Three-dimensional statistical simulation of gate leakage fluctuations due to combined interface roughness and random dopants

A three-dimensional simulation methodology allowing statistical study of the direct tunnelling gate current fluctuations in realistic nano-scale metal-oxide-semiconductor field effect transistors (MOSFETs) is presented. The approach has been applied to study the gate leakage fluctuations due to the combined effect of oxide thickness variation.(OTV) and discrete random dopants (RD) in an example 25 nm gate length MOSFET. OTV is the primary source of gate leakage fluctuations at high gate voltage, while RD are the main factor at high drain voltage. Both OTV and RD contribute to an average increase in the magnitude of the gate leakage with respect to that of a uniform device. This reflects the exponential sensitivity of the direct tunnelling current.