Understanding and Modeling Opposite Impacts of Self-Heating on Hot-Carrier Degradation in n- and p-Channel Transistors

Abstract

We extend our framework for hot-carrier degradation (HCD) modeling by covering the impact of self-heating (SH) on HCD. This impact is threefold: (i) perturbation of carrier transport, (ii) acceleration of the thermal contribution to the Si-H bond breakage process, and (iii) and shortening vibrational lifetime of the bond resulting in reducing the multiple-carrier mechanism rate. We validate the framework against HCD data acquired on n-channel fin field-effect-transistors (FETs) and p-channel nanowire (NW) FETs under various stress conditions and analyze the importance of each of the aforementioned components of the SH impact on HCD. This analysis shows that in n-channel devices SH depopulates the high energetical fraction of the carrier distribution, while in p-channel transistors SH slightly shifts the carrier energy distribution towards higher energy. Thus, in nFinFETs the impact of SH on the carrier transport and enhancement of the thermal component of bond rupture compensate each other (vibrational lifetime shortening has a weak impact on HCD), thereby leading to slight inhibition of HCD by SH. To the contrary, in pNWFETs these two factors both enhance HCD (while the contribution of the vibrational lifetime dependence on temperature is again small) and thus SH accelerates HCD. Our modeling framework, therefore, can explain why in n-channel FETs SH slightly inhibits HCD, while in p-channel devices HCD is accelerated by SH.