A BCl3/Ne plasma chemistry was used to etch Ga-based (GaAs, AlGaAs, GaSb) and In-based (InGaP, InP, InAs and InGaAsP) compound semiconductors in a planar inductively coupled plasma (ICP) reactor. The addition of the Ne allows the plasma to maintain high ion density conditions over a broader range of operating pressures. All of the materials exhibit a maximum etch rate at BCl3-to-Ne ratios of 0.25-0.5. Under all conditions, the Ga-based materials etched at significantly higher rates than the In-based materials, due to the higher volatilities of their trichloride etch products relative to InCl3. The etched surfaces of both AlGaAs and GaAs have comparable root-mean-square (rms) roughness and similar stoichiometry to the unetched control samples, while the surfaces of In-based materials are degraded by the BCl3/Ne etching. Etch anisotropy of the GaAs and AlGaAs relies on some degree of sidewall passivation by redeposition of etch products and photoresist from the mask. (C) 2003 Elsevier B.V. All rights reserved.