When microfabricating semiconductor materials, it is necessary to reduce etching damage and to apply a high‐selectivity mask. A single‐grid ion beam etching system can generate much larger ion currents at low accelerator voltages than a dual grid system. In this experiment, a tenfold ion current as that from a dual grid system is extracted at accelerator voltages below 1000 eV. Here, GaAs samples are etched with an Ar ion beam in order to evaluate the physical etching damage, as measured from theI–Vcurves of a Schottky diode. The normalizednfactor, which indicates the amount of etching damage, is less than 1.2 for an accelerator voltage less than 100 eV. The ion current density can be increased without increasing the etching damage. Additionally, several mask materials for GaAs etching are examined. Ion beam sputtered carbon has the highest selectivity, about 15–20 atVabelow 150 eV, among the materials examined. The selectivities of Ti for a metal mask and Al2O3for a transparent mask are more than 10 atVabelow 100 eV, whereas the selectivity of SiO2is 2.6.