Closed- and open-boundary models for gate-current calculation in n-MOSFETs

The gate current of different submicron MOS structures has been calculated using two different approaches to evaluate the eigenvalue energy and the escape-time of the quasi-bound states of the potential energy well at the Si/SiO₂ interface. The numerical issues involved in the implementation of these approaches (one semi-classical, the other quantum-mechanical) inside a device simulator are presented. Simulations performed on different thin-oxide MOS structures show that, compared to the quantum-mechanical treatment, the semi-classical approach is faster, numerically less demanding, and surprisingly accurate in estimating the escape-times. Nevertheless, differences in the eigenvalue energy computed assuming open or closed boundary-conditions at the system boundaries sensibly affect the predicted gate current values