Comparison between characteristics of radio-frequency sheaths and pulse sheaths with insulating substrates

Characteristics of collisionless radio-frequency (r.f.) and pulse modulated sheaths near an insulating substrate are studied with a one-dimensional fluid model coupled to an equivalent circuit model. The fluid model includes all the time-dependent terms to ensure that it can describe the sheath dynamics over a wide range of r.f.- or pulse-frequency. In addition, the equivalent circuit model can self-consistently determine the relationship between the instantaneous sheath thickness and instantaneous surface potential at an insulting substrate placed on the r.f. or pulse biased electrode. The characteristic parameters of the two kinds of sheath, such as the time-dependent surface potential and sheath thickness as well as spatiotemporal variations of the potential, ion density and electron density are compared. Furthermore, the ion energy distributions (IEDs) arriving at insulating substrates and the charge density accumulated on insulating substrates are also calculated with the model. It is shown that the pulsed-power operation can more efficiently remedy the ‘surface charging effect’ than the r.f. technique for etching and deposition on insulators. Also, more uniform IED can be obtained by pulse-power techniques than that by r.f. ones.