U.S. patent application number 13/259805 was filed with the patent office on 2012-02-23 for method for cooling object to be processed, and apparatus for processing object to be processed.
This patent application is currently assigned to Tokyo Electron Limited. Invention is credited to Takashi Horiuchi, Noritomo Tada.
Application Number | 20120043062 13/259805 |
Document ID | / |
Family ID | 42828230 |
Filed Date | 2012-02-23 |
United States Patent
Application |
20120043062 |
Kind Code |
A1 |
Tada; Noritomo ; et
al. |
February 23, 2012 |
METHOD FOR COOLING OBJECT TO BE PROCESSED, AND APPARATUS FOR
PROCESSING OBJECT TO BE PROCESSED
Abstract
Provided is a method for cooling an object to be processed. The
cooling method is provided with a step of placing the object in a
heated state on a stage, and a step of cooling the object by
blowing a cooling gas to a region the near-center region of the
object placed on the stage, including the center thereof.
Inventors: |
Tada; Noritomo; (Yamanashi,
JP) ; Horiuchi; Takashi; (Yamanashi, JP) |
Assignee: |
Tokyo Electron Limited
Tokyo
JP
|
Family ID: |
42828230 |
Appl. No.: |
13/259805 |
Filed: |
March 30, 2010 |
PCT Filed: |
March 30, 2010 |
PCT NO: |
PCT/JP2010/055687 |
371 Date: |
October 24, 2011 |
Current U.S.
Class: |
165/138 ;
165/185 |
Current CPC
Class: |
H01L 21/67109
20130101 |
Class at
Publication: |
165/138 ;
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2009 |
JP |
2009-081072 |
Claims
1. A cooling method of a target object, comprising: placing the
object in a heated state on a stage; and cooling the object placed
on the stage by spraying a cooling gas to a near-center region of
the object including the center thereof.
2. The method of claim 1, wherein the object that has been heated
to a temperature of 450.degree. C. or more is placed on the stage
and cooled.
3. The method of claim 1, wherein the near-center region of the
object including the center thereof corresponds to a region within
an area having a radius of 75 mm from the center of the object.
4. The method of claim 1, wherein a flow velocity of the cooling
gas is maximized at the center of the object.
5. The method of claim 1, wherein the cooling gas includes a first
cooling gas having a high cooling effect and a second cooling gas
having a cooling effect lower than that of the first cooling gas,
wherein the first cooling gas is sprayed to the near-center region
of the object including the center thereof, and the second cooling
gas is sprayed to a region outside the near-center region of the
object.
6. The method of claim 1, wherein the stage has a cooling mechanism
for cooling the object, and the object is cooled using the cooling
gas and the cooling mechanism.
7. The method of claim 4, wherein the stage has a cooling mechanism
for cooling the object, and the object is cooled using the cooling
gas and the cooling mechanism.
8. The method of claim 5, wherein the stage has a cooling mechanism
for cooling the object, and the object is cooled using the cooling
gas and the cooling mechanism.
9. An object processing apparatus comprising: a load-lock module
which performs pressure conversion between a depressurized state
and an atmospheric pressure state; a stage which is provided in the
load-lock module and on which a target object is placed; and a
cooling gas injection unit which is provided in the load-lock
module to face the stage and sprays a cooling gas to the object
placed on the stage.
10. The object processing apparatus of claim 9, wherein the object
that has been heated to a temperature of 450.degree. C. or more is
placed on the stage and cooled.
11. The object processing apparatus of claim 9, wherein the cooling
gas injection unit is a nozzle.
12. The object processing apparatus of claim 9, wherein the cooling
gas injection unit is a shower head, and a diameter of the shower
head is smaller than a diameter of the object.
13. The object processing apparatus of claim 12, wherein the
diameter of the shower head is equal to or smaller than 150 mm.
14. The object processing apparatus of claim 12, wherein an inside
of the shower head is divided into a plurality of concentric
spaces.
15. The object processing apparatus of claim 9, wherein the cooling
gas injection unit is a shower head, and an inside of the shower
head is divided into a plurality of concentric spaces.
16. The object processing apparatus of claim 14, wherein the
cooling gas includes a first cooling gas having a high cooling
effect and a second cooling gas having a cooling effect lower than
that of the first cooling gas, wherein the first cooling gas is
supplied to one or more of the plurality of spaces, including the
center of the shower head, and the second cooling gas is supplied
to the other spaces outside the spaces to which the first cooling
gas is supplied.
17. The object processing apparatus of claim 15, wherein the
cooling gas includes a first cooling gas having a high cooling
effect and a second cooling gas having a cooling effect lower than
that of the first cooling gas, wherein the first cooling gas is
supplied to one or more of the plurality of spaces, including the
center of the shower head, and the second cooling gas is supplied
to the other spaces outside the spaces to which the first cooling
gas is supplied.
18. The object processing apparatus of claim 9, wherein the stage
has a cooling mechanism for cooling the object.
19. The object processing apparatus of claim 11, wherein the stage
has a cooling mechanism for cooling the object.
20. The object processing apparatus of claim 12, wherein the stage
has a cooling mechanism for cooling the object.
21. The object processing apparatus of claim 14, wherein the stage
has a cooling mechanism for cooling the object.
22. The object processing apparatus of claim 9, wherein the
load-lock module is provided between a loading/unloading module and
a transfer module and performs the pressure conversion between the
atmospheric pressure state and the depressurized state, the
loading/unloading module serving to load/unload the object in the
atmospheric pressure state, and the transfer module serving to
transfer the object between a plurality of processing modules for
performing a process on the object in the depressurized state, and
wherein cooling of the object is performed when the pressure
conversion is performed from the depressurized state to the
atmospheric pressure state.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a cooling method of a
target object and an object processing apparatus capable of
performing the cooling method.
BACKGROUND OF THE INVENTION
[0002] In a manufacturing process of, e.g., semiconductor devices,
a high temperature process such as film formation and thermal
treatment is performed on a semiconductor wafer (hereinafter,
referred to as a "wafer") as a target object. In order to unload
the wafer that has been processed at a high temperature from a
processing apparatus, it is necessary to cool the wafer to a secure
temperature.
[0003] Conventionally, cooling of the wafer is performed in a
load-lock chamber that performs pressure conversion between a
depressurized state and an atmospheric pressure state, and the
wafer is naturally cooled when the depressurized state is converted
into the atmospheric pressure state (see, e.g., Japanese Patent
Publication Application No. 2001-319885).
[0004] However, in a case where the wafer is naturally cooled while
the depressurized state is converted into the atmospheric pressure
state, a decrease in temperature of the wafer is started from an
edge of the wafer. Accordingly, a temperature difference is
generated between the edge and the center of the wafer.
[0005] Recently, the wafer has a larger diameter and a temperature
difference between the edge and the center tends to increase.
Moreover, with the trend of miniaturization of devices, it is
strictly required to prevent deformation of the wafer such as
warpage of the wafer caused by the temperature difference between
the edge and the center.
[0006] Accordingly, currently, the pressure conversion from the
depressurized state to the atmospheric pressure state is performed
slowly to suppress an increase in the temperature difference
between the edge and the center of the wafer.
[0007] By this technique, it is possible to suppress an increase in
the temperature difference between the edge and the center and
prevent the wafer from being warped or cracked.
[0008] However, since the pressure conversion from the
depressurized state to the atmospheric pressure state is performed
slowly, a throughput may be reduced.
SUMMARY OF THE INVENTION
[0009] The present invention provides a cooling method of a target
object capable of improving a throughput while preventing the
warpage or crack of the wafer from being generated to exceed the
allowable range, and an object processing apparatus capable of
performing the cooling method.
[0010] In accordance with a first aspect of the present invention,
there is provided a cooling method of a target object including
placing the object in a heated state on a stage; and cooling the
object placed on the stage by injecting a cooling gas to a
near-center region of the object including a center thereof.
[0011] In accordance with a second aspect of the present invention,
there is provided an object processing apparatus including a
load-lock module for performing pressure conversion between a
depressurized state and an atmospheric pressure state; a stage
which is provided in the load-lock module and on which a target
object is placed; and a cooling gas injection unit which is
provided in the load-lock module to face the stage and injects a
cooling gas to the object placed on the stage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a plan view schematically showing an example of an
object processing apparatus capable of performing a cooling method
of a target object in accordance with an embodiment of the present
invention;
[0013] FIG. 2 is a cross-sectional view schematically showing a
first example of a load-lock module;
[0014] FIG. 3 illustrates a temperature distribution of a
wafer;
[0015] FIGS. 4A to 4C illustrate relationships between a position
in the wafer and a temperature difference;
[0016] FIG. 5 illustrates a relationship between a position in the
wafer and a temperature difference;
[0017] FIG. 6 is an enlarged cross-sectional view showing the
vicinity of a shower head shown in FIG. 2;
[0018] FIGS. 7A to 7C illustrate relationships between an
in-surface temperature difference of the wafer and a diameter of a
shower head;
[0019] FIG. 8 is a cross-sectional view schematically showing a
second example of the load-lock module;
[0020] FIG. 9 is a cross-sectional view schematically showing a
third example of the load-lock module;
[0021] FIG. 10 is a plan view schematically showing the shower head
shown in FIG. 6;
[0022] FIG. 11 is a cross-sectional view schematically showing a
fourth example of the load-lock module;
[0023] FIGS. 12A and 12B are cross-sectional views schematically
showing a fifth example of the load-lock module;
[0024] FIGS. 13A and 13B are cross-sectional views schematically
showing a sixth example of the load-lock module;
[0025] FIG. 14 is a cross-sectional view schematically showing a
seventh example of the load-lock module; and
[0026] FIG. 15 is a plan view schematically showing a modification
example of the object processing apparatus.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0027] Hereinafter, an embodiment of the present invention will be
described with reference to the accompanying drawings which form a
part thereof. Further, the same components are denoted by the same
reference numerals throughout the drawings.
[0028] FIG. 1 is a plan view schematically showing an example of an
object processing apparatus capable of performing a cooling method
of a target object in accordance with the embodiment of the present
invention. As an example of the object processing apparatus of this
embodiment, there will be described an object processing apparatus
for performing a process on a wafer to manufacture semiconductor
devices. However, the present invention may be applied to other
apparatuses without being limited to the object processing
apparatus for performing a process on a wafer.
[0029] As illustrated in FIG. 1, an object processing apparatus 1
in accordance with the embodiment of the present invention includes
a processing unit 2 for performing a process on a wafer W, a
loading/unloading unit 3 for loading/unloading the wafer W
into/from the processing unit 2, and a control unit 4 for
controlling the apparatus 1.
[0030] The object processing apparatus 1 of this embodiment is a
cluster tool type (multi chamber type) semiconductor manufacturing
apparatus.
[0031] In this embodiment, the processing unit 2 includes two
processing modules (PM) (processing modules 21a and 21b) for
performing a process on the wafer W. Each of the processing modules
21a and 21b can be depressurized to a predetermined vacuum level.
For example, in the processing modules 21a and 21b, a PVD process,
e.g., a sputtering process is performed at a high vacuum level (low
pressure), and a specific metal or metal compound film is formed on
a target substrate such as a semiconductor wafer W. The processing
modules 21a and 21b are connected to one transfer module (TM) 22
via gate valves G1 and G2, respectively.
[0032] The loading/unloading unit 3 includes a loading/unloading
module (LM) 31. The loading/unloading module 31 is configured such
that an inner pressure thereof is adjustable to an atmospheric
pressure, or near-atmospheric pressure, e.g., a slightly positive
pressure compared to the outside air pressure. In this embodiment,
the loading/unloading module 31 has a rectangular shape having long
sides and short sides perpendicular to the long sides in its plan
view. One of the long sides of the loading/unloading module 31 is
adjacent to the processing unit 2. In this embodiment, it is
supposed that the long sides are extended in a Y direction, the
short sides are extended in an X direction, and a height direction
is a Z direction.
[0033] The loading/unloading module 31 includes load ports LP on
which carriers C for accommodating wafers W therein are attached.
In this embodiment, three load ports 32a, 32b and 32c for target
substrates are arranged in the Y direction on the long side of the
loading/unloading module 31 opposite to the processing unit 2.
Although the number of the load ports is three in this embodiment,
the number of the load ports may be varied without being limited
thereto. Shutters (not shown) are respectively provided at the load
ports 32a, 32b and 32c. When the carriers C storing the wafers W or
empty carriers C are attached on the load ports 32a, 32b and 32c,
shutters (not shown) are opened such that the carriers C can
communicate with the loading/unloading module 31 while preventing
infiltration of outside air.
[0034] Load-lock modules LLM, e.g., two load-lock modules 51a and
51b in this embodiment, are provided between the processing unit 2
and the loading/unloading unit 3. Each of the load-lock modules 51a
and 51b is configured such that an inner pressure thereof is
switchable between a specific vacuum level and an atmospheric
pressure or near-atmospheric pressure. The load-lock modules 51a
and 51b are connected to one side of the loading/unloading module
31 opposite to the load ports 32a, 32b and 32c via respective gate
valves G3 and G4. The load-lock modules 51a and 51b are also
connected to two of the other sides of the transfer module 22 than
two sides connected to the processing modules 21a and 21b via
respective gate valves G5 and G6.
[0035] The load-lock modules 51a and 51b communicate with the
loading/unloading module 31 by opening the respective gate valves
G3 and G4, and are separated from the loading/unloading module 31
by closing the respective gate valves G3 and G4. Further, the
load-lock modules 51a and 51b communicate with the transfer module
22 by opening the respective gate valves G5 and G6, and are
separated from the transfer module 22 by closing the respective
gate valves G5 and G6.
[0036] A loading/unloading mechanism 35 is provided in the
loading/unloading module 31. The loading/unloading mechanism 35
performs loading/unloading of the wafer W into/from the carriers C
for target substrates. Moreover, the loading/unloading mechanism 35
performs loading/unloading of the wafer W into/from the load-lock
modules 51a and 51b. The loading/unloading mechanism 35 has, e.g.,
two multi-joint arms 36a and 36b and is movable on a rail 37
extending in the Y direction. Hands 38a and 38b are respectively
attached to leading ends of the multi-joint arms 36a and 36b. The
wafer W is loaded on the hand 38a or 38b when the above-described
loading/unloading of the wafer W is performed.
[0037] Provided in the transfer module 22 is a transfer mechanism
24 for performing transfer of the wafer W between the processing
modules 21a and 21b and the load-lock modules 51a and 51b. The
transfer mechanism 24 is located at an approximately central
portion in the transfer module 22. The transfer mechanism 24 has,
e.g., a plurality of rotatable and extensible/contractible transfer
arms. In this embodiment, the transfer mechanism 24 has, e.g., two
transfer arms 24a and 24b. Holders 25a and 25b are respectively
attached to leading ends of the transfer arms 24a and 24b. The
wafer W is supported by the holder 25a or 25b when the transfer of
the wafer W is performed between the processing modules 21a and 21b
and the load-lock modules 51a and 51b as described above.
[0038] The control unit 4 includes a process controller 41, a user
interface 42 and a storage unit 43.
[0039] The process controller 41 has a microprocessor
(computer).
[0040] The user interface 42 includes a keyboard through which
commands are inputted, a display for displaying an operation status
of the object processing apparatus 1 and the like in order to allow
an operator to manage the object processing apparatus 1.
[0041] The storage unit 43 stores control programs for performing a
process in the object processing apparatus 1 under control of the
process controller 41, various types of data, and recipes for
performing a process in the object processing apparatus 1 under
processing conditions. The recipes are stored in a storage medium
of the storage unit 43.
[0042] The storage medium may be a computer-readable medium, e.g.,
a hard disk, or a portable medium such as a CD-ROM, a DVD and a
flash memory. Further, the recipes may be appropriately transmitted
from another apparatus via, e.g., a dedicated line. Upon receipt of
a command from the user interface 42, the process controller 41
retrieves a desired recipe from the storage unit 43, and the
process controller 41 executes a process corresponding to the
retrieved recipe, so that a desired process is performed on the
wafer W in object processing apparatus 1 under the control of the
process controller 41.
[0043] FIG. 2 is a cross-sectional view schematically showing a
first example of the load-lock module 51a or 51b.
[0044] As illustrated in FIG. 2, provided in the load-lock module
51a or 51b is a stage on which the wafer W is mounted, e.g., a
cooling stage in this embodiment, e.g., a cooling stage 52 having a
water cooling mechanism 52a.
[0045] At a ceiling wall 53 of the load-lock module 51a or 51b,
there is provided a cooling gas injection unit, e.g., a shower head
54 in this embodiment. The shower head 54 is provided to face the
cooling stage 52. The wafer W is mounted on the cooling stage 52
such that the center of the wafer W is aligned with the center of
the shower head 54.
[0046] A cooling gas is supplied into the shower head 54 from a
cooling gas supply mechanism 60 through a flow control valve 61.
For example, a rare gas or an inert gas such as N.sub.2 gas, He gas
and Ar gas may be used as the cooling gas. A plurality of cooling
gas injection holes 54a are formed on a surface of the shower head
54 facing the cooling stage 52.
[0047] Further, in this embodiment, a diameter .PHI.S of the shower
head 54 is set to be smaller than a diameter .PHI.W of the wafer W.
By setting the diameter .PHI.S to be smaller than the diameter
.PHI.W, the cooling gas 70 can be locally injected to a near-center
region of the wafer W including the center thereof instead of being
injected uniformly to the entire surface of the wafer W.
[0048] A gas exhaust port 56 is formed at a bottom wall 55 of the
load-lock module 51a or 51b. The gas exhaust port 56 is connected
to a gas exhaust unit 62 for evacuating the load-lock module 51a or
51b to a predetermined vacuum level.
[0049] Further, a gas inlet port 57 is formed at the bottom wall 55
of the load-lock module 51a or 51b. The gas inlet port 57 is
connected to the cooling gas supply mechanism 60 through a flow
control valve 63 in this embodiment. The inner pressure of the
load-lock module 51a or 51b may be increased to a pressure
approximately equal to the inner pressure of the loading/unloading
module 31, e.g., an atmospheric pressure or a pressure slightly
lower than the inner pressure of the loading/unloading module 31 by
introducing the cooling gas from the gas inlet port 57 and the
shower head 54. FIG. 3 illustrates an in-surface temperature
distribution of the wafer W.
[0050] As illustrated in FIG. 3, when the wafer W is naturally
cooled, the temperature of the edge of the wafer W decreases at the
fastest rate, whereas the temperature of the center of the wafer W
decreases at the slowest rate. Accordingly, while the temperature
of the wafer W decreases, there occurs an in-surface temperature
difference in such a way that the temperature is high at the center
and low at the edge (see the curve I of FIG. 3). If there is a
large difference in the in-surface temperature, the wafer W may be
warped or cracked during the cooling. An allowable warpage range of
the wafer W is, e.g., equal to or smaller than 0.6 mm in the wafer
having a diameter .PHI.W of 300 mm.
[0051] The in-surface temperature difference generated in the wafer
W will be described in detail with reference to FIGS. 4A to 4C.
[0052] FIG. 4A illustrates an in-surface temperature difference
when the ambient pressure of the wafer W is 1 Pa and the wafer W is
heated to a temperature of about 500.degree. C. The diameter .PHI.W
of the wafer W is 300 mm, and the temperature is measured at the
center (0 mm), the middle (.+-.75 mm from the center) and the
near-edge (.+-.140 mm from the center).
[0053] In FIG. 4A, the temperature of the near-edge is about
500.degree. C. From the measurement results, it is seen that the
temperature of the middle is about 20.degree. C. higher than the
temperature of the near-edge (i.e., about 520.degree. C.) and the
temperature of the center is about 25.degree. C. higher than the
temperature of the near-edge (i.e., about 525.degree. C.).
[0054] The wafer W is exposed to the air at a time, so that the
state of the wafer W is changed from the depressurized state of
FIG. 4A to a state in which the ambient pressure of the wafer W is
an atmospheric pressure (about 100000 Pa) and the temperature of
the wafer W is decreased to about 70.degree. C. FIG. 4C illustrates
a state in which the wafer W is cooled to a temperature of about
70.degree. C.
[0055] As illustrated in FIG. 4C, when the wafer W is cooled to a
temperature of about 70.degree. C., the in-surface temperature
difference in the center, the middle and the near-edge is equal to
or smaller than about 6.degree. C. (the temperature of the center
is about 70.degree. C. and the temperature of the near-edge is
about 64.degree. C.). That is, the in-surface temperature
difference is reduced compared to a maximum difference of about
25.degree. C. before the start of cooling.
[0056] However, since the decrease in the temperature of the wafer
W is started from the edge during the cooling, the temperature of
the center decreases at the slowest rate. In particular, this
tendency appears remarkably in the cooling after the wafer W is
exposed to the air at a time, i.e., the wafer W is subjected to the
natural cooling. Accordingly, as shown in FIG. 4B, the in-surface
temperature difference increases during the cooling. The increase
in the in-surface temperature difference may cause a warpage or
crack of the wafer W, which exceeds, e.g., 0.6 mm.
[0057] In order to prevent the warpage or crack from being
generated, pressure conversion is slowly performed from the
depressurized state to the atmospheric pressure state, and rapid
decrease in the temperature of the edge is suppressed during the
cooling to reduce the in-surface temperature difference (see the
curve II of FIG. 3, and FIG. 5). However, since the pressure
conversion from the depressurized state to the atmospheric pressure
state is performed slowly, the throughput may be reduced.
[0058] Accordingly, in this embodiment, the cooling gas 70 is
locally injected to the near-center region of the wafer W including
the center thereof by using the shower head 54. By this
configuration, it is possible to control the temperature decrease
in the near-center region of the wafer W to be equivalent to the
temperature decrease in the near-edge region of the wafer W.
[0059] The spray of the cooling gas 70, i.e., the cooling of the
wafer W is performed when the pressure conversion is performed from
the depressurized state to the atmospheric pressure state in the
load-lock module 51a or 51b. In this case, the cooling gas may be
also supplied from the gas inlet port 57 into the load-lock module
51a or 51b to perform the pressure conversion from the
depressurized state to the atmospheric pressure state.
[0060] Further, since the cooling stage 52 has the cooling
mechanism 52a for cooling the wafer W in this embodiment, the
cooling of the wafer W is performed by using the cooling gas 70 and
the cooling mechanism 52a.
[0061] As described above, in this embodiment, the cooling gas 70
is locally sprayed to the near-center region of the wafer W
including the center thereof to accelerate the decrease in the
temperature of the near-center region of the wafer W. Accordingly,
it is possible to cool the wafer W at the faster rate compared to a
case where the pressure conversion is slowly performed from the
depressurized state to the atmospheric pressure state while the
rapid decrease in the temperature of the edge of the wafer W is
suppressed during the cooling.
[0062] Further, the temperature decrease in the near-center region
of the wafer W is controlled to be equivalent to the temperature
decrease in the near-edge region of the wafer W. Accordingly, it is
possible to prevent the wafer W from being warped or cracked to
exceed the allowable range.
FIRST EXAMPLE
[0063] FIG. 6 is an enlarged cross-sectional view showing the
vicinity of the shower head 54 shown in FIG. 2.
[0064] As shown in FIG. 6, the cooling gas 70 injected from the
shower head 54 has a flow velocity distribution in which the flow
velocity is high in the center and becomes lower as it approaches
the edge of the wafer W (see the curve III of FIG. 6). This flow
velocity distribution is formed by setting the diameter .PHI.S of
the shower head 54 to be smaller than the diameter .PHI.W of the
wafer W, for example.
[0065] Further, when the wafer W is mounted on the stage 52 such
that the center of the wafer W is aligned with the center of the
shower head 54, the flow velocity of the cooling gas 70 can be
maximized at the center of the wafer W. Further, the flow velocity
distribution of the cooling gas 70 may be formed in such a way that
the flow velocity is high in the near-center region of the wafer W
including the center thereof and becomes lower as it goes from the
near-center region toward the edge of the wafer W.
[0066] By such flow velocity distribution, it is possible to
efficiently cool the center of the wafer W in which the temperature
decreases at the slowest rate, and reduce a cooling effect as it
goes toward the edge of the wafer W in which the temperature
decreases at the faster rate. Accordingly, it is possible to easily
allow the temperature of the center of the wafer W to approximate
the temperature of the edge of the wafer W.
[0067] Next, an example of setting the diameter .PHI.S of the
shower head 54 will be described.
[0068] For example, the diameter .PHI.S of the shower head 54 may
be set according to the in-surface temperature difference of the
wafer W before the start of cooling.
[0069] For example, in case of reducing the temperature of a region
of the wafer W having an in-surface temperature difference of
20.degree. C. or more, the diameter .PHI.S of the shower head 54
may have a size corresponding to the region having an in-surface
temperature difference of 20.degree. C. or more.
[0070] FIG. 7A illustrates an in-surface temperature distribution
when the wafer W having a diameter .PHI.W of 300 mm was heated to
about 500.degree. C. The in-surface temperature distribution of
FIG. 7A is equivalent to the in-surface temperature distribution of
FIG. 4A. As shown in FIG. 7A, the region having an in-surface
temperature difference of 20.degree. C. or more corresponds to a
region in which a distance from the center falls within a range
from -75 mm to +75 mm. In this case, the diameter .PHI.S of the
shower head 54 is set to be 150 mm. Further, the wafer W may be
mounted on the stage 52 such that the center of the wafer W is
aligned with the center of the shower head 54. In this case, the
near-center region of the wafer W including the center thereof
corresponds to a region within an area having a radius of 75 mm
from the center of the wafer W.
[0071] It goes without saying that the region of the wafer W, the
temperature of which is intended to be reduced, may be varied
without being limited to the region having an in-surface
temperature difference of 20.degree. C. or more. As for the wafer W
that has the diameter .PHI.W of 300 mm and is heated to a
temperature of about 500.degree. C., for example, in a case where
the region of the wafer W, the temperature of which is intended to
be reduced, is a region having an in-surface temperature difference
of 15.degree. C. or more, it is preferable that the diameter .PHI.S
of the shower head 54 is set to be 200 mm as shown in FIG. 7B.
[0072] In the same way, the wafer W may be mounted on the stage 52
such that the center of the wafer W is aligned with the center of
the shower head 54. In this case, the near-center region of the
wafer W including the center thereof corresponds to a region within
an area having a radius of 100 mm from the center of the wafer
W.
[0073] Further, in the wafer W that has the diameter .PHI.W of 300
mm and is heated to a temperature of about 500.degree. C., for
example, in a case where the region of the wafer W, the temperature
of which is intended to be reduced, is a region having an
in-surface temperature difference of 22.degree. C. or more, it is
preferable that the diameter .PHI.S of the shower head 54 is set to
be 100 mm as shown in FIG. 7C. In this case, the near-center region
of the wafer W including the center thereof corresponds to a region
within an area having a radius of 50 mm from the center of the
wafer W.
[0074] That is, the diameter .PHI.S of the shower head 54 may be
set based on the diameter .PHI.W of the wafer W and the size of the
region, the temperature of which is intended to be reduced.
Further, the size of the region, the temperature of which is
intended to be reduced, may be determined based on the in-surface
temperature difference generated in the wafer W while the wafer W
is heated.
[0075] It is not limited to the wafer W having the diameter .PHI.W
of 300 mm, and the wafer W may have the diameter .PHI.W of 450
mm.
SECOND EXAMPLE
[0076] Further, the flow velocity distribution represented by the
curve III of FIG. 6 may be obtained by providing a nozzle 54b as
shown in FIG. 8 instead of the shower head 54.
THIRD EXAMPLE
[0077] Further, in case of using the shower head 54, the inside of
the shower head 54 may be divided into a plurality of spaces, e.g.,
two or more concentric spaces such as spaces 54c and 54d as shown
in FIG. 9. FIG. 10 is a plan view of the spaces 54c and 54d shown
in FIG. 9.
[0078] In case of providing the concentric spaces 54c and 54d, the
flow velocity of the cooling gas 70 injected from the space 54c
including the center of the shower head 54 may be set to be higher
than the flow velocity of the cooling gas 70 injected from the
space 54d provided outside the space 54c by varying a flow rate of
the cooling gas supplied to the space 54c, for example. That is,
the cooling gas 70 is sprayed at the higher flow velocity to a
portion particularly close to the center in the near-center region
including the center of the wafer W, thereby further improving
cooling efficiency of the near-center region of the wafer W
including the center thereof.
[0079] In order to control the flow velocity of the cooling gas 70,
a flow velocity controller, e.g., a speed controller, may be
provided in a supply path of the cooling gas, so that the flow
velocity of the injected cooling gas 70 can be controlled by using
the speed controller.
[0080] Further, if the flow velocity of the injected cooling gas 70
is defined as follows:
[0081] Flow velocity of cooling gas=Flow rate of cooling gas/total
area of cooling gas injection holes 54a, the flow velocity of the
injected cooling gas 70 can be controlled by adjusting the flow
rate of the cooling gas 70. In this case, a flow rate controller,
e.g., a mass flow controller, may be provided in the supply path of
the cooling gas, so that the flow rate of the cooling gas can be
adjusted by using the mass flow controller.
[0082] Further, in a case where the inside of the shower head 54 is
divided into a plurality of spaces, e.g., the spaces 54c and 54d, a
first cooling gas having a high cooling effect may be introduced
into the space 54c including the center of the shower head 54, and
a second cooling gas having a cooling effect lower than that of the
first cooling gas may be introduced into the space 54d provided
outside the space 54c. For example, He gas and N.sub.2 gas may be
used as the first gas and the second gas, respectively.
[0083] Further, when the first gas is He gas and the second gas is
N.sub.2 gas, the flow velocity of the He gas may be set to be
higher than the flow velocity of the N.sub.2 gas, thereby further
improving cooling efficiency of the near-center region of the wafer
W including the center thereof.
[0084] In accordance with the shower head 54 shown in FIGS. 9 and
10, it is possible to further enhance cooling efficiency in the
center of the wafer W, and also reduce a cooling effect as it goes
toward the edge of the wafer W.
FOURTH EXAMPLE
[0085] Further, in accordance with the shower head 54 shown in
FIGS. 9 and 10, the diameter of the shower head 54 may be increased
to be equal to the diameter of the wafer W as shown in FIG. 11.
[0086] In a case where the diameter of the shower head 54 is
increased to be equal to the diameter of the wafer W, three or more
spaces such as concentric spaces 54d, 54e, 54f and 54g may be
formed outside the space 54c including the center of the shower
head 54. The flow velocities of the cooling gases injected from the
spaces 54d, 54e, 54f and 54g may be sequentially reduced in an
outward direction to obtain the flow velocity distribution
represented by the curve III of FIG. 11.
[0087] In order to control the flow velocity of the injected
cooling gas 70, as described in the third example, a flow velocity
controller such as a speed controller, or a flow rate controller,
e.g., a mass flow controller, may be provided in the supply path of
the cooling gas, so that the flow velocity or the flow rate of the
injected cooling gas 70 can be controlled by using the flow
velocity controller or the flow rate controller.
[0088] Further, a first cooling gas (e.g., He gas) having a high
cooling effect may be introduced into the space 54c including the
center of the shower head 54 or the space 54c including the center
and the space 54d adjacent to the space 54c, and a second cooling
gas (e.g., N.sub.2 gas) having a cooling effect lower than that of
the first cooling gas may be introduced into the spaces 54d to 54g
provided outside the space 54c, or the spaces 54e to 54g provided
outside the space 54d.
FIFTH EXAMPLE
[0089] Further, the temperature decrease of the wafer W is closely
dependent on a distance D between the shower head 54 and the wafer
W. For example, if the distance D between the shower head 54 and
the wafer W is short, the cooling effect is high, and if the
distance D is long, the cooling effect is low. The temperature
decrease of the wafer W may be controlled by using this
tendency.
[0090] Accordingly, as shown in FIGS. 12A and 12B, the distance D
between the shower head 54 and the wafer W may be varied by using a
structure capable of adjusting a vertical level of the stage
52.
SIXTH EXAMPLE
[0091] In case of varying the distance between the shower head 54
and the wafer W, the structure capable of adjusting the vertical
level of the stage 52 is used in the fifth example. However, as
shown in FIGS. 13A and 13B, it is possible to employ a structure
capable of adjusting a vertical level of the shower head 54.
[0092] Also in the sixth example, it is possible to obtain an
advantage of the fifth example by varying the distance D between
the wafer W and the shower head 54.
SEVENTH EXAMPLE
[0093] In the first to sixth examples, one shower head 54 or one
nozzle 54b is installed in the load-lock module 51a or 51b.
[0094] However, as shown in FIG. 14, a plurality of shower heads 54
or nozzles 54b may be installed in the load-lock module 51a or 51b
to simultaneously cool a plurality of wafers W. FIG. 14 illustrates
an example in which two shower heads 54 of the first example shown
in FIG. 6 are attached to the ceiling wall 53.
[0095] The modification of the seventh example may be applied to
any one of the second to sixth examples without being limited to
the first example.
Modification Example of Object Processing Apparatus
[0096] In the first to seventh examples, the wafer W is cooled in
the load-lock module 51a or 51b of the object processing apparatus
1.
[0097] However, as shown in FIG. 15, a cooling module (CM) 81 for
cooling the wafer W may be provided in the processing unit 2 such
that the wafer W can be cooled in the cooling module 81 instead of
the load-lock module 51a or 51b during or after a process. In this
case, the cooling module 81 employs the structure of the first to
seventh examples. Accordingly, also in the cooling module 81
provided in the processing unit 2, it is possible to obtain the
same advantage as those of the first to seventh examples.
Heating Temperature of Target Object Preferably Used in the
Embodiment
[0098] The target object may have a deformation point as a
temperature at which rapid deformation occurs. For example, in a
case where the target object is the wafer W and is made of silicon,
a temperature of about 450.degree. C. is the deformation point. The
silicon wafer undergoes rapid deformation when it is heated to
exceed the temperature of 450.degree. C. from the temperature of
450.degree. C. or less. On the other hand, the silicon wafer
undergoes rapid deformation when it is cooled below the temperature
of 450.degree. C. from the temperature of 450.degree. C. or
more.
[0099] Accordingly, the above-described embodiment may be
preferably applied to a cooling process performed after a silicon
wafer serving as a target object is heated to a temperature of
450.degree. C. or more.
[0100] Further, a physical upper limit of the heating temperature
is a melting point of silicon that ranges from about 1410 to
1420.degree. C. or less. Furthermore, a practical upper limit of
the heating temperature in an actual process may be 900.degree.
C.
[0101] As described above, in accordance with the embodiment of the
present invention, it is possible to provide a cooling method of a
target object capable of improving a throughput while preventing
the wafer from being warped or cracked to exceed the allowable
range, and an object processing apparatus using the cooling
method.
[0102] Although the present invention has been described using the
embodiment, the present invention is not limited thereto, and
modifications may be appropriately made without departing from the
spirit of the present invention. Further, the above-described
embodiment of the present invention is not the only embodiment.
[0103] For example, although the cooling stage 52 having the
cooling mechanism 52a for cooling the wafer W is used in the
above-described embodiment, the stage may not necessarily include
the cooling mechanism 52a.
[0104] Further, in the aforementioned embodiment, the gas inlet
port 57 is provided in the load-lock module 51a or 51b and, in the
pressure conversion from the depressurized state to the atmospheric
pressure state, the cooling gas is also introduced from the gas
inlet port 57 to create an atmospheric pressure state.
[0105] However, the gas inlet port 57 may not be provided, and the
introduction of the cooling gas from the gas inlet port 57 may not
be performed in the pressure conversion from the depressurized
state to the atmospheric pressure state. In this case, the pressure
conversion from the depressurized state to the atmospheric pressure
state is performed only by the introduction of the cooling gas from
the cooling gas injection unit, i.e., the shower head 54 or the
nozzle 54b in this embodiment.
[0106] Further, the target object, e.g., the wafer W, after being
heated is placed in a high depressurized state having a pressure of
1 Pa and then cooled until the depressurized state is converted
into the atmospheric pressure state in the above-described
embodiment. However, the cooling process may be performed even when
the ambient pressure of the wafer W is not 1 Pa, for example, when
the pressure state ranging from 1 to 70000 Pa is converted into the
atmospheric pressure state (about 100000 Pa).
[0107] In the same way, the cooling process may be performed even
when it is not converted into the atmospheric pressure state, for
example, when it is converted into a pressure ranging from, e.g.,
20000 Pa to an atmospheric pressure.
[0108] Further, the semiconductor wafer is used as an example of
the target object and the silicon wafer is used as an example of
the semiconductor wafer in the above-described embodiment. However,
the present invention may be also applied to other semiconductor
wafers such as SiC, GaAs, InP wafers without being limited to the
silicon wafer.
[0109] Further, the target object may be a glass substrate used for
the manufacture of a flat panel display (FPD) or solar cell without
being limited to the semiconductor wafer. The present invention may
be applied to any object capable of being heated.
[0110] In accordance with the embodiment of the present invention,
it is possible to provide a cooling method of a target object
capable of improving a throughput while preventing the wafer from
being warped or cracked to exceed the allowable range, and an
object processing apparatus using the cooling method.
* * * * *