Electric heating – Metal heating – By arc
Reexamination Certificate
2000-12-19
2002-04-23
Hoang, Tu Ba (Department: 3742)
Electric heating
Metal heating
By arc
C219S121360, C373S025000
Reexamination Certificate
active
06376796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma processing system, and more particularly, relates to an antenna supplying a large power and useful for generation of high density plasma without causing any loss and a plasma processing system efficiently generating high density plasma using the antenna and performing predetermined processing on the surface of a substrate.
2. Description of the Related Art
Among the systems for performing predetermined processing on the surface of a semiconductor wafer or liquid crystal substrate (hereinafter referred to as a “substrate”) using plasma, plasma enhanced chemical vapor deposition (PCVD) and plasma etching systems are widely known. In these plasma processing systems, it is necessary to generate high density plasma in order to increase the processing rate. In addition, from the viewpoint of preventing impurities, it is required to form high density plasma by a lower pressure.
To generate plasma for the surface processing, from the viewpoint of obtaining high density plasma with a high efficiency, a system using the gaseous discharge generated by high frequency power is used. The inventors of the present patent application have already proposed a plasma processing system of a type supplying a high frequency power of 2.45 GHz to a radial slotted antenna connected to a coaxial high frequency power feed system to generate plasma (Japanese Patent No. 8-2534219) and have confirmed that good plasma processing was possible (as document, see for example N. Sato et al., “Uniform Plasma Produced by a Plane Slotted Antenna With Magnets For Electron Cyclotron Resonance” for the configuration of a plasma processing system using a slotted antenna shown in the above document. This plasma processing system has a vacuum chamber
102
provided with an evacuating mechanism
101
and generating a discharge inside for generation of plasma, an antenna device
104
arranged on the upper section of the vacuum chamber
102
and provided with a slotted antenna
103
, a high frequency wet-feed system
105
for feeding high frequency power to the slotted antenna
103
, a discharge gas introduction mechanism
105
for introducing a discharge gas into the vacuum chamber
102
, and a substrate holder
107
arranged at a lower position inside the vacuum chamber
102
. A substrate
108
is loaded on the substrate holder
107
as an object to be processed. The shape of the slots (or slits) formed in the slotted antenna
103
is explained in detail in the above-mentioned patent specification or document. The slotted antenna
103
is actually provided with a magnetic circuit formed by permanent magnets etc. for generating a magnetic field near the electromagnetic wave emitter
103
a
, but in
FIG. 9
, its illustration is omitted. Further, as a result of the addition of the magnetic circuit, the slotted antenna
103
originally to be produced as the disk-shaped conductor plate is actually produced as a conductor having a predetermined thickness being able to house a magnetic circuit. In
FIG. 9
, however, for convenience of explanation, it is shown as a plate material. The high frequency power feed system
104
supplying the high frequency power is comprised of a high frequency power source
111
, a stub tuner
112
, a coaxial waveguide converter
113
, a coaxial line
114
, and a coaxial vacuum window
115
.
The substrate
108
loaded on the substrate holder
107
is arranged to face the electromagnetic wave emitter
103
a
in the slotted antenna
103
.
In the plasma processing system shown in
FIG. 9
, the vacuum chamber
102
is evacuated by the evacuating mechanism
101
, discharge gas is introduced into the vacuum chamber
102
, and a predetermined high frequency power is supplied to the slotted antenna
103
by the high frequency power feed system
105
. The introduced discharge gas starts to discharge by the high frequency wave emitted from the electromagnetic wave emitter
103
a
of the slotted antenna
103
and generates plasma in the space in front of the substrate
108
in the vacuum chamber
102
. The surface of the substrate
108
is processed by the physical or chemical action of the generated plasma. For example, if gas having an etching action is introduced as the discharge gas, the surface of the substrate
108
is etched.
Note that in the above-mentioned related art, an industrial frequency of 2.45 GHz is used as the frequency of the high frequency power. Further, the flux density of the magnetic field generated near the antenna by the magnetic circuit, corresponding to the high frequency, is set to be larger than about 875 Gauss so that the frequency of the electron cyclotron becomes equal to 2.45 GHz.
In the field of art of general antennas for transmitting an electromagnetic wave of the microwave to the millimeter wave band, conventionally, the folded waveguide proposed In Japanese Unexamined Patent Publication (Kokai) No. 9-199901 is known. This folded waveguide was proposed to solve the problem of the conventional folded waveguide shown in FIG. 14 of Japanese Unexamined Patent Publication (Kokai) No. 9-199901, that is, the need for formation of reflection surfaces of 45 degrees cuts at the top and bottom of the folded ends and the attachment of adjustment screws for canceling out reflection waves at the reflection surfaces and the resultant complexity of the configuration, the requirement for high dimensional precision, the high cost and inability of mass production, the narrow band of the frequency characteristics, and the troublesome adjustment work. Therefore, the folded waveguide proposed in Japanese Unexamined Patent Publication (Kokai) No. 9-199901 is characterized, as defined for example in claim
1
and claim
2
, by setting an “h” satisfying predetermined conditions in the dimensions a×h (shown in
FIG. 1
) of the opening window of the 180 degrees folded portion.
In general the substrates processed by plasma processing systems have become larger in size in recent years. In the process of production of an LSI by processing of a silicon substrate, it is necessary to fabricate a large number of devices from a single substrate, so the size of substrates have become larger. Therefore, the above-mentioned plasma processing systems have been required to be increased in the power of the high frequency wave supplied in order to make the area of the plasma generation region (area of plane parallel to the substrate) larger and to make the plasma density higher for increasing the processing rate.
The antenna device
104
comprised of the above slotted antenna
103
is predicated on the processing of a substrate of a diameter of about 200 mm using plasma of a density of 10
11
cm
−3
or so generated by the supply of a high frequency power of about 1 kW. Therefore, it is not possible to supply a large power high frequency wave outside of this assumption and therefore not possible to generate high density plasma suited to the processing of a large area substrate. The reason why a large power high frequency wave cannot be supplied is that a standing wave is generated due to the mismatch of the impedance at the high frequency wave propagation path formed in the slotted antenna
103
and therefore a locally strong electrical field is generated and causes insulation breakdown. Further, the electrical field induced in the slotted antenna
103
due to the standing wave becomes large and the surface of the slotted antenna
103
is heated by the Joule effect resulting in a loss of power which in turn obstructs the realization of a higher density plasma. In this slotted antenna, it is generally impossible to avoid mismatch of impedance arising due to the discontinuity in the shape of the high frequency wave propagation path.
Further, according to the technology disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-199901 explained above, it is made possible to match the impedance without adjustment in the folded waveguide of a low loss transmission line of an electromagnetic wave of the micro
Iizuka Satoru
Nakagawa Yukito
Numazawa Yoichiro
Ogawa Unryu
Sato Hiroyasu
Hoang Tu Ba
Oliff & Berridg,e PLC
Sato Noriyoshi
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