A surface modification study of InGaP etched with an electron cyclotron resonance source at variable microwave powers

Abstract

Etch-induced surface modifications, utilizing an electron cyclotron resonance source, have been studied as a function of controllable etch parameters. InGaP was etched with BCl3 at a constant substrate temperature (100 °C) and bias voltage (−145 V) using microwave powers varying between 250 and 1000 W. The surface morphology, residual etch damage, and surface stoichiometry were strongly influenced by changes in ion flux. The etch-induced lattice damage and surface smoothness increased as the ion energy was elevated. Low ion flux etching resulted in an In-enriched P-depleted surface suggesting nonuniform desorption of InClx which gave rise to the surface roughness observed at the low microwave powers. The smooth surfaces, achieved at the higher microwave power levels, were attributed to either efficient sputter-assisted desorption of the InClx etch products or to InClx desorption via plasma-induced surface heating. Results of this study demonstrate that etching at microwave powers between 500 and 750 W induce low residual damage and smooth surfaces while maintaining a reasonable etch rate for device processing.