A high etch rate GaAs via-hole process was studied in an inductively coupled plasma system using Cl2/BCl3 gas system. The effects of process parameters on the GaAs etch rate were investigated. The influences of photoresist SiO2 and Ni masks on the resultant profiles were also studied by scanning electron microscopy. A maximum etch rate of 8.9 μm/min was obtained and the etched profiles were optimized.