Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Patent
1992-07-27
1994-11-15
Pascal, Robert J.
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
31511151, 118723MW, H01J 724
Patent
active
053651472
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a plasma source, and more specifically to an apparatus for generating a plasma and for controlling certain physical conditions of the plasma.
2. Description of Related Art
In recent years, the utility of plasma has expanded continually. In particular, in the field of production facilities for integrated circuits (IC), a stable plasma source is in demand.
In the conventional high frequency plasma apparatus, adjustment of high frequency or microwave power and gas pressure has been done manually with the consequence that it was not possible to follow automatically any fluctuations in the plasma conditions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device for generating a stable plasma.
The present invention is directed to a plasma stabilizer having measuring circuits for measuring electron temperature and electron density of the plasma means of the triple probe; a gas pressure control circuit for controlling the plasma gas pressure with an output signal of the measured electron temperature; an electric power control circuit for controlling a plasma excitation power with a measured output signal of the electron density; and insulated coupling elements which connect the measuring circuit, the gas pressure control circuit, and the power control circuit, thereby automatically generating a stabilized plasma by controlling at least one of the plasma gas pressure and the plasma excitation power.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a system diagram of one embodiment of the present invention;
FIG. 2 is a system diagram of another embodiment thereof;
FIG. 3 is an explanatory diagram for the principle of the triple probe method; and
FIG. 4 is a characteristic diagram of voltage V.sub.d2 versus electron temperature Te.
FIG. 5 is a diagram showing an alternative to element 151 shown in FIG. 1; and
FIG. 6 is another diagram showing another alternative to element 151 shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is to provide a plasma stabilizer which is capable of generating stabilized plasma by first displaying directly on an indicator electron temperature and electron density of the plasma using the triple-probe method, and then, using these outputs, the high frequency or microwave power quantity and the gas pressure are controlled, either independently or simultaneously.
In this case, the electron temperature and the electron density from the measuring circuits must be taken out as voltage-to-ground outputs, since these circuits are floating from the standpoint of direct current. With this control voltage outputs, the high frequency or microwave power and the gas pressure are controlled, thereby stabilizing plasma flame. PG,3
In case no insulated coupling element is used, the voltage-to-ground which corresponds to the measured output signals of the electron temperature and the electron density are taken out of the abovementioned measuring circuit, with which the gas pressure control circuit and the electronic control circuit may be regulated.
Since the output from the plasma characteristic detecting circuit by the triple probe method is floating from the standpoint of direct current, it is necessary for taking the signals outside to insulatingly connect the circuit in the direct current manner. The preferred embodiments of the present invention transmit control signals to an external circuit by use of the insulated coupling elements such as an isolation amplifier, a voltage/frequency conversion circuit, a photo-isolator, and so forth, even if they are insulated from the standpoint of direct current; and a system of taking out voltages-to-ground which correspond to those output voltages by means of electronic circuit. With these systems, an output signal of the electron temperature Te is introduced into a gas pressure control circuit to control the gas pressure, and a high frequency or microwave output power is controlled with an output s
REFERENCES:
patent: 3617804 (1971-11-01), Paine et al.
patent: 4641060 (1987-02-01), Dandl
patent: 5170098 (1992-12-01), Dutton et al.
Obara Kozo
Shinohara Kibatsu
Umezawa Tsuku
Nichimen Kabushiki Kaisha
Nihon Kosyuha Kabushiki Kaisha
Pascal Robert J.
Shingleton Michael B.
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