Accurate Ion Energy Control in Plasma Processing by Switched-Mode Power Converter

Abstract

Plasma processing, such as plasma deposition and etching, requires accurate control of the plasma ion energy. It can be realized by biasing the reactor table with a tailored voltage waveform. Switched-mode power converters can be used to generate the tailored waveforms. Since the plasma reactor is capacitive, it forms an LC circuit with the stray inductance in the loop, which could cause severe resonances to the output waveform. In order to accurately control the ion energy, a smooth tailored voltage waveform is required. In this research, a trajectory control method is introduced based on the equivalent electric circuit model of the plasma reactor. The control method is able to deliver a well-defined output waveform by controlling the switching sequence properly, rather than using passive and dissipative resistive damping.