SEGR Study on Power MOSFETs: Multiple Impacts Assumption

This paper presents experimental data showing heavy ions inducing gate degradation in power MOSFETs. In the experiments, backside and front-side irradiations are performed. During backside irradiation, the heavy ion ranges are tuned in such way to control whether they hit the gate or not. Gate-to-source current Igss (Phi) is measured versus heavy ions (H.I.) fluence Phi. Post-irradiation-gate-stress-test (PGST) allows measurement of gate breakdown voltage VBD(Phi) which is observed to decrease with (H.I.) fluence. Based on these experimental results, a hypothesis of substrate-generated carriers impact overlap of multiple strikes may explain gate degradation until SEGR triggering. This last hypothesis is supported by a statistical model approach of heavy ions multiple impacts.