Comparison of the effective oxide thickness determined by ellipsometry with the result by medium energy ion scattering spectroscopy and high-resolution transmission electron microscopy

Ellipsometric results may be inaccurate for the measured thickness of ultra thin oxide films on silicon because of the apparent refractive index change s with thickness. We have assessed this problem by comparing results on oxi de thickness measured by ellipsometry with results of measurements by two i ndependent techniques, such as medium energy ion scattering spectroscopy an d high-resolution transmission electron microscopy, which should not be sub ject to error. The results show that appropriate ellipsometric models can p rovide thickness information consistent with two independent techniques, wh ich improves the reliability of ellipsometric analysis in the nm range. (C) 2001 American Vacuum Society.