Total-Ionizing-Dose Effects on InGaAs FinFETs with Modified Gate-stack

We evaluate the total-ionizing-dose (TID) responses of InGaAs nMOS fin field-effect transistors (FinFETs) with a modified gate-stack irradiated with 10-keV X-rays under different gate biases. This modified InGaAs nMOS FinFET process shows decreased subthreshold leakage current and increased hysteresis in as-processed devices, and reduced hole trapping in irradiated devices, than first-generation development-stage devices. The reduction in subthreshold leakage current is attributed to changing the buffer layer from GaAs to In_0.3Ga_0.7As, thereby enhancing the material quality. Both the increased hysteresis in as-processed devices and reduced hole trapping in irradiated devices are attributed primarily to thinning the Al₂O₃ layer that separates the HfO₂ from the InGaAs layers. This facilitates charge exchange with defects at the HfO₂/Al₂O₃ interface and reduces the percentage of radiation-induced holes that are generated in Al₂O₃ and trapped in HfO₂. The removal of a tungsten layer above the TiN gate reduces the interface dose enhancement.