Capacitively coupled glow discharges at frequencies above 13.56 MHz

Particle‐in‐cell/Monte Carlo simulations of glow discharges between parallel plate electrodes indicate that operation at frequencies above 13.56 MHz offers a number of attractive features for plasma processing applications. Plasma density and ion current scale approximately as the square of frequency, but maximum ion energy is unaffected to first order when applied voltage, pressure and electrode spacing remain constant. In addition, raising frequency decreases sheath thickness, thereby increasing ion directionality in the sheath at constant pressure. By manipulating both frequency and rf voltage, it is possible to control ion current and energy independently.