TID Degradation Mechanisms in 16-nm Bulk FinFETs Irradiated to Ultrahigh Doses

This article investigates the total ionizing dose (TID) degradation mechanisms of 16-nm bulk Si FinFETs at ultrahigh doses. n- and p-FinFETs with several channel lengths are irradiated up to 1 Grad(SiO
₂
) and then annealed for 24 h at 100 °C. Irradiated devices show significant degradation in transconductance and OFF-state leakage currents with slight subthreshold stretch-out and negligible threshold voltage shifts. At doses up to 10 Mrad(SiO
₂
), the TID response is dominated by positive trapped charges in the shallow trench isolation (STI). At ultrahigh doses approaching 1 Grad(SiO
₂
), dc static measurements suggest generation of trapped charge at the STI/Si interface and/or at the corner between the STI and the gate dielectric. The TID sensitivity depends on the bias condition and channel length. Halo implantations fortuitously increase the radiation tolerance of short-channel FinFETs due to the increased channel doping caused by the overlap of the source and the drain halos. The worst degradation is found when a high electric field is applied to the gate during irradiation.