Comparison of Total-Ionizing-Dose Effects in Bulk and SOI FinFETs at 90 and 295 K

Bulk and silicon-on-insulator (SOI) n-channel FinFETs with fin widths of 15-40 nm and channel lengths of 45 and 1000 nm were irradiated with 1.8 MeV protons at temperatures of 295 and 90 K. Bulk and SOI FinFETs show improved transconductance and steeper subthreshold slopes before irradiation at 90 K than at 295 K. Increased off-state leakage currents are observed for longer channel bulk FinFETs for doses above 300-500 krad (SiO ₂ ) for 295 and 90 K irradiation, and at lower doses for shorter channel devices. Threshold-voltage shifts for irradiation up to 1 Mrad(SiO ₂ ) are greater for SOI devices at 90 K than at 295 K due to enhanced charge trapping in the buried oxide (BOX). TCAD simulations provide insight into radiation-induced trapped-charge densities in the SOI devices.