Positive self-bias in a magnetized CCP discharge

Abstract

Radio frequency (RF) plasmas are commonly used for surface treatments and plasma heating processes. Controlling the heat flux from the plasma to the RF electrode is a crucial issue for optimizing these processes and is, therefore, the subject of considerable research in the low- and high-temperature plasma physics communities. In an asymmetric capacitively coupled plasma discharge, the ions accelerated by the direct current (DC) self-bias are the prime factor of the wall heating process. In this work, investigations have been performed with the aim to act on the DC self-bias in a linear magnetized RF environment. The lateral side and one face of the electrode have been covered by ceramic in order to limit the electron flux toward these surfaces. The variations in DC self-bias voltage as a function of the gas pressure, coupled RF power, and tilt angle between the RF electrode and the axial magnetic field have been studied. A new regime was discovered at low pressures, higher magnetic fields, and grazing angles for which the self-bias is positive. An analytical model was developed, which is in agreement with the experimental results.