Charging damage of thin gate oxides is often a concern in plasma processing. This study examines the breakdown voltage characteristics of thin gate oxides in low‐energy argon plasmas. An electron cyclotron resonance (ECR) system with a rf‐biased electrode was used. The effects of rf bias, plasma exposure time, and gate oxide thickness on the gate oxide breakdown voltage were measured. The results show that the ECR plasma process with low, self‐induced dc bias does not induce any charging damage for gate oxides as thin as 120 Å. More device failures are produced with higher bias and longer plasma exposure, while thicker gate oxides show less damage.