Reduction of capacitive coupling in inductively coupled plasmas by solenoid coils on dielectric window
Solenoid coils with grounded ends positioned on the dielectric window were proposed and numerically studied to reduce the capacitive coupling in conventional inductively coupled plasma (ICP) sources. The capacitive coupling between the plasma and the coils was subsequently suppressed, leading to a significant reduction of the window erosion. To understand the plasma characteristics and the advantages of this configuration, the discharges by the solenoid coil were modeled and compared with a conventional planar coil ICP discharge. The solenoid coil could generate a plasma with higher density than the planar coil under the same absorbed power. The ratio of inductive to capacitive heating power of the solenoid coil was more than one magnitude higher than that of the planar ICP source. The voltage drop on the dielectric window under the solenoid coil was significantly reduced, which was attributed to a potential shielding effect of the grounded end of the radio frequency coil.