A central composite design response surface study was used to determine the etching characteristics of GaAs/AlGaAs in high-density inductively coupled BCl3/Cl2-based plasmas as a function of process parameters including inductive power, substrate bias, and pressure. Equietch rates were obtained for GaAs and AlxGa1-xAs in the entire parameter space investigated and ranged from approximately 0.3 to 1.0 μm/min. The etch rate of GaAs/AlGaAs grew with an increase in all three parameters. Variations in inductive power had the maximum effect on the etch rate while the bias affected the etch rate the least. In contrast, bias played a significant role in the etch rate of photoresist indicating different mechanisms for resist etching. An ion energy threshold was observed for resist etching which was found to increase with decreasing inductive power. Anisotropic GaAs/AlGaAs etch profiles were obtained over a wide range of parameters including very low substrate bias. Extremely smooth etched surfaces were observed for most etch conditions. © 1999 American Vacuum Society.