We investigated dry etching of GaAs in a planar inductively coupled plasma (ICP) reactor with BCl3 gas chemistry. The process parameters included planar ICP source power, chamber pressure, reactive ion etching (RIE) chuck power, and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure was changed from 5 to 20 mTorr. RIE chuck power was controlled from 0 to 150 W. The gas flow rate was varied from 10 to 40 sccm. We found that a process condition at 20 sccm BCl3, 300 W ICP, 100 W RIE, and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature showed extremely smooth surface (rms roughness <1 nm), vertical sidewall, relatively fast etch rate (>3000 Angstrom/min) and good selectivity to a photoresist (>3: 1). X-ray photoelectron spectroscopy study on the surface of processed GaAs proved a very clean surface of the material after dry etching. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. These results indicate that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors. (C) 2004 The Electrochemical Society.