U.S. patent application number 10/455004 was filed with the patent office on 2004-12-09 for heat pipe with temperature control.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Hazelton, Andrew J..
Application Number | 20040244963 10/455004 |
Document ID | / |
Family ID | 33489837 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040244963 |
Kind Code |
A1 |
Hazelton, Andrew J. |
December 9, 2004 |
Heat pipe with temperature control
Abstract
Methods and apparatus for controlling the boiling temperature of
a fluid within a heat pipe are disclosed. According to one aspect
of the present invention, a method for controlling a temperature
associated with a heat pipe that contains a fluid and has an
evaporator end includes measuring the temperature associated with
the heat pipe and determining when the temperature associated with
the heat pipe is at a desired level. The method also includes
changing a pressure within the heat pipe when it is determined that
the temperature associated with the heat pipe is not at a desired
level. Changing the pressure within the heat pipe causes the
temperature associated with the heat pipe to change.
Inventors: |
Hazelton, Andrew J.; (San
Carlos, CA) |
Correspondence
Address: |
RITTER, LANG & KAPLAN
12930 SARATOGA AE. SUITE D1
SARATOGA
CA
95070
US
|
Assignee: |
Nikon Corporation
Tokyo
JP
|
Family ID: |
33489837 |
Appl. No.: |
10/455004 |
Filed: |
June 5, 2003 |
Current U.S.
Class: |
165/272 |
Current CPC
Class: |
G03F 7/70758 20130101;
F28D 15/06 20130101; G03F 7/70858 20130101 |
Class at
Publication: |
165/272 |
International
Class: |
F28F 027/00 |
Claims
1. A method for controlling a temperature associated with a heat
pipe, the heat pipe being arranged to contain a fluid, the heat
pipe having an evaporator end, the evaporator end being arranged to
be in the vicinity of a heat source, the method comprising:
measuring the temperature associated with the heat pipe;
determining when the temperature associated with the heat pipe is
at a desired level; and changing a pressure within the heat pipe
when it is determined that the temperature associated with the heat
pipe is not at a desired level, wherein changing the pressure
within the heat pipe changes a boiling temperature of the fluid and
causes the temperature associated with the heat pipe to change.
2. The method of claim 1 wherein changing the pressure within the
heat pipe includes increasing the pressure within the heat pipe to
cause the temperature associated with the heat pipe to be
raised.
3. The method of claim 1 wherein the heat pipe includes a pressure
control mechanism, and changing the pressure within the heat pipe
includes operating the pressure control mechanism.
4. The method of claim 3 wherein the pressure control mechanism
includes a piston assembly, and changing the pressure within the
heat pipe includes applying a controlled pressure using the piston
assembly.
5. The method of claim 4 wherein the piston assembly is actuated by
an electromagnetic actuator, and changing the pressure within the
heat pipe includes applying a controlled force to the piston
assembly using the electromagnetic actuator.
6. The method of claim 4 wherein the piston assembly is actuated by
an air bellows, and changing the pressure within the heat pipe
includes applying a controlled force to the piston assembly using
the air bellows.
7. The method of claim 1 wherein measuring the temperature
associated with the heat pipe includes measuring the temperature at
the evaporator end.
8. The method of claim 7 wherein the temperature measured at the
evaporator end is a boiling temperature of the fluid.
9. A method for operating an exposure apparatus comprising the
method for controlling the temperature of claim 1.
10. A method for making an object including at least a
photolithography process, wherein the photolithography process
utilizes the method of operating an exposure apparatus of claim
9.
11. A method for making a wafer utilizing the method of operating
an exposure apparatus of claim 9.
12. A heat pipe comprising: an evaporator end; a fluid; and a
pressure control mechanism, wherein the pressure control mechanism
is arranged to change a pressure within the heat pipe such that a
boiling temperature of the fluid is changed.
13. The heat pipe of claim 12 wherein the pressure control
mechanism is arranged to change the pressure by increasing the
pressure such that the boiling temperature of the fluid is
increased.
14. The heat pipe of claim 12 wherein the pressure control
mechanism includes a piston arrangement, the piston arrangement
being arranged to apply a control pressure to change the pressure
within the heat pipe.
15. The heat pipe of claim 14 wherein the pressure control
mechanism further includes an actuator, the actuator being arranged
to apply a control force to the piston arrangement such that the
piston arrangement applies the control pressure to change the
pressure within the heat pipe.
16. The heat pipe of claim 14 wherein the pressure control
mechanism further includes an air bellows, the air bellows being
arranged to cause the piston arrangement to apply the control
pressure to change the pressure within the heat pipe.
17. The heat pipe of claim 14 further including: a temperature
sensor, the temperature sensor being arranged to measure the
boiling temperature of the fluid.
18. The heat pipe of claim 17 wherein the measured boiling
temperature is provided to the pressure control mechanism, the
pressure control mechanism being arranged to change the pressure by
an amount determined using the measured boiling temperature.
19. The heat pipe of claim 17 wherein the temperature sensor is
arranged at the evaporator end.
20. The heat pipe of claim 12 further including: a condenser end,
wherein the pressure control mechanism is positioned near the
condenser end of the heat pipe.
21. The heat pipe of claim 12 wherein the evaporator end is
arranged to be positioned near an external heat source.
22. The heat pipe of claim 21 wherein the external heat source is a
coil of a linear motor within a stage apparatus.
23. An exposure apparatus comprising the stage apparatus of claim
22.
24. A device manufactured with the exposure apparatus of claim
23.
25. A wafer on which an image has been formed by the exposure
apparatus of claim 23.
26. A method for controlling a temperature of an actuator within a
stage apparatus, the stage apparatus being in communication with an
evaporator end of a heat pipe, the method comprising: determining a
desired temperature for the actuator; and adjusting a mechanism
within the heat pipe to achieve the desired temperature for the
actuator, wherein adjusting the mechanism causes a boiling
temperature of a fluid within the heat pipe to be adjusted such
that a temperature of the heat pipe is adjusted.
27. The method of claim 26 wherein adjusting the pressure within
the heat pipe includes applying a control force of a first amount
to a piston arrangement of the heat pipe, wherein the control force
of the first amount is arranged to cause the piston arrangement to
change the pressure within the heat pipe.
28. The method of claim 27 further including: determining when the
temperature of the actuator is the desired temperature for the
actuator, wherein when it is determined that the temperature of the
actuator is the desired temperature for the actuator, the control
force is maintained at the first amount.
29. The method of claim 28 wherein when it is determined that the
temperature of the actuator is not the desired temperature for the
actuator, adjusting the pressure within the heat pipe to achieve
the desired temperature for the actuator further includes applying
a control force of a second amount to the piston arrangement,
wherein the control force of the second amount is arranged to cause
the piston arrangement to change the pressure within the heat pipe,
the second amount being different from the first amount.
30. The method of claim 26 further including: determining a
corresponding desired temperature for a section of the heat pipe
using the desired temperature for the actuator, wherein adjusting
the mechanism to achieve the desired temperature for the heat pipe
includes adjusting the mechanism to achieve the corresponding
desired temperature for the section of the heat pipe.
31. The method of claim 30 wherein the section is the evaporator
end.
32. A method for operating an exposure apparatus comprising the
method for controlling the temperature of claim 26.
33. A method for making an object including at least a
photolithography process, wherein the photolithography process
utilizes the method of operating an exposure apparatus of claim
32.
34. A method for making a wafer utilizing the method of operating
an exposure apparatus of claim 32.
35. A method for controlling a temperature of an actuator within a
stage apparatus, the stage apparatus being in communication with an
evaporator end of a heat pipe, the heat pipe including a piston
arrangement, the method comprising: determining a desired
temperature for the actuator; and adjusting the piston arrangement
to achieve the desired temperature for the actuator, wherein
adjusting the piston arrangement causes a boiling temperature of a
fluid within the heat pipe to be changed such that a temperature of
the actuator is changed.
36. The method of claim 35 wherein adjusting the piston arrangement
includes adjusting an internal pressure of the heat pipe to change
the temperature of the actuator.
37. The method of claim 35 wherein adjusting the piston arrangement
includes adjusting an internal volume of the heat pipe to change
the temperature of the actuator.
38. The method of claim 35 wherein adjusting the piston arrangement
includes applying a control force to the piston arrangement.
39. The method of claim 38 wherein applying the control force to
the piston arrangement causes a control pressure to be applied
using the piston arrangement, the control pressure being arranged
to cause the boiling temperature of the fluid to be changed.
40. The method of claim 35 further including: determining a
corresponding desired temperature for a section of the heat pipe
using the desired temperature for the actuator.
41. The method of claim 40 wherein the section is the evaporator
end.
42. A method for operating an exposure apparatus comprising the
method for controlling the temperature of claim 35.
43. A method for making an object including at least a
photolithography process, wherein the photolithography process
utilizes the method of operating an exposure apparatus of claim
42.
44. A method for making a wafer utilizing the method of operating
an exposure apparatus of claim 42.
45. A cooling device comprising: a heat pipe having an end portion
that is arranged to be in vicinity of a heat source; a fluid that
is contained in the heat pipe; and a pressure control mechanism
connected to the heat pipe, the pressure control mechanism being
arranged to change a pressure within the heat pipe such that a
boiling temperature of the fluid is changed.
46. The cooling device of claim 45, wherein the heat pipe has an
evaporator end and a condenser end, and the evaporator end is
located on the end portion.
47. A heat transfer apparatus comprising: a flow passage; at least
one heat receiving section where heat is transferred from a heat
source, the at least one heat receiving section being disposed on
the way of the flow passage; a heat transfer medium filled within
said flow passage, the heat transfer medium being circulated within
the flow passage; and a temperature setting device connected to the
flow passage, the temperature setting device being arranged to
change a state-shift temperature of the heat transfer medium.
48. The heat transfer apparatus of claim 47, wherein the
temperature setting device changes a boiling temperature of the
heat transfer medium.
49. The heat transfer apparatus of claim 47, wherein the
temperature setting device changes a pressure within the flow
passage.
50. The heat transfer apparatus of claim 47, wherein the heat
source is a part of an actuator within a stage apparatus.
51. An exposure apparatus comprising the stage apparatus of claim
50.
52. A method for controlling a temperature associated with a heat
transfer apparatus, the method comprising: circulating a heat
transfer medium within a flow passage, the flow passage including
at least one heat receiving section where heat is transferred from
a heat source; and changing a state-shift temperature of the heat
transfer medium circulating within the flow passage.
53. The method of claim 52, wherein changing a state-shift
temperature includes changing a boiling temperature of the heat
transfer medium.
54. The method of claim 52, wherein changing a state-shift
temperature includes changing a pressure within the flow
passage.
55. A method for operating a stage device comprising the method for
controlling the temperature of claim 52.
56. A method for operating an exposure apparatus comprising the
method for controlling the temperature of claim 52.
57. A method for making an object including at least a
photolithography process, wherein the photolithography process
utilizes the method of operating an exposure apparatus of claim
56.
58. A method for making a wafer utilizing the method for operating
an exposure apparatus of claim 56.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates generally to semiconductor
processing equipment. More particularly, the present invention
relates to a heat pipe with an internal temperature that may be
readily controlled by changing the pressure within the heat
pipe.
[0003] 2. Description of the Related Art
[0004] For precision instruments such as photolithography machines
which are used in semiconductor processing, factors which affect
the performance, e.g., accuracy, of the precision instrument
generally must be dealt with and, insofar as possible, eliminated.
When the performance of a precision instrument is adversely
affected, as for example by disturbance forces or by excessive
heat, products formed using the precision instrument may be
improperly formed and, hence, defective. For instance, a
photolithography machine which is subjected to disturbance forces
may cause an image projected by the photolithography machine to
move, and, as a result, be aligned incorrectly on a projection
surface such as a semiconductor wafer surface.
[0005] Scanning stages such as wafer scanning stages and reticle
scanning stages are often used in semiconductor fabrication
processes, and may be included in various photolithography and
exposure apparatuses. Wafer scanning stages are generally used to
position a semiconductor wafer such that portions of the wafer may
be exposed as appropriate for masking or etching. Reticle scanning
stages are generally used to accurately position a reticle or
reticles for exposure over the semiconductor wafer. Patterns are
generally resident on a reticle, which effectively serves as a mask
or a negative for a wafer. When a reticle is positioned over a
wafer as desired, a beam of light or a relatively broad beam of
electrons may be collimated through a reduction lens, and provided
to the reticle on which a thin metal pattern is placed. Portions of
a light beam, for example, may be absorbed by the reticle while
other portions pass through the reticle and are focused onto the
wafer.
[0006] A stage such as a wafer scanning stage or a reticle scanning
stage is typically supported by a base structure such that the
stage may move in a linear direction. The base structure often
includes or houses various sensors and actuators which serve to
control the motion of the stage and a table, e.g., a wafer table,
which is a part of an overall stage apparatus. Such actuators are
often arranged to control a coarse stage of an overall wafer stage,
and include coils which generate heat. The heat generated by the
coils may be relatively significant, e.g., significant enough to
affect an exposure process performed using the overall wafer stage.
The heat generated may be, for example, in the range of
approximately 10 degrees Celsius to approximately 20 degrees
Celsius higher than a desired ambient temperature. Since the heat
generated by the coils may adversely affect the performance of the
overall wafer stage by, for example, interfering with the operation
of sensors such as interferometers, the generated heat is generally
carried away or otherwise removed from the vicinity of relatively
critical components of the overall wafer stage. Carrying heat away
from relatively critical components, as for example a wafer,
reduces the effect of excessive heat on the critical
components.
[0007] One device that may be used to carry heat away from
relatively critical components is a heat pipe. For example, a heat
source such as a linear motor within a stage device may be
substantially in contact with a heat pipe which is arranged to
remove heat from the heat source and to transfer the heat to a heat
sink. FIG. 1 is a diagrammatic representation of a conventional
heat pipe. A heat pipe 100 includes an evaporator end 102 and a
condenser end 104. Heat pipe 100 may generally be configured as a
hollow cylindrical tube that is substantially lined with wicking
material 112, e.g., a cotton sleeve. When heat is generated by a
heat source 106, a fluid in liquid form that is contained within
heat pipe 100 may be heated to its boiling point by heat source 106
at evaporator end 102. The fluid is typically a fluid which takes
on a gaseous or vapor state when heated, and a liquid state when
cooled. When heated at evaporator end 102, the fluid may be
conducted towards a heat sink 107 positioned near condenser end
104, as indicated by arrows 108. It should be understood that heat
sink 107 may be the environment around heat pipe 100, and may not
necessarily be a physical component.
[0008] Heat sink 107 is arranged to remove the heat from the fluid
and, as a result, allows the fluid to be cooled. That is, fluid at
condenser end 104 condenses and transfers its latent heat of
vaporization to heat sink 107. Cooled fluid may be returned through
heat pipe 100 to heat source 102 when the condensed fluid enters
wicking material 112 which is located within heat pipe 100.
Capillary action then forces the condensed fluid through wicking
material 112 back to evaporator end 102, as indicated by arrows
110.
[0009] In some cases, the ability to control the boiling
temperature of fluid within a heat pipe may be needed such that the
temperature of a heat source such as heat source 106 of FIG. 1 may
be controlled. Controlling the temperature of a heat source may be
critical, as many systems may require that the temperature of a
heat source, e.g., the surface temperature of a coil of a linear
motor, be maintained as close to an ambient temperature such as
room temperature as possible. To control the temperature of a heat
source, the boiling temperature associated with a fluid contained
within a heat pipe may be controlled. For example, a heat pipe may
be "charged" to alter the boiling temperature of fluid contained
within the heat pipe to lower it to a level which enables the
surface temperature of a coil of a linear motor to be maintained at
a desired level. Charging a heat pipe generally includes adding a
fluid such as water inside a heat pipe, or removing a fluid from a
heat pipe, to alter the boiling temperature of the heat pipe. As
shown in FIG. 2, additional fluid 230 may be added to an evaporator
end 202 of a heat pipe 200 when it is desired for the boiling
temperature associated with heat pipe 200 to be altered. Although a
process of charging heat pipe 200 may be effective in altering the
boiling temperature associated with heat pipe 200 and, hence the
temperature associated with evaporator end 202, it is generally
difficult to charge heat pipe 200 except at one time during the
manufacturing process. Thus, the boiling temperature remains
effectively constant during the use of heat pipe 200.
[0010] Some heat pipes have been designed to enable temperatures
associated with the heat pipes to be substantially controlled, even
if boiling temperatures associated with the heat pipes are
essentially not controlled. A gas-loaded, variable conductance heat
pipe, for example, may be used in some cases to enable the
temperature within a heat pipe to remain fairly constant. Allowing
the temperature within a heat pipe to remain fairly constant may
allow a heat pipe to operate more efficiently, although the
temperature at an evaporator end of such a heat pipe is generally
not changeable. FIGS. 3a and 3b are diagrammatic representations of
a gas-loaded, variable conductance heat pipe. A heat pipe 300,
which has an evaporator end 302 and a condenser end 304, includes a
gas reservoir 340 at condenser end 304. Gas contained within
reservoir 340 has a gas front 342 which moves depending upon the
temperature of vapor contained within heat pipe 300. As gas front
342 moves, the surface area of condenser end 304 varies. For
instance, as shown in FIG. 3b, when gas front 342 moves into
condenser end 304, the surface area of condenser end 304 is
decreased from the surface area of condenser end 304 as shown in
FIG. 3a.
[0011] Since the surface area of condenser end 304 varies as gas
front 342 moves, the thermal conductance of heat pipe 300 also
varies as a function of the position of gas front 342. When the
surface area of condenser end 304 increases, thermal conductance
increases, and when the surface area of condenser end 304
decreases, thermal conductance decreases. As a result, a
temperature drop across evaporator end 302 and condenser end 304 is
effectively controllable by moving gas front 342. While the
temperature drop within heat pipe 300 may be controlled such that
the temperature within heat pipe 300 may be maintained at a
substantially constant temperature, the use of heat pipe 300
generally does not enable the temperature at evaporator end 302 to
be controlled.
[0012] While the use of a heat pipe to transfer heat away from
critical components of an overall wafer stage system is typically
effective, heat pipes generally are not able to be used to readily
and efficiently allow the temperatures of heat sources to be
controlled. As discussed above, although charging a heat pipe may
enable a desired boiling temperature to be obtained within the heat
pipe, it is typically difficult to charge heat pipes except at one
time during a manufacturing process. Hence, the boiling temperature
within a heat pipe generally remains substantially constant during
the use of the heat pipe. As a result, the boiling temperature
achieved within a heat pipe may not be sufficient to maintain a
surface of a heat source at a desired temperature, since the
boiling temperature of the fluid in the heat pipe effectively
determines the constant temperature at which the evaporator end of
the heat pipe which typically contacts the heat source may be
held.
[0013] Therefore, what is needed is a method and an apparatus for
enabling the temperature at which fluid in a heat pipe boils to be
controlled. More specifically, what is desired is a method and an
apparatus for controlling the temperature of an evaporator end of a
heat pipe such that the temperature of a heat source may
effectively be controlled.
SUMMARY OF THE INVENTION
[0014] The present invention relates to a heat pipe within which
the boiling temperature of a fluid may be adjusted. According to
one aspect of the present invention, a method for controlling a
temperature associated with a heat pipe that contains a fluid and
has an evaporator end includes measuring the temperature associated
with the heat pipe and determining when the temperature associated
with the heat pipe is at a desired level. The method also includes
changing a pressure within the heat pipe when it is determined that
the temperature associated with the heat pipe is not at a desired
level. Changing the pressure within the heat pipe causes the
temperature associated with the heat pipe to change.
[0015] In one embodiment, the heat pipe includes a pressure control
mechanism, and changing the pressure within the heat pipe includes
operating the pressure control mechanism. In such an embodiment,
the pressure control mechanism may include a piston assembly, and
changing the pressure within the heat pipe may include applying a
controlled pressure using the piston assembly.
[0016] Controlling the temperature within a heat pipe effectively
allows the temperature at which heat is removed from a heat source
that is cooled by the heat pipe to be controlled. Specifically, the
temperature of the fluid may be controlled by substantially
controlling the pressure within the heat pipe. When the boiling
temperature of the fluid within the heat pipe is controlled, the
temperature of the evaporator end of the heat pipe is essentially
controlled. Hence, the temperature at which heat is removed from a
heat source, e.g., a coil of a linear motor, may be substantially
controlled by adjusting the pressure within the heat pipe.
Controlling the temperature at which heat is removed from the heat
source enables the surface temperature of the heat source to be
more readily maintained at a constant level, which enhances the
performance of an overall system, e.g., a stage apparatus, which
includes the heat source.
[0017] According to another aspect of the present invention, a heat
pipe includes an evaporator end, a fluid, and a pressure control
mechanism. The pressure control mechanism is arranged to change a
pressure within the heat pipe such that a boiling temperature of
the fluid is changed. In one embodiment, the pressure control
mechanism is arranged to change the pressure by increasing the
pressure such that the boiling temperature of the fluid is
increased. In another embodiment, the pressure control mechanism
includes a piston arrangement that applies a control pressure to
change the pressure within the heat pipe.
[0018] According to yet another aspect of the present invention, a
method for controlling a temperature of an actuator within a stage
apparatus that is in communication with an evaporator end of a heat
pipe includes determining a desired temperature for the actuator,
determining a corresponding desired temperature for the evaporator
end using the desired temperature for the actuator, and adjusting a
mechanism within the heat pipe to achieve the desired temperature
for the evaporator end. Adjusting the pressure causes a boiling
temperature of a fluid within the heat pipe to be adjusted such
that a temperature of the evaporator end is adjusted.
[0019] In one embodiment, adjusting the pressure within the heat
pipe includes applying a control force of a first amount to a
piston arrangement of the heat pipe. The control force of the first
amount is arranged to cause the piston arrangement to change the
pressure within the heat pipe. In such an embodiment, the method
may also include determining when the temperature of the evaporator
end is the desired temperature for the evaporator end. When the
temperature of the evaporator end is the desired temperature for
the evaporator end, the control force is maintained at the first
amount. Alternatively, when the temperature of the evaporator end
is not the desired temperature for the evaporator end, the pressure
within the heat pipe may be adjusted to achieve the desired
temperature for the evaporator end by applying a control force of a
second amount to the piston arrangement.
[0020] These and other advantages of the present invention will
become apparent upon reading the following detailed descriptions
and studying the various figures of the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention may best be understood by reference to the
following description taken in conjunction with the accompanying
drawings in which:
[0022] FIG. 1 is a diagrammatic representation of a conventional
heat pipe.
[0023] FIG. 2 is a diagrammatic representation of a conventional
heat pipe which is chargeable. FIG. 3a is a diagrammatic
representation of a gas-loaded, variable conductance heat pipe.
[0024] FIG. 3b is a diagrammatic representation of a gas-loaded,
variable conductance heat pipe, e.g., heat pipe 300 of FIG. 3a,
with gas from a reservoir present in a condenser section.
[0025] FIG. 4 is a diagrammatic representation of a heat pipe
within which pressure may be controlled in accordance with an
embodiment of the present invention.
[0026] FIG. 5 is a diagrammatic representation of a heat pipe
within which pressure may be controlled using a piston arrangement
in accordance with an embodiment of the present invention.
[0027] FIG. 6 is a block diagram representation of actions which
occur when a piston of a heat pipe assembly is moved in accordance
with an embodiment of the present invention.
[0028] FIG. 7 is a diagrammatic representation of a heat pipe with
a piston which serves as a pressure controller and an internal
temperature sensor in accordance with an embodiment of the present
invention.
[0029] FIG. 8 is a diagrammatic representation of a control loop
which may be used to control the temperature within a heat pipe in
accordance with an embodiment of the present invention.
[0030] FIG. 9 is a process flow diagram which illustrates one
method of controlling the temperature in a heat pipe by adjusting
the pressure in the heat pipe in accordance with an embodiment of
the present invention.
[0031] FIG. 10a is a diagrammatic representation of a piston which
is actuated by a voice coil motor in accordance with an embodiment
of the present invention.
[0032] FIG. 10b is a diagrammatic representation of a piston which
is actuated by an air bellows in accordance with an embodiment of
the present invention.
[0033] FIG. 11 is a diagrammatic representation of a
photolithography apparatus in accordance with an embodiment of the
present invention.
[0034] FIG. 12 is a process flow diagram which illustrates the
steps associated with fabricating a semiconductor device in
accordance with an embodiment of the present invention. FIG. 13 is
a process flow diagram which illustrates the steps associated with
processing a wafer, i.e., step 1304 of FIG. 12, in accordance with
an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0035] When the ambient temperature around an overall precision
stage device, e.g., an overall wafer stage device, is raised during
a wafer exposure process, the performance of the stage device may
be compromised. As a result, errors or inconsistencies may arise
during a wafer exposure process that is performed using the stage
device when the ambient temperature is raised, as for example from
a desired temperature in the range of approximately 20 to
approximately 25 degrees Celsius to a temperature in the range of
approximately 30 to approximately 40 degrees Celsius. Often, heat
which is generated by actuators associated with a stage device
causes the ambient temperature to be raised. In order to reduce the
amount by which the ambient temperature is raised by actuators such
as linear motors or motors with electromagnetic coils, heat pipes
may be used to carry heat away from the actuators to heat sinks
that absorb the heat.
[0036] Typically, heat pipes are used to enable the surface
temperature of a coil, e.g., a coil of a linear motor, to be
maintained at a particular temperature such as room temperature.
Although a heat pipe is generally effective in carrying heat away
from the coil, when the temperature at which a heat pipe operates
to transfer heat away from the coil is too high, the coil may not
be cooled sufficiently, and convection in the air surrounding the
coil may cause the air to be heated up and, hence, interfere with
the measurements made by sensors such as interferometers.
[0037] By controlling the temperature of a heat transfer medium,
e.g., a fluid, within a heat pipe, the temperature at which heat is
removed from a heat source such as an actuator may be controlled.
In one embodiment, the temperature of the heat transfer medium,
particularly at an evaporator end of a heat pipe, may be controlled
by substantially controlling the pressure within the heat pipe.
Controlling the pressure within the heat pipe enables the boiling
temperature of fluid within the heat pipe to be controlled, which
effectively enables the temperature of the evaporator end of the
heat pipe to be controlled. As a result, the temperature at which
heat is removed from a heat source, e.g., a coil of a linear motor,
may be substantially controlled by adjusting the pressure within
the heat pipe. Controlling the temperature at which heat is removed
from the heat source enables the surface temperature of the heat
source to be more readily maintained at a constant level.
[0038] FIG. 4 is a diagrammatic representation of a heat pipe
within which pressure may be controlled in accordance with an
embodiment of the present invention. A heat pipe 404 may be
arranged between a heat source 416, e.g., heat generating coils of
an actuator, and a heat sink 420, e.g., the environment surrounding
heat pipe 404. Specifically, heat source 416 is positioned at an
evaporator end 408 of heat pipe 404, while heat sink 420 is
positioned at a condenser end 412 of heat pipe 404. A pressure
control mechanism 424, which is effectively a part of heat pipe
404, is arranged to enable the pressure within heat pipe 404 to be
varied. Pressure control mechanism 424 may generally be positioned
substantially anywhere with respect to heat pipe 404. In one
embodiment, pressure control mechanism 424 may be a piston which is
subjected to a control force, as will be described below with
respect to FIG. 5. It should be appreciated, however, that pressure
control mechanism 424 may generally be substantially any mechanism
which enables the pressure within heat pipe 404 to be varied.
[0039] Typically, by increasing the pressure within heat pipe 404,
the boiling temperature of a fluid which is either in a liquid
state or a gas-liquid state may be increased. On the other hand, by
decreasing the pressure within heat pipe 404, the boiling
temperature of the fluid which is either in a liquid state or a
gas-liquid state may be lowered. When the boiling point or
temperature of the fluid within heat pipe 404 changes, then the
temperature at evaporator end 408, which generally contains the
fluid in a liquid state, changes. As such, changing the boiling
temperature of the fluid changes the temperature of evaporator end
408 and, hence, the temperature at which heat source 416 may be
maintained may effectively be changed, since heat source 416 is
generally in communication with evaporator end 408. By way of
example, when the pressure within heat pipe 404 increases and the
boiling temperature of the fluid within heat pipe 404 5 increases,
then heat generated by heat source 416 may be substantially
dissipated by heat pipe 404 at a higher temperature. Hence,
allowing the boiling temperature of fluid within heat pipe 404 to
be substantially controlled using pressure control mechanism 424
allows the temperature associated with evaporator end 408 and the
temperature of heat source 416 to be controlled.
[0040] As mentioned above, one suitable pressure control mechanism
424 is a piston mechanism. Referring next to FIG. 5, one embodiment
of a heat pipe within which pressure may be controlled using a
piston will be described in accordance with an embodiment of the
present invention. A heat pipe 504 which includes an evaporator end
508 and a condenser end 512 is positioned between a heat source 516
and a heat sink 520 such that heat source 516 is located at
evaporator end 508 and heat sink 520 is located at condenser end
512. A piston 514 is positioned with respect to heat pipe 504 such
that when a control force 530, which may be applied through an
actuator that is controlled by a control mechanism, is applied to
piston 514, piston 514 may cause a pressure within heat pipe 504,
i.e., an internal pressure of heat pipe 504, to change. Piston 514
may cause the pressure within heat pipe 504 to change by
effectively applying a control pressure within heat pipe 504. In
order to prevent fluid from escaping from heat pipe 504, a
diaphragm (not shown) may be used in one embodiment to effectively
create a seal that prevents fluid from leaking out from heat pipe
504 through any gaps which are present between piston 514 and heat
pipe 504. It should be appreciated that applying a control pressure
within heat pipe 504 may also cause at least a slight volume change
within heat pipe 504.
[0041] Piston 514 generally has an associated surface area which
effectively comes into contact with an interior of heat pipe 504.
As such, the control pressure applied by piston 514 may be
expressed as a function of control force 530 and the contact area
of piston 514. Hence, by increasing control force 530, the control
pressure applied by piston 514 may be increased, and the pressure
within heat pipe 504 may rise. Generally, when control force 530 is
applied in a negative y-direction 540, piston 514 moves in negative
y-direction 540 and causes the pressure within heat pipe 504 to
increase. Alternatively, when control force 530 is applied in a
positive y-direction 540, piston moves in positive y-direction 540
and typically causes the pressure within heat pipe 504 to
decrease.
[0042] With reference to FIG. 6, the actions which occur when a
piston of a heat pipe assembly is moved will be discussed in
accordance with an embodiment of the present invention. When the
force applied to a piston of a heat pipe, e.g., piston 514 of FIG.
5, is adjusted in action 610, the pressure within the heat pipe
changes in action 614. By way of example, when the force applied to
the piston is increased, the pressure within the heat pipe may
increase. A change in pressure within the heat pipe causes the
boiling temperature of the fluid in the heat pipe to change in
action 618. At a given pressure, when the fluid in the heat pipe is
in a gas-liquid state, changing the pressure within the heat pipe
changes the boiling temperature of the fluid, as will be
appreciated by those skilled in the art. For an embodiment in which
the pressure within the heat pipe is increased, the boiling
temperature of the fluid in the heat pipe typically increases.
[0043] Once the boiling temperature of the fluid in the heat pipe
changes, the temperature at the evaporator end of the heat pipe
changes in action 622. Since the evaporator end of the heat pipe is
generally in the vicinity of a heat source, by changing the
temperature at the evaporator end of the heat pipe, the temperature
at which heat is removed from the heat source is also changed.
[0044] To monitor the temperature of the fluid in the heat pipe or,
more particularly, the evaporator end of a heat pipe, in order to
ascertain whether the boiling temperature of fluid within the heat
pipe is at a desired level or needs to be changed to reach the
desired level, a temperature sensor may be positioned within the
heat pipe. FIG. 7 is a diagrammatic representation of a heat pipe
with a piston which serves as a pressure controller and an internal
temperature sensor in accordance with an embodiment of the present
invention. A heat pipe 602 includes a piston 614 which is
controlled by a force 618. To determine an appropriate amount of
force 618 to apply to piston 614 to achieve a desired boiling
temperature within heat pipe 602, a temperature sensor 640 may be
positioned at an evaporator end 606 of heat pipe 602. Temperature
sensor 640 may generally be used to measure a temperature of fluid
within heat pipe 602, and may be substantially any suitable
temperature sensor 640. Suitable temperature sensors or transducers
may include, but are not limited to, thermometers such as
thermocouple thermometers, and thermistor thermometers, as well as
thermoelectric sensors and resistive temperature sensors.
[0045] Output from temperature sensor 640 may be provided to a
controller which provides force 618 such that the magnitude of
force 618 may be adjusted as appropriate to create a pressure
within heat pipe 602 which is suitable for causing a temperature
within heat pipe 602 to be raised or lowered. As shown in FIG. 8,
which is a diagrammatic block diagram representation of one
suitable control loop which may be used to control the temperature
within a heat pipe such as heat pipe 602, a desired temperature 802
for an evaporator end of a heat pipe is provided as a control input
in a control loop 800. The desired temperature 802 is provided to a
controller 806, e.g., by a user who specifies desired parameters of
the heat pipe, which controls an actuator 808 that provides a
control force to a piston of the heat pipe. In one embodiment,
actuator 808 may be a voice coil motor, a linear motor, or
substantially any electromagnetic actuator.
[0046] A measured temperature 810, which may be provided by a
temperature sensor within the heat pipe, is also provided as an
input to controller 806. Using desired temperature 802 and measured
temperature 810, controller 806 may determine an appropriate
amount, or level, of force to be exerted by actuator 808 on a
piston of the heat pipe to enable measured temperature 810 to be
approximately the same as desired temperature 802. It should be
appreciated that controller 806 may substantially continuously
adjust actuator 808 as necessary and, hence, the pressure within
the heat pipe, as needed to effectively maintain measured
temperature 810 at a level that is approximately the same as
desired temperature 802.
[0047] Referring next to FIG. 9, one method of controlling the
temperature in a heat pipe by adjusting the pressure in the heat
pipe will be described in accordance with an embodiment of the
present invention. A process 900 of controlling the temperature in
a heat pipe begins at step 902 in which a determination is made
regarding what the desired temperature for the evaporator end of
the heat pipe is. Determining what the desired temperature is may
include obtaining a desired temperature from a user of the heat
pipe, or determining a desired temperature based upon the
requirements of an overall stage apparatus which uses the heat
pipe. For example, a desired surface temperature for an actuator
which is being cooled using the heat pipe may be used to determine
a corresponding desired temperature for the evaporator end of the
heat pipe. It should be appreciated that although the desired
temperature for the evaporator end of the heat pipe may be the same
as the desired temperature for the actuator, the two desired
temperatures may also vary.
[0048] After the desired temperature is determined, the temperature
at an evaporator end of the heat pipe may be measured in step 906.
Although the temperature is typically measured within the heat pipe
at an evaporator end to enable a desired temperature to be
maintained at the evaporator end, it should be appreciated that the
temperature within the heat pipe may be measured substantially
anywhere within the heat pipe. Alternatively, the temperature of
the actuator, some other temperature, or a performance parameter
related to the temperature of the actuator, e.g., air turbulence or
sensor noise, may be measured. Once the temperature within the heat
pipe is measured, it is determined in step 908 whether the
temperature at the evaporator end of the heat pipe is as desired.
If it is determined that the temperature at the evaporator end of
the heat pipe is as desired, then the indication is that the
pressure within the heat pipe is sufficient for maintaining the
boiling point of liquid within the heat pipe at a desired
temperature. Accordingly, in step 912, the current control force
applied to the piston of the heat pipe is maintained at it current
level. That is, the actuator which causes the control force to be
applied to the piston effectively does not change the amount of
control force that is applied to the piston. From step 912, process
flow returns to step 906 in which the temperature at the evaporator
end of the heat pipe is measured.
[0049] Returning to step 908, if it is determined that the
temperature at the evaporator end of the heat pipe is not as
desired, then the implication may be that the pressure within the
heat pipe is either too high or too low for the desired temperature
to be achieved. For example, if the temperature at the evaporator
end of the heat pipe is too high, then the pressure in the heat
pipe is likely to be too high to enable the desired temperature at
the evaporator end to be achieved. As such, from step 908, process
flow moves to step 910 in which the control force applied to the
piston of the heat pipe, e.g., using an actuator, is adjusted to
adjust the pressure within the heat pipe. Typically, the adjustment
made to the control force is arranged to be sufficient to alter the
pressure within the heat by an amount that is sufficient to achieve
the desired temperature at the evaporator end of the heat pipe.
Once the control force is adjusted, process flow returns to step
906 in which the temperature at the evaporator end of the heat pipe
is measured.
[0050] In general, an actuator used to vary the force applied to a
piston of a heat pipe may be substantially any suitable actuator
that may be controlled, as for example by a controller which sends
signals to the actuator to alter the force generated by the
actuator. By way of example, an actuator which is coupled to the
piston of the heat pipe may be a motor such as a voice coil motor
(VCM). FIG. 10a is a diagrammatic representation of a piston which
is actuated by a VCM in accordance with an embodiment of the
present invention. A heat pipe 950 includes a piston 944 which is
coupled to a VCM 930. As shown, a body 934 of VCM 930 is coupled to
piston 944 such that magnets 936 in cooperation with a coil 932
cause body 934 to move and create a force on piston 944. Often,
forces on piston 944 created by VCM 930 may either cause piston 944
to be moved in a positive y-direction 948, or in a negative
y-direction 948. A diaphragm 940 or similar mechanism may be
arranged to prevent fluid contained in an interior 954 of heat pipe
950 from leaking around piston 944 and out of heat pipe 950. As
piston 944 moves, the pressure within interior 954 may change as a
function of the force applied by VCM 930 on piston 944 and the area
of piston 944.
[0051] Another actuator which may be used to apply force to a
piston of a heat pipe is an air bellows. FIG. 10b is a diagrammatic
representation of a piston which is actuated by an air bellows in
accordance with an embodiment of the present invention. A heat pipe
980 includes a piston 974 which may be sealed using a diaphragm 970
to prevent leakage of fluid contained in an interior 984 of heat
pipe 980. Piston 974 may be coupled to an air bellows 960 which may
be used to alter a control force applied to piston 974 and, hence,
the pressure within interior 984. Typically, the amount of force
applied by air bellows 960 onto piston 974 may be varied by
altering the air pressure within bellows 960. As a result, movement
of piston 974 in a y-direction 968 may be controlled by controlling
the air pressure within bellows 960.
[0052] A heat pipe with a controllable internal temperature may
generally be incorporated as part of an apparatus such as a
photolithography apparatus. By way of example, a heat pipe with
temperature control may be applied to a coil of an electromagnetic
actuator in a photolithography apparatus, or a heat pipe with
temperature control may be connected to a linear motor within the
photolithography apparatus. With reference to FIG. 11, a
photolithography apparatus which may include a heat pipe with
temperature control will be described in accordance with an
embodiment of the present invention. A photolithography apparatus
(exposure apparatus) 40 includes a wafer positioning stage 52 that
may be driven by a planar motor (not shown), as well as a wafer
table 51 that is magnetically coupled to wafer positioning stage 52
by utilizing an EI-core actuator. The planar motor which drives
wafer positioning stage 52 generally uses an electromagnetic force
generated by magnets and corresponding armature coils arranged in
two dimensions. A wafer 64 is held in place on a wafer holder or
chuck 74 which is coupled to wafer table 51. Wafer positioning
stage 52 is arranged to move in multiple degrees of freedom, e.g.,
between three to six degrees of freedom, under the control of a
control unit 60 and a system controller 62. The movement of wafer
positioning stage 52 allows wafer 64 to be positioned at a desired
position and orientation relative to a projection optical system
46. Heat generated during the movement of wafer positioning stage
52 may be stored by a heat pipe (not shown) that is coupled to
wafer positioning stage 52.
[0053] Wafer table 51 may be levitated in a z-direction 10b by any
number of voice coil motors (not shown), e.g., three voice coil
motors. In the described embodiment, at least three magnetic
bearings (not shown) couple and move wafer table 51 along a y-axis
10a. The motor array of wafer positioning stage 52 is typically
supported by a base 70. Base 70 is supported to a ground via
isolators 54. Reaction forces generated by motion of wafer stage 52
may be mechanically released to a ground surface through a frame
66. One suitable frame 66 is described in JP Hei 8-166475 and U.S.
Pat. No. 5,528,118, which are each herein incorporated by reference
in their entireties.
[0054] An illumination system 42 is supported by a frame 72. Frame
72 is supported to the ground via isolators 54. Illumination system
42 includes an illumination source, and is arranged to project a
radiant energy, e.g., light, through a mask pattern on a reticle 68
that is supported by and scanned using a reticle stage which
includes a coarse stage and a fine stage. The radiant energy is
focused through projection optical system 46, which is supported on
a projection optics frame 50 and may be supported the ground
through isolators 54. Suitable isolators 54 include those described
in JP Hei 8-330224 and U.S. Pat. No. 5,874,820, which are each
incorporated herein by reference in their entireties.
[0055] A first interferometer 56 is supported on projection optics
frame 50, and functions to detect the position of wafer table 51.
Interferometer 56 outputs information on the position of wafer
table 51 to system controller 62. In one embodiment, wafer table 51
has a force damper which reduces vibrations associated with wafer
table 51 such that interferometer 56 may accurately detect the
position of wafer table 51. A second interferometer 58 is supported
on projection optical system 46, and detects the position of
reticle stage 44 which supports a reticle 68. Interferometer 58
also outputs position information to system controller 62.
[0056] It should be appreciated that there are a number of
different types of photolithographic apparatuses or devices. For
example, photolithography apparatus 40, or an exposure apparatus,
may be used as a scanning type photolithography system which
exposes the pattern from reticle 68 onto wafer 64 with reticle 68
and wafer 64 moving substantially synchronously. In a scanning type
lithographic device, reticle 68 is moved perpendicularly with
respect to an optical axis of a lens assembly (projection optical
system 46) or illumination system 42 by reticle stage 44. Wafer 64
is moved perpendicularly to the optical axis of projection optical
system 46 by a wafer stage 52. Scanning of reticle 68 and wafer 64
generally occurs while reticle 68 and wafer 64 are moving
substantially synchronously.
[0057] Alternatively, photolithography apparatus or exposure
apparatus 40 may be a step-and-repeat type photolithography system
that exposes reticle 68 while reticle 68 and wafer 64 are
stationary. In one step and repeat process, wafer 64 is in a
substantially constant position relative to reticle 68 and
projection optical system 46 during the exposure of an individual
field. Subsequently, between consecutive exposure steps, wafer 64
is consecutively moved by wafer positioning stage 52
perpendicularly to the optical axis of projection optical system 46
and reticle 68 for exposure. Following this process, the images on
reticle 68 may be sequentially exposed onto the fields of wafer 64
so that the next field of semiconductor wafer 64 is brought into
position relative to illumination system 42, reticle 68, and
projection optical system 46.
[0058] It should be understood that the use of photolithography
apparatus or exposure apparatus 40, as described above, is not
limited to being used in a photolithography system for
semiconductor manufacturing. For example, photolithography
apparatus 40 may be used as a part of a liquid crystal display
(LCD) photolithography system that exposes an LCD device pattern
onto a rectangular glass plate or a photolithography system for
manufacturing a thin film magnetic head.
[0059] The illumination source of illumination system 42 may be
g-line (436 nanometers (nm)), i-line (365 nm), a KrF excimer laser
(248 nm), an ArF excimer laser (193 nm), and an F.sub.2-type laser
(157 nm). Alternatively, illumination system 42 may also use
charged particle beams such as x-ray and electron beams. For
instance, in the case where an electron beam is used, thermionic
emission type lanthanum hexaboride (LaB.sub.6) or tantalum (Ta) may
be used as an electron gun. Furthermore, in the case where an
electron beam is used, the structure may be such that either a mask
is used or a pattern may be directly formed on a substrate without
the use of a mask.
[0060] With respect to projection optical system 46, when far
ultra-violet rays such as an excimer laser is used, glass materials
such as quartz and fluorite that transmit far ultra-violet rays is
preferably used. When either an F.sub.2-type laser or an x-ray is
used, projection optical system 46 may be either catadioptric or
refractive (a reticle may be of a corresponding reflective type),
and when an electron beam is used, electron optics may comprise
electron lenses and deflectors. As will be appreciated by those
skilled in the art, the optical path for the electron beams is
generally in a vacuum.
[0061] In addition, with an exposure device that employs vacuum
ultra-violet (VUV) radiation of a wavelength that is approximately
200 nm or lower, use of a catadioptric type optical system may be
considered. Examples of a catadioptric type of optical system
include, but are not limited to, those described in Japan Patent
Application Disclosure No. 8-171054 published in the Official
gazette for Laid-Open Patent Applications and its counterpart U.S.
Pat. No. 5,668,672, as well as in Japan Patent Application
Disclosure No. 10-20195 and its counterpart U.S. Pat. No.
5,835,275, which are all incorporated herein by reference in their
entireties. In these examples, the reflecting optical device may be
a catadioptric optical system incorporating a beam splitter and a
concave mirror. Japan Patent Application Disclosure (Hei) No.
8-334695 published in the Official gazette for Laid-Open Patent
Applications and its counterpart U.S. Pat. No. 5,689,377, as well
as Japan Patent Application Disclosure No. 10-3039 and its
counterpart U.S. Pat. No. 5,892,117, which are all incorporated
herein by reference in their entireties. These examples describe a
reflecting-refracting type of optical system that incorporates a
concave mirror, but without a beam splitter, and may also be
suitable for use with the present invention.
[0062] Further, in photolithography systems, when linear motors
(see U.S. Pat. Nos. 5,623,853 or 5,528,118, which are each
incorporated herein by reference in their entireties) are used in a
wafer stage or a reticle stage, the linear motors may be either an
air levitation type that employs air bearings or a magnetic
levitation type that uses Lorentz forces or reactance forces.
Additionally, the stage may also move along a guide, or may be a
guideless type stage which uses no guide.
[0063] Alternatively, a wafer stage or a reticle stage may be
driven by a planar motor which drives a stage through the use of
electromagnetic forces generated by a magnet unit that has magnets
arranged in two dimensions and an armature coil unit that has coil
in facing positions in two dimensions. With this type of drive
system, one of the magnet unit or the armature coil unit is
connected to the stage, while the other is mounted on the moving
plane side of the stage.
[0064] Movement of the stages as described above generates reaction
forces which may affect performance of an overall photolithography
system. Reaction forces generated by the wafer (substrate) stage
motion may be mechanically released to the floor or ground by use
of a frame member as described above, as well as in U.S. Pat. No.
5,528,118 and published Japanese Patent Application Disclosure No.
8-166475. Additionally, reaction forces generated by the reticle
(mask) stage motion may be mechanically released to the floor
(ground) by use of a frame member as described in U.S. Pat. No.
5,874,820 and published Japanese Patent Application Disclosure No.
8-330224, which are each incorporated herein by reference in their
entireties.
[0065] Isolaters such as isolators 54 may generally be associated
with an active vibration isolation system (AVIS). An AVIS generally
controls vibrations associated with forces 112, i.e., vibrational
forces, which are experienced by a stage assembly or, more
generally, by a photolithography machine such as photolithography
apparatus 40 which includes a stage assembly.
[0066] A photolithography system according to the above-described
embodiments, e.g., a photolithography apparatus which may include
one or more heat pipes, may be built by assembling various
subsystems in such a manner that prescribed mechanical accuracy,
electrical accuracy, and optical accuracy are maintained. In order
to maintain the various accuracies, prior to and following
assembly, substantially every optical system may be adjusted to
achieve its optical accuracy. Similarly, substantially every
mechanical system and substantially every electrical system may be
adjusted to achieve their respective desired mechanical and
electrical accuracies. The process of assembling each subsystem
into a photolithography system includes, but is not limited to,
developing mechanical interfaces, electrical circuit wiring
connections, and air pressure plumbing connections between each
subsystem. There is also a process where each subsystem is
assembled prior to assembling a photolithography system from the
various subsystems. Once a photolithography system is assembled
using the various subsystems, an overall adjustment is generally
performed to ensure that substantially every desired accuracy is
maintained within the overall photolithography system.
Additionally, it may be desirable to manufacture an exposure system
in a clean room where the temperature and humidity are
controlled.
[0067] Further, semiconductor devices may be fabricated using
systems described above, as will be discussed with reference to
FIG. 12. The process begins at step 1301 in which the function and
performance characteristics of a semiconductor device are designed
or otherwise determined. Next, in step 1302, a reticle (mask) in
which has a pattern is designed based upon the design of the
semiconductor device. It should be appreciated that in a parallel
step 1303, a wafer is made from a silicon material. The mask
pattern designed in step 1302 is exposed onto the wafer fabricated
in step 1303 in step 1304 by a photolithography system. One process
of exposing a mask pattern onto a wafer will be described below
with respect to FIG. 13. In step 1305, the semiconductor device is
assembled. The assembly of the semiconductor device generally
includes, but is not limited to, wafer dicing processes, bonding
processes, and packaging processes. Finally, the completed device
is inspected in step 1306.
[0068] FIG. 13 is a process flow diagram which illustrates the
steps associated with wafer processing in the case of fabricating
semiconductor devices in accordance with an embodiment of the
present invention. In step 1311, the surface of a wafer is
oxidized. Then, in step 1312 which is a chemical vapor deposition
(CVD) step, an insulation film may be formed on the wafer surface.
Once the insulation film is formed, in step 1313, electrodes are
formed on the wafer by vapor deposition. Then, ions may be
implanted in the wafer using substantially any suitable method in
step 1314. As will be appreciated by those skilled in the art,
steps 1311-1314 are generally considered to be preprocessing steps
for wafers during wafer processing. Further, it should be
understood that selections made in each step, e.g., the
concentration of various chemicals to use in forming an insulation
film in step 1312, may be made based upon processing
requirements.
[0069] At each stage of wafer processing, when preprocessing steps
have been completed, post-processing steps may be implemented.
During post-processing, initially, in step 1315, photoresist is
applied to a wafer. Then, in step 1316, an exposure device may be
used to transfer the circuit pattern of a reticle to a wafer.
Transferring the circuit pattern of the reticle of the wafer
generally includes scanning a reticle scanning stage which may, in
one embodiment, include a force damper to dampen vibrations.
[0070] After the circuit pattern on a reticle is transferred to a
wafer, the exposed wafer is developed in step 1317. Once the
exposed wafer is developed, parts other than residual photoresist,
e.g., the exposed material surface, may be removed by etching.
Finally, in step 1319, any unnecessary photoresist that remains
after etching may be removed. As will be appreciated by those
skilled in the art, multiple circuit patterns may be formed through
the repetition of the preprocessing and post-processing steps.
[0071] Although only a few embodiments of the present invention
have been described, it should be understood that the present
invention may be embodied in many other specific forms without
departing from the spirit or the scope of the present invention. By
way of example, although a heat pipe has been described as
including a pressure controller which is a piston, a pressure
controller may be substantially any mechanism which enables
pressure within the heat pipe to be controlled. In other words, a
pressure controller on a heat pipe may not necessarily be a
piston.
[0072] A heat pipe with an internal temperature which may be
controlled by controlling the pressure within the heat pipe may be
used for a variety of different application. For instance, as
described above, a heat pipe with an internal temperature which is
controllable may be used within a photolithography apparatus to
cool linear motors, voice coil motors, or substantially any other
electromagnetic actuator. It should be appreciated, however, that
such a heat pipe may generally be used to cool substantially any
mechanism or device which would benefit from being cooled.
[0073] While a pressure control mechanism such as a piston has been
shown as being positioned near a condenser end of a heat pipe, a
pressure control mechanism may generally be positioned
substantially anywhere with respect to the heat pipe. Positioning
the pressure control mechanism closer to a condenser end of the
heat pipe, which contains mostly gas or vapors, may enable the
pressure control mechanism to be more readily actuated. However,
the pressure control mechanism may instead be located near a middle
portion of a heat pipe, or closer to an evaporator end of the heat
pipe in some embodiments.
[0074] Changing the pressure within a heat pipe may, in some cases,
cause an appreciable change in the interior volume of the heat
pipe. Conversely, changing the interior volume of a heat pipe may
lead to a change in pressure within the heat pipe. As such, it
should be appreciated that the internal volume of the heat pipe may
effectively be changed, e.g., by displacing a piston of the heat
pipe, to cause a change in pressure within the heat pipe that leads
to a change in the boiling temperature of fluid in the heat
pipe.
[0075] In general, the steps associated with the methods of the
present invention may vary widely. Steps may be added, removed,
altered, and reordered without departing from the spirit or the
scope of the present invention. For example, a process of
controlling the temperature within a heat pipe may include at least
periodically determining a desired temperature within the heat
pipe. Periodically determining a desired temperature within the
heat pipe enables changes to requirements associated with an
overall stage apparatus to be accounted for, as the control force
applied to a piston of a heat pipe may be adjusted to compensate
for any change to a desired temperature. Therefore, the present
examples are to be considered as illustrative and not restrictive,
and the invention is not to be limited to the details given herein,
but may be modified within the scope of the appended claims.
* * * * *