Effects of Plasma Prenitridation and Postdeposition Annealing on the Structural and Dielectric Characteristics of the Ta2 O 5 / Si System

Abstract

Material and dielectric properties of layers grown on bare Si, as well as and plasma nitrided Si substrates, before and after postdeposition annealing in oxygen, were investigated. X-ray photoelectron spectroscopy reveals that and plasma nitridation on Si at 450°C formed a nitrogen-rich and an oxygen-rich layer, respectively. Capacitance-voltage measurements show that layers deposited on the prenitrided Si exhibit a higher relative dielectric constant and contain a lower density of charge trapping sites as compared to the one on bare Si. In contrast, the interface state density near the midgap is for non-nitrided and nitrided samples, but it is for the nitrided sample. Postdeposition annealing at 650 or 800°C leads to an increment of except to a lesser extent for the nitrided sample, and reduces all to Concurrently, crystallization of the layer and depletion of nitrogen in the interlayer formed by plasma nitridation are observed after annealing at 800°C. As for current-voltage characteristics, all as-deposited samples exhibit large leakage currents, regardless of the prenitridation process. Postdeposition annealing will significantly lower the leakage currents, and the annealed deposited on nitrided Si exhibits better character than the others at high electric field. Effects of various prenitridation and postannealing processes on the structural and electrical characteristics of systems are discussed. © 2002 The Electrochemical Society. All rights reserved.