Control of electron and ion density profiles via virtual ground position control in an inductively coupled plasma

Abstract

The effects of capacitive coupling on electron and ion density profiles are studied in an argon inductively coupled plasma. Electron energy probability functions and two-dimensional ion density profiles were measured by changing the termination capacitance from 200 to 1000 pF. Experimental results show that a termination capacitor creates a virtual ground on a coil, and the virtual ground suppresses the local capacitive coupling. At 2 mTorr (non-local electron kinetics), there is little change in the azimuthal electron density distribution for different termination capacitances. However, at 50 mTorr (local electron kinetics), the virtual ground causes each mode (E-mode and H-mode) to have the maximum and minimum points in the azimuthal electron density distribution. As the termination capacitance increases, the virtual ground moves along the coil and the maximum and minimum points of the electron density also move with the virtual ground. These effects are explained by electron dynamics and the power transfer mechanism in each mode (E-mode and H-mode).