Impact of process variability in junctionless FinFETs due to random dopant fluctuation, gate work function variation, and oxide thickness variation

In this paper, process variability such as random dopant fluctuation (RDF), work function variation (WFV), and oxide thickness variation (OTV) in 14 nm node junctionless (JL) FinFETs is investigated using the impedance field method (IFM). Effects of doping concentration, gate metal grain-related parameters, and device parameter scaling on RDF, WFV, and OTV induced variability are studied using the standard deviations of threshold voltage (σ _Vth) and subthreshold slope (σ _Ssub). As a result, we find that a relatively low doping concentration helps alleviate process variability. As average grain size increases, different mechanisms of σ _Vth and σ _Ssub degradation are analyzed for WFV and OTV induced variability. Compared to WFV and OTV, RDF is revealed as the most significant source of variability as devices scale down. It is observed that fin width (W _fin) and oxide thickness (t _ox) scaling leads to the reduction of RDF induced variability, whereas channel length (L) and fin height (H _fin) scaling results in aggravation of RDF, WFV, and OTV induced variability.