U.S. patent application number 09/764036 was filed with the patent office on 2001-06-21 for integrated bake and chill plate.
Invention is credited to Bolandi, Hooman, Tepman, Avi.
Application Number | 20010003901 09/764036 |
Document ID | / |
Family ID | 23488823 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010003901 |
Kind Code |
A1 |
Bolandi, Hooman ; et
al. |
June 21, 2001 |
Integrated bake and chill plate
Abstract
A method and apparatus for providing integrated bake and chill
thermal cycling applied to a material substrate is provided. The
apparatus is a module comprising an integrated bake and chill plate
with one or more fluid channels in a generally spiraling
arrangement. The fluid channels have inlets and outlets near the
center and perimeter of the integrated bake and chill plate.
Additionally, the fluid channels can have microchannels through
portions thereof. The module can also comprise one or more
thermoelectric devices, a thermally conductive plate on which the
substrate directly or indirectly rests, a printed circuit board,
and a variable power source. The integrated bake and chill plate,
the thermally conductive plate and the thermoelectric devices are
all in thermal contact with each other. The thermoelectric devices
are also in electrical contact with the variable power source and
comprise a top plate, a bottom plate, a support positioned between
the top and bottom plates, and one or more copper pads beneath the
bottom plate for establishing electrical contact. The module bakes
and chills a substrate by flowing fluids of different temperatures
through the generally spiraling fluid channels and adjusting the
temperature of the thermoelectric devices according to a
preprogrammed cycle. Different fluid flow patterns can be chosen
where fluid enters near the center of the integrated bake and chill
plate and drains near the perimeter, where fluid enters near the
perimeter and drains near the center, or where the two patterns are
combined.
Inventors: |
Bolandi, Hooman; (Santa
Clara, CA) ; Tepman, Avi; (Cupertino, CA) |
Correspondence
Address: |
Patent Counsel
APPLIED MATERIALS, INC.
M/S 2061 Legal Affairs Department
3050 Bowers Avenue
Santa Clara
CA
95054
US
|
Family ID: |
23488823 |
Appl. No.: |
09/764036 |
Filed: |
January 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09764036 |
Jan 16, 2001 |
|
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|
09377365 |
Aug 18, 1999 |
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Current U.S.
Class: |
62/3.7 ;
62/3.3 |
Current CPC
Class: |
F25B 21/04 20130101;
F28D 9/04 20130101; H01L 21/67103 20130101; H01L 21/67109
20130101 |
Class at
Publication: |
62/3.7 ;
62/3.3 |
International
Class: |
F25B 021/02 |
Claims
What is claimed is:
1. An integrated bake and chill plate comprising: an upper surface
and a lower surface and one or more fluid conducting channels
interposed between said upper and lower surfaces, at least one of
said surfaces composed of thermally conducting material; said fluid
conducting channel having a first and a second end, said ends
comprising either fluid-inlets or fluid-outlets for conducing fluid
into and out of said channels; said channel interposed between said
upper and lower surfaces such that one end of said channel extends
from generally the center of said plate to the other end of said
channel generally positioned at the perimeter of said plate in a
generally spiraling arrangement.
2. The integrated bake and chill plate of claim 1 further
comprising a plurality of fluid conducting channels, said channels
positioned generally parallel to one another and extending
generally from the center of said integrated bake and chill plate
at one end to generally the perimeter of said integrated bake and
chill plate at the other end in a generally spiraling
arrangement.
3. The integrated bake and chill plate of claim 1 wherein said
fluid conducting channel of said integrated bake and chill plate
further comprises a plurality of microchannels extending through
portions of said fluid conducting channel.
4. The integrated bake and chill plate of claim 3 further
comprising a plurality of fluid conducting channels, said channels
positioned generally parallel to one another and extending
generally from the center of said integrated bake and chill plate
at one end to generally the perimeter of said integrated bake and
chill plate at the other end in a generally spiraling
arrangement.
5. A thermal cycling module comprising: an integrated bake and
chill plate comprising an upper surface and a lower surface and one
or more fluid conducting channels interposed between said upper and
lower surfaces, at least one of said surfaces composed of thermally
conducting material; said fluid conducting channel having a first
and a second end, said ends comprising either fluid-inlets or
fluid-outlets for conducing fluid into and out of said channels;
said channel interposed between said upper and lower surfaces such
that one end of said channel extends from generally the center of
said plate to the other end of said channel generally positioned at
the perimeter of said plate in a generally spiraling arrangement;
and one or more thermoelectric devices in thermal contact with said
integrated bake and chill plate and each individually removably
attached to said integrated bake and chill plate with a connector
means.
6. The thermal cycling module of claim 5 wherein said fluid
conducting channel of said integrated bake and chill plate further
comprises a plurality of microchannels extending through portions
of said fluid conducting channel.
7. The thermal cycling module of claim 6 wherein said integrated
bake and chill plate comprises a plurality of fluid conducting
channels, said channels positioned generally parallel to one
another and extending generally from the center of said integrated
bake and chill plate at one end to generally the perimeter of said
integrated bake and chill plate at the other end in a generally
spiraling arrangement.
8. The thermal cycling module of claim 5 further comprising a
thermally conductive plate in thermal contact with said
thermoelectric devices.
9. The thermal cycling module of claim 8 further comprising a first
washer, a second washer and a connection means having a top, said
connection means removably attaching said thermally conductive
plate to said integrated bake and chill plate and said first washer
being placed around said connection means and below said top of
said connection means and said second washer being placed around
said connection means and between said first washer and said
thermally conductive plate.
10. The thermal cycling module of claim 8 wherein said thermally
conductive plate further comprises a bottom surface and vertical
extensions integrally connected to said bottom surface of said
thermally conductive plate and wherein said integrated bake and
chill plate further comprises a top surface and vertical ribs
integrally connected to said top surface of said integrated bake
and chill plate; said vertical extensions of said thermally
conductive plate being in thermal contact with said vertical ribs
of said integrated bake and chill plate.
11. A thermal cycling module of claim 6 further comprising a
thermally conductive plate in thermal contact with said
thermoelectric devices.
12. The thermal cycling module of claim 11 further comprising a
first washer, a second washer, and a connection means having a top,
said connection means removably attaching said thermally conductive
plate to said integrated bake and chill plate and said first washer
being placed around said connection means and below said top of
said connection means and said second washer being placed around
said connection means and between said first washer and said
thermally conductive plate.
13. The thermal cycling module of claim 11 wherein said thermally
conductive plate further comprises a bottom surface and vertical
extensions integrally connected to said bottom surface of said
thermally conductive plate and wherein said integrated bake and
chill plate further comprises a top surface and vertical ribs
integrally connected to said top surface of said integrated bake
and chill plate; said vertical extensions of said thermally
conductive plate being in thermal contact with said vertical ribs
of said integrated bake and chill plate.
14. A method of baking and chilling a material substrate, the
method comprising: placing the substrate in thermal contact with a
thermally conductive plate; exchanging heat between the thermally
conductive plate and one or more thermoelectric devices; exchanging
heat between the thermoelectric devices and an integrated bake and
chill plate; flowing thermally conductive fluids of differing
temperatures through the integrated bake and chill plate in a
generally spiraling arrangement; calculating a control signal based
on a desired process parameter; changing a flow of electricity
through the thermoelectric device in accordance with the calculated
control signal; and changing the flow of the fluids in accordance
with the calculated control signal.
15. The method of claim 14 wherein fluids flow from generally the
center of the integrated bake and chill plate to generally the
perimeter of the integrated bake and chill plate in a generally
spiral arrangement.
16. The method of claim 14 wherein fluids flow from generally the
perimeter of the integrated bake and chill plate to generally the
center of the integrated bake and chill plate in a generally spiral
arrangement.
17. The method of claim 14 wherein some fluids flow from generally
the perimeter of the integrated bake and chill plate to generally
the center of the integrated bake and chill plate in a generally
spiral arrangement and the remaining fluids flow from generally the
center of the integrated bake and chill plate to generally the
perimeter of the integrated bake and chill plate in a generally
spiral arrangement.
18. A thermoelectric device comprising: a top plate having an upper
surface and a lower surface; a bottom plate having an upper surface
and a lower surface; a support interposed between and in thermal
contact with the lower surface of said top plate and the upper
surface of said bottom plate; wherein said top plate, said bottom
plate and said support define a passageway therethrough to accept a
connecting means; and one or more electrically conductive pads
positioned below and in thermal contact with the lower surface of
said bottom plate.
19. The thermoelectric device of claim 18 wherein said top plate
and said bottom plate are composed of a ceramic material.
20. The thermoelectric device of claim 18 wherein said support is
composed of a copper material.
21. The thermoelectric device of claim 18 wherein said pad is
composed of a copper material.
22. A thermal cycling module for baking and chilling a material
substrate, the module comprising: a integrated bake and chill plate
having an upper surface and a lower surface and one or more fluid
conducting channels interposed between said upper and lower
surfaces, at least one of said surfaces composed of thermally
conducting material; said fluid conducting channel having a first
and a second end, said ends comprising either fluid-inlets or
fluid-outlets for conducing fluid into and out of said channels;
said fluid conducting channel having a plurality of microchannels
extending therethrough; said fluid conducting channel interposed
between said upper and lower surfaces such that one end of said
channels extends from generally the center of said integrated bake
and chill plate to the other end of said channel generally
positioned at the perimeter of said integrated bake and chill plate
in a generally spiraling arrangement; one or more thermoelectric
devices in thermal contact with said integrated bake and chill
plate and each individually removably attached to said integrated
bake and chill plate with a connecting means; said thermoelectric
device having a top plate having an upper surface and a lower
surface, a bottom plate having an upper surface and a lower
surface, a support interposed between and in thermal contact with
the lower surface of said top plate and the upper surface of said
bottom plate, and one or more electrically conductive pads
positioned below and in thermal contact with the lower surface of
said bottom plate; wherein said top plate, said bottom plate and
said support define a passageway therethrough to accept a
connecting means; a thermally conductive plate in thermal contact
with said thermoelectric device; and a variable power supply in
electrical contact with the thermoelectric devices.
23. The thermal cycling module of claim 22 further comprising a
printed circuit board in electrical contact with the variable power
supply and thermoelectric devices.
24. The thermal cycling module of claim 24 further comprising a
connection means having a top, a first washer, and a second washer,
said connection means removably attaching said printed circuit
board to said integrated bake and chill plate and said first washer
being placed around said connection means and below said top of
said connection means and said second washer being placed around
said connection means and between said first washer and printed
circuit board.
25. The thermal cycling module of claim 22 further comprising a
first washer, a second washer, and a connection means having a top,
connection means removably attaching said thermally conductive
plate to said integrated bake and chill plate and said first washer
being placed around said connection means and below said top of
said connection means and said second washer being placed around
said connection means and between said first washer and said
thermally conductive plate.
26. The thermal cycling module of claim 22 wherein said thermally
conductive plate further comprises a bottom surface and vertical
extensions integrally connected to said bottom surface of said
thermally conductive plate and wherein said integrated bake and
chill plate further comprises a top surface and vertical ribs
integrally connected to said top surface of said integrated bake
and chill plate; said vertical extensions of said thermally
conductive plate being in thermal contact with said vertical ribs
of said integrated bake and chill plate.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to methods and apparatuses
for providing integrated bake and chill thermal cycling applied to
material substrates. More particularly, it relates to an integrated
bake and chill thermal cycling module having improved fluid
channels and structural design for providing controlled thermal
cycling of material substrates such as semiconductor wafers and
flat panel displays.
BACKGROUND OF THE INVENTION
[0002] Certain stages of semiconductor manufacturing require baking
the semiconductor substrate material, such as a wafer, and
subsequently chilling it. For example, the photoresist processing
state of semiconductor manufacturing requires such baking and
chilling, or thermal cycling. In order to produce high quality
wafers suitable for present integrated circuit applications, the
temperature of the wafer during this thermal cycling must be
precisely controlled with respect to both the temporal temperature
profile of the baking and chilling cycles and to the uniformity of
the temperature across the substrate.
[0003] The conventional method for baking and chilling wafers
involves first baking the wafer at a temperature ranging typically
between 70.degree. C. and 250.degree. C. for a period of time
ranging typically between 30 seconds and 90 seconds. After baking
the wafer, the wafer is mechanically moved to a cold plate where it
is chilled to a temperature ranging typically between 0.degree. C.
and 30.degree. C.
[0004] There are several disadvantages of the above method. First,
moving a wafer through the air between the hot and cold plates
subjects the wafer to uncontrolled temperature variations during
the bake and chill cycles. Moreover, the time required to move the
wafer between the bake and chill plates prevents the realization of
very short thermal transition times between thermal cycles.
Finally, mechanically moving the wafer from the hot plate to the
cold plate can contaminate or otherwise damage the wafer.
[0005] Attempts have been made to overcome the disadvantages of
separate bake and chill plates. One apparatus places the hot plate
upside down and directly above the cold plate. Because the wafer
moves only a short distance from the cold plate directly upward to
the hot plate, the apparatus reduces the uncontrolled and
nonuniform temperature fluctuations normally present during the
transition from the baking step to the chilling step. Nevertheless,
because the wafer must be moved between separate bake and chill
plates, the wafer is still subjected to uncontrolled and nonuniform
temperature fluctuations during thermal cycling. Moreover, physical
movement inhibits short thermal transition times. Finally, the
wafer may still be exposed to contaminates or otherwise damaged
during the physical movements from the hot plate to the cold
plate.
[0006] Accordingly, the present invention provides an improved
apparatus for the thermal cycling of material substrates such as
wafers used in the manufactures of semiconductors. In particular,
the present invention provides an improved apparatus for thermal
cycling that eliminates the need to move the substrate between
distinct bake or chill plates and that provides improved continuous
control of substrate temperature throughout the entire baking and
chilling cycle. Further features and advantages of the invention
will be apparent from the following description and drawings.
SUMMARY OF THE INVENTION
[0007] The present invention provides a single thermally conductive
plate for baking and chilling a substrate such as a wafer. Because
the substrate is not moved during the entire baking and chilling
cycle, the invention avoids problems associated with the transfer
of the substrate between separate bake and chill plates. Another
feature of the present invention is the use of a thinner plate for
baking and chilling the substrate. A thinner plate provides an
advantage of relatively thicker plates used previously due to the
thinner plates lower thermal mass. Accordingly, the thinner plate
provides for more efficient heat transfer.
[0008] The integrated bake and chill plate of the present invention
contains one or more fluid channels that wind around a center
point, gradually receding from the center point until reaching the
perimeter in a square-like, rectangular-like, triangular-like,
circular or other geometric pattern. The fluid channels permit
thermally conductive fluids of pre-selected temperatures to be
introduced at the perimeter of the integrated bake and chill plate
and drained at the center or introduced at the center of the
integrated bake and chill plate and drained at the perimeter. This
design facilitates different flows and counterflows, which
compensates for different heat transfer at the perimeter of the
integrated bake and chill plate versus the center of the integrated
bake and chill plate. In addition, the integrated bake and chill
plate also can contain microchannels throughout portions of the
fluid channels. The microchannels provide a larger pressure drop
within the fluid channels thereby increasing the velocity of the
thermally conductive fluid. The greater velocity inhibits the
development of areas of nonuniform heat transfer in the integrated
bake and chill plate. Additionally, the microchannels add stiffness
to the integrated bake and chill plate, thereby reducing the
potential for warping of the plate.
[0009] To improve the precision and uniformity of the plate's
temperature, the present invention further comprises one or more
thermoelectric devices (TEDs) in thermal contact with the thermally
conductive plate. Because the TEDs may be quickly and precisely
adjusted to heat the plate, they improve the control of the plate
temperature and provide for shortened plate temperature transition
times. Moreover, independently controlling an array of TEDs allows
for compensation of spatial nonuniformities in substrate
temperature that might arise. Alternatively, such independent
control can provide intentional temperature nonuniformities if
desired for special processing purposes.
[0010] The present invention also comprises a design facilitating
easy replacement of individually damaged TEDs. The TEDs are
attached with a connector, such as a screw or bolt, through a hole
located in the center of the TED. This design also improves the
electrical connection between the TED and a variable power source
and the thermal connection between the thermally conductive plate
and each TED.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The advantages, features and design of the invention will
become apparent from the following detailed description of the
invention and the accompanying drawings in which like reference
numerals refer to like elements and in which:
[0012] FIG. 1 is a perspective view of a preferred embodiment of
the present invention;
[0013] FIG. 2 is a top view of an arrangement of fluid channels in
a preferred embodiment of the invention;
[0014] FIG. 3 is a cross-sectional view of a preferred embodiment
of the invention; and
[0015] FIG. 4 is a top view of an arrangement of fluid channels and
holes in the integrated bake and chill plate in a preferred
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention provides a single thermally conductive
plate for baking and chilling a substrate such as a wafer. Because
the substrate is not moved during the entire baking and chilling
cycle, the invention avoids problems associated with the transfer
of the substrate between separate bake and chill plates. Another
feature of the present invention is the use of a thinner plate for
baking and chilling the substrate. A thinner plate provides an
advantage over relatively thicker plates used previously due to the
thinner plate's lower thermal mass. Accordingly, the thinner plate
provides for more efficient heat transfer.
[0017] Referring to FIG. 1, a substrate 38, such as a semiconductor
wafer or flat panel display, is baked and chilled through thermal
contact with a thermally conductive plate 30. Thermal contact
includes physical proximity or direct physical contact sufficient
to permit the transfer of heat. Both methods of establishing
thermal contact are well known in the art and include positioning
the substrate approximately 0.005-0.006 inches from the plate, or
holding the substrate directly against the plate with a vacuum
line, electrostatic clamp or gravity. It will be appreciated by
anyone skilled in the art that although the present description
uses physical proximity thermal contact for purposes of
definiteness, any of the known methods of thermal contact may be
used. In another preferred embodiment, the thermally conductive
plate 30 has vertical extensions from its bottom surface that
extend to make thermal contact with an integrated bake and chill
plate 34.
[0018] The thermally conductive plate 30 is preferably made of a
1/8or {fraction (3/16)}inch thick piece of aluminum, aluminum
nitride or other suitable ceramic or metal. The thinner plate
provides an advantage over relatively thicker plates used
previously due to the thinner plates lower thermal mass, which
provides for more efficient heat transfer. Positioned on the other
side of plate 30 is an array of thermoelectric devices (TEDs) 32
capable of heating. The TEDs 32 can be controlled to increase or
decrease the amount of heat applied to the thermally conductive
plate. Furthermore, when multiple TEDs 32 are used and individually
controlled, one region of the plate 30 and substrate 38 can be
heated or cooled in a different manner from another region. Thermal
grease can be placed between the plate 30 and TEDs 32 to act as a
conductive interface and improve the thermal contact. In a
preferred embodiment, there are no spaces between the TEDs 32. In
another preferred embodiment there are varying spaces between the
TEDs to allow vertical extensions of the thermally conductive plate
30 to rest between the TEDs and make direct contact with an
integrated bake and chill plate 34.
[0019] Beneath the layer of TEDs 32 is an integrated bake and chill
plate 34 in thermal contact with the TEDs 32 and with the thermally
conductive plate 30. While the integrated bake and chill plate 34
shown in FIG. 1 has a square shape across a horizontal plane, the
plate 34 could also have a circular, oval or other shape. In a
preferred embodiment, the integrated bake and chill plate 34 also
has receiving ribs that are integrally connected to the top surface
of the integrated bake and chill plate to receive the vertical
extensions of the thermally conductive plate 30 thereby improving
thermal conductivity between the integrated bake and chill plate 34
and thermally conductive plate 30 and reducing the potential for
the plate 30 to warp. Preferably, thermal grease is also placed
between the TEDs 32 and integrated bake and chill plate 34 to act
as a conductive interface.
[0020] Beneath the integrated bake and chill plate 34, in a
preferred embodiment, is a layer of insulation 35. Then, beneath
the insulation layer 35 is a printed circuit board (PCB) 36. Any
variable power source can be connected to the TEDs 32, but the
preferred embodiment is to connect the TEDs 32 to a variable power
source through the PCB 36. The TEDs 32 can be individually
controlled by the PCB 36.
[0021] The integrated bake and chill plate of the present invention
contains one or more fluid channels that wind around a center
point, gradually receding from the center point until reaching the
perimeter in a square-like, rectangular-like, triangular-like,
circular or other geometric pattern. The fluid channels permit
thermally conductive fluids of pre-selected temperatures to be
introduced at the perimeter of the integrated bake and chill plate
and drained at the center or introduced at the center of the
integrated bake and chill plate and drained at the perimeter. This
design facilitates different flows and counterflows, which
compensates for different heat transfer at the perimeter of the
integrated bake and chill plate versus the center of the integrated
bake and chill plate. In addition, the integrated bake and chill
plate also can contain microchannels throughout portions of the
fluid channels. The microchannels provide a larger pressure drop
within the fluid channels thereby increasing the velocity of the
thermally conductive fluid. The greater velocity inhibits the
development of areas of nonuniform heat transfer in the integrated
bake and chill plate. Additionally, the microchannels add stiffness
to the integrated bake and chill plate, thereby reducing the
potential for warping of the plate.
[0022] Referring to FIG. 2, the integrated bake and chill plate 34
is illustrated having fluid channels 40A and 40B and fluid inlets
and fluid outlets through which thermally conductive fluid may flow
for heating or cooling the thermally conductive plate. The
temperature of the plate 30 is determined primarily by the
temperature of the fluid flowing through channels 40A and 40B. The
integrated bake and chill plate 34 is approximately 1 inch to
11/2inch thick and is composed of a material of relatively high
thermal conductivity, such as a metal composed of copper or
aluminum. Copper has preferable thermal properties, but aluminum is
less expensive and simpler to manufacture. The integrated bake and
chill plate 34 can be comprised of one solid plate with channels
40A and 40B formed within it or of two plates that are braised
together and have indentations formed on their respective surfaces
so that when joined the two plates create fluid channels 40A and
40B. The temperature of the thermally conductive plate 30 is
determined primarily by the temperature of the fluid following
through the integrated bake and chill plate 34. Any type of
thermally conductive fluid can be used, but the preferred fluids
are water for low temperatures or ethylene glycol, propylene
glycol, or FLUORINERT.TM., which is manufactured by Minnesota
Mining & Manufacturing Corporation, for higher temperatures.
The layer of TEDs 32 provide improved control of the temperature of
thermally conductive plate 30 and the different fluid temperatures
combined with the low thermal mass allow the single plate 30 to be
used for both heating and cooling.
[0023] Again referring to FIG. 2, channels 40A and 40B are
illustrated having fluid-inlets and fluid-outlets near the center
and near the perimeter of the integrated bake and chill plate. The
fluid-inlets and fluid-outlets can be on the bottom surface of the
integrated bake and chill plate or on the side surface. In a
preferred embodiment, the perimeter fluid-inlets and fluid-outlets
are on the side surface to avoid creating locations of concentrated
heat and are on the bottom surface at the center. The parallel
channels 40A and 40B form square pattern spirals as they extend
gradually from the center of the integrated bake and chill plate 34
to the perimeter in a gradually receding manner. Other geometric
spirals are appropriate as well. This design allows for several
different patterns of fluid flow. First, fluid can flow from
generally the perimeter of the integrated bake and chill plate 34
to generally the center in all channels or from generally the
center of the integrated bake and chill plate 34 to generally the
perimeter in all channels. Additionally, the fluid can flow in
opposite directions (counterflow) in the different channels. These
flow options improve the speed with which the integrated bake and
chill plate's 34 temperature can change, thereby allowing for rapid
heating and/or cooling, thereby improving the uniformity of heat
transfer across the integrated bake and chill plate 34.
[0024] Channels 40A and 40B can also contain microchannels 42. The
microchannels extend throughout the fluid channels. Preferably, the
microchannels 42 increase the area of heat transfer across the
integrated bake and chill plate 34, improve the rigidity of the
integrated bake and chill plate 34 to reduce warping, and increase
the velocity of the fluid through the channels for more rapid
heating and cooling and overall better heat transfer. Ideally the
microchannels will have a discontinuous phase at selected points in
the fluid channels. In the preferred embodiment illustrated, the
microchannels are discontinued at the corners to allow more uniform
heat transfer.
[0025] The thermal cycling module is controlled in a preferred
embodiment by feedback control loop, which includes a multivariable
feedback controller. The feedback control loop regulates the
substrate temperature during the thermal cycle by monitoring the
temperature of the substrate and various process parameters with
sensors, e.g. thermocouple sensors or infrared (IR) sensors or a
process sensor such as a scatterometer. Sensors can be positioned
to sense particular temperatures and/or process parameters at
specific regions of the substrate. For example, IR sensors may be
positioned above the substrate to detect infrared radiation from
particular substrate regions. Similarly, thermocouple sensors may
be placed in thermal contact with the substrate to sense substrate
temperatures at particular substrate regions. The thermocouples are
preferably imbedded in the thermally conductive plate. Specific
techniques for measuring substrate temperatures and process
parameters are well known in the art.
[0026] Based on electric signals sent by the sensors, a
microprocessor in the controller calculates control signals for the
TEDs and sends them to the variable power source, which is
electrical contact with the TEDs 32 and controller. The variable
power source changes flow of electric current through the TEDs in
accordance with control signals received from the microprocessor.
The microprocessor calculates and sends additional control signals
to fluid supplies and to valves that control the flow of fluid
through channels 40A and 40B of integrated bake and chill plate 34.
The fluid then flows through the integrated bake and chill plate 34
to roughly determine the temperature of the entire plate 30 over
longer time periods, while the TEDs 32 precisely determine local
variations in the temperature of the plate at specific locations
and determine the plate 30 temperature over short time
intervals.
[0027] Typically, the present device is used through the
specification of predetermined process parameters characteristic of
the desired thermal cycle. For example, the controller may be
programmed to start a substrate at 30.degree. C. and quickly ramp
it up to 80.degree. C. for 60 seconds after which it is chilled to
10.degree. C. for 30 seconds and then returned to 30.degree. C. to
complete the cycle. In this example, the controller sets fluid
supplies to temperatures of 80.degree. C., 30.degree. C. and
10.degree. C., respectively. Initially, the controller sets valves
to permit only the 30.degree. C. fluid to flow through the
integrated bake and chill plate in a chosen flow pattern (either
from the center of the integrated bake and chill plate 34 to the
perimeter, from the perimeter of the integrated bake and chill
plate 34 to the center, or alternating with some fluids flowing
from the center to the perimeter and others flowing from the
perimeter to the center). If any of the sensors indicate a
temperature other than 30.degree. C., then the controller sends a
control signal to the variable power supply in order to
appropriately heat or cool the appropriate plate region. In this
manner, the temperature of the plate 30, and the substrate 38, is
dynamically maintained at a uniform desired temperature.
[0028] At a specified point in time, the controller begins a
transition phase to ramp the temperature from 30.degree. C. to
80.degree. C. At this point, the controller causes valves to permit
only the 80.degree. C. fluid to flow through the integrated bake
and chill plate in a chosen flow pattern. In order to achieve more
rapid temperature response, the controller sends control signals to
the variable power source 36 that will send currents through TEDs
32 to rapidly heat the plate. Once the sensors indicate
temperatures near 80.degree. C., the transition phase is completed
and the controller begins a baking phase where a uniform
temperature of 80.degree. C. is maintained through feedback in the
same manner as the temperature was maintained at 30.degree. C.
[0029] After baking the substrate for 60 seconds, the controller
begins a second transition phase to ramp the temperature from
80.degree. C. to 10.degree. C. At this point, the controller causes
valves to permit only 10.degree. C. fluid to flow through the
integrated bake and chill plate 34 in a desired flow pattern. The
controller also sends control signals to the variable power supply
that will send currents through the TEDs 32 to rapidly cool the
plate. Once the sensors indicate temperatures of 10.degree. C., the
second transition phase is completed and the controller begins a
chill phase where a uniform temperature of 10.degree. C. is
maintained through feedback.
[0030] After the chill phase is completed, the controller begins a
third transition phase to ramp the temperature from 10.degree. C.
to 30.degree. C. in a manner analogous to the transition phases
described above. When the third transition is completed, the
thermal cycle is complete.
[0031] Those skilled in the art can program the controller to
execute many different thermal cycles involving any number of
phases and transitions of different types. Additionally, the
controller can be programmed by those skilled in the art to
implement the described embodiments or any variations.
[0032] To improve the precision and uniformity of the plate's
temperature, the present invention further comprises one or more
thermoelectric devices (TEDs) in thermal contact with the thermally
conductive plate. Because the TEDs may be quickly and precisely
adjusted to heat the plate, they improve the control of the plate
temperature and provide for shortened plate temperature transition
times. Moreover, independently controlling an array of TEDs allows
for compensation of spatial nonuniformities in substrate
temperature that might arise. Alternatively, such independent
control can provide intentional temperature nonuniformities if
desired for special processing purposes.
[0033] The present invention also comprises a design facilitating
easy replacement of individually damaged TEDs. The TEDs are
attached with a connector, such as a screw or bolt, through a hole
located in the center of the TED. This design also improves the
electrical connection between the TED and a variable power source
and the thermal connection between the thermally conductive plate
and each TED.
[0034] Referring to FIG. 3, a cross-sectional view of a preferred
embodiment of the is shown that illustrates how the integrated bake
and chill plate 34 is in thermal and electric contact with the TED
32, PCB 36 and thermally conductive plate 30. The integrated bake
and chill plate 34 and insulation layer 35 is illustrated having
two holes or bores for each TED 32 for establishing an electrical
connection with the PCB 36. The holes extend through the integrated
bake and chill plate 34 and insulation layer 35 and are adapted to
receive a support 51 made of copper or other suitable metal. A
preferred support 51 has a cylindrical structure with a section
having a smaller diameter at the bottom for inserting into and
soldering to the PCB 36 which is powered by a variable power
source. Anything that can be soldered to the support 51 and create
an electrical connection with a variable power source can be used
instead of a PCB 36 as well. A spring loaded pin 53 is inserted in
the support for establishing an electrical connection between the
TED 32 and PCB 36 and support 51. On the bottom surface of the TED
32 are copper pads 56, which when the TED 32 is secured to the
integrated bake and chill plate 34, the pads 56 establish an
electrical connection by depressing the spring loaded pin 53 into
the support 51 soldered to the PCB 36.
[0035] The TEDs 32 comprise a lower plate 52A and upper plate 52B
made of ceramic or other appropriate dielectric device with high
electrical conductivity. The two plates are connected by a copper
support structure 54 or other suitable metal structure and soldered
together as shown in FIG. 5. Attached to the bottom of the lower
plate 52A, are copper pads 56. Although the TED design shown in
FIG. 5 is a preferred design, any type of TED can be used as long
as the integrated bake and chill plate 34 and electrical connection
means for connecting each TED to a variable power source are
adapted accordingly.
[0036] As shown in FIG. 3, the TEDs 32 preferably are secured to
the integrated bake and chill plate 34 with a screw, bolt or other
connector 58 through a hole in the center of each TED 32. There are
corresponding receiving holes on the integrated bake and chill
plate 34 for receiving the connector 58. In a preferred embodiment,
a Belleville washer is used to facilitate support and allow for
vertical movement. Additionally, the TEDs are secured by the
thermally conductive plate 30 which rests above the TEDs 32.
Thermal grease can be placed on the top and bottom of the TEDs to
improve the conductive interface between the thermally conductive
plate and TEDs and between the TEDs and integrated bake and chill
plate.
[0037] In a preferred embodiment, the thermally conductive plate 30
is connected to the PCB 36 with a screw, bolt or other connector
55. The connector 55 travels through a hole in the integrated bake
and chill plate 34 to secure the top plate. Two Belleville washers
56 can be used, one upside down on top of the other, to handle
vibration and thermal shock. Similarly, the PCB 36 can be connected
to the integrated bake and chill plate 34 with a screw, bolt or
other connector 57 as well. Again, in a preferred embodiment, two
Belleville washers 59, one upside down on the other, can be used to
handle thermal shock and vibrations.
[0038] FIG. 4 shows a top view of the integrated bake and chill
plate and all of the locations of the mounting holes and TED
support holes, as well as channels 40A and 40B for movement of
fluids in a preferred embodiment. Hole 62 is a mounting hole
location for the thermally conductive plate 30 and hole 63 is a
mounting hole location for the PCB 36. Holes 64 are locations of
the TED supports 51 and hole 64 is the location for the connector
58 that secures the TEDs 32 to the integrated bake and chill plate
34. Hole 65 accommodates a tooling pin to guide the integrated bake
and chill plate 34 when placing it on the PCB 36. In a preferred
embodiment, the fluid channels 40A and 40B have sufficient space
between them to accommodate the TEDs 32 and the supports 51 and to
facilitate braising of the two integrated bake and chill plate
plates if the integrated bake and chill plate 34 comprises two
plates yet maximize the area of heat transfer between the
integrated bake and chill plate 34 and the TEDs 32. A preferred
number of TEDs 32 to cover the surface of the integrated bake and
chill plate 34 is 196 TEDs 32 arranged in a 14.times.14 matrix or
100 TEDs 32 arranged in a 10.times.10 matrix.
* * * * *