SEGR study on Power MOSFETs: Multiple impacts assumption

The main emphasis of this study is the investigation of the gate degradation or rupture, aiming to determine the nature of the so-called SEGR phenomena. This article presents experimental data showing heavy ions induced gate degradation in power MOSFETs. In the experiments, backside and front-side irradiations are performed. The heavy ions ranges are tuned in such way to control whether they hit the gate or not, during backside irradiation. Gate-to-source current I_gss (phi) is measured versus heavy ions (H.I.) fluence phi. Post-irradiation-gate-stress-test (PGST) allows to measure breakdown voltage V_BD(phi) as being decreasing with (H.I.) fluence. Based on these experimental results, an hypothesis of substrate-generated ldquohot carriersrdquo impact overlap may explain gate degradation until SEGR triggering. This last hypothesis is supported by statistical approach model of heavy ions multiple impact.