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 HfO
₂
/Al
₂
O
₃
gate-stack. Transistors are irradiated up to 500 krad(SiO
₂
) 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 HfO
₂
, and the increased noise is due primarily to O vacancies in Al
₂
O
₃
. Additional contributions to the noise from defects in the GaAs buffer layer are also likely, primarily at low temperatures.