Bias Dependence of Total Ionizing Dose Effects in SiGe- ${{\rm SiO}_2}/{{\rm HfO}_2} p$ MOS FinFETs

The total ionizing dose (TID) response of double-gate SiGe- SiO₂/HfO₂ pMOS FinFET devices is investigated under different device bias conditions. Negative bias irradiation leads to the worst-case degradation due to increased hole trapping in the HfO₂ layer, in contrast to what is typically observed for devices with SiO₂ or HfO₂ gate dielectrics. This occurs in the devices because radiation-induced holes that are generated in the SiO₂ interfacial layer can transport and become trapped in the HfO₂ under negative bias, leading to a more negative threshold voltage shift than observed at 0 V bias. Similarly, radiation-induced electrons that are generated in the SiO₂ interfacial layer can transport into the HfO₂ and become trapped under positive bias, leading to a more positive threshold voltage shift than observed at 0 V bias.