In this article, we report on a high etch rate GaAs via hole processes in an electron cyclotron resonance system using a Cl-2/Ar plasma. The effects of process parameters on the GaAs etch rate were investigated. The influences of process parameters on the resultant profiles were also studied. The GaAs etch rate was found to increase as the Cl-2 percentage in the Cl-2/Ar plasma, process pressure, and rf power or the microwave power increased. A maximum etch rate of 6.7 mum/min has been obtained from a sample etched using a microwave power, rf power, and process pressure of 800 W, 150 W, and 50 mTorr, respectively. The degree of anisotropy of the etched profile was controlled by varying the process pressure and rf power.