Power measurements and coupler optimization in inductive discharges

The power absorbed by the plasma is one of the key parameters which defines processes in any plasma source. This power, however, can be very different from the power at the rf power source output or the coupler terminals, which has been used in many publications to characterize the plasma. This article describes how to find the power absorbed by the plasma and the power lost in the coupler and matcher network for inductively coupled plasmas. In addition, several practical coupler configurations to reduce the coupler coil loss and minimize the rf plasma potential are discussed. We propose an effective and simple method to achieve that by the coupler coil splitting and insertion of the resonating capacitor in the middle of the coil. Our experimental data demonstrate this approach having superior coupler efficiency and substantially lower rf plasma potential.