Radiation-induced breakdown in 1.7 nm oxynitrided gate oxides

We present new experimental data about the radiation-induced breakdown in 1.7 nm gate oxides, typical of the 90nm technology node. We irradiated several MOS capacitors with n- and p-type substrates and different areas under a positive and negative staircase bias with Ag ions. A modified testing procedure was introduced based on a low voltage sensing of the gate current during irradiation. We showed that, even in spite of a smaller gate oxide field, irradiation was more damaging for biases in deep depletion than for biases in accumulation. We attributed this to the injection in the oxide of energetic carriers heated in the depletion region. In this regime of operation, we highlighted the differences in the gate current degradation of nMOS and pMOS devices: abrupt changes followed by a smooth growth in the first ones, an increase proportional to the area in the second.