In this paper, we proposed our recent works on inductively coupled plasma (ICP) etching of GaAs in Cl-2/Ar and Cl-2/Ar/O-2 chemistry for pattern structure transferring and analyzed their etching mechanism. It is proposed that the etching rate reduction due to introduction of extra Cl-2 and additional O-2 in the plasma chemistry is resulted from their influences on all ICP etching process aspects. Moreover, with results presented here, it shows that by introducing O-2 into plasma chemistry, the etched GaAs surface roughness will be optimized and the etching ratio of photoresist to GaAs will be tuned. (C) 2015 Published by Elsevier B.V.