OPTICAL-EMISSION SPECTROSCOPY OF PLASMA-ETCHING OF GAAS AND INP

This paper describes optical emission spectroscopy between 260 - 800 nm for ClCH3/H-2 rf-plasma reactive ion etching of Al0.3Ga0.7As, GaAs and InP compound semiconductors. The optical emission species identified for GaAs and InP etching are: Ga, GaCl, In, InCl and diatomic P2 (A1PI(g)-X1SIGMA(u)+) and P2+ (C2PI-X2PI) lines. Under the plasma condition used here and allowing for the stoichiometry of the etch species, it is found that the ratio of emission intensity is SIGMA(In/P) almost-equal-to 1.4. Taken together with the disparity between In and P2 vapour pressures, these results suggest that the initial rate of Indium desorption is a factor 1.4 greater than that of phosphorus, suggesting a near-surface P-enriched surface.