Anomalous electrical gate conduction in self-aligned MOS structures

Abstract

A class of dielectric conduction and breakdown which can be dominant in practical MOS devices is described. This mechanism consists of surface conduction along the edge of the thin oxide which separates the gate metal from the underlying silicon. Every type of self-aligning dielectric removal tried including direct cleaving produces an effectively weaker dielectric than existed before the removal. Nearly ideal dielectrics result when the oxide edge is electrically isolated from the conductors. It is suggested that the oxide band structure is significantly altered at local regions near the oxide edge-metal connection. Schottky type conduction is indicated instead of the Fowler-Nordheim type found in bulk oxides.