Annealing ultra thin Ta2O5 films deposited on bare and nitrogen passivatedSi(100)

Ta2O5 films, deposited on bare and nitrogen passivated Si(100) surfaces, we re annealed in the presence of three different oxidizing agents, NO, N2O, a nd O-2, and then examined using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOFSIMS). These films were thin enough to allow spectroscopic examination of the interface between the silicon and the oxide. During deposition of Ta2O5 on bare Si(100), the sub strate is oxidized and the amount of oxide increases during subsequent anne aling, No nitrogen accumulates when annealing in NO or N2O. Angle-resolved XPS and TOFSIMS depth profiles reveal, after annealing, oxidized silicon at the vacuum-solid interface and throughout the oxidized tantalum layer. For Ta2O5 on nitrided Si(100), annealing at 820 degrees C depletes nitrogen in the silicon nitride and increases silicon oxide, regardless of the oxidant used. Temperature programmed reaction spectra of Ta2O5 deposited on previo usly oxidized Si(100) show SiO desorption above similar to 950 degrees C. T he annealing results are accounted for in terms of chemical reactions at th e buried interface that form SiO and, for the nitrided samples, NO species that migrate toward the vacuum interface, Oxidizing species from the gas ph ase also migrate to the buried interface to produce additional silicon oxid e. (C) 1999 Elsevier Science S.A, All rights reserved.