Electronic Structure of Photochemically Etched Silicon Surfaces

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Abstract
Photochemical etching of silicon has been carried out in NF3 under ArF excimer laser irradiation. The valence band spectra of a fluorosily layer formed on the etched surface have been systematically investigated for the first time by using in situ X-ray photoelectron spectroscopy. The valence band spectra have indicated that SiF4 and F2 molecular units exist in the surface fluorosilyl layer, and that the top silicon valence band underneath the fluorosilyl layer moves either upward or downward with the progress of etching. It is supposed that these silicon band bendings are caused by the excess photogenerated majority carriers being trapped in the very thin semi-insulating fluorosilyl layer.