In this study, silicon oxynitride (SiON) has been etched in a C2F6 inductively coupled plasma. The process parameters examined include a radio frequency source power, bias power, pressure, and C2F6 flow rate. For process optimization, a statistical experimental design was employed to investigate parameter effects under various plasma conditions. The etch rate increased almost linearly with increasing the source or bias power. Main effect analysis revealed that the etch rate is dominated by the source power. The C2F6 flow rate exerted the least impact on both etch rate and profile angle. It was estimated that the C2F6 effect is transparent only as the etchant is supplied sufficiently. Depending on the pressure levels, the etch rate varied in a complicated way. Parameter effects on the profile angle were very small and the profile angle varied between 83° and 87° for all etching experiments. In nearly all experiments, microtrenching was observed. The etch rate and profile angle, optimized at 1000 W source power, 30 W bias power, 6 mTorr pressure, and 60 sccm C2F6 flow rate, are 434 nm/min and 86°, respectively.