U.S. patent application number 13/070786 was filed with the patent office on 2012-03-29 for apparatus for and method of processing substrate.
Invention is credited to Hiroaki KITAGAWA, Katsuhiko MIYA.
Application Number | 20120073599 13/070786 |
Document ID | / |
Family ID | 45869374 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120073599 |
Kind Code |
A1 |
MIYA; Katsuhiko ; et
al. |
March 29, 2012 |
APPARATUS FOR AND METHOD OF PROCESSING SUBSTRATE
Abstract
A rinsing liquid adheres to a substrate subjected to a cleaning
process. The rinsing liquid on the substrate is first replaced with
IPA liquid. While the substrate covered with the IPA liquid is held
in a dryer chamber, liquid carbon dioxide is supplied to the
surface of the substrate. Liquid nitrogen is supplied to cool down
the interior of the dryer chamber. This solidifies the liquid
carbon dioxide on the substrate into solid carbon dioxide.
Thereafter, the pressure in the dryer chamber is returned to
atmospheric pressure, and gaseous nitrogen is supplied into the
dryer chamber. Thus, the temperature in the dryer chamber
increases. The solid carbon dioxide on the surface of the substrate
is sublimated, and is hence removed from the substrate. All of the
steps are performed while carbon dioxide is not in a supercritical
state but in a non-supercritical state.
Inventors: |
MIYA; Katsuhiko; (Kyoto-shi,
JP) ; KITAGAWA; Hiroaki; (Kyoto-shi, JP) |
Family ID: |
45869374 |
Appl. No.: |
13/070786 |
Filed: |
March 24, 2011 |
Current U.S.
Class: |
134/4 ;
134/94.1 |
Current CPC
Class: |
B08B 7/0014 20130101;
H01L 21/67028 20130101; H01L 21/67034 20130101 |
Class at
Publication: |
134/4 ;
134/94.1 |
International
Class: |
B08B 3/00 20060101
B08B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2010 |
JP |
JP2010-218669 |
Claims
1. A substrate processing apparatus for removing a first liquid
from a substrate with said first liquid adhering thereto,
comprising: a process chamber for receiving said substrate therein;
a liquid supply part for supplying a second liquid made of a
predetermined material different from that of said first liquid to
said substrate received in said process chamber, with said first
liquid adhering to said substrate; a solidifying part for
solidifying said predetermined material on said substrate; and a
removing part for changing at least one of temperature and pressure
in said process chamber to sublimate the solidified predetermined
material, thereby removing said predetermined material from said
substrate.
2. The substrate processing apparatus according to claim 1, wherein
said first liquid is a replacement liquid used for replacement of a
remaining liquid left on said substrate after a predetermined
process and having a solidification temperature lower than that of
said remaining liquid.
3. The substrate processing apparatus according to claim 2, wherein
the solidification temperature of said replacement liquid is lower
than the temperature of said predetermined material at the triple
point thereof.
4. The substrate processing apparatus according to claim 1, wherein
the predetermined material that is liquefied is supplied from said
liquid supply part toward said substrate while the pressure and
temperature in said process chamber are higher than the pressure
and temperature of said predetermined material at the triple point
thereof.
5. The substrate processing apparatus according to claim 4, wherein
in an initial stage of a process period over which said liquid
supply part supplies a liquid of said predetermined material to
said substrate, a gas of said predetermined material is supplied to
said process chamber that is hermetically closed to cause the
pressure and temperature in said process chamber to be higher than
the pressure and temperature of said predetermined material at the
triple point thereof, thereby causing said predetermined material
continuously supplied to said process chamber to adhere in a liquid
phase to said substrate.
6. The substrate processing apparatus according to claim 1, wherein
said solidifying part is a part for cooling said predetermined
material on said substrate.
7. The substrate processing apparatus according to claim 6, wherein
said removing part is a part for raising the temperature in said
process chamber.
8. The substrate processing apparatus according to claim 7, further
comprising a temperature adjusting part for raising the temperature
of said substrate obtained after said predetermined material is
sublimated.
9. The substrate processing apparatus according to claim 1, wherein
said solidifying part is a part for releasing an atmosphere in said
process chamber to an atmospheric environment.
10. The substrate processing apparatus according to claim 9,
wherein said removing part is a part for raising the temperature in
said process chamber.
11. The substrate processing apparatus according to claim 10,
further comprising a temperature adjusting part for raising the
temperature of said substrate obtained after said predetermined
material is sublimated.
12. The substrate processing apparatus according to claim 1,
wherein said predetermined material is a material with a pressure
of one atmosphere or higher at the triple point thereof.
13. A method of processing a substrate to remove a first liquid
from the substrate with said first liquid adhering thereto, said
method comprising the steps of: (a) adjusting an atmosphere
surrounding said substrate with said first liquid adhering thereto
to an atmosphere having temperature and pressure higher than the
temperature and pressure of a predetermined material at the triple
point thereof; (b) supplying a second liquid made of said
predetermined material to said substrate; (c) solidifying said
predetermined material on said substrate; and (d) changing at least
one of the temperature and pressure in said process chamber to
sublimate the solidified predetermined material, thereby removing
said predetermined material from said substrate.
14. The method according to claim 13, wherein said first liquid is
a replacement liquid used for replacement of a remaining liquid
left on said substrate after a predetermined process and having a
solidification temperature lower than that of said remaining
liquid.
15. The method according to claim 14, wherein the solidification
temperature of said replacement liquid is lower than the
temperature of said predetermined material at the triple point
thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a substrate processing
apparatus and a substrate processing method which remove liquid
adhering to various substrates (referred to simply as "substrates"
hereinafter) including a semiconductor substrate, a glass substrate
for a flat panel display, a substrate for an optical disk, a solar
cell panel and the like from the substrates.
[0003] 2. Description of the Background Art
[0004] In the process steps of manufacturing a semiconductor
device, for example, a variety of wet processes using liquid are
performed on a substrate, and a drying process is then performed on
the substrate subjected to such wet processes. In the process of
development in photolithography, a chemical liquid such as a
developing solution is applied to a substrate to which a pattern is
transferred by exposure to light, and thereafter the substrate is
cleaned using a rinsing liquid to remove the chemical liquid from
the substrate. The rinsing liquid is replaced with a replacement
liquid such as isopropyl alcohol (IPA), and the substrate is dried
by removing the replacement liquid.
[0005] In recent years, however, there has been a tendency for
patterns formed on substrate surfaces to become finer. This gives
rise to a problem such that, in the drying process of the
replacement liquid, surface tension (or capillary force) acting on
a boundary surface between the liquid entering the microstructure
of a pattern and a gas in contact with the liquid causes adjacent
protruding portions of the pattern to attract each other, thereby
collapsing the adjacent protruding portions.
[0006] To prevent the collapse of the pattern resulting from such
capillary force, there has been a known substrate drying technique
using a supercritical fluid. The supercritical fluid is low in
viscosity, high in diffusibility, and has no surface tension. There
is hence no apprehension that the supercritical fluid brings about
the collapse of the pattern when supplied to the substrate.
Japanese Patent Application Laid-Open No. 2008-072118 discloses a
technique in which carbon dioxide in a supercritical state is
supplied to a pattern formed on the surface of a substrate and is
then vaporized, whereby the surface of the substrate is dried.
[0007] As disclosed in Japanese Patent Application Laid-Open No.
2008-072118, carbon dioxide is relatively easily brought into the
supercritical state. However, a high-pressure environment having a
pressure as high as 73 atmospheres or more must be set to achieve
the supercritical state. Thus, the setting of such an environment
in which the supercritical state is achievable necessitates an
apparatus for achieving and maintaining a high-pressure state. The
provision of such an apparatus requires apparatus costs. These
problems become considerations not only in the process of drying
the substrate by the removal of the replacement liquid but also in
the general processes of removing liquid remaining on the substrate
from the substrate.
SUMMARY OF THE INVENTION
[0008] The present invention is intended for a substrate processing
apparatus and a substrate processing method which are capable of
drying a substrate without collapsing a pattern provided on the
substrate in an environment with a pressure lower than that
required to achieve a supercritical state.
[0009] According to a first aspect of the present invention, a
substrate processing apparatus for removing a first liquid from a
substrate with the first liquid adhering thereto comprises: a
process chamber for receiving the substrate therein; a liquid
supply part for supplying a second liquid made of a predetermined
material different from that of the first liquid to the substrate
received in the process chamber, with the first liquid adhering to
the substrate; a solidifying part for solidifying the predetermined
material on the substrate; and a removing part for changing at
least one of temperature and pressure in the process chamber to
sublimate the solidified predetermined material, thereby removing
the predetermined material from the substrate.
[0010] According to a second aspect of the present invention, a
method of processing a substrate to remove a first liquid from the
substrate with the first liquid adhering thereto comprises the
steps of: (a) adjusting an atmosphere surrounding the substrate
with the first liquid adhering thereto to an atmosphere having
temperature and pressure higher than the temperature and pressure
of a predetermined material at the triple point thereof; (b)
supplying a second liquid made of the predetermined material to the
substrate; (c) solidifying the predetermined material on the
substrate; and (d) changing at least one of the temperature and
pressure in the process chamber to sublimate the solidified
predetermined material, thereby removing the predetermined material
from the substrate.
[0011] According to the present invention, the predetermined
material is supplied in a liquid phase onto the substrate, and is
then solidified. Thereafter, the predetermined material in a solid
phase is sublimated, and is hence removed from the substrate. Thus,
capillary force does not act on the substrate. This prevents
damages to a pattern provided on the substrate. Also, for the
solidification of a material, it is in general sufficient to use a
pressure lower than that required to place the material into a
supercritical state. The present invention therefore eliminates the
need to provide facilities for achieving a high-pressure
environment, thereby reducing apparatus costs.
[0012] These and other objects, features, aspects and advantages of
the present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a top plan view of a substrate processing
apparatus according to a first preferred embodiment of the present
invention;
[0014] FIG. 2 is a sectional view of a developer unit taken along a
plane defined by X- and Z-axes according to the first preferred
embodiment of the present invention;
[0015] FIG. 3 is a sectional view of a dryer unit taken along a
plane defined by X- and Z-axes according to the first preferred
embodiment of the present invention;
[0016] FIG. 4 is a phase diagram of carbon dioxide showing changes
in temperature and pressure in procedures according to the first
preferred embodiment and a second preferred embodiment of the
present invention;
[0017] FIG. 5 is a flow diagram showing the procedure according to
the first preferred embodiment of the present invention;
[0018] FIGS. 6 to 12 are schematic views partly showing the
procedure according to the first preferred embodiment of the
present invention;
[0019] FIG. 13 is a sectional view of another dryer unit taken
along a plane defined by X- and Z-axes according to the second
preferred embodiment of the present invention; and
[0020] FIG. 14 is a flow diagram showing the procedure according to
the second preferred embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Preferred embodiments according to the present invention
will now be described with reference to the accompanying drawings.
The preferred embodiments to be described below are examples
embodying the present invention, and do not limit the technical
scope of the present invention.
First Preferred Embodiment
[0022] A substrate processing apparatus 1 as shown in FIG. 1 is a
system of process units which is used, for example, in the course
of a developing process of a semiconductor substrate W for use as a
material of a semiconductor device, and which performs a cleaning
process and a drying process after the developing process. The
substrate processing apparatus 1 principally includes a substrate
station 5, a transfer unit 20, a developer unit 10, and a dryer
unit 30. The substrate processing apparatus 1 to be described below
is configured as, but not limited to, a single-substrate type
processing system for serially processing wafers or substrates W,
and may be configured as a batch-type processing system.
[0023] The substrate station 5 includes a plurality of cassettes 51
(in this preferred embodiment, three cassettes 51a, 51b and 51c)
placed thereon. A partition wall divides the developer unit 10 and
the dryer unit 30 from each other. Substrates W subjected to an
exposure process are stored in a stacked relation in each of the
cassettes 51. The substrates W placed on the substrate station 5
are transported by the transfer unit 20 in sequential order to the
developer unit 10 and to the dryer unit 30.
[0024] The transfer unit 20 includes a first hand 21, a second hand
22, an extendable and retractable arm capable of pivoting each of
the first hand 21 and the second hand 22 about a vertical axis, and
a swivelable substrate support (not shown) provided on the distal
end of each of the arms. The transport of the substrates W is
performed efficiently by the first hand 21 and the second hand
22.
[0025] The developer unit 10 shown in FIG. 2 is a device for
applying a developing solution to a top major surface of an exposed
substrate W, to thereby develop an exposure pattern of a resist
layer and the like on the substrate W. The developer unit 10
includes a substrate holder 182 having a substrate support plate
181 of a planar size approximately equal to that of the substrate
W, and a plurality of peripheral support pins 180 rigidly secured
to the top surface of the substrate support plate 181. The
peripheral support pins 180 support the peripheral portion of the
substrate W. This allows the substrate W to be held in a
substantially horizontal position. The substrate support plate 181
is coupled to a rotary shaft 150 of a motor 151, and rotates as the
motor 151 operates.
[0026] A chemical liquid supplied to the substrate W in the
developer unit 10 is the developing solution. After the developing
process using the developing solution is completed, the developing
solution is removed by being replaced with a rinsing liquid. Then,
the rinsing liquid is replaced with a replacement liquid. The
developing solution is stored in a developing solution supply
source 100, and is supplied through a slit nozzle 105 onto the top
major surface of the substrate W by opening a valve 101 provided in
a pipe 106 providing a connection between the developing solution
supply source 100 and the slit nozzle 105. This causes the
developing solution to spread over the top major surface of the
substrate W, thereby forming a developing solution layer. In this
manner, the developing solution in the form of a puddle is held on
the top major surface of the substrate W for a predetermined length
of time. In general, an alkaline aqueous solution is used as the
developing solution. However, an organic developing solution such
as butyl acetate may be used, depending on the type of a
photoresist.
[0027] A discharge nozzle 125 provided over the substrate holder
182 is used in common for the rinsing liquid and the replacement
liquid. Specifically, the discharge nozzle 125 is coupled through a
pipe 116 to a rinsing liquid supply source 110, and is also coupled
through a pipe 126 to a replacement liquid supply source 120. A
valve 111 is provided in the pipe 116, and a valve 121 is provided
in the pipe 126. Switching between the opening and closing of the
valves 111 and 121 permits the selective discharge of the rinsing
liquid or the replacement liquid from the discharge nozzle 125. It
should be noted that the rinsing liquid and the replacement liquid
may be discharged from respective separate discharge nozzles.
[0028] When the developing solution is an alkaline aqueous
solution, deionized water (DIW) is in general used as the rinsing
liquid. When the developing solution is an organic developing
solution, on the other hand, isopropyl alcohol (IPA) or the like is
used as the rinsing liquid. The replacement liquid used in this
preferred embodiment is a liquid having the physical property of
having a solidification temperature lower than that of the rinsing
liquid. For example, when the rinsing liquid is DIW, IPA liquid is
used as the replacement liquid. In this preferred embodiment, DIW
is used as the rinsing liquid, and IPA liquid is used as the
replacement liquid.
[0029] A processing cup 161 is provided around the substrate holder
182 to collect a surplus of the alkaline aqueous solution that is
the developing solution supplied through the slit nozzle 105 onto
the substrate W, DIW that is the rinsing liquid supplied through
the discharge nozzle 125, and IPA liquid that is the replacement
liquid supplied through the discharge nozzle 125. These collected
chemical liquids are drained through drain outlets 160 to the
outside of the developer unit 10.
[0030] The dryer unit 30 according to the first preferred
embodiment as shown in FIG. 3 is a device for performing the drying
process on a substrate W subjected to the developing process in the
developer unit 10. The dryer unit 30 principally includes a dryer
chamber 31, a carbon dioxide supply mechanism 32, a first nitrogen
supply mechanism 33, a liquid nitrogen supply mechanism 34, a
second nitrogen supply mechanism 44, and a drain mechanism 35.
[0031] The dryer chamber (process chamber) 31 includes a
cylindrical upper member 313, and a lower member 314 provided with
a circular bottom wall 316. The upper member 313 and the lower
member 314 are brought into intimate contact with each other by a
sealing material 315. The upper member 313 is configured such that
a circular top wall 311 and a side wall 312 provided around the top
wall 311 are integrated together. The top surface of the bottom
wall 316, i.e. a surface of the lower member 314 that defines the
interior space of the dryer chamber 31, is inclined from the
horizontal. The upper member 313 and the lower member 314 are
movable relative to each other in a vertical direction, and come
into contact with or separate from each other to thereby allow the
dryer chamber 31 to close or open. After a substrate W is
transported into the dryer chamber 31 that is left open, the dryer
chamber 31 is closed. After the dryer chamber 31 is hermetically
closed, the substrate W is subjected to the process in the dryer
chamber 31.
[0032] A table 39 for placing a substrate W thereon is provided in
the dryer chamber 31. The substrate W is held in a substantially
horizontal position by being placed on the top surface of the table
39. The top surface of the table 39 has suction holes (not shown)
formed therein. The bottom surface of the substrate W placed on the
table 39 is attracted by suction to the table 39. This allows the
substrate W to be held on the table 39.
[0033] A support shaft 36 extends downwardly from the center of the
bottom surface of the table 39. The support shaft 36 is inserted
through the lower member 314, with a high-pressure seal rotation
introducing mechanism 37 provided therebetween. The high-pressure
seal rotation introducing mechanism 37 has a rotary shaft 371
connected to a rotating mechanism 372 of the dryer chamber 31.
Driving the rotating mechanism 372 rotates the substrate W with the
table 35 about the support shaft 36 at any rotational speed.
[0034] The carbon dioxide supply mechanism 32 includes a carbon
dioxide supply source 321, a valve 323, a pipe 322, and a first
inlet pipe 40. The first nitrogen supply mechanism 33 includes a
first nitrogen supply source 331, a valve 333, a pipe 332, and the
first inlet pipe 40. That is, the first inlet pipe 40 is used in
common for the carbon dioxide supply mechanism 32 and the first
nitrogen supply mechanism 33.
[0035] Carbon dioxide supplied from the carbon dioxide supply
source 321 is used as a material for removing remaining IPA liquid
from the substrate in accordance with principles to be described
later. Such a material used for the removal of liquid from a
substrate is in general referred to herein as a "sublimation
material."
[0036] The first inlet pipe 40 is provided in the top wall 311 of
the upper member 313 so as to extend through the top wall 311.
Specifically, the first inlet pipe 40 has a first end connected to
the interior space of the dryer chamber 31. The first inlet pipe 40
has a second end split into two: one is connected to the carbon
dioxide supply source 321, and the other is connected to the first
nitrogen supply source 331. In the first preferred embodiment, the
first inlet pipe 40 is used in common for the supply of carbon
dioxide and nitrogen to the dryer chamber 31. However, the dryer
unit 30 may be configured to include inlet pipes separately used
for the supply of carbon dioxide and nitrogen, respectively.
[0037] The valve 323 is provided in the pipe 322 connecting the
carbon dioxide supply source 321 and the first inlet pipe 40 to
each other, and the valve 333 is provided in the pipe 332
connecting the first nitrogen supply source 331 and the first inlet
pipe 40 to each other. Liquefied carbon dioxide is sealed in the
carbon dioxide supply source 321. When the valve 323 is opened with
the valve 333 closed, part of the liquefied carbon dioxide changes
to a gas, which in turn starts to come through the first inlet pipe
40 into the dryer chamber 31. Since the dryer chamber 31 is
hermetically closed, the pressure in the dryer chamber 31 reaches
an increased pressure higher than the pressure at which carbon
dioxide is condensed by the accumulation of the gaseous carbon
dioxide coming into the dryer chamber 31 soon after the gaseous
carbon dioxide starts to come into the dryer chamber 31, which will
be described later. Thus, carbon dioxide in a vapor phase is
supplied into the dryer chamber 31 in a very early stage, and
shortly thereafter liquefied carbon dioxide is supplied onto the
substrate W. In other words, the early stage of supply of carbon
dioxide is a stage in which the pressure in the dryer chamber 31 is
increased by carbon dioxide in a vapor phase, and the subsequent
stage is a stage in which carbon dioxide in a liquid phase is
supplied. In another step, when the valve 333 is opened with the
valve 323 closed, nitrogen is supplied into the dryer chamber 31.
Alternatively, nitrogen the temperature of which is raised by
mounting a heater to the pipe 332 may be supplied into the dryer
chamber 31.
[0038] The liquid nitrogen supply mechanism 34 includes a second
inlet pipe 341, a liquid nitrogen supply source 342, a pipe 345,
and a valve 343. The second inlet pipe 341 extends through the
bottom wall 316 of the lower member 314 to the interior of the
dryer chamber 31. The second inlet pipe 341 has a first end
provided within the dryer chamber 31 and positioned under the
bottom surface of the table 39. The second inlet pipe 341 has a
second end connected to the liquid nitrogen supply source 342. The
valve 343 is provided in the pipe 345 connecting the second inlet
pipe 341 and the liquid nitrogen supply source 342 to each other.
Liquid nitrogen is supplied through the second inlet pipe 341 into
the dryer chamber 31 by opening the valve 343.
[0039] The second nitrogen supply mechanism 44 is further mounted
to the lower member 314. The second nitrogen supply mechanism 44
includes a third inlet pipe 441, a second nitrogen supply source
442, a heater 444, a valve 443, and a pipe 445.
[0040] Like the second inlet pipe 341, the third inlet pipe 441
extends through the lower member 314 to the interior of the dryer
chamber 31. The third inlet pipe 441 has a first end positioned
under the bottom surface of the table 39, like the first end of the
second inlet pipe 341. The third inlet pipe 441 has a second end
connected to the second nitrogen supply source 442. The heater 444
and the valve 443, which are arranged in ascending order of
distance from the second nitrogen supply source 442, are provided
in the pipe 445 connecting the third inlet pipe 441 and the second
nitrogen supply source 442 to each other. Nitrogen supplied from
the second nitrogen supply source 442 is raised in temperature by
the heater 444, and is supplied at the raised temperature into the
dryer chamber 31 by opening the valve 443. Alternatively, a single
nitrogen supply source may be provided for a dual purpose to serve
as both the first nitrogen supply source 331 and the second
nitrogen supply source 442.
[0041] A fluid dispersing mechanism 38 is provided in an upper
portion of the interior of the dryer chamber 31. The fluid
dispersing mechanism 38 includes a round disk-shaped blocking plate
381 fitted in the dryer chamber 31 and having a large number of
communication holes 382 extending vertically through the blocking
plate 381.
[0042] The drain mechanism 35 includes a plurality of drain pipes
351, a pipe 354, and a valve 353. The drain pipes 351 are provided
in a lowermost position of the inclined surface of the lower member
314. Thus, the liquid flowing down from over the substrate W flows
along the inclined surface of the lower member 314 into the drain
pipes 351, and is then drained through the drain pipes 351 to the
outside of the dryer chamber 31. The gas within the dryer chamber
31 is also discharged through the drain pipes 351 to the outside of
the dryer chamber 31.
[0043] A mixture of liquid and gas discharged from the dryer
chamber 31 through the drain pipes 351 is decreased in pressure by
passing through the valve 353, and is then separated into liquid
and gas in a separating tank 355. After the separation, the gas and
liquid are sent to respective predetermined devices for reuse or
reprocessing purposes.
[0044] A temperature measuring part and a pressure measuring part
both not shown are provided within the dryer chamber 31, and are
able to measure the temperature and pressure in the dryer chamber
31. A controller 50 adjusts the degree of opening of the valves
323, 333, 343, 443 and 353 in accordance with the temperature and
pressure measured with the temperature measuring part and pressure
measuring part to adjust the temperature and pressure in the dryer
chamber 31. The controller 50 is similar in hardware construction
to typical computers.
[0045] Next, the principle of processing and a specific procedure
according to the first preferred embodiment of the present
invention will be described with reference to a phase diagram of
carbon dioxide shown in FIG. 4, a flow diagram shown in FIG. 5, and
FIGS. 6 to 12. In FIGS. 6 to 12, the construction of the dryer unit
30 is shown schematically for the purpose of facilitating the
understanding of the procedure. In fact, the dryer unit 30 shown in
FIG. 3 is used for the processing. The ordinate of FIG. 4 is
indicated to have a logarithmic scale.
[0046] One of the substrates W placed on the substrate station 5
and each having an exposed resist layer is taken out and
transported to the developer unit 10 by the transfer unit 20. An
alkaline aqueous solution pd serving as the developing solution is
supplied to the transported substrate W, whereby the developing
process is performed. After a lapse of a predetermined period of
time, the supply of the alkaline aqueous solution pd serving as the
developing solution is stopped. Then, the valve 111 is opened to
supply DIW (dw) serving as the rinsing liquid to the surface of the
substrate W, as shown in FIG. 6, for the purpose of removing the
alkaline aqueous solution pd remaining on the surface of the
substrate W.
[0047] During the supply of the DIW (dw), the substrate W is
rotating. For this reason, the DIW (dw) supplied to the surface of
the substrate W is subjected to centrifugal force to flow over the
substrate W toward the outer periphery of the substrate W. Thus,
while rinsing the alkaline aqueous solution pd out of the surface
of the substrate W, the DIW (dw) splashes with the alkaline aqueous
solution pd to the processing cup 161, and is drained through the
drain outlets 160. In this manner, the supply of the DIW (dw)
serving as the rinsing liquid continues until a lapse of a
predetermined period of time, so that the alkaline aqueous solution
pd serving as the developing solution and held in the form of a
puddle on the surface of the substrate W is replaced with the DIW
(dw) (in Step S1).
[0048] Subsequently, the valve 111 is closed, and the valve 121 is
opened to supply IPA liquid ds serving as the replacement liquid
through the discharge nozzle 125 onto the substrate W (with
reference to FIG. 7). As in the case of the supply of the DIW (dw),
the IPA liquid ds rinses the DIW (dw) out of the surface of the
substrate W while flowing over the substrate W toward the outer
periphery of the substrate W because the substrate W is rotating.
Thus, the DIW (dw) remaining on the substrate W is completely
replaced with the IPA liquid ds (in Step S2).
[0049] After a lapse of a predetermined period of time, the
rotation of the substrate W is stopped. Then, the transfer unit 20
takes out the substrate W, and transports the substrate W to the
dryer unit 30 (in Step S3). During the transport of the substrate
W, the surface of the substrate W is fully covered with the IPA
liquid ds serving as the replacement liquid. The dryer chamber 31
of the dryer unit 30 is left open, and the transfer unit 20 places
the substrate W onto the table 39.
[0050] After the substrate W is placed on the table 39, the upper
member 313 and the lower member 314 are fitted together to
hermetically close the dryer chamber 31 because all of the valves
323, 333, 343, 443, and 353 are closed. The interior atmosphere
(environment) of the dryer chamber 31 in this stage is at normal
temperature and pressure.
[0051] After the dryer chamber 31 is hermetically closed, the valve
323 is opened. This causes carbon dioxide vaporized upon emission
from the carbon dioxide supply source 321, i.e. gaseous carbon
dioxide gc, to come through the first inlet pipe 40 into the dryer
chamber 31. As the gaseous carbon dioxide gc is supplied, the valve
353 is opened. This causes air in the dryer chamber 31 to exit the
dryer chamber 31 through the valve 353, thereby replacing the air
in the dryer chamber 31 with the gaseous carbon dioxide gc. After a
lapse of a predetermined period of time, the valve 353 is closed,
so that the dryer chamber 31 is hermetically closed. The pressure
in the dryer chamber 31 increases because the supply of the gaseous
carbon dioxide gc into the dryer chamber 31 continues (in Step S4).
As the gaseous carbon dioxide gc is supplied into the dryer chamber
31 in this manner, the temperature and pressure in the dryer
chamber 31 become higher than a temperature of -56.6.degree. C. and
a pressure of 5.1 atmospheres (0.517 MPa) corresponding to the
triple point of carbon dioxide. When the pressure in the dryer
chamber 31 exceeds a predetermined pressure, the gaseous carbon
dioxide gc changes into liquid within the dryer chamber 31. The
predetermined pressure is a pressure determined based on a vapor
pressure curve representing a relationship between pressure and
temperature at which a liquid phase and a vapor phase coexist at
the temperature in the dryer chamber 31.
[0052] That is, carbon dioxide supplied from the carbon dioxide
supply source 321 into the dryer chamber 31 is in the form of a gas
at the time of the start of supply of carbon dioxide. Thereafter,
as the supply of carbon dioxide continues, the pressure in the
dryer chamber 31 increases. When the pressure in the dryer chamber
31 exceeds 5.1 atmospheres to reach a predetermined condensation
pressure, carbon dioxide changes into a liquid state. Subsequently,
carbon dioxide in such a liquid state is supplied to the substrate
W.
[0053] Thus, carbon dioxide is supplied substantially in a
liquefied state (liquid carbon dioxide lc) to the dryer chamber 31,
as shown in FIG. 8, except for a temporary gaseous state in an
early stage. A liquid layer of carbon dioxide is formed on the
surface of the substrate W.
[0054] The controller 50 opens the valve 353, and drives the
rotating mechanism 372 to rotate the table 39, when carbon dioxide
exists in liquid form, that is, in a non-supercritical state where
the following conditions 1) and 2) are maintained.
[0055] 1) The temperature and pressure are higher than a
temperature of -56.6.degree. C. and a pressure of 5.1 atmospheres
which define the triple point of carbon dioxide.
[0056] 2) The temperature and pressure, which are lower than a
temperature of 31.1.degree. C. and a pressure of 72.8 atmospheres
(7.38 MPa) respectively, do not reach a supercritical state.
[0057] Thus, the liquid carbon dioxide lc and the IPA liquid ds
serving as the replacement liquid both present on the surface of
the substrate W flow toward the outer periphery of the substrate W
by centrifugal force resulting from the rotation of the substrate
W. Then, the IPA liquid ds and the liquid carbon dioxide lc flow
down onto the bottom surface of the dryer chamber 31 (or the upper
surface of the bottom wall 316), and are drained through the drain
pipes 351 to the outside of the dryer chamber 31. Rotating the
substrate W achieves efficient replacement of the IPA liquid ds
with the liquid carbon dioxide lc.
[0058] The liquid carbon dioxide lc supplied through the first
inlet pipe 40 into the dryer chamber 31 is supplied uniformly onto
the surface of the substrate W by the fluid dispersing mechanism
38. The liquid carbon dioxide lc easily enters gaps in the pattern
formed on the surface of the substrate W because the surface
tension of the liquid carbon dioxide lc is less than that of the
IPA liquid ds. Such supply of the liquid carbon dioxide is
continues until a lapse of a predetermined period of time so that
the IPA liquid ds on the surface of the substrate W is completely
replaced with the liquid carbon dioxide lc.
[0059] After a lapse of the predetermined period of time, the valve
323 and the valve 353 are closed to stop the supply of carbon
dioxide into the dryer chamber 31. The non-supercritical state is
maintained because the dryer chamber 31 is hermetically closed.
[0060] Subsequently, the valve 343 is opened to supply liquid
nitrogen ln into the dryer chamber 31 (in Step S5 with reference to
FIG. 9). At this time, the valve 353 is opened while the degree of
opening of the valve 353 is adjusted so that the pressure in the
dryer chamber 31 remains constant.
[0061] The liquid nitrogen In supplied through the second inlet
pipe 341 is blown directly onto the bottom surface of the table 39.
This rapidly decreases the temperature of the table 39 to cool down
the substrate W held on the table 39. In other words, the table 39
cools down the substrate W using the entire surface thereof
contacting the substrate W, as does a cool plate.
[0062] The pressure is held constant at 5.1 atmospheres or higher,
and the temperature decreases. This causes the liquid carbon
dioxide lc on the surface of the substrate W to solidify (with
reference to FIG. 10). Specifically, with reference to FIG. 4, the
temperature and pressure change along a solid line connecting a
point indicating a state (A) and a point indicating a state (B),
and a phase transition from the liquid carbon dioxide lc to solid
carbon dioxide sc occurs when the temperature in the dryer chamber
31 decreases to below a predetermined temperature. The
predetermined temperature is a temperature determined based on a
melting curve representing a relationship between pressure and
temperature at which a liquid phase and a solid phase coexist at
the pressure in the dryer chamber 31. In this manner, liquid
nitrogen serving as a refrigerant is supplied directly into the
dryer chamber 31 to solidify carbon dioxide according to the first
preferred embodiment. Thus, heat is removed from the substrate W
through the surface of the table 39 contacting the substrate W.
This efficiently cools down the substrate W to solidify the liquid
carbon dioxide lc. In the first preferred embodiment, the part for
supplying liquid nitrogen corresponds to a solidifying part for
solidifying carbon dioxide. However, the solidifying part may use a
refrigerant in the form of a gas and be configured to blow the
refrigerant gas directly onto the surface of the substrate W
without using the table 39. The temperature of the supplied
refrigerant, whether in liquid form or in gaseous form, is required
only to be lower than the solidification temperature of carbon
dioxide at the pressure in the dryer chamber 31.
[0063] In this manner, the DIW (dw) serving as the rinsing liquid
and having a solidification temperature much higher than that of
carbon dioxide is replaced with the replacement liquid such as the
IPA liquid ds having a solidification temperature lower than that
of the DIW (dw) for the purpose of solidifying carbon dioxide
according to the first preferred embodiment. This prevents the
rinsing liquid, e.g. the DIW (dw), remaining on the surface of the
substrate W from solidifying before carbon dioxide solidifies.
Also, when the solidification temperature of the replacement
liquid, e.g. the IPA liquid ds, is not higher than -56.6.degree. C.
that is the solidification temperature of carbon dioxide, the
replacement liquid is prevented from solidifying before carbon
dioxide solidifies.
[0064] After the surface of the substrate W is covered with the
solid carbon dioxide sc in this manner, the valve 343 is closed,
and the valve 353 is fully opened. This causes the pressure in the
dryer chamber 31 to fall to a pressure of one atmosphere that is
atmospheric pressure (in Step S6). At this time, the temperature in
the dryer chamber 31 is further lowered because of adiabatic
expansion. Specifically, the temperature and pressure change along
a solid line connecting the point indicating the state (B) and a
point indicating a state (C) with reference to FIG. 4.
[0065] When the pressure in the dryer chamber 31 reaches
atmospheric pressure, the valve 333 is opened to introduce gaseous
nitrogen ig at room temperature through the first inlet pipe 40
into the dryer chamber 31 (in Step S7 with reference to FIG. 11).
The temperature in the dryer chamber 31 is lower than the
temperature of the gaseous nitrogen ig, and the valve 353 is left
open. For this reason, the supply of the gaseous nitrogen ig into
the dryer chamber 31 raises the temperature of the atmosphere in
the dryer chamber 31, with the pressure in the dryer chamber 31
held at atmospheric pressure. Specifically, the temperature changes
along a solid line connecting the point indicating the state (C)
and a point indicating a state (D) with reference to FIG. 4. At
this time, when the temperature in the dryer chamber 31 reaches
-78.5.degree. C. or higher, the solid carbon dioxide sc sublimates
to make a phase transition to the gaseous carbon dioxide gc. The
temperature at which the sublimation starts is a temperature
determined based on a sublimation curve representing a relationship
between pressure and temperature at which a solid phase and a vapor
phase coexist at the pressure in the dryer chamber 31. There
remains no liquid on the surface of the substrate W because the
gaseous carbon dioxide gc is diffused from the surface of the
substrate W into the atmosphere.
[0066] In this manner, the liquid carbon dioxide lc penetrating the
gaps in the pattern of the substrate W is changed to a solid state
by cooling, and then makes a phase transition to a gaseous state.
Thus, carbon dioxide does not change to a liquid state before
changing to the gaseous state. This prevents the production of
capillary force peculiar to liquid to prevent the collapse of
protruding portions of the pattern formed on the substrate W. As
compared with a drying technique using a supercritical fluid which
does not change to a liquid state before changing to a gaseous
state in a similar manner, the drying process according to the
first preferred embodiment is performed in a low-pressure
atmosphere (environment). Thus, the first preferred embodiment
reduces apparatus costs, as compared with facilities for achieving
a supercritical state which requires a high-pressure environment.
Additionally, the first preferred embodiment reduces processing
time because there is no need to wait until a high-pressure
environment is provided.
[0067] When the temperature of the substrate W is low, there is a
difference in temperature between the substrate W and an atmosphere
outside the dryer chamber 31. This gives rise to apprehension that
dew condensation occurs on the surface of the substrate W when the
substrate W is transported out of the dryer chamber 31 for a
subsequent step. To prevent this, the valve 443 is opened to blow
gaseous nitrogen hg warmed by the heater 444 through the third
inlet pipe 441 directly onto the bottom surface of the table 39
(with reference to FIG. 12). These mechanisms for supplying the
warmed gaseous nitrogen hg function as a temperature adjusting
part. Heat transferred from the gaseous nitrogen hg through the
table 39 to the substrate W raises the temperature of the substrate
W to prevent dew condensation from occurring on the surface of the
substrate W.
[0068] As described hereinabove, for the purpose of removing liquid
from the surface of the substrate W, the dryer unit 30 according to
the first preferred embodiment temporarily covers the surface of
the substrate W with the liquid carbon dioxide lc, and then
decreases the temperature in the dryer chamber 31, thereby causing
the liquid carbon dioxide lc to make a phase transition to the
solid carbon dioxide sc. Then, the dryer unit 30 releases the
pressure in the dryer chamber 31 to an atmospheric environment to
decrease the pressure in the dryer chamber 31 to atmospheric
pressure (a pressure of one atmosphere), and thereafter increases
the temperature, thereby using the sublimation of the solid carbon
dioxide sc to the gaseous carbon dioxide gc. Since the sublimation
reaction from the solid state to the gaseous state is used, the
material on the surface of the substrate W is vaporized without
entering the liquid state. This prevents capillary force from
acting on the gaps in the pattern of the substrate W to prevent the
collapse of the pattern formed on the surface of the substrate
W.
[0069] Also, as compared with a drying technique using a
supercritical fluid which produces a similar effect, the drying
process according to the first preferred embodiment may be
performed in a low-pressure environment. Thus, the first preferred
embodiment eliminates the need for facilities for achieving a
high-pressure environment to reduces apparatus costs.
[0070] Additionally, the first preferred embodiment reduces
processing time because there is no need to wait until a
high-pressure state in which a supercritical state is reached is
provided.
Second Preferred Embodiment
[0071] Next, a dryer unit 30b according to a second preferred
embodiment of the present invention will be described with
reference to FIGS. 13 and 14. Like reference numerals and
characters are used in the second preferred embodiment to designate
components identical with those of the first preferred embodiment
described above, and only differences from the dryer unit 30 of the
first preferred embodiment will be described. The sublimation
material for use in the second preferred embodiment is carbon
dioxide, as in the first preferred embodiment.
[0072] The liquid carbon dioxide lc covering the surface of the
substrate W placed in the dryer chamber 31 according to the first
preferred embodiment is solidified by cooling. According to the
second preferred embodiment, the liquid carbon dioxide lc is
solidified by decreasing the pressure in the dryer chamber 31 in an
adiabatic state.
[0073] As shown in FIG. 13, the dryer unit 30b according to the
second preferred embodiment is configured such that the liquid
nitrogen supply mechanism 34 provided in the first preferred
embodiment is dispensed with. The solidifying part in the second
preferred embodiment is the drain mechanism 35.
[0074] FIG. 14 is a flow diagram showing the procedure according to
the second preferred embodiment of the present invention. As in the
first preferred embodiment, the surface of the substrate W is
covered with the liquid carbon dioxide lc. In the second preferred
embodiment, the valve 353 is opened (in Step S15) after a lapse of
a predetermined period of time since the covering of the surface of
the substrate W with the liquid carbon dioxide lc. This decreases
the pressure in the dryer chamber 31 to adiabatically expand the
atmosphere in the dryer chamber 31, thereby decreasing the
temperature. Thus, the temperature of the liquid carbon dioxide lc
covering the surface of the substrate W decreases, which in turn
solidifies the liquid carbon dioxide lc. In other words, the
temperature and pressure change as represented by a solid line
connecting the point indicating the state (A) and the point
indicating the state (C) with reference to FIG. 4, to thereby cause
carbon dioxide to make a phase transition from the liquid state to
the solid state. At this time, the degree of opening of the valve
353 is adjusted so that the temperature and pressure do not make a
phase transition from the liquid carbon dioxide lc to the gaseous
carbon dioxide gc, i.e., so that the transition to the state (C) is
made through a path lying above the triple point in the phase
diagram of FIG. 4. The pressure in the dryer chamber 31 is finally
decreased to atmospheric pressure, i.e., a pressure of one
atmosphere. Then, gaseous nitrogen is supplied into the dryer
chamber 31 (in Step S16), as in the first preferred embodiment, to
sublimate the solid carbon dioxide sc to the gaseous carbon dioxide
gc, thereby removing liquid (IPA liquid) from the surface of the
substrate W. In other words, the temperature changes along the
solid line connecting the point indicating the state (C) and the
point indicating the state (D).
[0075] For convenience of illustration, the state (C) in the first
preferred embodiment and the state (C) in the second preferred
embodiment are indicated by the same point with reference to FIG.
4. However, the state (C) in the first preferred embodiment and the
state (C) in the second preferred embodiment may be indicated by
different points so far as these points lie on the line indicating
one atmosphere in a region of the solid phase.
[0076] In this manner, the liquid nitrogen supply mechanism 34 is
not required in the second preferred embodiment. Thus, the second
preferred embodiment is capable of removing liquid from the surface
of the substrate W by using simplified facilities, as compared with
the first preferred embodiment. Additionally, the second preferred
embodiment facilitates the control of the valve for solidifying
carbon dioxide because it is necessary only to adjust the degree of
opening of the valve 353.
[0077] As described hereinabove, the dryer unit 30b according to
the second preferred embodiment performs the processes of covering
the surface of the substrate W with the liquid carbon dioxide lc
and decreasing the pressure in the dryer chamber 31, thereby
causing the phase transition from the liquid carbon dioxide lc to
the solid carbon dioxide sc. The second preferred embodiment
produces effects similar to those of the first preferred
embodiment, and also simplifies the construction and control of the
apparatus.
[0078] <Modifications>
[0079] The present invention is not limited to the first and second
preferred embodiments described above. For example, the dryer units
30 and 30b are used for the drying process subsequent to the
developing process in the first and second preferred embodiments
described above. The present invention, however, is not limited to
such forms. When there arises a need to dry the surface of the
substrate W subjected to a wet process, the substrate processing
technique according to the present invention may be used.
[0080] An arrangement as a compromise between the first and second
preferred embodiments may be used in which both of the temperature
and pressure in the dryer chamber 31 (in general, a process
chamber) are changed (specifically, using both cooling and pressure
decrease) to sublimate solidified carbon dioxide, thereby removing
carbon dioxide from the surface of the substrate.
[0081] Although the point indicating the state (C) lies on the line
indicating one atmosphere, the state (C) need not correspond to one
atmosphere so far as the state (C) corresponds to a pressure lower
than that at the triple point and lies in a solid phase region.
However, it is more preferable that the point indicating the state
(C) lies on the line indicating one atmosphere because the pressure
is easily controlled.
[0082] In the first and second preferred embodiments, carbon
dioxide is used as the sublimation material. However, other
materials which have a triple point (the temperature and pressure
at which solid, liquid and vapor phases coexist) with a pressure of
one atmosphere or higher may be used as the sublimation material.
Also, other inert gases may be used in place of nitrogen for supply
to the dryer chamber 31.
[0083] Although the second nitrogen supply mechanism 44 is provided
in the first and second preferred embodiments, the present
invention is not limited to such an arrangement. The second
nitrogen supply mechanism 44 need not necessarily be provided. The
first nitrogen supply mechanism 33 may be provided with a heater
and configured for dual purpose so that supply of warmed nitrogen
and supply of room-temperature nitrogen are selected. With such an
arrangement, the first nitrogen supply mechanism 33 has the
function of the second nitrogen supply mechanism 44.
[0084] While the invention has been described in detail, the
foregoing description is in all aspects illustrative and not
restrictive. It is understood that numerous other modifications and
variations can be devised without departing from the scope of the
invention.
* * * * *