Communications: radio wave antennas – Antennas – Having electric space discharge device
Reexamination Certificate
2000-08-03
2002-02-12
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Having electric space discharge device
C118S7230AN, C118S7230IR
Reexamination Certificate
active
06346915
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing method such as dry etching, sputtering, and plasma CVD, as well as apparatus therefor, to be used for manufacture of semiconductor or other electron devices and micromachines. More particularly, the present invention relates to plasma processing method and apparatus for use of plasma excited with high-frequency power of VHF or UHF band.
Whereas Japanese Unexamined Patent Publication No. 8-83696 describes that use of high-density plasma is important in order to meet the trend toward microstructures of semiconductors and other electron devices, low electron temperature plasma has recently been receiving attention by virtue of its high electron density and low electron temperature.
In the case where a gas having a high negativity, i.e., a gas that tends to generate negative ions, such as Cl
2
and SF
6
, is formed into plasma, when the electron temperature becomes about 3 eV or lower, larger amounts of negative ions are generated than with higher electron temperatures. Taking advantage of this phenomenon makes it possible to prevent etching configuration abnormalities, so-called notch, which may occur when positive charges are accumulated at the bottom of micro-patterns due to excessive incidence of positive ions. This allows etching of extremely micro-patterns to be achieved with high precision.
Also, in the case where a gas containing carbon and fluorine, such as CxFy or CxHyFz (where x, y, z are natural numbers), which is generally used for etching of insulating films such as silicon oxide, is formed into plasma, when the electron temperature becomes about 3 eV or lower, gas dissociation is suppressed more than with higher electron temperatures, where, in particular, generation of F atoms, F radicals and the like is suppressed. Because F atoms, F radicals, and the like are higher in the rate of silicon etching, insulating film etching can be carried out at larger selection ratios to silicon etching the more with lower electron temperatures.
Also, when the electron temperature becomes 3 eV or lower, ion temperature and plasma potential also lower, so that ion damage to the substrate in plasma CVD can be reduced.
It is plasma sources using high-frequency power of VHF or UHF band that are now receiving attention as a technique capable of generating plasma having low electron temperature.
FIG. 9
is a sectional view of a plate antenna type plasma processing apparatus we have already purposed. Referring to
FIG. 9
, while interior of a vacuum chamber
101
is maintained to a specified pressure by introducing a specified gas from a gas supply device
102
into the vacuum chamber
101
and simultaneously performing exhaustion by a pump
103
as an exhausting device, a high-frequency power of 100 MHz is supplied by an antenna use high-frequency power supply
104
to an antenna
105
via a through hole
107
provided in a dielectric plate
106
which is sandwiched between the antenna
105
and the vacuum chamber
101
and which is generally equal in outer dimensions to the antenna
105
. Then, plasma is generated in the vacuum chamber
101
, where plasma processing such as etching, deposition, and surface reforming can be carried out on a substrate
109
placed on a substrate electrode
108
. In this process, as shown in
FIG. 9
, by supplying high-frequency power also to the substrate electrode
108
by a substrate-electrode use high-frequency power supply
110
, ion energy that reaches the substrate
109
can be controlled. In addition, the surface of the antenna
105
is covered with an insulating cover
111
.
Also, a plasma trap
114
formed of a recessed space between the antenna
105
and a conductor ring
113
provided around the antenna
105
is provided. With such a constitution, because electromagnetic waves radiated from the antenna
105
are intensified by the plasma trap
114
, and because hollow cathode discharge is liable to occur in plasma at low electron temperatures, it becomes easier to generate high-density plasma (hollow cathode discharge) with the plasma trap
114
surrounded by solid surfaces. Therefore, within the vacuum chamber
101
, plasma density becomes the highest at the plasma trap
114
, and plasma is transported up to near the substrate
109
by diffusion, by which more uniform plasma can be obtained.
However, there has been an issue that the conventional method shown in
FIG. 9
has difficulty in ignitability (start of discharge) at low pressure. It was found that with chlorine gas supplied into the vacuum chamber
101
, and with a VHF power of 1000 W applied to the antenna
105
, ignition could not be obtained at 0.3 Pa or lower pressures. Also, with the conventional method shown in
FIG. 9
, ion saturation current density in the vicinity of the substrate
109
is so low that with chlorine gas supplied into the vacuum chamber
110
, and with a VHF power of 1000 W applied to the antenna
105
, the result was 1.41 mA/cm
2
for 1 Pa.
SUMMARY OF THE INVENTION
In view of these issues of the prior art, an object of the present invention is to provide plasma processing method and apparatus superior in ignitability and capable of obtaining high ion saturation current density.
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a plasma processing method for generating plasma within a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the method comprising:
supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna, provided within the vacuum chamber opposite to the substrate, via a through hole provided in a dielectric plate which is sandwiched between the antenna and the vacuum chamber and which is generally equal in outer dimensions to the antenna, while interior of the vacuum chamber is controlled to a specified pressure by introducing a gas into the vacuum chamber and, simultaneously therewith, exhausting the interior of the vacuum chamber, thus generating plasma; and
processing the substrate while plasma distribution on the substrate is controlled by a plasma trap made up of a groove-shaped space between the dielectric plate and a dielectric ring provided around the dielectric plate, and a groove-shaped space between the antenna and a conductor ring provided around the antenna.
According to a second aspect of the present invention, there is provided a plasma processing method for generating plasma within a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the method comprising:
supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna, provided within the vacuum chamber opposite to the substrate, via a through hole provided in a dielectric plate which is sandwiched between the antenna and the vacuum chamber and which is larger in outer dimensions than the antenna, while interior of the vacuum chamber is controlled to a specified pressure by introducing a gas into the vacuum chamber and, simultaneously therewith, exhausting the interior of the vacuum chamber, thus generating plasma; and
processing the substrate while plasma distribution on the substrate is controlled by a plasma trap formed of a groove-shaped space between the antenna and a conductor ring provided around the antenna.
According to a third aspect of the present invention, there is provided a plasma processing method for generating plasma within a vacuum chamber and processing a substrate placed on a substrate electrode within the vacuum chamber, the method comprising:
supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to an antenna, provided within the vacuum chamber opposite to the substrate, via a through hole provided in a dielectric plate which is sandwiched between the antenna and the vacuum chamber and which is larger in outer dimensions than the antenna, while interior of the vacuum chamber is controlled to a specified pressure by introducing a gas into the vacuum chamber
Matsui Takuya
Okumura Tomohiro
Le Hoang-anh
Matsushita Electric - Industrial Co., Ltd.
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