INTERPRETATION OF SPECTROSCOPIC ELLIPSOMETRY MEASUREMENTS OF ULTRATHIN DIELECTRIC LAYERS ON SILICON - IMPACT OF ACCURACY OF THE SILICON OPTICAL-CONSTANTS

Ultrathin thermally grown silicon dioxide and silicon oxynitride layer s with thicknesses between 3 and 6 nm are characterised by spectroscop ic ellipsometry, The ellipsometric measurements are interpreted using one- and two-layer optical models and different Si dielectric function reference data available in the literature. It is shown that using th e newest more accurate reference data gives not only an improved fit t o the experimental data, but also a different, more realistic physical model for ultrathin oxide and oxynitride layers on silicon.