REACTIVITY OF A FLUORINE PASSIVATED SILICON SURFACE

Fluorine-terminated Si(100) surfaces have been prepared by dosing with XeF2. The reactivity of these surfaces towards reoxidation by water vapor or molecular oxygen has been analyzed in situ using x-ray photoelectron spectroscopy. Whereas the fluorine-terminated surface is quite stable in dry oxygen, significantly stronger reactivity is observed with water vapor. Reaction with water molecules creates Si-OF surface species, presumably via an insertion reaction, and leads to loss of fluorine and to growth of a thin oxide. It is inferred that the hydrogen-terminated, HF-cleaned surface, which exhibits some surface fluorine, is oxidatively attacked in water or air at Si-F defect sites.