T03.2 - Soft-Switched Pulsed Bias Plasma Supply System

Radio Frequency (RF) generators are essential as bias voltage sources in plasma-enhanced semiconductor manufacturing processes. Employing pulsed waveforms to generate plasma offers significant improvements in manufacturing precision, but are challenging to produce as they are high voltages (kV range), high frequencies (hundreds of kHz to low MHz), require precise timing, and have broadband frequency content. This work introduces a simple and compact method for generating pulsed bias voltages for plasma processing, enabling reduced loss compared to the complex systems described in the literature. The approach synthesizes the pulsed waveform at a low, convenient voltage and then uses an auto-transformer to step up the voltage to the desired level. A coaxial-cable-based transformer with low leakage inductance is developed to provide scaling with sufficient fidelity across a wide frequency range. Zero voltage switching (ZVS) is achieved on all devices, ensuring low-loss operation. A lab prototype generates pulses of 2.1 kV at 400 kHz. The proposed system further offers adjustable pulse duty ratio and slew rate, providing enhanced control and versatility for various applications.