A comparative materials study of magnetron ion etched GaAs using Freon-12, SiCl4 and BCl3

Etch characteristics and residual damage incurred via magnetron ion etching of GaAs using three different etch gases, namely, freon-12, SiCl₄ and BCl₃, at two different power levels has been studied. Transmission electron microscopy, scanning electron microscopy, Auger electron spectroscopy, and Schottky diode measurements were employed to determine the suitability of the processed surfaces for device fabrication. Lattice damage was incurred in all processing situations in the form of small dislocation loops. Samples etched in freon-12 at the highest power density exhibited the roughest surface morphology, while those etched in SiCl₄ and BCl₃ resulted in planar surfaces. The Schottky barrier diode characteristics, for all etch gases, degraded with increasing power density. The electrical quality of the BCl₃-etched GaAs at the lowest power density was superior to that of the other etch gases at all power levels. The etched profiles of SiCl₄ and BCl₃ yielded vertical sidewalls, whereas freon-12 yielded a negative undercut. The BCl₃-etched GaAs surfaces were residue-free, while those of freon-12 and SiCl₄ exhibited surface or sidewall contamination. Our results have demonstrated that magnetron ion etching with BCl₃ yields planar residue-free surfaces with minimum material surface damage and superior electrical integrity compared with GaAs etched with freon-12 or SiCl₄.