On the validity of power transfer efficiency measurement in an inductively coupled plasma.

The validity of the power transfer efficiency measurement using an antenna current in an inductively coupled plasma is investigated. It is valid only if the current ratio between the two capacitors in a L-type matcher remains constant. However, the impedance of the entire circuit, including the matcher, an antenna and a plasma, changes depending on the input power. The current flowing through each capacitor in the matcher is measured by current sensors at various input powers and pressures. Interestingly, in experimental measurement, the current ratio remains constant although the plasma impedance changes. It is found that the resistance of the matcher circuit and the antenna can influence the current ratio between the two capacitors in the matcher. However, the current ratio changes less in the experiments, even though the resistance of the matcher and the antenna is considered. The discussion about the constant current ratio will be presented.