Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-05-30
2001-09-11
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230ER, C156S345420
Reexamination Certificate
active
06286454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma process devices, and more specifically, to a plasma process device capable of performing a processing such as deposition, etching and ashing to a large size, rectangular glass substrate using plasma.
2. Description of the Background Art
Conventional plasma process devices to perform deposition, etching and ashing using plasma are known. One of known methods of generating plasma in such a plasma process device is an electron cyclotron resonance plasma excitation method according to which plasma is excited using a microwave and a DC magnetic field. In the electron cyclotron resonance plasma excitation method, however, stable plasma results only if the pressure is set to a level of several mTorr or less at the time of generating plasma. In addition, since the electron temperature in plasma is high, the plasma formed using the electron cyclotron resonance plasma excitation method is not suitable for the process such as deposition as described above. In the electron cyclotron resonance plasma excitation method, a DC magnetic field must be applied, which necessitates the entire device to have a large size. As a result, the manufacturing cost of the plasma process device is disadvantageously high.
Meanwhile, there is a known method of exciting plasma using the surface wave mode of microwave propagating through dielectric rather than using an electron cyclotron resonance method with a DC magnetic field as described above. The plasma excitation method using the surface wave of a microwave can produce stable plasma if the pressure is set in a relatively broad range from several ten mTorr to several Torr or higher, Since the electron temperature in the plasma is relatively low, surface wave excited plasmas are suitable for any of the above processings such as deposition may result.
In a process such as plasma CVD (Chemical Vapor Deposition) and etching, a reaction gas must be introduced uniformly over the entire surface of substrate subject to a reactive process. This is to assure process condition uniformity for deposition, etching or the like over the entire substrate. As one known means for achieving this is the use of a shower plate to supply a reaction gas in a plasma process device. Herein, the shower plate refers to a plate shaped member positioned to oppose a substrate to be processed and having a plurality of reaction gas inlets to introduce a reaction gas into a processing chamber in which the substrate is placed.
As a conventional plasma process device using a method of exciting plasma using the surface wave of a microwave as described above together with a shower plate, a plasma process device using a radial line slot antenna has been known.
FIG. 16
is a schematic cross sectional view of a conventional plasma process device using a radial line slot antenna. Referring to
FIG. 16
, the plasma process device will be described.
Referring to
FIG. 16
, plasma process device
150
includes a vacuum vessel
156
as a processing chamber, a shower plate
153
, a dielectric plate
152
, a radial line slot antenna
151
and an exhaust pump
155
. In vacuum vessel
156
, a circular substrate
154
subjected to deposition process or the like is placed on a substrate holder. Shower plate
153
of dielectric is provided on the upper wall surface of vacuum vessel
156
opposing substrate
154
. Dielectric plate
152
is provided above shower plate
153
with a gap
163
therebetween. Radial line slot antenna
151
is provided on dielectric plate
152
. Shower plate
153
, dielectric plate
152
and radial line slot antenna
151
have a circular shape when viewed from the top. A reaction gas inlet passage
157
is formed to connect the gap
163
between shower plate
153
and dielectric plate
152
. A reaction gas introduced to gap
163
from reaction gas inlet passage
157
is let into vacuum vessel
156
through the gas inlets formed in shower plate
153
.
Substantially homogeneous plasma
158
is formed over the entire surface of substrate
154
from the reaction gas by the microwave introduced into vacuum vessel
156
from radial line slot antenna
151
through dielectric plate
152
, gap
163
and shower plate
153
formed of dielectric. With plasma
158
, a processing such as deposition may be performed on the surface of substrate
154
. The reaction gas which have not contributed to the processing and the gas generated by the reaction at the substrate surface are let out of vacuum vessel
156
through exhaust pump
155
.
FIG. 17
is a perspective cross sectional view of the radial line slot antenna shown in FIG.
16
. Referring to
FIG. 17
, the radial line slot antenna will be described.
Referring to
FIG. 17
, radial line slot antenna
151
includes a coaxial waveguide
160
, a ground plate
159
formed of conductor, a dielectric plate
161
and a slot plate
164
of conductor having slots
162
. Dielectric plate
161
is provided under ground plate
159
. A slot plate
164
is provided under dielectric plate
161
. Coaxial waveguide
160
is connected to dielectric plate
161
. A microwave is transmitted to dielectric plate
161
from coaxial waveguide
160
. Dielectric plate
161
serves as a radial microwave transmission path. A microwave is radiated through slots
162
formed in slot plate
164
from the entire bottom surface of radial line slot antenna
151
.
In the conventional plasma process device using the radial line slot antenna, plasma excitation with a microwave and uniform supply of a reaction gas to the processing chamber using the shower plate are simultaneously performed. The plasma process device using the radial line slot antenna described above suffers from the following problem.
More specifically, referring to
FIG. 16
, in the conventional plasma process device, a microwave used to form plasma
158
is supplied from radial line slot antenna
151
into vacuum vessel
156
as a processing chamber through dielectric plate
152
, gap
163
and shower plate
153
. At this time, gap
163
serving as a transmission path for the microwave also function as a supply passage for a reaction gas to vacuum vessel
156
. As a result, there is the reaction gas to generate plasma in gap
163
. Therefore, the microwave transmitted from radial line slot antenna
151
into vacuum vessel
156
can generate plasma when the gas pressure in gap
163
and the microwave conditions are inappropriate. If plasma is thus generated in gap
163
, shower plate
153
and dielectric plate
152
could be damaged by this plasma. In order to prevent the plasma (abnormal plasma) from being generated in gap
163
, the pressure of the reaction gas in gap
163
was set significantly higher than the pressure of the reaction gas in vacuum vessel
156
. This is for the following reason: electrons in the reaction gas are accelerated by an electric field by the microwave. If however the pressure of the reaction gas in gap
163
is set to a high level of 10 Torr or more, for example, the electrons can collide with other gas atoms or molecules before they are accelerated by the above electric field. As a result, the electrons will no longer have enough energy to generate plasma, so that the plasma can be restrained from being generated in gap
163
.
While the pressure of the reaction gas in gap
163
is set to a high level, the pressure inside vacuum vessel
156
must be maintained at a level of several mTorr. As a result, the pressure of the reaction gas in gap
163
is kept at a high level, while the supply of the reaction gas to vacuum vessel
156
must be sufficiently small. Therefore, the easiness for the reaction gas to flow (conductance) through the reaction gas inlets formed in shower plate
153
must be small. In order to realize such small conductance, fine gas inlets in shower plate
153
must be formed with extremely high precision (a precision in the order of 10 &mgr;m). Meanwhile, shower plate
153
must be formed using dielectric such as ceramic to allow a microwave to propagate. It is extremely dif
Hirayama Masaki
Ohmi Tadahiro
Tadera Takamitsu
Yamamoto Tatsushi
Conlin David G.
Dike Bronstein, Roberts & Cushman IP Group of Edwards & Angell,
Hassanzadeh P.
Mills Gregory
Tadahiro OHMI
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