Stoichiometric dry etching of mercury cadmium telluride using a secondary afterglow reactor

Abstract

A secondary afterglow reactor has been used for the dry etching of mercury cadmium telluride. In this reactor, methane is injected into the flowing afterglow of a microwave discharge in a fluorine source gas. The resulting reaction of F+CH4 produces methyl radicals, which etch mercury cadmium telluride at rates of up to 400 Å/min. Examination of etched surfaces by energy dispersive x-ray analysis and electron beam electroreflectance (EBER) reveals no change of stoichiometry over the unetched surface. EBER analysis further indicates no damage to the crystallinity of the surface. The etched surfaces exhibit crystalline anisotropy. Recent advances in mercury cadmium telluride device fabrication have focused on vacuum processes. The development of a nondamaging, stoichiometric dry etch process provides the potential of processing mercury cadmium telluride focal plane arrays in a continuous vacuum environment.