U.S. patent application number 10/357456 was filed with the patent office on 2004-03-11 for plasma processing method and apparatus.
Invention is credited to Maegawa, Yukihiro, Nakayama, Ichiro, Okumura, Tomohiro, Suzuki, Hiroyuki.
Application Number | 20040045669 10/357456 |
Document ID | / |
Family ID | 27667500 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040045669 |
Kind Code |
A1 |
Okumura, Tomohiro ; et
al. |
March 11, 2004 |
Plasma processing method and apparatus
Abstract
Plasma is generated in the interior of a vacuum chamber to
process a high melting metal film formed on a substrate, while
supplying gas into the vacuum chamber and simultaneously exhausting
the interior of the vacuum chamber to control to a specified
pressure, by supplying a high-frequency power of a 30 MHz to 3 GHz
frequency to an antenna provided within the vacuum chamber in
opposition to the substrate placed on a substrate electrode within
the vacuum chamber, by supplying a high-frequency power of a 100
kHz to 20 MHz frequency different from the above frequency to the
antenna.
Inventors: |
Okumura, Tomohiro;
(Kadoma-shi, JP) ; Maegawa, Yukihiro;
(Ibaraki-shi, JP) ; Suzuki, Hiroyuki; (Yawata-shi,
JP) ; Nakayama, Ichiro; (Kadoma-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
27667500 |
Appl. No.: |
10/357456 |
Filed: |
February 4, 2003 |
Current U.S.
Class: |
156/345.35 ;
216/58; 216/68 |
Current CPC
Class: |
H01J 37/32082 20130101;
Y02E 50/30 20130101; C23F 4/00 20130101 |
Class at
Publication: |
156/345.35 ;
216/058; 216/068 |
International
Class: |
C23F 001/00; B44C
001/22; C03C 015/00; H01L 021/306 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2002 |
JP |
2002-29232 |
Feb 15, 2002 |
JP |
2002-38102 |
Claims
What is claimed is:
1. A plasma processing method for generating plasma in a vacuum
vessel, by supplying a high-frequency power of a 30 MHz to 3 GHz
frequency to an antenna provided within the vacuum vessel in
opposition to a substrate placed on a substrate electrode within
the vacuum vessel while interior of the vacuum vessel is controlled
to a specified pressure by supplying gas into the vacuum vessel and
simultaneously exhausting the interior of the vacuum vessel, and
thus processing a high melting metal film formed on the substrate,
the method comprising: additionally supplying a high-frequency
power of a 100 kHz to 20 MHz frequency different from the above
frequency to the antenna to process the substrate.
2. The plasma processing method according to claim 1, wherein the
high melting metal film is a film containing at least one element
selected from among iridium, rhodium, ruthenium, platinum, gold,
copper, rhenium, bismuth, strontium, barium, zirconium, lead, and
niobium.
3. The plasma processing method according to claim 1, wherein the
substrate is processed with temperature of the antenna controlled
by giving a flow of a refrigerant to the antenna while heat
conduction between the antenna and an antenna cover is ensured by
an electrically conductive sheet which is disposed between the
antenna and the antenna cover and whose surface parallel to the
substrate is larger in surface area than that of the antenna, and
further the substrate is processed while a self-bias voltage is
generated up to an end portion of the cover by additionally
supplying the high-frequency power of the 100 kHz to 20 MHz
frequency different from the above frequency to the antenna.
4. The plasma processing method according to claim 3, wherein the
plasma processing is an etching process of the high melting metal
film formed on the substrate.
5. The plasma processing method according to claim 4, wherein the
high melting metal film is a film containing at least one element
selected from among iridium, rhodium, ruthenium, platinum, gold,
copper, rhenium, bismuth, strontium, barium, zirconium, lead, and
niobium.
6. A plasma processing apparatus comprising: a vacuum vessel; a gas
supply unit for supplying gas into the vacuum vessel; an exhausting
unit for exhausting interior of the vacuum vessel; a
pressure-regulating valve for controlling the interior of the
vacuum vessel to a specified pressure; a substrate electrode for
placing thereon a substrate within the vacuum vessel; an antenna
provided in opposition to the substrate electrode and covered with
an insulating antenna cover; a first high-frequency power supply
capable of supplying a high-frequency power of a 30 MHz to 3 GHz
frequency to the antenna; a second high-frequency power supply
capable of additionally supplying a high-frequency power of a 100
kHz to 20 MHz frequency different from the above frequency to the
antenna; a refrigerant supply unit for making a refrigerant flow to
the antenna; and an electrically conductive sheet whose surface
parallel to the substrate is larger than that of the antenna and
which is provided between the antenna and the antenna cover.
7. The plasma processing apparatus according to claim 6, wherein
the antenna cover is made of quartz glass.
8. The plasma processing apparatus according to claim 6, wherein
the antenna cover is made of insulative silicon.
9. The plasma processing apparatus according to claim 6, wherein
the antenna cover is 1 mm to 10 mm thick.
10. The plasma processing apparatus according to claim 6, wherein
the electrically conductive sheet is made of a material having a
resistivity of not more than 10 .OMEGA..multidot.m.
11. The plasma processing apparatus according to claim 6, wherein
the electrically conductive sheet is 0.03 mm to 3 mm thick.
12. A plasma processing method for generating inductive-coupling
type plasma in a vacuum vessel by placing a substrate on a
substrate electrode within the vacuum vessel, supplying a first
high-frequency power of a 1 MHz to 60 MHz frequency to a feeding
point which is one end of a coil provided in opposition to the
substrate electrode while interior of the vacuum vessel is
controlled to a specified pressure by supplying gas into the vacuum
vessel and simultaneously exhausting the interior of the vacuum
vessel, and thus processing the substrate or a film formed on the
substrate, the method comprising: while supplying a second
high-frequency power of a frequency lower than that of the first
high-frequency power to the coil with the other end of the coil
grounded via a capacitor, processing the substrate.
13. A plasma processing method for generating inductive-coupling
type plasma in a vacuum vessel by placing a substrate on a
substrate electrode within the vacuum vessel, supplying a first
high-frequency power of a 1 MHz to 60 MHz frequency to a feeding
point which is one end of a coil provided in opposition to the
substrate electrode while interior of the vacuum vessel is
controlled to a specified pressure by supplying gas into the vacuum
vessel and simultaneously exhausting the interior of the vacuum
vessel, and thus processing the substrate or a film formed on the
substrate, the method comprising: while supplying a second
high-frequency power of a frequency lower than that of the first
high-frequency power to an electrode provided at a vacancy of the
coil, processing the substrate.
14. The plasma processing method according to claim 12, wherein the
plasma processing is an etching process of a high melting metal
film formed on the substrate.
15. The plasma processing method according to claim 14, wherein the
high melting metal film is a film containing at least one element
selected from among iridium, rhodium, ruthenium, platinum, gold,
copper, rhenium, bismuth, strontium, barium, zirconium, lead, and
niobium.
16. A plasma processing apparatus comprising: a vacuum vessel; a
gas supply unit for supplying gas into the vacuum vessel; an
exhausting unit for exhausting interior of the vacuum vessel; a
pressure-regulating valve for controlling the interior of the
vacuum vessel to a specified pressure; a substrate electrode for
placing thereon a substrate within the vacuum vessel; a coil
provided in opposition to the substrate electrode and having one
end grounded via a capacitor; a first high-frequency power supply
for supplying a first high-frequency power of a 1 MHz to 60 MHz
frequency to a feeding point which is the other end of the coil;
and a second high-frequency power supply for supplying a second
high-frequency power of a frequency lower than that of the first
high-frequency power to the coil.
17. A plasma processing apparatus comprising: a vacuum vessel; a
gas supply unit for supplying gas into the vacuum vessel; an
exhausting unit for exhausting interior of the vacuum vessel; a
pressure-regulating valve for controlling the interior of the
vacuum vessel to a specified pressure; a substrate electrode for
placing thereon a substrate within the vacuum vessel; a coil
provided in opposition to the substrate electrode; a first
high-frequency power supply for supplying a first high-frequency
power of a 1 MHz to 60 MHz frequency to a feeding point which is
one end of the coil; and a second high-frequency power supply for
supplying a second high-frequency power of a frequency lower than
that of the first high-frequency power to an electrode provided at
a vacancy of the coil.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a plasma processing method
and apparatus to be used for manufacture of semiconductor or other
electron devices and micromachines.
[0002] In the manufacture of semiconductor or other electron
devices and micromachines, thin-film processing techniques using
plasma processing have been becoming increasingly important in
recent years.
[0003] As an example of conventional plasma processing methods,
plasma processing using a patch-antenna type plasma source is
described below with reference to FIG. 3. Referring to FIG. 3,
while interior of a vacuum vessel 51 is maintained to a specified
pressure by introducing a specified gas from a gas supply unit 52
into the vacuum vessel 51 and simultaneously performing exhaustion
by a turbo-molecular pump 53 as an exhausting unit, a
high-frequency power of 100 MHz is supplied by an antenna use
high-frequency power supply 54 to an antenna 55 provided so as to
project into the vacuum vessel 51. Then, plasma is generated in the
vacuum vessel 51, allowing plasma processing to be carried out with
a substrate 57 placed on a substrate electrode 56.
[0004] There is also provided a substrate-electrode use
high-frequency power supply 58 for supplying high-frequency power
to the substrate electrode 56, making it possible to control ion
energy that reaches the substrate 57. The high-frequency power
supplied to the antenna 45 is fed to a proximity of the center of
the antenna 55 via an antenna-use matching circuit 59 by a feed bar
60. A dielectric plate 61 is sandwiched between the antenna 55 and
the vacuum vessel 51, and the feed bar 60 serves to connect the
antenna 55 and the antenna-use high-frequency power supply 54 to
each other via a through hole provided in the dielectric plate 61.
Also, the surface of the antenna 55 is covered with an antenna
cover 65.
[0005] Further, a slit 64 is provided so as to comprise a
groove-shaped space between the dielectric plate 61 and a
dielectric ring 62 provided at a peripheral portion of the
dielectric plate 61, and a groove-shaped space between the antenna
55 and a conductor ring 63 provided at a peripheral portion of the
antenna 55.
[0006] The turbo-molecular pump 53 and an exhaust port 73 are
disposed just under the substrate electrode 56, and a
pressure-regulating valve 74 for controlling the vacuum vessel 51
to a specified pressure is an up-and-down valve disposed just under
the substrate electrode 56 and just over the turbo-molecular pump
53. The substrate electrode 56 is fixed to the vacuum vessel 51
with four pillars 75.
[0007] In the plasma processing described in the prior-art example,
however, etching a high melting metal film formed on the substrate
57 would involve deposition of an electrically conductive deposited
film on the antenna cover 65, in which case poor
close-contactability of the conductive deposited film or occurrence
of abnormal discharge at the surface of the antenna cover 65 would
make it more likely to occur that the conductive deposited film
would be peeled off, falling onto the substrate 57 as dust in some
cases. According to a result of the present inventors' experiments,
when the substrate 57 coated with a 200 nm thick iridium film was
etched to a quantity of 7 pieces, 1000 or more dust particles
having 0.23 .mu.m or larger particle diameters were generated on
the substrate 57.
[0008] Further, in the plasma processing described in the prior-art
example, there is another issue that the temperature of the antenna
cover 65 increases due to plasma exposure. Since the antenna cover
65 and the antenna 55 are vacuum-insulated from each other, the
temperature of the antenna cover 65 gradually increases over
repeated plasma processing. According to a result of the present
inventors' experiments, it was found that the temperature of the
antenna cover 65 increases up to 170.degree. C. after 5-min. plasma
processing and 1-min. vacuum holding is repeated six times. Such an
abrupt change in the temperature of the antenna cover 65 may cause
not only occurrence of dust but also cracks of the antenna cover
65.
[0009] In view of these and other prior-art issues, an object of
the present invention is to provide a plasma processing method and
apparatus which is less liable to occurrence of dust and cracks of
the antenna cover.
SUMMARY OF THE INVENTION
[0010] In order to achieve the above object, the present invention
has the following constitution.
[0011] According to a first aspect of the present invention, there
is provided a plasma processing method for generating plasma in a
vacuum vessel, by supplying a high-frequency power of a 30 MHz to 3
GHz frequency to an antenna provided within the vacuum vessel in
opposition to a substrate placed on a substrate electrode within
the vacuum vessel while interior of the vacuum vessel is controlled
to a specified pressure by supplying gas into the vacuum vessel and
simultaneously exhausting the interior of the vacuum vessel, and
thus processing a high melting metal (high melting temperature
metal) film formed on the substrate,
[0012] the method comprising:
[0013] additionally supplying a high-frequency power of a 100 kHz
to 20 MHz frequency different from the above frequency to the
antenna to process the substrate.
[0014] According to a second aspect of the present invention, there
is provided the plasma processing method according to the first
aspect, wherein the high melting metal film is a film containing at
least one element selected from among iridium, rhodium, ruthenium,
platinum, gold, copper, rhenium, bismuth, strontium, barium,
zirconium, lead, and niobium.
[0015] According to a third aspect of the present invention, there
is provided the plasma processing method according to the first
aspect, wherein the substrate is processed with temperature of the
antenna controlled by giving a flow of a refrigerant to the antenna
while heat conduction between the antenna and an antenna cover is
ensured by an electrically conductive sheet which is disposed
between the antenna and the antenna cover and whose surface
parallel to the substrate is larger in surface area than that of
the antenna, and further the substrate is processed while a
self-bias voltage is generated up to an end portion of the cover by
additionally supplying the high-frequency power of the 100 kHz to
20 MHz frequency different from the above frequency to the
antenna.
[0016] According to a fourth aspect of the present invention, there
is provided the plasma processing method according to the third
aspect, wherein the plasma processing is an etching process of the
high melting metal film formed on the substrate.
[0017] According to a fifth aspect of the present invention, there
is provided the plasma processing method according to the fourth
aspect wherein the high melting metal film is a film containing at
least one element selected from among iridium, rhodium, ruthenium,
platinum, gold, copper, rhenium, bismuth, strontium, barium,
zirconium, lead, and niobium.
[0018] According to a sixth aspect of the present invention, there
is provided a plasma processing apparatus comprising:
[0019] a vacuum vessel;
[0020] a gas supply unit for supplying gas into the vacuum
vessel;
[0021] an exhausting unit for exhausting interior of the vacuum
vessel;
[0022] a pressure-regulating valve for controlling the interior of
the vacuum vessel to a specified pressure;
[0023] a substrate electrode for placing thereon a substrate within
the vacuum vessel;
[0024] an antenna provided in opposition to the substrate electrode
and covered with an insulating antenna cover;
[0025] a first high-frequency power supply capable of supplying a
high-frequency power of a 30 MHz to 3 GHz frequency to the
antenna;
[0026] a second high-frequency power supply capable of additionally
supplying a high-frequency power of a 100 kHz to 20 MHz frequency
different from the above frequency to the antenna;
[0027] a refrigerant supply unit for making a refrigerant flow to
the antenna; and
[0028] an electrically conductive sheet whose surface parallel to
the substrate is larger than that of the antenna and which is
provided between the antenna and the antenna cover.
[0029] According to a seventh aspect of the present invention,
there is provided the plasma processing apparatus according to the
sixth aspect, wherein the antenna cover is made of quartz
glass.
[0030] According to an eighth aspect of the present invention,
there is provided the plasma processing apparatus according to the
sixth aspect, wherein the antenna cover is made of insulative
silicon.
[0031] According to a ninth aspect of the present invention, there
is provided the plasma processing apparatus according to the sixth
aspect, wherein the antenna cover is 1 mm to 10 mm thick.
[0032] According to a 10th aspect of the present invention, there
is provided the plasma processing apparatus according to the sixth
aspect, wherein the electrically conductive sheet is made of a
material having a resistivity of not more than 10
.OMEGA..multidot.m.
[0033] According to an 11th aspect of the present invention, there
is provided the plasma processing apparatus according to the sixth
aspect, wherein the electrically conductive sheet is 0.03 mm to 3
mm thick.
[0034] According to a 12th aspect of the present invention, there
is provided a plasma processing method for generating
inductive-coupling type plasma in a vacuum vessel by placing a
substrate on a substrate electrode within the vacuum vessel,
supplying a first high-frequency power of a 1 MHz to 60 MHz
frequency to a feeding point which is one end of a coil provided in
opposition to the substrate electrode while interior of the vacuum
vessel is controlled to a specified pressure by supplying gas into
the vacuum vessel and simultaneously exhausting the interior of the
vacuum vessel, and thus processing the substrate or a film formed
on the substrate,
[0035] the method comprising:
[0036] while supplying a second high-frequency power of a frequency
lower than that of the first high-frequency power to the coil with
the other end of the coil grounded via a capacitor, processing the
substrate.
[0037] According to a 13th aspect of the present invention, there
is provided a plasma processing method for generating
inductive-coupling type plasma in a vacuum vessel by placing a
substrate on a substrate electrode within the vacuum vessel,
supplying a first high-frequency power of a 1 MHz to 60 MHz
frequency to a feeding point which is one end of a coil provided in
opposition to the substrate electrode while interior of the vacuum
vessel is controlled to a specified pressure by supplying gas into
the vacuum vessel and simultaneously exhausting the interior of the
vacuum vessel, and thus processing the substrate or a film formed
on the substrate,
[0038] the method comprising:
[0039] while supplying a second high-frequency power of a frequency
lower than that of the first high-frequency power to an electrode
provided at a vacancy of the coil, processing the substrate.
[0040] According to a 14th aspect of the present invention, there
is provided the plasma processing method according to the 12th
aspect, wherein the plasma processing is an etching process of a
high melting metal film formed on the substrate.
[0041] According to a 15th aspect of the present invention, there
is provided the plasma processing method according to the 14th
aspect, wherein the high melting metal film is a film containing at
least one element selected from among iridium, rhodium, ruthenium,
platinum, gold, copper, rhenium, bismuth, strontium, barium,
zirconium, lead, and niobium.
[0042] According to a 16th aspect of the present invention, there
is provided a plasma processing apparatus comprising:
[0043] a vacuum vessel;
[0044] a gas supply unit for supplying gas into the vacuum
vessel;
[0045] an exhausting unit for exhausting interior of the vacuum
vessel;
[0046] a pressure-regulating valve for controlling the interior of
the vacuum vessel to a specified pressure;
[0047] a substrate electrode for placing thereon a substrate within
the vacuum vessel;
[0048] a coil provided in opposition to the substrate electrode and
having one end grounded via a capacitor;
[0049] a first high-frequency power supply for supplying a first
high-frequency power of a 1 MHz to 60 MHz frequency to a feeding
point which is the other end of the coil; and
[0050] a second high-frequency power supply for supplying a second
high-frequency power of a frequency lower than that of the first
high-frequency power to the coil.
[0051] According to a 17th aspect of the present invention, there
is provided a plasma processing apparatus comprising:
[0052] a vacuum vessel;
[0053] a gas supply unit for supplying gas into the vacuum
vessel;
[0054] an exhausting unit for exhausting interior of the vacuum
vessel;
[0055] a pressure-regulating valve for controlling the interior of
the vacuum vessel to a specified pressure;
[0056] a substrate electrode for placing thereon a substrate within
the vacuum vessel;
[0057] a coil provided in opposition to the substrate
electrode;
[0058] a first high-frequency power supply for supplying a first
high-frequency power of a 1 MHz to 60 MHz frequency to a feeding
point which is one end of the coil; and
[0059] a second high-frequency power supply for supplying a second
high-frequency power of a frequency lower than that of the first
high-frequency power to an electrode provided at a vacancy of the
coil.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] These and other aspects and features of the present
invention will become clear from the following description taken in
conjunction with the preferred embodiments thereof with reference
to the accompanying drawings, in which:
[0061] FIG. 1 is a sectional view showing constitution of a plasma
processing apparatus used in a first embodiment of the present
invention;
[0062] FIG. 2 is a sectional view showing constitution of a plasma
processing apparatus used in a second embodiment of the present
invention;
[0063] FIG. 3 is a sectional view showing constitution of a plasma
processing apparatus used in a prior-art example;
[0064] FIG. 4 is a sectional view showing constitution of a plasma
processing apparatus used in a third embodiment of the present
invention;
[0065] FIG. 5 is a perspective view showing constitution of a
plasma processing apparatus used in a fourth embodiment of the
present invention, as it is seen through;
[0066] FIG. 6 is a sectional view showing constitution of a plasma
processing apparatus used in a fifth embodiment of the present
invention;
[0067] FIG. 7 is a perspective view showing constitution of a
plasma processing apparatus used in a sixth embodiment of the
present invention, as it is seen through;
[0068] FIG. 8 is a perspective view showing constitution of a
plasma processing apparatus used in a seventh embodiment of the
present invention, as it is seen through;
[0069] FIG. 9 is a sectional view showing constitution of a plasma
processing apparatus used in an eighth embodiment of the present
invention; and
[0070] FIG. 10 is a sectional view showing constitution of a plasma
processing apparatus used in a prior-art example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] Before the description of the present invention proceeds, it
is to be noted that like parts are designated by like reference
numerals throughout the accompanying drawings.
[0072] Hereinbelow, embodiments of the present invention will be
described in detail with reference to the accompanying
drawings.
[0073] A plasma processing method and apparatus according to a
first embodiment of the present invention is described below with
reference to FIG. 1.
[0074] FIG. 1 is a sectional view of the plasma processing
apparatus with a patch antenna type plasma source mounted thereon,
which is used in the first embodiment of the present invention.
Referring to FIG. 1, while interior of a vacuum vessel 1 is
maintained to a specified pressure by introducing a specified gas
from a gas supply unit 2 into the vacuum vessel 1 serving as one
example of a vacuum chamber and simultaneously performing
exhaustion by a turbo-molecular pump 3 as an exhausting unit, a
high-frequency power of a 100 MHz frequency is supplied by an
antenna use high-frequency power supply 4 to an antenna 5. As a
result of this, plasma is generated in the vacuum vessel 1,
allowing plasma processing to be carried out on a substrate 7
placed on a substrate electrode 6.
[0075] There is also provided a substrate-electrode use
high-frequency power supply 8 for supplying high-frequency power of
400 kHz to the substrate electrode 6, making it possible to control
ion energy that reaches the substrate 7. The high-frequency power
supplied to the antenna 5 is fed to a proximity of the center of
the antenna 5 by a feed bar 10 via an antenna-use matching circuit
9. A dielectric plate 11 composed of a dielectric material is
sandwiched between the antenna 5 and the vacuum vessel 1, and the
feed bar 10 extends through a through hole provided in the
dielectric plate 11 to be brought into contact with the antenna 5.
Further, a slit 14 is provided so as to comprise a groove-shaped
space between the dielectric plate 11 and a dielectric ring 12
provided at a peripheral portion of the dielectric plate 11, and a
ring-shaped and groove-shaped space between the antenna 5 and a
conductor ring 13 provided at a peripheral portion of the antenna
5. An inner side face of the slit 14 and the antenna 5 are covered
with a 5 mm thick antenna cover 15 made of quartz glass. An
electrically conductive sheet 16 whose surface parallel to the
substrate 7 is larger than the antenna 5 is provided between the
antenna 5 and the antenna cover 15. The conductive sheet 16 is 1 mm
thick. Also, a refrigerant feed apparatus 17 for making a
refrigerant flow to the antenna 5 is provided, and a refrigerant
flow passage 18 is formed inside the antenna 5, while an
inlet/outlet passage for the refrigerant is provided within the
feed bar 10.
[0076] A high-frequency power of a 500 kHz frequency is supplied to
the antenna 5 from a self-bias generation use high-frequency power
supply 19 via a self-bias use matching circuit 20. A 100 MHz trap
(trap circuit) 21 is provided to prevent the high-frequency power
of a 100 MHz frequency for use of plasma generation from mixing
into the self-bias use matching circuit 20, and further, a
high-pass filter 22 is provided to prevent the 500 kHz
high-frequency power from mixing into the antenna-use matching
circuit 9 for use of plasma generation.
[0077] The turbo-molecular pump 3 and an exhaust port 23 are
disposed just under the substrate electrode 6, and a
pressure-regulating valve 24 for controlling the vacuum vessel 1 to
a specified pressure is an up-and-down valve disposed just under
the substrate electrode 6 and just over the turbo-molecular pump 3.
The substrate electrode 6 is fixed to the vacuum vessel 1 with four
pillars 25.
[0078] With the plasma processing apparatus of the above-described
constitution, as one example, the substrate 7 coated with a 200 nm
thick iridium film was etched to a quantity of 100 pieces under the
conditions that while the internal pressure of the vacuum vessel 1
was maintained to 0.5 Pa by supplying 145 sccm of argon gas and 15
sccm of chlorine gas into the vacuum vessel 1, 1500 W of a 100 MHz
high-frequency power for plasma generation and 500 W of a 500 kHz
high-frequency power for self-bias generation were supplied to the
antenna 5, and simultaneously 400 W of a 400 kHz high-frequency
power was supplied to the substrate electrode 6. As a result of
this, only 50 or less dust particles having 0.23 .mu.m or larger
particle diameters were generated on the substrate 7, which led to
a dramatic improvement over the prior art in terms of the quantity
of substrates that can be continuously processed without performing
wet maintenance of the vacuum vessel 1.
[0079] This can be attributed to the fact that generating a
self-bias voltage in the antenna cover 15 made it possible to
efficiently prevent any deposition of a conductive deposited film
on the antenna cover 15. In fact, examining the surface state of
the antenna cover 15 after a 100-piece etching process of the
substrate 7 coated with an iridium film showed no formation of any
conductive deposited film. Also, since the size of the surface of
the antenna 5 parallel to the substrate 7 is quite smaller than the
size of the surface of the antenna cover 15 parallel to the
substrate 7, it would be considered difficult to generate a
self-bias voltage up to end portions of the antenna cover 15.
However, in the first embodiment, by virtue of the provision of the
conductive sheet 16 whose surface parallel to the substrate 7 is
larger than that of the antenna 5, the self-bias voltage was able
to be generated up to the end portions of the antenna cover 15.
[0080] Further, when 5-min. plasma processing and 1-min. vacuum
holding were repeated 100 times with the refrigerant temperature
held at 25.degree. C., the temperature of the antenna cover 15 was
maintained at 100.degree. C. or less. The reason of this can be
considered that a thin conductive sheet 16 was interleaved between
the antenna cover 15 and the antenna 5 and that the antenna 5 was
cooled by a refrigerant. Whereas a carbon sheet (NICAFIIM made by
Nippon Carbon Co., Ltd.) was used as the conductive sheet 16 in
this experiment, the conductive sheet 16 is soft, making close
contact with the antenna 5 and the antenna cover 15, and thin,
having a great effect in accelerating heat exchange between the
antenna cover 15 and the antenna 5. As a result of carrying out
plasma processing while the temperature of the antenna cover 15 was
controlled as described above, there was no occurrence of cracks of
the antenna cover 15.
[0081] The above-described first embodiment of the present
invention has exemplified only a part of many variations on
configuration of the vacuum vessel, structure and arrangement of
the plasma source, and the like out of the application range of the
present invention. Needless to say, other many variations are
conceivable in applying the present invention, other than the
example given above.
[0082] Whereas the present invention has been exemplified by a case
where the plasma processing is an etching of a substrate coated
with an iridium film, the present invention is also applicable to
other various etching processes or plasma CVD processes. However,
the present invention is effective particularly for etching of high
melting metal (high melting temperature metal) films, because the
etching process of such films is accompanied with a higher
likelihood that a conductive deposited film may be deposited on the
antenna cover. The high melting metal film is not limited to
iridium, and the present invention is particularly effective for
the etching process of a film containing at least one element
selected from among rhodium, ruthenium, platinum, gold, copper,
rhenium, bismuth, strontium, barium, zirconium, lead, and
niobium.
[0083] Whereas the present invention has been exemplified by a case
where the antenna cover is given by 5 mm thick quartz glass, the
antenna cover might also be given by other ceramic based materials
or insulative silicon. However, ceramic based materials, which
contain impurities in larger part, could make a cause of dust or
contamination, hence rather being not preferable. Meanwhile, using
insulative silicon produces an effect of improving the etching
selection ratio in the etching process of insulating films such as
silicon oxide or the like. Further, since too thin an antenna cover
would cause an insufficiency of mechanical strength, and since too
thick an antenna cover would cause the cooling efficiency to lower
due to a heat storage effect, the antenna cover is, preferably,
about 1 mm to 10 mm thick.
[0084] Whereas the present invention has been exemplified by a case
where the conductive sheet is a uniform-in-thickness, 1 mm thick
carbon sheet, thickness and material of the conductive sheet are
not limited to these. It is preferable, however, that the thermal
conductivity of the conductive sheet is not less than 0.1
W/m.multidot.K. The conductive sheet is desirably soft and highly
close-contactable in order to fulfill the heat exchange between the
antenna and the antenna cover, but too thin a conductive sheet
would make it hard to absorb the insufficiency of planarity of the
antenna or the antenna cover and too thick a conductive sheet would
cause the conductive sheet itself to increase in heat capacity,
thus the conductive sheet being preferably about 0.03 mm to 3 mm
thick. Further, a larger resistivity of the conductive sheet would
lead to occurrence of loss due to an effect of the high-frequency
power supplied to the antenna, which in some cases would lead to
occurrence of heat generation or melting of the sheet, thus the
resistivity being desirably not more than 10
.OMEGA..multidot.m.
[0085] Also, the above embodiment has been described on a case
where the frequency of the high-frequency power for plasma
generation applied to the antenna is 100 MHz. However, for the
patch antenna used in the present invention, frequencies of 30 MHz
to 3 GHz can be used.
[0086] Also, the above embodiment has been described on a case
where the frequency of the self-bias use high-frequency power
applied to the antenna is 500 kHz. However, high-frequency power of
other frequencies, e.g. 100 kHz to 20 MHz, can be used.
Nevertheless, in order to effectively generate the self-bias
voltage to the antenna cover, it is preferable to use a
high-frequency power of about 100 kHz to 1 MHz.
[0087] Also, the above embodiment has been described on a case
where the frequency of the high-frequency power supplied to the
substrate electrode is 400 kHz. However, it is needless to say that
high-frequency power of other frequencies, e.g. 100 kHz to 100 MHz,
can be used for the control of ion energy that reaches the
substrate. Otherwise, without the supply of high-frequency power to
the substrate electrode, it is also possible to carry out plasma
processing with weak ion energy by making use of a slight
difference between plasma potential and substrate potential.
Furthermore, using a frequency different from the frequency of the
self-bias use high-frequency power supplied to the antenna has an
advantage that interference of high frequencies can be avoided.
[0088] A case where a plasma processing method and apparatus
according to a second embodiment of the present invention having
such a constitution as shown in FIG. 2 that uses no antenna cover
is used is also within the application range of the present
invention. Referring to FIG. 2, while interior of a vacuum vessel 1
is maintained to a specified pressure by introducing a specified
gas from a gas supply unit 2 into the vacuum vessel 1 serving as
one example of a vacuum chamber and simultaneously performing
exhaustion by a turbo-molecular pump 3 as an exhausting unit, a
high-frequency power of a 100 MHz frequency is supplied by an
antenna use high-frequency power supply 4 to an antenna 5. As a
result of this, plasma is generated in the vacuum vessel 1,
allowing plasma processing to be carried out on a substrate 7
placed on a substrate electrode 6. There is also provided a
substrate-electrode use high-frequency power supply 8 for supplying
high-frequency power of 400 kHz to the substrate electrode 6,
making it possible to control ion energy that reaches the substrate
7. The high-frequency power supplied to the antenna 5 is fed to a
proximity of the center of the antenna 5 by a feed bar 10 via an
antenna-use matching circuit 9. A dielectric plate 11 constructed
by a dielectric material is sandwiched between the antenna 5 and
the vacuum vessel 1, and the feed bar 10 extends through a through
hole provided in the dielectric plate 11.
[0089] A high-frequency power of a 500 kHz frequency is supplied to
the antenna 5 from a self-bias generation use high-frequency power
supply 19 via a self-bias use matching circuit 20. A 100 MHz trap
(trap circuit) 21 is provided to prevent the high-frequency power
of a 100 MHz frequency for use of plasma generation from mixing
into the self-bias use matching circuit 20, and further, a
high-pass filter 22 is provided to prevent the 500 kHz
high-frequency power from mixing into the antenna-use matching
circuit 9 for use of plasma generation.
[0090] The turbo-molecular pump 3 and an exhaust port 23 are
disposed just under the substrate electrode 6, and a
pressure-regulating valve 24 for controlling the vacuum vessel 1 to
a specified pressure is an up-and-down valve disposed just under
the substrate electrode 6 and just over the turbo-molecular pump 3.
The substrate electrode 6 is fixed to the vacuum vessel 1 with four
pillars 25.
[0091] Also with the plasma processing apparatus shown in FIG. 2,
the deposition of conductive deposited film on the antenna can
effectively be prevented in the etching process of high melting
metal.
[0092] As apparent from the above description, according to the
plasma processing method in the first aspect of the present
invention, there is provided the plasma processing method in which
the substrate is placed on the substrate electrode within the
vacuum vessel, and the plasma is generated by supplying the
high-frequency power of a 30 MHz to 3 GHz frequency to the antenna
provided in opposition to the substrate electrode while interior of
the vacuum vessel is controlled to the specified pressure by
supplying gas into the vacuum vessel and simultaneously exhausting
the interior of the vacuum vessel and thus etching is performed on
the high melting metal film formed on the substrate, wherein the
substrate is processed wall which a high-frequency power of a 100
kHz to 20 MHz frequency different from the above frequency is
additionally supplied to the antenna. Therefore, the plasma
processing method which is less liable to occurrence of dust can be
provided.
[0093] Also, according to the plasma processing method in the third
aspect of the present invention, there is provided the plasma
processing method in which the substrate is placed on the substrate
electrode within the vacuum vessel, and the plasma is generated by
supplying the high-frequency power of a 30 MHz to 3 GHz frequency
to the antenna provided in opposition to the substrate electrode
and covered with the insulating antenna cover while interior of the
vacuum vessel is controlled to the specified pressure by supplying
gas into the vacuum vessel and simultaneously exhausting the
interior of the vacuum vessel and thus the substrate is processed,
wherein the substrate is processed with temperature of the antenna
controlled by giving a flow of the refrigerant to the antenna while
ensuring heat conduction between the antenna and the antenna cover
by the electrically conductive sheet which is disposed between the
antenna and the antenna cover and whose surface parallel to the
substrate is larger in size than the antenna, and further the
substrate is processed while the self-bias voltage is generated up
to an end portion of the cover by additionally supplying the
high-frequency power of the 100 kHz to 20 MHz frequency different
from the above frequency to the antenna. Therefore, the plasma
processing method which is less liable to occurrence of dust and
cracks of the antenna cover can be provided.
[0094] Also, according to the plasma processing apparatus in the
sixth aspect of the present invention, there is provided the plasma
processing apparatus comprising: the vacuum vessel; the gas supply
unit for supplying gas into the vacuum vessel; the exhausting unit
for exhausting interior of the vacuum vessel; the
pressure-regulating valve for controlling the interior of the
vacuum vessel to the specified pressure; the substrate electrode
for placing thereon the substrate within the vacuum vessel; the
antenna provided in opposition to the substrate electrode and
covered with the insulating antenna cover; the high-frequency power
supply capable of supplying the high-frequency power of the 30 MHz
to 3 GHz frequency to the antenna; the high-frequency power supply
capable of additionally supplying the high-frequency power of the
100 kHz to 20 MHz frequency different from the above frequency to
the antenna; and the refrigerant supply unit for making the
refrigerant flow to the antenna, wherein the electrically
conductive sheet whose surface parallel to the substrate is larger
in size than the antenna and which is provided between the antenna
and the antenna cover. Therefore, the plasma processing apparatus
which is less liable to occurrence of dust and cracks of the
antenna cover can be provided.
[0095] Next, an object of plasma processing methods and apparatuses
according to third to eighth embodiments of the present invention
is to provide a plasma processing method and apparatus which is
less liable to occurrence of dust and capable of obtaining a stable
etching rate.
[0096] First of all, plasma processing using an inductive-coupling
type plasma source is described below as an example of prior-art
plasma processing methods with reference to FIG. 10. Referring to
FIG. 10, while interior of a vacuum vessel 201 is maintained to a
specified pressure with a pressure-regulating valve 204 by
introducing a specified gas from a gas supply unit 202 into the
vacuum vessel 201 and simultaneously performing exhaustion by a
turbo-molecular pump 203 as an exhausting unit, a high-frequency
power of 13.56 MHz is supplied by a coil use high-frequency power
supply 205 to a coil 208 provided along a dielectric plate 207
opposed to a substrate electrode 206. Then, inductive-coupling type
plasma is generated in the vacuum vessel 201, allowing plasma
processing to be carried out on a substrate 209 placed on the
substrate electrode 206. There is also provided a
substrate-electrode use high-frequency power supply 210 for
supplying a high-frequency power to the substrate electrode 206,
making it possible to control ion energy that reaches the substrate
209. The turbo-molecular pump 203 and an exhaust port 211 are
disposed just under the substrate electrode 206, and the
pressure-regulating valve 204 is an up-and-down valve disposed just
under the substrate electrode 206 and just over the turbo-molecular
pump 203. The substrate electrode 206 is fixed to the vacuum vessel
201 with four pillars 212.
[0097] In the plasma processing described in the prior-art example,
however, there has been an issue that a deposited film caused by
reaction is more likely to be deposited onto the inner wall surface
of the dielectric plate 207 during continued process. In
particular, etching a high melting metal film formed on the
substrate 209 would involve deposition of an electrically
conductive deposited film on the dielectric plate 207, in which
case poor close-contactability of the conductive deposited film or
occurrence of abnormal discharge at the surface of the dielectric
plate 207 would make it more likely to occur that the conductive
deposited film would be peeled off, falling onto the substrate 209
as dust in some cases. According to a result of our experiments,
when the substrate 209 coated with a 200 nm thick iridium film was
etched to a quantity of 50 pieces, 1000 or more dust particles
having 0.23 .mu.m or larger particle diameters were generated on
the substrate 209.
[0098] Further, in the plasma processing described in the prior-art
example, there is another issue that continued etching of the
substrate 209 with an iridium film would cause a conductive
deposited film to be deposited onto the dielectric plate 207 so
that the conductive deposited film makes a shielding against the
high-frequency electromagnetic field generated from the coil 208,
causing an induction field formed within the vacuum vessel 201 to
be weakened, with a result of lowered plasma density and,
therefore, lowered etching rate. According to a result of our
experiments, as a result of etching the substrate 209 coated with a
200 nm thick iridium film to a quantity of 50 pieces, whereas the
initial etching rate was 102 nm/min., the etching rate after a
50-piece etching process lowered to 81 nm/min.
[0099] Accordingly, the plasma processing methods and apparatuses
according to the third to eighth embodiments of the present
invention are intended to provide plasma processing methods and
apparatuses which are less liable to occurrence of dust and capable
of obtaining a stable etching rate.
[0100] First, the third embodiment of the present invention is
described below with reference to FIG. 4.
[0101] FIG. 4 is a sectional view of a plasma processing apparatus
with an inductive-coupling type plasma source mounted thereon,
which is used in the third embodiment of the present invention.
Referring to FIG. 4, while interior of a vacuum vessel 101 is
maintained to a specified pressure with a pressure-regulating valve
104 by introducing a specified gas from a gas supply unit 102 into
the vacuum vessel 101 serving as one example of a vacuum chamber
and simultaneously performing exhaustion by a turbo-molecular pump
103 as an exhausting unit, a first high-frequency power of 13.56
MHz is supplied by a coil-use first high-frequency power supply 105
to a coil 108 provided along a dielectric plate 107 opposed to a
substrate electrode 106. Then, inductive-coupling type plasma is
generated in the vacuum vessel 101, allowing plasma processing to
be carried out on a substrate 109 placed on the substrate electrode
106 or on a film formed on the substrate 109. There is also
provided a substrate-electrode use high-frequency power supply 110
for supplying a high-frequency power to the substrate electrode
106, making it possible to control ion energy that reaches the
substrate 109. The turbo-molecular pump 103 and an exhaust port 111
are disposed just under the substrate electrode 106, and the
pressure-regulating valve 104 is an up-and-down valve disposed just
under the substrate electrode 106 and just over the turbo-molecular
pump 103. The substrate electrode 106 is fixed to the vacuum vessel
101 with four pillars 112.
[0102] A feeding point 113, which is one end of the coil 108, is
located at the center of a spiral formed by the coil 108. The other
end 114 of the coil 108 is grounded via a capacitor 115. The
capacitor 115 has a capacity of 1000 pF. Further, a coil-use second
high-frequency power supply 116 for supplying a second
high-frequency power of a 500 kHz frequency, lower than 13.56 MHz
of the first high-frequency power, to the coil 108 is provided and
connected to the feeding point 113 of the coil 108.
[0103] Also, a band-pass filter 117 is provided as a circuit for
preventing any influences of modulation by the second
high-frequency power from being exerted on the detection circuit
system for reflected waves of the first high-frequency power. This
is intended to eliminate any effects of fluctuations of the sheath
thickness of the surface of the dielectric plate 107 by 500 kHz due
to the supply of the second high-frequency power and to thereby
take out and detect only the 13.56 MHz component out of the
reflected waves of the first high-frequency power. In such an
arrangement, carrying out processes while monitoring the reflected
waves of the first high-frequency power by a reflected-wave meter
118 makes it possible to detect any trouble with the matching state
or the coil-use first high-frequency power supply in real time. In
addition, assuming that the frequency of the first high-frequency
power is f.sub.1 and the frequency of the second high-frequency
power is f.sub.2, the band-pass filter 117 preferably has such
frequency characteristics that its center frequency is set to a
proximity of f.sub.1 and that its damping factor is 10 dB or more
at f.sub.1.+-.f.sub.2.
[0104] With the plasma processing apparatus of the above-described
constitution, as one example, the substrate 109 coated with a 200
nm thick iridium film was etched to a quantity of 50 pieces under
the conditions that while the internal pressure of the vacuum
vessel 101 was maintained to 0.5 Pa by supplying 145 sccm of argon
gas and 15 sccm of chlorine gas into the vacuum vessel 101, 1500 W
of the first high-frequency power and 500 W of the second
high-frequency power were supplied to the coil 108, and
simultaneously 400 W of a 400 kHz high-frequency power was supplied
to the substrate electrode 106. As a result of this, only 50 or
less dust particles having 0.23 .mu.m or larger particle diameters
were generated on the substrate 109, which led to a dramatic
improvement over the prior art in terms of the quantity of
substrates that can be continuously processed without performing
wet maintenance of the vacuum vessel 101. Also, whereas the initial
etching rate was 102 nm/min., the etching rate after a 50-piece
etching process lowered to 101 nm/min., thus freeing from
occurrence of such lowering of etching rate as would be seen in the
prior art.
[0105] This can be attributed to the fact that an ion bombardment
was generated on the surface of the dielectric plate 107 as a
result of capacitively coupling the coil 108 and plasma together,
making it possible to effectively prevent the deposition of any
conductive deposited film on the dielectric plate 107. In fact,
examining the surface state of the dielectric plate 107 after a
50-piece etching process of the substrate 109 coated with an
iridium film showed no formation of any conductive deposited
film.
[0106] The above-described embodiment of the present invention has
exemplified only a part of many variations on configuration of the
vacuum vessel, structure and arrangement of the plasma source, and
the like out of the application range of the present invention.
Needless to say, other many variations are conceivable in applying
the present invention, other than the example given above.
[0107] For example, as shown in the fourth embodiment of the
present invention in FIG. 5, the coil 108A may also be of a
multiple spiral type. In this case, the coil 108A is low in
inductance, having an advantage that a good matching state can more
easily be obtained for high frequencies or large-scale coils.
Further, as shown in the fifth embodiment of the present invention
in FIG. 6, the coil 108B may be of a cylindrical type. In this
case, a dielectric cylinder 119 is used in place of the dielectric
plate.
[0108] The above-described third embodiment of the present
invention has been exemplified by a case where the frequency of the
first high-frequency power is 13.56 MHz and the frequency of the
second high-frequency power is 500 kHz. However, it is considered
preferable that the frequency of the second high-frequency power is
not more than {fraction (1/10)} of the frequency of the first
high-frequency power. In the third embodiment of the present
invention, since the capacity of the capacitor 115 is 1000 pF, the
impedance of the capacitor for the first high-frequency power
is
1/(2.pi..times.13.56.times.10.sup.6.times.1000.times.10.sup.-12)=12
.OMEGA..
[0109] For the second high-frequency power, on the other hand, the
impedance is
1/(2.pi..times.500.times.10.sup.3.times.1000.times.10.sup.-12)=320
.OMEGA..
[0110] Since the inductance of the coil 108 was 0.8 .mu.H, the
impedance of the coil 108 for the first high-frequency power is
2.pi..times.13.56.times.10.sup.6.times.0.8.times.10.sup.-6=68
.OMEGA..
[0111] For the second high-frequency power, on the other hand, the
impedance is
2.pi..times.500.times.10.sup.3.times.0.8.times.10.sup.-6=2.5
.OMEGA..
[0112] Therefore, the ratio of a voltage applied to the coil 108 to
a voltage applied to the capacitor 115 for the first high-frequency
power is
68.div.12=5.7,
[0113] and for the second high-frequency power, it is
2.5.div.320=0.0078.
[0114] Therefore, it can be understood that a series circuit of the
coil 108 and the capacitor 115 is nearly inductive (coil component)
as viewed from the first high-frequency power, and nearly
capacitive (capacitor component) as viewed from the second
high-frequency power. That is, while inductive-coupling type plasma
is generated with the first high-frequency power, the coil 108 and
the plasma can be capacitively coupled together with the second
high-frequency power so that an ion bombardment due to the
self-bias voltage can be given to the surface of the dielectric
plate 107 or the dielectric cylinder 119. It can be considered that
such a relationship holds when the frequency of the second
high-frequency power is not more than generally {fraction (1/10)}
of the frequency of the first high-frequency power. If the
frequency of the second high-frequency power is larger than
{fraction (1/10)} of the frequency of the first high-frequency
power, the difference in the ratio of the voltage applied to the
coil 108 to the voltage applied to the capacitor 115 between the
first high-frequency power and the second high-frequency power
would be too small, making it hard to expect the intended
effect.
[0115] Even in the prior-art example, since the high-frequency
voltage is relatively large in vicinities of the center of the coil
108, there would occur some degree of ion bombardment due to the
self-bias voltage in vicinities of the center of the dielectric
plate 107. However, since the high-frequency voltage is low in
vicinities of the outer periphery of the coil 108, there would
occur almost no ion bombardment due to the self-bias voltage in
vicinities of the outer periphery of the dielectric plate 107.
Further, the present invention has an advantage that plasma density
is controlled by the magnitude of the first high-frequency power
and, independently of this, the ion bombardment can be controlled
by the magnitude of the second high-frequency power.
[0116] Also, if the impedance of the coil against the first
high-frequency power is not less than a double of the impedance of
the capacitor and the impedance of the coil against the second
high-frequency power is not more than {fraction (1/5)} of the
impedance of the capacitor, then enough difference in the ratio of
the voltage applied to the coil 108 to the voltage applied to the
capacitor 115 between the first high-frequency power and the second
high-frequency power can be obtained, which is considered
effective. When these conditions are not satisfied, there would
result too small a difference in the ratio of the voltage applied
to the coil 108 to the voltage applied to the capacitor 115 between
the first high-frequency power and the second high-frequency power,
making it hard to expect the intended effect. In addition, when
multiple coils are used as in the fourth embodiment of the present
invention, it is appropriate that the impedance be considered for
each one pair of coil and capacitor.
[0117] Also, if the impedance of the capacitor against the first
high-frequency power is not more than 25 .OMEGA. and the impedance
of the capacitor against the second high-frequency power is not
less than 250 .OMEGA., then enough difference in the ratio of the
voltage applied to the coil 108 to the voltage applied to the
capacitor 115 between the first high-frequency power and the second
high-frequency power can be obtained, which is considered
effective. When these conditions are not satisfied, there would
result too small a difference in the ratio of the voltage applied
to the coil 108 to the voltage applied to the capacitor 115 between
the first high-frequency power and the second high-frequency power,
making it hard to expect the intended effect. In addition, when
multiple coils are used as in the fourth embodiment of the present
invention, it is appropriate that the impedance be considered for
each one pair of coil and capacitor.
[0118] Also, if the impedance of the coil against the first
high-frequency power is not less than 50 .OMEGA. and the impedance
of the coil against the second high-frequency power is not more
than 5 .OMEGA., then enough difference in the ratio of the voltage
applied to the coil 108 to the voltage applied to the capacitor 115
between the first high-frequency power and the second
high-frequency power can be obtained, which is considered
effective. When these conditions are not satisfied, there would
result too small a difference in the ratio of the voltage applied
to the coil 108 to the voltage applied to the capacitor 115 between
the first high-frequency power and the second high-frequency power,
making it hard to expect the intended effect. In addition, when
multiple coils are used as in the fourth embodiment of the present
invention, it is appropriate that the impedance be considered for
each one pair of coil and capacitor.
[0119] Next, a sixth embodiment of the present invention is
described with reference to FIG. 7.
[0120] FIG. 7 is a perspective view of a plasma processing
apparatus having an inductive-coupling type plasma source mounted
thereon, which is used in the sixth embodiment of the present
invention. Referring to FIG. 7, while interior of a vacuum vessel
101 is maintained to a specified pressure with a
pressure-regulating valve 104 by introducing a specified gas from a
gas supply unit 102 into the vacuum vessel 101 and simultaneously
performing exhaustion by a turbo-molecular pump 103 as an
exhausting unit, a first high-frequency power of 13.56 MHz is
supplied by a coil-use first high-frequency power supply 105 to a
coil 108 provided along a dielectric plate 107 opposed to a
substrate electrode 106. Then, inductive-coupling type plasma is
generated in the vacuum vessel 101, allowing plasma processing to
be carried out with a substrate 109 placed on the substrate
electrode 106 or with a film formed on the substrate 109. There is
also provided a substrate-electrode use high-frequency power supply
110 for supplying high-frequency power to the substrate electrode
106, making it possible to control ion energy that reaches the
substrate 109. The turbo-molecular pump 103 and an exhaust port 111
are disposed just under the substrate electrode 106, and the
pressure-regulating valve 104 is an up-and-down valve disposed just
under the substrate electrode 106 and just over the turbo-molecular
pump 103. The substrate electrode 106 is fixed to the vacuum vessel
101 with four pillars 112.
[0121] A feeding point 113, which is one end of the coil 108, is
located at the center of a spiral formed by the coil 108. Further,
there is provided an electrode-use second high-frequency power
supply 116 for supplying a second high-frequency power of a
frequency, which is lower than the frequency of the first
high-frequency power, to an electrode 120 provided at a vacancy of
the coil. Although the second high-frequency power is applied to
the center of the spiral formed by the electrode 120 in this
embodiment, yet it may also be applied to an outer peripheral end
of the spiral and moreover the feeding points do not necessarily
need to be end portions. Also, the electrode 120 is not
grounded.
[0122] Also, a band-pass filter 117 is provided as a circuit for
preventing any influences of modulation by the second
high-frequency power from being exerted on the detection circuit
system for reflected waves of the first high-frequency power. This
is intended to eliminate any effects of fluctuations of the sheath
thickness of the surface of the dielectric plate 107 by 500 kHz due
to the supply of the second high-frequency power and to thereby
take out and detect only the 13.56 MHz component out of the
reflected waves of the first high-frequency power. In such an
arrangement, carrying out processes while monitoring the reflected
waves of the first high-frequency power by a reflected-wave meter
118 makes it possible to detect any trouble with the matching state
or the coil-use first high-frequency power supply in real time. In
addition, assuming that the frequency of the first high-frequency
power is f.sub.1 and the frequency of the second high-frequency
power is f.sub.2, the band-pass filter 117 preferably has such
frequency characteristics that its center frequency is set to a
proximity of f.sub.1 and that its damping factor is 10 dB or more
at f.sub.1.+-.f.sub.2.
[0123] With the plasma processing apparatus of the above-described
constitution, as one example, the substrate 109 coated with a 200
nm thick iridium film was etched to a quantity of 50 pieces under
the conditions that while the internal pressure of the vacuum
vessel 101 was maintained to 0.5 Pa by supplying 145 sccm of argon
gas and 15 sccm of chlorine gas into the vacuum vessel 101, 1500 W
of the first high-frequency power was supplied to the coil 108 and
500 W of the second high-frequency power was supplied to the
electrode 120, and simultaneously 400 W of a 400 kHz high-frequency
power was supplied to the substrate electrode 106. As a result of
this, only 50 or less dust particles having 0.23 .mu.m or larger
particle diameters were generated on the substrate 109, which led
to a dramatic improvement over the prior art in terms of the
quantity of substrates that can be continuously processed without
performing wet maintenance of the vacuum vessel 101. Also, whereas
the initial etching rate was 98 nm/min., the etching rate after a
50-piece etching process was 97 nm/min., thus freeing from
occurrence of such lowering of etching rate as would be seen in the
prior art.
[0124] This can be attributed to the fact that an ion bombardment
was generated on the surface of the dielectric plate 107 as a
result of capacitively coupling the electrode 120 and plasma
together, making it possible to effectively prevent the deposition
of any conductive deposited film on the dielectric plate 107. In
fact, examining the surface state of the dielectric plate 107 after
a 50-piece etching process of the substrate 109 coated with an
iridium film showed no formation of any conductive deposited
film.
[0125] The above-described embodiment of the present invention has
exemplified only a part of many variations on configuration of the
vacuum vessel, structure and arrangement of the plasma source, and
the like out of the application range of the present invention.
Needless to say, other many variations are conceivable in applying
the present invention, other than the example given above.
[0126] For example, as shown in the seventh embodiment of the
present invention in FIG. 8, the coil 108 may also be of a multiple
spiral type. In this case, the coil 108 is low in inductance,
having an advantage that a good matching state can more easily be
obtained for high frequencies or large-scale coils. In this case,
preferably, the electrode 120 is also of a multiple spiral
structure as a whole as shown in FIG. 8. Further, as shown in the
eighth embodiment of the present invention in FIG. 9, the coil 108
may be of a cylindrical type. In this case, a dielectric cylinder
119 is used in place of the dielectric plate. Further, preferably,
the electrode 120B is also of a cylindrical spiral
configuration.
[0127] The above sixth embodiment of the present invention has been
exemplified by a case where the frequency of the high-frequency
power is 13.56 MHz and the frequency of the second high-frequency
power is 500 kHz. However, it is considered preferable that the
frequency of the second high-frequency power is not more than
{fraction (1/10)} of the frequency of the first high-frequency
power. With such a relationship, there is an advantage that
interference between the first high-frequency power and the second
high-frequency power is less likely to occur.
[0128] Whereas the above embodiment of the present invention has
been exemplified by a case where the plasma processing is an
etching of a substrate coated with an iridium film, the present
invention is also applicable to other various etching processes and
plasma CVD processes. This is because in general there are many
cases where the deposition of a deposited film onto the dielectric
plate or the dielectric cylinder would matter in etching process or
plasma CVD process. However, the present invention is effective
particularly for etching of high melting metal films, because the
etching process of such films is accompanied by a higher likelihood
that a conductive deposited film may be deposited on the dielectric
plate or the dielectric cylinder. The high melting metal film is
not limited to iridium, and the present invention is particularly
effective for the etching process of films containing at least one
element selected from among rhodium, ruthenium, platinum, gold,
copper, rhenium, bismuth, strontium, barium, zirconium, lead, and
niobium.
[0129] Also, the above embodiments have been exemplified by a case
where the frequency of the first high-frequency power supplied to
the coil is 13.56 MHz. However, in order to effectively generate
the inductive-coupling type plasma, it is preferable to use
frequencies of 1 MHz to 60 MHz. Frequencies lower than 1 MHz would
cause a drawback that enough plasma density could not be obtained,
while frequencies higher than 60 MHz would cause occurrence of
standing waves to the coil, making it quite hard to obtain uniform
plasma.
[0130] Also, the above embodiments have been exemplified by a case
where the frequency of the high-frequency power supplied to the
substrate electrode is 400 kHz. However, it is needless to say that
high-frequency power of other frequencies, e.g. 100 kHz to 100 MHz,
can be used for the control of ion energy that reaches the
substrate. Otherwise, without the supply of high-frequency power to
the substrate electrode, it is also possible to carry out plasma
processing with weak ion energy by making use of a slight
difference between plasma potential and substrate potential.
Furthermore, as to the frequency of the high-frequency power
supplied to the substrate electrode, using a frequency different
from the frequency of the second high-frequency power supplied to
the coil or the electrode has an advantage that interference of
high frequencies can more easily be avoided.
[0131] As apparent from the above description, according to the
plasma processing method in the 12th aspect of the present
invention, there is provided the plasma processing method in which
the substrate is placed on the substrate electrode within the
vacuum vessel, and the inductive-coupling type plasma is generated
in the vacuum vessel by supplying the first high-frequency power of
a 1 MHz to 60 MHz frequency to the feeding point which is one end
of the coil provided in opposition to the substrate electrode while
interior of the vacuum vessel is controlled to the specified
pressure by supplying the gas into the vacuum vessel and
simultaneously exhausting the interior of the vacuum vessel and
thus the substrate or the film formed on the substrate is
processed, wherein the substrate is processed while the second
high-frequency power of a frequency lower than that of the first
high-frequency power is supplied to the coil with the other end of
the coil grounded via the capacitor. Therefore, the plasma
processing method which is less liable to occurrence of dust and
capable of obtaining a stable etching rate can be provided.
[0132] Also, according to the plasma processing method in the 13th
aspect of the present invention, there is provided the plasma
processing method in which the substrate is placed on the substrate
electrode within the vacuum vessel, the inductive-coupling type
plasma is generated in the vacuum vessel by supplying the first
high-frequency power of a 1 MHz to 60 MHz frequency to the feeding
point which is one end of the coil provided in opposition to the
substrate electrode while interior of the vacuum vessel is
controlled to the specified pressure by supplying the gas into the
vacuum vessel and simultaneously exhausting the interior of the
vacuum vessel, and thus the substrate or the film formed on the
substrate is processed, wherein the substrate is processed while
the second high-frequency power of a frequency lower than that of
the first high-frequency power is supplied to the electrode
provided at the vacancy of the coil to process the substrate.
Therefore, the plasma processing method which is less liable to
occurrence of dust and capable of obtaining a stable etching rate
can be provided.
[0133] Also, according to the plasma processing apparatus in the
16th aspect of the present invention, there is provided the plasma
processing apparatus comprising: the vacuum vessel; the gas supply
unit for supplying the gas into the vacuum vessel; the exhausting
unit for exhausting the interior of the vacuum vessel; the
pressure-regulating valve for controlling the interior of the
vacuum vessel to the specified pressure; the substrate electrode
for placing thereon the substrate within the vacuum vessel; the
coil provided in opposition to the substrate electrode; and the
first high-frequency power supply for supplying the first
high-frequency power of the 1 MHz to 60 MHz frequency to the
feeding point which is one end of the coil, wherein the other end
of the coil is grounded via the capacitor, and the plasma
processing apparatus further comprises the second high-frequency
power supply for supplying the second high-frequency power of a
frequency lower than that of the first high-frequency power to the
coil. Therefore, the plasma processing apparatus which is less
liable to occurrence of dust and capable of obtaining a stable
etching rate can be provided.
[0134] Also, according to the plasma processing apparatus in the
17th aspect of the present invention, there is provided the plasma
processing apparatus comprising: the vacuum vessel; the gas supply
unit for supplying the gas into the vacuum vessel; the exhausting
unit for exhausting the interior of the vacuum vessel; the
pressure-regulating valve for controlling the interior of the
vacuum vessel to the specified pressure; the substrate electrode
for placing thereon the substrate within the vacuum vessel; the
coil provided in opposition to the substrate electrode; the first
high-frequency power supply for supplying the first high-frequency
power of a 1 MHz to 60 MHz frequency to the feeding point which is
one end of the coil, wherein the plasma processing apparatus
further comprises the second high-frequency power supply for
supplying the second high-frequency power of a frequency lower than
that of the first high-frequency power to the electrode provided at
the vacancy of the coil. Therefore, the plasma processing apparatus
which is less liable to occurrence of dust and capable of obtaining
a stable etching rate can be provided.
[0135] In addition, combining any arbitrary embodiments together
appropriately from among the foregoing various embodiments allows
their respective effects to be produced.
[0136] Although the present invention has been fully described in
connection with the preferred embodiments thereof with reference to
the accompanying drawings, it is to be noted that various changes
and modifications are apparent to those skilled in the art. Such
changes and modifications are to be understood as included within
the scope of the present invention as defined by the appended
claims unless they depart therefrom.
* * * * *