SUBSTRATE DISORDER-INDUCED BY A SURFACE CHEMICAL-REACTION - THE FLUORINE SILICON INTERACTION

Si(111) surfaces etched by XeF2 are studied with high-resolution soft X-ray photoelectron spectroscopy. After a sufficient exposure to XeF2, a thick fluorosilyl reaction layer forms on the surface. An inelastic loss feature in the Si2p core-level spectra collected from these surf aces indicates the presence of Si defects that have been created by th e reaction. These defects are located both at the reaction layer/subst rate interface and in the near-surface region of the substrate.-As sug gested by earlier theoretical studies, it is proposed that the defects in the substrate are created by the excess heat liberated from the fo rmation of exothermic Si-F bonds. Reaction-induced defects are an inte gral and essential part of the etching process, as they enable F to bo nd with subsurface Si and form the characteristic fluorosilyl reaction layer.