U.S. patent application number 10/820157 was filed with the patent office on 2004-12-23 for baking system having a heat pipe.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Kim, Sang-kap, Kim, Tae-gyu, Lee, Dong-woo, Lee, Jin-sung, Shin, Dong-hwa.
Application Number | 20040256094 10/820157 |
Document ID | / |
Family ID | 33475964 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040256094 |
Kind Code |
A1 |
Lee, Dong-woo ; et
al. |
December 23, 2004 |
Baking system having a heat pipe
Abstract
A baking system includes a heat pipe including a top surface for
receiving a wafer to be baked, the heat pipe to be filled with a
predetermined amount of working fluid and having wicks formed on
sides and a ceiling thereof for supplying the working fluid, a
heater for heating the top surface by heating the working fluid, a
subsidiary cooling system, which contains a liquid coolant that is
to be exchanged with the working fluid from the heat pipe through
circulation, a connection pipe for providing fluid communication
between the heat pipe and the subsidiary cooling system to
circulate the working fluid and the liquid coolant, and a control
unit, which is installed in the connection pipe, for controlling a
flow of the working fluid and the liquid coolant through the
connection pipe.
Inventors: |
Lee, Dong-woo; (Seoul,
KR) ; Lee, Jin-sung; (Seoul, KR) ; Kim,
Sang-kap; (Osan-si, KR) ; Shin, Dong-hwa;
(Yongin-si, KR) ; Kim, Tae-gyu; (Hwaseong-gun,
KR) |
Correspondence
Address: |
LEE & STERBA, P.C.
SUITE 2000
1101 WILSON BOULEVARD
ARLINGTON
VA
22209
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
|
Family ID: |
33475964 |
Appl. No.: |
10/820157 |
Filed: |
April 8, 2004 |
Current U.S.
Class: |
165/299 |
Current CPC
Class: |
F28D 15/0266 20130101;
F28D 15/046 20130101; F28D 15/06 20130101; H01L 21/67109
20130101 |
Class at
Publication: |
165/299 |
International
Class: |
F28F 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2003 |
KR |
2003-21920 |
Claims
What is claimed is:
1. A baking system, comprising: a heat pipe including a top surface
for receiving a wafer to be baked, the heat pipe to be filled with
a predetermined amount of working fluid and having wicks formed on
sides and a ceiling thereof for supplying the working fluid; a
heater for heating the top surface by heating the working fluid; a
subsidiary cooling system, which contains a liquid coolant that is
to be exchanged with the working fluid from the heat pipe through
circulation; a connection pipe for providing fluid communication
between the heat pipe and the subsidiary cooling system to
circulate the working fluid and the liquid coolant; and a control
unit, which is installed in the connection pipe, for controlling a
flow of the working fluid and the liquid coolant through the
connection pipe.
2. The system as claimed in claim 1, wherein the connection pipe
comprises an inlet flow path and an outlet flow path for providing
fluid communication between the heat pipe and the subsidiary
cooling system.
3. The system as claimed in claim 1, wherein the connection pipe
comprises: an outlet connection pipe for providing fluid
communication from the heat pipe to the subsidiary cooling system;
and an inlet connection pipe for providing fluid communication from
the subsidiary cooling system to the heat pipe.
4. The system as claimed in claim 3, wherein the control unit
comprises: an outlet fluid control unit installed in the outlet
connection pipe; and an inlet fluid control unit installed in the
inlet connection pipe.
5. The system as claimed in claim 4, wherein the outlet fluid
control unit is selected from the group consisting of an automated
pump and a valve and the inlet fluid control unit is selected from
the group consisting of a valve, an automatic pump, and a manual
pump.
6. The system as claimed in claim 3, wherein the control unit
comprises: a first outlet fluid control unit and a second outlet
fluid control unit sequentially installed in the outlet connection
pipe; and an inlet fluid control unit installed in the inlet
connection pipe.
7. The system as claimed in claim 6, wherein the first outlet fluid
control unit is selected from the group consisting of an automatic
valve and a manual valve, the inlet fluid control unit is selected
from the group consisting of an automatic valve, a manual valve,
and a pump, and the second outlet fluid control unit is a pump.
8. The system as claimed in claim 2, wherein the subsidiary cooling
system comprises: a coolant storage tank for storing the liquid
coolant, the coolant storage tank having a wick formed therein; a
cooling unit installed at the coolant storage tank for cooling the
working fluid supplied from the heat pipe; and a pressurizing unit
for pressurizing the liquid coolant during a process of cooling the
top surface.
9. The system as claimed in claim 3, wherein the subsidiary cooling
system comprises: a first coolant storage tank for storing the
liquid coolant; and a first cooling system installed at the first
coolant storage tank for cooling the working fluid supplied from
the heat pipe.
10. The system as claimed in claim 1, wherein the control unit is
selected from the group consisting of a pump and a valve.
11. The system as claimed in claim 9, further comprising a second
coolant storage tank in fluid communication with the first coolant
storage tank, wherein the first cooling system extends to the
second coolant storage tank.
12. The system as claimed in claim 9, further comprising: a second
coolant storage tank in fluid communication with the first coolant
storage tank; and a second cooling system installed at the second
coolant storage tank.
13. The system as claimed in claim 11, further comprising: an
intermediate connection pipe for providing fluid communication
between the first coolant storage tank and the second coolant
storage tank; and an intermediate fluid control unit installed in
the intermediate connection pipe.
14. The system as claimed in claim 1, further comprising a
subsidiary heater installed in the connection pipe between an inlet
of the heat pipe and the subsidiary cooling system to heat a fluid
flowing through the connection pipe.
15. The system as claimed in claim 9, further comprising a
subsidiary heater installed at the first coolant storage tank to
heat a fluid supplied into the heat pipe.
16. The system as claimed in claim 9, wherein the working fluid is
selected from the group consisting of water, deionized water,
acetone, and methyl.
17. A baking system, comprising: a heat pipe including a top
surface for receiving a wafer to be baked and an inlet side and an
outlet side, the heat pipe to be filled with a predetermined amount
of working fluid and having wicks formed on sides and a ceiling
thereof for supplying the working fluid; a heater for heating the
top surface of the heat pipe by heating the working fluid; a
connection pipe, a first end of which is connected to the outlet
side of the heat pipe, and a second end of which is connected to
the inlet side of the heat pipe; a cooling unit installed in the
connection pipe for cooling the working fluid flowing through the
connection pipe; and a control unit for controlling the working
fluid.
18. The system as claimed in claim 17, wherein the cooling unit is
installed to wrap around a portion of the connection pipe.
19. The system as claimed in claim 17, wherein the control unit
comprises an outlet fluid control unit installed in the connection
pipe between the outlet side of the heat pipe and the cooling unit
and an inlet fluid control unit installed in the connection pipe
between the inlet side of the heat pipe and the cooling unit.
20. The system as claimed in claim 19, wherein the outlet fluid
control unit and the inlet fluid control unit are selected from the
group consisting of an automatic valve, a manual valve, and a pump.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a baking system for use in
a process of manufacturing semiconductor devices. More
particularly, the present invention relates to a baking system
having a heat pipe as a cooling unit.
[0003] 2. Description of the Related Art
[0004] A photolithographic process, which is one type of process
performed during the manufacture of a semiconductor device,
includes a coating process of coating a photoresist layer on a
wafer, a pre-baking process of baking the coated photoresist layer
before exposure, and a post-exposure baking process of baking the
photoresist layer after exposure, to form a predetermined pattern
in the photoresist layer.
[0005] In a photolithographic process, a baking temperature varies
according to a type of photoresist layer and a type of baking
process. For example, the baking process may be performed at a
temperature of 150.degree. C. or 90.degree. C. depending on
particular circumstances. Accordingly, a widely used baking
apparatus includes a heating system and a cooling system to adjust
the baking temperature according to the particular
circumstances.
[0006] FIGS. 1 through 3 illustrate sectional views of cooling
systems of conventional baking apparatuses (hereinafter, referred
to as "conventional cooling systems").
[0007] In a first conventional cooling system, as shown in FIG. 1,
coolant paths 56 and 57, through which a coolant flows, are
installed in a plate 54. Coolant circulates through the coolant
paths 56 and 57 and cools a heating plate 51. The first
conventional cooling system additionally includes a heater 52, a
lift pin 53, and a cooling plate 55. Coolant supply pipelines 60
and 61 include switching valves 62 and 63, respectively, and
terminate at a drain 64. The first conventional cooling system
further includes a temperature sensor 65, a unit controller 66, a
temperature adjuster 67, a solenoid valve 68, and a power supply
69. A system controller 80 controls operations of the entire
system.
[0008] In a second conventional cooling system, as shown in FIG. 2,
a plurality of nozzles 74 is installed under a heating plate 70
that acts as a baking plate. A spray of a fluid from the nozzles 74
onto the heating plate 70 is used to cool the heating plate 70. The
second conventional cooling system further includes a heater 71, a
guide 83, an inner case 85, a support ring 87, a cooling plate 93,
and a black plate 96.
[0009] A third conventional cooling system 30, as shown in FIG. 3,
includes a cooling plate 99 in which a Peltier device 101 is
embedded. The Peltier device 101 adjusts a temperature of the
cooling plate 99 to a predetermined temperature. The third
conventional cooling system 30 further includes a power controller
102 for supplying power to the Peltier device 101, a temperature
adjuster 103 for adjusting the temperature of the Peltier device
101, and a proportional integral derivative (PID) control parameter
altering unit 105. In addition, the cooling system 30 includes a
flow path 111 used for radiating heat generated in the Peltier
device 101, a lifting pin 90 for lifting a wafer W, a penetration
pin 91, and a proximity pin 92 for supporting the wafer W. A
temperature sensor 104 senses a temperature of the cooling plate
99.
[0010] In the above-described conventional cooling systems a
temperature deviation between different regions of a baking plate
is very large. More specifically, the entire baking plate cannot be
uniformly cooled. In addition, a significant amount of time is
required until a temperature is uniformly distributed after a
cooling process starts. These disadvantages degrade semiconductor
device manufacturing productivity.
[0011] As these problems of the conventional cooling systems have
been highlighted, various alternatives have been proposed. One such
alternative requires a plurality of baking plates, set to different
temperatures, to be installed in a cooling system. In this case,
however, although a cooling time may be reduced, a single spinner
is required to include the plurality of baking plates and thus
becomes undesirably large.
SUMMARY OF THE INVENTION
[0012] In an effort to overcome at least some of the
above-described disadvantages, the present invention provides a
baking system that is able to uniformly cool an entire top surface
of a hot plate and effectively reduce a cooling time.
[0013] In accordance with a feature of an embodiment of the present
invention, there is provided a baking system including a heat pipe
including a top surface for receiving a wafer to be baked, the heat
pipe to be filled with a predetermined amount of working fluid and
having wicks formed on sides and a ceiling thereof for supplying
the working fluid, a heater for heating the top surface by heating
the working fluid, a subsidiary cooling system, which contains a
liquid coolant that is to be exchanged with the working fluid from
the heat pipe through circulation, a connection pipe for providing
fluid communication between the heat pipe and the subsidiary
cooling system to circulate the working fluid and the liquid
coolant, and a control unit, which is installed in the connection
pipe, for controlling a flow of the working fluid and the liquid
coolant through the connection pipe.
[0014] The connection pipe may include an inlet flow path and an
outlet flow path for providing fluid communication between the heat
pipe and the subsidiary cooling system. The connection pipe may
include an outlet connection pipe for providing fluid communication
from the heat pipe to the subsidiary cooling system and an inlet
connection pipe for providing fluid communication from the
subsidiary cooling system to the heat pipe.
[0015] The control unit may include an outlet fluid control unit
installed in the outlet connection pipe and an inlet fluid control
unit installed in the inlet connection pipe. The outlet fluid
control unit may be an automated pump or a valve and the inlet
fluid control unit may be a valve, an automatic pump, or a manual
pump.
[0016] The control unit may include a first outlet fluid control
unit and a second outlet fluid control unit sequentially installed
in the outlet connection pipe and an inlet fluid control unit
installed in the inlet connection pipe. The first outlet fluid
control unit may be an automatic valve or a manual valve, the inlet
fluid control unit may be an automatic valve, a manual valve, or a
pump, and the second outlet fluid control unit may be a pump.
[0017] The subsidiary cooling system may include a coolant storage
tank for storing the liquid coolant, the coolant storage tank
having a wick formed therein, a cooling unit installed at the
coolant storage tank for cooling the working fluid supplied from
the heat pipe, and a pressurizing unit for pressurizing the liquid
coolant during a process of cooling the top surface.
[0018] The subsidiary cooling system may include a first coolant
storage tank for storing the liquid coolant and a first cooling
system installed at the first coolant storage tank for cooling the
working fluid supplied from the heat pipe. Further, there may be
included a second coolant storage tank in fluid communication with
the first coolant storage tank, wherein the first cooling system
extends to the second coolant storage tank. Alternatively, there
may be included a second coolant storage tank in fluid
communication with the first coolant storage tank and a second
cooling system installed at the second coolant storage tank.
Further, there may be included an intermediate connection pipe for
providing fluid communication between the first coolant storage
tank and the second coolant storage tank and an intermediate fluid
control unit installed in the intermediate connection pipe. The
control unit may be a pump or a valve.
[0019] The baking system may further include a subsidiary heater
installed in the connection pipe between an inlet of the heat pipe
and the subsidiary cooling system to heat a fluid flowing through
the connection pipe.
[0020] Alternatively, the baking system may further include a
subsidiary heater installed at the first coolant storage tank to
heat a fluid supplied into the heat pipe.
[0021] The working fluid may be water, deionized water, acetone, or
methyl.
[0022] In accordance with a feature of another embodiment of the
present invention, there is provided a baking system including a
heat pipe including a top surface for receiving a wafer to be baked
and an inlet side and an outlet side, the heat pipe to be filled
with a predetermined amount of working fluid and having wicks
formed on sides and a ceiling thereof for supplying the working
fluid, a heater for heating the top surface of the heat pipe by
heating the working fluid, a connection pipe, a first end of which
is connected to the outlet side of the heat pipe, and a second end
of which is connected to the inlet side of the heat pipe, a cooling
unit installed in the connection pipe for cooling the working fluid
flowing through the connection pipe, and a control unit for
controlling the working fluid.
[0023] The cooling unit may be installed to wrap around a portion
of the connection pipe. The control unit may include an outlet
fluid control unit installed in the connection pipe between the
outlet side of the heat pipe and the cooling unit and an inlet
fluid control unit installed in the connection pipe between the
inlet side of the heat pipe and the cooling unit. The outlet fluid
control unit and the inlet fluid control unit may be an automatic
valve, a manual valve, or a pump.
[0024] A baking system according to an embodiment of the present
invention is able to uniformly cool an entire region of a hot plate
in a relatively short amount of time to stabilize the temperature
of the hot plate. Further, a time required to heat the hot plate
may be decreased using a subsidiary heater, thus improving
semiconductor device manufacturing productivity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other features and advantages of the present
invention will become more apparent to those of ordinary skill in
the art by describing in detail illustrative embodiments thereof
with reference to the attached drawings in which:
[0026] FIGS. 1 through 3 illustrate sectional views of a first
through a third conventional cooling system, respectively;
[0027] FIGS. 4 through 9 illustrate partial sectional views of
baking systems according to a first through a sixth embodiment of
the present invention, respectively;
[0028] FIG. 10 is a graph of simulation results showing a cooling
efficiency of a conventional baking system using natural
cooling;
[0029] FIGS. 11 through 13 are graphs of simulation results showing
a cooling efficiency of a conventional baking system, in which a
cooling line is buried in a hot plate;
[0030] FIG. 14 is a graph of simulation results showing a cooling
efficiency of a conventional baking system, in which a cooling line
is installed under a heater;
[0031] FIGS. 15 and 16 illustrate a partial front view and a plan
view, respectively, of the conventional baking system with the
cooling line buried in the hot plate;
[0032] FIG. 17 illustrates a partial front view of the conventional
baking system with the cooling line installed under the heater;
and
[0033] FIGS. 18 through 20 are graphs of simulation results showing
a cooling efficiency of the baking systems according to the
embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] Korean Patent Application No. 2003-21920, filed on Apr. 8,
2003, and entitled: "Baking System," is incorporated by reference
herein in its entirety.
[0035] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown. The invention
may, however, be embodied in different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. In the figures, the
dimensions of layers and regions are exaggerated for clarity of
illustration. Like reference numerals refer to like elements
throughout. In the context of the present invention, a term
"working fluid" describes a fluid in a heat pipe that operates
either to heat or to cool a top surface of the heat pipe. A term
"liquid coolant" describes a fluid in a coolant storage tank that
circulates to replace the working fluid in the heat pipe and
operates to cool the top surface of the heat pipe.
[0036] First Embodiment
[0037] As shown in FIG. 4, a baking system according to a first
embodiment includes a main body P1 and a subsidiary cooling system
P2. The main body P1 includes a heat pipe 100 and a heater 102
contacting a bottom of the heat pipe 100. The subsidiary cooling
system P2 includes a coolant storage tank 106, which is partially
filled with a liquid coolant 104b, a cooling unit 110 for cooling
the liquid coolant 104b, and a pressurizing unit 109 for forcibly
circulating the liquid coolant 104b through the heat pipe 100.
[0038] Wicks W1 and W2 are formed on inner sides of and on a center
of the ceiling of the heat pipe 100, respectively. In the context
of the present invention, the term wicks may also include wick
plates WP1 and WP2, as shown in FIG. 4. Wicks similar to the wicks
W1 and W2 may be formed on an inside of the coolant storage tank
106. More specifically, the wicks may be formed on inner sides of
and a ceiling of the coolant storage tank 106 so that a
high-temperature working fluid, which flows into the coolant
storage tank 106, can move along the sides of the coolant storage
tank 106 to the ceiling thereof due to the capillarity attraction
of the wicks and evaporate. In this process, the high-temperature
working fluid flowing into the coolant storage tank 106 is cooled.
More specifically, the subsidiary cooling system P2 includes the
coolant storage tank 106 functioning as a heat pipe. The
pressurizing unit 109 heats the vapor above the liquid coolant 104b
contained in the coolant storage tank 106 and pressurizes the
liquid coolant. Preferably, the pressurizing unit 109 does not
cause physical transformation of the coolant storage tank 106.
[0039] When a baking process is performed, as shown in FIG. 4, a
wafer W is loaded on a top surface S1 of the heat pipe 100, and the
top surface S1 of the heat pipe 100, i.e., a hot plate surface, is
heated to a predetermined temperature, e.g., 100.degree. C. to
150.degree. C. After the baking process is finished and the wafer W
is removed from the top surface S1, the heat pipe 100 cools the top
surface S1, which was heated in the baking process, to a
predetermined temperature.
[0040] In order to cool the top surface S1, the heat pipe 100 is
filled with a predetermined amount of working fluid 104a.
[0041] During a baking process, the working fluid 104a transmits
heat from the heater 102 to the top surface S1 of the heat pipe 100
to heat the top surface S1. More specifically, the heat transmitted
from the heater 102 causes the working fluid 104a to evaporate into
an upper space 112 and contact the ceiling of the heat pipe 100,
thus heating the top surface S1 of the heat pipe 100.
[0042] During a cooling process, the working fluid 104a is supplied
along the wicks W1 and W2 to the ceiling of the heat pipe 100 and
evaporates, thereby cooling the hot plate surface, i.e., the top
surface S1 of the heat pipe 100. Since the wicks W1 are uniformly
formed on the entire ceiling of the heat pipe 100, the working
fluid 104a is uniformly supplied to the entire ceiling of the heat
pipe 100. In addition, the working fluid 104a is affected by the
capillarity attraction of the wicks W1 and W2 and is rapidly
supplied to the entire ceiling of the heat pipe 100 during the
cooling process. Thus, the entire top surface S1 of the heat pipe
100 is cooled in a relatively short amount of time. The vapor,
generated in the cooling process, passes through the upper space
112 and contacts the working fluid 104a, whose temperature is lower
than that of the vapor. Thus, the vapor condenses again into the
working fluid 104a.
[0043] The working fluid 104a may be water, i.e., deionized water,
acetone, methyl or any suitable liquid.
[0044] While the top surface of the heat pipe 100 is being cooled,
if the working fluid 104a is replaced by another fluid, whose
temperature is lower than that of the working fluid 104a, the
cooling efficiency of the heat pipe 100 will improve. For this
purpose, the liquid coolant 104b contained in the coolant storage
tank 106 of the subsidiary cooling system P2 is prepared. The
liquid coolant 104b is preferably maintained at a temperature lower
than that of the working fluid 104a.
[0045] While the top surface S1 of the heat pipe 100 is being
cooled, to improve the cooling efficiency of the heat pipe 100,
fluid circulates between the subsidiary cooling system P2 and the
heat pipe 100 until the top surface S1 is cooled to a desired
temperature.
[0046] Specifically, an outlet flow path L1 and an inlet flow path
L2 are installed between the heat pipe 100 and the subsidiary
cooling system P2 to provide fluid communication between the heat
pipe 100 and the subsidiary cooling system P2. A valve 108 for
controlling the flow of fluid is installed in the outlet and inlet
flow paths L1 and L2 such that the fluid circulates only during the
cooling process. Alternatively, the valve 108 may be a pump.
[0047] When the cooling process of the top surface S1 of the heat
pipe 100 starts, the valve 108 is opened and simultaneously, the
pressurizing unit 109, such as a Peltier device, of the subsidiary
cooling system P2, pressurizes the liquid coolant 104b. As a
result, some of the liquid coolant 104b is supplied via the inlet
flow path L2 to the heat pipe 100, and the working fluid 104a of
the heat pipe 100 is supplied via the outlet flow path L1 to the
coolant storage tank 106. This fluid circulation is conducted
continuously or periodically until the top surface S1 of the heat
pipe 100 is cooled to a predetermined temperature, e.g.,
100.degree. C. During the fluid circulation, the heated working
fluid 104a of the heat pipe 100 flows into the coolant storage tank
106 of the subsidiary cooling system P2 and raises the temperature
of the liquid coolant 104b stored in the coolant storage tank 106.
However, the cooling unit 110, installed under the coolant storage
tank 106, maintains the liquid coolant 104b at a constant
temperature.
[0048] Second Embodiment
[0049] Referring to FIG. 5, a baking system according to a second
embodiment includes a coolant storage tank 120 in fluid
communication with the heat pipe 100. An outlet of the heat pipe
100 is connected to a side, e.g., a top of the coolant storage tank
120 by an outlet connection pipe 126. An inlet of the heat pipe 100
is connected to another side of the coolant storage tank 120 by an
inlet connection pipe 128. During a cooling process, the working
fluid 104a flows from the heat pipe 100 to the coolant storage tank
120 via the outlet connection pipe 126. The working fluid 104a,
which flows into the coolant storage tank 120, is cooled to a
predetermined temperature, e.g., 23.degree. C., and is then
returned to the heat pipe 100 via the inlet connection pipe
128.
[0050] The fluid circulation between the heat pipe 100 and the
coolant storage tank 120 may be interrupted during a baking process
and restarted during a process of cooling the top surface S1 of the
heat pipe 100. To perform this interruption, an outlet fluid
control unit 126a and an inlet fluid control unit 128a are
installed in the outlet connection pipe 126 and the inlet
connection pipe 128, respectively. The outlet fluid control unit
126a may be an automated pump or a valve. The inlet fluid control
unit 128a may be a valve, an automatic pump or a manual pump.
[0051] In operation, while fluids, i.e., the working fluid and the
liquid coolant, are circulating between the heat pipe 100 and the
coolant storage tank 120, a level of the working fluid 104a in the
heat pipe 100 may rise over time but is preferably maintained as
constant as possible. Accordingly, the flow rate of the working
fluid 104a flowing from the heat pipe 100 is preferably equal to
that of the liquid coolant (not shown) flowing into the heat pipe
100. To maintain a constant flow rate, in a case where a diameter
of the outlet connection pipe 126 is equal to that of the inlet
connection pipe 128, a control function of the outlet fluid control
unit 126a is preferably equal to that of the inlet fluid control
unit 128a. Alternatively, when a diameter of the outlet connection
pipe 126 differs from that of the inlet connection pipe 128, a
control function of the outlet fluid control unit 126a may be
adjusted to differ from that of the inlet fluid control unit 128a
such that the flow rate of the working fluid 104a from the heat
pipe 100 is equal to that of the liquid coolant flowing into the
heat pipe 100.
[0052] In addition, the working fluid 104a flowing from the heat
pipe 100 into the coolant storage tank 120 via the outlet
connection pipe 126 has a relatively high temperature, whereas the
liquid coolant supplied from the coolant storage tank 120 to the
heat pipe 100 via the inlet connection pipe 128 preferably has a
relatively lower predetermined temperature, e.g., 23.degree. C.
Thus, the working fluid 104a supplied to the coolant storage tank
120 is preferably cooled to the predetermined temperature of
23.degree. C. A cooling unit 124 is installed at the coolant
storage tank 120 to cool the working fluid 104a. The cooling unit
124 may be provided on a top of the coolant storage tank 120, as
shown, or may be installed under the coolant storage tank 120 as
illustrated by reference numeral 124'.
[0053] In a case where the cooling unit 124 includes an evaporation
unit (not shown) and a condensation unit (not shown), the
evaporation unit may be installed on a top, a bottom and/or a side
of the coolant storage tank 120, and the condensation unit may be
installed in a region spaced apart from the evaporation unit.
[0054] Third Embodiment
[0055] Referring to FIG. 6, in a baking system according to a third
embodiment of the present invention, a connection pipe 130 is
installed outside the heat pipe 100 to circulate the working fluid
104a in the heat pipe 100 during the cooling of the top surface S1,
i.e., the hot plate surface. An inlet of the connection pipe 130 is
connected to the outlet of the heat pipe 100 and an outlet of the
connection pipe 130 is connected to the inlet of the heat pipe 100.
A cooling unit 132 is installed at a predetermined position along
the connection pipe 130 so as to wrap around a portion of the
connection pipe 130. The cooling unit 132 of the third embodiment
performs the same function as the cooling unit 124 of the second
embodiment. In particular, the cooling unit 132 cools the working
fluid 104a flowing from the heat pipe 100 through the connection
pipe 130 to a predetermined temperature. The outlet fluid control
unit 126a, as described in connection with the second embodiment,
is installed in the connection pipe 130 between the outlet of the
heat pipe 100 and the cooling unit 132. In addition, the inlet
fluid control unit 128a is installed in the connection pipe 130
between the inlet of the heat pipe 100 and the cooling unit
132.
[0056] Fourth Embodiment
[0057] Referring to FIG. 7, in a baking system according to a
fourth embodiment of the present invention, a first coolant storage
tank 134 and a second coolant storage tank 136 are installed
outside the heat pipe 100. The first coolant storage tank 134 and
the second coolant storage tank 136 store the high-temperature
working fluid 104a supplied from the heat pipe 100 during a cooling
process of the hot plate and cool the working fluid 104a to a
predetermined temperature. To perform this cooling operation, a
first cooling unit 144 and a second cooling unit 146 are installed
at the first coolant storage tank 134 and the second coolant
storage tank 136, respectively.
[0058] When a cooling process of the hot plate begins, the working
fluid 104a flows from the heat pipe 100 and simultaneously, the
liquid coolant (not shown) is supplied to the heat pipe 100,
preferably at a flow rate equal to that of the working fluid 104a.
Therefore, a predetermined amount of liquid coolant may be
maintained at a predetermined temperature, e.g., 2.degree. C. to
3.degree. C., and stored in the first coolant storage tank 134 and
the second coolant storage tank 136. In particular, the liquid
coolant is stored in the second coolant storage tank 136, which is
closer to the inlet side of the heat pipe 100.
[0059] The first cooling unit 144 and the second cooling unit 146
of the fourth embodiment perform the same function as the cooling
unit of the second embodiment (124 of FIG. 5). The first cooling
unit 144 and the second cooling unit 146 may be integrated into a
single cooling unit as illustrated by reference numeral 148. Given
the positions of the first coolant storage tank 134 and the second
coolant storage tank 136, a liquid coolant flowing into the second
coolant tank 136 necessarily flows through the first coolant
storage tank 134. Accordingly, the liquid coolant flowing into the
second coolant storage tank 136 has a lower temperature than the
working fluid 104a flowing into the first coolant storage tank 134.
For this reason, the first cooling unit 144 may have a same or
higher cooling efficiency than the second cooling unit 146.
[0060] The outlet of the heat pipe 100 is connected to the first
coolant storage tank 134 by an outlet connection pipe 138, the
first coolant storage tank 134 is connected to the second coolant
storage tank 136 by an intermediate connection pipe 140, and the
inlet of the heat pipe 100 is connected to the second coolant
storage tank 136 by an inlet connection pipe 142. An outlet fluid
control unit 126a is installed in the outlet connection pipe 138.
An inlet fluid control unit 128a is installed in the inlet
connection pipe 142. Like the outlet and/or inlet fluid control
units 126a and 128a, an intermediate fluid control unit 140a may be
an automatic valve, a manual valve, an automatic pump, or a manual
pump. The outlet, inlet, and intermediate fluid control units 126a,
128a, and 140a are opened when cooling of the hot plate starts and
are closed when the cooling of the hot plate is finished or when
the hot plate is heated again to bake a new wafer.
[0061] In operation, a cooling process of the hot plate occurs as
follows. When cooling of the hot plate starts, all of the fluid
control units 126a, 128a, and 140a are opened, and a hot working
fluid 104a flows from the heat pipe 100 into the first coolant
storage tank 134 via the outlet connection pipe 138. The first
cooling unit 144 cools the hot working fluid 104a supplied to the
first coolant storage tank 134. The working fluid 104a then flows
through the intermediate connection pipe 140 into the second
coolant storage tank 136. A liquid coolant supplied to the second
coolant storage tank 136 is cooled to a desired temperature by the
second cooling unit 146 and then flows into the heat pipe 100 via
the inlet connection pipe 142.
[0062] Fluid circulation may be continuously conducted until
cooling of the hot plate is completed or may be repeated several
times for a predetermined time duration, e.g., 15 seconds, each
time. The liquid coolant flowing from the second coolant storage
tank 136 into the heat pipe 100 may be maintained at any
temperature lower than that of the hot working fluid 104a in the
heat pipe 100. However, the temperature of the liquid coolant is
preferably lower than about 80.degree. C. This aspect of the
process will be subsequently described in greater detail.
[0063] As described above, while passing through the first and
second coolant storage tanks 134 and 136, the hot working fluid
104a is cooled to a previous temperature thereof in the heat pipe
100 before the hot plate was heated. The first coolant storage tank
134 and/or the second coolant storage tank 136 may be used to cool
the hot working fluid 104a. More specifically, the hot working
fluid 104a may be gradually cooled while passing through both the
first and second coolant storage tanks 134 and 136. Alternatively,
the hot working fluid 104a may be cooled to a desired temperature
using only one of the first and second coolant storage tanks 134
and 136.
[0064] Fifth Embodiment
[0065] As shown in FIG. 8, a baking system according to a fifth
embodiment of the present invention is similar to that of the
fourth embodiment except that the first coolant storage tank 134
and the second cooling unit 144 are removed from the subsidiary
cooling system of the baking system in the fifth embodiment.
[0066] In FIG. 8, a coolant storage tank 150 and a cooling system
156 installed at the coolant storage tank 150 correspond to the
second coolant storage tank 136 and second cooling system 146 of
the fourth embodiment. The coolant storage tank 150 is connected to
the outlet side of a heat pipe 100 by an outlet connection pipe 152
and to the inlet side of the heat pipe 100 by an inlet connection
pipe 154. A first outlet fluid control unit 152a and a second
outlet fluid control unit 152b are sequentially installed in the
outlet connection pipe 152, through which a hot working fluid 104a
flows from the heat pipe 100 into the coolant storage tank 150. An
inlet fluid control unit 154a is installed in the inlet connection
pipe 154, through which a cooled liquid coolant flows from the
coolant storage tank 150 into the heat pipe 100. The first outlet
fluid control unit 152a and the inlet fluid control unit 154a may
be automatic valves or manual valves, and the second outlet fluid
control unit 152b may be a pump. Alternatively, the inlet fluid
control unit 154a may be a pump.
[0067] Sixth Embodiment
[0068] Referring to FIG. 9, in a baking system according to a sixth
embodiment of the present invention, a coolant storage tank 160 is
installed outside the heat pipe 100. The coolant storage tank 160
is connected to the outlet side of the heat pipe 100 by an outlet
connection pipe 162 and to the inlet side of the heat pipe 100 by
an inlet connection pipe 164. The hot working fluid 104a flows from
the heat pipe 100 into the coolant storage tank 160 via the outlet
connection pipe 162. The hot working fluid 104a is cooled while
passing through the coolant storage tank 160. The cooled working
fluid 104a is then returned to the heat pipe 100 via the inlet
connection pipe 164. An outlet fluid control unit 162a is installed
in the outlet connection pipe 162. An inlet fluid control unit 164a
is installed in the inlet connection pipe 164. The outlet fluid
control unit 162a and the inlet fluid control unit 164a may be
automatic valves, manual valves, or pumps. A cooling system 160b is
installed under the coolant storage tank 160 and a subsidiary
heater 160a is mounted on the coolant storage tank 160. The cooling
system 160b performs the same function as the foregoing cooling
systems. Alternatively, the subsidiary heater may be installed in
the inlet connection pipe 164 between an inlet of the heat pipe 100
and the subsidiary cooling system 160 to heat a fluid flowing
through the inlet connection pipe 164.
[0069] The subsidiary heater 160a is used to heat the top surface
S1 of the heat pipe 100, i.e., the hot plate surface, along with
the heater 102 installed under the heat pipe 100. In operation,
when a heating process of the top surface S1 of the heat pipe 100
starts, unlike in the previous embodiments, the outlet fluid
control unit 162a and the inlet fluid control unit 164a remain open
in the same manner as when the top surface S1 is cooled.
Accordingly, the heater 102 heats some of the working fluid 104a in
the heat pipe 100, and the subsidiary heater 160a heats the working
fluid 104a in the coolant storage tank 160. The subsidiary heater
160a facilitates heating of the top surface S1 of the heat pipe 100
and reduces a time necessary to heat the top surface S1.
[0070] Hereinafter, simulation results showing a cooling efficiency
of baking systems of the present invention will be described.
[0071] In the simulation, the baking system shown in FIG. 4 as used
as a simulation model and the conventional baking system shown in
FIGS. 15 through 17 was used as a contrastive example (hereinafter,
referred to as the "contrastive baking system"). In the simulation,
a top surface of a heat pipe, i.e., a hot plate, included in the
baking system of the present invention, and a hot plate of the
contrastive baking system were heated to a temperature of
150.degree. C. and then cooled to a temperature of 100.degree.
C.
[0072] FIGS. 15 and 16 illustrate a partial front view and a plan
view, respectively, of a hot plate 200 of the contrastive baking
system, in which a first cooling line 206 and a second cooling line
208 for supplying liquid coolant, such as water, are buried. FIG.
15 illustrates a left half of the hot plate 200, wherein the first
cooling line 206 is buried. FIG. 16 illustrates a plan view of the
entire hot plate, in which the first cooling line 206 and the
second cooling line 208 are buried.
[0073] In FIG. 15, reference numerals 202 and 204 are a heater and
a lower plate, respectively. In addition, reference character Lc
denotes a central line that bisects the hot plate 200 shown in FIG.
16.
[0074] FIG. 17 illustrates a partial front view of the contrastive
baking system, in which cooling lines 210 for supplying cooling
water are buried only in a lower plate 204 under a heater.
[0075] FIGS. 10 through 14 are graphs showing simulation results of
the contrastive baking system. FIGS. 18 through 20 are graphs
showing simulation results of the baking system according to the
first embodiment of the present invention.
[0076] Specifically, FIGS. 10, 11, 13, and 14 show variation of
average temperature and greatest temperature deviation, versus
time, of a hot plate surface of the contrastive baking system. FIG.
10 shows a case where the hot plate is cooled naturally
(hereinafter, Example 1). FIG. 11 shows a case where the hot plate
is cooled by supplying cooling water at a temperature of 23.degree.
C. to each of a first cooling line 206 and a second cooling line
208 at a rate of 1.5 liters per minute (total 3 liters/min)
(hereinafter, Example 2). FIG. 13 shows a case where the hot plate
is cooled by supplying air at a temperature of 23.degree. C.,
instead of cooling water, to each of the first cooling line 206 and
the second cooling line 208 (hereinafter, Example 3). FIG. 14 shows
a case where the hot plate is cooled by supplying cooling water at
a temperature of 18.degree. C. to each of cooling lines 210 buried
in a lower plate 204 installed under the heater 202, at a rate of
1.5 liters per minute (total 3 liters/min) (hereinafter, Example
4). In addition, FIG. 12 shows an amount of time necessary to
stabilize the temperature in Example 2.
[0077] Reference characters G1 of FIG. 10, G3 of FIG. 11, G5 of
FIG. 12, G7 of FIG. 13, and G9 of FIG. 14 indicate first, third,
fifth, seventh, and ninth curves, respectively, showing a variation
of average temperature of the top surface of the hot plate 200 with
time during a cooling process. Reference characters G2 of FIG. 10,
G4 of FIG. 11, G6 of FIG. 12, G8 of FIG. 13, and G10 of FIG. 14
indicate second, fourth, sixth, eighth, and tenth curves showing a
variation of greatest temperature deviation of the hot plate with
time during the cooling process.
[0078] Referring to the first and second curves G1 and G2 of FIG.
10, in Example 1, it took 50 minutes to cool the hot plate from
150.degree. C. to 100.degree. C., and the greatest temperature
deviation of the hot plate 200 ranged from about 0.2.degree. C. to
0.3.degree. C.
[0079] Referring to the third curve, G3 of FIG. 11, in Example 2,
it took only about 10 seconds to cool the hot plate 200 from
150.degree. C. to 100.degree. C. However, as shown by the fourth
curve G4, the greatest temperature deviation of the hot plate 200
had a very high value ranging from 70.degree. C. to 80.degree.
C.
[0080] As a result, in Example 2, as shown in the fifth and sixth
curves G5 and G6 of FIG. 12, it took about 5 minutes to stabilize
the temperature after the hot plate 200 was cooled to 100.degree.
C.
[0081] Next, referring to the seventh and eighth curves, G7 and G8
of FIG. 13, in Example 3, it took a long time to cool the hot plate
200 from 150.degree. C. to 100.degree. C., and the greatest
temperature deviation of the hot plate 200 is expected to be
1.4.degree. C. or more.
[0082] Referring to the ninth and tenth curves, G9 and G10 of FIG.
14, in Example 4, it took about 95 seconds to cool the hot plate
200 from 150.degree. C. to 10020 C., and the greatest temperature
deviation was almost 8.degree. C. Further, it took about 4 minutes
and 20 seconds to stabilize the temperature.
[0083] Meanwhile, FIGS. 18 through 20 are graphs showing simulation
results of the baking system according to the first embodiment of
the present invention. Eleventh and twelfth curves G11 and G12 of
FIG. 18 show a variation in average temperature and greatest
temperature deviation of the top surface of a hot plate,
respectively, with time in a case where a liquid coolant at a
temperature of 23.degree. C. circulates three times at 15-second
intervals (hereinafter, Example 5).
[0084] In FIG. 19, thirteenth and fourteenth curves G13 and G14
show a variation in average temperature and greatest temperature
deviation of the top surface of the hot plate, respectively, with
time in a case where a liquid coolant at a temperature of
50.degree. C. circulates four times at 15-second intervals
(hereinafter, Example 6).
[0085] In FIG. 20, fifteenth and sixteenth curves G15 and G16 show
a variation in the average temperature and greatest temperature
deviation of the top surface of the hot plate, respectively, with
time in a case where a liquid coolant at a temperature of
80.degree. C. circulates six times at 15-second intervals
(hereinafter, Example 7).
[0086] Referring to the eleventh and twelfth curves G1 and G12 of
FIG. 18, in Example 5, the hot plate was cooled to a temperature of
100.degree. C. within 40 seconds, and the greatest temperature
deviation AT of the hot plate was .DELTA.T <0.4.degree. C. at
the end of each interval.
[0087] Further, referring to the thirteenth and fourteenth curves
G13 and G14 of FIG. 19, in Example 6, the hot plate was cooled to a
temperature of 100.degree. C. within 45 seconds and the greatest
temperature deviation .DELTA.T of the hot plate was .DELTA.T
<0.2.degree. C. at the end of each interval.
[0088] In addition, referring to the fifteenth and sixteenth curves
G15 and G16 of FIG. 20, in Example 7, the hot plate was cooled to a
temperature of 100.degree. C. within 75 seconds, and the greatest
temperature deviation AT of the hot plate was .DELTA.T
<0.2.degree. C. at the end of each interval.
[0089] The following Table summarizes the foregoing simulation
results on cooling of the hot plates of the contrastive baking
system and the baking system of the present invention. In the
Table, System 1 indicates the baking system of the present
invention, and System 2 indicates the contrastive baking system. In
addition, a category entitled "the other" represents a case where
cooling water is maintained at a temperature of 18.degree. C. in
Example 2.
1TABLE The greatest Temperature temperature stabilizing Cooling
time deviation time Content (150.degree. C. -> 100.degree. C.)
(.DELTA.T) (.degree. C.) (.DELTA.T < 1.degree. C.) System 1 90
seconds 0.2 1.5 minutes System Example 1 50 minutes 0.2 50 minutes
2 Example 2 10 minutes 78 5 minutes Example 3 Long 1.4 -- Example 4
95 seconds 8 4 and 1/3 minutes The other 10 seconds 80 --
[0090] As shown in the Table, in the contrastive baking system
(System 2), in the cases where the hot plate was cooled using
cooling water (Examples 2 and 4 and the other), the cooling time
was shorter (Example 2 and the other) or similar (Example 4) but
the temperature deviation .DELTA.T was high and a longer amount of
time was necessary to stabilize the temperature of the hot plate,
as compared with the baking system of the present invention (System
1).
[0091] More specifically, in the baking system of the present
invention (System 1), the cooling time was similar or slightly
longer and the temperature stabilizing time was shorter than in the
contrastive baking system and the temperature deviation was the
same as in a natural cooling method (Example 1).
[0092] Meanwhile, in Example 1 using the natural cooling method,
the cooling time and the stabilizing time were much longer than in
the baking system of the present invention. Therefore, despite the
small temperature deviation, Example 1 is not suitable for
practical use.
[0093] As a result, by analyzing the simulation results, it may be
seen that the baking system of the present invention performed
better than any contrastive baking system in consideration of
overall productivity, cooling effect, and temperature
uniformity.
[0094] As described above, the baking system of the present
invention includes a heat pipe, a top surface of which is used as a
hot plate where a wafer to be baked is loaded, and on sides and a
ceiling of which wicks for supplying a working fluid are installed.
Thus, when the top surface is cooled, the working fluid is
uniformly and rapidly supplied to the entire ceiling of the heat
pipe, thus uniformly cooling the entire top surface. The top
surface is cooled by evaporating the working fluid supplied to the
ceiling of the heat pipe. Therefore, a time required for
stabilizing the temperature of the hot plate surface may be
significantly reduced as compared with conventional systems using
circulation of cooling water.
[0095] Further, the heat pipe is connected to a subsidiary cooling
system, which is used to circulate a working fluid through the heat
pipe to cool the top surface. The subsidiary cooling system
includes a coolant storage tank, which is filled with a
predetermined amount of liquid coolant to be exchanged with the
working fluid to cool the top surface, and a cooling unit, which
prevents an increase in temperature of the liquid coolant due to
inflow of the working fluid. In addition, the coolant storage tank
may further include a pressurizing unit, a second cooling system,
or a subsidiary heater, if necessary. The subsidiary cooling system
is able to maintain the working fluid in the heat pipe at a low
temperature during cooling of the top surface of the heat pipe,
thus improving the cooling efficiency of the heat pipe. Also, if
the coolant storage tank includes a subsidiary heater, a time
required for heating the top surface of the heat pipe, i.e., a hot
plate surface, may be reduced to improve semiconductor device
manufacturing productivity.
[0096] Illustrative embodiments of the present invention have been
disclosed herein and, although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. For example, a
coolant storage unit with a subsidiary heater for heating a liquid
coolant can be further used if necessary, in addition to a coolant
storage unit with a cooling unit. Accordingly, it will be
understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
* * * * *