Towards Understanding Cryogenic Reliability in FinFETs Under Hot Carrier Stress: New Findings on Ge Migration, and Impacts of Tail States Evolution

In this paper, we present a systematic study of cryogenic reliability in FinFETs under hot carrier stress down to 10K. Our findings reveal that the traditional view of hot carrier degradation (HCD)-induced Vth shift is no longer sufficient to explain device behavior at such low temperatures. For the first time, an additional ΔVth under HCD stress has been identified in PMOS, attributed to Ge migration from SiGe S/D into the Si channel. This migration reduces band tail states, as uncovered through advanced physical characterizations (TEM/EDS/EELS) and ab initio calculations. These results provide strong physical evidence linking Ge migration to Va. shift at cryogenic temperatures, highlighting the need for cryogenic reliability models to incorporate atomic-scale Ge migration effects.