U.S. patent application number 10/466873 was filed with the patent office on 2004-07-01 for plasma processing device and plasma processing method.
Invention is credited to Abe, Syoichi, Akahori, Takashi, Ashigaki, Shigeo, Chung, Gishi, Inoue, Yoichi, Ishizuka, Shuuichi, Kawamura, Kohei, Miyoshi, Hidenori, Oshima, Yasuhiro, Suzuki, Takashi, Takahashi, Hiroyuki, Takatsuki, Koichi, Yoshitaka, Hiraku.
Application Number | 20040127033 10/466873 |
Document ID | / |
Family ID | 27345786 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127033 |
Kind Code |
A1 |
Takatsuki, Koichi ; et
al. |
July 1, 2004 |
Plasma processing device and plasma processing method
Abstract
That surface of an electrode plate 20 which is opposite to a
susceptor 10 has a projection shape. The electrode plate 20 is
fitted in an opening 26a of shield ring 26 at a projection 20a. At
this time, the thickness of the projection 20a is approximately the
same as the thickness of the shield ring 26. Accordingly, the
electrode plate 20 and the shield ring 26 form substantially the
same plane. The major surface of the projection 20a has a diameter
1.2 to 1.5 times the diameter of a wafer W. The electrode plate 20
is formed of, for example, SiC.
Inventors: |
Takatsuki, Koichi;
(Nirasaki-shi Yamanashi, JP) ; Yoshitaka, Hiraku;
(Tsukui-gun Kanagawa, JP) ; Ashigaki, Shigeo;
(Shiroyama-machi Tsukui-gun Kanagawa, JP) ; Inoue,
Yoichi; (Tokyo, JP) ; Akahori, Takashi;
(Shiroyama-machi Tsukui-gun Kanagawa, JP) ; Ishizuka,
Shuuichi; (Hosaka-cho Nirasaki-shi Yamanashi, JP) ;
Abe, Syoichi; (Shiroyama-machi Tsukui-gun Kanagawa, JP)
; Suzuki, Takashi; (Fujii-cho Nirasaki-shi Yamanashi,
JP) ; Kawamura, Kohei; (Hosaka-cho Nirasaki-shi
Yamanashi, JP) ; Miyoshi, Hidenori; (Hosaka-cho
Nirasaki-shi Yamanashi, JP) ; Chung, Gishi;
(Hosaka-cho Nirasaki-shi Yamanshi, JP) ; Oshima,
Yasuhiro; (Hosaka-cho Nirasaki-shi Yamanashi, JP) ;
Takahashi, Hiroyuki; (Kitagejo-cho Nirasaki-shi Yamanashi,
JP) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Family ID: |
27345786 |
Appl. No.: |
10/466873 |
Filed: |
January 29, 2004 |
PCT Filed: |
January 22, 2002 |
PCT NO: |
PCT/JP02/00428 |
Current U.S.
Class: |
438/689 |
Current CPC
Class: |
H01J 37/32009 20130101;
H01J 37/3244 20130101; H01J 37/32541 20130101 |
Class at
Publication: |
438/689 |
International
Class: |
H01L 021/302; H01L
021/461 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 2001 |
JP |
2001-13574 |
Jan 22, 2001 |
JP |
2001-13572 |
Aug 7, 2001 |
JP |
2001-239720 |
Claims
1. A plasma process system (1) characterized by comprising: a
chamber (2); an electrode plate (20) provided with gas holes (19)
for supplying a process gas into said chamber (2) and having a
projection (20a); and a shield ring (26) having an opening (26a)
which is fitted over said projection (20a) and is constituted by a
ring-like plate member which covers a peripheral portion of said
electrode plate (20) with said projection (20a) and said opening
(26a) fitted together.
2. The plasma process system (1) according to claim 1,
characterized in that said projection (20a) of said electrode plate
(20), in such a state as to be fitted in said opening (26a), forms
a substantially flat surface together with a major surface of said
shield ring (26).
3. A plasma process system (1) characterized by comprising: a first
electrode plate (10) on one surface of which a subject to be
processed is placed; and a second electrode plate (20) connected to
a high-frequency power supply and having an opposing surface
opposing said one surface in parallel and having a diameter 1.2 to
1.5 times a diameter of said one surface.
4. The plasma process system (1) according to claim 3,
characterized by further comprising a shield ring (26) which has an
opening (26a) formed therein with a diameter approximately equal to
the diameter of said opposing surface and covers a peripheral
portion of said second electrode plate (20) in such a way that said
opposing surface is exposed to the inside said opening (26a).
5. The plasma process system (1) according to claim 4,
characterized in that said opposing surface is a major surface and
said second electrode plate (20) has a projection (20a) which fits
in said opening (26a)
6. A plasma process system (1) characterized by comprising: a
chamber (2); an electrode plate (20) connected to a high-frequency
power supply and provided with first gas holes (19) for supplying a
process gas into said chamber (2); and a shield ring (26) which is
provided with second gas holes (26b), has an opening (26a) and
covers a periphery of said electrode plate (20) in such a way that
said electrode plate (20) is exposed to the inside of said opening
(26a).
7. The plasma process system (1) according to claim 6,
characterized in that said second gas holes (26b) are laid out
annually around said opening (26a) and a maximum layout diameter of
said second gas holes (26b) is about 1.1 times a diameter of said
opening (26a).
8. The plasma process system (1) according to claim 6,
characterized in that said exposed surface is a major surface, said
electrode plate (20) has a projection (20a) which fits in said
opening (26a), and a major surface of said projection (20a) forms a
substantially flat surface together with said shield ring (26).
9. A plasma process system (1) characterized by comprising: a
chamber (2) in which a predetermined plasma process is performed on
a subject to be processed; a cleaning gas supply port (30) which
supplies a cleaning gas containing halogen into said chamber (2);
and an electrode plate (20) provided with gas holes (19) for
supplying a process gas into said chamber (2) and so constituted as
to contain a material resistive to a halogen radical.
10. The plasma process system (1) according to claim 9,
characterized in that said electrode plate (20) is so constituted
as to contain a material resistive to a halogen radical rather than
to silicon.
11. The plasma process system (1) according to claim 9,
characterized in that said cleaning gas is comprised of a material
containing fluorine and said halogen radical is comprised of a
fluorine radical.
12. The plasma process system (1) according to claim 9,
characterized in that said material resistive to said halogen
radical is selected from a group of silicon carbide, carbon,
aluminum, alumite, alumina and sprayed quartz alumina.
13. The plasma process system (1) according to claim 9,
characterized by further comprising: a mount table (10) which is
provided opposite to said electrode plate (20) and on which said
subject to be processed is placed; and a ring-like member (17)
formed of a material resistive to said halogen radical.
14. The plasma process system (1) according to claim 9,
characterized in that said cleaning gas is turned into a plasma in
said chamber (2) to generate said halogen radical.
15. The plasma process system (1) according to claim 9,
characterized by further comprising an activator (33) provided
outside said chamber (2) and connected to said cleaning gas supply
port, and in that said activator (33) generates said halogen
radical by activating said cleaning gas and supplies said generated
halogen radical into said chamber (2) 2.
16. The plasma process system (1) according to claim 9,
characterized in that said cleaning gas is so formed as to contain
an oxygen-containing material.
17. A plasma process method using a plasma process system having a
chamber (2) in which a predetermined plasma process is performed on
a subject to be processed by generation of a plasma inside, a first
electrode plate (10) on one surface of which a subject to be
processed is placed, and a second electrode plate (20) connected to
a high-frequency power supply and having an opposing surface
opposing said one surface in parallel characterized by including
the step of: setting a diameter of said opposing surface to 1.2 to
1.5 tines a diameter of said one surface and supplying
high-frequency power to said second electrode.
18. A plasma process method using a plasma process system having a
chamber (2) in which a predetermined plasma process is performed on
a subject to be processed by generation of a plasma inside, an
electrode plate (20) provided with first gas holes (19) for
supplying a process gas into said chamber (2) and connected to a
high-frequency power supply, and a shield ring (26) which is
provided with second gas holes (26b), has an opening (26a) and
covers a periphery of said electrode plate (20) in such a way that
said electrode plate (20) is exposed to the inside of said opening
(26a), characterized by including the step of spraying said gas
into said chamber (2) through said first gas holes (19) and said
second gas holes (26b).
Description
TECHNICAL FIELD
[0001] The present invention relates to a plasma process system and
a plasma process method which perform processes, such as film
deposition and etching, using a plasma.
BACKGROUND ART
[0002] A plasma process system which processes the surface of a
substrate, such as a semiconductor wafer, using a plasma is used in
a fabrication process for a liquid crystal display or the like. As
plasma process systems, there are, for example, a plasma etching
system which performs etching on a substrate and a plasma CVD
system which performs chemical vapor deposition (Chemical Vapor
Deposition: CVD). Of them, a parallel plate plasma process system
is widely used because it has an excellent process uniformity and
its system structure is relatively simple.
[0003] The structure of a parallel plate plasma process system is
shown in FIG. 17. As shown in FIG. 17, a plasma process system 101
comprises a chamber 102, a shower electrode 103 which feeds a
process gas into the chamber 102 and constitutes an upper
electrode, and a susceptor 104 on which a subject W to be
processed, such as a semiconductor wafer, is placed and which
constitutes a lower electrode.
[0004] The shower electrode 103 comprises an electrode plate 106
having multiple gas holes 105, and an electrode support 108 having
a hollow portion 107 which leads the process gas to the gas holes
105. The electrode plate 106 is supported on the electrode support
108 at its peripheral portion by screws or the like and the
supported portion is covered with a shield ring 109 made of an
insulator. The shield ring 109 has an opening having a smaller
diameter than the electrode plate 106 and is constructed in such a
way that the electrode plate 106 is exposed to the inside of the
opening. The shield ring 109 reduces the generation of abnormal
discharge at the supported portion.
[0005] The plasma process system 101 feeds a process gas (the
solid-line arrows in the diagram) to the to-be-processed subject W
through the gas holes 105 of the electrode plate 106 and supplies
RF power to the electrode plate 106 to form an RF electric field
(the broken-line arrows in the diagram) between the exposed surface
of the electrode plate 106 and the susceptor 104. This generates
the plasma of the process gas on the to-be-processed subject W and
performs a predetermined process on the surface of the
to-be-processed subject W.
[0006] The plasma process system 101 with the above-described
structure has the following problems (1) and (2).
[0007] (1) To secure insulation, the shield ring 109 which protects
the periphery of the electrode plate 106 is made of a plate-like
member having a thickness of, for example, about 10 mm. The
electrode plate 106 is placed over the shield ring 109 in such a
way as to be exposed to the inside of the opening of the shield
ring 109. At this time, a step A is formed between the peripheral
portion of the exposed surface (bottom surface) of the electrode
plate 106 and the surface which is near the opening of the shield
ring 109.
[0008] Such a step .DELTA. varies the process characteristic of the
whole surface of the to-be-processed subject W and reduces the
process uniformity. That is, the gas in the opening that is
supplied through the gas holes 105 stays at the step .DELTA.,
disturbing the flow of the gas. This makes the gas supply at the
center portion and end portion of the to-be-processed subject W
uneven, thus lowering the process uniformity.
[0009] The diameter of the exposed surface of the electrode plate
106 hereinafter referred to as "upper electrode diameter") that
contacts a plasma is so formed as to be nearly equal to the
diameter of the surface of the opposing to-be-processed subject W.
That is, the upper electrode diameter is not determined to optimize
a gas flow and an electric field, which are formed between the
electrode plate 106 and the to-be-processed subject W, and to carry
out a process with high uniformity. Therefore, a process with a
sufficiently high uniformity may not be executed.
[0010] Even in case where the gas blowoff diameter and the upper
electrode diameter are changed in order to optimize the gas flow
and electric field, the gas blowoff diameter and the upper
electrode diameter are substantially determined by the diameter of
the opening of the shield ring 109. It is therefore difficult to
optimize the gas blowoff diameter and the upper electrode diameter
by independently varying them to thereby improve the process
uniformity.
[0011] As apparent from the above, the conventional plasma process
system 101 did not have the gas blowoff diameter and the upper
electrode diameter optimized to ensure sufficiently high process
uniformity.
[0012] (2) Dry cleaning using a halogen-based gas, such as
fluorine-based gas, is performed in the plasma process system 101.
Specifically, a halogen-based gas is generated inside or outside
the chamber 102 and a film adhered or deposited to the inside of
the chamber 102 is removed by a halogen active seed (e.g., fluorine
radicals) in the gas plasma. Particularly, fluorine has a high
reactivity to silicon and is suitable to clean a process system
which processes silicon-based films.
[0013] Here, to avoid metal contamination, the electrode plate 106
is formed of silicon. Such a silicon-based electrode plate 106 is
likely to be etched by the cleaning. Particularly, in remote plasma
cleaning which generates the plasma of the cleaning gas outside the
chamber 102 and selectively supply a radical seed in the chamber
102, the radical seed is highly active so that the degradation
(etching) of the electrode plate 106 becomes noticeable.
[0014] The degradation of the electrode plate 106 means a change in
the shape of the electrode plate 106 and changes the RF electric
field. A change in electric field varies the process
characteristics at, for example, the center portion and end portion
of the to-be-processed subject W, thus lowering the process
uniformity.
[0015] In case where the electrode plate 106 formed of silicon is
used, as mentioned above, cleaning is likely to etch the electrode
plate 106 so that a process with sufficiently high uniformity may
not be carried out.
DISCLOSURE OF INVENTION
[0016] It is therefore an object of the invention to provide a
plasma process system and a plasma process method which can perform
a process with high uniformity on a subject to be processed.
[0017] To achieve the object, a plasma process system (1) according
to the first aspect of the invention comprises:
[0018] a chamber (2);
[0019] an electrode plate (20) provided with gas holes (19) for
supplying a process gas into the chamber (2) and having a
projection (20a); and
[0020] a shield ring (26) having an opening (26a) which is fitted
over the projection (20a) and is constituted by a ring-like plate
member which covers a peripheral portion of the electrode plate
(20) with the projection (20a) and the opening (26a) fitted
together.
[0021] In the system with the above-described structure, for
example, the projection (20a) of the electrode plate (20), in such
a state as to be fitted in the opening (26a), forms a substantially
flat surface together with a major surface of the shield ring
(26).
[0022] To achieve the object, a plasma process system (1) according
to the second aspect of the invention comprises:
[0023] a first electrode plate (10) on one surface of which a
subject to be processed is placed; and
[0024] a second electrode plate (20) connected to a high-frequency
power supply and having an opposing surface opposing the one
surface in parallel and having a diameter 1.2 to 1.5 times a
diameter of the one surface.
[0025] The system with the above-described structure may further
comprise a shield ring (26) which has an opening (26a) formed
therein with a diameter approximately equal to the diameter of the
opposing surface and covers a peripheral portion of the second
electrode plate (20) in such a way that the opposing surface is
exposed to the inside of the opening (26a).
[0026] In the system with the above-described structure, the
opposing surface may be a major surface and the second electrode
plate (20) may have a projection (20a) which fits in the opening
(26a)
[0027] To achieve the object, a plasma process system (1) according
to the third aspect of the invention comprises:
[0028] a chamber (2);
[0029] an electrode plate (20) connected to a high-frequency power
supply and provided with first gas holes (19) for supplying a
process gas into the chamber (2); and
[0030] a shield ring (26) which is provided with second gas holes
(26b), has an opening (26a) and covers a periphery of the electrode
plate (20) in such a way that the electrode plate (20) is exposed
to the inside of the opening (26a).
[0031] In the system with the above-described structure, the second
gas holes (26b) may be laid out annually around the opening (26a)
and a maximum layout diameter of the second gas holes (26b) may be
about 1.1 times a diameter of the opening (26a).
[0032] In the system with the above-described structure, the
exposed surface may be a major surface, the electrode plate (20)
may have a projection (20a) which fits in the opening (26a), and a
major surface of the projection (20a) may form a substantially flat
surface together with the shield ring (26).
[0033] To achieve the object, a plasma process system (1) according
to the fourth aspect of the invention comprises:
[0034] a chamber (2) in which a predetermined plasma process is
performed on a subject to be processed;
[0035] a cleaning gas supply port (30) which supplies a cleaning
gas containing halogen into the chamber (2); and
[0036] an electrode plate (20) provided with gas holes (19) for
supplying a process gas into the chamber (2) and so constituted as
to contain a material resistive to a halogen radical.
[0037] In the system with the above-described structure, the
electrode plate (20) is so constituted as to contain a material
resistive to a halogen radical rather than to silicon, for
example.
[0038] In the system with the above-described structure, the
cleaning gas is comprised of a material containing, for example,
fluorine and the halogen radical is comprised of, for example, a
fluorine radical.
[0039] In the system with the above-described structure, the
material resistive to the halogen radical may be selected from a
group of silicon carbide, carbon, aluminum, alumite, alumina and
sprayed quartz alumina.
[0040] The plasma process system (1) with the above-described
structure may further comprise:
[0041] a mount table (10) which is provided opposite to the
electrode plate (20) and on which the subject to be processed is
placed; and
[0042] a ring-like member (17) formed of a material resistive to
the halogen radical.
[0043] In the system with the above-described structure, for
example, the cleaning gas is turned into a plasma in the chamber
(2) to generate the halogen radical.
[0044] The plasma process system (1) with the above-described
structure may further comprise an activator (33) provided outside
the chamber (2) and connected to the cleaning gas supply port,
and
[0045] the activator (33) may generate the halogen radical by
activating the cleaning gas and supply the generated halogen
radical into the chamber (2) 2.
[0046] In the system with the above-described structure, for
example, the cleaning gas is so formed as to contain an
oxygen-containing material.
[0047] To achieve the object, a plasma process method according to
the fifth aspect of the invention uses a plasma process system
having a chamber (2) in which a predetermined plasma process is
performed on a subject to be processed by generation of a plasma
inside, a first electrode plate (10) on one surface of which a
subject to be processed is placed, and a second electrode plate
(20) connected to a high-frequency power supply and having an
opposing surface opposing the one surface in parallel and includes
the step of:
[0048] setting a diameter of the opposing surface to 1.2 to 1.5
times a diameter of the one surface and supplying high-frequency
power to the second electrode is included.
[0049] To achieve the objects, a plasma process method according to
the second aspect of the invention uses a plasma process system
having a chamber (2) in which a predetermined plasma process is
performed on a subject to be processed by generation of a plasma
inside, an electrode plate (20) provided with first gas holes (19)
for supplying a process gas into the chamber (2) and connected to a
high-frequency power supply, and a shield ring (26) which is
provided with second gas holes (26b), has an opening (26a) and
covers a periphery of the electrode plate (20) in such a way that
the electrode plate (20) is exposed to the inside of the opening
(26a), and includes the step of:
[0050] spraying the gas into the chamber (2) through the first gas
holes (19) and the second gas holes (26b).
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 illustrates the structure of a plasma process system
according to a first embodiment.
[0052] FIG. 2 shows the structure of an upper electrode shown in
FIG. 1.
[0053] FIG. 3A shows the results of checking the pressure above a
wafer when a projection type electrode plate is used, and
[0054] FIG. 3B shows the results of checking the pressure above a
wafer when a flat electrode plate is used.
[0055] FIG. 4 shows the relationship between a gap between
electrodes and pressure when projection type and flat electrode
plates are used.
[0056] FIG. 5 shows the relationship between a step between the
electrode plate and a shield ring and the uniformity of a
deposition speed.
[0057] FIG. 6 shows the relationship between a step between the
electrode plate and the shield ring and the aspect ratio of a
groove which can be buried.
[0058] FIG. 7 is an enlarged diagram of an upper electrode and a
susceptor according to a second embodiment.
[0059] FIG. 8 shows the relationship between a ratio of upper and
lower electrodes (D2/D1) and the uniformity of a deposition
speed.
[0060] FIG. 9 shows the film thickness distribution on a wafer
surface at A, B and C in FIG. 8.
[0061] FIG. 10 is an enlarged diagram of an upper electrode and a
susceptor according to a third embodiment.
[0062] FIG. 11 shows the relationship between a gas blowoff
diameter (D3) and the deposition speed.
[0063] FIG. 12 illustrates the structure of a plasma process system
according to a fourth embodiment.
[0064] FIG. 13 shows the results of checking the etching rates of
electrode plates made of various kinds of materials.
[0065] FIG. 14 shows the results of checking the deposition speeds
when continuous deposition was performed using electrode plates
made of various kinds of materials.
[0066] FIG. 15 shows the results of performing cleaning using an
oxygen-added cleaning gas.
[0067] FIG. 16 shows the results of performing cleaning using an
oxygen-added cleaning gas.
[0068] FIG. 17 illustrates the structure of a conventional plasma
process system.
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0069] A process system according to the first embodiment of the
invention will now be described below with reference to the
accompanying drawings. In the following embodiment to be
illustrated below, a parallel plate plasma process system which
forms a silicon fluoride oxide (SiOF) film on a semiconductor wafer
(hereinafter "wafer W") by CVD (Chemical Vapor Deposition) will be
described as an example.
[0070] FIG. 1 illustrates the structure of a plasma process system
1 according to the first embodiment.
[0071] The plasma process system 1 has a cylindrical chamber 2 made
of, for example, aluminum whose surface has been subjected to an
alumite process (anodic oxidation). The chamber 2 is grounded to a
common potential.
[0072] A gas supply tube 3 is provided in the upper portion of the
chamber 2. The gas supply tube 3 is connected to a which supplies a
process gas having a mixture of SiF.sub.4, SiH.sub.4, O.sub.2, Ar,
etc. The process gas is adjusted to a predetermined flow rate by a
mass flow controller (not shown) and is then supplied into the
chamber 2.
[0073] An exhaust port 5 is provided in one side of the bottom
portion of the chamber 2. An exhaust unit 6 which comprises a turbo
molecular pump or the like is connected to the exhaust port 5. The
exhaust unit 6 degases inside the chamber 2 to a predetermined
depressurized atmosphere, e.g., a predetermined pressure of 1 Pa or
lower.
[0074] A gate valve 7 is provided on a side wall of the chamber 2.
With the gate valve 7 open, transfer-in and transfer-out of a wafer
W is performed between the chamber 2 and an adjoining loadlock
chamber (not shown).
[0075] A susceptor support 8 with an approximately columnar shape
stands upright from the center of the bottom portion in the chamber
2. A susceptor 10 is provided on the susceptor support 8 via an
insulator 9 of ceramics or the like. The susceptor support 8 is
connected via a shaft 11 to an elevation mechanism (not shown)
provided under the chamber 2 and is elevatable up and down.
[0076] An unillustrated electrostatic chuck which has approximately
the same diameter as the wafer W is provided above the susceptor
10. The wafer W placed on the susceptor 10 is fixed by Coulomb's
force by the electrostatic chuck.
[0077] The susceptor 10 is made of a conductor, such as aluminum,
and constitutes the lower electrode of a parallel plate electrode.
A first RF source 12 is connected to the susceptor 10 via a first
matching device 13. The first RF source 12 has a frequency in a
range of 0.1 to 13 MHz. As the frequency in the range is applied to
the first RF source 12, an effect, such as imparting adequate ion
impact to a to-be-processed subject, is acquired.
[0078] A refrigerant chamber 14 is provided inside the susceptor
support 8. A refrigerant circulates in the refrigerant chamber 14.
The refrigerant supplied through a refrigerant supply tube 15
passes through the refrigerant chamber 14 and is discharged from a
refrigerant discharge tube 16. As the refrigerant circulates in the
refrigerant chamber 14, the susceptor 10 and the process surface of
the wafer W are kept at a desired temperature. A transfer lift pin
(not shown) for the wafer W is provided in an elevatable manner,
penetrating the susceptor 10 and the electrostatic chuck.
[0079] A focus ring 17 made of an insulator, such as ceramics, is
provided at the peripheral portion of the top surface of the
susceptor 10. The focus ring 17 has an opening in the center and
the diameter of the opening is made slightly larger than that of
the wafer W. The wafer W is mounted on the top surface of the
susceptor 10 which is exposed to the inside of the opening of the
focus ring 17. The focus ring 17 allows a plasma active seed to be
effectively incident to the wafer W.
[0080] An upper electrode 18 of the parallel plate electrode is
provided at the roof portion of the chamber 2. The upper electrode
18 has a so-called shower head structure and comprises an electrode
plate 20 having multiple gas holes 19 and an electrode support 22
which forms a hollow diffusion portion 21 between itself and the
electrode plate 20.
[0081] The electrode support 22 is connected to the gas supply tube
3. The gas supplied from the gas supply tube 3 is diffused at the
diffusion portion 21 and is sprayed through the multiple gas holes
19. The electrode plate 20 is provided in such a way as to face the
susceptor 10 and is so formed as to have a diameter slightly larger
than that of the wafer W. This causes the process gas to be
supplied to the entire top surface of the wafer W.
[0082] The electrode plate 20, made of a conductive material, such
as aluminum, is formed in a disk shape. The electrode plate 20 is
connected to a second RF source 24 via a second matching device 23.
Application of RF power to the electrode plate 20 generates the
plasma of the gas supplied through the gas holes 19.
[0083] FIG. 2 shows an enlarged diagram of near the electrode plate
20. As shown in FIG. 2, the peripheral portion of the electrode
plate 20 is formed thin so as to form a columnar projection 20a.
The electrode plate 20 has screw grooves or the like in the
peripheral portion and is fastened to the electrode support 22 at
the peripheral portion by screws 25.
[0084] The screwed portions of the peripheral portion of the
electrode plate 20 are covered with a shield ring 26 made of
ceramics or the like, such as aluminum nitride. The shield ring 26
has a major surface in which an opening 26a is formed, and is fixed
to the side portions or the like of the roof of the chamber 2 in
such a way that the major surface becomes approximately parallel to
the roof surface of the chamber 2. The opening 26a of the shield
ring 26 is formed to have a smaller diameter than the electrode
plate 20 and is provided so that the electrode plate 20 is exposed
to the inside of the opening 26a. At least the major surface
portion of the shield ring 26 is formed in a plate shape having a
thickness of about 10 mm. Covering the screwed portions with the
shield ring 26 prevents abnormal discharge or the like at the
screwed portions at the time of generating a plasma
[0085] The diameter of the opening 26a of the shield ring 26 is
formed to be approximately equal to the diameter of the projection
20a of the electrode plate 20 and the shield ring 26 is placed in
such a way that the projection 20a of the electrode plate 20 is
fitted, downward, into the opening 26a.
[0086] The diameter of the projection 20a of the electrode plate 20
is set nearly equal to the diameter of the opening of the shield
ring 26 and the projection 20a is constructed in such a way as to
be fitted in the opening 26a of the shield ring 26 nearly without a
gap. The gas holes 19 are formed so as to penetrate the projection
20a so that the spray of the process gas will not be inhibited by
the shield ring 26.
[0087] The projection 20a of the electrode plate 20 and the shield
ring 26, when fitted together, form substantially the same surface.
That is, the height of the projection 20a of the electrode plate 20
is set to a value (e.g., about 10 mm) approximately equal to the
thickness of the portion near the opening 26a of the shield ring
26.
[0088] In the above-described structure, the electrode plate 20 and
the shield ring 26 form a flat surface with respect to a plasma
generation area. In this case, a step is not formed between the
exposed surface of the electrode plate 20 and the major surface of
the shield ring 26. Accordingly, the flow of the process gas which
is sprayed though the gas holes 19 is not disturbed at such a step
portion and the flow of the process gas which is sprayed through
the entire gas holes 19 becomes nearly uniform. This allows the
process gas to be supplied to the surface of the wafer W with high
uniformity so that a process with high uniformity is performed on
the wafer W.
EXAMPLE 1
[0089] FIG. 3A shows the results of checking the pressure at
individual points above the wafer W when an Ar gas is supplied into
the chamber 2 via the projection type electrode plate 20. FIG. 3B
shows the results when the flat electrode plate 20 which does not
have the projection 20a is used. The distance between the electrode
plate 20 and the susceptor 10 (gap between electrodes) was 30 mm
and the Ar gas was let to flow to the surface of the wafer W of 200
mm at 300 sccm.
[0090] As shown in FIG. 3A, in the case of using the projection
type electrode plate 20, the pressure above the wafer W does not
change at the center portion and end portion and is nearly constant
at about 1 Pa. In the case of using the flat type electrode plate
20, as shown in FIG. 2B, the pressure at the end portion above the
wafer W is about 1 Pa whereas the pressure at the center portion
becomes about 1.5 Pa nearly 50% higher. The pressure difference
occurs near the step portion between the electrode plate 20 and the
shield ring 26. It is understood from this the use of the
projection type electrode plate 20 which does not produce a step
can make the pressure above the wafer W nearly constant.
[0091] FIG. 4 shows the results of checking a change in pressure
above the center of the wafer W when the gap between electrodes is
changed in the experiments illustrated in FIGS. 3A and 3B. When the
flat electrode plate 20 is used, as shown in FIG. 4, the pressure
greatly rises with a decrease in the gap between electrodes and
reaches about 4 Pa at the electrode gap of 10 mm.
[0092] When the projection type electrode plate 20 is used, a
significant rise in pressure is not seen even when the gap between
electrodes is varied and the pressure is about 2 Pa, nearly half
the pressure of the flat type, even at the electrode gap of 10
mm.
[0093] It is understood from the results shown in FIG. 4 that when
the projection type electrode plate 20 is used, the pressure above
the wafer W (i.e., the substantial process pressure) becomes
relatively low. In general, a high process pressure gives an
undesirable influence to the plasma process. In a burying process
by CVD, particularly, a high pressure is likely to produce voids.
It is understood from this that the use of the projection type
electrode plate 20 can ensure a highly reliable process,
particularly, a burying process.
[0094] FIG. 5 shows the results of checking the uniformity of the
deposition speed on the top surface of the wafer W when the step
(the height of the projection 20a) between the exposed surface of
the electrode plate 20 and the exposed surface of the shield ring
26 is changed. The deposition conditions here are
SiH.sub.4/SiF.sub.4/O.sub.2/A- r=22/28/250/50 (sccm), pressure
(discharge pressure) of 1.3 Pa, and the electrode gap of 20 mm. The
deposition speed uniformity was calculated from (deposition speed
uniformity (%))=((maximum deposition speed)+(minimum deposition
speed))/(average deposition speed).times.2).times.100. A lower
value of the deposition speed uniformity indicates a less variation
in deposition speed and high process uniformity. The thickness of
the shield ring 26 is 10 mm and when the step height is 0 mm, the
electrode plate 20 and the shield ring 26 form a flat surface.
[0095] As shown in FIG. 5, the smaller the step between the
electrode plate 20 and the shield ring 26 is, the smaller the value
of the uniformity of the deposition speed becomes, making it
apparent that a film deposition process with high uniformity is
performed on the entire top surface of the wafer W.
[0096] FIG. 6 shows the results of performing a process of burying
a groove having a predetermined aspect ratio while changing the
step and checking the maximum aspect ratio at which a good burying
process is possible without producing voids. In FIG. 6, the aspect
ratio is expressed as a ratio with 1 being the result when the flat
electrode plate 20 (a step of -10 mm) is used.
[0097] As shown in FIG. 6, the smaller the step is or without the
step, the higher the maximum aspect ratio which ensure good burying
becomes. In case where the electrode plate 20 and the shield ring
26 form a flat surface (a step of 0 mm), for example, a good
burying process can be performed on a groove whose aspect ratio is
1.5 times that of the case where the flat electrode plate 20 is
used (a step of -10 mm). Here, the higher the aspect ratio of the
groove is, the easier it is to cause voids at the time of the
burying process.
[0098] Together with the results shown in FIG. 4, it is understood
that as the step is made smaller or eliminated by the use of the
projection type electrode plate 20, process pressure above the
wafer W is suppressed low and a highly reliable burying process
with generation of fewer voids is carried out.
[0099] As described above, the first embodiment takes such a
structure that the electrode plate 20 is formed into a projection
type and the exposed surface of the electrode plate 20 and the
major surface of the shield ring 26 form a flat surface. This
structure eliminates the step between the electrode plate 20 and
the shield ring 26, and can reduce or eliminate the disturbance of
the process gas above the wafer W. Accordingly, the pressure above
the wafer W becomes nearly uniform on the entire top surface so
that a process with high uniformity can be performed on the entire
top surface. Further, the pressure above the wafer W can be kept at
a relatively low pressure so that a highly reliable process with
suppressed generation of voids can be executed.
[0100] In the first embodiment, the height of the projection 20a of
the electrode plate 20 is approximately equal to the thickness of
the shield ring 26 and the electrode plate 20 and the shield ring
26 form substantially the same surface. However, the height of the
projection 20a is not limited to that and may be greater than the
thickness of the shield ring 26 so that the projection 20a
protrudes from the opening of the shield ring 26.
Second Embodiment
[0101] The second embodiment of the invention will be discussed
below. A plasma process system 1 according to the second embodiment
has nearly the same structure as the plasma process system 1 of the
first embodiment illustrated in FIG. 1. FIG. 6 shows an enlarged
diagram of near the upper and lower electrodes of the second
embodiment. In the diagram, same reference symbols are given to
those portions which are the same as those in FIGS. 1 and 2 and the
description will be omitted for easier understanding.
[0102] In the second embodiment, the electrode plate 20 has a
structure similar to that of the first embodiment. That is, the
electrode plate 20 is formed into a projection type and the exposed
surface (bottom surface) of the projection 20a and the exposed
surface (bottom surface) of the shield ring 26 form approximately
the same plane surface. The diameter of the opening of the focus
ring 17 is set approximately equal to the diameter of the wafer
W.
[0103] The ratio of the diameter of the exposed surface of the
susceptor 10 (lower electrode diameter D1) and the diameter of the
exposed surface of the electrode plate 20 (upper electrode diameter
D2) is designed to be a predetermined value. Here, the exposed
surface of the susceptor 10 indicates the surface that
substantially functions as the lower electrode, and the lower
electrode diameter D1 is almost equal to the diameter of the
opening of the focus ring 17 or the diameter of the wafer W. The
exposed surface of the electrode plate 20 indicates the surface
that substantially functions as the upper electrode, and the upper
electrode diameter D2 is almost equal to the diameter of the major
surface of the projection 20a or the diameter of the opening 26a of
the shield ring 26. In is assumed below that the lower electrode
diameter D1 indicates the diameter of the wafer W and the upper
electrode diameter D2 indicates the diameter of the major surface
of the projection 20a.
[0104] For example, the lower electrode diameter D1 and the upper
electrode diameter D2 are designed in such a way that their ratio
(D2/D1) is 1.2 to 1.5, particularly, 1.25 to 1.45. In case where
the lower electrode diameter D1 is 200 mm, for example, the upper
electrode diameter D2 is set to 260 mm.
[0105] Here, the gas holes 19 are provided so as to penetrate the
projection 20a of the electrode plate 20, e.g., concentrically. The
electrode diameter ratio (D2/D1) is varied in such a way as not to
change the layout of the gas holes 19. As the electrode diameter
ratio (D2/D1) is changed, therefore, an RF electric field which is
formed between the upper and lower electrodes can be changed with
the supply of the process gas set constant
EXAMPLE 2
[0106] FIG. 8 shows the results of performing a film deposition
process while changing the electrode diameter ratio (D2/D1) and
checking the uniformity of the deposition speed on the top surface
of the wafer W. The deposition conditions here were
SiH.sub.4/SiF.sub.4/O.sub.2/Ar=22/28/250/- 50 (sccm), pressure of
1.3 Pa, and the electrode gap of 20 mm. The deposition speed
uniformity was calculated from (deposition speed uniformity:
%)=((maximum deposition speed)+(minimum deposition speed))/(average
deposition speed).times.2).times.100.
[0107] It is understood from the results shown in FIG. 8 that when
the electrode diameter ratio (D2/D1) lies in the range of 1.2 to
1.5, the deposition speed uniformity is equal to or less than 5%
and a film is formed with high uniformity on the entire top surface
of the wafer W. It is also apparent that higher uniformity is shown
particularly when the electrode diameter ratio is in the range of
1.25 to 1.45.
[0108] When the diameters of the upper and lower electrodes are
equal (D2/D1=1) and when the diameter of the upper electrode D2 is
too large (D2/D1>1.5), it is apparent that film deposition with
high uniformity is not made on the entire top surface of the wafer
W and the value of the deposition speed uniformity is high so that
an RF electric field suitable for the process is not formed.
[0109] FIG. 9 shows the results of checking the film thickness at
individual points of the top surface of the wafer W after film
deposition in cases where the electrode diameter ratio is 1.1 (A in
FIG. 8), 1.4 (B) and 1.6 (C).
[0110] It is understood from FIG. 9 that when the electrode
diameter ratio is 1.4 (B), deposition with high uniformity is
carried out When the ratio is 1.1 (A), on the other hand, the
deposition speed is high at the center portion of the wafer W and
is low at the end portion. When the ratio is 1.6 (C), contrary to
the above, the deposition speed is high at the end portion and is
low at the center portion. It is apparent from those like the
results shown in FIG. 8 that when the electrode diameter ratio lies
within the range of 1.2 to 1.5, the optimal RF electric field is
formed and film deposition with high uniformity can be performed on
the entire top surface of the wafer W.
[0111] In the second embodiment the projection type electrode plate
20 is used. However, the invention is not limited to the projection
type electrode plate 20 but can be adapted to the flat electrode
plate 20. For instance, the ratio of the upper and lower electrode
diameters may likewise be defined with the upper electrode diameter
D2 set to the diameter of the exposed surface of the electrode
plate 20, i.e., the diameter of the opening of the shield ring
26.
Third Embodiment
[0112] The third embodiment of the invention will be discussed
below. A plasma process system 1 according to the third embodiment
has approximately the same structure as the plasma process system 1
of the first embodiment illustrated in FIG. 1. FIG. 10 shows an
enlarged diagram of near the upper and lower electrodes of the
third embodiment. In the diagram, same reference symbols are given
to those portions which are the same as those in FIGS. 1 and 2 and
the description will be omitted for easier understanding.
[0113] The electrode plate 20 is formed into a projection type and,
as shown in FIG. 10, the exposed surface (bottom surface) of the
projection 20a and the exposed surface (bottom surface) of the
shield ring 26 form approximately the same plane surface. The
exposed surface of the projection 20a substantially forms an RF
electric field.
[0114] The third embodiment has such a structure that while the
area of the exposed surface of the electrode plate 20 is kept
constant, the supply area of the process gas (the blowoff diameter
of the process gas) can be enlarged as desired. That is, it has a
structure such that the gas holes 19 are provided not only in the
electrode plate 20 but also in the shield ring 26 that surrounds
it.
[0115] As shown in FIG. 10, the shield ring 26 has gas holes 26b
formed around the electrode plate 20. The electrode support 22 is
provided in such a way that the diffusion portion 21 formed inside
communicate with the gas holes 26b. Accordingly, the process gas is
ejected from the gas holes 19 provided in the electrode plate 20
and the gas holes 26b in the shield ring 26.
[0116] The gas holes 26b are arranged in the same way as the gas
holes 19 of the electrode plate 20. The gas holes 19 of the
electrode plate 20 are provided, for example, concentrically, and
the gas holes 26b of the shield ring 26 are provided around the gas
holes 19 of the electrode plate 20.
[0117] Here, the blowoff diameter (D3) for the process gas which is
comprised of the gas holes 19 and the gas holes 26b is designed to
be larger than the diameter of the exposed surface of the electrode
plate 20 (upper electrode diameter D2) and, particularly, about 1.1
times greater (D3/D1>1.1). The blowoff diameter D3 is the
diameter of, for example, the outermost gas hole 26b. When the
upper electrode diameter D2 is set to 260 mm, for example, the
blowoff diameter D3 is set to about 280 mm about 1.1 times D2.
[0118] As discussed above, the provision of the gas holes 26b in
the shield ring 26 can enlarge the gas supply area without changing
the RF electric field without changing the area of the exposed
surface of the electrode plate 20. As the gas supply area is
enlarged, the gas can be supplied to the entire top surface of the
wafer W more uniformly. Therefore, a process with high uniformity
can be performed on the top surface of the wafer W.
EXAMPLE 3
[0119] FIG. 11 shows the results of checking the deposition speed
and the uniformity of the deposition speed on the top surface of
the wafer W while changing the blowoff diameter D3 for the process
gas. Here, the upper electrode diameter D2 was set to 260 mm. The
deposition conditions were
SiH.sub.4/SiF.sub.4/O.sub.2/Ar=22/28/250/50 (sccm), pressure of 1.3
Pa, and the electrode gap of 20 mm. The deposition speed uniformity
was calculated from (deposition speed uniformity: %)=((maximum
deposition speed)+(minimum deposition speed))/(average deposition
speed).times.2).times.100.
[0120] It is apparent from FIG. 11 that the greater the blowoff
diameter D3 is, the higher the deposition speed is. It is also
apparent that when the blowoff diameter D3 is equal to or greater
than about 240 mm (equal to or greater than about 0.85 times the
upper electrode diameter D2 and equal to or greater than about 1.2
times the wafer diameter), a sufficient high deposition speed is
obtained.
[0121] Further, it is apparent from that the greater the blowoff
diameter D3 is, the higher the uniformity of the deposition speed
is. It is also apparent that when the blowoff diameter D3 is
greater than the upper electrode diameter D2, particularly, equal
to or greater than 280 mm (equal to or greater than about 1.1 times
the upper electrode diameter D2 and equal to or greater than about
1.4 times the wafer diameter), the uniformity of the deposition
speed shows a stable high value.
[0122] From those, if the blowoff diameter D3 is larger than the
upper electrode diameter D2, particularly, equal to or greater than
about 1.1 times, a process with high uniformity can be performed on
the entire top surface of the wafer W at a high deposition
speed.
[0123] According to the third embodiment, as described above, the
gas holes 26b are provided in the shield ring 26. Accordingly, the
blowoff diameter D3 for the process gas can be enlarged without
changing the RF electric field by changing the area of the exposed
surface of the electrode plate 20 that functions as the upper
electrode. This can lead to an improvement on the deposition speed
and an improvement on the in-plane process uniformity.
[0124] In the third embodiment, the gas holes 26b provided in the
shield ring 26 communicate with the hollow portion in the electrode
support 22 and receive the same supply of the process gas as the
gas holes 19 of the electrode plate 20 do. But, an independent gas
flow passage connected to the gas holes 26b of the shield ring 26
may be provided. At this time, a flow rate control device or the
like may be provided in the gas flow passage for the shield ring 26
to provide the structure that adjusts the amounts of the gas supply
at the electrode plate 20 and the shield ring 26 respectively.
[0125] In the third embodiment, the projection type electrode plate
20 is used. However, the projection type electrode plate 20 is not
restrictive but a similar structure may be taken for the flat
electrode plate 20. In this case, the diameter of the exposed
surface of the electrode plate 20 or the inside diameter of the
opening of the shield ring 26 should be set to the upper electrode
diameter (D2) and the blowoff diameter (D3) should be determined
based on it.
Fourth Embodiment
[0126] A plasma process system 1 according to the fourth embodiment
of the invention will be discussed below referring to the
accompanying drawings. The plasma process system 1 according to the
fourth embodiment has a structure such that a fluorine-based
cleaning gas is used to dry-clean the interior.
[0127] The structure of the plasma process system 1 according to
the fourth embodiment is illustrated in FIG. 12. In FIG. 12, same
reference symbols are given to the same structure to omit the
description.
[0128] As shown in FIG. 12, a cleaning gas supply port 30 is formed
in one side wall of the chamber 2. The cleaning gas supply port 30
is connected to a cleaning gas supply source 31 and a carrier gas
source 32. A fluorine-based cleaning gas, e.g., nitrogen
trifluoride (NF.sub.3), is supplied from the cleaning gas supply
source 31. An inactive gas, such as argon (Ar) or nitrogen, is
supplied from the carrier gas source 32.
[0129] An activator 33 is provided between the cleaning gas supply
port 30 and the cleaning gas supply source 31 and carrier gas
source 32. The activator 33 has an unillustrated plasma generation
mechanism and generates a high-density plasma of the gas that
passes inside, such as an ECR (Electron Cyclotron Resonance) plasma
or inductive coupled plasma (Inductive Coupled Plasma: ICP). The
activator 33 selectively discharges fluorine radicals in the
plasma.
[0130] As the cleaning gas is supplied into chamber 2, a
contaminated material such as silicon-based material, adhered or
deposited the interior of the chamber 2 is decomposed by the
fluorine radicals and discharged and eliminated. In this manner,
the cleaning gas is turned into a plasma outside the chamber 2 and
so-called remote plasma cleaning is carried out.
[0131] In the fourth embodiment, the electrode plate 20 is made of
a material having a resistance to fluorine radicals rather than
silicon. That is, the electrode plate 20 is made of anodized
aluminum, silicon carbide, carbon, aluminum, alumina, sprayed
quartz alumina or the like. As the electrode plate 20 is made of
the material, it is possible to suppress the degrading of the
electrode plate 20 originated from cleaning using a fluorine gas.
This suppresses a reduction in the deposition uniformity which is
caused by the degrading of the electrode plate 20 and a reduction
in productivity which is caused by an increase in the frequency of
replacement of the electrode plate 20.
[0132] A description will now be given of the deposition process of
the plasma process system 1 and the operation at the time of
cleaning with reference to FIG. 12.
[0133] First, the wafer W is loaded into the chamber 2 and mounted
on the susceptor 10. Next, the process gas consisting of SiF.sub.4,
SiH.sub.4, O.sub.2 and Ar is supplied into the chamber 2 and RF
power is applied to generate the plasma of the process gas. An SiOF
film is deposited on the wafer W by the generated plasma. As a film
with a predetermined thickness is deposited on the wafer W, the
wafer W is removed from the chamber 2. The above-described
operation is repeated to continuously process wafers W. At this
time, every time a predetermined number of wafers W are processed,
the chamber 2 is cleaned.
[0134] At the time of cleaning, first, a dummy wafer is loaded into
the chamber 2 and mounted on the susceptor 10. Then, the supply of
NF.sub.3 and Ar is started and the activator 33 is activated. The
activator 33 generates the plasma of the process gas and supplies a
gas containing fluorine radicals as an essential component into the
chamber 2. For example, SiOF adhered to the interior of the chamber
2 is caused by the cleaning gas to react with the fluorine radicals
to be decomposed into silane tetrafluoride and is removed. Cleaning
proceeds as deposition or the like inside the chamber 2 is removed
this way.
[0135] When predetermined end conditions, such as time and degree
of cleaning, are reached thereafter, the activator 33 is set off to
stop the supply of the gas. This ends cleaning and film deposition
is started again.
EXAMPLE 4
[0136] The etching rates of the electrode plates 20 when the
above-described cleaning was carried out using the electrode plates
20 made of various kinds of materials. The materials used were
silicon, silicon oxide, silicon nitride, anodized aluminum, silicon
carbide, carbon, aluminum, alumina, sprayed quartz alumina The
results are shown in FIG. 13. The results were shown as a ratio
with the etching rate of silicon taken as 100. The cleaning
conditions are NF.sub.3/Ar=1500 sccm/1500 sccm, pressure of 300 Pa,
an electrode gap of 48 mm and plasma supply power of about 2
kW.
[0137] It is apparent from FIG. 13 that the etching rates of
anodized aluminum, silicon carbide, carbon, aluminum, alumina and
sprayed quartz alumina are lower than the etching rates of silicon,
silicon oxide and silicon nitride. Particularly, they are half the
etching rate of silicon or lower (50% or lower). This indicates
that the electrode plates 20 made of anodized aluminum, silicon
carbide, carbon, aluminum, alumina and sprayed quartz alumina are
not easily etched by a fluorine-based gas are not easily
corroded.
[0138] FIG. 13 shows the results of not a case of remote plasma
cleaning but also a case where in-situ (in situ) plasma cleaning
was carried out. In the in situ plasma cleaning, NF.sub.3 and Ar
are introduced into the chamber 2 and the plasma of the cleaning
gas is generated inside the chamber 2. The cleaning conditions are
NF.sub.3/Ar=100 sccm/0 sccm, pressure of 65 Pa, an electrode gap of
48 mm and plasma supply power of about 500 W.
[0139] As shown in FIG. 13, a tendency similar to that in the
remote plasma cleaning is seen in the in-situ plasma cleaning too.
That is, the etching rate ratios in the case of using the electrode
plates 20 made of silicon, silicon oxide and silicon nitride are
close to 20%, whereas the etching rate ratios in the case of using
the electrode plates 20 made of anodized aluminum, silicon carbide,
carbon, aluiminum, alumina and sprayed quartz alumina are about 10%
or less. Apparently, the electrode plate 20 made of a
plasma-resistive material, such as silicon carbide is less likely
to be degraded by the remote plasma cleaning and in-situ plasma
cleaning than the electrode plate 20 made of silicon or the
like.
[0140] FIG. 14 shows the results of continuously performing film
deposition with cleaning in between using the electrode plates 20
made of various kinds of materials and checking the deposition
speeds in the individual film deposition processes. The electrode
plate 20 was made of one of alumite, silicon carbide, carbon,
aluminum, alumina, sprayed quartz alumina and silicon. Film
deposition was performed in such a way that a film with a
predetermined thickness was formed on the wafer W and the
deposition speed was calculated from the time needed to process 100
wafers W. Cleaning was performed every time 25 wafers W were
processed.
[0141] As apparent from FIG. 14, in case of using the electrode
plate 20 of silicon, the deposition speed is very high at the
beginning of the process as compared with the other materials. But,
the deposition speed drops significantly later and becomes lower
than that for the other materials.
[0142] In case of using a material other than silicon, on the other
hand, the deposition speed does not drop significantly and is
relatively constant even after 1000 wafers W are processed. In case
of using the electrode plate 20 of silicon carbide, particularly,
the highest deposition speed is maintained. It is understood from
this that the electrode plates 20 made of alumite, silicon carbide,
carbon, aluminum, alumina and sprayed quartz alumina, the electrode
plate 20 of silicon carbide in particular, are not easily degraded
by dry cleaning. Apparently, the electrode plate 20 made of a
material having a resistance to a plasma, such as silicon carbide,
is not easily etched by the fluorine-contained cleaning gas and
realizes a high productivity, such as a lower frequency of
replacement of the electrode plate 20. As it is not easily etched
at this time, the shape of the electrode plate 20 is maintained at
the initial shape over a long period of time and a process with
high uniformity is carried out over a long period of time.
[0143] In the fourth embodiment, the electrode plate 20 was made of
a material having a resistance to fluorine radicals. However, it is
not limited to the electrode plate 20 but a member around the
electrode which is exposed to fluorine radicals at the time of
cleaning may be made of the aforementioned material. For example,
the focus ring 17 may be made of the aforementioned material. As
the member around the electrode is made of a plasma-resistive
material, a high productivity can be achieved while suppressing the
degrading of the member.
[0144] In the fourth embodiment, a fluorine-based gas,
particularly, NF.sub.3, is used as a cleaning seed. However, other
halogen gases, such as chloride-based gas, may be used. Further,
besides NF.sub.3, fluorine-based gas, such as F.sub.2, CF.sub.4,
C.sub.2F.sub.6 and SF.sub.6 can be used as the cleaning gas to be
used for an Si-based film seed.
[0145] A cleaning gas which has an oxygen-contained material, such
as O.sub.2, O.sub.3, CO, CO.sub.2 or N.sub.2O, is added to the
aforementioned gas. This is particularly is effective when silicon
carbide (SiC) is used as the material for the electrode plate 20.
That is, a material containing carbon (C) is adhered to the inside
of the chamber 2 by etching of the electrode plate 20. In general,
a carbon-contained material is not easily etched by a halogen-based
gas and is easily decomposed into CO.sub.2 or the like by the gas
of an oxygen-contained material.
[0146] The results of checking the cleaning speed when cleaning was
carried out with an oxygen-contained material added to a cleaning
gas containing NF.sub.3 and Ar are shown in FIG. 15. FIG. 15 shows
the results in a case where the interior of the process system
which would deposit an SiC film was cleaned with cleaning gases
added with O.sub.2, CO, CO.sub.2 and N.sub.2O. Cleaning was
conducted by an in-situ plasma and a combination of the remote
plasma and in-situ plasma in addition to a remote plasma. The
combination of the remote plasma and in-situ plasma is to turn the
cleaning gas into a plasma outside the chamber 2 and then turn it
again into a plasma in the chamber 2 to do cleaning.
[0147] The results in a case where an oxygen-contained material was
added to the cleaning gas containing F.sub.2 and Ar are likewise
shown in FIG. 16.
[0148] The cleaning conditions for a remote plasma are
NF.sub.3/O.sub.2/Ar=1500 sccm/500 sccm/1500 sccm, pressure of 300
Pa, an electrode gap of 48 mm and plasma supply power of about 2
kW. The cleaning conditions for a in-situ plasma are
NF.sub.3/O.sub.2/Ar=100 sccm/50 sccm/0 sccm, pressure of 65 Pa, an
electrode gap of 48 mm and upper electrode supply power of 500 W.
Further, the cleaning conditions for a remote plasma+in-situ plasma
are NF.sub.3/O.sub.2/Ar=1000 sccm/500 sccm/1500 sccm, pressure of
300 Pa, an electrode gap of 48 mm, plasma supply power of about 2
kW and upper electrode supply power of 500 W.
[0149] It is apparent from FIGS. 15 and 16 that a higher cleaning
speed can be acquired in the case of using a cleaning gas added
with an oxygen-contained material than the case of making no
addition. This is because a deposition containing carbon (C) which
is not easily removed by fluorine radicals is easily removed as CO
or the like by oxygen radicals which are generated from an
oxygen-contained material. As adding an oxygen-contained material
to the cleaning gas can enhance the cleaning speed.
[0150] In the first to fourth embodiments, a case where the
parallel plate plasma process system 1 deposits an SiOF film on a
wafer has been discussed as one example. The film seed is not
limited to those in the above-described example but may be another
silicon-based film, such as, SiO.sub.2, SiN, SiCN, SiCH or SiOCH.
Various kinds of gas seeds can be used by combining the film
seeds.
[0151] Further, the invention is not limited to a deposition system
but can be adapted to any plasma process system which performs dry
cleaning, such as an etching system or thermal process system. For
example, it can be used not only in a CVD process but also various
plasma processes, such as an etching process. Further, a plasma
generating method is not only a parallel plate type but also may be
any type, such as a magnetron type, inductive coupled plasma or ECR
(Electron Cyclotron Resonance) type. Furthermore, a to-be-processed
subject is not limited to a semiconductor wafer but may be a glass
substrate or the like for a liquid crystal display device.
INDUSTRIAL APPLICABILITY
[0152] The invention can be suitably used for fabrication of
electronic devices, such as a liquid crystal display device.
[0153] The invention is based on Japanese Patent Application No.
2001-13572 filed on Jan. 22, 2001, Japanese Patent Application No.
2001-13574 filed on Jan. 22, 2001 and Japanese Patent Application
No. 2001-239720 filed on Aug. 7, 2001, and includes the
specifications, claims, drawings and abstracts thereof. The present
specification incorporates what is disclosed in the applications
entirely by reference.
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