wafer on one surface of the bakeplate, the
other surface of the bakeplate is selectively brought into or out
of thermal contact with a thermally massive chill plate so as to
switch between baking and chilling operations. In one version, the
bakeplate can rest on top of the chill plate during chilling, and
one or both of the components is moved to separate them during
baking. The bakeplate can heat a wafer by direct conduction of heat
generated by the bakeplate to the wafer, while chilling requires
heat transfer from the wafer through the bakeplate (which is not
heated during the chilling operation) to the chill plate by
conduction, which itself is preferably artificially cooled. Both
the bake and chill plates are operatively supported within a
housing defining a thermal processing chamber. In particular, the
housing is formed as a cylinder comprising a cylindrical side wall,
a flat top wall, and a flat bottom wall through which various
control components extend. The side wall is split so that the top
and bottom walls are relatively movable from one another to provide
access within the process chamber for loading and unloading
wafers.
[0005] In developing the present invention, it was discovered that
thermal uniformity of a wafer-like object within such a processing
chamber is significantly affected by the design and make-up of the
process chamber itself. That is, the components making up the
processing chamber as well as the components within the chamber,
such as for supporting, heating and cooling a wafer-like object,
significantly affect the temperature of the wafer-like object
throughout its surface area. This is particularly true where such a
wafer-like object is to be uniformly heated at relatively high
temperatures, e.g., above 200.degree. C. and as high as 456.degree.
C. or more. Newer polymers and coatings for semiconductor wafers
cure at temperatures of between 350.degree. C. and 450.degree. C.,
for example. However, as noted above, precise temperature
achievement of the entire surface area of a wafer-like object may
be required for effective curing or processing. Such thermal
uniformity being required in spite of the fact that such a
processing chamber should advantageously be designed as a
combination baking and cooling apparatus. That is, thermal
uniformity is desired even where a wafer-like object is to be
heated and cooled within the same chamber. Thus, the structure
defining the process chamber and its internal devices not only
affect the uniformity of the thermal processing that is conducted
on a wafer-like object, they also are subject to cyclical heating
and cooling. In general, thermal uniformity in processing a
wafer-like object is a function of the relative thermal uniformity
of the chamber and its components. So, to achieve good thermal
uniformity, such as during a baking step, the process chamber
housing and components should be together brought within a desired
temperature range. But, as a result of a subsequent cooling
operation, the entire chamber and components would be cooled, or at
least its temperature uniformity would be compromised. In any case,
cycle times would be lengthened in that the achievement of thermal
uniformity of a next heating process would require greater time to
assure a subsequent achievement of sufficient temperature
uniformity of the process chamber.
[0006] In developing the present invention, it was also discovered
that the gases contained within the processing environment of a
baking and cooling apparatus during both steps should be controlled
for enhancing the development of the desired material
properties.
SUMMARY OF THE INVENTION
[0007] The present invention overcomes the deficiencies and
shortcomings of the prior art by providing an apparatus and method
for efficiently and effectively heating and cooling a wafer-like
object within a controlled environment in the same process chamber.
In accordance with the present invention, the process chamber and
its components are designed to enhance thermal uniformity for the
thermal processing operation, but to permit a temperature profile
to be conducted including heating and cooling steps with maximized
throughput through the apparatus. In particular, the process
chamber can uniformly heat objects to high temperatures and still
provide effective cooling in situ, all of which may advantageously
occur in an environment where the mixture of gases can be carefully
controlled.
[0008] In accordance with the present invention, good thermal
uniformity can be achieved across the surface area of a wafer-like
object while the wafer-like object can achieve sufficiently high
and low temperatures in accordance with a desired temperature
profile. In particular, the process chamber is designed so that its
inner surface remains of a sufficiently high temperature relative
to the desired temperature of the heating operation even during the
cooling of the wafer-like object. Thus, during a subsequent heating
step, good thermal uniformity can be achieved with respect to the
surface area of a subsequent wafer-like object and with greater
throughput. Preferably, the process chamber is also sufficiently
sealable and closeable by a chamber door so that the thermal
processing can be conducted within an anaerobic environment created
by the suitable flow of inert gases as well.
[0009] The above advantages are achieved by carefully controlling
the flow of heat (radiatively, convectively and conductively) as
well as the composition of the gases in the processing environment.
Radiative heat transfer control is achieved by maintaining the
surfaces "visible" to the wafer-like object as close to the
processing temperature as possible. Convective heat transfer
control is achieved by establishing the proper gas flow pattern on
the exposed surface of the wafer-like object. This flow pattern may
be called upon to correct for other nonuniformities in the process.
Conductive heat transfer control is achieved by ensuring uniform
contact between the wafer-like object and the heating surface and
by ensuring that the contacting surface temperature is as uniform
as possible. Control of the gas composition in the processing
environment is achieved by isolating the processing environment
from the ambient environment and by maximizing the flexibility and
control of gas flow in the processing environment.
[0010] In the present invention, the surfaces visible to the
wafer-like object are preferably maintained close to the processing
temperature through the use of three essential features. First, the
chamber incorporates a double walled design that allows superior
thermal isolation of the inner surface from the much cooler outer
surface. Second, the cooling required to maintain some chamber
seals within their thermal operating ranges is accomplished by the
use of an internal gas cooling channels rather than a liquid
cooling channel. Due to their generally lower heat capacity than
liquids, gases allow more precise and reliable temperature control
by permitting finer control of the heat transfer rate. The thermal
limit of liquids also constrains their boiling point, which can
create safety as well as reliability hazards. The thermal limit of
gases allows the chamber wall to operate at higher temperatures,
reducing heat transfer from the wafer-like object and, therefore,
improving temperature uniformity. Third, careful control of the
heat transfer from the heating element to the chamber bottom and
side walls prevent temperature gradients along the walls, improving
the uniformity of the visible surfaces. This control may be
achieved by reducing the cross sectional area of conductive paths
or by increasing their lengths. Control may also be achieved by
minimizing emissivity of the heater surface thereby minimizing the
radiation between the heater and the chamber wall.
[0011] The present invention promotes the development of the proper
convective gas flow through the use of three elements. First, the
use of separately variable inner and outer gas introduction
patterns above the wafer-like object allow the ratio and magnitude
of the flows to be adjusted to achieve the optimum flow pattern on
the wafer-like object. Second, the use of a door minimizes gas
disturbances during transfer of the wafer-like object, minimizing
the time required to establish the required gas flow. Third, the
use of removable exhaust plate simplifies the investigation of
widely varying exhaust patterns, promoting the achievement of the
optimum gas flow environment.
[0012] To ensure superior conductive heat transfer control, the
present invention preferably employs a "pedestal" style heater that
contacts the cooler chamber bottom wall at a single, preferably
central point. This point of contact may then be carefully
minimized to reduce losses to the chamber, improving pedestal
surface uniformity. Heater surface uniformity is also improved by
maximizing the radiative emissivity between the wafer-like object
and the contacting heater surface while minimizing the radiative
emissivity between the other heater surfaces and the chamber wall.
The radiative emissivity of the heater surfaces may be controlled
by chemical (e.g. anodization) or mechanical (e.g. ball peening)
treatment. In particular, the surface or surfaces visible to the
wafer-like object may be anodized while the other surfaces are left
with a finely machined finish. To ensure good contact between the
wafer-like object and the heater surface, channels on the pedestal
surface are evacuated, the resulting pressure difference across the
wafer-like object driving it against the heater surface.
[0013] To control the gas composition in the process environment,
the present invention employs a door that, as was previously
described, minimizes gas disturbances during transfer of the
wafer-like object. The separate inner and outer gas introduction
patterns allow sophisticated purging routines to be developed that
can create the proper gas composition in the minimum amount of
time. The removable exhaust plate assists in establishing the
optimum gas flow pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above-mentioned and other advantages of the present
invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of the preferred embodiments
of the invention taken in conjunction with the accompanying
drawings, wherein:
[0015] FIG. 1 is a partially exploded view in perspective of an
apparatus in accordance with the present invention including a
thermal processing chamber for heating and cooling wafer-like
objects that are supported within the thermal processing
chamber;
[0016] FIG. 2 is a cross sectional view taken through the thermal
processing chamber of FIG. s1 and illustrating a wafer-like object
supported within the thermal processing chamber that is configured
in a heating state with the wafer-like object in thermal transfer
contact with a pedestal heater;
[0017] FIG. 3 is another cross sectional view taken through the
thermal processing chamber of FIG. 1 and illustrating a wafer-like
object supported within the thermal processing chamber that is
configured in a cooling state with the wafer-like object supported
out of heat transfer contact with the pedestal heater and with the
cooling gas flow established;
[0018] FIG. 4 is another cross sectional view taken through the
thermal processing chamber of Figure and illustrating a wafer-like
object supported within the thermal processing chamber that is
configured in the transfer state with the chamber door in an open
position to permit access to the internal chamber from outside;
[0019] FIG. 5 is a top plan view of a pedestal heater showing one
possible configuration for a heater layout;
[0020] FIG. 6 is a cross sectional view through the pedestal heater
illustrated in FIG. 5;
[0021] FIG. 7 is a perspective view of an alternative apparatus
including another thermal processing chamber also in accordance
with the present invention;
[0022] FIG. 8 is a cross sectional view taken through the thermal
processing chamber of FIG. 7; and
[0023] FIG. 9 is a top plan view illustrating a cluster processing
apparatus that may include a thermal processing chamber in
accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED INVENTION
[0024] With reference to the Figures, wherein like components are
labeled with like numerals throughout the several Figures, and
initially to FIG. 1, an apparatus is illustrated including a
thermal processing chamber 10 supported by a support plate 12 that
facilitates mounting of the thermal processing chamber 10 to
additional apparatus support structure based upon a particular
application. For example, the apparatus may be provided as a
standalone system wherein the thermal processing chamber 10 and
support plate 12 are supported and encased to define a modular
piece of equipment. As another example, the thermal processing
chamber 10 can be supported by the support plate 12 and positioned
within a cluster tool system as illustrated in FIG. 9, which is
described in greater detail below.
[0025] With reference also to FIG. 2, an internal chamber 14 is
defined within the thermal processing chamber 10 within which a
wafer-like object 16 is supported on a pedestal platen 18. Although
the present is specifically designed for the processing of
semiconductor wafers, it is understood that the present invention
may be used for thermal processing of many other types of
wafer-like objects 16. The term wafer-like object is meant to
include any object that defines at least one major surface that can
be supported in thermal transfer contact by a platen and is not
limited to substrates that are circular (like a semiconductor
wafer). The pedestal platen 18 preferably comprises a pedestal
heater, which will be described in greater detail below for the
purpose of not only supporting a wafer-like object 16 in thermal
transfer contact, but also to generate the heat that is to be
transferred to the wafer-like object 16. No heating elements are
illustrated in FIGS. 2-4 for the sake of clarity of the other
components.
[0026] The thermal processing chamber 10 is preferably cylindrical
to accommodate circular wafers, but need not be. Preferably, the
thermal processing chamber 10 comprises a bottom wall 20, a
cylindrical side wall 22 and a lid 24. A transfer slot 26 is
provided through a portion of the side wall so as to provide access
from outside the internal chamber 14 to within the internal chamber
14. Preferably, the transfer slot 26 is sized and shaped to
accommodate a robotic mechanism (not shown) that is usable for
loading and unloading a wafer-like object 16 from the platen 18.
Moreover, the transfer slot should accommodate the object size
(such as 200 mm or 300 mm semiconductor wafers) but may otherwise
be minimized to prevent excessive fluid flow therethrough when
open. In the case of processing semiconductor wafers it is often
desirable to provide an anaerobic environment within the internal
chamber 134, so a minimized transfer slot size is beneficial in
preventing unwanted flow of certain naturally occurring gases in
the environment (such as oxygen) from entering the internal chamber
14.
[0027] The transfer slot 26 is also preferably sealingly closable
by a chamber door 28 that is moveable between opened and closed
positions by a door closure mechanism 30 that is schematically
illustrated in FIGS. 2, 3 and 4. As illustrated in FIG. 1, the
chamber door 28 can be a substantially planar panel that closes a
transfer slot 26 that actually opens to the outside of the thermal
processing chamber 10 by way of a housing adapter 29 that adapts a
portion of the cylindrical chamber side wall 22 to provide a
rectangular opening capable of being closed by a planar chamber
door 28. The housing adapter 29 may be fabricated in any
conventional way without compromising the sealable nature of the
internal chamber 14. Otherwise, the chamber door 28 could be
arc-shaped to fit against the cylindrical outer surface of the side
wall 22, the side wall 22 could be otherwise adapted, or the
thermal processing chamber can be otherwise shaped. The door
closure mechanism 30 can comprise any known or developed mechanism
for opening and closing the chamber door 28, but preferably such
door closure mechanism 30 not only moves the chamber door 28
between opened and closed positions (i.e., to and from a position
in front of the transfer slot 26) but also is capable of urging the
chamber 28 toward chamber side wall 22 when the chamber door 28 is
positioned in a closed position in front of the transfer slot 26.
With the addition of a seal 32 provided within a perimetric groove
of the inside surface 33 of the chamber door 28, such a door
closure mechanism 30 assures a proper sealing of the internal
chamber 14 for processing when the chamber door 28 is closed. To
further facilitate this sealing arrangement, a perimetric flange 34
is also preferably secured to the side wall 22 about the transfer
slot 26 to provide an outer perimetric sealing surface 35 against
which the seal 32 contacts in the closed position of the chamber
door 28. One example of a suitable door closure mechanism 30 will
be described below with reference to another embodiment of the
present invention with the understanding that such mechanism could
also be applied in this embodiment. Moreover, other closure
mechanisms that include pneumatic, hydraulic, mechanical and
electromechanical drive devices may instead by used. It is
preferable, however, that the chamber door 28 be movable not only
between positions opening and closing the transfer slot 26, but
also movable toward and away from the side wall 22 to provide a
good sealing arrangement. Such movements can be imparted by
independent drive devices, or both such movements maybe controlled
by a single drive device or a combination of several drive
devices.
[0028] In accordance with one aspect of the present invention, the
side wall 22 is preferably a part of a double-wall structure (i.e.
having two or more spaced walls). In accordance with the embodiment
illustrated in FIG. 2, for example, the side wall 22 includes a
radially extending annular top portion 36, a radially extending
annular middle portion 38, and a radially extending annular bottom
portion forty. An outer wall 42 is further provided and connected
to the annular top, middle and bottom portions 36, 38 and 40,
respectively, to define the double-wall structure. The outer wall
42 may comprise an upper wall portion 44 and a lower wall portion
46 that may be fabricated independently from one another or
together. In this regard, the middle annular portion 38 may extend
all the way around the side wall 22, or may extend as a plurality
of arc portions around the side wall 22 or even as discrete posts
arranged about the side wall 22. More middle portions may be
provided, or they may be arranged in any pattern on the side wall
22. Alternatively, the middle annular portion 38 may be eliminated,
but it is preferred to provide mechanical structural strength to
the double wall structure.
[0029] In any case, the double wall structure defines an internal
wall cavity, that, as illustrated, is divided into an upper wall
cavity 48 and a lower wall cavity 50. The upper wall cavity 48 does
not extend completely around the internal chamber 14 as the
perimetric flange 34 defining the transfer slot 26 passes through
it at one portion of the side wall 22. The lower wall cavity 50
preferably extends completely about the internal chamber 14. The
outer wall 42 is preferably connected with the inner wall 22, and
the perimetric flange 34 is preferably connected with the side wall
22 by welding. Because of the temperatures experienced during
thermal processing of semiconductor wafers, for example, it is
desirable that the thermal processing chamber 10 comprise metal
materials, such as aluminum. Other materials are also contemplated,
such as stainless steel, and any other material suitable for the
temperature profile of the chamber 10. It is further preferable
that each of the components to be welded to one another be of
similar metals to facilitate such welding. The result is a
thermally and mechanically robust structure defining the thermal
processing chamber 10. Of course, for other applications, other
materials may be suitable and other connection techniques may be
utilized. For example, at lower temperatures, plastics may be
usable and adhesives may connect the components.
[0030] The chamber's bottom wall 20 is preferably fabricated
intregally with the side wall 22. However, it may otherwise be
formed separately and structurally secured to the side wall 22 by
any conventional means. In this embodiment, the bottom wall 20
comprises a single wall including an opening 52, preferably
centrally located, to facilitate the passage of components to and
from the platen 18 as will be described below. Supported about the
opening 52 on the chamber side of bottom wall 20 is a pedestal base
54. Preferably, the pedestal base 54 sits within an annular recess
56 formed within the bottom wall 20 from the internal chamber side
so that conventional bolts 58 can secure the pedestal base 54 to
the bottom wall 20. To effectively seal the internal chamber 14, a
seal ring 60 is provided between a lower surface 62 of the pedestal
base 54 and the bottom of the annular recess 56 so that as the
pedestal base 54 is mounted via the bolts 58, a good sealing
relationship is established. To facilitate this construction and to
accommodate heat transfer abilities of this portion, the central
portion 64 of the bottom wall 20 is preferably made thicker.
[0031] Also in the thicker central portion 64 of bottom wall 20, an
exhaust passage 66 is preferably defined for removal of process
fluids from within the internal chamber 14 as appropriate depending
on the particular application. In particular, the exhaust channel
66 is preferably annular as provided by an annual recess 68 of the
central portion 64 that is open to the internal chamber side
thereof. One or more passages (not shown) are also provided
extending through the remainder of the thickness of the central
portion 64 so that exhaust fluids can be drawn from the exhaust
channel 66 outside of the internal chamber 14 by conventional
tubing and fittings or the like. To close the chamber side of the
exhaust channel 66, a removable exhaust plate 70 is provided having
an arrangement of orifices 74 provided in any desired pattern along
the exhaust plate 70. Thus, by fluidly connecting the exhaust
channel 66 to an exhaust system, fluid can be drawn from the
internal chamber 14 through the orifices 72 into the exhaust
channel 66 and out of the thermal processing chamber 10. By using a
removable exhaust plate 70, the size of the orifices 72 can easily
be varied depending on any particular application of the thermal
processing chamber 10 by merely replacing the exhaust plate 70 with
another of appropriate size orifices 72. The exhaust plate 70 is
preferably fitted within a stepped portion of the annular recess 68
and is preferably secured in place by a plurality of fasteners 76
having head portions that overlap at least a portion of the exhaust
plate 70 when secured in position. Preferably, the fasteners 76 are
threaded within holes of the central portion 64 at appropriate
locations to do so.
[0032] Also provided within the central portion 64 of the bottom
wall 20, is a cooling channel 78. The cooling channel 78 also
preferably comprises a recess made into the central portion 64 of
bottom wall 20, but the recess is open to the outside of the bottom
wall 20. The cooling channel 78 preferably substantially forms a
circular channel (as viewed in a plan view) that is concentric with
the opening 52. That is, the cooling channel 78 preferably stops
short of defining a full circle so that one end of the cooling
channel 78 can be utilized as an inlet and its other end can be
used as an outlet. To close the cooling channel 78 from the
outside, a plate 80 is secured to the central portion 64 of the
bottom wall 20 so as to sealingly cover the cooling channel 78 and
to provide inlet and outlet passages (not shown) by which -the
cooling channel 78 can be appropriately fluidly connected with
input and outlet lines of a cooling system in any conventional way.
(Note that the figures need to show the plate 80).
[0033] Also provided through the central portion 64 of the bottom
wall 20 are a number of (preferably three) passages 82 (only one
shown in FIG. 2) that accommodate reciprocal movement of lift pins
84. In addition to facilitating the reciprocal movement of the lift
pins 84, the passages 82 must permit this movement while
effectively sealing the internal chamber 14. To do this, seal rings
86 are preferably installed within a recess provided from the
outside of the central portion 65 around the passages 82 for
providing sealing sliding engagement with the lift pins 84. Such
seal rings 86 may be secured in place by mounting plates retained,
in turn, by a plurality of fasteners or any other conventional
means.
[0034] The passages 82, and thus the lift pins 84, are preferably
arranged concentrically (but need not be) about the opening 52 so
as to extend within passages 88 (only one shown in FIG. 2) provided
entirely through the thickness of platen 18. The platen 18, which
is directly supported by the pedestal base 54 provides a support
surface 90 onto which a wafer-like object 16 can be positioned in
thermal transfer contact. The lift pins 84 are movable from a
position where their tips 85 lie below the support surface 90 so as
not to interfere with this thermal transfer contact. Lift pins 84
are movable as driven by a reciprocal drive mechanism 92 so as to
be movable to positions where their tips 85 are located above the
support service 90 so as to move the wafer-like object 16 to a
non-thermal transfer contact position. That is, movement of the
lift pins 84 move the wafer-like object 16 from its thermal
transfer contact. This position is designated as the cooling state
of the thermal processing chamber 10 as explained further below.
The degree of lift pin 84 movement is dependent on the cooling
needs and fluid flow characteristics of the internal chamber 14. In
any case, it is considered that the object 16 be out of thermal
transfer contact with platen 18 when it is moved to a cooling
position.
[0035] To accomplish movement of lift pins 84 simultaneously, each
lift pin 84 is preferably connected to a common element, such as a
plate (not shown) so that a drive mechanism 92 can move the single
element or plate and thus each lift pin 84 together. The drive
mechanism 92 can comprise any known or developed mechanism capable
of linear movement, such as a lead screw mechanism driven by a
stepper motor. It is further preferable that each lift pin 84
further include an internal passage 94 that can be conventionally
connected with a vacuum line or system so as to draw vacuum at
openings through tips 85 for holding the wafer-like object 16
against the tips 85.
[0036] As will be further described below, the platen 18 includes
other components that provide heat generation and temperature
feedback control. In this regard, the opening 52 through the bottom
wall 20 facilitates passage of a wiring conduit 94 and portions of
any number of temperature sensing devices 96 that may be embedded
within the platen 18. Temperature sensing devices may include
conventional RTD sensors or thermocouple devices. Such temperature
sensing devices can be used to provide temperature information of
the platen 18 at various locations and depths within platen 18 and
are connected with a control circuit so as to control the
generation of heat by a heating mechanism within platen 18 in a
conventional manner. The control mechanism itself does not form a
particular part of the subject application and can be provided in
any known or developed manner consistent with the basic operation
of controlling the heat generated based upon temperature sensing
information.
[0037] Closing off the top of the internal chamber 14 is the lid
24. Lid 24 preferably comprises a top wall 98 and a cover plate
100. The top wall 98, in the case of a cylindrical thermal
processing chamber 10, also includes axially extending circular
outer portion 102, circular middle portion 104 and circular inner
portion 106. The result is an annular outer chamber 108, an annular
middle chamber 110 and a circular inner chamber 112. Each of these
chambers are closed off by the cover plate 100 which is
conventionally secured to the top wall 98 by conventional fasteners
114, such as bolts. The lid 24, comprising both the top wall 98 and
cover plate 100, is connected to the top of the side wall 22 also
by a plurality of conventional fasteners 1 16 such as bolts. A
further seal 118 is also preferably provided within a recess of a
top surface of the side wall 22 so as to provide an effective seal
of the internal chamber 14 when the lower edge surface of top wall
98 is secured in place by the fasteners 116. By way of the seal
118, seal ring 60, door seal 32 and lift pin seals 86, the internal
chamber 14 is effectively provided for thermal processing
therein.
[0038] For reasons discussed in the operation of the thermal
processing chamber 10 below, the outer chamber 108 can fluidly
communicate with the internal chamber 14 by way of a series of
orifices 120. Likewise, the inner chamber 112 can fluidly
communicate with the internal chamber 14 by orifices 122. It is
also desirable to provide fluid communication between the outer
chamber 108 and inner chamber 112 with supply lines provided
outside of the thermal processing chamber 10. To do this,
conventional fluid lines and fittings can be conventionally
utilized to connect with fluid sources and supply fluid through
passages (not shown) through the cover plate 100 at appropriate
locations for fluid to enter the outer and inner chambers 108 and
112, respectively.
[0039] As noted above, the platen 18 itself preferably comprises a
heater mechanism for providing heat transfer to a wafer-like object
16 when supported on the surface 90 thereof. Preferably, the
heating mechanism will supply heat to allow effective heat transfer
to the entire wafer-like object 16. As shown in FIGS. 5 and 6, one
specific example of a heater mechanism is illustrated which
comprises a heater cable 130 that is cast within the platen 18 to
provide a pedestal heater. The cable heater 130 is illustrated in
FIG. 5 as having a spiral pattern so that heat can be generated and
distributed over the entire surface 90 of the platen 18. That way,
effective heat transfer can be provided to a wafer-like object 16
when supported in a heat transfer contact position. The spiral
pattern may be modified depending on the desired application and
heat transfer requirements, and many different patterns can be
developed. Moreover, multiple zones may be created for affecting
the wafer-like object 16 differently at different portions thereof.
In this regard, more than one heating element may be utilized. As
illustrated in FIG. 6, a framework 132 may be utilized within the
body of the platen 18 for accurately controlling the positioning of
such a heater cable 130 so as to define its pattern during the
casting process of the pedestal heater. Such framework 132 may
comprise any number of components and features for the purpose of
precisely defining the desired pattern including one or more
heating elements.
[0040] Alternative heater devices can comprise any known or
developed film heater, such as the type including a film layer or
mica layer having a heater circuit printed on a surface thereof.
Such a film heater could be connected on the top surface of the
platen, in which case the heater would provide the wafer-like
object support surface instead of the top surface of the platen
itself. As yet another alternative, a heater circuit may be printed
directly onto the top or bottom surface of a platen. Or as yet
another alternative, the heating device disclosed in copending U.S.
patent application Ser. No. 09/035,628, filed Mar. 5, 1998, and
owned by the assignee of the subject application, could also be
utilized. In any case, appropriate passages can be provided through
the platen to provide the electrical connections and any other
electrical or mechanical needs. Moreover, any number of temperature
sensors 96 can be provided throughout and at various levels within
the platen 18 for monitoring and providing feedback information to
a control circuit for driving the heater mechanism.
[0041] The thermal processing chamber 10 described above is
designed in particular for enhanced performance as a thermal
processing chamber that facilitates both heating and cooling of a
wafer-like object 16 within the internal chamber 14. Moreover, the
thermal processing chamber 10 is designed to enhance thermal
uniformity of the chamber so that heat is transferred to a
wafer-like object 16 from a heater within or upon the platen 18 in
a precisely uniform manner. In the production of many products,
such as semiconductor wafers with dielectric material (described
above in the Background section), it is important that the entire
object be uniformly heated so that exact processing of the entire
object surface is thermally treated. For example, in the case of
processing a semiconductor wafer with a high temperature curing
material, the dielectric material is cured by raising the entire
wafer surface to a temperature of 200.degree. or more for a
specific length of time. As also discussed above in the Background
section of this application, it has been discovered that the design
of the chamber 10 and its components affect such thermal
uniformity. That is, the design of the side walls, bottom wall,
lid, pedestal and platen all contribute to such thermal uniformity
in either a positive or negative way. Moreover, the fact that the
chamber 10 is to be utilized as both a heating and cooling chamber
exacerbates this problem. That is, the effect of cooling the
chamber between heating operations affects the temperature of the
components of and within the thermal processing chamber so as to
affect its next use in a heating operation and thus its thermal
uniformity in that next operation.
[0042] In accordance with the present invention, the design of the
thermal processing chamber 10 and method of using it in processing
a wafer-like object 16 include a number of features and steps that
have been developed for the purpose of enhancing the thermal
uniformity of the heating step, even at high temperature
processing.
[0043] One such feature is the provision of the double side wall
structure. In particular, this design provides a good heat
conductive inside surface by way of the inner surface of side wall
22 and provides an outer wall 42 that is thermally insulated from
the side wall 22 thus, the interior surface of the side wall 22 is
insulated from the effects of temperatures outside of the chamber,
and the external surface 42 is likewise insulated from the side
wall 22. The particular advantage of this construction is that the
inside surface of side wall 22 can be heated and remain heated
without substantial cooling between cycles of operation. Good heat
conductivity along all internal surfaces is advantageous, and it is
desirable to keep the internal surfaces as hot as possible (up to
the process temperature) to enhance thermal uniformity.
[0044] Another specific feature provided for this purpose is the
inner and outer chambers 108 and 112, respectively, formed within
the lid 24. Not only do these chambers, along with the middle
chamber 110, provide an insulating effect in a similar manner to
the double side wall construction, the chambers can be utilized for
circulating gases throughout the internal chamber 14.
Advantageously, the inner chamber 112 can be utilized to supply
cooling gas for cooling the wafer-like object 16 after the heating
step is conducted and while the wafer-like object 16 is moved to a
cooling state by extension of lift pins 84 by taking the wafer-like
object 16 out of thermal transfer contact with the platen 18. With
the wafer-like object 16 supported out of thermal transfer contact,
cooling gas can be circulated from inner chamber 112 through
orifices 122 about the wafer-like object 16 within the internal
chamber 14 and exhausted through the exhaust channel 66.
Circulation of the cooling gas would have little effect on the
temperature of the interior surface of the side wall 22 as its flow
would be primarily directed across the wafer-like object 16, around
the platen 18 and into the exhaust channel 66.
[0045] Another feature provided to enhance the uniformity is the
gas cooling channel 78 defined within the central portion 64 of the
bottom wall 20. The gas cooling channel 78, however, is not for the
purpose of maintaining heat, but is instead to provide a cooling
function of the central portion 64 of bottom wall 20. Because heat
is generated by the platen 18, heat is conducted through the
pedestal base 54 to the central portion 64. The cooling of the
central portion 64 permits the remainder of the bottom wall 20 and
the side wall 22 to be maintained at a sufficiently high heat level
but not to permit the central portion 64 to become overheated. An
overheated condition could result in the destruction of the seals
60 and 86 which are necessary to maintain the internal chamber 14.
Thus, the gas cooling channel 78 balances the heat extending across
the bottom wall 20 to further assist in the thermal uniformity of
the thermal processing chamber 10. Of course, other configurations
for the gas cooling channel 78 may be designed based upon the
particular cooling requirements of a particular application and the
degree of heat conducted to the bottom wall 20. The use of cooling
gas provides a significant advantage over liquid cooling techniques
in that liquid would impinge on the interior surface of the cooling
channel 78 and cause it to cool to a greater degree. Moreover, such
a liquid could be caused to boil by the high temperature of the
bottom wall 20 which itself could have many adverse effects within
a cooling liquid supply system.
[0046] These features and others noted below contribute to the
achievement of a thermal processing chamber within which efficient
and effective heating and cooling of a wafer-like object can take
place. In one aspect, this is done by carefully controlling the
flow of heat (radiatively, convectively and conductively) as well
as the composition of the gases in the processing environment.
Radiative heat transfer control is achieved by maintaining the
surfaces "visible" to the wafer-like object as close to the
processing temperature as possible. Convective heat transfer
control is achieved by establishing the proper gas flow pattern on
the exposed surface of the wafer-like object. This flow pattern may
be called upon to correct for other nonuniformities in the process.
Conductive heat transfer control is achieved by ensuring uniform
contact between the wafer-like object and the heating surface and
by ensuring that the contacting surface temperature is as uniform
as possible. Control of the gas composition in the processing
environment is achieved by isolating the processing environment
from the ambient environment and by maximizing the flexibility and
control of gas flow in the processing environment.
[0047] In accordance with the present invention, the surfaces
visible to the wafer-like object are preferably maintained close to
the processing temperature through the use of three essential
features. First, the chamber wall incorporates a double walled
design that allows superior thermal isolation of the inner surface
of chamber wall 22 from the much cooler outer surface of outer wall
42. Second, the cooling required to maintain chamber seals, such as
seals 60 and 86, within their thermal operating ranges is
accomplished by the use of an internal gas cooling channel 78
rather than a liquid cooling channel. Due to their generally lower
heat capacity than liquids, gases allow more precise and reliable
temperature control by permitting finer control of the heat
transfer rate. The thermal limit of liquids also constrains their
boiling point, which can create safety as well as reliability
hazards. The thermal limit of gases allows the chamber wall to
operate at higher temperatures, reducing heat transfer from the
wafer-like object and, therefore, improving temperature uniformity.
Third, careful control of the heat transfer from the pedestal
heater, comprising the platen 18 and its heating element, to the
chamber bottom wall 20 and side walls 22 prevent temperature
gradients along the walls, improving the uniformity of the visible
surfaces. This control may be achieved by reducing the cross
sectional area of conductive paths or by increasing their lengths.
Control may also be achieved by minimizing emissivity of the heater
surface thereby minimizing the radiation between the heater and the
chamber wall.
[0048] The present invention promotes the development of the proper
convective gas flow through the use of three elements. First, the
use of separately variable inner and outer gas introduction
patterns above the wafer-like object (see FIG. 3) allow the ratio
and magnitude of the flows to be adjusted to achieve the optimum
flow pattern on the wafer-like object. This can be done by
appropriate sizing of the respective orifices 120 and 122 and/or by
otherwise controlling gas supply (i.e. by pressure). Second, the
use of a chamber door 28 minimizes gas disturbances during transfer
of the wafer-like object 16, minimizing the time required to
establish the required gas flow. Third, the use of removable
exhaust plate 72 simplifies the investigation of widely varying
exhaust patterns, promoting the achievement of the optimum gas flow
environment.
[0049] The separate inner and outer gas introduction patterns allow
sophisticated purging routines to be developed that can create the
proper gas composition in the minimum amount of time. The removable
exhaust plate 72 assists in establishing the optimum gas flow
pattern.
[0050] To ensure superior conductive heat transfer control, the
present invention preferably employs a pedestal-style heater that
contacts the cooler chamber bottom wall 20 at a single, preferably
central point. This point of contact may then be carefully
minimized to reduce losses to the chamber, improving pedestal
surface uniformity. Heater surface uniformity is also improved by
maximizing the radiative emissivity between the wafer-like object
and the contacting heater surface while minimizing the radiative
emissivity between the other heater surfaces and the chamber wall.
The radiative emissivity of the heater surfaces may be controlled
by chemical (e.g. anodization) or mechanical (e.g. ball peening)
treatment. In particular, the surface or surfaces visible to the
wafer-like object may be anodized while the other surfaces are left
with a finely machined finish. To ensure good contact between the
wafer-like object and the heater surface, channels on the pedestal
surface are evacuated, the resulting pressure difference across the
wafer-like object driving it against the heater surface.
[0051] The operation of a complete cycle and method of using the
thermal processing chamber 10 in accordance with the present
invention is described as follows with reference to FIGS. 2, 3 and
4. Starting with a transfer state of the thermal processing chamber
10 illustrated in FIG. 4, with the chamber door 28 in its open
position, a wafer-like object 16 is positioned onto the tips of
pins 84 (as they are extended in the transfer position) by way of a
conventional robotic handling device that is capable of grasping
and moving such a wafer-like object 16 and loading it onto the pins
84. Such robotic handlers are well-known, including those of the
type that move a wafer within the x and y plane, as well as those
which move a wafer in x, y and z directions to facilitate wafer
loading the removal. The purge gas is activated at this time to
minimize entry of atmospheric gases into the processing chamber.
Preferably, gas is circulated through the internal chamber 14 and
out through the exhaust channel 66 as supplied through both the
inner chamber 112 and the outer chamber 108. Only one or the other
of the inner and outer chambers 112 and 108, respectively, may be
used for this if desired, or, the middle chamber 110 may be used
instead or in combination with one or both, provided that a proper
supply and orifices are included.
[0052] Suitable purge gases are preferably those that do not
adversely affect the particular process of a particular
application. For many applications, inert gases are preferred.
[0053] After a wafer-like object 16 is transferred onto the pins
84, as shown in FIG. 4, the pins 84 are lowered to configure the
thermal processing chamber 10 in a heating state, as illustrated in
FIG. 2. The heating state is defined by the wafer-like object 16
being in thermal transfer contact with the surface 90 of the platen
18, with lift pins 84 retracted and the chamber door 28 in a closed
sealed position. In this state, the wafer-like object 16 can be
thermally processed by heat generated from platen 18 and
transferred to the wafer-like object 16. For the many reasons
discussed above, thermal uniformity of the heating process is
achieved in accordance with the present invention. During this
heating step, purge gas may be provided through one of or both of
the inner and outer chambers 112 and 108 within lid 24 for
circulation within the internal chamber 14 and exhausted through
exhaust channel 66.
[0054] Once the heating operation is fully conducted, and while the
chamber door 28 remains closed, the wafer-like object 16 can be
elevated to a position where it is no longer in thermal transfer
contact with the platen 18. This is accomplished by extending the
lift pins 82 so that the tips thereof extend a sufficient distance
beyond the support surface of platen 18. The wafer-like object may
then be cooled by the flow of gases from one of or both of the
inner and outer chambers 112 and 108 within lid 24. When cooling
has been accomplished, the door 28 may then be opened to permit
removal by the object transfer mechanism.
[0055] With reference to FIGS. 7 and 8, another embodiment of a
thermal processing chamber 200 is described as follows. To the
extent that the components and construction of thermal processing
chamber 200 are similar to those of the thermal processing chamber
10, their description and functionality will not be described in
detail again, and the following description is directed to the
differences between them. It is further understood that any of such
differences may be incorporated within the thermal processing
chamber 10 independently or in any combination with one
another.
[0056] In the thermal processing chamber 200, a bottom wall 220
further includes an axially extending annular outer portion 221 and
an axially extending annular middle portion 223 that together with
stepped edge of the central portion 264 provide mounting surfaces
for a spaced outer bottom wall 265. Like the outer side wall 42,
the outer bottom wall 265 provides part of a double bottom wall
structure with an increase in thermal isolation due to the
insulating capability of the structure and an increase in
structural strength. The outer bottom wall 265 may be welded or
otherwise connected with the bottom wall 220 in the same manner as
the side wall construction, and the portions 221 and 223 may also
be modified as suggested above with regard to the side wall. As
illustrated, an annular outer bottom chamber 267 and an annular
inner bottom chamber 269 are thereby defined.
[0057] The bottom wall 220 is also modified in that the exhaust
channel 266 is moved inboard of the lift pins 284 and the cooling
channel 278 is moved further inboard to be positioned under the
pedestal base 254. The removable exhaust plate 270 is positioned to
cover the exhaust channel 278 and to partially extend between the
lower surface of the pedestal base 254 and the surface of a stepped
down portion of the central portion 264 of the bottom wall 220
adjacent to the provision of the seal ring 260. By moving the
exhaust channel 278 closer to the pedestal base 254, the
circulation of fluid within the internal chamber 214 is improved
and the purge efficiency of the internal chamber 214 is improved by
reducing circulation of the gas in the region between the exhaust
channel 266 and the pedestal base 254. Another advantage of this
design is that the seal ring 260 is spaced further in a heat
transfer path from the platen 218 without spacing the platen 218
further from the bottom wall 220, and the added distance further
protects the seal ring 260 from thermal breakdown. By also
positioning the seal ring 260 closer in a heat transfer path to the
cooling channel 278, it is further protected. As also shown in FIG.
8, a temperature sensor 296 may instead be extended through the
bottom wall 220, and in particular through its central portion 264.
As this provides another opening through the bottom wall 220 into
the internal chamber 214, a sealing ring 297 of any conventional
construction is also provided between the temperature sensor 296
and the central portion 264.
[0058] Another difference of the thermal processing chamber 200 is
in the construction of the lid 224. A double wall structure is
provided in a similar sense as that of lid 24, but axially
extending middle annular portion 306 is provided with one or more
lower sections that do not extend to contact the cover plate 300 so
as to provide fluidic communication between the middle and inner
lid chambers 310 and 312, respectively. That is, the middle and
inner chambers 310 and 312 act as a single chamber through which
cooling gas can be dispensed into the internal chamber 214. As
such, many more orifices 322 can be provided and at different
location for a different distribution of cooling gas into the
internal chamber 214. The ability to change the distribution
pattern is thus enhanced, and gas flow uniformity against a
wafer-like object 216 may be improved for in situ wafer
cooling.
[0059] Yet another difference of the thermal processing chamber 200
is in the connection of the lid 224 to the upper edge of the side
wall 222. By providing an annular step 301 at the peripheral edge
of the top wall 298, the internal surface of the top wall 298 is
positioned closer to the wafer-like object 216 so as to reduce
circulation and improve purging efficiency and to bring the
orifices 322 closer to the wafer-like object 216 to improve cooling
performance.
[0060] Also illustrated in FIG. 7 is a door closure mechanism
usable in accordance with any thermal processing chamber of the
present invention that provides vertical and horizontal movement of
a chamber door. The illustrated chamber door 228 is substantially
planar and is adapted to the thermal processing chamber 210 by a
housing adapter 229. A door closure mechanism 330 includes a pair
of door actuators 332, themselves each comprising a conventional
drive device, such as a pneumatic cylinder (not shown) and a first
slide component 334. A cooperating slide component 336 is connected
with a door frame 338. The movable portion of the drive device
(e.g. a piston of a cylinder) is connected with the slide component
336 to move the door frame 338 vertically as guided by the first
slide component 334. The chamber door 328 is itself operatively
connected to the door frame 338 by way of a known four-bar
mechanism (not shown) that permits the chamber door 328 to move
horizontally. To cause this horizontal movement, a door stop 340 is
positioned above the upper edge of the chamber door 328, the door
stop 340 having a first cam surface (not shown) that cooperates
with the upper edge of the chamber door 328 (or a roller or other
element positioned there). By this arrangement, upward movement of
the chamber door 328 after an initial engagement of the door stop
340 and chamber door 328 in translated into horizontal movement of
the chamber door 328. This horizontal movement is utilized in
providing a suitable force for sealing the chamber door 328 to the
chamber side wall 222 with seal 232 therebetween.
[0061] One specific apparatus including any thermal processing
chamber disclosed or suggested in accordance with the present
invention is illustrated in FIG. 9. Specifically, a cluster
apparatus 400 is shown that includes a thermal processing chamber
402 among a number of other processing stations 404, 406, 408 and
410. For the processing of semiconductor wafers, for example, other
stations may be coating, dispensing, curing or wafer storing
stations. A wafer transfer mechanism 412 may also be provided. Such
other stations and transfer mechanisms are well known and can be
varied depending of the particular application. One such cluster
apparatus to which the present invention is particularly applicable
for the processing of semiconductor wafers is a cluster apparatus
that is commercially available from the FSI International, Inc.,
the assignee of the present invention, under the trade designation
"Calypso", wherein the thermal processing chamber of the present
invention can be incorporated as one of its stations for
semiconductor wafer processing. As noted above, it is also
contemplated that any apparatus having a thermal processing chamber
in accordance with the present invention may also be provided in
the form of a stand-alone apparatus, in which case the thermal
processing chamber could be used alone or in combination with any
other apparatus.
[0062] Other embodiments of this invention will be apparent to
those skilled in the art upon consideration of this specification
or from practice of the invention disclosed herein. Various
omissions, modifications, and changes to the principles and
embodiments described herein may be made by one skilled in the art
without departing from the scope and spirit of the present
invention which is indicated by the following claims.
* * * * *