TID Degradation Mechanisms in 16-nm Bulk FinFETs Irradiated to Ultrahigh Doses
Teng Ma, Stefano Bonaldo, S. Mattiazzo, A. Basçhirotto, Christian Enz, A. Paccagnella, Simone Gerardin
Abstract
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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), the TID response is dominated by positive trapped charges in the shallow trench isolation (STI). At ultrahigh doses approaching 1 Grad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), 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.