SIMULATIONS OF RF GLOW-DISCHARGES IN SF6 BY THE RELAXATION CONTINUUM MODEL - PHYSICAL STRUCTURE AND FUNCTION OF THE NARROW-GAP REACTIVE-IONETCHER

A capacitively-coupled reactive ion etcher (RIE) can operate, even und er high pressure conditions, for dry etching. Most of the etching gase s are known to be strongly electronegative. The spatiotemporal structu re of an ideal narrow-gap RIE with parallel plate geometry in an SF6 d ischarge is investigated over the pressure range of 0.05-0.5 Torr at 1 3.56 MHz, using numerical simulations based on the relaxation continuu m model. The rf plasma consists of a majority of positive and negative ions and a minority of more mobile electrons. The functionality of th e narrow-gap RIE under typical operating conditions is due to the appe arance of a double layer in front of the instantaneous anode. The doub le layer serves as the source of beamlike ions and virgin radicals imm ediately in front of the electrode surface. A narrower sheath width is realized compared with that found in electropositive gases. The maint enance of the rf discharge is accomplished by ionization at the double layer, while detached electrons from the negative ions have no signif icant influence on the function or the structure of the SF6 discharge.