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 Vth 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 Vth 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. [ABSTRACT FROM AUTHOR]