Characterization of interfacial layer of ultrathin Zr silicate on Si(100) using spectroscopic ellipsometry and HRTEM

Abstract

Optical properties and the film thickness of interfacial layer formed between the ultrathin as-deposited Zr silicate films and the Si substrate were investigated by the variable-angle spectroscopic ellipsometry (SE), the high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). Five Zr silicate films were deposited by using oxygen-based Zr(O-i-Pr)(2)(thd)(2) and Si(O-t-Bu)(2)(thd)(2) as precursors in a pulse-mode metalorganic chemical-vapor deposition (MOCVD) apparatus to investigate the influence of the choice of ambient gas (oxygen or NO) on the formation of the interfacial layers during the oxidation and the deposition of the Zr silicate films. HRTEM images clearly show the existence of the amorphous interfacial layer below the Zr silicate layer. The interfacial layers are found to be Zr-free from the XPS study. In SE analysis, the interfacial layers were described best as the mixture of SiO2 and SiO in the Bruggeman effective medium approximation (BEMA). The evident reduction of the interfacial layer due to the intentionally grown ultrathin oxynitride buffer layer was observed for the Zr silicate film deposited under a carefully designed growing condition. Any source of oxygen during the growth of the film results in the thicker, but self-limited interfacial layer. (C) 2004 Elsevier B.V. All rights reserved.