A hybrid system consisting of a multipolar electron cyclotron resonance source driven by a microwave power supply at 2.45 GHz and a radio‐frequency (rf) powered electrode at 13.56 MHz is used for the etching of GaAs and InP. Both CCl2F2and Cl2are used as the gas sources, and the effect of rf and microwave power, pressure, as well as flow rate on etch rate and surface morphology are evaluated. Fast etch rate up to 3.4 μm/min is obtained for GaAs. Etch rate increases with rf power and decreases with microwave power when CCl2F2is used. Optical emission and x‐ray photoelectron measurements indicate that more C‐related compounds are generated when microwave power is on. With Cl2addition, etch rate increases with microwave power and smoother morphology is obtained. Etching for InP yields smooth morphology at a typical rate of 50 nm/min.