Device Simulation of Random Dopant Effects in Ultra-small MOSFETs Based on Advanced Physical Models

Abstract

We discuss random dopant effects in ultra-small MOSFETs associated with quantum confinement effects and contact resistances, along with the separation of impurity number fluctuations and position fluctuations. The contribution ratio of the effect of the channel impurity position fluctuation to the total threshold voltage fluctuation almost reaches 75%, which indicates the importance of controlling the impurity diffusion process in the scaled MOSFETs. Fluctuations of electron distribution confined in the inversion layer lead to an increase in threshold voltage deviations as compared to the classical simulation. On the other hand, since the potential fluctuations around the Schottky barriers are not so sensitive to random dopant effects, the standard deviation of threshold voltage with contact resistances becomes lower. As we show, random dopant effects have various physical aspects in terms of device characteristics, and therefore, physical models concerning random dopant effects should be appropriately chosen and taken into consideration for correct device simulation.