New insights into the total dose response of fully-depleted planar and FinFET SOI transistors

Abstract

In this thesis, we examine the total dose response of planar fully depleted planar SOI MOSFETs fabricated in a FinFET technology as functions of both drain bias and gate length. The ID for negative Vgf increases with the drain bias and decreases with the gate length. The mechanisms that are involved include: band-to-band tunneling (BBT), positive charge trapping in the BOX, direct tunneling through the thin gate oxide, and short-channel effects. In order to extend our TID understanding to more advanced FinFETs, devices with narrower fins (40 nm and 80 nm) and shorter gate lengths (100 nm) were critically studied. Both the threshold-voltage shift and the subthreshold swing (SS) were analyzed as functions of device dimensions and total dose. Our experimental results suggest that irradiated FinFET devices with narrower fins are more tolerant to TID effects. This was explained by the additional lateral gate control that attenuates the coupling effects between the front and the back gates, and decreases the fringing field effects originated from the drain terminal.