U.S. patent application number 09/789799 was filed with the patent office on 2001-09-13 for plasma processing method and apparatus.
Invention is credited to Matsui, Takuya, Okumura, Tomohiro.
Application Number | 20010021550 09/789799 |
Document ID | / |
Family ID | 18568059 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021550 |
Kind Code |
A1 |
Okumura, Tomohiro ; et
al. |
September 13, 2001 |
Plasma processing method and apparatus
Abstract
A plasma processing method includes evacuating a vacuum chamber
while supplying a gas into the vacuum chamber, thereby controlling
an interior of the vacuum chamber to a pressure, and supplying a
high frequency power of a frequency of 50 MHz-3 GHz to an antenna
which is set opposite to a substrate placed to a substrate
electrode in the vacuum chamber and which has a structure with a
dielectric member held between a wall face of the vacuum chamber
opposite to the substrate and a metallic plate, thereby generating
plasma inside the vacuum chamber and processing the substrate,
wherein the high frequency power is supplied to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
Inventors: |
Okumura, Tomohiro;
(Osaka-fu, JP) ; Matsui, Takuya; (Osaka-fu,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
18568059 |
Appl. No.: |
09/789799 |
Filed: |
February 22, 2001 |
Current U.S.
Class: |
438/220 ;
257/E21.252 |
Current CPC
Class: |
H01J 37/32091 20130101;
H01L 21/31116 20130101; H01J 37/32082 20130101 |
Class at
Publication: |
438/220 |
International
Class: |
H01L 021/8238 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2000 |
JP |
2000-45483 |
Claims
What is claimed is:
1. A plasma processing method comprising: evacuating a vacuum
chamber while supplying a gas into the vacuum chamber, thereby
controlling an interior of the vacuum chamber to a pressure; and
supplying a high frequency power of a frequency of 50 MHz-3 GHz to
an antenna which is set opposite to a substrate placed to a
substrate electrode in the vacuum chamber and which has a structure
with a dielectric member held between a wall face of the vacuum
chamber opposite to the substrate and a metallic plate, thereby
generating plasma inside the vacuum chamber and processing the
substrate, wherein the high frequency power is supplied to satisfy
a relation 3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
2. A plasma processing method according to claim 1, wherein in
supplying the high frequency power of the frequency of 50 MHz-3 GHz
to the antenna, the high frequency power is supplied to satisfy a
relation 3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a radius (m) of a circular shape of the dielectric
member.
3. A plasma processing method according to claim 1, wherein in
supplying the high frequency power of the frequency of 50 MHz-3 GHz
to the antenna, the high frequency power is supplied to satisfy a
relation 3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a diagonal line of a rectangular
shape of the dielectric member.
4. A plasma processing method according to claim 1, wherein in
supplying the high frequency power of the frequency of 50 MHz-3 GHz
to the antenna, the high frequency power is supplied to satisfy a
relation 3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a major axis of an ellipse shape of
the dielectric member.
5. A plasma processing method according to claim 1, wherein in
supplying the high frequency power of the frequency of 50 MHz-3 GHz
to the antenna, the high frequency power is supplied to satisfy a
relation 4r<c/(f.multidot..epsilon..sup.1/2)<8r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
6. A plasma processing method according to claim 1, wherein in
supplying the high frequency power of the frequency of 50 MHz-3 GHz
to the antenna, the high frequency power is supplied to satisfy a
relation 5r<c/(f.multidot..epsilon..sup.1/2)<7r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
7. A plasma processing method according to claim 1, further
comprising: supplying a high frequency voltage to the metallic
plate via a through hole formed to a vicinity of a center of the
dielectric member; and shortcircuiting the metallic plate and the
wall face of the vacuum chamber opposite to the substrate via
through holes formed to a plurality of points different from the
center and a periphery of the dielectric member.
8. A plasma processing method according to claim 7, wherein in
shortcircuiting the metallic plate and the wall face of the vacuum
chamber opposite to the substrate, each of the points is
shortcircuited to the vacuum chamber while each of the points is
almost isotropically arranged to the center of the antenna.
9. A plasma processing method according to claim 1, wherein in
supplying the high frequency power of the frequency of 50 MHz-3 GHz
to the antenna, the high frequency power is supplied to the antenna
while a surface of the antenna is covered with an insulating
cover.
10. A plasma processing apparatus comprising: a vacuum chamber; a
gas supply device for supplying a gas into the vacuum chamber; an
evacuation device for evacuating the vacuum chamber; a substrate
electrode used for placing a substrate in the vacuum chamber; an
antenna in a structure having a dielectric member held between a
wall face of the vacuum chamber opposite to the substrate electrode
and a metallic plate; and a high frequency power source capable of
supplying a high frequency power of a frequency of 50 MHz-3 GHz to
the antenna, the plasma processing apparatus being constituted to
supply the high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1/2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
11. A plasma processing apparatus according to claim 10, wherein
the plasma processing apparatus being constituted to supply the
high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1- /2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a radius (m) of a circular shape of the dielectric
member.
12. A plasma processing apparatus according to claim 10, wherein
the plasma processing apparatus being constituted to supply the
high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1- /2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a diagonal line of a rectangular
shape of the dielectric member.
13. A plasma processing apparatus according to claim 10, wherein
the plasma processing apparatus being constituted to supply the
high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1- /2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a major axis of an ellipse shape of
the dielectric member.
14. A plasma processing apparatus according to claim 10, wherein
the plasma processing apparatus being constituted to supply the
high frequency power to satisfy a relation
4r<c/(f.multidot..epsilon..sup.1- /2)<8r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
15. A plasma processing apparatus according to claim 10, wherein
the plasma processing apparatus being constituted to supply the
high frequency power to satisfy a relation
5r<c/(f.multidot..epsilon..sup.1- /2)<7r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
16. A plasma processing apparatus according to claim 10, wherein a
high frequency voltage is supplied to the metallic plate via a
through hole formed to a vicinity of a center of the dielectric
member, thereby shortcircuiting the metallic plate and the wall
face of the vacuum chamber opposite to the substrate via through
holes formed to a plurality of points different from the center and
a periphery of the dielectric member.
17. A plasma processing apparatus according to claim 16, wherein
each of the points to be shortcircuited to the vacuum chamber is
almost isotropically arranged to the center of the antenna.
18. A plasma processing apparatus according to claim 10, wherein a
surface of the antenna is covered with an insulating cover.
19. A plasma processing apparatus according to claim 10, wherein a
ring and groove-shaped plasma trap is set between the antenna and
vacuum chamber.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method and an apparatus
for plasma processing such as dry etching, sputtering, plasma CVD,
or the like utilized for manufacturing electronic devices and
micromachines of a semiconductor or the like, and more particularly
to the method and apparatus which utilize plasma excited with the
use of a VHF or UHF-band high frequency power.
[0002] Japanese Laid-Open Patent Publication No. 8-83696 describes
it important in the published specification to make use of
high-density plasma to cope with finely forming electronic devices
of a semiconductor or the like. In the meantime, low electron
temperature plasma having a high electron density and a low
electron temperature is attracting attention these days.
[0003] When a gas having a strong negative characteristic, in other
words, easy to generate negative ions such as Cl.sub.2, SF.sub.6,
or the like is turned to plasma and an electron temperature becomes
approximately 3eV or lower, a larger quantity of negative ions is
generated than when the electron temperature is high. Utilizing
this phenomenon can prevent an abnormality in shape of etching
named as "notch" which is caused by positive charges piled to a
bottom part of a fine pattern due to an excessive injection of
positive ions, thus enabling highly accurate etching into
remarkably fine patterns.
[0004] When a gas including carbon and fluorine such as CxFy,
CxHyFz (x, y and z are natural numbers) or the like generally used
to etch insulating films such as silicon oxide films or the like is
turned to plasma, and if the electron temperature becomes
approximately not higher than 3eV, dissociation of the gas is
restricted more than when the electron temperature is high,
particularly, generation of F atoms, F radicals, and the like is
suppressed. Since the F atoms, F radicals, and the like are fast to
etch silicon, the insulating films can be etched with a higher
etching selectivity to silicon as the electron temperature is
lower.
[0005] A temperature of ions and a potential of plasma decrease
when the electron temperature becomes not higher than 3eV, so that
ionic damage to substrates in plasma CVD can be reduced.
[0006] It is a plasma source using a VHF or UHF-band high frequency
power that receives latest attention as a technique to generate
plasma of a low electron temperature.
[0007] FIG. 10 is a sectional view of a plasma processing apparatus
of a plate-shaped antenna system. In FIG. 10, a vacuum chamber 101
is evacuated by a pump 103 as an evacuation device while a
predetermined gas is introduced from a gas supply device 102 into
the vacuum chamber 101. With the vacuum chamber 101 kept inside to
be a predetermined pressure, a high frequency power of 100 MHz is
supplied from a high frequency power source 104 for antenna to an
antenna 105. In consequence, plasma is generated in the vacuum
chamber 101, processing a substrate 107 placed on a substrate
electrode 106, for example, by etching, deposition, surface
reforming, or the like manner. At this time, a high frequency power
is also supplied from a high frequency power source 108 for
substrate electrode to the substrate electrode 106 as shown in FIG.
10, whereby an ion energy reaching the substrate 107 can be
controlled. The antenna 105 consists of a metallic plate 109 of a
radius of 115 mm and a dielectric plate 110 of a radius of 115 mm
and, is designed to supply a high frequency voltage to the metallic
plate 109 via a through hole 111 formed near the center of the
dielectric plate 110.
[0008] According to the prior art system shown in FIG. 10, it is
difficult to obtain stable plasma of a high plasma density.
[0009] The present invention has for its object to provide a method
and an apparatus whereby stable plasma of a high plasma density can
be obtained, with eliminating the above-described issue in the
prior art.
SUMMARY OF THE INVENTION
[0010] In accomplishing these and other aspects, according to a
first aspect of the present invention, there is provided a plasma
processing method comprising:
[0011] evacuating a vacuum chamber while supplying a gas into the
vacuum chamber, thereby controlling an interior of the vacuum
chamber to a pressure; and
[0012] supplying a high frequency power of a frequency of 50 MHz-3
GHz to an antenna which is set opposite to a substrate placed to a
substrate electrode in the vacuum chamber and which has a structure
with a dielectric member held between a wall face of the vacuum
chamber opposite to the substrate and a metallic plate, thereby
generating plasma inside the vacuum chamber and processing the
substrate,
[0013] wherein the high frequency power is supplied to satisfy a
relation 3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a
light velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
[0014] According to a second aspect of the present invention, there
is provided a plasma processing method according to the first
aspect, wherein in supplying the high frequency power of the
frequency of 50 MHz-3 GHz to the antenna, the high frequency power
is supplied to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a radius (m) of a circular shape of the dielectric
member.
[0015] According to a third aspect of the present invention, there
is provided a plasma processing method according to the first
aspect, wherein in supplying the high frequency power of the
frequency of 50 MHz-3 GHz to the antenna, the high frequency power
is supplied to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a diagonal line of a rectangular
shape of the dielectric member.
[0016] According to a fourth aspect of the present invention, there
is provided a plasma processing method according to the first
aspect, wherein in supplying the high frequency power of the
frequency of 50 MHz-3 GHz to the antenna, the high frequency power
is supplied to satisfy a relation
3r<c/(f.multidot..epsilon..sup.1/2)<9r when c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a major axis of an ellipse shape of
the dielectric member.
[0017] According to a fifth aspect of the present invention, there
is provided a plasma processing method according to the first
aspect, wherein in supplying the high frequency power of the
frequency of 50 MHz-3 GHz to the antenna, the high frequency power
is supplied to satisfy a relation
4r<c/(f.multidot..epsilon..sup.1/2)<8r when c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
[0018] According to a sixth aspect of the present invention, there
is provided a plasma processing method according to the first
aspect, wherein in supplying the high frequency power of the
frequency of 50 MHz-3 GHz to the antenna, the high frequency power
is supplied to satisfy a relation
5r<c/(f.multidot..epsilon..sup.1/2)<7r when c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
[0019] According to a seventh aspect of the present invention,
there is provided a plasma processing method according to the first
aspect, further comprising:
[0020] supplying a high frequency voltage to the metallic plate via
a through hole formed to a vicinity of a center of the dielectric
member; and
[0021] shortcircuiting the metallic plate and the wall face of the
vacuum chamber opposite to the substrate via through holes formed
to a plurality of points different from the center and a periphery
of the dielectric member.
[0022] According to an eighth aspect of the present invention,
there is provided a plasma processing method according to the
seventh aspect, wherein in shortcircuiting the metallic plate and
the wall face of the vacuum chamber opposite to the substrate, each
of the points is shortcircuited to the vacuum chamber while each of
the points is almost isotropically arranged to the center of the
antenna.
[0023] According to a ninth aspect of the present invention, there
is provided a plasma processing method according to the first
aspect, wherein in supplying the high frequency power of the
frequency of 50 MHz-3 GHz to the antenna, the high frequency power
is supplied to the antenna while a surface of the antenna is
covered with an insulating cover.
[0024] According to a 10th aspect of the present invention, there
is provided a plasma processing apparatus comprising:
[0025] a vacuum chamber;
[0026] a gas supply device for supplying a gas into the vacuum
chamber;
[0027] an evacuation device for evacuating the vacuum chamber;
[0028] a substrate electrode used for placing a substrate in the
vacuum chamber;
[0029] an antenna in a structure having a dielectric member held
between a wall face of the vacuum chamber opposite to the substrate
electrode and a metallic plate; and
[0030] a high frequency power source capable of supplying a high
frequency power of a frequency of 50 MHz-3 GHz to the antenna,
[0031] the plasma processing apparatus being constituted to supply
the high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..- sup.1/2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
[0032] According to an 11th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein the plasma processing apparatus being constituted
to supply the high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..- sup.1/2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a radius (m) of a circular shape of the dielectric
member.
[0033] According to a 12th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein the plasma processing apparatus being constituted
to supply the high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..- sup.1/2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a diagonal line of a rectangular
shape of the dielectric member.
[0034] According to a 13th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein the plasma processing apparatus being constituted
to supply the high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..- sup.1/2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a major axis of an ellipse shape of
the dielectric member.
[0035] According to a 14th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein the plasma processing apparatus being constituted
to supply the high frequency power to satisfy a relation
3r<c/(f.multidot..epsilon..- sup.1/2)<9r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a major axis of an ellipse shape of
the dielectric member.
[0036] According to a 15th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein the plasma processing apparatus being constituted
to supply the high frequency power to satisfy a relation
5r<c/(f.multidot..epsilon..- sup.1/2)<7r wherein c is a light
velocity (m/sec), f is a frequency (Hz) of the high frequency
power, .epsilon. is a relative permittivity of the dielectric
member and, r is a half (m) of a longer line of a shape of the
dielectric member.
[0037] According to a 16th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein a high frequency voltage is supplied to the
metallic plate via a through hole formed to a vicinity of a center
of the dielectric member, thereby shortcircuiting the metallic
plate and the wall face of the vacuum chamber opposite to the
substrate via through holes formed to a plurality of points
different from the center and a periphery of the dielectric
member.
[0038] According to a 17th aspect of the present invention, there
is provided a plasma processing apparatus according to the 16th
aspect, wherein each of the points to be shortcircuited to the
vacuum chamber is almost isotropically arranged to the center of
the antenna.
[0039] According to an 18th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein a surface of the antenna is covered with an
insulating cover.
[0040] According to a 19th aspect of the present invention, there
is provided a plasma processing apparatus according to the 10th
aspect, wherein a ring and groove-shaped plasma trap is set between
the antenna and vacuum chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] 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:
[0042] FIG. 1 is a sectional view showing a structure of a plasma
processing apparatus employed in a first embodiment of the present
invention;
[0043] FIG. 2 is a diagram showing measured results of an ion
saturation current density immediately above a substrate with a
relative permittivity of a dielectric plate changed from 4 to
90;
[0044] FIG. 3 is a sectional view showing a structure of a plasma
processing apparatus used in a second embodiment of the present
invention;
[0045] FIG. 4 is a sectional view showing a structure of a plasma
processing apparatus used in a third embodiment of the present
invention;
[0046] FIG. 5 is a sectional view showing a structure of a plasma
processing apparatus used in a fourth embodiment of the present
invention;
[0047] FIG. 6 is a sectional view showing a structure of a plasma
processing apparatus used in a fifth embodiment of the present
invention;
[0048] FIG. 7 is a sectional view showing a structure of a plasma
processing apparatus used in a sixth embodiment of the present
invention;
[0049] FIG. 8 is a diagram showing measured results of an ion
saturation current density immediately above a substrate with a
relative permittivity of a dielectric plate changed from 14 to
28;
[0050] FIG. 9 is a diagram showing measured results of an ion
saturation current density immediately above a substrate with a
relative permittivity of a dielectric plate changed from 11 to
45;
[0051] FIG. 10 is a sectional view showing a structure of a plasma
processing apparatus employed in a first embodiment of a
conventional example;
[0052] FIG. 11A is a plan view of the dielectric plate having a
circular shape;
[0053] FIG. 11B is a plan view of a dielectric plate having a
rectangular shape; and
[0054] FIG. 11C is a plan view of a dielectric plate having an
ellipse shape.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0055] 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.
[0056] A first embodiment of the present invention will be
described below with reference to FIG. 1.
[0057] FIG. 1 is a sectional view of a plasma processing apparatus
of a plate-shaped antenna system according to the first embodiment
of the present invention. In FIG. 1, a vacuum chamber 1 is
evacuated by a pump 3 as an evacuation device while a predetermined
gas is introduced from a gas supply device 2 into the vacuum
chamber. With the vacuum chamber 1 kept inside to be a
predetermined pressure, a high frequency power of 100 MHz is
supplied from a high frequency power source 4 for antenna to an
antenna 5. In consequence, plasma is generated in the vacuum
chamber 1, processing a substrate 7 placed on a substrate electrode
6, for example, by etching, deposition, surface reforming or the
like manner. At this time, a high frequency power is also supplied
from a high frequency power source 8 for substrate electrode to the
substrate electrode 6 as shown in FIG. 1, whereby an ion energy
reaching the substrate 7 can be controlled. The antenna 5 consists
of a metallic plate 9 of a radius of 115 mm and a dielectric plate
10 of a radius of 115 mm and, is designed to supply a high
frequency voltage to the metallic plate 9 via a through hole 11
formed near the center of the dielectric plate 10.
[0058] When a relative permittivity of a dielectric plate 10 is
changed from 4 to 90 while a plasma generation condition is fixed
to that a gas is Cl.sub.2, a flow rate of the gas is 100 sccm, a
pressure is 1.3 Pa, and a high frequency power for antenna is 1 kW,
an ion saturation current density measured immediately above a
substrate 7 is as indicated in FIG. 2. It is clear from FIG. 2 that
the ion saturation current density decreases when the relative
permittivity of the dielectric plate 10 is approximately 8 or
smaller. When the relative permittivity of the dielectric plate 10
is larger than approximately 80, plasma is turned instable and the
ion saturation current density cannot be measured.
[0059] Generally, supposed that a light velocity is c (m/sec) and a
frequency of electromagnetic waves is f (Hz), a wavelength
.lambda.(m) of electromagnetic waves in a medium of a relative
permittivity of .epsilon. is expressed by:
.lambda.=c/(f.multidot..epsilon..sup.1/2)
[0060] That is, the wavelength .lambda. is inversely proportional
to the relative permittivity .epsilon..sup.1/2. Since an outer
circumferential part of the dielectric plate 10 which is an exit
for electromagnetic waves from the antenna 5 is a free end, an
electric field strength is weak in the vicinity of the center in
the dielectric plate 10, whereas the electric field strength is
strong at the outer circumferential part. In order to enhance the
electric field strength at the outer circumferential part, it is
effective to reduce the wavelength in the dielectric plate 10
thereby increasing a phase difference to the vicinity of the
center. Thus, an increase in relative permittivity of the
dielectric plate 10 is considered to increase the electric field
strength at the outer circumferential part of the dielectric plate
10, with a high ion saturation current density effectuated.
[0061] On the other hand, if the relative permittivity of the
dielectric plate 10 is increased too much, the wavelength in the
dielectric plate 10 is shortened too much, letting an
electromagnetic field of a high-order mode to the dielectric plate
10 to be allowed and result in a mix state with a fundamental mode.
Plasma is turned instable consequently.
[0062] The above result indicates it necessary to set the relative
permittivity of the dielectric plate 10 within some range so as to
obtain stable plasma of a high plasma density. Since the frequency
f of the high frequency power for antenna is 100 MHz=100,000,000 Hz
and the radius r of the dielectric plate 10 is 115 mm=0.115 m,
stable plasma of a high plasma density can be obtained by selecting
each of the parameters to satisfy the following expression of
relation:
3r<c/(f.multidot..epsilon..sup.1/2)<9r
[0063] In the embodiment of the present invention described above,
a shape of the vacuum chamber, a shape and an arrangement of the
antenna, a shape and an arrangement of the dielectric body, and the
like are shown merely by way of example among variations within the
scope of the present invention. The other variations than the
example can naturally be conceivable in adopting the present
invention.
[0064] The high frequency voltage is supplied to the metallic plate
9 through the through hole 11 formed to the vicinity of the center
of the dielectric plate 10 according to the first embodiment of the
present invention. However, an arrangement as in a second
embodiment of the present invention shown in FIG. 3 is applicable,
in which the high frequency voltage is supplied to the metallic
plate 9 via the through hole 11 set to the vicinity of the center
of the dielectric plate 10, and moreover, the metallic plate 9 and
a wall face 12 of the vacuum chamber opposite to the substrate 7
are shortcircuited by shortcircuit pins 13 via through holes 11A
formed to a plurality of points other than the center and the
periphery of the dielectric plate 10. In this arrangement, an
anisotropic mode among the fundamental mode of the electromagnetic
field radiated from the antenna 5 can be effectively restricted.
Preferably, each of points to be shortcircuited to the vacuum
chamber 1 is nearly isotropically arranged to the center of the
antenna 5 so as to obtain a better effect, for example, uniform
distribution of the plasma. When a substrate with a different
pattern is used or when the plasma density is changed, the points
may not be isotropically arranged thereto.
[0065] Although a surface of the antenna 5 is exposed to the plasma
in the structure of the above first embodiment, the surface of the
antenna 5 may be coated with an insulating cover 14 made of quartz
glass, ceramic, or the like as in a third embodiment of the present
invention shown in FIG. 4. The substrate 7 would be probably
contaminated by a material constituting the antenna 5, or the like
trouble would be brought about without the insulating cover 14.
Therefore, the insulating cover 14 is preferably set if processing
sensitive to contamination is to be carried out. On the other hand,
a ratio of capacitive coupling between the metallic plate 9 and
plasma tends to increase in the absence of the insulating cover 14
thereby increasing the plasma density at a central part of the
substrate 7. Therefore, depending on a type and a pressure of the
gas to be used, a uniform plasma distribution may rather be
obtained by eliminating the insulating cover 14.
[0066] While each of the foregoing embodiments relate to the case
where a space surrounded by a solid surface is not present in the
vicinity of the antenna 5, a ring and groove-shaped plasma trap 15
may be set between the antenna 5 and the vacuum chamber 1 as
according to a fourth embodiment of the present invention
represented in FIG. 5. In this constitution, the plasma trap 15
surrounded by the solid surface enhances electromagnetic waves
radiated from the antenna 5 and facilitates generation of
high-density plasma (hollow cathode discharge) because the hollow
cathode discharge is apt to take place with the low electron
temperature plasma. The plasma density is rendered highest at the
plasma trap 15 in the vacuum chamber 1. The plasma is transported
to the vicinity of the substrate 7 through diffusion. More uniform
plasma can be obtained accordingly.
[0067] While a direct current magnetic field is not present in the
vacuum chamber in each of the above embodiments of the present
invention, the present invention is effective also in the case
where such a large direct current magnetic field as enables the
high frequency power to invade into the plasma is not present, for
instance, when a small direct current magnetic field of
approximately several tens Gauss is used to improve inflammability.
However, the present invention is particularly effective in the
case where the direct current magnetic field is not present in the
vacuum chamber.
[0068] The high frequency power of 100 MHz is supplied to the
antenna in each of the above embodiments. However, the frequency is
not limited to this and the present invention is effective to the
plasma processing method and apparatus using the frequency of 50
MHz-3 GHz.
[0069] Although the antenna is a flat plate in each of the
above-discussed embodiments, the antenna 5 can be formed in a dome
projecting opposite to the substrate 7 as in a fifth embodiment of
the present invention of FIG. 6, the antenna having a recessed
dome-shaped metallic plate 9A, a recessed dome-shaped dielectric
plate 10A, and a recessed dome-shaped insulating cover 14A.
Further, the antenna 5 can be a dome projecting to the substrate 7
as in a sixth embodiment of the present invention shown in FIG. 7,
the antenna having a projected dome-shaped metallic plate 9B, a
projected dome-shaped dielectric plate 10B, and a projected
dome-shaped insulating cover 14B.
[0070] FIG. 8 is a diagram showing measured results of an ion
saturation current density immediately above a substrate with the
relative permittivity of the dielectric plate changed from 14 to 28
under the similar condition of FIG. 2 except for the pressure. That
is, when the relative permittivity of the dielectric plate 10 is
changed from 14 to 28 while a plasma generation condition is fixed
to that a gas is Cl.sub.2, a flow rate of the gas is 100 sccm, a
pressure is 0.3 Pa, and a high frequency power for antenna is 1 kW,
the ion saturation current density measured immediately above the
substrate 7 is indicated in FIG. 8. It is clear from FIG. 8 that
the ion saturation current density decreases when the relative
permittivity of the dielectric plate 10 is approximately 14 or
smaller. When the relative permittivity of the dielectric plate 10
is approximately 28 or larger, plasma is turned instable and the
ion saturation current density cannot be measured. The above result
indicates that since the frequency f of the high frequency power
for antenna is 100 MHz=100,000,000 Hz and the radius r of the
dielectric plate 10 is 115 mm=0.115 m, stable plasma of a high
plasma density can be obtained by selecting each of the parameters
to satisfy the following expression of relation:
5r<c/(f.multidot..epsilon..sup.1/2)<7r
[0071] On the other hand, FIG. 9 is a diagram showing measured
results of an ion saturation current density immediately above a
substrate with the relative permittivity of the dielectric plate
changed from 11 to 45 under the similar condition of FIG. 2 except
for the pressure. When the relative permittivity of the dielectric
plate 10 is changed from 11 to 45 while a plasma generation
condition is fixed to that a gas is Cl.sub.2, a flow rate of the
gas is 100 sccm, a pressure is 0.8 Pa, and a high frequency power
for antenna is 1 kW, the ion saturation current density measured
immediately above the substrate 7 is indicated in FIG. 9. It is
clear from FIG. 9 that the ion saturation current density decreases
when the relative permittivity of the dielectric plate 10 is
approximately 11 or smaller. When the relative permittivity of the
dielectric plate 10 is approximately 45 or larger, plasma is turned
instable and the ion saturation current density cannot be measured.
The above result indicates that since the frequency f of the high
frequency power for antenna is 100 MHz=100,000,000 Hz and the
radius r of the dielectric plate 10 is 115 mm=0.115 m, stable
plasma of a high plasma density can be obtained by selecting each
of the parameters to satisfy the following expression of
relation:
4r<c/(f.multidot..epsilon..sup.1/2)<8r
[0072] As a result of the examples, in order to obtain stable
plasma of a high plasma density, each of the parameters is selected
to satisfy the following expression of relation:
5r<c/(f.multidot..epsilon..sup.1/2)&- lt;7r as a best
example, 4r<c/(f.multidot..epsilon..sup.1/2)<8r as a better
example, and 3r<c/(f.multidot..epsilon..sup.1/2)<9r as a good
example. That is, although depending on the pressure, the kind of
gas, high frequency power for antenna, or the like, the range for
obtaining stable plasma of a high plasma density may be changed,
the ranges of 3r<c/(f.multidot..epsilon..sup.1/2)<9r,
4r<c/(f.multidot..epsilon..sup.1/2)<8r, and
5r<c/(f.multidot..ep- silon..sup.1/2)<7r may be applied to
gas such as Ar, N.sub.2, or the like because it seems that the
range is not greatly changed by the kind of gas.
[0073] In each of the foregoing embodiments, the dielectric plate
is one example of a dielectric member and is not limited to be a
plate, but may be formed of a sheet.
[0074] In each of the foregoing embodiments, the dielectric plate
has a circular shape, but is not limited to be in such a shape. The
dielectric plate may have a rectangular shape or an ellipse shape.
In such a case, r is a half of a diagonal line of a rectangular
shape as shown in FIG. 11B or a half of a major axis of an ellipse
shape as shown in FIG. 11C, instead of a radius (m) of a circular
shape of the dielectric plate as shown in FIG. 11A in this
specification and claims. In the other words, r is a half of a
longer line of a shape of the dielectric plate.
[0075] As is apparent from the foregoing description, according to
the plasma processing method of the present invention, the vacuum
chamber is evacuated while a gas is supplied into the vacuum
chamber, thereby controlling the interior of the vacuum chamber to
a predetermined pressure. In this state, the high frequency power
of a frequency of 50 MHz-3 GHz is supplied to the antenna set
opposite to the substrate placed to the substrate electrode in the
vacuum chamber in the structure in which the dielectric plate is
held between the metallic plate and the wall face of the vacuum
chamber opposite to the substrate, whereby plasma is generated in
the vacuum chamber thereby processing the substrate. Supposed that
the light velocity is c (m/sec), the frequency of the high
frequency power is f (Hz), the relative permittivity of the
dielectric plate is .epsilon., and the radius of the dielectric
plate is r (m), the high frequency power is supplied to satisfy the
relation:
3r<c/(f.multidot..epsilon..sup.1/2)<9r.
[0076] Accordingly, stable plasma of a high plasma density can be
obtained, so that the substrate can be stably processed at high
speed.
[0077] The plasma processing apparatus of the present invention
comprises the vacuum chamber, the gas supply device for supplying a
gas into the vacuum chamber, the evacuation device for evacuating
the interior of the vacuum chamber, the substrate electrode used
for placing the substrate in the vacuum chamber, the antenna in the
structure with the dielectric plate held between the metallic plate
and the wall face of the vacuum chamber opposite to the substrate
electrode, and the high frequency power source which can supply the
high frequency power of the frequency of 50 MHz-3 GHz to the
antenna. Supposed that the light velocity is c (m/sec), the
frequency of the high frequency power is f (Hz), the relative
permittivity of the dielectric plate is .epsilon. and, the radius
of the dielectric plate is r (m), the apparatus is designed to
supply the high frequency power to satisfy the relation:
3r<c/(f.multidot..epsilon..sup.1/2)<9r
[0078] Accordingly, the apparatus can obtain stable plasma of a
high plasma density and stably process the substrate at high
speed.
[0079] 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.
* * * * *