Characterization of electron beam damage in oxidized silicon using thermally stimulated exoelectron emission

Abstract

Silicon dioxide thin films grown on p-type Si(111) wafers were exposed to electron beam irradiation ranging from 1 to 4 keV in energy. Subsequent heating of the samples resulted in thermally stimulated exoelectron emission (TSEE) with several peaks in the emission intensity as a function of temperature. Peaks with temperatures below 450 °C occurred at a fixed temperature for a given oxide, but varied as a function of oxide thickness. This emission is thought to be related to electron desorption from shallow trap states or energetic defects in the near surface region of the oxide and some impurity trap states in the bulk. A high temperature peak was observed which varied in time during heating as a function of sample temperature. This suggests a diffusion limited process where physical defects such as vacancies or interstitials must migrate to the surface to produce emission. The energy and thickness dependence of these emission states are related to the creation of defects and excited states in the thin film and the interaction of these states with the Si substrate.