U.S. patent application number 09/891784 was filed with the patent office on 2002-12-26 for apparatus and method for thermally isolating a heat chamber.
Invention is credited to Baumel, Kenneth E., Beer, Emanuel.
Application Number | 20020195201 09/891784 |
Document ID | / |
Family ID | 25398814 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020195201 |
Kind Code |
A1 |
Beer, Emanuel ; et
al. |
December 26, 2002 |
Apparatus and method for thermally isolating a heat chamber
Abstract
An apparatus through which a substrate may be transferred
between a first chamber and a second chamber in which the first
chamber is maintained at a high temperature relative to the ambient
temperature of the second chamber. The apparatus comprises a
passageway for receiving the substrate and a thermally isolating
interface. The thermally isolating interface reduces heat transfer
from the first chamber to the second chamber and allows for
transfer of the substrate between the apparatus and the second
chamber. The thermally isolating interface includes a hole having
dimensions such that the substrate is transferrable through the
thermally isolating interface.
Inventors: |
Beer, Emanuel; (San Jose,
CA) ; Baumel, Kenneth E.; (Los Altos, CA) |
Correspondence
Address: |
APPLIED MATERIALS, INC.
2881 SCOTT BLVD. M/S 2061
SANTA CLARA
CA
95050
US
|
Family ID: |
25398814 |
Appl. No.: |
09/891784 |
Filed: |
June 25, 2001 |
Current U.S.
Class: |
156/345.31 ;
118/719 |
Current CPC
Class: |
C23C 16/54 20130101;
H01L 21/67103 20130101; Y10S 414/139 20130101 |
Class at
Publication: |
156/345.31 ;
118/719 |
International
Class: |
C23F 001/02; C23C
016/00 |
Claims
We claim:
1. An apparatus through which a substrate is transferred between a
first chamber and a second chamber, wherein said first chamber is
maintained at a high temperature relative to a temperature
maintained within said second chamber, said second chamber
including a port; said apparatus comprising: a passageway for
receiving said substrate; and a thermally isolating interface that
reduces heat transfer from said first chamber to said second
chamber, said thermally isolating interface allowing for transfer
of said substrate between said apparatus and said second chamber,
said thermally isolating interface having a face with a border
disposed on said face, the border defining a hole in said thermally
isolating interface having dimensions such that said substrate is
transferrable through said thermally isolating interface.
2. The apparatus of claim 1 wherein said first chamber is a heat
chamber or a high temperature processing chamber and said second
chamber is a transfer chamber.
3. The apparatus of claim 1 wherein said thermally isolating
interface is composed of a material having a thermal conductivity
coefficient less than that of aluminum.
4. The apparatus of claim 3 wherein said thermally isolating
interface is composed of a material having a thermal conductivity
coefficient of less than 1536 Btu inch/(hr)(ft.sup.2)(.degree.
F.).
5. The apparatus of claim 4 wherein said thermally isolating
interface is made of stainless steel.
6. The apparatus of claim 4 wherein said thermally isolating
interface is composed of a stainless steel having a thermal
conductivity coefficient of about 106 Btu
inch/(hr)(ft.sup.2)(.degree. F.).
7. The apparatus of claim 1, wherein said face includes a recess
such that, when said face abuts said port, a thermally isolating
volume is defined within said recess.
8. The apparatus of claim 7 wherein said thermally isolated volume
is occupied by a composition having a thermal conductivity
coefficient of less than 1200 Btu inch/(hr)(ft.sup.2)(.degree.
F.).
9. The apparatus of claim 8 wherein said composition is air or an
insulating material.
10. The apparatus of claim 7 wherein said recess is beveled.
11. The apparatus of claim 7 wherein a cross section of said recess
is defined by a shape selected from the group consisting of a
sawtooth pattern, a repeating pattern, a curve, and a polynomial
equation.
12. The apparatus of claim 1 wherein said high temperature is in a
range between about 250.degree. C. to about 625.degree. C.
13. The apparatus of claim 1 wherein said passageway further
comprises a heating element for maintaining said apparatus at a
temperature that is proximate to said a high temperature.
14. The apparatus of claim 13 wherein said heating element
comprises a heater in a metal shape.
15. The apparatus of claim 13 wherein said heating element is a
coil wrapped about a ceramic base.
16. The apparatus of claim 13 wherein said passageway further
comprises a heat distribution mechanism for distributing heat
generated by said heating element.
17. The apparatus of claim 13 wherein said heat distribution
mechanism is a reflective surface.
18. The apparatus of claim 17 wherein said heat distribution
mechanism is a parabolic mirror.
19. The apparatus of claim 1 wherein said substrate is a
semiconductor substrate or a glass substrate.
20. An apparatus through which a substrate is transferred between a
first chamber and a second chamber, wherein said first chamber is
maintained at a high temperature relative to a temperature
maintained in said second chamber, said second chamber including a
port; said apparatus comprising: a passageway for receiving said
substrate; and a stainless steel interface that reduces heat
transfer from said first chamber to said second chamber, said
stainless steel interface allowing for transfer of said substrate
between said apparatus and said second chamber, said stainless
steel interface having a face with a border disposed on said face,
the border defining a hole in said stainless steel interface having
dimensions such that said substrate is transferrable through said
stainless steel interface.
21. An apparatus through which a substrate is transferred between a
first chamber and a second chamber, wherein said first chamber is
maintained at a high temperature relative to an ambient temperature
of said second chamber, said second chamber including a port; said
apparatus comprising: a passageway for receiving said substrate,
said passageway including a heating element for maintaining said
apparatus at a temperature that is proximate to said high
temperature; and an interface that reduces heat transfer from said
first chamber to said second chamber, said interface allowing for
transfer of said substrate between said apparatus and said second
chamber, said interface having a face with a border disposed on
said face, the border defining a hole in said interface having
dimensions such that said substrate is transferrable through said
interface.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to an apparatus
through which a substrate may be transferred between a heat chamber
and a second chamber, such as a central transfer chamber, to effect
a semiconductor or glass substrate processing regimen. The present
invention has application in a broad array of manufacturing
processes, leading to improved semiconductors or flat panel display
yields. Further, the invention also has application in prolonging
the life of equipment used in such manufacturing processes.
BACKGROUND
[0002] Semiconductor devices are typically made in highly automated
systems. Many of these systems include a central transfer chamber
mounted on a monolithic platform. The central transfer chamber
transfers semiconductor substrates to one or more specialized
chambers or reactors located on the periphery of the transfer
chamber. The specialized chambers or reactors are used to conduct
the various specialized etching, chemical vapor deposition,
diffusion, and annealing processes that are necessary to process
the substrate. Similar such equipment is used in the manufacture of
flat panel displays, as well as various optical components such as
couplers, splitters, filters, array waveguide gratings, Bragg
gratings, taps, attenuators, multiplexers, and de-multiplexers.
Many of these processes are performed at controlled temperatures
and very low pressures.
System Architecture
[0003] FIG. 1A illustrates a representative modular architecture 10
for processing substrates. Architecture 10 comprises a central
transfer chamber 12 to which are connected load lock/cooling
chambers 14A and 14B, each for transferring substrates into system
10, heating chamber 102, and processing chambers 40, 42, 44, and
46. Central transfer chamber 12, loadlock/cooling chambers 14A and
14B, heating chamber 102, and processing chambers 40, 42, 44, and
46 are sealed together for a closed environment in which the system
may be operated at internal pressures considerably less than
standard atmospheric pressure. For example, a representative
pressure is about 10.sup.-3 Torr. Load lock/cooling chambers 14A
and 14B have closable openings comprising load doors 16A and 16B,
respectively, on their outside walls for transfer of substrates
into system 10.
[0004] Load lock/cooling chambers 14A and 14B each contain a
cassette 17 fitted with a plurality of shelves for supporting and
cooling substrates. Cassettes 17 in load lock/cooling chambers 14
are mounted on an elevator assembly (not shown) to raise and lower
the cassettes 17 incrementally by the height of one shelf. To load
chamber 14A, load door 16A is opened and a substrate 72 is placed
on a shelf in cassette 17. The elevator assembly then raises
cassette 17 by the height of one shelf so that an empty shelf is
opposite load door 16A. Another substrate is placed on that shelf
and the process is repeated until all of the shelves of cassette 17
are filled. At that point, load door 16A is closed and chamber 14A
is evacuated to the pressure in system 10.
[0005] A slit valve 20A on the inside wall of load lock/cooling
chamber 14A adjacent to central transfer chamber 12 is then opened.
The substrates are transferred by means of a robot 22 in central
transfer chamber 12 to a heating chamber 102 where they are heated
to the temperature required for processing operations described
below. Robot 22 is controlled by a microprocessor control system
(not shown). Robot 22 is used to withdraw a substrate from cassette
17 of load lock/cooling chamber 14A, insert the substrate onto an
empty shelf in heating chamber cassette 29 and withdraw, leaving
the substrate on a shelf within heating chamber 102. Typically,
heating chamber cassette 29 is mounted on an elevator assembly
within heating chamber 102. After loading one shelf, heating
chamber cassette 29 is raised or lowered to present another empty
shelf for access by robot 22. Robot 22 then retrieves another
substrate from cassette 17 of load lock/cooling chamber 14A.
[0006] In like manner, robot 22 transfers all or a portion of the
substrates from heating chamber cassette 29 to one of four single
substrate processing chambers 40, 42, 44 and 46. Processing
chambers 40, 42, 44 and 46 are adapted to deposit one or more thin
layers onto the substrates. Each of the film chambers 40, 42, 44
and 46 is also fitted on its inner walls 40a, 42a, 44a and 46a,
respectively, with a slit valve 41, 43, 45 and 47, respectively,
for isolation of process gases.
[0007] At the end of film processing, each hot substrate is
transferred to cooling cassette 17 of load lock/cooling chamber
14A, one substrate being placed onto each shelf, with the elevator
mechanism raising and lowering cassette 17 to present an empty
shelf to transfer robot 22 for each substrate.
[0008] Various chambers and reactors used in a typical modular
architecture based system such as a cluster tool are described in
the prior art. For example, U.S. Pat. No. 4,367,672, Wang, et al.
discloses methods of using a plasma to selectively etch holes or
trenches in a film layer on a semiconductor substrate. Similarly,
U.S. Pat. No. 5,614,055, Fairburn, et al., discloses a high density
plasma chemical vapor deposition and etching reactor. U.S. Pat. No.
5,865,896, Nowak et al., discloses a high density plasma chemical
vapor deposition reactor with combined inductive and capacitive
cooling. U.S. Pat. No. 5,108,792, Anderson, et al., discloses a
double-dome reactor for semiconductor processing. U.S. Pat. No.
6,000,227 discloses a representative central transfer chamber that
is cooled.
[0009] Various chambers and vacuum systems are commercially
available. A representative commercial embodiment of a vacuum
system is the AKT processing system which is available from AKT,
Inc., located in Santa Clara, Calif. An exemplary processing
chamber is an AKT 1600 PECVD Chamber, and an exemplary thermal
anneal chamber is a rapid thermal anneal chamber, such as a lamp
heated thermal anneal chamber. These chambers are available from
Applied Materials, Inc.
Unique Problems Associated with Glass Substrate Processing
[0010] The fabrication of devices, such as plates for use in solar
cells and video and computer monitors, makes use of glass
substrates. Often, thin film transistors are etched onto the glass
substrates. The fabrication of such devices is done in a system
that uses many of the same processes and chambers used to fabricate
semiconductor devices. For instance, U.S. Pat. No. 5,512,320,
Turner et al., discloses a representative system for processing
glass substrates. U.S. Pat. Nos. 5,441,768, Law et al., 5,861,107,
Law et al., and 5,928,732 Law et al., disclose methods for
plasma-enhanced chemical vapor deposition on substrates such as
glass. U.S. Pat. No. 5,607,009, Turner et al., discloses a heater
chamber with an elevator assembly for heating glass substrates.
[0011] One product that relies on processing of glass substrates is
flat panel displays. The manufacture of a flat panel display begins
with a clean glass substrate. Transistors are formed on the flat
panel using film deposition and selective etching techniques.
Sequential deposition, photolithography and selective etching of
film layers on the substrate create individual transistors on the
substrate. These transistors, as well as metallic interconnects,
liquid crystal cells and other devices formed on the substrate are
then used to create active matrix display screens for flat panel
displays.
[0012] Although the flat panel display is typically manufactured
using the same processes as those used in semiconductor device
fabrication, the glass used as the flat panel display substrate is
different from a semiconductor substrate in certain aspects that
affect processing and system design. In semiconductor fabrication,
individual devices are formed on the wafer, and the wafer is diced
to form multiple individual integrated circuits. Thus, the creation
of some defective devices on the semiconductor wafer is tolerated,
because the die bearing these defective devices are simply
discarded once the substrate is cut into individual integrated
circuits. In contrast, in a flat panel display, individual
defective devices must not be removed. Therefore, the number of
defective devices created on the flat panel substrate must approach
zero. If a substrate is sufficiently large to allow multiple
displays to be formed on a single substrate, a defect in any one of
the flat panel displays being formed on the flat panel substrate
renders the entire substrate useless. Thus, it is important that
error rates are minimized in flat panel display fabrication
systems.
[0013] An objective common to both semiconductor and glass
substrate processing is the need to avoid, to the extent possible,
exposing the substrate to contamination sources. Accordingly,
conventional processing systems provide a closed environment in
which the various chambers are sealed together. This presents
special problems. For instance, in a typical semiconductor or glass
substrate processing scheme, a heat chamber within the cluster tool
system is used to subject the substrate to a very high temperature.
Yet prior art apparatuses that couple a heat chamber to a central
transfer chamber in a closed environment have not adequately
addressed the heat problems that arise when a heat chamber is
coupled to a central transfer chamber.
[0014] One drawback of prior art cluster tool systems, or other
modular system architectures that have a heat chamber and/or
another high temperature process chamber coupled to a central
transfer chamber, is that thermal energy flows from the heat
chamber or high temperature process chamber to the central transfer
chamber at a significant rate. A reason for this significant flow
of thermal energy is that the apparatus used to couple the heat
chamber or high temperature process chamber to the central transfer
chamber in prior art cluster tool systems, or other modular system
architectures, is made of machined aluminum or aluminum alloys.
Aluminum and aluminum alloys have a high thermal conductivity
coefficient. Central transfer chamber exposure to excessive thermal
energy raises the ambient temperature of the central transfer
chamber. This temperature rise has a deleterious effect on moving
parts within the central transfer chamber, such as the robot arm,
and significantly reduces the lifetime of such parts.
[0015] As discussed above, prior art apparatuses used to couple a
heat chamber or other high temperature process chamber to a central
transfer chamber lose a considerable amount of thermal energy
through the aperture used to ultimately connect the heat chamber or
other high temperature process chamber to the transfer chamber.
This heat loss causes a cold spot to arise within the heat chamber
or other high temperature process chamber. This cold spot is
undesirable because many of the processes carried out in a heat
chamber or other high temperature process chamber require that the
temperature be uniform across the entire substrate. If one section
of the heat chamber or other high temperature process chamber has a
cold spot, it is difficult to maintain substrate temperature
uniformity.
[0016] Accordingly, there is a need in the art for an improved
apparatus for coupling two chambers in a closed environment. In
particular, there is a need in the art for an apparatus that
couples two chambers and minimizes the amount of heat that is
transferred between the two chambers. Such an apparatus would be
particularly useful for connecting a heat chamber or other high
temperature process chamber to a central transfer chamber in the
closed environment of a cluster tool system or other modular
architecture used to process glass substrates.
SUMMARY OF THE INVENTION
[0017] The present invention provides an improved apparatus for
connecting a heat chamber or another high temperature process
chamber to a second chamber, such as a central transfer chamber, in
a closed environment suitable for modular architecture based
substrate processing in such a manner that heat transfer from the
heat chamber or another high temperature process chamber to the
second chamber is minimized. The apparatus of the present invention
includes a thermally isolating interface, which has a reduced
thermal conductivity coefficient, that abuts the second chamber.
This thermally isolating interface reduces the amount of heat that
is transferred from the heat chamber or other high temperature
process chamber to the second chamber. Furthermore, in some
embodiments of the present invention, the thermally isolating
interface includes one or more recesses so that the surface area
between the thermally isolating interface and the second chamber is
minimized. Reduction in this surface area, in turn, minimizes
thermal transfer between the heat chamber or other high temperature
process chamber and the second chamber. Thus, the apparatus of the
present invention prolongs the life of moving parts in the second
chamber, such as the robot arm.
[0018] In some embodiments of the present invention, the apparatus
includes a heating device to prevent heat loss from the second
chamber. In many substrate processing regimens, maintenance of a
uniform temperature within the second chamber is an important
requirement. The inclusion of a heating device in the apparatus of
the present invention prevents heat loss through the aperture to
the second chamber. Furthermore, the inclusion of a heating device
in the apparatus of the present invention lowers the potential
temperature differential across large substrates that pass through
the apparatus. The reduction in temperature differential across the
substrate potentially reduces stress on the substrate, particularly
in processing regiments that require the substrate to pass into the
second chamber several times.
[0019] One embodiment of the present invention provides an
apparatus through which a substrate may be transferred between a
first chamber, such as a heat chamber or other high temperature
process chamber, and a second chamber, such as a central transfer
chamber. The first chamber is maintained at a high temperature
relative to the temperature maintained within the second chamber.
The apparatus comprises: (i) a passageway for receiving the
substrate and (ii) a thermally isolating interface that reduces
heat transfer from the first chamber to the second chamber. The
thermally isolating interface has a hole in the face of the
interface that abuts a port into the second chamber. The hole has
dimensions such that the substrate is transferrable through the
interface, thereby allowing for substrate transfer between the
first chamber and the second chamber.
[0020] In some embodiments of the present invention, the thermally
isolating interface is composed of a material having a thermal
conductivity coefficient less than that of aluminum, which is about
1536 Btu inch/(hr)(ft.sup.2)(.degree. F.). In yet other
embodiments, the thermally isolating interface is composed of a
material having a thermal conductivity coefficient of less than
1200 Btu inch/(hr)(ft.sup.2)(.degre- e. F.). In still other
embodiments of the present invention, the thermally isolating
interface is composed of an austenitic, martensitic steel, or
ferritic steel. In one aspect of the present invention, the
thermally isolating interface is composed of stainless steel. In
one embodiment in accordance with this aspect of the invention, the
thermally isolating interface is composed of a stainless steel
having a thermal conductivity coefficient of about 106 Btu
inch/(hr)(ft.sup.2)(.degree. F.).
[0021] In some embodiments of the present invention, the face of
the thermally isolating interface includes one or more recesses
such that an enclosed volume is defined within the recess when the
face abuts the port of the second chamber. In some embodiments,
this enclosed volume remains empty or is occupied by an insulating
material. In general, whatever occupies the enclosed volume has a
thermal conductivity coefficient of less than that of aluminum. For
example, in one embodiment, the enclosed volume is simply air,
which has a thermal conductivity of 0.18 Btu
inch/(hr)(ft.sup.2)(.degree. F.). Because whatever occupies the
enclosed volume has a thermal conductivity less than that of
aluminum, the enclosed volume is referred to herein as a thermally
isolating volume.
[0022] The present invention contemplates a large number of
different shaped recesses all of which are in accordance with the
present invention. For example, in one embodiment, the recess is
beveled. In other embodiments, the shape of the recess is best
described in terms of the shape of a cross section of the recess.
The shape of the cross section of some recesses in accordance with
these embodiments is alternatively defined by a sawtooth pattern, a
repeating pattern, a curve or a polynomial equation.
[0023] In selected embodiments of the present invention, the
passageway through which the substrate is passed includes a heating
element for maintaining the passageway at a temperature that is
proximate to the temperature of the heat chamber and/or another
high temperature process chamber such as a chemical vapor
deposition (CVD) chamber. In some embodiments, this heating element
is a coil wrapped around a ceramic base. Further, in some
embodiments the heat from the heating element is distributed by a
distribution mechanism such as a reflective surface. In a preferred
embodiment, this reflective surface is a parabolic mirror.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] So that the manner in which the above recited features,
advantages and objects of the present invention are attained and
can be understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to the
embodiments thereof which are illustrated in the appended
drawings.
[0025] It is to be noted however, that the appended drawings
illustrate only typical embodiments of this invention and are
therefore not to be considered limiting to its scope, for the
invention may admit to other equally effective embodiments.
[0026] FIG. 1A is a plan view of a prior art vacuum system.
[0027] FIG. 1B is a plan view of a prior art heat chamber that
includes a prior art apparatus for coupling the heat chamber to a
second chamber.
[0028] FIG. 2 is a top view of a schematic of a system
incorporating the present invention.
[0029] FIG. 3 is a side view of a schematic of a thermally
isolating interface in accordance with one embodiment of the
present invention.
[0030] FIG. 4 is a schematic view of a thermally isolating
interface in accordance with one embodiment of the present
invention.
[0031] FIG. 5 is a diagrammatic cross-sectional view of a thermally
isolating interface in accordance with one embodiment of the
present invention.
[0032] FIG. 6 is a diagrammatic cross-sectional view of a thermally
isolating interface that features a first embodiment of a shaped
recess.
[0033] FIG. 7 is a diagrammatic cross-sectional view of a thermally
isolating interface that features a second embodiment of a shaped
recess.
[0034] FIG. 8 is a diagrammatic cross-sectional view of the
passageway of an apparatus of the present invention that includes a
heating element and a heat distribution mechanism.
[0035] FIG. 9 is a diagrammatic cross-sectional view of FIG. 8.
[0036] Like reference numerals refer to corresponding parts
throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] The present invention provides an improved apparatus for
connecting two chambers in a closed environment. The improved
apparatus minimizes heat transfer from the two chambers by
including an improved interface. In some embodiments of the present
invention, the improved interface is made of a material that has a
reduced thermal conductivity coefficient. In other embodiments of
the present invention, the interface includes one or more recesses
so that the surface area between the interface and the second
chamber is minimized. This surface area minimization reduces the
amount of thermal energy that is transferred to the second chamber.
In still other embodiments of the present invention, the apparatus
includes a heating device to prevent heat loss near the aperture to
the second chamber.
[0038] FIG. 1B discloses a conventional heat chamber 102 with a
prior art apparatus 54 including a hole 56 through which substrates
are passed between the conventional heat chamber 102 and a second
chamber such as a central transfer chamber. A closed environment
between heat chamber 102 and a second chamber is maintained by
bolting and sealing the interface 58 of apparatus 54 to a similar
interface on the second chamber.
[0039] Referring to FIG. 2, a plan view is disclosed of a schematic
of a modular architecture incorporating an apparatus 104 of the
present invention. FIG. 2 includes a schematic representation of
heat chamber 102, chamber 110, and apparatus 104. While FIG. 2
discloses a heat chamber 102, the apparatus and methods of the
present invention may, in fact, be used with any of a number of
high temperature process chambers rather than a heat chamber. For
example, chamber 102 could be a chemical vapor deposition (CVD)
chamber. In one embodiment, heat chamber 102 is any form of chamber
used to heat a substrate to a specified temperature. For instance,
in some embodiments, heat chamber 102 is a batch-type heat chamber
designed for glass substrates, such as that disclosed in U.S. Pat.
No. 5,607,009, Turner et al. It will be appreciated that, because
glass substrates are typically rectangular shaped, the plan
dimensions of the heat chamber in such embodiments is rectangular
rather than the circular shape shown. In other embodiments, heat
chamber 102 is a heat chamber designed for silicon substrates.
[0040] In some configurations of the present invention, chamber 110
is a central transfer chamber used in semiconductor and/or glass
substrate processing. A representative transfer chamber is
disclosed in U.S. Pat. No. 5,512,320, Turner et al. Chamber 110
includes a port 112 with an interface 114. Central transfer chamber
10 is found in such products as the Precision 5000, Endura,
Centura, Producer, and Endura SL, which are manufactured and sold
by Applied Materials, Inc., located in Santa Clara, Calif.
[0041] Apparatus 104 is used to couple heat chamber 102 to chamber
110. Apparatus 104 is composed of a passageway 120 and a thermally
isolating interface 108. Interface 114 and thermally isolating
interface 108 are bolted and sealed together in such a manner that
a closed environment is formed between heat chamber 102 and chamber
110. This closed environment enables heat chamber 102 and chamber
110 to maintain a vacuum.
[0042] An important advantage of the present invention is that heat
transfer between apparatus 104 and chamber 110 is reduced by
forming a thermally isolating interface 108 from a material having
thermal conductivity that is less than that of aluminum or aluminum
alloy. The advantage of such construction will be appreciated by
reference to FIG. 3 in which a schematic view of thermally
isolating interface 108 is depicted. Thermally isolating interface
108 is coupled to passageway 120 and to interface 114 of port 112.
Because passageway 120 is communicatively coupled to heat chamber
102, it is at a high temperature t.sub.1 during normal operation.
And because interface 114 is communicatively coupled to port 112
and chamber 110, it is at some lower temperature t.sub.2. Because
t.sub.1 is higher than t.sub.2, the direction of heat flow, q, is
from passageway 120 to interface 114 and ultimately to chamber 110
through port 112 (FIG. 2).
[0043] An important aspect of the present invention is that
thermally isolating interface 108 is composed of a material having
a thermal conductivity coefficient of less than that of aluminum so
that heat transfer between heat chamber 102 and chamber 110 (FIG.
2) is reduced. Accordingly, materials that can be used to make
thermally isolating interface 108 include any machinable material
that has a thermal conductivity coefficient less than that of
aluminum. In some embodiments, the material used to make thermally
isolating interface 108 can withstand temperatures up to about
625.degree. C. or more without melting. In other embodiments, the
material used to make thermally isolating interface 108 can
withstand temperatures, such as about 100.degree. C. to about
550.degree. C., without melting.
[0044] While reference is made to the material used to make
thermally isolating interface 108, it will be appreciated that
passageway 120 could also be made from material having a thermal
conductivity coefficient of less than that of aluminum. Further, in
some embodiments, passageway 120 and thermally isolating interface
108 may be a single part.
[0045] Reference to a wide range of materials that are suitable for
use in the present invention may be found in Marks' Standard
Handbook for Mechanical Engineers, id, including the Table at 6-11.
Thus, possible materials for thermally isolating interface 108
include, platinum, as well as various alloys of iron and chromium
including steel with an American Iron and Steel Institute
designation of C1020 (hot-worked) or 304 (sheet). However, in a
preferred embodiment, the material used for thermally isolating
interface 108 is any common form of stainless steel.
[0046] Reference will now be made to FIG. 4 in order to illustrate
additional features of certain embodiments of the present
invention. FIG. 4 represents a schematic view of thermally
isolating interface 108 along line 4-4' shown in FIG. 2, in
accordance with one embodiment of the present invention. Thus, FIG.
4 represents a face 402 of thermally isolating interface 108 that
is bolted onto interface 114 of port 112 (FIG. 2). Face 402 defines
a hole 404 in the thermally isolating interface 108 having
dimensions such that a substrate is transferrable through thermally
isolating interface 108. Bolt holes 406 in face 402 serve as holes
for bolts (not shown) used to bolt and seal thermally isolating
interface 108 to interface 114 of port 112.
[0047] An important feature of face 402 is the presence of one or
more recesses 408. In a typical embodiment, a recess 408 is made by
milling a portion of face 402 to form a cavity. A recess 408 has
the effect of reducing the amount of surface area on face 402 that
comes into contact with interface 114 when face 402 is bolted and
sealed onto interface 114 of port 112 (FIG. 2), thus reducing the
amount of heat flow Q [Eq. (1)] from heat chamber 102 to chamber
110. While three recesses (408-1, 408-2, and 408-3) are shown in
the embodiment illustrated in FIG. 4, it will be appreciated that
any number of recesses may be milled into face 402 provided that a
closed environment may still be formed when thermally isolating
interface 108 is bolted to interface 114 of port 112 (FIG. 2). When
thermally isolating interface 108 is bolted to interface 114, an
enclosed volume is defined by the walls of the recess and the
abutting portion of interface 114. In some embodiments, this
enclosed volume remains empty or is occupied by an insulating
material. In general, whatever occupies the enclosed volume,
whether it is an insulating material or air, has a thermal
conductivity coefficient of less than that of aluminum, which is
about 1536 Btu inch/(hr)(ft.sup.2)(.degree. F.). Therefore, the
enclosed volume is referred to herein as a thermally isolating
volume.
[0048] FIG. 5 shows a cross-sectional view of recesses 408-2 and
408-3 within thermally isolating interface 108 along vertical line
5-5' drawn in FIG. 4. As seen in FIG. 5, each recess 408 reduces
the surface area of face 402 that comes into contact with interface
114 (FIG. 2), thereby reducing the amount of heat flow Q [Eq. (1)]
from heat chamber 102 to chamber 110.
[0049] Turning attention to FIG. 6, which is a cross-sectional view
of recess 408-3 along horizontal line 6-6' of FIG. 4, additional
features found in some embodiments of the present invention are
shown. FIG. 6 highlights the shape of recess 408-3. In some
embodiments, which are not illustrated, recess 408-3 is beveled. In
still other embodiments, a cross-section of recess 408-3 has a
shape that can be described as a sawtooth pattern. Such a pattern
is illustrated in FIG. 7. However, it will be appreciated that
recess 408 may have a wide number of different shapes including,
but not limited to, any form of repeating pattern, a curve, or a
shape determined by a polynomial equation.
[0050] FIG. 8 illustrates another feature found in some embodiments
of the present invention. FIG. 8 is a diagrammatic cross-sectional
view of passageway 120 along line 8-8' of FIG. 2. For perspective,
FIG. 8 includes a representation of the position of hole 404
(dashed lines) that is present in thermally isolating interface
108.
[0051] Representative central transfer chambers, such as chamber
110, include a slit valve (not shown) that opens in port 112 when a
substrate is exchanged between chamber 110 and 102 (FIG. 2). When
this slit value is open, a large amount of heat loss occurs through
hole 404 in apparatus 104. This results in a cold spot within
passageway 120 of apparatus 104. To alleviate this cold spot, some
embodiments of the present invention include a heating element.
This heating element maintains apparatus 104 at a temperature that
is proximate to the temperature of heating chamber 102. For
example, if heating chamber 102 is maintained at a temperature from
250.degree. C. to 625.degree. C., the heating element may maintain
apparatus 104 at a temperature between about 40.degree. C. to about
550.degree. C., depending on the processes supported by a specific
modular architecture. In some embodiments, the heating element may
maintain apparatus 104 at a temperature from about 50.degree. C. to
about 500.degree. C. In still other embodiments, heating element
may maintain apparatus 104 at a temperature from about 70.degree.
C. to about 300.degree. C. In some embodiments of the present
invention, chamber 102 operates at a temperature as high as
550.degree. C. and the heating element is operated at a temperature
that reduces heat loss from chamber 102. In any event, it will be
appreciated that the heating element can maintain apparatus 104 at
temperatures in ranges not explicitly mentioned herein and that any
such temperature range is within the scope of the present invention
so long as the temperature range facilitates a semiconductor or
glass processing regimen.
[0052] The heating element 802 shown in FIG. 8 is a representative
heating element in accordance with the present invention. In
general, heating element 802 is any heating element capable of
heating apparatus 104 to a suitable temperature without giving off
particulate matter that will damage a substrate that is being
processed. For example, heating element may be a tungsten coil
wrapped around a ceramic base. In some embodiments, heating element
802 is cast in metal. Illustrative of such embodiments is the
Watlow cast-in or interference fit (IFC) product line.
[0053] In some embodiments of the present invention, a heat
distribution mechanism is used to distribute heat generated by
heating element 802. Typically, the heat distribution mechanism is
a reflective surface. In one embodiment, the reflective surface is
a parabolic mirror. FIG. 8 illustrates a parabolic mirror 804 that
is used to reflect heat generated from heating element 802.
[0054] FIG. 9 is a diagrammatic cross-sectional view along line
9-9' of FIG. 8 showing two heating elements 802. In practice, an
apparatus 104 in accordance with the present invention may have any
number of heating elements 802 and the presence of two heating
elements 802 in FIG. 9 merely illustrates this point. FIG. 9
further shows how, in cross-sectional view, parabolic mirror 804
distributes heat from heating element 802. Thus, an apparatus 104
of the present invention is advantageous because it prevents the
apparatus from being a heat sink to the heat chamber or other high
temperature process chamber. As a result, apparatus 104 promotes
temperature uniformity within the heat chamber or other high
temperature process chamber.
[0055] While reference was made to glass substrates and silicon
substrates, it will be appreciated that the teachings of the
present invention are not limited to glass substrates or silicon
substrates. Indeed, the apparatuses and methods of the present
invention may be used for substrates that include, but are not
limited to, glass panels, quartz, silica, fused silica, silicon,
and doped silicon, gallium arsenide, as well as any other type of
substrate that may be processed by modular architecture based
systems. In fact, the methods of the present invention may be used
for substrates composed of any of the III-IV semiconductors.
Furthermore, the substrates processed in accordance with the
apparatuses and methods of the present invention may be round,
rectangular, or any other suitable shape. In particular, in some
embodiments, the substrates processed by the present invention are
noncircular substrates having an area greater than 400 cm.sup.2.
Exemplary substrates include, but are not limited to, rectangular
or square substrates used in flat panel display fabrication having
dimensions of, for example, about 370 mm.times.470 mm or larger.
Substrates having rectangular dimensions as large as 1
meter.times.1.5 meter are contemplated as well.
[0056] All references cited herein are incorporated herein by
reference in their entirety and for all purposes to the same extent
as if each individual publication or patent was specifically and
individually indicated to be incorporated by reference in its
entirety for all purposes.
[0057] The foregoing descriptions of specific embodiments of the
present invention are presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Obviously many
modifications and variations are possible in view of the above
teachings. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
applications, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
following claims and their equivalents.
* * * * *