Investigation on Cryogenic Reliability in FinFETs Under Hot Carrier Stress

Cryogenic CMOS technology is crucial for high-performance and quantum computing, but faces significant reliability challenges from exacerbated hot carrier degradation (HCD) at ultralow temperatures. In addition, cryogenic HCD (cryo-HCD) is further complicated by the coupling of cryogenic-specific phenomena, such as band tail states. In this work, a change temperature measure-stress-measure (MSM) method is established based on FinFET, which can separate the cryo-HCD from the effects of band tail states. It is found that additional V_th shifts under cryo-HCD in pFinFET at 10 K. The physical mechanism is revealed by advanced atomic-scale characterization [transmission electron microscope (TEM)/energy-dispersive X-ray spectroscopy (EDS)/electron energy-loss spectroscopy (EELS)], which identifies directional Ge migration from Si_1-x Ge_x (SiGe) drain regions into the channel as the origin. Combined with ab initio calculations, we establish that this Ge migration suppresses band tail states, directly inducing the anomalous V_th shift. These findings offer fundamental insights into cryogenic degradation mechanisms, underscoring the crucial role of atomic-scale material transport, which is essential for cryogenic reliability.