HOLE-SIZE DEPENDENT HIGHLY SELECTIVE SIO2 ETCHING WITH A HEXTHODE-TYPE WIDE-GAP PLASMA ETCHER

We carry out contact-hole etching of SiO2 with a high selectivity over the underlying Si using a hexthode-type wide-gap plasma etcher. In sp ite of the low power density in the plasma, heavy fluorocarbon deposit ion was observed. The amount of deposition is thought to depend on the bias voltage near the surface of the wafer. Selectivity is low in sma ller holes (< empty set 0.8 mu m), since the deposition radicals are s haded and cannot reach the bottom of the holes. In larger holes (> emp ty set 0.8 mu m), however, selectivity is very high (>50), and almost infinite in a hole of empty set 2.0 mu m in diameter. Moreover, sidewa ll deposition is enough to prevent retardation of the resist even in s maller holes. As a result, quite unique hole-size dependent etching ch aracteristics were obtained, such as tapered etching for smaller holes and high selectivity etching for larger holes. This oxide etcher is a pplicable when large shallow holes and small deep holes must be etched at the same time. (C) 1997 American Vacuum Society.