Structural characterization of epitaxial Y2O3 on Si (001) and of the Y2O3/Si interface

The search for high dielectric constant (high-k) oxides to replace silicon dioxide for future CMOS devices is a formidable task. Key issues are definitely good structural and electrical properties as well as high quality interfaces between the high-k and the semiconductor substrate. In this work we study the local structure of ultra thin Y2O3 films and Y2O3/Si interface, by using Y-K edge x-ray absorption spectroscopy (XAS) in grazing incidence geometry. Y2O3 epilayers (2-20 nm thick) were grown on Si(001) by MBE at 450 °C and some of them were in-situ annealed at 500 °C for 30 min. In the as grown epilayer, XAS determined the presence of Y-Si and Y-O correlations at the Y2O3/Si interface. The in-situ annealing produces a rearrangement of the local atomic environment at the interface and only Y-O correlations are detected. The local structural quality of the epilayers improves with thickness and annealing.