Plasma generating device
A plasma generating device is an inductively coupled plasma generating device comprising an antenna coil that generates plasma in a vacuum chamber, a high-frequency power source that is connected to a reference potential to be referred for plasma potential and that applies high-frequency voltage to the antenna coil, and a resonance circuit provided between the antenna coil and the high-frequency power source. The resonance circuit comprises a first series reactance element that is connected in series to one end portion of the antenna coil and has at least a capacitance component and a second series reactance element that is connected in series to the other end portion of the antenna coil and has at least a capacitance component. The circuit configuration at one side and the circuit configuration at the other side are electrically symmetrical.
1. A plasma generating device of an inductive coupling type comprising a vacuum chamber, an antenna coil that generates plasma in the vacuum chamber, a high-frequency power source that is to be connected to a reference potential and that applies high-frequency voltage to the antenna coil, and a resonance circuit provided between the antenna coil and the high-frequency power source, wherein
the resonance circuit comprises
a first series reactance element that is connected in series to one end portion of the antenna coil and has at least a capacitance component,
a second series reactance element that is connected in series to the other end portion of the antenna coil and has at least a capacitance component,
a parallel reactance element connected in parallel with the antenna coil,
a first voltage detection unit for detecting voltage at the one end portion of the antenna coil,
a second voltage detection unit for detecting voltage at the other end portion, and
a capacitance control circuit,
wherein
a circuit configuration of the resonance circuit between the one end portion of the antenna coil and the high-frequency power source is electrically same as a circuit configuration of the resonance circuit between the other end portion of the antenna coil and the high-frequency power source,
the first series reactance element, the second series reactance element and the parallel reactance element are variable, and
the capacitance control circuit is configured to adjust the capacitance of the first series reactance element, the capacitance of the second series reactance element and the capacitance of the parallel reactance element based on voltages detection signals output from the first voltage detection unit and the second voltage detection unit.
2. The plasma generating device according to claim 1 , wherein the first series reactance element and the second series reactance element are capacitors.
3. The plasma generating device according to claim 1 , wherein reactance of the first series reactance element and reactance of the second series reactance element are configured such that a maximum voltage value at the one end portion of the antenna coil is substantially same as a maximum voltage value at the other end portion of the antenna coil.
4. The plasma generating device according to claim 1 , wherein
the vacuum chamber is tubular having an inlet and an outlet for material gas on both sides thereof, and
the antenna coil is wound around a peripheral surface of the vacuum chamber such that the one end portion of the antenna coil is disposed on an inlet side while the other end portion of the antenna coil is disposed on an outlet side, and
capacitance of the first series reactance element is larger than capacitance of the second series reactance element.