NUMERICAL MODELING OF LOW-PRESSURE RF PLASMAS

A particle-in-cell simulation is used to model the plasma generated in a parallel plate RF reactor at low pressure. Nonperiodic boundary conditions are used, and the electric field and particle motion are obtained by finite difference methods leading to the self-consistent creation of sheaths on the boundaries. Rate equations are not employed; rather, model cross sections are used to describe collisions between particles. Ionization is included and the plasma is maintained by fast electrons generated in the RF sheaths. Most of the power dissipation is due to the acceleration of ions in the time-average sheath fields. At high applied voltage, the power dissipation is well described by the power law P ∝ V5/2. Simple scaling laws for the density and plasma potential are obtained. The effect of ion mass and charge-exchange collisions on the ion energy spectrum collected by the electrodes is examined. © 1990 IEEE