Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2001-09-05
2004-03-30
Clinger, James (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C118S7230AN
Reexamination Certificate
active
06713968
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus for generating plasma by high-frequency electromagnetic fields to perform a predetermined process.
In manufacture of semiconductor devices and flat panel displays, plasma processing apparatus have been used widely and frequently for performing processes such as formation of oxide films, crystal growth in semiconductor layer, etching and ashing. Of the plasma processing apparatus as above, a high-frequency plasma processing apparatus is available in which high-frequency electromagnetic fields from an antenna are admitted to a process container to generate high-density plasma. This type of high-frequency plasma processing apparatus can generate plasma stably even when the pressure of plasma gas is relatively low and can be applied to widespread uses to advantage.
An etching apparatus using a conventional high-frequency plasma processing apparatus is constructed as shown in FIG.
20
. In
FIG. 20
, the construction is partly illustrated in sectional form.
A dielectric plate
113
is disposed horizontally in an upper opening of a cylindrical process container
111
. They are jointed to each other through the medium of a sealing member
112
to keep airtightness of the interior of the process container
111
. Evacuation ports
114
for vacuum evacuation are formed in the bottom of the process container
111
and a nozzle
116
for gas supply passes through the sidewall of the process container
111
. Housed in the process container is a carriage
122
for carrying a substrate
121
that is an object to be etched. The carriage
122
is connected to a high-frequency power supply
126
for biasing.
A radial antenna
130
is disposed above the dielectric plate
113
. Peripheries of the dielectric plate
113
and radial antenna
130
are covered with a shield member
117
.
The radial antenna
130
includes two mutually parallel conductive plates
131
and
132
forming a radial waveguide
136
and a ring member
133
for connecting outer peripheries of these conductive plates
131
and
132
. A great number of slots
134
are formed in the conductive plate
131
constituting a radiation plane. When the wavelength of an electromagnetic field propagating inside the radial waveguide
136
(hereinafter referred to as a guide wavelength) is &lgr;
g
, pitch P
2
between adjacent slots in the radial direction is set to be equal to the guide wavelength &lgr;
g
. An inlet port
135
for admitting the electromagnetic field to the inside of the radial waveguide
136
is formed in the center of the conductive plate
132
. The inlet port
135
is connected with a high-frequency generator
145
through a waveguide
141
.
The etching apparatus constructed in this manner operates as will be described below.
After the interior of the process container
111
is first evacuated to a predetermined degree of vacuum, a mixture gas of, for example, CF
4
and Ar is supplied from the nozzle
116
under the control of flow rate. Under this condition, a high-frequency electromagnetic field is supplied from the high-frequency generator
145
to the radial antenna
130
by way of the waveguide
141
.
While propagating inside the radial waveguide
136
, the electromagnetic field supplied to the radial antenna
130
is radiated from the many slots
134
formed in the conductive plate
131
. Since the pitch p
2
between adjacent slots in the radial direction is set to &lgr;
g
, the electromagnetic fields are radiated in a direction substantially vertical to the conductive plate
131
(radiation plane). Then, the electromagnetic fields transmit through the dielectric plate
113
so as to be admitted to the inside of the process container
111
.
Electric fields of the electromagnetic fields admitted to the process container
111
ionize the gas prevailing in the process container
111
to generate plasma in a space S
1
above the substrate
121
representing the object to be processed. At that time, the electromagnetic fields admitted to the process container are not totally absorbed directly by the plasma generation but unabsorbed remaining electromagnetic fields repeat reflection inside the process container
111
to form standing waves in a space S
2
between the radial antenna
130
and the plasma generation space S
1
. As is known in the art, electric fields of the standing waves also take part in the plasma generation.
The thus generated ions of plasma are extracted by negative potential at the carriage
122
and utilized for an etching process.
SUMMARY OF THE INVENTION
In the conventional etching apparatus shown in
FIG. 20
, the standing waves formed in the space S
2
affect the plasma generation to a great extent. Since the distribution of the electric fields of the standing waves is difficult to control, plasma cannot be generated uniformly in the conventional etching apparatus. For example, through observation of plasma that is generated inside the process container
111
with the conventional etching apparatus, it is confirmed that portions
161
A and
161
B where plasma is generated at a high density take place near the center of a plasma generation region
160
as shown in
FIG. 10A
to be referred to later.
Consequently, the conventional apparatus faces a problem that the etching process proceeds more rapidly on the substrate
121
representing the processing object in underlying regions corresponding to the high-density plasma portions. The problem of causing spots in the processing amount is not specific to only the etching apparatus shown in
FIG. 20
but is common to conventional plasma apparatus.
The present invention contemplates elimination of the above conventional problems and it is an object of the invention to improve the distribution of plasma generated by high-frequency electromagnetic fields.
To accomplish the above object, according to the invention, in a plasma processing apparatus using a slot antenna having a radiation plane formed with a plurality of slots so as to radiate electromagnetic fields to the inside of a process container through the plurality of slots, the slot antenna radiates the electromagnetic fields in a direction oblique to the normal direction of the radiation plane.
When a dielectric plate is disposed in parallel to the antenna radiation plane, the electromagnetic fields are radiated in a direction oblique to the normal direction of the dielectric plate. A plasma plane opposing the dielectric plate in the process container has a form extending along the dielectric plate and therefore, the electromagnetic fields directly incident upon plasma inside the process container from the slot antenna through the dielectric plate come into the plasma in a direction oblique to the normal direction of the plasma plane.
To explain briefly how an electric field of an electromagnetic field changes in a region ranging from the boundary between the plasma and dielectric plate to a point where the plasma density assumes a cut-off density, the intensity of a component of electric field in a direction parallel to the plasma plane is maintained to a substantially constant level but the intensity of a component of electric field in the normal direction of the plasma plane increases monotonously. Accordingly, by making the electromagnetic fields incident in a direction oblique to the normal direction of the plasma plane, a resultant component of the two components can take place having a higher electric field intensity than that obtained when the electromagnetic fields are made to be incident in the normal direction of the plasma plane. By virtue of this, the plasma generation efficiency attributable to the electric fields of the electromagnetic fields directly coming from the slot antenna can be improved.
Through this, contribution of the electric fields of the electromagnetic fields directly coming into the process container from the slot antenna to the plasma generation can be promoted and as a result, the participation of the electric fields of the standing waves (that is, indirectly incident wave
Ishii Nobuo
Yasaka Yasuyoshi
Alemu Ephrem
Clinger James
Finnegan Henderson Farabow Garrett & Dunner LLP
Tokyo Electron Limited
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