Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2003-01-28
2004-09-21
Lee, Wilson (Department: 2821)
Coating apparatus
Gas or vapor deposition
With treating means
C315S111210
Reexamination Certificate
active
06792889
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma processing apparatuses and plasma processing methods. More particularly, the present invention relates to a high-performance plasma processing apparatus that includes current-detecting means for measuring a discharge current flowing in the gap between an electrode pair during plasma discharge, that can confirm the uniform plasma treatment of a workpiece, and that can stabilize the effective electric power consumption in a plasma space, and to a plasma processing method using the apparatus.
2. Description of the Related Art
FIG. 7
shows a typical plasma processing apparatus that has been used for plasma processes, such as CVD (chemical vapor deposition), sputtering, dry etching, and ashing. Referring to
FIG. 7
, the plasma processing apparatus includes a pair of electrodes composed of a plasma excitation electrode
4
for forming a plasma and a susceptor electrode
8
that faces the plasma excitation electrode
4
. A workpiece W is placed on the susceptor electrode
8
. The plasma excitation electrode
4
is connected to a feeding terminal of an RF generator
1
with an RF feeder
3
and a matching circuit
2
A therebetween. The matching circuit
2
A matches the impedance between the RF generator
1
and the plasma excitation electrode
4
. The matching circuit
2
A is accommodated in a conductive chassis
120
. Also, the RF feeder
3
and the plasma excitation electrode
4
are enclosed in a conductive housing
21
.
RF power generated from the RF generator
1
is supplied to the plasma excitation electrode
4
via the matching circuit
2
A and the RF feeder
3
. A shower plate
5
with many openings
7
is provided below the plasma excitation electrode (cathode electrode)
4
. An annular projection
4
a
abuts on the shower plate
5
. A conductive gas inlet pipe
17
is connected to a space
6
provided between the plasma excitation electrode
4
and the shower plate
5
. The gas inlet pipe
17
has an insulating component
17
a
at the middle thereof to electrically insulate the plasma excitation electrode
4
from the gas supply source. Gas introduced from the gas inlet pipe
17
is supplied through the openings
7
of the shower plate
5
into a chamber
60
surrounded by a chamber wall
10
. The upper side of the chamber wall
10
and the circumference of the plasma excitation electrode
4
are hermetically sealed using an insulator
9
.
The susceptor electrode
8
carrying the workpiece W, such as a wafer, is arranged in the chamber
60
. The susceptor electrode
8
has a common discharge potential and is supported by a shaft
13
. The lower portion of the shaft
13
and a chamber bottom
10
A are hermetically connected to each other with conductive bellows
11
. The chamber
60
is evacuated by an exhaust system (not shown).
Since the susceptor electrode
8
is vertically movable with the shaft
13
and the bellows
11
, the distance between the plasma excitation electrode
4
and the susceptor electrode
8
is, therefore, adjustable, while the vacuum is maintained in the chamber
60
. The lower portion of the shaft
13
is grounded as a common terminal, and the common terminal of the RF generator
1
is also grounded. The chamber wall
10
and the shaft
13
have the same DC potential.
The matching circuit
2
A is disposed between the RF generator
1
and the RF feeder
3
. The matching circuit
2
A matches the impedance between the RF generator
1
and the plasma excitation electrode
4
in accordance with changes in the plasma within the chamber
60
. Thus, the matching circuit
2
A generally includes a plurality of passive devices. Specifically, referring to
FIG. 8
, the matching circuit
2
A includes three types of passive devices: a load capacitor
22
(a vacuum variable capacitor), an inductance coil
23
, and a tuning capacitor
24
(an air variable capacitor). In the drawing, one inductance coil
23
is connected between the load capacitor
22
and the tuning capacitor
24
.
For etching and film deposition using the plasma processing apparatus mentioned above, it is important to maintain processing uniformity. To produce such uniformity, a stabilized plasma must be generated. A conventional plasma processing method for generating a stable plasma includes monitoring of the ground line to control the grounded state and, therefore, to improve the processing characteristics by controlling the number of ions in the plasma, which is dependent on the electrical characteristics, i.e., the current in the ground line.
FIG. 9
shows a typical plasma processing method using ground line monitoring.
Referring to
FIG. 9
, a plasma processing apparatus includes an etching apparatus
101
and a process controller
102
. The process controller
102
controls vacuum exhaust and a state of etching gas supply in the etching apparatus
101
, and also controls the RF power for generating a plasma and the like. The etching apparatus
101
includes a processing chamber
103
and a stage
105
. The processing chamber
103
is vacuum-sealed with a dielectric discharge pipe and microwaves are passed therethrough. The stage
105
is arranged in the lower portion of the processing chamber
103
. A semiconductor wafer
104
serving as a sample is placed on and electrically insulated from the stage
105
.
A mirror magnetic field is applied between the processing chamber
103
and the semiconductor wafer
104
by a solenoid coil and a permanent magnet (neither are shown). In this state, the processing chamber
103
is evacuated to produce a high vacuum. Then, process gas is introduced at a predetermined gas pressure. Furthermore, the microwaves, which are generated in a magnetron, are introduced into the processing chamber
103
through a waveguide (not shown) and are applied to the plasma excitation electrode (cathode electrode, not shown). A microwave discharge induced plasma state thereby occurs. The resonance between an electronic cyclotron motion and microwaves in the magnetic field induces the microwave discharge.
In the etching apparatus
101
, the processing chamber
103
is connected to ground via a variable resistor (current control means)
111
and an ammeter (measurement means)
112
. Accordingly, the ammeter
112
outputs a measured value for the ground line in the processing chamber
103
. The output terminal of the ammeter
112
is connected to a computer
113
. The computer
113
controls the resistance of the variable resistor
111
to a predetermined value based on the current value from the ammeter
112
.
In this case, the number of ions in the plasma forms a dependent relationship with the current in the ground line. That is, the ions disappear into the wall of the grounded processing chamber
103
or the surface of parts in the processing chamber
103
, and a current thus flows into the ground line. Consequently, the number of disappearing ions, that is, the number of ions in the plasma, can be controlled by controlling the current flowing into the ground line.
In general, the plasma processing apparatus described above may not start discharging until the RF voltage applied to the gap between the plasma excitation electrode
4
and the susceptor electrode
8
is exceeds a discharge starting voltage. Therefore, the RF voltage between discharge electrodes must be monitored at least when discharge starts in order to adjust the RF voltage to a level exceeding the discharge starting voltage. Heretofore, the RF voltage has been adjusted by detecting reflected waves with a directional coupler (not shown) included in the RF generator
1
and by adjusting the level of reflected waves to zero. However, in some cases, even when the level of reflected waves becomes zero by this detection method, discharge does not start. Also, this conventional monitoring method cannot detect the unevenness of discharge current density on an electrode surface, thus inhibiting the uniform plasma treatment of a workpiece.
Similarly to
FIG. 8
, an RF output is controlled to a predetermined value at the out
Nakano Akira
Ohmi Tadahiro
Alps Electric Co. ,Ltd.
Beyer Weaver & Thomas LLP
Lee Wilson
LandOfFree
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