On discrete random dopant modeling in drift-diffusion simulations: physical meaning of 'atomistic' dopants

We investigate the physics behind the 'atomistic' dopant model widely used in drift-diffusion (DD) simulators for the study of statistical threshold voltage variations in ultra-small MOSFETs. It is found that the conventional dopant model, when extended to the extreme atomistic regime, becomes physically inconsistent with the concepts of electric potential presumed in DD device simulations. The split of the Coulomb potential between the long-range and short-range parts associated with discretized dopants. is critical for the device simulations under the atomistic regime. A new dopant model to overcome such problems for 3-dimensional DD simulations is proposed by employing this idea. (C) 2002 Elsevier Science Ltd. All rights reserved.