A capacitively coupled plasma (CCP) with a different frequency source at each of two parallel plates is a powerful tool for SiO2 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 CF4(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.
We investigate the relationship between local wall charging and the feature profile in a SiO 2 trench pattern, by considering the transport of electrons, positive ions, and neutral radicals from the two-dimensional sheath structure in a two frequencycapacitively coupled plasma in CF 4 (5%)/Ar. Emphasis is given on the influence of both charging and neutral radical accumulation inside the SiO 2 trench during plasma etching. Feature profiles of the SiO 2 trench are estimated by the Level Set method under conditions with/without charging and neutral deposition.
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