U.S. patent application number 10/447472 was filed with the patent office on 2004-01-15 for plasma film-forming apparatus and cleaning method for the same.
This patent application is currently assigned to ULVAC, Inc.. Invention is credited to Asari, Shin, Hashimoto, Masanori, Hirata, Masayasu, Ishikawa, Michio, Kurata, Takaomi, Mori, Katsuhiko, Tsuji, Naoto, Yamauchi, Kazuaki.
Application Number | 20040007247 10/447472 |
Document ID | / |
Family ID | 18739717 |
Filed Date | 2004-01-15 |
United States Patent
Application |
20040007247 |
Kind Code |
A1 |
Asari, Shin ; et
al. |
January 15, 2004 |
Plasma film-forming apparatus and cleaning method for the same
Abstract
In a plasma film-forming apparatus which includes a film-forming
chamber in which a substrate is arranged, a film-forming gas
introducing pipe connected to a supply source of a film-forming gas
at its first end, a shower plate through numerous holes of which a
second end of said film-forming gas introducing pipe communicate
with said film-forming chamber, film-gas exciting means for
exciting film-forming gas introduced through said shower plate into
said film-forming chamber, to form a film on the surface of said
substrate with the chemical reaction, radicals-producing means
which excites said cleaning gas and produces radicals, and
cleaning-gas introducing means which introduces said cleaning gas
containing said radicals into said film-forming chamber, the
improvement in which said cleaning-gas introducing means
communicate directly with said film-forming chamber.
Inventors: |
Asari, Shin; (Chiba-ken,
JP) ; Tsuji, Naoto; (Chiba-ken, JP) ; Kurata,
Takaomi; (Chiba-ken, JP) ; Yamauchi, Kazuaki;
(Chiba-ken, JP) ; Hashimoto, Masanori; (Chiba-ken,
JP) ; Ishikawa, Michio; (Chiba-ken, JP) ;
Hirata, Masayasu; (Chigasaki-shi, JP) ; Mori,
Katsuhiko; (Chigasaki-shi, JP) |
Correspondence
Address: |
Floyd B. Carothers
CAROTHERS AND CAROTHERS
Suite 500
445 Fort Pitt Boulevard
Pittsburgh
PA
15219
US
|
Assignee: |
ULVAC, Inc.
Chigasaki-shi
JP
|
Family ID: |
18739717 |
Appl. No.: |
10/447472 |
Filed: |
May 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10447472 |
May 28, 2003 |
|
|
|
09932047 |
Aug 17, 2001 |
|
|
|
Current U.S.
Class: |
134/1.1 |
Current CPC
Class: |
H01J 37/32862 20130101;
C23C 16/345 20130101; C23C 16/4405 20130101; C23C 16/402 20130101;
H01J 37/3244 20130101 |
Class at
Publication: |
134/1.1 |
International
Class: |
C25F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2000 |
JP |
250080/2000 |
Claims
What is claimed is:
1. In a cleaning method for a plasma film-forming apparatus in a
film-forming operation wherein a film-forming gas is introduced
through a shower plate having numerous holes into a film-forming
chamber, the introduced gas is excited and forms a film with the
chemical reaction on a surface of a substrate arranged in said
film-forming chamber, and in a cleaning operation, a cleaning-gas
containing radicals produced by exciting said cleaning-gas is
introduced into said film-forming chamber and cleans said
film-forming chamber by chemical reaction of said radicals and
removes materials to be cleaned; the improvement comprising
introducing said cleaning gas containing said radicals directly
into said film-forming chamber.
2. A cleaning method for a plasma film-forming chamber according to
claim 1, including in said cleaning operation, introducing inert
gas into said film-forming chamber in addition to said cleaning gas
containing radicals, exciting said inert gas to inert ions, and
cleaning said film-forming chamber with the chemical reaction of
said radicals and with the sputtering of said inert gas ions.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a plasma film-forming apparatus
and a cleaning method for cleaning the plasma film-forming
apparatus.
[0003] 2. Description of the Prior Art
[0004] FIG. 1 shows a plasma film-forming apparatus 1 of the prior
art. It is an apparatus to form a film on a substrate 9 by a plasma
CVD (Chemical Vapor Deposition) method. A cathode electrode 4 is
arranged on the upper wall of a vacuum tank 2. An anode electrode 3
is arranged opposite to the cathode electrode 4, in a film-forming
chamber 10 of the vacuum tank 2. The cathode electrode 4 is
connected to a high frequency electric power source 8. The anode
electrode 3 is connected to the earth. It functions also as a
supporter for substrate. The substrate 9 is mounted on the anode
electrode 3.
[0005] The cathode electrode 4 is dish-shaped. A gas-introducing
pipe 13 is connected to a central hole of the upper wall of the
cathode electrode 4. A shower plate 5 is fixed to a lower end of
the cathode electrode 4. Numerous small holes are made in the
shower plate 5 which is facing to the substrate 9.
[0006] One end of a film-forming gas introducing pipe 6 is
connected to the gas-introducing pipe 13. Another end of the
film-forming gas-introducing pipe 16 is connected to a not-shown
film-forming gas supply source. A radicals producing source 11 is
connected to one end of a gas-introducing pipe 12. Another end of
the gas-introducing pipe 12 is connected to a not-shown cleaning
gas sipply source. The radicals producing source 11 is further
connected to the pipe 13.
[0007] Next, operations of the above described plasma film-forming
apparatus 1 will be described.
[0008] For example, there will be described a case of forming a
film of SiNx on the substrate 9. First, the film-forming chamber 10
is evacuated through an exhaust port 7 and so is put under the
lower pressure. For example, SiH.sub.4 gas and NH.sub.3 gas are
introduced onto the shower plate 5 through the film-forming gas
introducing pipe 6 and the gas introducing pipe 13. They are
ejected through the numerous holes of the shower plate 5 uniformly
into the film-forming chamber 10 and toward the substrate 9.
[0009] Next, a high frequency electric power is supplied to the
cathode electrode 4 form the high frequency power source 8, to
decompose and make the introduced gases to react on each other
gases in the film-forming chamber 10. Thus, a film of SiNx is
formed on the substrate 9.
[0010] The above film-forming operations are repeated, and so SiNx
films are adhered and piled onto the shower plate 5, anode
electrode 3, cathode electrode 4 and inner walls of the vacuum tank
2 besides the substrate 9. The SiNx films on the above portions
besides the substrate 9 should be removed (cleaned).
[0011] Next, there will be described cleaning operations of the
interior of the film-forming chamber 10.
[0012] As on the film-forming operation, the film-forming chamber
10 is evacuated through the exhaust port 7 and so put under the
lower pressure. For example, NF.sub.3 gas is supplied into the
radicals producing source 11. Microwave is applied to the NF.sub.3
gas there, so that fluorine free radicals are produced there.
NF.sub.3 gas including fluorine free radicals are introduced into
the film-forming chamber 10 through the gas-introducing pipe 13 and
the shower plate 5.
[0013] Then, fluorine radicals react chemically on the materials
(SiNx film) to be cleaned. The SiNx films piled on the inner wall
of the vacuum tank 2 are removed. The removed SiNx materials are
discharged through the exhaust port 7 together with the cleaning
gas.
[0014] The method that the radicals for cleaning are thus
previously produced and then introduced into the film-forming
chamber 10, has the advantage that the plasma damage of the shower
plate 5 is decreased, in comparison with the method that free
radicals for cleaning are produced in the film-forming chamber 10
by the high frequency electric power applied to the cathode
electrode 4 from the high frequency power source 8, as on the
film-forming operation. introduced into the film-forming chamber 5,
most of the radicals are dissipated, since the passing rate of the
shower plate 5 having numerous small holes is low. Thus there is
the problem that the cleaning rate is lowered.
[0015] Further, in consideration of the problem that most of the
radicals are dissipated through in the shower plate 5, a very high
frequency microwave such as 2.45 GHz is applied to the
radicals-producing source 11 to produce more radicals, in some
cases. However, such method requires high cost.
SUMMARY OF THE INVENTION
[0016] Accordingly, it is an object of this invention to provide a
plasma film-forming apparatus and the cleaning method that the
dissipation of the radicals to be introduced into the film-forming
chamber can be prevented.
[0017] Another object of this invention is to provide a plasma
film-forming apparatus and the cleaning method that the radicals as
the cleaning gas produced outside the film-forming chamber, can be
effectively used for cleaning the film-forming chamber.
[0018] In accordance with one aspect of the invention, in a plasma
film-forming apparatus which includes a film-forming chamber in
which a substrate is arranged, a film-forming gas introducing pipe
connected to a supply source of a film-forming gas at its first
end, a shower plate through numerous holes of which a second end of
said film-forming gas introducing pipe communicate with said
film-forming chamber, film-gas exciting means for exciting
film-forming gas introduced through said shower plate into said
film-forming chamber, to form a film on the surface of said
substrate with the chemical reaction, radicals-producing means
which excites said cleaning gas and produces radicals, and
cleaning-gas introducing means which introduces said cleaning gas
containing said radicals into said film-forming chamber, the
improvement in which said cleaning-gas introducing means
communicate directly with said film-forming chamber. film-forming
chamber.
[0019] In accordance with another aspect of the invention, in a
cleaning method of a plasma film-forming apparatus which, in the
film-forming operation, introduces a film-forming gas through a
shower plate having numerous holes into a film-forming chamber,
excites the introduced gas and forms a film, with the chemical
reaction, on a surface of substrate arranged in said film-forming
chamber, and in the cleaning operation, introduces a cleaning-gas
containing radicals produced by exciting of said cleaning-gas, into
said film-forming chamber and cleans said film-forming chamber by
chemical reaction of said radicals and removes materials to be
cleaned, the improvement in which said cleaning gas containing said
radicals is introduced directly into said film-forming chamber.
BRIFE DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a vertical cross-sectional view of a plasma
film-forming apparatus of the prior art;
[0021] FIG. 2 is a vertical cross-sectional view of a plasma
film-forming apparatus according to first and second embodiment of
this invention;
[0022] FIG. 3 is vertical cross-sectional view of a plasma
film-forming apparatus according to a third embodiment of this
invention;
[0023] FIG. 4 is a cross-sectional view taken along the line iv-iv
in FIG. 3;
[0024] FIG. 5 is a graph for showing the comparisons of the
cleaning rates of SiNx films between the prior art and the first
embodiment of this invention; and
[0025] FIG. 6 is a graph for showing the cleaning rates of SiOx
film by the second embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Next, embodiments of this invention will be described with
reference to the drawings. The parts corresponding to the parts of
the above prior art are denoted by the same reference numerals, the
detailed description of which will be omitted.
[0027] FIG. 2 shows a plasma (CVD) film-forming apparatus 20
according to a first embodiment of this invention. A cathode
electrode 4 connected to a high frequency electric power source 8
is arranged in the upper wall of a vacuum tank 2. An anode
electrode 3 supporting a substrate 9 and connected to the earth is
arranged opposite to the cathode electrode 4 in the film-forming
chamber 10.
[0028] A film-forming gas introducing pipe 15 is connected to a
central hole of the upper wall of the cathode electrode 4. A shower
plate 5 having numerous small holes is fixed to the lower end of
the cathode electrode 4, opposite to the substrate 9.
[0029] A radicals-producing means 21 is arranged outside the vacuum
tank 2. An input side of the radicals-producing means 21 is
connected through a conduit 22 to a not-shown cleaning gas supply
source. The radicals-producing means 21 consists of a chamber for a
cleaning gas introduced from the conduit 22 and a high frequency
electric power source applying a high frequency electric power to
the contained cleaning gas in the chamber for producing
radicals.
[0030] An output side of the radicals-producing means 21 is
connected through a valve 24 to one end of a pipe 23 for
introducing a cleaning gas. Another end of the pipe 23 is connected
to a hole made in the side wall of the vacuum tank 2, positioning
between the shower plate 5 and the anode electrode 3. Thus, the
pipe 23 for introducing the cleaning gas directly communicates with
the inside of the film-forming chamber 10.
[0031] In the film-forming operation, the film-forming chamber 10
is evacuated through the exhaust port 7 and is put under the lower
pressure, as in that the prior art. A film-forming gas (SiH.sub.4
gas, NH.sub.3 gas) is supplied through the film-forming gas
introducing pipe 15 onto the shower plate 5. It is ejected into the
film-forming chamber 10 from the numerous small holes of the shower
plate 5. A high frequency electric power is supplied to the cathode
electrode 4 by the high frequency electric power source 8 to
decompose and make the introduced film-forming gas reacting. Thus,
a film of SiNx is formed on the substrate 9.
[0032] In the cleaning operation of the film-forming chamber 10,
the film-forming chamber 10 is evacuated through the exhaust port 7
and put under the lower pressure. Then, the cleaning gas such as
NF.sub.3 gas is supplied to the radicals producing source 21 to
which a high frequency electric power (400 kHz) is supplied.
Fluorine radicals are produced in the radicals-producing source 21.
The valve 24 is opened to introduce directly the NF.sub.3 gas
containing the fluorine radicals into the film-forming chamber 10
through the gas-introducing pipe 23 as the means for introducing
the cleaning gas. The fluorine radicals react on the SiNx film to
be cleaned. Thus, the interior of the film-forming chamber 10 is
cleaned. Thus, in this embodiment, the radicals pass not through
the shower plate 5, but directly introduced into the film-forming
chamber 10 to be cleaned. Thus, most of the radicals can be
prevented from dissipating before introduced into the film-forming
chamber 10. The film-forming chamber 10 can be effectively cleaned.
As shown in FIG. 5, the cleaning rate of the SiNx according to this
embodiment is higher about twenty times than the prior art method
in which the radicals pass through the shower plate 5.
[0033] Further, the micro-wave generator of a high frequency such
as 2.45 GHz was used for producing radicals in the
radicals-producing means of the prior art. It is very expensive. In
the embodiment of this invention, it is not necessary to use such
as an expensive high-frequency electric power source. A high
frequency electric power source of 400 HKz, which takes lower cost,
can be used to produce radicals. The experimental results as shown
in FIG. 3 were obtained with the electric power source of 400 KHz.
The frequency is not limited to 400 KHz. Similar effects can be
obtained within the range of 100 to 1000 KHz. A high frequency
electric power source of lower frequency than 1000 KHz takes low
cost. Accordingly, a plasma film-forming apparatus using such a
high frequency electric power source takes lower cost, in
comparison with the prior art plasma film-forming apparatus.
[0034] Further, in the embodiment of this invention, polyfluoro
ethylene (trade name-Tefron) is coated on the inner surface of the
cleaning gas introducing pipe 23. Accordingly, the radicals can be
transported through the cleaning gas introducing pipe 23 without
the dissipation. Thus, the life of the produced radicals can be
longer.
[0035] Sufficient cleaning rate can be obtained for SiNx film, even
only by radicals. However, radicals are very directional.
Accordingly, there is the possibility that the films are not
removed around the shower plate 5 and anode electrode 3, when only
the radicals are used for cleaning. Accordingly, in the cleaning
operation, Argon gas as inert gas for sputter cleaning is
introduced into the film-forming chamber 10 besides NF.sub.3 gas
including fluorine radicals. A high frequency electric power of
27.12 MHz frequency and 0.15 W/cm.sup.2 electric power density is
applied to the introduced gases from the high frequency electric
power source 8 which is used also for film-forming.
[0036] Thus, the argon gas is electrically devided into Ar ions
(Ar.sup.+) and electrons. The film-forming chamber 10 is cleaned
both with the chemical reaction by radicals and with Ar ions
sputtering. It can be more uniformly cleaned, and the cleaning
efficiency can be improved. The Ar gas is introduced into the
film-forming chamber 10 through the cleaning gas introducing pipe
23 or through the film-forming gas introducing gas 15. Insteads, it
may be introduced through a special pipe for spluttering gas.
[0037] Next, there will be described a second embodiment of this
invention. SiO.sub.2 film is formed in the same plasma film-forming
apparatus 20 as in the first embodiment. For example, SiH.sub.4 gas
and N.sub.2O gas are used as a film-forming gas. The SiO.sub.2 film
is formed on the substrate 9 in the same manner as the first
embodiment.
[0038] In the cleaning operation of the film-forming chamber 10,
NF.sub.3 gas containing fluorine radicals is directly introduced
into the film-forming chamber 10 from the gas introducing pipe 23.
The fluorine radicals reacts chemically with the SiO.sub.2 film to
be cleaned. Thus, the film-forming chamber 10 is cleaned.
[0039] Although the radicals are effectively introduced into the
film-forming chamber 10, a sufficient cleaning rate cannot be
obtained for SiO.sub.2 film. Accordingly, Ar gas is introduced into
the film-forming chamber 10. The high frequency electric power is
applied to the Ar gas from the cathode electrode 4 by the high
frequency electric power source 8. Ar ions are produced. The
film-forming chamber 10 is cleaned also by the Ar ion
sputtering.
[0040] FIG. 6 shows the comparison results of the cleaning of the
SiO.sub.2 films among the cleaning only by the radicals (fluorine
radicals), the cleaning only by the ions (Ar.sup.+) and the
cleaning by the ions (Ar.sup.+) and radicals. When the film-forming
chamber 10 was cleaned only by the ions, the high frequency
electric power was applied to the cathode electrode 4 at the
frequency of 27.12 MHz and the power density of 0.67W/cm.sup.2.
When the film-forming chamber 10 was cleaned by the radicals and
ions, the high frequency electric power was applied to the cathode
electrode 4 at the same frequency as that of the cleaning only by
the ions, and at the half power density of that of the cleaning
only by the ions.
[0041] The cleaning rate of the cleaning operation only by the
radicals are low. However, that of the cleaning operation by
combination of the radicals and ions is substantially equal to that
of the cleaning operation only by the ions. The required power of
high frequency in the cleaning operation by combination of the
radicals and ions is about half of that in the cleaning operation
only by the ions. Accordingly, the plasma damage to the shower
plate 5 can be reduced, and so the shower plate 5 can be prevented
from being deteriorated.
[0042] Next, there will be described a third embodiment of this
invention. Parts in this embodiment which correspond to those in
the first and the second embodiments, are denoted by the same
reference numerals, the detailed description of which will be
omitted.
[0043] FIG. 3 shows a vertical cross-sectional view of a plasma
film-forming apparatus 30 according to this embodiment. FIG. 4
shows a cross-sectional view taken along the lines IV-IV in FIG. 3.
It is used for a large-sized substrate.
[0044] In the first and the second embodiments as shown in FIG. 2,
the radicals are introduced laterally into the film-forming chamber
10. Accordingly, portions nearer to the outlet of the
gas-introducing pipe 23 are sooner cleaned. When the size of the
substrate 9 is about 400 mm.times.500 mm, there is no problem.
However, when the size of the substrate is large as 730
mm.times.920 mm, the cleaning rate is generally lowered. The
film-forming chamber 10 is large-sized for a large substrate. The
cleaning rates are considerably different between portions near to
the outlet of the gas-introducing pipe 23 and portions farther from
that. Totally, the cleaning rate is lowered.
[0045] In this embodiment, a first cleaning-gas introducing pipe
33a is connected to one side wall 2a of the film-forming chamber
10, and another cleaning-gas introducing pipe 33b is connected to
another side wall 33b of the film-forming chamber 10, which is
facing to the one side wall 2b.
[0046] The cleaning-gas is introduced into the film-forming chamber
10 from the two outlets. As shown in FIG. 3, the first and second
cleaning-gas introducing pipes 33a and 33b are shifted from the
centers of the walls in opposite directions. The cleaning-gas is
more uniformly introduced into the film-forming chamber 10 than in
the case that the cleaning-gas introducing pipes 33a and 33b are
connected to the walls, facing to each other. Of course, they may
be connected to the walls, facing to each other.
[0047] The cleaning rate of the large film-forming chamber 10 with
the arrangement of FIG. 4 is about three times as high as that in
the case that only one cleaning-gas introducing pipe 22 is
connected to the one side wall as in FIG. 2. The high frequency
electric power source of about 100 to 1000 KHz for producing
radicals, is simple in constructions and small-sized in comparison
with the micro-wave generator.
[0048] The price of the former is one third as low as that of the
latter. Accordingly, plural radical-producing sources can be easily
arranged, and the manufacturing cost is not so high.
[0049] While the preferred embodiments have been described,
variations thereto will occur to those skilled in the art within
the scope of the present inventive concepts which are delineated by
the following claims.
[0050] For example, in the above embodiments, NF.sub.3 is used as
the cleaning-gas. However, it is not limited to NF.sub.3, but
CF.sub.4, C.sub.2F.sub.6, C.sub.3F.sub.3, CHF.sub.3, SF.sub.6 etc.
may be used as the cleaning-gas. Inert gas for sputtering cleaning
is not limited to Ar. Further, the film to be formed in the
substrate or to be cleaned, is not limited to SiNx and SiO.sub.2.
Further, the high frequency power to be applied to the cathode
electrode 4, is not limited to the above frequency and to the above
electric power density. Frequency between 10 to 100 MHZ may be
adjusted.
[0051] Electric power density between 0.03 to 0.7 W/cm.sub.2 may be
adjusted.
[0052] In the third embodiment, two cleaning-gas introducing pipes
are connected to the film-forming chamber 10. The number of the
connected pipes is not limited to two, and more than two. The wall
connecting the cleaning-gas introducing pipe, is not limited to the
side wall, and may be upper wall or bottom wall, of the vacuum tank
2.
* * * * *