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| United States Patent |
5,706,890
|
|
Sloan
, et al.
|
January 13, 1998
|
Temperature control apparatus with recirculated coolant
Abstract
A temperature control and process for adjusting the temperature of a
workstation and a work medium at a workstation to a predetermined
temperature. The temperature control comprises a cooling vehicle such as a
heat exchanger, a coolant temperature sensor and control, a source of
fluid coolant such as a manifold, a recirculating pump, a flow line to
circulate the coolant to the workstation with the flow line containing a
flow regulator and a heater, a bypass valve for bypassing the flow
regulator and heater, and a workstation temperature sensor and control.
The workstation temperature control controls the operation of the heater
and bypass valve so that the temperature of the coolant is below the
desired temperature for the workstation, thus achieving a rapid transient
response while avoiding overcooling. The coolant temperature control and
workstation temperature control may be in a temperature control computer,
thus providing a large number of different operating sequences. A number
of embodiments of workstations are also described.
| Inventors:
|
Sloan; Ben J. (Garland, TX);
Reed; William G. (Richardson, TX)
|
| Assignee:
|
FSI International, Inc. (Chaska, MN)
|
| Appl. No.:
|
184681 |
| Filed:
|
January 21, 1994 |
| Intern'l Class: |
F25B 029/00 |
| Field of Search: |
165/30,34,104.33,263,264,206,290,61,64,80.4
|
References Cited
U.S. Patent Documents
| 3227207 | Jan., 1966 | Litman | 165/11.
|
| 3229754 | Jan., 1966 | Hoag | 165/30.
|
| 3236292 | Feb., 1966 | Smith, Jr. | 165/30.
|
| 3360032 | Dec., 1967 | Sherwood | 165/30.
|
| 3612165 | Oct., 1971 | Haynes | 165/264.
|
| 3645697 | Feb., 1972 | Hoffman, Jr. | 23/253.
|
| 4072181 | Feb., 1978 | Kostura et al. | 165/30.
|
| 4621678 | Nov., 1986 | Hahn et al. | 165/34.
|
| 4651813 | Mar., 1987 | Witt et al. | 165/30.
|
| 4729424 | Mar., 1988 | Mizuno et al. | 165/30.
|
| 4789025 | Dec., 1988 | Brandemuehl et al. | 165/264.
|
| 4984628 | Jan., 1991 | Uchida et al. | 165/30.
|
| 5226472 | Jul., 1993 | Benevelli et al. | 165/263.
|
| 5348076 | Sep., 1994 | Asakawa | 165/104.
|
Other References
"Polaris 2000 Microlithography Cluster" data sheet and drawings, FSI
International (1994).
Sematech publication, "Chill plates", 4 pages (no date).
|
Primary Examiner: Ford; John K.
Attorney, Agent or Firm: Palmatier, Sjoquist, Helget & Voigt, P.A.
Claims
What is claimed:
1. A temperature control for adjusting the temperature of a workstation and
a work medium at a workstation to a predetermined temperature, comprising:
a source of fluid coolant,
a cooling vehicle, main coolant temperature sensor and main coolant
temperature control for detecting and maintaining the temperature of the
fluid coolant at a temperature below said predetermined temperature,
a flow line, a return line, and a recirculating pump for receiving fluid
coolant from said source of fluid coolant and providing fluid coolant to
the workstation and producing cooling of the workstation and work medium
therein,
a workstation temperature sensor and workstation temperature control for
detecting and regulating the temperature of the workstation,
a coolant heater in said flow line responsive to said workstation
temperature control for heating the coolant being supplied to the
workstation to a temperature nearly equal to said predetermined
temperature as to maintain the workstation and work medium at said
predetermined temperature,
said workstation temperature control reducing the heating by said heater
while a substantial differential exists between the workstation
temperature and said predetermined temperature, and said workstation
temperature control increasing the heating by said heater as said
differential decreases and as the workstation temperature nearly achieves
said predetermined temperature,
a flow regulator in said flow line for maintaining the desired rate of flow
of coolant through said flow line, and
a bypass valve for bypassing both said heater and said flow regulator,
thereby providing a flow of unwarmed coolant to the workstation at an
increased rate of flow, said bypass valve being responsive to said
workstation temperature control.
2. A temperature control as in claim 1, wherein said main coolant
temperature control and said workstation temperature control are a
temperature control computer.
3. A temperature control as in claim 1, wherein said temperature control
controls the temperature of a plurality of workstations and work media
therein.
4. A temperature control for adjusting the temperature of a workstation and
a work medium at a workstation to a predetermined temperature, comprising:
a workstation,
a source of fluid coolant,
a cooling vehicle, main coolant temperature sensor and main coolant
temperature control for detecting and maintaining the temperature of the
fluid coolant at a temperature below said predetermined temperature,
a flow line, a return line, and a recirculating pump for receiving fluid
coolant from said source of fluid coolant and providing fluid coolant to
the workstation and producing cooling of the workstation and work medium
therein,
a workstation temperature sensor and workstation temperature control for
detecting and regulating the temperature of the workstation,
a coolant heater in said flow line responsive to said workstation
temperature control for heating the coolant being supplied to the
workstation to a temperature nearly equal to said predetermined
temperature as to maintain the workstation and work medium at said
predetermined temperature,
said workstation temperature control reducing the heating by said heater
while a substantial differential exists between the workstation
temperature and said predetermined temperature, and
said workstation temperature control increasing the heating by said heater
as said differential decreases and as the workstation temperature nearly
achieves said predetermined temperature,
a flow regulator in said flow line for maintaining the desired rate of flow
of coolant through said flow line, and
a bypass valve for bypassing both said heater and said flow regulator,
thereby providing a flow of unwarmed coolant to the workstation at an
increased rate of flow, said bypass valve being responsive to said
workstation temperature control.
5. A temperature control as in claim 4, wherein said workstation comprises
a cooling plate for supporting a wafer whose temperature is to be
regulated.
6. A temperature control as in claim 4, wherein said workstation comprises
a module having an upper compartment, a lower compartment, and a cooling
plate separating said upper compartment from said lower compartment, said
module regulating the temperature of materials in said upper compartment
and said lower compartment.
7. A temperature control as in claim 4, wherein said main coolant
temperature control and said workstation temperature control are a
temperature control computer.
8. A temperature control as in claim 4, wherein said temperature control
controls the temperature of a plurality of workstations and work media
therein.
9. A temperature control for adjusting the temperature of a workstation and
a work medium at a workstation to a predetermined temperature, comprising:
workstation temperature sensing means to determine the temperature of the
workstation,
a source of fluid coolant and means for maintaining the fluid coolant at a
temperature below said predetermined temperature,
coolant circulating means comprising a flow line delivering coolant from
said source and to and through the workstation and adjusting the
temperature of the workstation and work medium therein,
a coolant heater in the flow line heating the coolant being supplied to the
workstation to a temperature nearly equal to said predetermined
temperature as to maintain the workstation and work medium at said
predetermined temperature,
control means for the heater and modulating the heating thereof, said
control means reducing the heating by said heater while a substantial
differential exists between the workstation temperature and said
predetermined temperature, and said control means increasing the heating
by said heater as said differential decreases and as the workstation
temperature nearly achieves said predetermined temperature; means for
regulating the flow of coolant in the flow line; and means for bypassing
said flow regulating means and said heater, and wherein said control means
controls said bypass means.
10. A temperature control as in claim 9, wherein said control means is a
temperature control computer, and the computer's program controls said
heater and said bypass means.
11. A temperature control as in claim 9, wherein said temperature control
controls the temperature of a plurality of workstations and work media
therein.
12. A temperature control for adjusting the temperature of a workstation
and a work medium at a workstation to a predetermined temperature,
comprising:
a workstation,
workstation temperature sensing means to determine the temperature of the
workstation,
a source of fluid coolant and means for maintaining the fluid coolant at a
temperature below said predetermined temperature,
coolant circulating means comprising a flow line delivering coolant from
said source and to and through the workstation and producing cooling of
the workstation and work medium therein,
a coolant heater in the flow line heating the coolant being supplied to the
workstation to a temperature nearly equal to said predetermined
temperature as to maintain the workstation and work medium at said
predetermined temperature,
control means for the heater and modulating the heating thereof, said
control means reducing the heating by said heater while a substantial
differential exists between the workstation temperature and said
predetermined temperature, and said control means increasing the heating
by said heater as said differential decreases and as the workstation
temperature nearly achieves said predetermined temperature; means for
regulating the flow of coolant in the flow line; and means for bypassing
said flow regulating means and said heater, and wherein said control means
controls said bypass means.
13. A temperature control as in claim 12, wherein said control means is a
temperature control computer, and the computer's program controls said
heater and said bypass means.
14. A temperature control as in claim 12, wherein said workstation
comprises a cooling plate for supporting a wafer whose temperature is to
be regulated.
15. A temperature control as in claim 12, wherein said workstation
comprises a module having an upper compartment, a lower compartment, and a
cooling plate separating said upper compartment from said lower
compartment, said module regulating the temperature of materials in said
upper compartment and said lower compartment.
Description
This invention relates to a temperature control apparatus and method with
recirculated coolant for rapidly cooling a workstation with a work medium
or workpiece to a set temperature.
BACKGROUND OF THE INVENTION
Applications such as photoresist processing on semiconductor wafers require
very precise temperature control of chemicals and silicon wafers. To
achieve such precise control of temperatures, temperature controls with
recirculated coolant are used.
Most temperature controls of this type use a recirculated coolant, such as
water, for temperature control at or around room temperature. Most such
temperature controls require large flow rates in order to achieve rapid
transient response, since the coolant is set at the temperature to be
achieved in the material being controlled and heat transfer near the set
point is very slow. Most such temperature controls also require multiple
circulators to achieve temperature control of multiple workstations at
different temperatures.
SUMMARY OF THE INVENTION
An object of the invention is to provide a temperature control with rapid
transient response with minimal flow rates.
A second object of the invention is to provide a temperature control which
uses only one circulator to achieve control of temperature of multiple
workstations.
A feature of the invention is the apparatus for producing cooling at a
workstation sufficient to rapidly bring the workstation and a solid or
fluid work medium therein to a predetermined temperature, i.e., for
achieving a rapid transient response, i.e., the time required to cool the
workstation from its initial temperature to a temperature closely
approaching that desired. Such rapid cooling is achieved by introducing
into the workstation a coolant at a lower temperature than the
predetermined temperature, and by adding heat to the coolant in its flow
line as the temperature in the workstation nearly simulates the desired
predetermined temperature.
Another feature of the invention is the apparatus for adjusting the
temperature of a workstation, thus providing the ability to set the
workstation temperature below, at, or above the ambient temperature.
Another feature of the invention is the apparatus for circulating coolant
to multiple workstations with only one circulator. Having only one
circulator for multiple workstations increases reliability and reduces
cost versus multiple circulator approaches.
Another feature of the invention is the apparatus for adjusting the
temperature of multiple workstations. In this way, each workstation may
have a separate set point temperature below, at, or above its ambient
temperature.
Still another feature of the invention is the method of providing control
of temperature to multiple workstations, wherein rapid transient response
is achieved by momentarily introducing a flow of unwarmed coolant to the
workstations, wherein only one circulator is used, and wherein the coolant
temperature is slightly below the temperature of the workstations, the
coolant being precisely warmed at each workstation.
BRIEF DESCRIPTION OF TEE DRAWINGS
FIG. 1 is a diagrammatic sketch of the temperature control apparatus.
FIG. 2 is a perspective view of one possible work station whose temperature
is being controlled.
FIG. 3 is a perspective view of a second possible work station whose
temperature is being controlled.
FIG. 4 is a perspective view of a third possible work station whose
temperature is being controlled.
FIG. 5 is a perspective view of a fourth possible work station whose
temperature is being controlled.
FIG. 6 is a graph of one possible time sequence for controlling a
workstation's temperature.
FIG. 7 is a graph of a second possible time sequence for controlling a
workstation's temperature.
DETAILED SPECIFICATION OF THE PREFERRED EMBODIMENTS
An embodiment of the invention is indicated in FIG. 1 by the numeral 10.
The invention comprises first a source of fluid coolant and a means for
maintaining the fluid coolant at a temperature below a predetermined
temperature at or around room temperature. The invention maintains the
fluid coolant temperature within a tolerance of .+-.0.5.degree. C.
The means for maintaining the fluid coolant below a predetermined
temperature comprises a cooling vehicle and associated controls. A cooling
vehicle 12, such as a heat exchanger, cools the fluid coolant to a
temperature below that desired for the workstation and work medium or
workpiece. A main coolant temperature sensor 14 detects the temperature of
the fluid coolant. Upon detecting the temperature of the fluid coolant,
the temperature sensor 14 provides an indication of this temperature to a
main coolant temperature control 16 by means of a sensor lead 18, such as
a wire or other means of transmission. Acting upon set point information
provided by the operator, the main coolant temperature control 16 signals
the cooling vehicle 12, by means of a control lead 20, which may be a wire
or other transmission medium, to remove enough heat from the fluid coolant
to establish and maintain the temperature of the fluid coolant at the
desired temperature, which is below that desired for the workstation and
work medium or workpiece. The main coolant temperature control 16 may be
in a programmed temperature control computer 22.
Coolant from the cooling vehicle 12 enters a source of fluid coolant, such
as a pipe or manifold 24. In this embodiment of the invention, the
temperature sensor 14 described above is within or attached to the
manifold 24, thus sensing the temperature of the fluid coolant at the
manifold 24.
Coolant from the cooling vehicle 12 and manifold 24 is circulated to and
through the workstation 28 by coolant circulating means comprising a flow
line 26, return line 32 and a recirculating pump 30.
Fluid coolant 25 from the manifold 24 enters the flow line 26. The flow
line 26 preferably contains a flow regulator 34 which maintains the
desired rate of flow of liquid coolant through the flow line 26. A
specific embodiment of such a flow regulator is a fixed orifice. The flow
line 26 also contains a heater 36 such as an electrical resistance heater
for regulating the temperature of the fluid coolant flowing to the
workstation 28, and continuously adding heat when called for, to the
continuously flowing coolant fluid.
Fluid coolant enters the workstation 28 from the flow line 26, passes
through the workstation 28, and exits the workstation 28 into the flow
line 26. Coolant then returns to the recirculating pump 30 and cooling
vehicle 12 by return line 32. Coolant from the manifold 24 also directly
returns to the recirculating pump 30 and cooling vehicle through return
line 32.
As the fluid coolant passes through the workstation 28, the fluid coolant
adjusts the temperature of the workstation 28 to the temperature of the
fluid coolant by heat transfer. Although the coolant in the flow line 26
is normally cooler than the workstation 28, coolant in the flow line 26
may also be at a higher temperature than that of the workstation 28. The
workstation 28 is closely associated with a work medium or workpiece 38
whose temperature is to be controlled, the temperature of the work medium
or workpiece thus approximating that of the workstation.
The workstation 28 has associated with it a workstation temperature sensor
40, in such a manner that the temperature sensor 40 detects the
temperature of the workstation 28. Upon detecting the temperature of the
workstation 28, the temperature sensor 40 provides an indication of this
temperature to a control means, workstation temperature control 42 by
means of a sensor lead 44, such as a wire or other transmission medium.
The set point temperature to be maintained at the workstation 28 is
provided to the workstation temperature control 42 by the operator. The
workstation temperature control 42 may be in a programmed temperature
control computer, thus providing a great deal of flexibility and precision
in regulating the temperature of the workstation. The workstation
temperature control 42 compares the temperature indication from the
workstation temperature sensor 40 to the desired temperature, and takes
appropriate action to adjust the workstation temperature to the desired
temperature.
To adjust the workstation temperature to the desired temperature, the
workstation temperature control 42 signals the heater 36 to provide more
or less heat by means of a control lead 46, which may be a wire or other
transmission medium. The heater heats only that portion of the coolant
flowing in flow line 26 to the workstation 28, rather than the entire
source of coolant. This provides for precise and rapid control of the
temperature of the workstation.
The flow line also contains a means, such as a valve 48, for bypassing both
the flow regulator 34 and the heater 36. When the bypass valve 48 is
opened, it will be seen that a flow of unwarmed coolant will be supplied
to the workstation 28 at an increased rate of flow, thus rapidly cooling
the workstation 28. The valve 48 is controlled by the workstation
temperature control 42 by means of a control lead 50, which may be a wire
or other transmission medium.
It will be appreciated by those skilled in the art that the sequence in
which the bypass valve 48 and heater 36 are operated will depend upon the
rapidity of the transient response required, and the initial temperature
differential between the temperature of the workstation 42 and the desired
temperature. At one extreme, an initial large temperature differential
such as 5.degree. C. might cause the workstation temperature control 42 to
open the bypass valve 48 initially. At the other extreme, an initially
small temperature differential such as 0.5.degree. to 1.0.degree. C. might
cause the temperature control 42 to keep the bypass valve 48 closed. As
the temperature control 42 may be embodied in a temperature control
computer, a large number of different operating sequences may be
programmed into the computer, and the appropriate sequence selected for
the particular situation presenting itself.
For example, FIG. 6 is a graph of workstation temperature versus time. The
workstation is to be cooled from an initial temperature T.sub.1, for
example 22.degree. C. to a desired temperature T.sub.2 perhaps 20.degree.
C. somewhat above the temperature of the fluid coolant T.sub.3, such as
19.degree. C. In this example the workstation temperature control 42 might
initially close the bypass valve 48, and turn off the heater 36. When the
workstation temperature falls to a predetermined value T.sub.4 the
workstation temperature control 42, as set by the operator, signals the
heater 36 to begin supplying heat to the flow line 26. The temperature of
the workstation 28 then decreases less rapidly as depicted by the graph
line L.sub.1, until the temperature of the workstation 28 reaches the
desired temperature T.sub.2, as depicted at point P.sub.1. The workstation
temperature control 42 then precisely modulates the heater 36 in order to
maintain the temperature of the workstation 28 at the desired temperature
T.sub.2.
FIG. 7 shows a second example. Here the workstation, starts out at a higher
temperature T.sub.1, perhaps 25.degree. C. The workstation temperature
control 42 opens the bypass valve 48 providing rapid cooling of the
workstation 28 as depicted by the chart line L.sub.1. As the workstation
temperature approaches desired temperature T.sub.2, perhaps 20.degree. C.,
somewhat above the temperature of the fluid coolant T.sub.3, such as
19.degree. C., the workstation temperature control 42 closes the bypass
valve 48, thus shutting off the high-rate flow of unheated coolant. The
workstation temperature control 42 then precisely modulates the heater 36
to maintain the temperature of the workstation 28 at temperature T.sub.2.
A plurality of workstations 28, 28.1, 28.2 may be regulated by the
invention through flow lines 26, 26.1, 26.2, heaters 36, 36.1, 36.2, flow
regulators 34, 34.1, 34.2, bypass valves 48, 48.1, 4.2, workstation
temperature sensors 40, 40.1, 40.2 and workstation temperature controls
42, 42.1, 42.2. Having one temperature control regulate a number of
workstations can result in cost savings. At the same time, replicating the
workstation temperature and flow controls allows each workstation to be
independently controlled to an independent predetermined temperature, if
so desired.
A first embodiment of a workstation is shown in FIG. 2, where the
workstation 28 comprises a chill plate through which the fluid coolant is
circulated from the flow line 26. The chill plate has an upper surface
29.1 upon which the workpiece 38 rests. In this embodiment the workpiece
may be a semiconductor wafer whose temperature is to be controlled.
A second embodiment of a workstation is shown in FIG. 3, where the
workstation 28 comprises a cylindrical collar with an interior cylindrical
passage 29.2 through which the work medium 38.1 extends. In this
embodiment, the work medium 38.1 may be the shaft 39 of an electric motor
52. The fluid coolant circulates from the flow line 26 in and out of the
workstation 28. The workstation 28 thereby regulates the temperature of
the shaft 39, thus preventing heat from the motor 52 from reaching the
workpiece 54, which can be a wafer supported on a rotating chuck 56 on the
end of the shaft 39.
A third embodiment of a workstation is shown in FIG. 4, where the
workstation 28 comprises a liquid-to-liquid heat exchanger with an
interior pipe 29.3 through which a liquid work medium to be cooled 38.2 is
flowing. The fluid coolant circulates from the flow line 26 in and out of
the workstation 28, thereby regulating the temperature of the liquid work
medium 38.2.
A fourth embodiment of a workstation is shown in FIG. 5, where the
workstation 28 comprises a module with an upper compartment 29.4 and lower
compartment 29.5 separated by a cooling plate 29.6. The fluid coolant
circulates from the flow line 26 in and out of the cooling plate 29.6,
thereby preventing thermal interactions between processes in the upper
compartment 29.4 and the lower compartment 29.5.
It will be seen that a temperature control with recirculated coolant and a
rapid transient response has been described. A process for precisely
cooling a work medium to a predetermined temperature has also been
described.
The present invention may be embodied in other specific forms without
departing from the spirit or essential attributes thereof; therefore, the
illustrated embodiment should be considered in all respects as
illustrative and not restrictive, reference being made to the appended
claims rather than to the foregoing description to indicate the scope of
the invention.
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