Investigation on the temperature dependence of the HCI effects in the rugged STI-based LDMOS transistor

Abstract

The rugged LDMOS transistors showing a current "enhancement" in their high current-voltage regime are investigated under electrical stress conditions. A new hot-carrier-injection (HCI) effect is observed for the n-channel devices, in that the temperature dependence of the device parameter drift changes with operating conditions: under high injection conditions, an increasing linear current drift DId,lin and a positive threshold voltage shift DVt are found under increasing temperature, whereas at low gate voltage DVt is temperature independent and DId,lin decreases with increasing temperature. A numerical investigation is carried out, revealing that traps at the gate oxide close to the source side of the channel are mainly responsible for the degradation under high injection, where the increase of the normal electric field is mainly driven by the local temperature. A temperature-dependent slope of the DVt curves is observed. Under low injection, the drift is dominated by traps located in the drain extension region at the corner of the STI