A Switched-Mode Power Amplifier for Ion Energy Control In Plasma Etching

Plasma etching is an important process in the semiconductor manufacturing process. In order to precisely control the ion energy for better process quality, a tailored pulse-shape voltage waveform is applied to the plasma reactor table. Traditionally, a linear amplifier is used to generate this waveform, which results in poor efficiency. This paper proposes a switched-mode power amplifier as a substitute to the traditional linear amplifier. The electric equivalent circuit of the plasma reactor is introduced and a basic topology for the switched-mode power amplifier is derived. The basic topology is able to generate the required waveform but it has a low efficiency of charging the capacitive load in practice. Therefore, an efficiencyimproved topology is proposed by adopting resonant charging. A prototype is built in order to validate the research. The experiments show that the presented solution yields a significantly reduced input power compared to the normally used linear amplifier in this application.