Applicability of Quasi-3D and 3D MOSFET Simulations in the ‘Atomistic’ Regime

Abstract

The importance of intrinsic fluctuations to the next generation of CMOS circuits has renewed interest in simplified, computationally inexpensive routes to the analysis of circuit parameters such as threshold voltage and subthreshold slope in ensembles of devices. A quasi-3D analytic approach to the statistical analysis of these parameters in 100 × 100 nm, 70 × 70 nm and 35 × 35 nm devices has been compared to the more computationally expensive full 3D simulation. The quasi-3D approach is useful in predicting variations in subthreshold slope, although its predictions become inaccurate for devices of approximately 35 × 35 nm or smaller. It is less effective in considering variations in threshold voltage, erroneously predicting a rise of the ensemble average threshold voltage and significantly exaggerating the threshold voltage variations over the ensemble.