Analysis of 3D current flow in undoped FinFETs and approaches for compact modeling

Current flow in FinFETs is strongly influenced by 3D effects. In this paper, based on 3D TCAD results the current path is analyzed from subthreshold to above threshold operation. A new method to extract the pinch-off point in saturation is presented. Furthermore, based on a 3D analytical model for the electrostatic potential at the barrier threshold conditions and subthreshold slopes at different positions within the channel cross section are analyzed. A way is proposed how 1D current equations can be superposed to result in a semi-empirical model for the channel current. One part of the model dominates the subthreshold behavior, whereas the second part represents the current well above threshold at the silicon surface. This simple model helps to interpret the influence of geometry effects on the channel current.