U.S. patent application number 09/491876 was filed with the patent office on 2002-07-11 for method of processing residue of ion implanted photoresist, and method of producing semiconductor device.
Invention is credited to YOKOSHIMA, SHIGENOBU.
Application Number | 20020090827 09/491876 |
Document ID | / |
Family ID | 12012610 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020090827 |
Kind Code |
A1 |
YOKOSHIMA, SHIGENOBU |
July 11, 2002 |
METHOD OF PROCESSING RESIDUE OF ION IMPLANTED PHOTORESIST, AND
METHOD OF PRODUCING SEMICONDUCTOR DEVICE
Abstract
In order to carry out ashing at a high efficiency without
leaving any residue and also to inhibit corrosion of an underlying
material of a resist and further to prevent particle contamination,
a photoresist is ashed at a low temperature to be removed and a
residue of the photoresist is removed at a high temperature.
Inventors: |
YOKOSHIMA, SHIGENOBU;
(TOCHIGI-KEN, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
12012610 |
Appl. No.: |
09/491876 |
Filed: |
January 27, 2000 |
Current U.S.
Class: |
438/714 ;
257/E21.256 |
Current CPC
Class: |
G03F 7/427 20130101;
H01L 21/31138 20130101 |
Class at
Publication: |
438/714 |
International
Class: |
H01L 021/425; H01L
021/302; H01L 021/461 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 1999 |
JP |
11-019918 |
Claims
What is claimed is:
1. A method of removing a residue comprising ashing and removing a
dopant-implanted photoresist to expose a surface of a processing
article and then removing a dopant-containing residue of the
photoresist remaining on the surface of the processing article,
wherein the dopant-containing residue is removed at a temperature
higher than the temperature at which the photoresist is ashed and
removed.
2. The method according to claim 1, wherein the ashing and removal
of the dopant-implanted photoresist comprises ashing using a plasma
of a gas not containing fluorine.
3. The method according to claim 1, wherein the removal of the
dopant-containing residue comprises a processing using a gas
containing at least one of fluorine and hydrogen.
4. The method according to claim 1, wherein the removal of the
dopant-containing residue comprises a processing using a gas
containing oxygen and at least one of fluorine and hydrogen.
5. The method according to claim 1, wherein the ashing and removal
of the dopant-implanted photoresist comprises ashing using a plasma
of a first gas not containing fluorine, and wherein the removal of
the dopant-containing residue comprises a processing using a second
gas containing at least one of fluorine and hydrogen.
6. The method according to claim 1, wherein the ashing and removal
of the dopant-implanted photoresist comprises ashing using a plasma
of a first gas not containing fluorine, and wherein the removal of
the dopant-containing residue comprises a processing using a second
gas containing oxygen and at least one of fluorine and
hydrogen.
7. The method according to claim 1, wherein the ashing and removal
of the dopant-implanted photoresist comprises ashing using a plasma
of oxygen, and wherein the removal of the dopant-containing residue
comprises a processing using a gas containing oxygen and at least
one of carbon fluoride, nitrogen fluoride, sulfur fluoride, and
ammonia.
8. The method according to claim 1, wherein the dopant is at least
one of phosphorus, arsenic and boron.
9. The method according to claim 1, wherein the ashing comprises a
plasma processing using a microwave plasma.
10. The method according to claim 1, wherein the removal of the
residue comprises a plasma processing using a microwave plasma.
11. The method according to claim 9 or 10, wherein the microwave
plasma is generated by radiating microwaves via a microwave antenna
having a plurality of slots provided in a conductor plate.
12. The method according to claim 1, wherein the ashing is carried
out in such a state that the processing article is not in contact
with a heater, and wherein the removal of the residue is carried
out in such a state that the processing article is in contact with
a heater.
13. A method of processing an article comprising the steps of:
ashing and removing a dopant-implanted photoresist on a surface of
an article at a first temperature; and removing a dopant-containing
residue of the photoresist at a second temperature higher than the
first temperature.
14. The method according to claim 13, wherein the step of ashing
and removal comprises ashing using a plasma of a gas not containing
fluorine.
15. The method according to claim 13, wherein the step of removal
of the residue comprises a processing using a gas containing at
least one of fluorine and hydrogen.
16. The method according to claim 13, wherein the step of removal
of the residue comprises a processing using a gas containing oxygen
and at least one of fluorine and hydrogen.
17. The method according to claim 13, wherein the step of ashing
and removal comprises ashing using a plasma of a first gas not
containing fluorine, and wherein the step of removal of the residue
comprises a processing using a second gas containing at least one
of fluorine and hydrogen.
18. The method according to claim 13, wherein the step of ashing
and removal comprises ashing using a plasma of a first gas not
containing fluorine, and wherein the step of removal of the residue
comprises a processing using a second gas containing oxygen and at
least one of fluorine and hydrogen.
19. The method according to claim 13, wherein the step of ashing
and removal comprises ashing using a plasma of oxygen, and wherein
the step of removal of the residue comprises a processing using a
gas containing oxygen and at least one of carbon fluoride, nitrogen
fluoride, sulfur fluoride, and ammonia.
20. The method according to claim 13, wherein the dopant is at
least one of phosphorus, arsenic and boron.
21. The method according to claim 13, wherein the ashing comprises
a plasma processing using a microwave plasma.
22. The method according to claim 13, wherein the removal of the
residue comprises a plasma processing using a microwave plasma.
23. The method according to claim 21 or 22, wherein the microwave
plasma is generated by radiating microwaves via a microwave antenna
having a plurality of slots provided in a conductor plate.
24. The method according to claim 13, wherein the step of ashing is
carried out in such a state that the processing article is not in
contact with a heater, and wherein the step of removal of the
residue is carried out in such a state that the processing article
is in contact with a heater.
25. A method of producing a semiconductor device comprising the
steps of: forming a photoresist pattern on a surface of a
substrate; implanting a dopant in the substrate using the
photoresist pattern as a mask; ashing and removing a
dopant-implanted photoresist on the surface of the substrate at a
first temperature; and removing a dopant-containing residue of the
photoresist at a second temperature higher than the first
temperature.
26. The method according to claim 25, wherein the step of ashing
and removal comprises ashing using a plasma of a gas not containing
fluorine.
27. The method according to claim 25, wherein the step of removal
of the residue comprises a processing using a gas containing at
least one of fluorine and hydrogen.
28. The method according to claim 25, wherein the step of removal
of the residue comprises a processing using a gas containing oxygen
and at least one of fluorine and hydrogen.
29. The method according to claim 25, wherein the step of ashing
and removal comprises ashing using a plasma of a first gas not
containing fluorine, and wherein the step of removal of the residue
comprises a processing using a second gas containing at least one
of fluorine and hydrogen.
30. The method according to claim 25, wherein the step of ashing
and removal comprises ashing using a plasma of a first gas not
containing fluorine, and wherein the step of removal of the residue
comprises a processing using a second gas containing oxygen and at
least one of fluorine and hydrogen.
31. The method according to claim 25, wherein the step of ashing
and removal comprises ashing using a plasma of oxygen, and wherein
the step of removal of the residue comprises a processing using a
gas containing oxygen and at least one of carbon fluoride, nitrogen
fluoride, sulfur fluoride, and ammonia.
32. The method according to claim 25, wherein the dopant is at
least one of phosphorus, arsenic and boron.
33. The method according to claim 25, wherein the ashing comprises
a plasma processing using a microwave plasma.
34. The method according to claim 25, wherein the removal of the
residue comprises a plasma processing using a microwave plasma.
35. The method according to claim 33 or 34, wherein the microwave
plasma is generated by radiating microwaves via a microwave antenna
having a plurality of slots provided in a conductor plate.
36. The method according to claim 25, wherein the step of ashing is
carried out in such a state that the processing article is not in
contact with a heater, and wherein the step of removal of the
residue is carried out in such a state that the processing article
is in contact with a heater.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a method of producing a
semiconductor device or the like as well as a processing method of
removing a photoresist on a substrate used for the method, a
residue thereof, or the like and particularly, relates to a
processing method of removing a residue which results from ion
implantation of a dopant or the like and is difficult to ash
(hereinafter simply referred to as "nonashable residue").
[0003] 2. Related Background Art
[0004] In the production process for a semiconductor device, a
photoresist as a photosensitive resin is widely used as a masking
material for selective etching and local ion implantation to form a
device structure. The corresponding photoresist needs to be removed
after various processes utilizing this, and in recent years, is
generally removed by oxidization and ashing through dry processing
with oxidation action mainly using oxygen plasma, oxygen radicals,
ozone, and so on.
[0005] As a method of removing a photoresist as an organic
substance consisting mainly of carbon and hydrogen, a technique is
widely used in which the photoresist is exposed to oxygen as
activated by electric discharge or irradiation with ultra violet
and is gasified through the oxidation action into steam, carbon
dioxide, carbon monoxide, etc., thus effecting ashing and
removal.
[0006] On the other hand, in the case where a photoresist is used
as a mask for ion implantation of a dopant, etc., the resist, the
surface of which is modified by the energy of implanted ions, will
be difficult to remove by oxidation, so that the processing
efficiency decreases significantly. In addition, it is known that,
when an ion implanted photoresist is heated to 150.degree. C. to
250.degree. C. as the normal ashing temperature, the phenomena
(popping) that the surface modified layer bursts by steam of an
organic solvent generated from an unmodified layer in a lower
portion of the photoresist to form flake-shaped particles to be
scattered around, is observed, so that the wafer is contaminated.
Moreover, since dopant ions such as As, P, B, etc. do not form any
substance of a high vapor pressure by oxidation, oxides of the ions
will remain on the wafer after the resist has been ashed and
removed by oxygen-based active species and needs to be removed by
subsequent wet processing.
[0007] For the purpose of removing the above mentioned resist which
is generated after ion implantation and is difficult to ash, there
have hitherto been proposed a method in which after a modified
layer of the resist surface is removed while hydrogenating and
removing the dopant ions with a hydrogen plasma or steam plasma, an
underlying unmodified layer is ashed and removed with an oxygen
plasma, a method in which the resist is ashed and remove with a
plasma of a mixed gas obtained by adding to oxygen gas a gas
containing fluorine having a function to increase the ashing rate
and to remove the implanted ion species, or the like.
[0008] In addition, Japanese Patent Application Laid-Open No.
5-275326 discloses a method in which after processing using oxygen
and CF.sub.4, a further processing is effected using oxygen and
nitrogen, and Japanese Patent Application Laid-Open No. 6-104223
discloses a method in which after processing using oxygen and
nitrogen, a further processing is effected using oxygen and
SF.sub.4. Moreover, Japanese Patent Application Laid-Open No.
5-160022 discloses a method in which a photoresist is ashed with an
oxygen plasma, and a residue is then ashed with a hydrogen
plasma.
[0009] However, in the case where a modified layer generated by ion
implantation is removed with a hydrogen plasma or steam plasma, the
processing efficiency generally becomes small due to its low
reaction rate. Moreover, it is necessary to sufficiently raise the
temperature of an article to be processed (hereinafter referred to
as "processing article") in order to increase the reaction rate, so
that the popping phenomenon is apt to take place more easily.
[0010] In a processing with a plasma of a mixed gas formed by
adding to oxygen a gas containing fluorine as a halogen which is an
example of the gas containing halogen, the processing efficiency is
improved by the function of generated fluorine ions and fluorine
radicals, compared with the case of using an oxygen plasma only.
However, since low temperature processing is apt to give rise to a
photoresist residue, in order to avoid this, it is necessary to
effect processing at a high temperature which is apt to cause the
popping.
[0011] In view of the problems as described above, in the actual
producing process, after ashing with oxygen has been effected,
oxides of a dopant remaining on a wafer as a processing article are
cleaned and removed in a subsequent wet processing.
SUMMARY OF THE INVENTION
[0012] An object of the present invention is to provide a
processing method that can remove a foreign matter on a surface of
a processing article at a high efficiency without leaving any
residue such as an oxide of an ion implanted dopant.
[0013] According to a first aspect of the present invention, there
is provided a method of removing a residue comprising ashing and
removing a dopant-implanted photoresist to expose a surface of a
processing article and then removing a dopant-containing residue of
the photoresist remaining on the surface of the processing
article,
[0014] wherein the dopant-containing residue is removed at a
temperature higher than the temperature at which the photoresist is
ashed and removed.
[0015] According to a second aspect of the present invention, there
is provided a method of processing an article comprising the steps
of:
[0016] ashing and removing a dopant-implanted photoresist on a
surface of an article at a first temperature; and
[0017] removing a dopant-containing residue of the photoresist at a
second temperature higher than the first temperature.
[0018] According to a third aspect of the present invention, there
is provided a method of producing a semiconductor device comprising
the steps of:
[0019] forming a photoresist pattern on a surface of a
substrate;
[0020] implanting a dopant in the substrate using the photoresist
pattern as a mask;
[0021] ashing and removing a dopant-implanted photoresist on the
surface of the substrate at a first temperature; and
[0022] removing a dopant-containing residue of the photoresist at a
second temperature higher than the first temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a flow chart showing the processing method of the
present invention;
[0024] FIGS. 2A, 2B and 2C are schematic sectional views showing
the processing according to the present invention;
[0025] FIG. 3 is a sectional view showing an example of a plasma
processing apparatus used in the present invention;
[0026] FIG. 4 is a sectional view showing another example of a
plasma processing apparatus used in the present invention; and
[0027] FIGS. 5A, 5B, 5C, 5D and 5E are schematic views showing the
method of producing a semiconductor device according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] FIG. 1 is a flow chart showing the processing method of the
present invention, and FIGS. 2A, 2B and 2C are schematic sectional
views showing the processing according to the present
invention.
[0029] A processing article such as a silicone wafer is denoted as
1, a photoresist in which a dopant such as phosphorus, arsenic,
boron, etc. has been ion implanted is denoted as 2, and a residue
containing an oxide of the dopant such as phosphorus oxide and
arsenic oxide, boron oxide, etc. is denoted as 3.
[0030] In a step S1, the dopant-implanted photoresist 2 is ashed
and removed so that a surface of the processing article 1 is
exposed.
[0031] Thereafter, in a step S2, the dopant-containing residue 3
remaining on the surface of the processing article 1 is
removed.
[0032] At this time, the residue 3 containing the dopant is removed
at a temperature T2 higher than the temperature of the step S1,
i.e., a temperature T1 when ashing and removing the
photoresist.
[0033] Thus, a highly clean surface of the processing article is
obtained.
[0034] Using a low temperature in the step S1 suppresses popping,
while using a high temperature in the step S2 improves removal
efficiency of the dopant oxide.
[0035] The temperature of a processing article in the step S1 is
preferably a temperature lower than 150.degree. C., specifically
130.degree. C. or lower, and more preferably 120.degree. C. or
lower.
[0036] The temperature of a processing article in the step S2 may
be any temperature higher than the temperature of the processing
article in the step S1, and more preferably 150.degree. C. or
higher, and most preferably 200.degree. C. or higher.
[0037] In the step S1, an oxidizing gas (a first gas) is used to
ash a photoresist. It is preferable to carry out ashing using a
plasma of a gas not containing fluorine so as not to damage a
surface of the processing article. The term "gas not containing
fluorine" as used herein is intended to encompass those gases to
which a fluorine-based gas is not added intentionally. Therefore,
those gases in which fluorine is detected at the so-called
background level or contamination level may be used in the present
invention. As the first gas used in the step S1, there may be
included oxygen gas with an oxygen concentration of 100%, a mixed
gas of oxygen gas and an inert gas (with any oxygen concentration),
or the like., As the inert gas, rare gases such as helium, argon,
neon, xenon, krypton, etc. and nitrogen gas are used. In addition,
water, nitrogen oxide, etc. may be added as the occasion
demands.
[0038] The gas used in the step S2 includes a gas containing at
least one of fluorine and hydrogen, more specifically carbon
fluoride, nitrogen fluoride, ammonia, sulfur fluoride, fluorine,
hydrogen, and water. If necessary, they may be mixed with oxygen
gas or an inert gas when used. Among others, carbon fluoride,
nitrogen fluoride, sulfur fluoride, and ammonia are preferable.
Oxygen has not only a function of serving as a diluent gas, but
also a function of reacting with carbon or nitrogen generated from
carbon fluoride, nitrogen fluoride or ammonia to form carbon
dioxide gas or nitrogen oxide gas thus removing remaining carbon or
remaining nitrogen from a processing space quickly.
[0039] In the steps S1 and S2, it is preferable to effect plasma
processing by use of a microwave plasma of the above mentioned
first or second gas.
[0040] As the second gas, among others, CF.sub.4, C.sub.2F.sub.6,
C.sub.3F.sub.8, C.sub.3F.sub.6, NF.sub.3, SF.sub.6, NH.sub.3, etc.
are preferably used. These may be mixed with oxygen when used. Of
the photoresist into which phosphorus, arsenic, boron, etc. have
been implanted, the organic component is oxidized and removed in
the first step, and thereafter, in the second step, oxides
remaining on the processing article are mainly removed. The dopant
such as phosphorus, arsenic, boron, or the like is converted by the
action of active species such as fluorine ions, fluorine radicals,
hydrogen ions, hydrogen radicals, etc. into a volatile fluoride or
hydride to be removed from the surface of the processing article. A
carbon fluoride based gas or nitrogen fluoride based gas does not
contain any element to cause undesired contamination and has a good
efficiency in generating fluorine active species, which allows
desired effects to be exhibited with less addition amount thereof,
so that the surface of the processing article will not be damaged
seriously. In addition, ammonia is very effective, since it can be
handled more easily than hydrogen and can generate hydrogen active
species efficiently because of its low N-H binding energy, and
since thus generated NH radicals have long lifetime and can
therefore reduce the oxides of the dopant efficiently.
[0041] (Embodiment 1)
[0042] FIG. 3 is a sectional view showing a configuration of a
plasma processing apparatus which generates a plasma using
microwaves to plasma process a wafer as the processing article.
Reference numeral 101 denotes a vacuum container, which together
with a dielectric window 107 for microwave introduction forms a
processing chamber for plasma generation therein, which is
exhausted through an exhaust opening 102 with a vacuum pump (not
shown). A microwave wave guide, which is denoted as 108, guides to
the vacuum container microwaves generated in a microwave generator
(not shown). A gas inlet tube, which is denoted as 106, supplies
the processing chamber with a gas for plasma processing at a
predetermined flow rate supplied from a gas supplying system (not
shown). In the drawing, a wafer having a photoresist into which
phosphorus (P) has been ion implanted is denoted as W and mounted
on a heater 105.
[0043] The wafer as the processing article is disposed in a
position above the heater set at a processing temperature in the
ashing apparatus shown in FIG. 3 with a wafer lifting pin or the
like to lift the wafer in a floating state. Specifically, after the
chamber has been sealed and the inside thereof has been exhausted
to substantial vacuum with a vacuum pump (not shown) connected to
the chamber, the wafer is disposed on the heater by operating the
lift pin or the like. This makes it possible to maintain the wafer
temperature lower than the heater temperature by the vacuum
insulation effect. In the actual determination, the wafer
temperature at this time was about 80.degree. C.
[0044] For the purpose of removing organic components of the
resist, oxygen gas at a predetermined flow rate shown below is
introduced into the chamber and the processing is started under the
predetermined conditions shown below, and the time taken until the
end point of ashing determined by an end point detecting device
with a plasma monitor (not shown) is measured. After a period of
time about 1.5 to 2 times the measured time has elapsed, the
processing is completed. Thereafter, the inside of the chamber is
exhausted to a substantial vacuum.
[0045] This will completely remove 95% or more of the photoresist
on the wafer to such an extent that no photoresist can be observed
with naked eyes.
[0046] Active species for ashing can be generated highly
efficiently not only with the apparatus shown in FIG. 3 but also
with a microwave plasma processing apparatus having a slotted
conductor plate. When a microwave plasma processing apparatus is
used in which a plate-like antenna or radial line slot antenna
formed by providing a plurality of slots in a plate-like H-plane of
an endless annular waveguide is employed, it is possible to
generate the active species more efficiently. Such apparatuses are
disclosed in Japanese Patent No. 2925535 and U.S. Pat. No.
5,034,086.
[0047] The typical processing conditions for this first step are as
follows.
[0048] Gas/Flow Rate: O.sub.2/1000 sccm
[0049] Processing Pressure: 1 Torr (approximately 133 Pa)
[0050] Wafer Temperature of 80.degree. C.<Heater Temperature of
250.degree. C.
[0051] Next, in order to break the vacuum insulation and to heat
the wafer to the heater temperature, oxygen is introduced into the
chamber until the inside pressure reaches substantially atmospheric
pressure. However, introduction of any other gas instead of oxygen
will not give rise to any particular problem.
[0052] Next, after the inside of the chamber has been exhausted
again, the second step is carried out. Here, for the purpose of
removing a residue not removed only by oxygen and remaining on the
wafer, a mixture gas of oxygen/CF.sub.4 mixed at a predetermined
ratio is introduced at a predetermined flow rate into the chamber,
and the processing is started under the predetermined conditions
and is continued for about 15 seconds. This processing removes the
residue comprised of oxides of the dopant as left after the first
step processing.
[0053] The processing conditions for this second step are, for
example, as follows.
[0054] Gas/Flow Rate: O.sub.2+CF.sub.4/500 sccm+2 sccm
[0055] Processing Pressure: 0.6 Torr (approximately 80 Pa)
[0056] Wafer Temperature: 250.degree. C.
[0057] Microwave Output: 1500 W
[0058] Processing Time: approximately 15 seconds.
[0059] (Embodiment 2)
[0060] After a wafer as the processing article is disposed on the
heater set at a processing temperature (a low temperature) in the
ashing apparatus as shown in FIG. 3 to allow the wafer temperature
to reach the processing temperature, the chamber is sealed and the
inside of the chamber is exhausted to substantial vacuum with a
vacuum pump (not shown) connected to the chamber.
[0061] For the purpose of removing organic components of the
resist, oxygen gas at a predetermined flow rate shown below is
introduced into the chamber and the processing is started under the
predetermined conditions shown below, and the processing is
continued for a period of time which is about twice the time taken
until the end point of ashing determined by an end point detecting
device with a plasma monitor (not shown).
[0062] The processing conditions for the first step are as
follows.
[0063] Gas/Flow Rate: O.sub.2/100 sccm
[0064] Processing Pressure: 0.1 Torr (approximately 13.3 Pa)
[0065] Wafer Temperature: 80.degree. C.
[0066] Microwave Output: 1500 W
[0067] Processing Time: approximately 1.5 to 2 times the time
period until the emission spectrum or the emission intensity
changes.
[0068] Afterwards, the chamber is opened to atmosphere and the
wafer is taken out. The photoresist on the wafer is removed by 5%
or more thereof to such clearness that it can no longer be observed
with naked eyes.
[0069] After the wafer as the processing article is disposed on the
heater set at a processing temperature (a high temperature) in the
ashing apparatus as shown in FIG. 3 to allow the wafer temperature
to reach the processing temperature, the chamber is sealed and the
inside of the chamber is exhausted to substantial vacuum with a
vacuum pump (not shown) connected to the chamber. At this time, the
processing may either be carried out in another chamber or be
carried out in the same chamber with the set temperature
changed.
[0070] For the purpose of removing a residue left after the removal
of the organic components in the resist in the first step
processing, a mixture gas of oxygen/CF.sub.4 mixed at a
predetermined ratio is introduced at a predetermined flow rate into
the chamber, and the processing is started under the predetermined
conditions and is continued for about 15 seconds. This processing
removes the residue comprised of oxides of the dopant to provide a
clean surface free from the residue.
[0071] The processing conditions for the second step are as
follows.
[0072] Gas/Flow Rate: O.sub.2+CF.sub.4/500 sccm+2 sccm
[0073] Processing Pressure: 0.6 Torr (approximately 80 Pa)
[0074] Wafer Temperature: 250.degree. C.
[0075] Microwave Output: 1500 W
[0076] Processing Time: approximately 15 seconds.
[0077] In this method, since the processing temperature in the
first step carried out with a non-fluoride oxidizing gas is set at
a temperature lower than the temperature in the second step, namely
a temperature sufficiently lower than 150.degree. C., popping was
suppressed.
[0078] (Embodiment 3)
[0079] The plasma processing apparatus shown in FIG. 4 is the same
as the apparatus of FIG. 3 except that a lift pin 109 is added as a
wafer lifting apparatus.
[0080] The wafer as the processing article is disposed in a
position above the heater in the ashing apparatus shown in FIG. 4
with the lifting apparatus in a floating state, the chamber is
sealed and the inside of the chamber is exhausted to substantial
vacuum with a vacuum pump (not shown) connected to the chamber.
[0081] For the purpose of removing organic components of the
resist, oxygen gas at a predetermined flow rate shown below is
introduced into the chamber and the processing is started under the
predetermined conditions shown below, and the processing is
continued for a period of time which is about twice the time taken
until the end point of ashing determined by an. end point detecting
device with a plasma monitor (not shown).
[0082] The processing conditions. for the first step are as
follows.
[0083] Gas/Flow Rate: O.sub.2/100 sccm
[0084] Processing Pressure: 0.1 Torr (approximately 13.3 Pa)
[0085] Heater Temperature: 250.degree. C.
[0086] Microwave Output: 1500 W
[0087] Processing Time: approximately 1.5 to 2 times the time
period until the emission spectrum or the emission intensity
changes.
[0088] The heater temperature at this time is 250.degree. C.
However, since the wafer itself is floating above the heater with
the lift pin, the temperature of the wafer will be sufficiently
lower than 150.degree. C. Thereby, 95% or more of the photoresist
can securely be removed.
[0089] After the first step, the wafer is lowered to be disposed on
the heater with the lift apparatus, and a gas such as oxygen, etc.
is introduced into the chamber up to approximate atmospheric
pressure to heat the wafer to approximately reach 250.degree.
C.
[0090] For the purpose of removing a residue left after the removal
of the organic components in the resist in the preceding step
processing, a mixture gas of oxygen/CF.sub.4 mixed at a
predetermined ratio is introduced at a predetermined flow rate into
the chamber, and the processing is started under the predetermined
conditions and is continued for about 15 seconds. This makes it
possible to carry out the same processing as that of Embodiment 2
efficiently in a shorter time period.
[0091] The processing conditions for the second step are as
follows.
[0092] Gas/Flow Rate: O.sub.2+CF.sub.4/500 sccm+2 sccm
[0093] Processing Pressure: 0.6 Torr (approximately 80 Pa)
[0094] Heater Temperature (Processing Article Temperature):
250.degree. C.
[0095] Microwave Output: 1500 W
[0096] Processing Time: approximately 15 seconds.
[0097] Fluorine active species generated when a gas containing
fluorine is subjected to plasma formation will corrode silicon
constituting the processing article and silicon oxides if the
processing takes a long time. Moreover, if ashing is carried out
with addition of a gas containing fluorine, the resist may be
fluorinated to be difficult to ash. The Embodiments described above
do not give rise to such problems.
[0098] (Embodiment 4)
[0099] Next, the producing method of a semiconductor device
according to the present invention will be described.
[0100] A semiconductor substrate such as an Si wafer is prepared as
the processing article 1.
[0101] As shown in FIG. 5A, a surface of the processing article 1
is coated with a photoresist material 4.
[0102] As shown in FIG. 5B, the photoresist material is exposed to
be developed, thus providing a photoresist pattern 2.
[0103] As shown in FIG. 5C, a dopant such as phosphorus, arsenic,
boron, or the like is implanted using the photoresist pattern 2 as
a mask. In a portion not covered with the photoresist pattern, a
doped layer 5 is formed. In addition, the dopant is incorporated
into the photoresist pattern.
[0104] The processing in the first step as described in Embodiments
1 to 3 is carried out to ash and remove the photoresist pattern 2.
This leaves a residue 3 consisting of oxides of the dopant on the
surface of the processing article 1 as shown in FIG. 5D
[0105] Subsequently, performing the above described second step
results in removal of the residue 3 as shown in FIG. 5E.
[0106] Thus, the doped layer 5 of the semiconductor device can be
formed.
[0107] [Example]
[0108] According to the procedure described in Embodiment 3, the
photoresist having P ions implanted therein was ashed and the
residue was then removed, with the result that the residue
consisting of dopant oxides was scarcely left.
[0109] According to the Embodiments as described, without leaving
any residue of modified organic components, highly efficient ashing
for removal can be performed, and corrosion of a surface of the
processing article as the underlying material of the organic
substance to ash can be suppressed and the cause of particle
contamination can be also suppressed. In addition, wet cleaning for
removal of a residue required for the conventional processing can
be omitted.
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