Reactive ion beam etching of silicon compounds with a saddle–field ion source

Abstract

Previous work using cold cathode ion sources of the saddle-field type has indicated that they are suitable for the reactive ion beam etching of many materials. Using a B93 source with a nominal beam current density of 0.16 mA cm−5 (neutral beam ion equivalent for argon), targets of Si, SiO2, and Si3N4 have been etched with a beam produced by injecting the source with Ar, CF4, and CHF3. Data are presented which show the etch rate dependence on beam current density for various combinations of etchant and target material. There is evidence to indicate that silicon was etched by free radical species which were produced at low beam energy (0.6 kV anode potential). Test patterns etched in SiO2 and Si3N4 by ’’CF4 and CHF3 beams’’, which have been examined by Scanning Electron Microscopy, reveal no evidence of redeposition, trenching, or lateral etching. Lines and troughs etched in SiO2 with a ’’CHF3 beam’’ to a depth of approximately 1 μm are shown to be vertical and free of undercutting.