Analytical modeling of threshold voltage and subthreshold swing in Si/Ge heterojunction FinFET

Abstract

This paper presents an analytical model of threshold voltage (Vth) and subthreshold swing (S) for a tri-gate (TG) heterojunction n-FinFET. The heterojunction is formed between the silicon source and germanium channel. The electrical parameters are analyzed by solving three-dimensional (3-D) Poisson’s equation with the aid of superposition principle. Based on the 3-D potential function and the minimum potential position in the channel, Vth and S are modeled. The model is validated against TCAD simulations. The modeled Vth and S are verified for variation of channel length (Lf), workfunction, oxide thickness (tox), drain-to-source voltage (VDS), gate-to-source voltage (VGS), channel concentration and fin width (Tfin). The models developed for Vth and S in the TG heterojunction FinFET are evaluated for its homojunction equivalent silicon structure, and found to exhibit excellent agreement with TCAD results.