Dynamics of Capacitively Coupled Plasma under Bipolar Voltage Pulsing for Charge Neutralization in High Aspect Ratio Etching

As semiconductor fabrication advances, the characteristics of capacitively coupled plasma (CCP) have become increasingly critical. During high aspect ratio (HAR) etching, ions accelerated through the sheath penetrate deeply into trenches. In contrast, electrons, limited by their thermal motion, remain near the trench surface, resulting in localized charge separation. This paper investigates optimal bipolar pulse conditions for extracting highly directional electrons from either the bulk plasma or the sheath. In particular, the effects of pulse parameters on the spatiotemporal evolution of plasma potential and the energy of the extracted electrons are analyzed. The pulse rise time emerged as a critical variable of electron energy: a rise rate of 1 kV ns⁻¹ produced highly directional electrons with translational energies of approximately 400 eV. The results provide quantitative insight into tailoring bipolar waveform strategies to mitigate the charge neutralization issue and enhance etch profile control in advanced semiconductor processes.