EVIDENCE OF CRYSTALLOGRAPHIC ETCHING IN (100)GAAS USING SICL4 REACTIVE ION ETCHING

Etch rate and etch profile characteristics of (100)GaAs in SiCl//4 reactive ion etching have been studied in the pressure range of 2-110 mTorr. Pronounced crystallographic or orientation dependent etching effects were observed at moderate pressures around 20 mTorr at lower power densities. Etch profiles became vertical at lower pressures. Therefore, pattern profiles with perfectly vertical sidewalls or with sidewalls defined by crystallographic planes can be realized merely by changing the etch conditions. The addition of argon to the etch gas increased the edge sharpness of the vertical profiles and eliminated any trace of orientation dependent etching. Sawtooth gratings and submicrometer structures with high aspect ratios have been fabricated.