Current model considering oxide thickness non-uniformity in a MOS tunnel structure

A problem of oxide non-uniformity in MOS tunnel structures on n-type Si wit h a 2-3 nm nominal SiO2 thickness d(n) is investigated. Thickness distribut ion is described with Gauss law. Concepts of modeling of reverse current-vo ltage characteristics are formulated for metal-oxide-semiconductor (MOS) tu nnel structures, regarding the effect of nonuniformity. The current crowdin g in relatively thin device sections is shown to result in a noticeable tra nsformation of curves for electron and hole tunnel currents. Introduction o f a mean effective thickness d(eff) instead of the nominal one is possible only for the weak-inversion regime. The experimental part of this work incl udes the examination of samples by TEM and atomic force microscope methods, and their electrical characterization. Measured characteristics have been satisfactorily fitted by curves simulated for a standard thickness deviatio n of sigma = 0.3 nm. (C) 2001 Published by Elsevier Science Ltd. Ail rights reserved.