Electrothermal Effects on Hot-Carrier Reliability in SOI MOSFETs—AC Versus Circuit-Speed Random Stress

Abstract

Computational study of electrothermal effects on hot-carrier injection (HCI) in 100-nm silicon-on-insulator (SOI) MOSFET for digital integrated circuit is performed using in-house developed time-domain finite element algorithm. The simulated $I$ – $V$ curve is obtained by solving diffusive carrier transport equations, and it agrees well with our measured results. The time-dependent thermal conduction equation is solved to get the transient temperature response of the device. Furthermore, according to the transient temperature responses to different signal stresses, including step pulse, ac signal, and pseudorandom binary sequence (PRBS), HCI-induced threshold voltage shift (TVS) is captured by accounting for the temperature dependence of HCI. It is shown that the TVS of device under PRBS stress, which is used to mimic the circuit speed operation, is slightly larger than that of the device under ac signal with the same frequency. With the frequency of signal stress decreasing from gigahertz to tens of megahertz, TVS becomes more severe, because the temperature during ON-state is higher for the SOI MOSFET under low-frequency stress. Thick buried oxide leads to high temperature in channel and deteriorates the HCI. The method presented in this paper should also be applicable to the other MOSFET counterparts.