Inductively coupled plasma etching of InP using HBr/O-2-based chemistry is reported. With the introduction of oxygen in the HBr plasma, high etching rate, smooth surface morphology, and vertical sidewall profile were achieved due to sidewall passivation and enhancement of ion-assisted chemical etching. The etching behavior was systematically studied by varying different process parameters, i.e., O-2 flow rate, pressure, reactive ion etching power, and inductively coupled plasma power, in a ridge array structure with a ridge width of 1 mu m and a ridge spacing of 1 mu m. InP nanopillars with an aspect ratio of similar to 6.7 were demonstrated using this chemistry. The X-ray photoelectron spectroscopy results suggested that the etched sample surface was P-rich. (c) 2007 The Electrochemical Society.