Functional design of a pulsed two-frequency capacitively coupled plasma in CF ₄/Ar for SiO ₂ etching

A capacitively coupled plasma (CCP) with a different frequency source at each of two parallel plates is a powerful tool for SiO ₂ etching. A time modulation of two-frequency CCP by a pulsed-power operation will be one of the practical solutions in the next generation of etchers, and will allow charging-free plasma processes for high-aspect-ratio holes or trench etching. We numerically predict the structure and functions of a pulsed two-frequency CCP in CF ₄(5%)/Ar, and discuss its ability to generate charge-free plasma processes. We also investigate the functional separation between plasma production by very high frequency (100 MHz) and bias voltage application by low frequency (1 MHz). Alternate injections of high-energy positive and negative ions are predicted during the off-phase of a pulsed two-frequency CCP.