COMBINED DEPTH PROFILE ANALYSIS WITH SNMS, SIMS AND XPS - PREFERENTIAL SPUTTERING AND OXYGEN-TRANSPORT IN BINARY METAL-OXIDE MULTILAYER SYSTEMS

Depth profile measurements of binary metal oxide multilayer systems ha ve been performed by combined SIMS, SNMS and XPS. The combination of d ata about the particle fluxes and thus the bulk stoichiometry by SNMS, the ionic fluxes by SIMS, and the surface composition and the oxidati on state of the metals by XPS provides a detailed insight into the mec hanism of preferential sputtering in these systems. We present results on the systems Al2O3/TiO2 and SiO2/HfO2. The signal behaviour at the interfaces cannot be explained by preferential sputtering alone, but m ust include an oxygen transport mechanism due to chemical driving forc es. By comparison of these systems with four other multilayer systems, we have developed a model of combined preferential sputtering and oxy gen transport which accounts for the experimental results. The investi gated systems can be classified according to their metal/oxygen sputte r yield ratio, the degree of preferential sputtering, and the heat of formation of the oxide.