Ion energy distributions in rf sheaths; review, analysis and simulation

We present a review and analysis of ion energy distributions (IED) arriving at the target of a radio frequency (rf) discharge. We mainly discuss the collisionless regime, which is of great interest to experimentalists and modellers studying high-density discharges in which the sheath is much thinner than in conventional reactive ion etching systems. We assess what. has been done so far and determine what factors influence the shape of the IEDs. We also briefly discuss collisional effects on the IEDs. Having determined the important parameters, we perform some particle-in-cell simulations of a collisionless current-driven rf sheath which show that ion modulations in an rf sheath significantly affect the IEDs when tau(ion)/tau(rf) < 1, where tau(ion) is the ion transit time and tau(rf) is the rf period.