Chemically assisted ion beam etching of polycrystalline and (100)tungsten

Abstract

A chemically assisted ion beam etching (CAIBE) technique is described which employs an ion beam from an electron bombardment ion source and a directed flux of ClF3 neutrals. This technique enables the etching of tungsten foils and films in excess of 40 μ thick with good anisotropy and pattern definition over areas 30 mm2, and with a high degree of selectivity. (100)tungsten foils etched with this process exhibit preferred orientation etching, while polycrystalline tungsten films exhibit high etch rates. This technique can be used to pattern the dispenser cathode surfaces serving as electron emitters in traveling wave tubes to a controlled porosity.