Ar ion laser assisted chemical etching of via holes in tungsten sheets in air

Abstract

Ar ion laser assisted chemical etching of 150 μm thick annealed tungsten sheets in air is reported. The material removal mechanism involves local heating by the laser to temperatures in the range of 1000-1500 °C that causes rapid oxidation of the W to WO3 which volatilizes readily. Holes with straight walls and slightly enlarged entrances near the surface were drilled with etch rates as high as 11.5 μm/s at 13.8 W, and a minimum hole diameter of 21 μm at 8.1 W. The diameters of the holes and the etch rates were measured and found to increase as a function of the laser power. It was found that by increasing the laser power above 11-12 W, no change was observed in the hole diameters which remained constant at about 31 μm, whereas the etch rates continued to increase even faster than at low powers. Distinct adjacent holes of 25 μm diameter could be drilled with their centers separated by as little as 60 μm. This is therefore also the etching resolution in the present study. © 1986 Springer-Verlag.