Analysis of omega-gate nanowire devices from parasitic conduction to ionizing radiation effects

Abstract

The proposal of this work is to present an analysis of omega-shaped-gate silicon nanowire field-effect-transistors operating in the subthreshold region. It is analyzed three channel widths (WNW), 220, 40 and 10 nm. In the widest device is noted a back interface conduction that it was extrapolated through numerical simulations adding the positive fixed charges (Qox) and interface traps (Nit) at the interface between the channel and the buried oxide. While studying the effects of these charges, it is noticed that besides causing a threshold voltage (VT) shift it does not present a significant variation in the subthreshold swing (SS). Since the total ionizing dose can be simulated by adding Nit and Qox in the gate and buried oxides, this study is extended, aiming to analyze the impact of ionizing radiation in the subthreshold region of nanowire devices. The nanowires presents a high immunity in SS due to the supercoupling provided by the small silicon height (hfin), which is confirmed through the analysis of the surface electrostatic potential. The hfin increase results in a worst coupling and, the Nit and Qox degrades the SS while increasing WNW. For WNW = 10 nm even with hfin = 65 nm, no significant influence in SS is observed.