The effect of phase difference between powered electrodes on RF plasmas

Abstract

This paper presents the results of measurements carried out on plasmas created in five different RF discharge systems. These systems all have two separately powered RF (13.56 MHz) electrodes, but differ in overall size and in the geometry of both vacuum chambers and RF electrodes or antennae. The two power supplies were synchronized with a phase-shift controller. We investigated the influence of the phase difference between the two RF electrodes on plasma parameters and compared the different system geometries. Single Langmuir probes were used to measure the plasma parameters in a region between the electrodes. Floating potential and ion density were affected by the phase difference and we found a strong influence of the system geometry on the observed phase difference dependence. Both ion density and floating potential curves show asymmetries around maxima and minima. These asymmetries can be explained by a phase dependence of the time evolution of the electrode-wall coupling within an RF-cycle resulting from the asymmetric system geometry. Show more