On the ballistic ratio in 14nm-Node FinFETs

Ballisticity in 14nm-node FinFETs is investigated by Monte Carlo device simulation. Analytic doping profiles are reverse-engineered to measured transfer characteristics of FinFETs from literature and from this work and good agreement between Monte Carlo simulations and measurements is achieved without any device-parameter calibration. The ballistic ratio, defined as the ratio of the on-current with and without scattering in the channel region, varies between 60 % and 76 % at a metallurgical gate length of about 20 nm, the higher ratio being obtained for devices with gate overlap. This shows that scattering in the channel is still important in current FinFET technology with doping and geometry details having an influence on ballisticity beyond only the gate length. As a particular result, it is found that valley occupancies change in the channel also in the absence of scattering which is attributed to free propagation leading to valley changes.