Total-Ionizing-Dose Effects and Low-Frequency Noise in 16-nm InGaAs FinFETs with HfO₂/Al₂O₃ Dielectrics

Total-ionizing-dose mechanisms are investigated in 16-nm InGaAs FinFETs with an HfO₂/Al₂O₃ gate-stack. Transistors are irradiated up to 500 krad(SiO₂) and annealed at high temperatures. Irradiated devices show negative threshold-voltage V_th shifts, subthreshold stretch-out, and leakage current increases. These result from positive charge trapping in the gate oxide and shallow trench insulators, and increases in the interface and border-trap charge densities. Low-frequency noise measurements at different temperatures indicate a significant increase of noise magnitude in irradiated devices at an activation energy of 0.4 eV. Density functional theory (DFT) calculations strongly suggest that transistor V_th shifts are due primarily to hole trapping at oxygen vacancies in HfO₂, and the increased noise is due primarily to O vacancies in Al₂O₃. Additional contributions to the noise from defects in the GaAs buffer layer are also likely, primarily at low temperatures.