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

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 (ΔI_{d, lin}) and positive threshold voltage shift (ΔV_t) are found under increasing temperature, whereas, at low gate voltage, ΔV_t is temperature independent and ΔI_{d, 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 ΔV_t curves is observed. Under low injection, the drift is dominated by traps located in the drain extension region at the corner of the STI.