U.S. patent application number 14/934066 was filed with the patent office on 2016-05-05 for plasma processing apparatus and plasma processing method.
The applicant listed for this patent is TOKYO ELECTRON LIMITED. Invention is credited to Chishio KOSHIMIZU, Tatsuo MATSUDO, Jun YAMAWAKU.
Application Number | 20160126064 14/934066 |
Document ID | / |
Family ID | 55853447 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160126064 |
Kind Code |
A1 |
YAMAWAKU; Jun ; et
al. |
May 5, 2016 |
PLASMA PROCESSING APPARATUS AND PLASMA PROCESSING METHOD
Abstract
A plasma processing apparatus includes a high frequency antenna
having first and second antenna elements. One end of the first
antenna element is grounded and the other end thereof is connected
to a high frequency power supply. One end of the second antenna
element is an open end and the other end thereof is connected to
either one of the one end and the other end of the first antenna
element, a line length of the second antenna element having a value
obtained by multiplying ((.lamda./4)+n.lamda./2) by a fractional
shortening (.lamda. is a wavelength of high frequency in vacuum and
n is a natural number). A circuit viewed from the high frequency
power supply toward the high frequency antenna is configured to
generate, when a frequency of a high frequency power is changed,
two resonant frequencies by an adjustment of the impedance
adjustment unit.
Inventors: |
YAMAWAKU; Jun; (Yamanashi,
JP) ; MATSUDO; Tatsuo; (Yamanashi, JP) ;
KOSHIMIZU; Chishio; (Yamanashi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRON LIMITED |
Tokyo |
|
JP |
|
|
Family ID: |
55853447 |
Appl. No.: |
14/934066 |
Filed: |
November 5, 2015 |
Current U.S.
Class: |
216/67 ;
315/111.21 |
Current CPC
Class: |
H01J 37/3211 20130101;
H01J 37/32651 20130101; H01J 2237/334 20130101; H01J 37/32183
20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2014 |
JP |
2014-225519 |
Claims
1. A plasma processing apparatus for performing a process on a
substrate mounted on a mounting unit in a processing chamber of a
vacuum atmosphere by exciting a processing gas supplied into the
processing chamber and generating plasma, the plasma processing
apparatus comprising: a high frequency antenna formed of a vortex
coil arranged opposite to a processing target surface of the
substrate mounted on the mounting unit, the high frequency antenna
being connected to a high frequency power supply that is a variable
frequency power supply and including a first antenna element and a
second antenna element; an impedance adjustment unit including
variable-capacity capacitors for adjusting a resonant frequency of
a circuit viewed from the high frequency power supply toward the
high frequency antenna; a dielectric configured to airtightly
isolate a vacuum atmosphere in the processing chamber from a space
in which the high frequency antenna is arranged; and a shield
member configured to surround the space in which the high frequency
antenna is arranged, wherein one end of the first antenna element
is grounded and the other end thereof is connected to the high
frequency power supply, wherein one end of the second antenna
element is an open end and the other end thereof is connected to
either one of the one end of the first antenna element and the
other end of the first antenna element, a line length of the second
antenna element having a value obtained by multiplying
((.lamda./4)+n.lamda./2) by a fractional shortening, where .lamda.
is a wavelength of high frequency in vacuum and n is a natural
number, and the second antenna element being set to resonate at a
power frequency to be used, and wherein the circuit viewed from the
high frequency power supply toward the high frequency antenna is
configured to generate, when a frequency of a high frequency power
is changed, a first resonant frequency and a second resonant
frequency by an adjustment of the impedance adjustment unit.
2. The plasma processing apparatus of claim 1, wherein the
variable-capacity capacitors of the impedance adjustment unit
include a variable-capacity capacitor provided between the high
frequency power supply and the high frequency antenna and connected
in series to the high frequency power supply, and a
variable-capacity capacitor provided between the other end of the
second antenna element and an earth.
3. The plasma processing apparatus of claim 1, wherein the
variable-capacity capacitors of the impedance adjustment unit
include a variable-capacity capacitor for adjusting a reflectivity
of high frequency which is connected in parallel to the high
frequency power supply.
4. The plasma processing apparatus of claim 2, wherein the
variable-capacity capacitors of the impedance adjustment unit
further include a variable-capacity capacitor for adjusting a
reflectivity of high frequency which is connected in parallel to
the high frequency power supply.
5. A plasma processing method using the plasma processing apparatus
of claim 1, the plasma processing method comprising: supplying,
from the high frequency power supply to the high frequency antenna,
a high frequency power having a frequency between the first
resonant frequency and the second resonant frequency; and
performing a plasma-process on the substrate.
6. A plasma processing method using the plasma processing apparatus
of claim 2, the plasma processing method comprising: supplying,
from the high frequency power supply to the high frequency antenna,
a high frequency power having a frequency between the first
resonant frequency and the second resonant frequency; and
performing a plasma-process on the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2014-225519 filed on Nov. 5, 2014, the entire
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a plasma processing
apparatus and a plasma processing method which perform a process on
a substrate by exciting a processing gas.
BACKGROUND OF THE INVENTION
[0003] As one of the semiconductor manufacturing processes, there
is a plasma process such as an etching process, a film forming
process or the like which uses plasma of a reaction gas. For
example, in a single-subatrate plasma processing apparatus, it is
required to properly control the plasma density distribution to
become appropriate in a plane direction of a substrate depening on
a process type, specifically based on a structure in a processing
chamber or in consideration of in-plane deviation of the substrate
in a post-porcess. Therefore, the requirement is not limited to
making the plasma density distribution uniform in the entire
surface of the substrate and may include making the plasma density
distribution different between a central portion and a peripheral
portion of the substrate.
[0004] As one of the plasma generating method in the plasma
processing apparatus, there is a method in which, e.g., a high
frequency power is supplied to an antenna and an induced electric
field is generated in a processing chamber to excite a processing
gas. For example, Japanese Patent No. 4178775 discloses a method in
which a coil corresponding to a monopole antenna is provided around
a reaction vessel of a vertical type furnace so as to surround the
processing chamber, and an induced electric field is generated in
the processing chamber to excite a processing gas and generate
plasma. This configuration may make easy the adjustment of the
plasma density in an arrangement direction of substrates but is not
suitable for the adjustment of the plasma density in the surface of
each substrate.
[0005] Japanese Patent Application Publication No. 2010-258324
discloses a configuration in which a coil-shaped inner antenna and
a coil-shaped outer antenna formed concentric to the inner antenna
are provided as a high frequency antenna which outputs a high
frequency, and each of antennas resonates at a frequency of 1/2
wavelength of the high frequency. In this plasma processing
apparatus, a circular electric field is formed by each antenna, and
thus in-plane distribution of the plasma density can be very finely
adjusted. However, a high frequency power supply needs to be
provided at each of the inner antenna and the outer antenna.
[0006] Japanese Patent Application Publication No. 2014-075579
discloses a plasma processing apparatus in which a monopole antenna
surrounds around a processing chamber. Japanese Patent No. 2613002
discloses a technique in which a semiconductor wafer is effectively
processed by increasing the plasma density. Japanese Patent
Application Publication No. H08-017799 discloses a plasma
processing apparatus in which an impedance element is connected
between a substrate holder and an earth. However, the above
documents all do not achieve the object of the present
invention.
SUMMARY OF THE INVENTION
[0007] In view of the above, the present invention provides a
technique capable of adjusting in-plane distribution of the plasma
density in a plasma processing apparatus which performs a process
on a substrate by generating plasma by using a high frequency
antenna.
[0008] In accordance with an aspect, there is provided a plasma
processing apparatus for performing a process on a substrate
mounted on a mounting unit in a processing chamber of a vacuum
atmosphere by exciting a processing gas supplied into the
processing chamber and generating plasma, the plasma processing
apparatus including: a high frequency antenna formed of a vortex
coil arranged opposite to a processing target surface of the
substrate mounted on the mounting unit, the high frequency antenna
being connected to a high frequency power supply that is a variable
frequency power supply and including a first antenna element and a
second antenna element; an impedance adjustment unit including
variable-capacity capacitors for adjusting a resonant frequency of
a circuit viewed from the high frequency power supply toward the
high frequency antenna; a dielectric configured to airtightly
isolate a vacuum atmosphere in the processing chamber from a space
in which the high frequency antenna is arranged; and a shield
member configured to surround the space in which the high frequency
antenna is arranged.
[0009] One end of the first antenna element is grounded and the
other end thereof is connected to the high frequency power
supply.
[0010] One end of the second antenna element is an open end and the
other end thereof is connected to either one of the one end of the
first antenna element and the other end of the first antenna
element, a line length of the second antenna element having a value
obtained by multiplying ((.lamda./4)+n.lamda./2) by a fractional
shortening, where .lamda. is a wavelength of high frequency in
vacuum and n is a natural number, and the second antenna element
being set to resonate at a power frequency to be used.
[0011] The circuit viewed from the high frequency power supply
toward the high frequency antenna is configured to generate, when a
frequency of a high frequency power is changed, a first resonant
frequency and a second resonant frequency by an adjustment of the
impedance adjustment unit.
[0012] In accordance with another aspect, there is provided a
plasma processing method using the plasma processing apparatus
described above. The plasma processing method including: supplying,
from the high frequency power supply to the high frequency antenna,
a high frequency power having a frequency between the first
resonant frequency and the second resonant frequency; and
performing a plasma-process on the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The objects and features of the present invention will
become apparent from the following description of embodiments,
given in conjunction with the accompanying drawings, in which:
[0014] FIG. 1 is a cross sectional view showing a plasma processing
apparatus in accordance with an embodiment of the present
invention;
[0015] FIG. 2 is a perspective view showing a high frequency
antenna in the plasma processing apparatus;
[0016] FIG. 3 is a characteristic view showing resonant frequencies
generated in the high frequency antenna in accordance with the
embodiment of the present invention;
[0017] FIG. 4 is an explanatory view showing a monopole
antenna;
[0018] FIG. 5 is a characteristic view showing a resonant frequency
generated in the monopole antenna;
[0019] FIG. 6 is an explanatory view showing a high frequency
antenna in accordance with another example of the embodiment of the
present invention;
[0020] FIG. 7 is an explanatory view showing a high frequency
antenna in accordance with still another example of the embodiment
of the present invention;
[0021] FIG. 8 is an explanatory view showing a high frequency
antenna in accordance with yet still another example of the
embodiment of the present invention;
[0022] FIG. 9 is a characteristic view showing resonant frequencies
in a test example 1;
[0023] FIGS. 10A to 10D are pictures showing plasma in test
examples 2-1 to 2-4; and
[0024] FIG. 11 is a characteristic view showing a standardized
plasma density in the test examples 2-1 to 2-4.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] Hereinafter, embodiments of the present invention will be
described in detail with respect to the accompanying drawings.
[0026] A plasma processing apparatus in accordance with an
embodiment of the present invention will be described. As shown in
FIG. 1, a plasma processing apparatus is a plasma etching apparatus
using a radio frequency (RF) (high frequency) antenna formed of a
vortex coil, e.g., a plane-shaped vortex coil. The plasma
processing apparatus includes a grounded processing chamber 10 made
of, e.g., aluminum or stainless steel. A loading/unloading port 11
for loading and unloading a semiconductor wafer (hereinafter,
referred to as "wafer") W as a substrate to be processed is
installed at a sidewall of the processing chamber 10. A gate valve
13 for opening and closing the loading/unloading port 11 is
provided at the loading/unloading port 11.
[0027] A cylindrical susceptor 12 serving as a mounting unit on
which the wafer W as a substrate to be processed is mounted and
also serving as a high frequency electrode is installed at a
central portion of the bottom wall of the processing chamber 10
through a support unit 14 formed of an insulator. A high frequency
power supply 30 for RF bias is electrically connected to the
susceptor 12 through a matching unit 32 and a power feed rod 34.
The high frequency power supply 30 is capable of outputting a high
frequency power of a specific frequency (13.56 MHz or below)
suitable to control energy of ions attracted to the wafer W. The
matching unit 32 is formed of a variable reactance matching circuit
for making a matching between impedance on the side of the high
frequency power supply 30 and impedance on the side of loads
(mainly, the susceptor, the plasma and the processing chamber).
[0028] An electrostatic chuck 36 for holding the wafer W with an
electrostatic attractive force is installed on the top of the
susceptor 12. A focus ring 38 which annularly surrounds the
periphery of the wafer W is arranged at the outer side of the
electrostatic chuck 36 in a diametric direction thereof. In the
susceptor 12, an annular coolant path 44 is provided to extend in,
e.g., a circumferential direction. A coolant, e.g., a cooling water
of a predetermined temperature is circularly supplied to the
coolant path 44 through lines 46 and 48 from a chiller unit (not
shown). A process temperature of the wafer W on the electrostatic
chuck 36 can be controlled by the temperature of the coolant. One
end of a gas supply line 60 provided in the susceptor 12 is opened
at the top surface of the electrostatic chuck 36. The other end of
the gas supply line 60 is connected to a heat transfer gas supply
mechanism 61 for supplying a heat transfer gas, e.g., He gas
between the top surface of the electrostatic chuck 36 and the
backside of the wafer W.
[0029] In the susceptor 12, elevating pins (not shown) for
transferring and receiving the wafer W to and from an external
transfer arm is provided to vertically penetrate through the
susceptor 12 and protrude beyond and retract below the surface of
the electrostatic chuck 36.
[0030] A gap between the periphery of the susceptor 12 and an inner
wall surface of the processing chamber 10 is blocked by an annular
baffle plate 39 formed of a perforated plate. At the bottom wall of
the processing chamber 10, an exhaust port 15 is formed below the
baffle plate 39. A vacuum exhaust unit 17 is connected to the
exhaust port 15 through an exhaust line 16.
[0031] In the sidewall of the processing chamber 10, an annular
processing gas supply passageway 18 is formed, above the
loading/unloading port 11, along the entire circumference of the
sidewall. A plurality of processing gas supply ports 19 is formed
to be opened toward the inside of the processing chamber 10 along
the inner circumference of the processing gas supply passageway 18.
A processing gas supply mechanism 21 for supplying a processing gas
is connected to the processing gas supply passageway 18 through a
gas supply line 20. In case that the plasma processing apparatus
is, e.g., an etching apparatus, an etching gas such as ClF.sub.3,
F.sub.2 or the like is used as the processing gas. Further, in case
that the plasma processing apparatus is, e.g., a film forming
apparatus, a nitriding or oxidizing gas such as ammonia gas, ozone
gas or the like is used as the processing gas.
[0032] At a ceiling plate part of the processing chamber 10, a
dielectric window 22 formed of, e.g., quartz plate is installed to
face the electrostatic chuck 36 so as to airtightly isolate the
vacuum atmosphere in the processing chamber 10 from the atmospheric
atmosphere above the dielectric window 22. At the top surface of
the dielectric window 22, a high frequency antenna 5 formed of a
vortex-shaped planar coil is provided opposite to the top surface
of the susceptor 12 with the dielectric window 22 therebetween. In
this example, the high frequency antenna 5 is mounted on the
dielectric window 22. A space in which the high frequency antenna 5
is arranged is surrounded by a shield box 9 that is a grounded
shield member.
[0033] Also referring to FIG. 2, a high frequency power supply 50
that is a variable frequency power supply is connected to an inner
end 6 of the high frequency antenna 5 through a wiring 53. On the
wiring 53 between the high frequency power supply 50 and the inner
end 6 of the high frequency antenna 5, a first variable-capacity
capacitor 55 is provided in series to the high frequency power
supply 50. Between a connection point of the high frequency power
supply 50 to the first variable-capacity capacitor 55 and an earth
electrode, a second variable-capacity capacitor 56 is provided in
parallel to the high frequency power supply 50. An outer end 7 of
the high frequency antenna 5 is an open end. A portion between the
inner end 6 and the outer end 7 (hereinafter, referred to as
"middle portion") is grounded through a wiring 54 while a third
variable-capacity capacitor 57 is provided on the wiring 54. A
conductive path is indicated as the wirings 53 and 54 in FIGS. 1
and 2, but specifically, the high frequency antenna 5 and a
terminal portion of the shield box 9 are connected to each other by
a strap-shaped copperplate in the shield box 9, and a coaxial cable
is used in the outside of the shield box 9.
[0034] A line length from the inner end 6 of the high frequency
antenna 5 to the middle portion 8 thereof is not particularly
limited, but is set to a length of, e.g., about 1 mm. A line length
from the middle portion 8 of the high frequency antenna 5 to the
outer end 7 thereof is set to a length of ((.lamda./4)+n.lamda./2)
(where n is a natural number, 0, 1, 2, . . . ), e.g., .lamda./4 so
that a standing wave is generated at the corresponding part to
thereby output a large high-frequency energy. Here, .lamda. is a
wavelength of electromagnetic wave in vacuum. Therefore, in order
to specify the line length in the high frequency antenna 5,
strictly, a fractional shortening is considered. Accordingly,
setting the line length to the length of ((.lamda./4)+n.lamda./2)
(where n is a natural number, 0, 1, 2, . . . ) strictly means
setting the line length to have a value obtained by multiplying
((.lamda./4)+n.lamda./2) (where n is a natural number, 0, 1, 2, . .
. ) by the fractional shortening. The fractional shortening varies
depending on how to wind a vortex coil and the surrounding
circumstances at which the high frequency antenna 5 is arranged. In
the following description, the expression of "multiplication by the
fractional shortening" will be omitted to simplify the
description.
[0035] That is, the line length from the middle portion 8 of the
high frequency antenna 5 to the outer end 7 thereof is a length of
.lamda./4 and may be set to resonate at a power frequency used. In
addition, setting the line length to a length of .lamda./4 means,
with respect to a high frequency between frequencies of two
resonance points to be later described and a high frequency near
the frequencies of the two resonance points, setting the line
length to a length that is considered to be able to generate an
effective standing wave suitable for obtaining a plasma intensity
strong enough to process the wafer W, the plasma intensity
corresponding to a part from the middle portion 8 to the outer end
7.
[0036] In the example, a part from the inner end 6 to the middle
portion 8 in the high frequency antenna 5 constitutes a first high
frequency antenna element 51 and is regarded as a coil for
generating an electric field by electromagnetic induction. A part
from the middle portion 8 to the outer end 7 constitutes a second
high frequency antenna element 52 and is regarded as a spiral
antenna formed of a monopole antenna.
[0037] When a circuit including the high frequency antenna 5 is
viewed from the high frequency power supply 50, as shown in FIG. 3,
two resonant frequencies (resonance points) exist in a frequency
variable range of the variable frequency power supply forming the
high frequency power supply 50. FIG. 3 schematically shows an
example of reflectivity variation when a frequency is changed in
the frequency variable range of the high frequency power supply 50
while respective capacities of the first to third variable-capacity
capacitors 55 to 57 are fixed to certain values. A reflectivity
indicated by an arrow in FIG. 3 can be changed by adjusting the
first to third variable-capacity capacitors 55 to 57. By doing so,
a relative power balance between a high frequency energy of the
first high frequency antenna element 51 and a high frequency energy
of the second high frequency antenna element 52 can be
controlled.
[0038] The first variable-capacity capacitor 55 functions as an
impedance matching circuit and corresponds, together with the third
variable-capacity capacitor 57, to an impedance adjustment unit for
adjusting two resonant frequencies. The two resonant frequencies
result from the first high frequency antenna element 51 and the
second high frequency antenna element 52, respectively. However, it
cannot be found that which resonant frequency comes from the first
high frequency antenna element 51 or from the second high frequency
antenna element 52.
[0039] The second variable-capacity capacitor 56 functions to
adjust a reflectivity of when the high frequency antenna 5 is seen
from the high frequency power supply 50. By the adjustment of the
reflectivity, impedance adjusted by the first and third
variable-capacity capacitors 55 and 57 is changed. Therefore, the
second variable-capacity capacitor also functions to adjust the
resonant frequencies. Accordingly, in this example, the first to
third variable-capacity capacitors 55 to 57 may be regarded as the
impedance adjustment unit for adjusting the resonant
frequencies.
[0040] When a distance between the high frequency antenna 5 and the
shield box 9 is changed, a capacity therebetween is also changed.
Therefore, the first resonant frequency and the second resonant
frequency may be adjusted by, e.g., providing a height adjustment
mechanism for the high frequency antenna 5 including an elevating
mechanism, or providing in the shield box 9 a plate electrically
connected to the shield box 9 and changing the height position of
the plate. In this example, the height adjustment mechanism of the
high frequency antenna 5 and the grounded plate are not provided,
so that the resonant frequencies are adjusted by the first
variable-capacity capacitor 55 and the third variable-capacity
capacitor 57 (or by the first to third variable-capacity capacitors
55 to 57).
[0041] As such, since the two resonant frequencies are close to
each other, by setting a frequency of the high frequency power
supply 50 to a value between the two resonant frequencies, a high
frequency energy of the first high frequency antenna element 51 and
a high frequency energy of the second high frequency antenna
element 52 are distributed depending on a distance (frequency
difference) between the set frequency of the high frequency power
supply 50 and each of the two resonant frequencies. The two
resonant frequencies are adjusted by the first to third
variable-capacity capacitors 55 to 57. The first high frequency
antenna element 51 and the second high frequency antenna element 52
are respectively arranged at the inner and outer sides on a plane.
Accordingly, a plasma density distribution can be adjusted between
the periphery of the wafer W and the central portion thereof by the
first to third variable-capacity capacitors 55 to 57.
[0042] Here, referring to a well-known monopole antenna 100 shown
in FIG. 4, since a resonant frequency of an open end side from an
earthing point P of a middle portion of an antenna element 101 is
equal to a resonant frequency of a high frequency power supply side
from the earthing point P of the middle portion of the antenna
element 101, only one resonant frequency appears, as shown in FIG.
5.
[0043] Subsequently, description will be made on an operation of
the plasma processing apparatus. In advance, according to a process
for the wafer W, resonant frequencies in the high frequency antenna
5 are adjusted by the impedance adjustment unit. In this case, the
resonant frequencies may be adjusted while fixing a value of a high
frequency used, or both the resonant frequency and the high
frequency may be adjusted. From this, a position of a frequency
supplied to the high frequency antenna 5 is adjusted between the
first resonant frequency and the second resonant frequency.
[0044] For example, there may be a desire to make an etching speed
or a film forming speed in the periphery of the wafer W higher than
that in the central portion of the wafer W, or vice versa. In
response to such a demand in each process, in order to obtain a
proper plasma density distribution in a plane of the wafer W, a
relationship between an adjustment position of each of the
variable-capacity capacitors 55 to 57 and in-plane distribution
state of the process for the wafer W is previously recognized, and
an appropriate adjustment position is found. Specifically, an
actuator is provided at the first to third variable-capacity
capacitors 55 to 57 to automatically perform a capacity adjustment
and an appropriate adjustment position is written in a process
recipe. The process recipe is selected by a control unit or is
taken from a superior computer and a plasma density distribution is
formed according to the process recipe.
[0045] If the plasma processing apparatus is operated, the wafer W
as a substrate to be processed is mounted on the electrostatic
chuck 36 by a cooperative work of the external transfer arm and the
elevating pins. Next, after the gate valve 13 is closed, a heat
transfer gas is supplied between the electrostatic chuck 36 and the
wafer W, and the electrostatic chuck 36 attracts and holds the
wafer W. A temperature of the wafer W is set to a setting value by
a flow of coolant and the like.
[0046] Thereafter, a processing gas is supplied into the processing
chamber 10 through the processing gas supply port 19. A vacuum
exhaust is performed through the exhaust port 15 and a pressure in
the processing chamber 10 is controlled to a predetermined value.
Next, the high frequency power supply 50 is turned on to input a
high frequency power to the high frequency antenna 5. Further, the
high frequency power supply 30 for the susceptor 12 is turned on to
apply, to the susceptor 12 through the power feed rod 34, a high
frequency power for an ion attraction control.
[0047] In the processing chamber 10, the processing gas is excited
by a magnetic field formed based on an induction coil that is the
first high frequency antenna element 51 and a magnetic field formed
based on a standing wave of the second high frequency antenna
element 52, so that a plasma is generated and the wafer W is
processed.
[0048] In the above embodiment, the plasma processing apparatus
using inductively coupled plasma uses the vortex-shaped high
frequency antenna 5 which is configured by combining the first high
frequency antenna element 51 and the second high frequency antenna
element 52. The inner end of the first high frequency antenna
element 51 is connected to the high frequency power supply 50 and
the middle portion 8 that is an outer end of the first high
frequency antenna element 51 is grounded. The outer end 7 of the
second high frequency antenna element 52 is an open end and a line
length of the second high frequency antenna element 52 is
.lamda./4. Further, the first and second resonant frequencies,
which respectively correspond to either one of the first and second
high frequency antenna elements 51 and 52 in one-to-one
correspondence relationship, are adjusted by adjusting the first to
third variable-capacity capacitors 55 to 57. Therefore, a ratio of
the high frequency energy distributed to the first and second high
frequency antenna elements 51 and 52 can be adjusted and thus
plasma density distribution in a plane of the wafer W can be
adjusted.
[0049] In the plasma processing apparatus in accordance with the
embodiment of the present invention, instead of the high frequency
antenna 5 shown in FIGS. 1 and 2, as shown in FIG.
[0050] 6, the inner end 6 of the high frequency antenna 5 may be
grounded and the middle portion 8 thereof may be connected to the
high frequency power supply 50. Alternatively, as shown in FIG. 7,
the high frequency antenna 5 may have a configuration in which the
outer end 7 of the high frequency antenna 5 is connected to the
high frequency power supply 50, the inner end 6 thereof is an open
end, and a line length from the inner end 6 to the middle portion 8
is a length of (.lamda./4)+n.lamda./2 (where n is an integer), and
the middle portion 8 is grounded. In this example, an inner part
from the inner end 6 to the middle portion 8 in the high frequency
antenna 5 constitutes the second high frequency antenna element 52
and an outer part from the middle portion 8 to the outer end 7
constitutes the first high frequency antenna element 51.
[0051] Further, in the example in which the inner part constitutes
the second high frequency antenna element 52 and the outer part
constitutes the first high frequency antenna element 51, as shown
in FIG. 8, the outer end 7 may be grounded and the middle portion 8
may be connected to the high frequency power supply 50. In FIGS. 6
to 8, the shield box 9 is omitted in the illustration. That is, the
high frequency antenna 5 shown in FIGS. 6 to 8 is accommodated in
the shield box 9 as the aforementioned embodiment shown in FIGS. 1
and 2 and is merely different from the high frequency antenna 5 of
the aforementioned embodiment with respect to a position connected
to the high frequency power supply 50, and a grounded position or a
position of the open end.
[0052] The vortex coil that is the high frequency antenna 5 is not
limited to a plane shape. The central portion of the vortex coil
and the peripheral portion thereof may have different height
positions while the vortex coil forms a vortex when seen from
above.
[0053] A winding direction of the high frequency antenna 5 may be a
clockwise direction or a counterclockwise direction from the inner
end 6 to the outer end 7 when the high frequency antenna 5 is seen
from above.
TEST EXAMPLE 1
[0054] The following test is performed to confirm the effect of the
embodiment of the present invention. The plasma processing
apparatus shown in FIG. 1 in accordance with the embodiment of the
present invention was used. While changing a frequency of a high
frequency power supplied from the high frequency power supply 50 in
a range from 10 MHz to 60 MHz, a reflectivity was measured from the
high frequency power supply 50 side.
[0055] FIG. 9 shows the test result which is a characteristic graph
showing a frequency of the high frequency power supply 50 and the
reflectivity. According to this result, it is seen that in a
frequency variable region of the high frequency power supply 50,
the reflectivity is lowered at two frequencies of 22 MHz and 25
MHz. Therefore, it is found that a circuit using the high frequency
antenna 5 employed in the plasma processing apparatus of the
present embodiment has two resonant frequencies.
TEST EXAMPLE 2
[0056] Further, the plasma processing apparatus shown in FIG. 1 in
accordance with the embodiment of the present invention was used
and a plasma electron density in the processing chamber 10 was
measured while changing the capacities of the variable-capacity
capacitors 55 to 57. Examples in which the capacities of the
variable-capacity capacitors 55 to 57 were adjusted were
respectively indicated by test examples 2-1 to 2-4.
[0057] FIGS. 10A to 10D are pictures showing excited plasma in the
processing chamber 10 in the test examples 2-1 to 2-4,
respectively. FIG. 11 shows a characteristic graph in the test
examples 2-1 to 2-4 wherein the horizontal axis indicates a
distance from a center of the processing chamber 10 and the
vertical axis indicates a standardized Ne value which is a value of
the electron density Ne standardized by the miximum value NeMax of
the electron density Ne. According to this result, in the test
example 2-1, the standardized Ne value is high in the central
portion, but in the test example 2-2, the standardized Ne value is
high in the more outer region compared to the test example 2-1. In
the test examples 2-3 and 2-4, the standardized Ne value is highest
in an outer position than the center.
[0058] According to the result, it is found that in-plane
distribution of the plasma density formed in the processing chamber
10 can be changed by changing the capacities of the
variable-capacity capacitors 55 to 57.
[0059] While the invention has been shown and described with
respect to the embodiments, it will be understood by those skilled
in the art that various changes and modifications may be made
without departing from the scope of the invention as defined in the
following claims.
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