Numerical Simulation of Random Dopant Fluctuation in Sub-65 nm Metal-Oxide-Semiconductor Field Effect Transistors

Abstract:- As the gate length of MOSFET devices shrinks down below 100 nm, the fluctuation of major devices parameter, namely, threshold voltage (VTH), subthreshold swing, drain current (ID) and subthreshold leakage current due to influences of processes variations becomes a serious problem. Random dopant fluctuation is one of the problems. In this work, we numerically examine the fluctuation effects of random dopant on the threshold voltage and drain current variation in deep sub-micron semiconductor devices. In the numerical simulation of the threshold voltage variation, the drift-diffusion and density gradient models are considered to describe transport phenomena with quantum effects of devices. Random dopant induces drain current and threshold voltage lowering. The fluctuation of device characteristics caused by random dopant cannot be neglected. From the results, the thin channel of DG-MOSFET might prevent VTH fluctuation caused by random dopant effects. Also, comparison of two- and three-dimensional simulation is presented. Three-dimensional simulation must be considered while simulating semiconductor devices in sub-50 nm regime so as to obtain a reliable result. From the fabrication point of view, we concluded that the random dopant fluctuation of device characteristics could be controlled in the design of DG-MOSFET with thin channel thickness. Key-Words:- random dopant fluctuation, double-gate MOSFET, nanoscale device, drift-diffusion model, density-gradient method, three-dimensional simulation