Electric heating – Metal heating – By arc
Reexamination Certificate
1998-11-17
2001-01-23
Walberg, Teresa (Department: 3742)
Electric heating
Metal heating
By arc
C156S345420
Reexamination Certificate
active
06177646
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a method and an apparatus for plasma processing, e.g., dry etching, sputtering, plasma CVD, etc. and more particularly to a method and an apparatus for plasma processing of a high frequency induction type.
2. Background Art
Plasma processing in a high vacuum has been required lately to achieve processing with a high aspect ratio in dry etching or embedding with a high aspect ratio in plasma CVD to meet a trend towards minute semiconductor elements.
For instance, if high-density plasma is produced in a high vacuum in dry etching, a probability of ions colliding against neutral gas particles or the like in an ion sheath formed at a substrate surface is decreased, so that the ions are uniform in direction to the substrate. Moreover, an increased degree of electrolytic dissociation increases a ratio of ions reaching the substrate to an entering-particle flux of neutral radicals. Etching anisotropy is eventually enhanced, thereby accomplishing processing with a high aspect ratio.
In plasma CVD, when high-density plasma is produced in a high vacuum, a fine pattern is embedded and smoothed owing to a sputtering effect by ions, thus allowing processing with a high aspect ratio.
Some systems of plasma processing apparatuses that can generate high-density plasma in the high vacuum are proposed.
FIG. 22
is a sectional view of a plasma processing apparatus having a spoke antenna type plasma source. In
FIG. 22
, a vacuum chamber
1
is evacuated by a pump
3
while a predetermined gas is introduced from a gas feed unit
2
to the vacuum chamber
1
, thereby to maintain the interior of the vacuum chamber
1
at a predetermined pressure. In this state, a high frequency power of 500 MHz is supplied from a high frequency power source
4
the for antenna to a spoke antenna
5
on a dielectric body
9
. In consequence, plasma is generated in the vacuum chamber
1
, subjecting a substrate
7
placed on an electrode
6
to plasma processing such as etching, deposition, or surface modification. At this time, as shown in
FIG. 22
, the ion energy reaching the substrate
7
can be controlled by feeding high frequency power to the electrode
6
as well from a high frequency power source
8
for the electrode. This system is described in detail in “New Ultra-High-Frequency Plasma Source for Large-Scale Etching Processes”, Jpn.J.Appln.Phys., Vol.34, Pt.1, No.12B(1995) by S. Samukawa et al.
FIG. 23
is a perspective view of a spiral antenna type plasma processing apparatus proposed earlier by the present inventors. In
FIG. 23
, the vacuum chamber
1
is evacuated by the pump
3
while a predetermined gas is fed from the gas feed unit
2
to the vacuum chamber
1
, so that the vacuum chamber
1
is kept at a predetermined pressure. In the state above, when a high frequency power of 100 MHz is supplied from the high frequency power source
4
to the spiral antenna
5
placed on the dielectric body
9
, plasma is generated in the vacuum chamber
1
, the substrate
7
placed on the electrode
6
can be subjected to plasma processing such as etching, deposition, or surface modification. The high frequency power source
8
is provided to supply high frequency power to the electrode
6
, so that the ion energy reaching the substrate
7
can be controlled.
In the conventional systems shown in
FIGS. 22 and 23
, a large quantity of reaction product is accumulated on the dielectric body
9
, leading to such issues as the generation of dust, shortening of a maintenance cycle, etc. Moreover, there is an issue that an ambience in the vacuum chamber
1
is not stable, rendering plasma processing poorly reproducible. The reason for this will be detailed below.
In the case of plasma CVD, a thin film is also deposited on the dielectric body
9
in a process of forming a thin film on the substrate
7
. Also, when dry etching, a substance resulting from an etching reaction or vapor phase reaction is sometimes turned to a thin film on the dielectric body
9
. The film is increased in thickness through repeated processings. When the film exceeds a certain thickness, the film comes off due to a film stress and falls as dust onto the substrate
7
. Since the dust is given to rise even by processing of only a small count of substrates
7
, inconveniently, the dielectric body
9
is frequently cleaned with pure water, ethanol or the like in the conventional systems of
FIGS. 22 and 23
.
Through repetition of processings, the thickness of the above deposited film is changed, consequently a adsorption rate of radicals is changed, and the ambience in the vacuum chamber
1
, namely, a partial pressure of reaction species is changed, thus worsening reproducibility of plasma processing. A temperature rise of the dielectric body
9
when heated by high energy ions colliding thereto is another cause of the change of the absorption rate of radicals.
A method and an apparatus capable of solving the above-described issues are already realized in an inductive coupling type plasma processing apparatus, which will be specifically described with reference to FIGS.
24
-
25
and
21
.
FIG. 24
is a perspective view and
FIG. 25
is a sectional view of the plasma processing apparatus.
FIG. 21
is a detailed plan view of a flat heater. In
FIGS. 24 and 25
, the vacuum chamber
1
is evacuated by the pump
3
while a predetermined gas is introduced into the vacuum chamber
1
from the gas feed unit
2
, so that the vacuum chamber
1
is kept at a predetermined pressure. During this time, when high frequency power is supplied from the discharge coil-use high frequency power source
4
to a flat spiral discharge coil
21
, plasma is generated in the vacuum chamber
1
and the substrate
7
placed on the electrode
6
is plasma-processed, e.g., etched, or subjected to deposition process or surface modification, etc. In this case, if high frequency power is also sent to the electrode
6
from the electrode-use high frequency power source
8
as indicated in
FIGS. 24 and 25
, the ion energy reaching the substrate
7
can be controlled. A pressure-weld type thermocouple
10
set to the dielectric body
9
and a flat heater
411
are connected to a heater temperature regulator
12
to adjust the dielectric body
9
at a required temperature. An insulating material
13
is disposed between the flat heater
411
and flat spiral discharge coil
21
so as to prevent the discharge coil
21
from being excessively heated. As shown in
FIG. 21
, in order to pass the electromagnetic waves generated by the supply of high frequency power to the coil
21
through a heat generating body
400
of the flat heater
411
, a portion of one face of the dielectric body
9
which is shielded with the heating element of the flat heater
411
to prevent passage of the electromagnetic waves therethrough is not larger than 40% the total area of the one face of the dielectric body
9
. An inner chamber
16
with a belt heater
22
is further installed in the vacuum chamber, and therefore the apparatus is so constructed that not only the dielectric body
9
, but almost every part of the apparatus in touch with the plasma can be heated.
Many substrates, each with a silicon oxide film, are etched with the use of the above apparatus under the conditions that the kind and flow rate of the gas, pressure, high frequency power impressed to the flat spiral discharge coil, and high frequency power impressed to the electrode are respectively C
4
F
8
/H
2
=50/15 sccm, 10 mTorr, 1000W and 300W. When the flat heater
411
is not provided in the apparatus, the dielectric body
9
gradually increases in temperature through repetition of processes. On the other hand, when the flat heater
411
is provided and a set temperature is not lower than 80° C., the dielectric body
9
is changed within the set temperature plus or minus 15° C. even through repeated processings, that is, the dielectric body
9
shows good temperature stability. Without the flat heater
411
, a lot of dust starts to fall on the substrates
7
aft
Haraguchi Hideo
Nakayama Ichiro
Okumura Tomohiro
Watanabe Shozo
Matsushita Electric Industrial Co Ltd.
Van Quang
Walberg Teresa
Wenderoth , Lind & Ponack, L.L.P.
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