Stability of cerium oxide on silicon studied by x-ray photoelectron spectroscopy

The silicon-cerium oxide interface is studied using x-ray photoelectron spe ctroscopy. The oxidation and reduction of species at the interface are exam ined as a function of annealing temperature both in vacuum and oxygen ambie nt, in order to determine their relative stabilities. By depositing a very thin CeO2 film (similar to 30 Angstrom), the cerium and silicon core level peaks can be monitored simultaneously. The presence of characteristic chemi cal shifts of the Si 2p peak gives information about any Sio,, layer that m ay form at the interface. The oxidation state of the cerium can be probed f rom three different areas of the spectrum, From this information we can inf er the oxidation state of both the silicon and the cerium. For the first ti me a complete picture of the interface is obtained. The implications of the se findings on the utility of CeO2 in device applications are discussed. (C ) 2001 American Vacuum Society.