U.S. patent application number 11/396677 was filed with the patent office on 2006-08-03 for resist application method and device.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Takehiro Sato.
Application Number | 20060172441 11/396677 |
Document ID | / |
Family ID | 31986493 |
Filed Date | 2006-08-03 |
United States Patent
Application |
20060172441 |
Kind Code |
A1 |
Sato; Takehiro |
August 3, 2006 |
Resist application method and device
Abstract
The resist application method comprises the steps of: thermal
processing for evaporating water from the surface of a wafer 10;
making the surface of the wafer 10 hydrophobic with a hydrophobic
processing material; and applying a resist onto the wafer 10, and
the step of thermal processing to the step of making the surface of
the wafer 10 hydrophobic are performed in a dehumidified
atmosphere.
Inventors: |
Sato; Takehiro;
(Kasugai-shi, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki
JP
|
Family ID: |
31986493 |
Appl. No.: |
11/396677 |
Filed: |
April 4, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10652314 |
Sep 2, 2003 |
7053008 |
|
|
11396677 |
Apr 4, 2006 |
|
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|
Current U.S.
Class: |
438/5 ;
257/E21.259; 438/780; 438/781; 438/782 |
Current CPC
Class: |
G03F 7/16 20130101; H01L
21/312 20130101; G03F 7/168 20130101 |
Class at
Publication: |
438/005 ;
438/780; 438/782; 438/781 |
International
Class: |
H01L 21/00 20060101
H01L021/00; H01L 21/31 20060101 H01L021/31 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2002 |
JP |
2002-264105 |
Claims
1. A resist application device comprising: a thermal processing
unit for performing thermal processing to evaporate water from the
surface of a substrate in a dehumidified atmosphere; a hydrophobic
processing unit for making the substrate surface hydrophobic with a
hydrophobic processing material, keeping the dehumidified
atmosphere; and a resist application unit for applying a resist
onto the substrate.
2. A resist application device according to claim 1, wherein the
hydrophobic processing unit further comprises a heating means.
Description
CROSS-REFERENCE TO RERATED APPLICATION
[0001] This Application is a divisional of application Ser. No.
10/652,314 filed on Sep. 2, 2003. This application is based upon
and claims priority of Japanese Patent Application No. 2002-264105,
filed on Sep. 10, 2002, the contents being incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a resist application method
and device for applying a resist to a substrate after the surface
of the substrate has been subjected to hydrophobic processing with
hexamethyldisilazane.
[0003] Conventionally in fabricating semiconductor devices, when a
resist is applied to a substrate, such as a wafer or others,
generally the surface of the substrate is made hydrophobic with
hexamehtyldisilazane (HMDS) as pre-processing. HMDS is a good
silylation agent, and easily silylates hydroxyl groups on the
surface of the silicon substrate, etc. to make the substrate
surface hydrophobic.
[0004] The hydrophobic processing with HMDS enhances adhesion
between the resist film and the substrate surface, whereby in the
following patterning, the occurrence of unsatisfactory pattern
transfer, etc. can be suppressed.
[0005] The hydrophobic processing of a wafer surface with HMDS is
made as follows.
[0006] First, HMDS, which is liquid at the room temperature, is
bubbled with nitrogen gas while being heated. The nitrogen gas
containing the HMDS produced by the bubbling is injected to a
substrate on a hot plate whose temperature is controlled within a
range of 30-100.degree. C. in a tightly closed processing
chamber.
[0007] Then, usually the substrate is cooled at the room
temperature, and a certain amount of resist is dropped onto the
rotating substrate in an environment whose temperature and humidity
are controlled, whereby the resist is applied to the substrate. The
resist applied to the substrate is dried and solidified by heat
processing, and a resist film is formed. The resist film thus
formed on the substrate is subjected to an exposure step to be
patterned into a required shape, as of a wiring pattern or
others.
[0008] In such resist applying step, for better adhesion between
the resist and the substrate, various methods have been so far
proposed.
[0009] For example, Japanese Published Patent Application No. Hei
04-99310 (1992) (pp. 2-3, FIGS. 1 and 2) discloses the method that
prior to the HMDS processing, heated nitrogen gas is injected to a
substrate to thereby remove water from the substrate surface.
[0010] Japanese Published Patent Application No. Hei 05-315233
(1993) (Paragraphs 0021-0022, FIG. 2) and Japanese Published Patent
Application No. Hei 06-302507 (1994) (Paragraphs 0014-0015, FIG. 1)
disclose the method that prior to the HMDS processing, water on the
surface of a substrate is removed by reduced pressure
processing.
[0011] Japanese Examined Patent Application Publication No. Sho
62-35264 (1987) (pp. 2-3, FIGS. 1-3) discloses the method that the
processing from the HMDS processing to the application of the
resist is performed in a nitrogen atmosphere.
[0012] Japanese Published Patent Application No. Hei 10-256139
(1998) (Paragraphs 0026-0033, FIG. 1) discloses the method that dry
air is caused to flow in a coater cup where a resist is applied,
for the purpose of removing humidity around the coater cup and
recycling the resist.
[0013] Japanese Published Patent Application No. Hei 05-234866
(1993) discloses the method that a plasma processing unit and an
HMDS processing unit are disposed in one and the same chamber to
thereby remove water on substrate surfaces by plasma
processing.
[0014] The internal unit of the resist application device, where
the above-described resist application is performed is fed with an
atmosphere in a clean room through a HEPA (High Efficiency
Particulate Air) filter. Recently, in applying a chemically
amplified resist used for mass production, an atmosphere in a clean
room is fed into the internal unit through a chemical filter so as
to remove basic substances, such as ammonia, etc., which inactivate
the resist.
[0015] However, in the conventional resist application device, the
humidity of an atmosphere in a clean room, which is to be fed into
the internal unit, has not been especially controlled.
[0016] Accordingly, HMDS used for the hydrophobic processing before
the resist application reacts with water contained in the fed
atmosphere of the clean room to be decomposed into siloxane-group
substances, such as trimethylsilanol. Resultantly, it is often that
the adhesion between the resist and substances is lowered.
[0017] For the prevention of such reaction of HMDS with water in
the atmosphere, as described above in connection with the prior
art, a resist application device which controls the water content
of the atmosphere in the HMDS processing unit is also so far known.
However, the water contents of the atmosphere before and after the
HMDS processing have not been controlled. For example, in cooling a
substrate after the baking prior to the HMDS processing, in
transferring the substrate or in cooling the substrate after the
HMDS processing, the water contents of the atmosphere have not been
especially controlled. Accordingly, re-adsorption of water to the
substrate surface, etc. takes place. It cannot be said that the
humidity control in the serial processing is sufficient.
[0018] For reducing the undesirable influence by the water before
and after the HMDS processing, the method as exemplified by the
prior art disclosed in Japanese Examined Patent Application
Publication No. Sho 62-35264 (1987) (pp. 2-3, FIGS. 1-3), in which
the serial processing from the HMDS processing to the resist
application is performed in an atmosphere of nitrogen gas, is
known. However, the atmosphere in which the resist application is
performed has also the water content decreased, which will make it
difficult to form the resist film in a uniform film thickness. Also
in consideration of the amount of nitrogen gas required to
completely replace the processing chamber and the time required for
the replacement, etc., it will be difficult to efficiently apply
the resist from the viewpoint of cost and time.
[0019] The undesirable influence by the hydrolysis of the HMDS used
in the hydrophobic processing on the substrate surface due to the
water is not limited to the reduced adhesion between the resist and
the substrate as will be described below.
[0020] Siloxane-group substances produced by the hydrolysis of the
HMDS due to the water cause reactions on the surfaces of especially
amorphous silicon, etc. Resultantly, after the resist has been
patterned, foreign substances are often produced on the surfaces of
amorphous silicon, etc. FIG. 4 is a picture of the foreign
substance. The foreign substance was observed by a scanning
electronic microscope.
[0021] Such foreign substances are sufficiently able to mask the
etching, and are one factor for causing defects of the pattern as
etched, which has much affected yields of the products.
SUMMARY OF THE INVENTION
[0022] An object of the present invention is to provide a resist
application method and device which can suppress the production of
foreign substances on substrate surfaces.
[0023] According to one aspect of the present invention, there is
provided a resist application method comprising the steps of:
thermal processing for evaporating water from the surface of a
substrate; making the surface of the substrate hydrophobic with a
hydrophobic processing material; and applying a resist onto the
substrate, the step of thermal processing to the step of making the
substrate surface hydrophobic being performed in a dehumidified
atmosphere.
[0024] According to another aspect of the present invention, there
is provided a resist application method comprising the steps of:
thermal processing for evaporating water from the surface of a
substrate; making the surface of the substrate hydrophobic with a
hydrophobic processing material; and applying a resist onto the
substrate, in the step of thermal processing, a temperature of the
substrate being above 150.degree. C. including 150.degree. C.
[0025] According to further another aspect of the present
invention, there is provided a resist application device
comprising: a thermal processing unit for performing thermal
processing to evaporate water from the surface of a substrate in a
dehumidified atmosphere; a hydrophobic processing unit for making
the substrate surface hydrophobic with a hydrophobic processing
material, keeping the dehumidified atmosphere; and a resist
application unit for applying a resist onto the substrate.
[0026] As described above, the resist application method according
to the present invention comprises the steps of: thermal processing
for evaporating water from the surface of a substrate; making the
surface of the substrate hydrophobic with a hydrophobic processing
material; and applying a resist onto the substrate, and the step of
the thermal processing to the step of making the substrate surface
hydrophobic are performed in a dehumidified atmosphere, whereby the
hydrolysis of the hydrophobic processing material to be used in the
hydrophobic processing of the substrate surface can be suppressed,
and the generation of foreign substances on the substrate surface
can be suppressed. The substrate surface is made hydrophobic with
the hydrophobic processing material while the substrate is being
heated, whereby the adhesion between the substrate and the resist
can be improved. Thus, the generation of foreign substances on the
substrate surface can be suppressed, and the adhesion between the
substrate and the resist is improved, whereby semiconductor devices
of high quality can be fabricated with high yields.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is an upper side view of the resist application
device according to one embodiment of the present invention, which
shows a structure thereof.
[0028] FIG. 2 is a flow chart of the steps of the resist
application method according to one embodiment of the present
invention.
[0029] FIGS. 3A and 3A are views of evaluation results.
[0030] FIG. 4 is a picture of a foreign substance.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The resist application method and device according to one
embodiment of the present invention will be explained with
reference to FIGS. 1 and 2. FIG. 1 is an upper side view of the
resist application device according to the present embodiment,
which shows a structure thereof. FIG. 2 is a flow chart of the
resist application method according to the present embodiment.
[0032] [1] The Resist Application Device
[0033] The resist application device according to the present
embodiment will be explained with reference to FIG. 1.
[0034] The resist application device according to the present
embodiment includes a housing unit 12 which houses a wafer 10 to be
coated with a resist; a first thermal processing unit 14 where the
wafer 10 is subjected to thermal processing before HMDS processing;
a first cooling processing unit 16 where the wafer 10 which has
been thermally processed by the first thermal processing unit 14 is
cooled; an HMDS processing unit 18 where the surface of the wafer
10 is subjected to hydrophobic processing with HMDS; a second
cooling processing unit 20 where the wafer 10 which has been
subjected to the hydrophobic processing with HMDS is cooled; and a
second thermal processing unit 22 where the wafer which has been
coated with the resist is thermally processed arranged adjacent to
each other in the stated order.
[0035] An arm moving region 26 where a carrying arm 24 for carrying
a wafer 10 to the respective processing units is provided on one
sides of the first thermal processing unit 14, the first cooling
processing unit 16, the HMDS processing unit 18, the second cooling
processing unit 20 and the second thermal processing unit 22. A
resist application unit 28 where a resist is applied to the wafer
which has been cooled after the HMDS processing is provided in the
region opposed to the respective processing units across the arm
moving region 26.
[0036] Partition walls 30 for isolating the respective processing
units from each other are provided between the respective
processing units and their adjacent one. The respective processing
units are connected respectively to independent exhaust systems
(not shown). Openings (not shown) for letting in and out the wafer
10 by the carrying arm 24 are provided in the partition walls 30 of
the respective processing units opposed to the arm moving region
26. The respective processing units are isolated chambers isolated
from an atmosphere in a clean room where the resist application
device is usually positioned. When the device is operated,
dehumidified air, i.e., clean dry air is fed into the first thermal
processing unit 14, the first cooling processing unit 16, the HMDS
processing unit 18, the second cooling processing unit 20 and the
arm moving region 26.
[0037] Wafers 10 to be coated with a resist are housed in the
housing unit 12, mounted on a carrier 32. The carrying arm 24 is
moved in the housing unit 12 and the arm moving region 26 to take
the wafer 10 off the carrier 32 and carry the wafer 10 to the
respective processing units.
[0038] A hot plate 34 whose temperature can be controlled in the
range of, e.g., 40-250.degree. C. is provided in the first thermal
processing unit 14. When the wafer 10 is thermally processed, the
wafer 10 is mounted on the hot plate 34.
[0039] A cooling plate 36 inside which water whose temperature
controlled by, e.g., a thermostat or others is circulated is
disposed in the first cooling processing unit 16. When the wafer 10
is subjected to the cooling processing, the wafer 10 is mounted on
the cooling plate 36.
[0040] A hot plate 38 whose temperature can be controlled in the
rage of, e.g., 40-250.degree. C. is disposed in the HMDS processing
unit 18. When the wafer 10 is subjected to the HMDS processing, the
wafer 10 is mounted on the hot plate 38. HMDS which has been
bubbled with nitrogen gas and vaporized in a storage tank (not
shown) disposed outside is carried on the nitrogen gas as a carrier
gas into the HMDS processing unit 18.
[0041] In the second cooling processing unit 20, a cooling plate 40
inside which water having the temperature controlled by, e.g., a
thermostat or others is circulated is disposed. When the wafer 10
is subjected to the cooling processing, the wafer 10 is mounted on
the cooling plate 10.
[0042] In the second thermal processing unit 22, as in the first
thermal processing unit 14, a hot plate 42 whose temperature can be
controlled in the range of, e.g., 40-250.degree. C. is provided.
When the wafer 10 is subjected to the thermal processing, the wafer
10 is mounted on the hot plate 42.
[0043] In the resist application unit 28, there are disposed an
application cup 44 in which a resist is applied, and a wafer chuck
46 which is disposed in the application cup 44 and is rotated in
horizontal plane, holding the wafer 10. A nozzle (not shown) for
dropping a resist onto the wafer 10 held by the wafer chuck 46 is
disposed above the wafer chuck 46.
[0044] As described above, the resist application device according
to the present embodiment is characterized mainly by the first
thermal processing unit 14 which thermally processes a wafer 10
before the wafer 10 is subjected to the HMDS processing. The wafer
10 is heated by the first thermally processing unit 14 before the
wafer 10 is subjected to the HMDS processing, whereby water on the
surface of the wafer 10 is removed, and the hydrolysis of the HMDS
to be used in the hydrophobic processing of the surface can be
suppressed.
[0045] The resist application device according to the present
embodiment is characterized also by the hot plate 38 for heating
the wafer 10 in the HMDS processing. The HMDS processing is made on
the wafer which is being heated by the hot plate 38, whereby the
adhesion of the resist film to the wafer 10 can be better.
[0046] The resist application device according to the present
embodiment is characterized also in that while the device is in
operation, dehumidified air, i.e., clean dry air is fed into the
first thermal processing unit 14, the first cooling processing unit
16, the HMDS processing unit 18, the second cooling processing unit
20 and the arm moving region 26. The clean dry air is fed into the
processing units into which the wafer 10 is carried, and in the
dehumidified atmosphere, the wafer 10 is carried and is subjected
to the serial processing, whereby re-adsorption of the water to the
surface of the wafer 10 can be suppressed. Thus, the hydrolytic
reaction of the HMDS to be used in the surface hydrophobic
processing due to the water can be suppressed.
[0047] As described above, the resist application device according
to the present embodiment suppresses the hydrolytic reaction of the
HMDS to be used in the hydrophobic processing of the surface of the
wafer 10, whereby the generation of foreign substances which are a
cause for inconveniences, such as pattern defects, etc. on the
surface of the wafer 10 with the resist developed. Furthermore, the
adhesion between the wafer 10 and the resist film can be better.
Thus, semiconductor devices of high quality can be fabricated with
high yields.
[0048] The clean dry air is not fed into the resist application
unit 28, which does not cause the inconvenience either that a
resist film cannot be formed in a uniform thickness.
[0049] In the first thermal processing unit 14, the thermal
processing is performed only by the hot plate 34, which is simple
heating means without pressure reduction, which can make the device
structure simpler in comparison with the device structure in which
the heating is performed with a hot plate in a reduced pressure
chamber.
[0050] [2] The Resist Application Method
[0051] Next, the resist application method according to the present
embodiment will be explained with reference to FIGS. 1 and 2.
[0052] First, the clean dry air is fed respectively into the first
thermal processing unit 14, the first cooling processing unit 16,
the HMDS processing unit 18, the second cooling processing unit 20
and the arm moving region 26. Concurrently therewith, the
respective processing units are exhausted by the exhaust systems
associated respectively therewith to replace atmospheres in the
respective processing units and the arm moving region 26 with the
clean dry air. The clean dry air has, e.g., a -60.degree. C. dew
point at the atmospheric pressure. A flow rate of the fed clean dry
air is, e.g., 3 L/min.
[0053] Then, the processing started (Step S0).
[0054] Next, a wafer 10 is taken off the carrier 32 in the housing
unit 12 by the carrying arm 24, carried to the first thermal
processing unit 14 and mounted on the hot plate 34 in the first
thermal processing unit 14.
[0055] Then, the wafer 10 is heated by the hot plate 34 in the
first thermal processing unit 14 set at, e.g., 225.degree. C. for
60 seconds (Step S1). The heating temperature and heating time of
the wafer 10 are not limited to 225.degree. C. and 60 seconds and
can be suitably set in accordance with various conditions, such as
a wafer size, etc. so that water can be removed from the surface of
the wafer 10. For example, the heating temperature may be above
100.degree. C. including 100.degree. C. The heating temperature of
the wafer 10 is set at above 150.degree. C. including 150.degree.
C. to thereby evaporate water on the surface of the wafer 10 in a
short period of time without failure. With the heating temperature
set at 200.degree. C. including 200.degree. C., water on the
surface of the wafer 10 can be evaporated in a further shorter
period of time without failure.
[0056] When the wafer 10 has been thermally processed, the wafer 10
is carried by the carrying arm 24 from the first thermal processing
unit 14 to the first cooling processing unit 16, and is mounted on
the cooling plate 36 in the first cooling processing unit 16. At
this time, the arm moving region 26 where the wafer is to be moved,
and the first cooling processing unit 16 have been fed with the
dehumidified clean dry air. Thus, after the thermal processing by
the first thermal processing unit 14, the re-adsorption of water to
the surface of the wafer 10 can be suppressed.
[0057] Subsequently, the wafer 10 is cooled by the cooling plate 36
in the first cooling processing unit 16 (Step S2). The wafer 10 is
cooled until the temperature of the wafer 10 becomes, e.g.,
23.degree. C., which is the room temperature.
[0058] After the cooling processing of the wafer 10 is completed,
the wafer 10 is carried by the carrying arm 24 from the first
cooling processing unit 16 to the HMDS processing unit 18 filled
with dry nitrogen, and the wafer 10 is mounted on the hot plate 38
in the HMDS processing unit 18. At this time, the arm moving region
26 where the wafer 10 is moved is fed with the humidified clean dry
air. Thus, after the thermal processing by the first thermal
processing unit 14, the re-adsorption of water to the surface of
the wafer 10 can be suppressed.
[0059] Next, the HMDS which has been vaporized by, e.g., bubbling
is carried on nitrogen gas into the HMDS processing unit 18 to
expose the surface of the wafer 10 to the vaporized HMDS. During
this processing, the wafer 10 is kept heated to, e.g., 110.degree.
C. by the hot plate 38 in the HMDS processing unit 18 (Step S3).
The heating temperature here is not limited to 110.degree. C., and
can be, e.g., above 100.degree. C. including 100.degree. C. as long
as the re-adsorption of water to the surface of the surface 10 can
be suppressed.
[0060] When the HMDS processing is over, the wafer 10 is carried by
the carrying arm 24 from the HMDS processing unit 18 to the second
cooling processing unit 20, and the wafer 10 is mounted on the
cooling plate 40 in the second cooling processing unit 20.
Subsequently, the wafer 10 is cooled by the cooling plate 40 in the
second cooling processing unit 20 (Step S4). The wafer 10 is cooled
until the temperature of the wafer 10 becomes, e.g., 23.degree. C.,
which is the room temperature.
[0061] When the cooling processing of the wafer 10 is over, the
wafer 10 is carried by the carrying arm 24 from the second cooling
processing unit 20 to the resist application unit 28, the wafer 10
is held by the wafer chuck 46 in the resist application unit
38.
[0062] Then, a prescribed amount of a resist is dropped onto the
surface of the wafer 10 being rotated in horizontal plane by the
wafer chuck 46. The resist is thus applied to the surface of the
wafer 10 by spin coating (Step S5). During this operation, the
atmosphere in the resist application unit 18 is air having the
humidity controlled to be, e.g., 45%. The temperature of the wafer
10 is controlled to be, e.g., 23.degree. C. Thus, the atmosphere in
the resist application unit 28 where the resist is applied has a
suitable amount of water, which permits the resist film to be
formed in a uniform thickness.
[0063] When the resist application is completed, the wafer 10 is
carried by the carrying arm 24 from the resist application unit 28
to the second thermal processing unit 22, and the wafer 120 is
mounted on the hot plate 42 in the second thermal processing unit
22. Subsequently, the wafer 10 is heated to about 120.degree. C. by
the hot plate 44 in the second thermal processing unit 22. The
resist immediately after the application, which contains a suitable
amount of organic solvent is thus dried and solidified (Step S6).
The clean dry air which has been fed into the first thermal
processing unit 14, etc. does not have to be fed into the second
thermal processing unit 22. The atmosphere in the second thermal
processing unit 22 may be the same as that of, e.g., the clean
room. The heating temperature is not limited to about 120.degree.
C. and can be suitably set in accordance with a kind, etc. of the
applied resist.
[0064] Then, the wafer 10 is carried by the carrying arm 24 from
the second thermal processing unit 22 to the housing unit 12, and
the wafer 10 is mounted on the carrier 32. Thus, the application of
the resist by the resist application method according to the
present embodiment is completed (Step S7).
[0065] The wafer 10 having the resist thus applied to is carried,
mounted on the carrier 32, to the next step of the exposure
etc.
[0066] As described above, according to the present embodiment, the
clean dry air having the water content controlled to be small is
fed into the respective processing units, the wafer 10 is subjected
to the thermal processing before the HMDS processing, and the HMDS
processing is performed with the wafer 10 being heated, whereby the
hydrolysis of the HMDS to be used in the hydrophobic processing of
the surface can be suppressed. Thus, the generation of foreign
substances on the surface of the wafer 10 can be suppressed, and
also the adhesion between the wafer 10 and the resist can be made
better. Semiconductor devices of high quality can be fabricated
with high yields.
[0067] Japanese Published Patent Application No. Hei 05-315233
(1993) discloses the art that before the HMDS processing, a
semiconductor substrate is mounted on a plate heated at 80.degree.
C. to be processed for 30 seconds at an about 60 mmHg degrees of
vacuum, whereby water is removed from the semiconductor substrate
surface. However, at the heating temperature of 80.degree. C., it
is difficult to remove water from the semiconductor substrate
surface without failure for a short period of time even at a
reduced pressure.
[0068] In the present embodiment, water 10 is heated at the
above-described high temperature, which makes it possible to
removed water from the surface of the wafer 10. In the present
embodiment, the pressure reduction is not necessary for the heat
processing, which allows to use simple heating means.
[0069] The art disclosed in Japanese Published Patent Application
No. Hei 05-315233 (1993) is for improving the adhesion of the
resist film, and is quite different from the present invention,
which is for suppressing the occurrence of the foreign substances.
Japanese Published Patent Application No. Hei 05-315233 (1993)
neither discloses nor suggests the heating temperature for
preventing the occurrence of the foreign substances.
[0070] (Evaluation Result)
[0071] Wafers coated with a resist by the resist application method
according to the present embodiment and the prior art resist
application methods were compared for evaluation in numbers of
foreign substances detected by a foreign substance detector.
[0072] FIGS. 3A and 3B show pictures of the wafers coated with the
resist, which show the results of the detection of foreign
substances by the foreign substance detector. FIG. 3A is the
picture of the wafer coated with the resist by the resist
application method according to the present embodiment. FIG. 3B is
the picture of the wafer coated with the resist by the prior art
method. In the wafer pictures, scattered points of gray to black
indicate foreign substances. The numbers indicated below the
respective pictures indicate numbers of foreign substances produced
due to the hydrolysis of the HMDS with respect to total numbers of
the detected foreign substances.
[0073] In the case of the present embodiment, of the total number
16 of the detected foreign substances, the number of the foreign
substances generated due to the hydrolysis was 0. In contrast to
this, in the case of the prior art method, of the total number 184
of the detected foreign substances, the number of the foreign
substances generated due to the hydrolysis of the HMDS was 109.
[0074] Based on the results shown in FIGS. 3A and 3B, it has been
found that the resist application method according to the present
embodiment can drastically decrease the number of foreign
substances generated due to the hydrolysis of the HMDS which are to
be the cause for pattern defects in the etching in comparison with
the prior art method. It has been also found that the total number
of the foreign substances detected on the wafer coated with the
resist can be smaller.
[0075] [Modifications]
[0076] The present invention is not limited to the above-described
embodiment and can cover other various modifications.
[0077] For example, in the above-described embodiment, the
hydrophobic processing was performed by using HMDS, but the
hydrophobic processing material to be used in the making the
surface hydrophobic is not limited to HMDS.
[0078] In the present embodiment, the clean dry air has a
-60.degree. C. dew point in the atmospheric pressure. However, the
water content of the clean dry air is not limited to this, and the
clean dry air can have a humidity of, e.g., below 20% including
20%.
[0079] In the present embodiment, the dry clean air is fed into the
respective processing units, and the serial processing is performed
in the dehumidified atmosphere. However, a gas to be fed into the
respective processing unit is not limited to the clean dry air, and
any gas can be used as long as the gas is dehumidified. In place of
the clean dry air, an inert gas, e.g., nitrogen gas, rare gas or
others may be fed. Otherwise, a mixed gas of them may be used. The
use of the dry clean air is free from the risk of oxygen deficiency
accidents which are present in the use of nitrogen gas or others,
and has an advantage that safety equipments are not required.
[0080] In the above-described embodiment, a resist is applied onto
wafers. However, the present invention is not limited to the
application of a resist onto wafers and is applicable widely to the
resist application onto various substrates, such as semiconductor
substrates, glass substrates, etc.
[0081] In the above-described embodiment, the resist is applied
onto wafers by spin coating. However, the method for applying a
resist onto wafers is not limited to the spin coating.
[0082] In the above-described embodiment, the serial process up to
the application of the resist to the wafer is described. However,
it is possible that the resist application method according to the
present invention is incorporated in the semiconductor device
fabrication steps to form resist films to be used in forming
various patterns, as of insulation layers, wiring layers, etc. of
semiconductor devices.
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