Binding state perturbations in the silicon oxide–tungsten system

Abstract

Thin films of silicon dioxide are widely used in present day microelectronic devices. In this study we investigate the model system silicon oxide adsorbed on clean and oxidized polycrystalline tungsten. The adsorbed silicon oxide is formed by means of an SiO molecular beam, and the adsorbate-surface interactions are studied by means of Auger Electron Spectroscopy and Flash Desorption Mass Spectrometry. We find that the binding state of SiO on a W surface can be perturbed by electron beam irradiation and also by oxygen coadsorption. The electron beam desorbs oxygen from the SiO+W system, but Si is not desorbed. After electron bombardment and annealing at 613 K, the single binding state of SiO on W(oxidized) is converted into two states. One state is characteristic of SiO on W(clean), while the other is characteristic of SiO on W(oxidized). In addition, oxygen coadsorption induces changes in the flash desorption spectrum of SiO. An analysis of the desorption spectrum indicates that the coadsorption process leads to attractive interactions between adsorbate and adsorbate. Thus, we conclude that the binding between the silicon oxide and the metal substrate is very sensitive to the film stoichiometry.