Kinetic theory of stochastically heated capacitive RF discharges

Abstract

Summary form only given, as follows. In a capacitive discharge nearly all of the applied voltage appears across the oscillating sheaths, leading to stochastic sheath heating as the dominant heating mechanism at low pressures. The result is an electron energy distribution function (EEDF) that approximates a two-temperature Maxwellian, as seen both experimentally and in numerical simulations. We have used the fundamental kinetic equations to obtain the EEDF over the low pressure range p=1-50 mTorr in argon. The major additional assumption is that the low temperature electrons are trapped in a square well potential that prevents them from interacting with the sheath heating fields. The calculated EEDF can he approximated by a two temperature Maxwellian. We use this approximation to determine the sheath density and the sheath thickness, which are parameters in the kinetic calculation. This gives us a fully self-consistent solution for a given pressure and applied voltage. The effect of ohmic heating is determined by comparing the results with and without the inclusion of this effect. The results are compared to those found in experiments and simulations, obtaining reasonable agreement.