Metal-organic decomposed cerium oxide thin film in mixed ambient at different temperatures for MOS capacitor

Abstract

Post-deposition annealing of CeO2 thin films in nitrogen/oxygen/nitrogen ambient from 400 until 1000 °C successfully transformed the films from oxygen poor to oxygen-rich state, in which an excess of oxygen was detected at higher temperatures as the oxygen interstitials. The adsorbed nitrogen attaching to oxygen vacancies in the CeO2 thin films would inhibit further oxidation of the films, and thus controlling the film thickness in addition to expanding the lattice. The increase of temperature has enhanced adsorption and diffusion of nitrogen and oxygen, decreasing the attachment of nitrogen to the oxygen vacancies. The dissociated nitrogen would reside as dangling bonds that caused a difficulty in controlling the oxidation and hence interfacial layer growth was expected. An exaggerated film growth dominated by interfacial layer happened at the highest temperature, surpassing the CeO2 layer thickness. The lowest interface trap density was attained but a degradation in the current-voltage characteristic happened due to the presence of excess oxygen and nitrogen as the scattering center for the incoming electrons during forward bias operation. A better performance was achieved by the film annealed at 800 °C via the demonstration of the lowest leakage current level, surpassing other films. Detailed explanation was discussed in this work.