SEGR characterization of power MOSFETs: A new insight on PIGST associated to a non-destructive charge collection measurement tool

In this work, the gate degradation or rupture under heavy-ion irradiation of two different Power MOSFET types is studied. The objective is to propose a well defined Post-Irradiation-Gate-Stress Test (PIGST) method for the characterization of the SEGR phenomenon. For doing such, an innovating test bench for power MOSFETs is described. It integrates SEB-SEGR characterization with an embedded charge collection measurement system, allowing a real-time measurement of charge deposited in the drain area during heavy-ion irradiation, and a charge to breakdown and time to breakdown setup. The charge collection system has been calibrated using heavy ion and pulsed laser irradiation.. The effects of flux and fluence used during heavy ion testing on the charge collection have respectively been dealt with. The behavior of the gate breakdown voltage versus the cumulated fluence during PIGST is studied. A potential correlation with multiple impacts phenomenon when operated at high fluences is raised. A statistical approach to quantify the gate breakdown voltage dependence on fluence during PIGST is then proposed. Besides, the relevance of a cumulated fluence sent at once during ground-testing is discussed and intermediate PIGST sequence that seems to reinforce the radiation hardness level of the gate oxide is addressed. Finally, experimental results showing extended PIGST levels are provided. The current leakage onset is shown to be much higher than the standard values of +/-20V specified in the manufacturer datasheets.