Laser-induced etching of tungsten and fused silica in WF6

Etching of tungsten and fused silica induced by a focused argon-ion laser beam at λ=514 nm has been investigated on a composite consisting of a thin W-layer sputtered onto a fused silica substrate. Pure WF6 gas serves as the reactant for both W- and silica-etching. The process starts with pure chemical etching of tungsten. As the thin W-layer is etched through, it continues as a combination of etching of both tungsten and silica. The latter is most probably caused by the formation of fluorine radicals at high temperatures. The analysis of the process is supported by theoretical estimations of temperatures and of the profile evolution of the etched holes.