Properties of stacked dielectric films composed of SiO2/Si3N4/SiO2

Dielectric films composed of silicon oxide-nitride-oxide (ONO) structure ha ve been grown over a polycrystalline silicon phosphorous-doped substrate. T he films with a total thickness of about 30 nm have been obtained by two di fferent deposition techniques of the top-oxide layer i.e. thermal oxidation of the nitride layers and low pressure chemical vapour deposition, while t he bottom oxide and the nitride layer were obtained by thermal oxidation an d low pressure chemical vapour deposition, respectively. The chemical compo sition was measured by XPS Auger parameter technique while the thickness of the deposited layers was determined by the X-ray reflectivity method and c ompared with the measurements performed on transmission electron microscopy cross-section images. The influence of the layer composition and thickness on the electrical properties of the whole film, used as dielectric layer o f a capacitor with doped polycrystalline silicon as electrodes, have been i nvestigated by measuring current as a function of voltage to study the mech anisms which contribute to an increase of the leakage current with increasi ng applied voltage. Furthermore, electrical erasable programmable read-only flash memory devices built using these dielectric layers in the Boating ga te structure have been measured for 'data retention loss' after thermal str ess. The results give a complete picture on the role of the two topmost lay ers of the ONO structure towards the electrical behaviour. (C) 1999 Elsevie r Science B.V. All rights reserved.