U.S. patent application number 12/034975 was filed with the patent office on 2008-08-21 for substrate processing apparatus, substrate processing method, and method of manufacturing semiconductor device.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Tomokazu KAWAMOTO.
Application Number | 20080200018 12/034975 |
Document ID | / |
Family ID | 39707047 |
Filed Date | 2008-08-21 |
United States Patent
Application |
20080200018 |
Kind Code |
A1 |
KAWAMOTO; Tomokazu |
August 21, 2008 |
SUBSTRATE PROCESSING APPARATUS, SUBSTRATE PROCESSING METHOD, AND
METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE
Abstract
There is disclosed a substrate processing apparatus including a
processing chamber housing a substrate, pipes for supplying gas
into the processing chamber, and heaters provided in the middle of
the pipes, and heating the gas. In the substrate processing
apparatus, the heaters heat the gas to a temperature lower than a
temperature at which exhaust gas is generated from the pipes to dry
the substrate in the heated gas.
Inventors: |
KAWAMOTO; Tomokazu;
(Kawasaki, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
39707047 |
Appl. No.: |
12/034975 |
Filed: |
February 21, 2008 |
Current U.S.
Class: |
438/530 ;
134/105; 134/21; 134/30; 134/31; 257/E21.255; 257/E21.473 |
Current CPC
Class: |
H01L 29/66575 20130101;
H01L 21/67034 20130101; H01L 21/31133 20130101; H01L 29/7833
20130101; H01L 21/67028 20130101; H01L 21/02057 20130101 |
Class at
Publication: |
438/530 ;
134/105; 134/31; 134/30; 134/21; 257/E21.473 |
International
Class: |
H01L 21/425 20060101
H01L021/425; B08B 13/00 20060101 B08B013/00; B08B 5/00 20060101
B08B005/00; B08B 3/04 20060101 B08B003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2007 |
JP |
2007-040322 |
Claims
1. A substrate processing apparatus comprising: a processing
chamber that houses a substrate; a pipe that supplies gas into the
processing chamber; and a heating unit that is provided in the
middle of the pipe and heats the gas, wherein the heating unit
heats the gas to a temperature lower than a temperature at which
degas is generated from the inside of the pipe, and the substrate
is dried in the heated gas.
2. The substrate processing apparatus according to claim 1, wherein
the gas contains a vaporized organic solvent.
3. The substrate processing apparatus according to claim 2, wherein
the concentration of the organic solvent in the gas is set so that
a dew point of the organic solvent becomes lower than room
temperature.
4. The substrate processing apparatus according to claim 3, wherein
the temperature of the gas is equal to or above a room
temperature.
5. The substrate processing apparatus according to claim 1, wherein
the gas is inert gas.
6. The substrate processing apparatus according to claim 1, wherein
a liquid tank containing a liquid and a substrate holder for
dipping the substrate into the liquid in the liquid tank are
further provided in the processing chamber.
7. The substrate processing apparatus according to claim 6, wherein
the substrate is cleaned in the liquid tank, a gas containing a
vaporized organic solvent is supplied from the pipe into the
processing chamber after the cleaning, and an inert gas is supplied
from the pipe into the processing chamber to replace the atmosphere
inside the processing chamber with the inert gas.
8. The substrate processing apparatus according to claim 6, wherein
the liquid is any of a deionized water and a chemical solution.
9. The substrate processing apparatus according to claim 1, wherein
the pipe is made of resin.
10. The substrate processing apparatus according to claim 9,
wherein the temperature at which the degas is generated is
100.degree. C.
11. A substrate processing method comprising: drying a substrate by
exposing the substrate to a heated gas supplied from a pipe, and by
setting the gas to a temperature lower than a temperature at which
degas is generated from the pipe.
12. The substrate processing method according to claim 11, wherein
a gas containing a vaporized organic solvent is used as the
gas.
13. The substrate processing method according to claim 12, wherein
the organic solvent in the gas is set to have such a concentration
that a dew point of the organic solvent becomes lower than a room
temperature.
14. The substrate processing method according to claim 13, wherein
the temperature of the gas is set equal to or above the room
temperature.
15. The substrate processing method according to claim 11, further
comprising: dipping the substrate into a liquid to clean the
substrate before drying the substrate
16. The substrate processing method according to claim 15, wherein
the drying of the substrate is performed by supplying a gas
containing a vaporized organic solvent from the pipe into an
atmosphere and then replacing the atmosphere with an inert gas by
supplying the inert gas from the pipe into the atmosphere.
17. The substrate processing method according to claim 11, wherein
the pipe is made of resin, and the temperature at which the degas
is generated is 100.degree. C.
18. A method of manufacturing a semiconductor device comprising:
cleaning a semiconductor substrate; performing a first drying for
the semiconductor substrate after the cleaning; forming a resist
pattern on the semiconductor substrate after performing the first
drying; forming a well in the semiconductor substrate by implanting
ions of an impurity into the semiconductor substrate by using the
resist pattern as a mask; removing the resist pattern; cleaning the
semiconductor substrate after removing the resist pattern;
performing a second drying for the semiconductor substrate after
cleaning the substrate; and forming a gate insulating film on the
semiconductor substrate after performing the second drying, wherein
the semiconductor substrate is exposed to heated gas supplied from
a pipe in at least any of the first drying and the second drying,
and the gas is set to have a temperature lower than a temperature
at which a degas is generated from the pipe.
19. The method of manufacturing a semiconductor device according to
claim 18, wherein a gas containing a vaporized organic solvent is
used as the gas, and the organic solvent in the gas is set to have
such a concentration that a dew point of the organic solvent
becomes lower than a room temperature.
20. The method of manufacturing a semiconductor device according to
claim 18, wherein the gas is set to have a temperature equal to or
above a room temperature.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority of Japanese
Patent Application No.2007-040322 filed on Feb. 21, 2007, the
entire contents of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] It is related to a substrate processing apparatus, a
substrate processing method, and a method of manufacturing a
semiconductor device.
BACKGROUND
[0003] In manufacturing processes for a semiconductor device such
as a large-scale integrated circuit (LSI), various cleaning
processes are performed for the purpose of removing organic
materials and the like on a semiconductor substrate. The cleaning
processes typically include the steps of dipping a semiconductor
substrate into a chemical solution, washing the semiconductor
substrate with deionized water, and then drying the semiconductor
substrate.
[0004] In the drying step, a drying rate is accelerated by taking
out the semiconductor substrate to an alcohol atmosphere and
consequently replacing moisture on a surface of the substrate with
alcohol.
[0005] The above-mentioned drying step is described in detail in
Japanese Patent Application Laid-open Publication No. Hei
11-354485, for example.
[0006] According to Japanese Laid-open Patent Publication No.
11-354485, occurrence of dew condensation on a surface of a
substrate is prevented by heating, in the drying step, the
substrate to a higher temperature than the higher one of a water
dew point and an alcohol dew point, so that attachment of particles
to the substrate attributable to the dew condensation is
prevented.
[0007] In addition, the techniques related to the present
embodiments are also disclosed in Japanese Laid-open Patent
Publication No. 64-69015, Japanese Laid-open Patent Publication No.
2005-166958 and Japanese Laid-open Patent Publication No.
2003-273059.
SUMMARY
[0008] It is an aspect of the embodiments discussed herein to
provide a substrate processing apparatus including a processing
chamber that houses a substrate, a pipe that supplies gas into the
processing chamber, and a heating unit that is provided in the
middle of the pipe and heats the gas, wherein the heating unit
heats the gas to a temperature lower than a temperature at which
degas is generated from the inside of the pipe, and the substrate
is dried in the heated gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a configuration diagram showing a substrate
cleaning system used in an embodiment;
[0010] FIG. 2 is a configuration diagram showing a substrate
processing apparatus according to the embodiment;
[0011] FIG. 3 is a schematic diagram showing a gas supply mechanism
for the substrate processing apparatus according to the
embodiment;
[0012] FIGS. 4A to 4H are schematic diagrams for explaining a
substrate processing method according to the embodiment;
[0013] FIGS. 5A and 5B are wafer maps obtained by investigating
photoresist defects by using a defect inspection apparatus;
[0014] FIG. 6 is a graph obtained by investigating relations
between the temperature of nitrogen gas and the organic materials
content; and
[0015] FIGS. 7A to 7J are cross-sectional views in the course of
manufacturing a semiconductor device according to the
embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0016] FIG. 1 is a configuration diagram showing a substrate
cleaning system 100 used in the present embodiment.
[0017] This system 100 is a batch system capable of simultaneously
processing multiple substrates W, and includes first to fourth
processing tanks 101 to 104 storing deionized water or chemical
solutions, and a substrate processing apparatus 105 for drying the
substrates W. The types of the substrates W are not particularly
limited, and it is possible to process, as the substrates W,
silicon (semiconductor) substrates for semiconductor devices, or
quartz substrates used for liquid crystal display devices and the
like.
[0018] Moreover, the liquids to be stored in the respective
processing tanks 101 to 104 are not particularly limited. In this
embodiment, deionized water is stored in the second and fourth
processing tanks 102 and 104, for example. Meanwhile, SPM is stored
in the first processing tank 101, and APM is stored in the third
processing tank 103. Here, the SPM means a mixed solution of
sulfuric acid, hydrogen peroxide water, and deionized water
(sulfuric acid hydrogen peroxide mixture), and the APM means a
mixed solution of ammonia, hydrogen peroxide water, and deionized
water (ammonia hydrogen peroxide mixture).
[0019] Note that it is also possible to use HPM or buffer
hydrofluoric acid, instead of the APM or the SPM. The HPM means a
mixed solution of hydrochloric acid, hydrogen peroxide water, and
deionized water (hydrochloric acid-hydrogen peroxide mixture).
[0020] The multiple substrates W are held by a lifter (a substrate
holder) 4. The lifter 4 moves in the directions of arrows in FIG. 1
by use of an unillustrated motor, and conveys the substrates W to
the respective processing tanks 101 to 104 in an arbitrary order.
Then, the silicon substrates W are eventually housed in the
processing apparatus 105 by the lifter 4 in order to dry the
substrates W.
[0021] FIG. 2 is a configuration diagram showing the substrate
processing apparatus 105.
[0022] This substrate processing apparatus 105 has a function to
dry the substrates W, and includes a processing chamber 2 and a
liquid tank 3. The liquid tank 3 can store water, chemical
solutions, and the like. A pipe 9 for supplying these liquids, a
pipe 8 for draining the liquids, and a pipe 7 for returning the
liquids are connected to the liquid tank 3 as illustrated in FIG.
2.
[0023] Moreover, a groove 3a is formed on an upper end of the
liquid tank 3 so that the liquid spilling out of the liquid tank 3
is collected by use of the groove 3a and a pipe 10.
[0024] Further, a horizontally movable shutter 11 is provided above
the processing chamber 2. The processing chamber 2 is hermetically
sealed when this shutter 11 is closed.
[0025] Meanwhile, the hermetically sealed state inside the
processing chamber 2 is interrupted by opening the shutter 11
before and after the processing in the processing chamber 2, so
that the above-described lifter 4 can go in and out of the
processing chamber 2. The lifter 4 is capable of moving vertically
in the processing chamber 2. With this movement of the lifter 4,
the substrates W can be put into the liquid tank 3 and pulled out
of the liquid tank 3.
[0026] A space above the liquid tank 3 is used for drying the
substrates W in a vaporized organic solvent atmosphere such as IPA
(isopropyl alcohol) gas, or in an inert gas such as a nitrogen gas.
For supplying these gases, a gas supply port 5 is provided on an
upper part of the processing chamber 2. Moreover, in order to
accelerate a drying rate by reducing pressure in the processing
chamber 2, an exhaust port 6 connected to an unillustrated vacuum
pump is provided at a lower part of the processing chamber 2.
[0027] FIG. 3 is a schematic diagram showing a gas supply mechanism
for this substrate processing apparatus 105.
[0028] As shown in FIG. 3, the substrate processing apparatus 105
includes first to four gas pipes 15 to 18. Among them, a nitrogen
supply source 21 such as a nitrogen gas cylinder is connected to
the starting end of the first pipe 15, so that nitrogen gas
supplied from this nitrogen supply source 21 is supplied to the
processing chamber 2 through the first pipe 15 and the fourth pipe
18.
[0029] Meanwhile, the second gas pipe 16 is also connected to the
nitrogen supply source 21, and an IPA container 22 is provided on
the end of this second gas pipe 16.
[0030] IPA is stored in the IPA container 22. The IPA is vaporized
by heating the IPA with an IPA heater 20 provided below the
container 22. The vaporized IPA passes through the third gas pipe
17 and the fourth gas pipe 18, and is then supplied to the
processing chamber 2 together with the nitrogen gas having passed
through the second gas pipe 16.
[0031] Here, the concentration of the IPA gas in the mixed gas of
the IPA gas and the nitrogen gas can be controlled by the
temperature of the IPA heater 20. For example, more IPA is
vaporized and the concentration of the IPA is increased by raising
the temperature of the IPA heater 20. On the contrary, the
concentration is reduced by lowering the temperature of the IPA
heater 20.
[0032] Switching between the nitrogen gas and the IPA gas is
executed by use of first and second valves 26 and 27. When
supplying only the nitrogen gas to the processing chamber 2, the
first valve 26 is closed and the second valve 27 is opened, to
supply the nitrogen gas by way of a passage A shown in FIG. 3. On
the contrary, when supplying the IPA gas, the first valve 26 is
opened and the second valve 27 is closed, to supply the IPA gas by
way of a passage B.
[0033] Moreover, first and second heaters (heating units) 23 and 24
are provided in the middle of the third gas pipe 17 and the fourth
gas pipe 18, respectively.
[0034] In the case of supplying only the nitrogen gas to the
processing chamber 2, the nitrogen gas passing through the passage
A is heated by the second heater 24. On the contrary, in the case
of supplying the IPA gas to the processing chamber 2, the IPA gas
passing through the passage B is heated by both the first and
second heaters 23 and 24.
[0035] Here, it is preferable to use a flexible material for the
material of the respective gas pipes 15 to 18 so that the
respective gas pipes 15 to 18 can be arranged easily in a small
space in the system. As such a material, in this embodiment,
fluororesin having excellent chemical resistance such as PTFE
(polytetrafluoroethylene) or PFA (perfluoroalcoxy) is used.
[0036] Next, a substrate processing method using the substrate
processing apparatus 105 will be described below.
[0037] FIGS. 4A to 4H are schematic diagrams for explaining this
substrate processing method.
[0038] This example is effective for a wet process in a
manufacturing process of a semiconductor device using silicon
substrates as the substrates W, where the wet process is carried
out for removing resist residues after a resist pattern is removed
by ashing.
[0039] In this wet process, the substrates W are firstly cleaned in
the first to fourth processing tanks 101 to 104 of the substrate
cleaning system 100 shown in FIG. 1.
[0040] Subsequently, the substrates W are dried in accordance with
the following procedures.
[0041] Firstly, as shown in FIG. 4A, the shutter 11 is opened for
putting the substrates W into the processing chamber 2, and then
the shutter 11 is closed to hermetically seal the processing
chamber 2.
[0042] Subsequently, as shown in FIG. 4B, the DIW (deionized water)
is supplied from the pipe 9 (see FIG. 2) to the liquid tank 3 so as
to fill the liquid tank 3 with the deionized water. Then, the
substrates W are dipped in the deionized water by descending the
lifter 4, and thereby, the liquids attached to surfaces of the
substrates W during the processes in the first to fourth processing
tanks 101 to 104 are removed with the deionized water. This process
is also called a rinsing process.
[0043] Next, as shown in FIG. 4C, the IPA gas is supplied from the
gas supply port 5 to the processing chamber 2 to fill the
processing chamber 2 with an IPA atmosphere.
[0044] Here, the IPA gas is heated by the first and second heaters
23 and 24 as described in FIG. 3. The heating temperature is around
90.degree. C. immediately after being supplied from the gas supply
port 5, for example.
[0045] Subsequently, as shown in FIG. 4D, the silicon substrates W
are pulled up from the liquid tank 3 by use of the lifter 4. In
this way, the silicon substrates W are exposed to the IPA gas
atmosphere, and consequently, water droplets attached to the
surfaces of the substrates W are replaced with the IPA. Since the
vapor pressure of the IPA is higher than that of the deionized
water, the surfaces of the substrates W can be dried up more
quickly.
[0046] In addition, since the IPA gas is heated by the first and
second heaters 23 and 24 as described previously, the substrates W
are also heated and thus dried up more quickly, and the water
droplets on the surfaces of the substrates W are more easily
replaced with the IPA.
[0047] Subsequently, as shown in FIG. 4E, the IPA gas supply is
stopped, and then the deionized water in the liquid tank 3 is
expelled from the pipe 8 (see FIG. 2) to the outside, so that the
liquid tank 3 becomes empty.
[0048] Next, as shown in FIG. 4F, the nitrogen gas is supplied from
the gas supply port 5 to the processing chamber 2 so as to replace
the atmosphere of the IPA in the processing chamber 2 by the
nitrogen.
[0049] Here, the nitrogen gas is heated by the second heater 24 as
described in FIG. 3. The nitrogen temperature is around 90.degree.
C. immediately after being supplied from the gas supply port 5, for
example.
[0050] The heated state of the substrates W is maintained by
exposing the substrates W to the heated nitrogen gas in this
manner.
[0051] Next, as shown in FIG. 4G, the nitrogen gas supply is
stopped, and then the nitrogen gas is exhausted from the outlet
port 6 (see FIG. 2) to reduce the pressure in the processing
chamber 2. By reducing the pressure in this maner, the IPA
condensed on the surfaces of the substrates W is vaporized, so that
the surfaces of the substrates W are dried up efficiently.
[0052] Lastly, as shown in FIG. 4H, the processing chamber 2 is set
open to the air by opening the shutter 11, and then, the substrates
W are taken out of the processing chamber 2.
[0053] In this way, the principal steps of the substrate process
are completed.
[0054] Although the deionized water is collected in the liquid tank
3, it is also possible to use other chemical solutions such as APM,
SPM, HPM, a buffer hydrofluoric acid solution, and the like,
instead of the deionized water.
[0055] Heating the gas in the step (FIG. 4C) of introducing the IPA
gas and in the step (FIG. 4F) of introducing the nitrogen gas when
the silicon substrates W are dried in the substrate processing
apparatus 105 is effective for increasing drying efficiency and
preventing dew condensation on the silicon substrates W.
[0056] The gas temperature that can prevent dew condensation is
expected to be equal to or above 125.degree. C.
[0057] It is to be noted, however, that such a dew condensation
prevention of the IPA is premised on that the dew point of the IPA
is equal to or above room temperature (20.degree. C.). For this
reason, if the dew point of the IPA is below room temperature as in
the case of a low concentration of the IPA gas, the IPA is not
condensed on the substrates W even when the IPA gas is not
heated.
[0058] Rather, the results of the investigation conducted by the
inventor of the present application show that the reliability of
the semiconductor device is reduced, and product yield thereof is
deteriorated, when the gas temperature is set to be high. The
details are as follows.
[0059] FIGS. 5A and 5B are wafer maps obtained by subjecting a
300-mm silicon wafer (the substrates W) to the steps described in
FIGS. 4A to 4H, then coating photoresist on the silicon wafer, and
then investigating photoresist defects by use of a defect
inspection apparatus.
[0060] Of these wafer maps, FIG. 5A is the wafer map obtained in
the case of heating the nitrogen gas to 120.degree. C. in the step
shown in FIG. 4F. Meanwhile, FIG. 5B is the wafer map obtained in
the case of heating the nitrogen gas to 90.degree. C. in this step.
Here, the temperature of the nitrogen gas is obtained by measuring
the nitrogen gas immediately after being supplied from the gas
supply port 5 with a thermometer. The gas temperature hereinafter
in this specification is defined as the temperature of the gas
immediately after being supplied from the gas supply port 5 in this
manner.
[0061] As shown in FIG. 5A, when the temperature of the nitrogen
gas is set to be 120.degree. C., defects are generated over a broad
range on the wafer W. These defects are assumed to be minute holes
(micro bubbles) formed in a photoresist film.
[0062] Formation of these defects in the photoresist leads to a
problem of unnecessary ion implantation in a region, on the silicon
wafer, unexpected for ion implantation if the photoresist is used
as a mask for such ion implantation. Meanwhile, formation of these
defects in the photoresist leads to a problem of deviation in the
shape of an etched film from a designed shape if the photoresist is
used as a mask for etching.
[0063] By contrast, as shown in FIG. 5B where the temperature of
the nitrogen gas is set to be 90.degree. C., defects generated in
the photoresist are significantly reduced.
[0064] From these investigation results, it is apparent that the
photoresist defects are more prominent than the effect of dew
condensation prevention on the silicon wafer, when the temperature
of the nitrogen gas is set to an unnecessarily high temperature,
for example, equal to or above 120.degree. C., so that the yield of
the semiconductor devices is reduced.
[0065] In order to investigate the cause for generation of the
defects in the photoresist as described above, the inventor of the
present application carried out the steps shown in FIGS. 4A to 4H
on a 300-mm silicon wafer, and then measured, by using a gas
chromatograph-mass spectrometry (GC-MS), degas generated from the
silicon wafer due to an organic materials. Note that no photoresist
was coated on the silicon wafer when this measurement was carried
out. Moreover, in this measurement, the temperature of the nitrogen
gas is variously changed in the step shown in FIG. 4F in order to
investigate the temperature dependency of the organic
materials.
[0066] FIG. 6 shows the result of this measurement.
[0067] The horizontal axis in FIG. 6 indicates the temperature of
the nitrogen gas while the vertical axis therein indicates
normalized organic materials content.
[0068] As shown in FIG. 6, the organic materials content is quite
small when the temperature of the nitrogen gas ranges from
40.degree. C. to 100.degree. C.
[0069] On the contrary, the organic materials content is suddenly
increased when the temperature of the nitrogen gas reaches
120.degree. C.
[0070] By combining this result and the above-described results in
FIGS. 5A and 5B, the organic materials adhered to the surfaces of
the silicon wafer are attributed to the generation of the numerous
defects in the photoresist in the case of setting the temperature
of the nitrogen gas to 120.degree. C. This is because adhesion
between the silicon wafer and the photoresist is degraded when the
organic materials are adhered to the surface of the silicon wafer,
whereby the above-mentioned micro bubbles are generated in the
photoresist.
[0071] Experiments were repeated by replacing various parts in the
processing chamber 2 in order to specify the generation source of
the organic materials. However, no improvement of the defects was
observed. Accordingly, the experiments showed that the generation
source of the organic materials resides outside the processing
chamber 2, i.e. in the fourth gas pipe 18.
[0072] As described previously, the fourth gas pipe 18 is made of
fluororesin. Hence, it is conceivable that organic degas (i.e.,
degassing of organic materials) is generated from an inner wall of
the fourth gas pipe 18 with the increase in the temperature of the
nitrogen gas, and thereby, the organic materials adhered to the
silicon wafer are increased.
[0073] As described above, from the viewpoint of improving the
reliability of the semiconductor device by reducing the content of
organic materials adhered to the silicon wafer during the process,
it is necessary to heat the nitrogen gas to a temperature lower
than the temperature at which degas from the fourth gas pipe 18 is
generated, in the step of drying the silicon wafer. Such a
temperature is equal to or below 100.degree. C. according to FIG.
6.
[0074] Moreover, by setting the temperature of the nitrogen gas
equal to or below 100.degree. C., which is equal to or below the
boiling point of water, the moisture remaining in the liquid tank 3
and the like in the processing chamber 2 is not vaporized in the
course of drying the silicon wafer. Accordingly, it is possible to
prevent the moisture remaining in the processing chamber 2 from
being vaporized and condensed on the silicon wafer W. Thus, since
no particles associated with the condensed moisture remain on the
silicon wafer W after drying, it is possible to further improve the
reliability of the semiconductor devices.
[0075] Here, the above-described investigation results concern the
nitrogen gas. However, similar tendencies as those described with
reference to FIGS. 5A and 5B and FIG. 6 are also observed in the
case of introducing the IPA gas in the step shown in FIG. 4C. Thus,
it is also necessary to heat the IPA gas to a temperature lower
than the temperature, i.e. equal to or below 100.degree. C., at
which degas is generated from the third and fourth gas pipes 17 and
18 where the heated IPA gas passes through, upon introduction to
the processing chamber 2.
[0076] Even when the IPA gas is set at a low temperature in this
manner, dew condensation of the IPA on the surfaces of the wafer is
prevented as long as the temperature of the IPA gas is kept equal
to or above room temperature, under the conditions that the
concentration of the IPA gas is low and hence the dew point of the
IPA is lower than room temperature.
[0077] In the case when high drying efficiency is required, for
example, a case where there are large unevenness on a surface of a
wafer so that water droplets are apt to remain on the substrate,
the concentration of the IPA gas is usually increased to make it
easier to replace the moisture remaining on the wafer with the
IPA.
[0078] However, in this embodiment, the concentration of the IPA
gas is adjusted to such a concentration that the dew point of the
IPA be below room temperature as described previously, in order to
give priority to dew condensation prevention over drying
efficiency. Such adjustment can be made by controlling the setting
temperature of the above-described IPA heater 20.
[0079] Next, a method of manufacturing a semiconductor device based
on the above investigation results will be described.
[0080] FIGS. 7A to 7J are cross-sectional views in the course of
manufacturing a semiconductor device according to the embodiment of
the present embodiment.
[0081] Firstly, as shown in FIG. 7A, shallow trench isolation (STI)
grooves for defining active regions of transistors are formed on a
surface of a silicon substrate 30 either of an n-type or a p-type,
and an insulating film, such as silicon oxide, is buried therein to
form element isolation insulating films 31. Here, the element
isolation structure is not limited only to the STI, and it is also
possible to form the element isolation insulating films 31 in
accordance with the local oxidation of silicon (LOCOS) method.
[0082] Further, a thermal oxidation film is formed with a thickness
of about 10 nm as a sacrificial insulating film 32 by subjecting
the surface of the silicon substrate 30 to thermal oxidation.
[0083] Subsequently, a first resist pattern 33 is formed on the
sacrificial insulating film 32 as shown in FIG. 7B.
[0084] Then, a p-type impurity is ion-implanted to the silicon
substrate 30 through a window 33a of the first resist pattern 33
while the sacrificial insulating film 32 is used as a through film,
so as to form a p-well 34.
[0085] Thereafter, the first resist pattern 33 is removed as shown
in FIG. 7C. This process is carried out as follows.
[0086] Firstly, a major part of the first resist pattern 33 is
changed into ash and removed by ashing, in which the silicon
substrate 30 is heated in a mixed atmosphere of nitrogen and
oxygen.
[0087] Subsequently, the silicon substrate is subjected to the wet
process in the substrate cleaning system 100 described in FIG. 1,
in order to remove the first resist pattern 33 remaining even after
the ashing process.
[0088] This wet process is broadly categorized into cleaning steps
performed in the first to fourth processing tanks 101 to 104 and a
drying step (a first drying step) performed in the substrate
processing apparatus 105.
[0089] Of these steps, the cleaning step includes cleaning with SPM
in the first liquid tank 101, rinsing with deionized water in the
second liquid tank 102, cleaning with APM in the third liquid tank
103, and rinsing with deionized water in the fourth liquid tank
104, by dipping the silicon substrate 30 sequentially in the
respective liquid tanks 101 to 104. Moreover, the cleaning with the
deionized water described with reference to FIGS. 4A and 4B is also
included in this cleaning step.
[0090] Then, in the drying step, the moisture remaining on the
surface of the silicon substrate 30 is dried in accordance with the
above-described steps shown in FIGS. 4C to 4H.
[0091] Here, in the step of introducing the isopropyl alcohol gas
in FIG. 4C and the step of introducing the nitrogen gas in FIG. 4F,
the heating temperature of the gas is set to the temperature lower
than such a temperature that the third and fourth gas pipes 17 and
18 (see FIG. 3) would generate the degas, i.e. the temperature
equal to or below 100.degree. C. In this way, it is possible to
suppress generation of the degas containing the organic materials
emitted from the gas pipes 17 and 18 made of the fluororesin, and
to prevent adhesion of the organic materials to the sacrificial
insulating film 32 after drying.
[0092] Next, as shown in FIG. 7D, photoresist 36 is coated onto the
sacrificial insulating film 32, and then the silicon substrate 30
is subjected to a thermal treatment to vaporize a solvent component
in the photoresist 36. Such a thermal treatment is also called
baking.
[0093] As described previously, the organic materials remaining on
the sacrificial insulating film 32 are reduced after the cleaning
process shown in FIG. 7C. Accordingly, this photoresist 36 has good
adhesion to the sacrificial insulating film 32. Hence, defects,
such as micro bubbles, are hardly generated in the photoresist.
[0094] Subsequently, as shown in FIG. 7E, a second resist pattern
36b including a window 36a is formed by developing the photoresist
36. Since the photoresist 36 includes very few defects as described
above, it is possible to form the fine second resist pattern 36b
without shape anomalies or locally thin portions.
[0095] Then, an n-well 38 is formed in the silicon substrate 30
beside the p-well 34 by implanting ions of an n-type impurity into
the silicon substrate 30 through the window 36a while the
sacrificial insulating film 32 is used as a through film. Since the
second resist pattern 36b is fine as described above, it is
possible to form the n-well 38 having a planar shape as designed,
and to prevent implantation of the n-type impurity into a region of
the silicon substrate 30 outside the n-well 38.
[0096] Next, the second resist pattern 36b is removed as shown in
FIG. 7F by executing the same step as the step illustrated in FIG.
7C.
[0097] Subsequently, as shown in FIG. 7G, the sacrificial
insulating film 32 damaged by the respective ion implantation
processes is removed by wet etching using a hydrofluoric acid
solution so as to expose a cleaning surface of the silicon
substrate 30.
[0098] Thereafter, the cleaning surface of the silicon substrate 30
is subjected to the wet process by use of the cleaning system 100
shown in FIG. 1. This wet process is essentially the same as the
combination of the cleaning step and the drying step described with
reference to FIG. 7C. In the cleaning step, it is also possible to
add a step of dipping the silicon substrate 30 into a buffer
hydrofluoric acid solution in order to remove a natural oxide film
on the surface of the silicon substrate 30.
[0099] Moreover, in the drying step (a second drying step), the
heating temperature of the gas is set equal to or below 100.degree.
C., which is the temperature lower than such a temperature that the
third and fourth gas pipes 17 and 18 (see FIG. 3) would generate
the degas, so as to suppress generation of the degas containing the
organic materials from these gas pipes 17 and 18, and to prevent
adhesion of the organic materials to the surface of the silicon
substrate 30.
[0100] Subsequently, as shown in FIG. 7H, a thermal oxidation film
is formed with a thickness of about 10 nm as a gate insulating film
40 by subjecting the surface of the silicon substrate 30 to thermal
oxidation.
[0101] Here, since no organic matters are adhered to the silicon
substrate 30 in the cleaning step in FIG. 7G, it is possible to
avoid generation of pinholes and the like in the gate insulating
film 40 at the time of its growth, and thereby to prevent
deterioration in withstand voltage of the gate insulating film
40.
[0102] Next, the process for obtaining a cross-sectional structure
shown in FIG. 7I will be described.
[0103] First, a polysilicon film is formed on the gate insulating
film 40 by the CVD method, and this polysilicon film is patterned
into gate electrodes 41a and 41b.
[0104] Then, ions of an n-type impurity are implanted into the p
well 34 beside the gate electrode 41a while these gate electrodes
41 are used as a mask to form an n-type source/drain extension 42a.
Similarly, ions of a p-type impurity are implanted into the n well
38 beside the gate electrode 41b to form a p-type source/drain
extension 42b.
[0105] Note that the ions of the n-type impurity and the ions of
the p-type impurity are separately implanted by using unillustrated
resist patterns.
[0106] Subsequently, as shown in FIG. 7J, an insulating film such
as a silicon oxide film is formed on the entire upper surface of
the silicon substrate 30, and insulating side walls 44 are left
beside the gate electrodes 41a and 41b by etching back the
insulating film.
[0107] Then, n-type source-drain regions 46a and p-type
source-drain regions 46b are formed in the silicon substrate 30
beside these gate electrodes 41a and 41b by means of ion
implantation while the respective gate electrodes 41a and 41b are
used as a mask.
[0108] Next, a refractory metal layer such as a cobalt layer is
formed on the entire upper surface of the silicon substrate 30 by
the sputtering method. Then, this refractory metal layer is heated
to cause a reaction with silicon, thereby forming a refractory
metal silicide layer 47 on the silicon substrate 30. The refractory
metal silicide layer 47 is also formed on top layer portions of the
gate electrodes 41a and 41b, thereby reducing resistance of the
gate electrodes 41a and 41b.
[0109] Thereafter, the unreacted refractory metal layer on the
element isolation insulating films 31 and the like is removed by
wet etching.
[0110] In this way, basic structures of an n-type MOS transistor
TR.sub.n and a p-type MOS transistor TR.sub.p, which are of the
CMOS structure, are completed on the active region of the silicon
substrate 30.
[0111] Then, processes for forming interlayer insulating films
covering the respective transistors TR.sub.n and TR.sub.p and for
forming metal wiring are performed. However, details of these
processes will be omitted herein.
[0112] According to the above-described embodiment, the silicon
substrate 30 is dried in the step of removing the residues of the
first resist pattern 33 in the FIG. 7C and in the wet process of
the silicon substrate 30 in FIG. 7G by use of the substrate
processing apparatus 105.
[0113] In these drying steps, the heating temperature of the gas is
set equal to or below 100.degree. C., which is the lower
temperature than the temperature for generating the degas from the
third and fourth gas pipes 17 and 18 (see FIG. 3). Hence, few
organic materials generate from these gas pipes 17 and 18 adhered
to the silicon substrate 30. In this way, it is possible to prevent
organic contamination in the silicon substrate 30, and to suppress
defects of the semiconductor device associated with organic
contamination, thereby to improve reliability and yield of the
semiconductor device.
[0114] The foregoing is considered as illustrative only of the
principles of the present invention. Further, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and applications shown and described, and accordingly,
all suitable modifications and equivalents may be regarded as
falling within the scope of the invention in the appended claims
and their equivalents.
* * * * *