An Analytical Model to Estimate VT Distribution of Partially Correlated Fin Edges in FinFETs Due to Fin-Edge Roughness

摘要

Line edge roughness (LER) is a critical variability source in scaled FinFETs. LER produces line width roughness (LWR) that causes threshold voltage (VT) variability. Various lithography techniques demonstrate characteristic LER-LWR relationship. For translating LER/LWR to the VT distribution, an analytical model for uncorrelated fin edges (correlation coefficient, ρ = 0) has been presented in the literature. However, a range of correlation coefficients (0 ≤ ρ ≤ 0.85) between two fin edges is experimentally observed for various lithography techniques. In this paper, we present an analytical model to predict p dependent VT distribution for partially correlated fin edges in FinFETs. First, an analytical model of mean (μ) and standard deviation (σ) for p dependent minimum, maximum, and average fin width is presented. This is used to construct an equivalent simplified trapezoidal fin distribution. Second, percolation theory-based model is used to compute VT distribution from the fin distribution. The model is validated against well-calibrated TCAD simulations for a wide range of geometrical (channel length LG and nominal fin width Wfin) and LER variability (correlation length Λ and correlation coefficient ρ) parameters to show excellent match. The model is 1000 times faster compared with TCAD simulations.