Surface charge analysis characterisation of ultraviolet-induced damage in silicon nitride dielectrics

We report the effect of deep ultraviolet (172 nm wavelength, 7.2 eV) irradiation from a Xe2 excimer lamp source on the electrical properties of PECVD Si3N4 dielectric layers on silicon. Surface charge analysis (SCA) was performed on silicon nitride layers of thickness 350 and 1200 A Ê on Si(100) substrates. The signi®cant absorption coef®cient of the silicon nitride at the excimer lamp emission wavelength absorbs 99.5% of the UV radiation in the 1200 AÊ silicon nitride layers. It was found that the ultraviolet induced damaged effects observed for the 350 A Ê silicon nitride layer were extinguished in the 1200 A Ê case, pointing to a substrate-assisted mechanism. The principal damage effect in the silicon nitride dielectric is attributed to a mechanism driven by ultraviolet-induced hot carriers produced in the silicon substrate. # 2000 Elsevier Science B.V. All rights reserved.