An Improved Model on Buried-Oxide Damage for Total-Ionizing-Dose Effect on HV SOI LDMOS

The distribution of radiation induced positive oxide trapped charges (N
ot
) in buried oxide (BOX) with different applied electric fields for high-voltage (HV) SOI LDMOS is investigated. In contrast to the traditional model which depends upon N
ot
buildup near the interface that the field line points to, the verified experimental results in this work indicated that there are still a non-negligible set of N
ot
generated in SOI/BOX interface even if the electric field plays a negative role (field line perpendicular to the SOI/BOX interface pointing from the top to the bottom of the BOX). The improved model on BOX damage induced by TID considering this set of N
ot
and its saturation effect is proposed and adopted in accurate simulated analysis to predict the post-irradiation device behavior. The mechanism of HV SOI LDMOS degradation during irradiation is also revealed. The radiation hardening LDMOS in this work keeps breakdown voltage above 120 V at D=500 krad(Si).