Plasma characteristics of an Ar/CF₄/N₂discharge in an asymmetric dual frequency reactor: numerical investigation by a PIC/MC model

Abstract

A one-dimensional particle-in-cell/Monte Carlo model is used to investigate Ar/CF4/N2 discharges sustained in an asymmetric capacitively coupled dual frequency reactor, with emphasis on the influence of the reactor parameters, such as the electrode area ratio and power source parameters, on the plasma characteristics. A comparison with the symmetric reactor is discussed. It is observed that the electron density distribution has a maximum at the bulk-sheath interface near the powered electrode (PE). The electron density and temperature and the sheath width are nearly independent of the electrode area ratio in the asymmetric reactor. Because of the formation of the dc bias voltage, the ion energy distribution function at the PE is calculated to be much broader than the one at the grounded electrode and that in the symmetric reactor. The ion energy at the PE reaches higher maximum values when the electrode area ratio increases. The scaling of the sheath voltage ratio with the electrode area ratio is determined as Va/Vb = (Sb/Sa)q, where q is close to 1. The influence of the high frequency and low frequency source parameters on the dc bias voltage and therefore on the sheath potential and ion energy is also presented.