Oxidation processes on the H 2O-chemisorbed Si(100) surface studied by in-situ infrared spectroscopy

Abstract

The oxidation processes on the Si(100)-(2×1) surface during exposure to H 2O and subsequent thermal annealing were investigated using in-situ infrared absorption spectroscopy in the multiple internal reflection geometry. Exposure to H 2O results in the oxidation of Si–Si bonds (dimer bond and backbonds) even at room temperature. Upon annealing up to 500°C the dimer bond is cleaved to produce dihydride Si (Si–H 2), and the backbonds are attacked by atomic oxygen released from the surface Si–OH species to produce intermediate oxidation species such as SiH 2(SiO). We demonstrate that most of the hydride species are driven out from the surface by annealing up to 500°C, but an intermediate oxidation species (SiH(O 3)) persists up to 600°C. A model of wet oxidation is presented in which dissociation of water molecules, attack of the Si–Si bonds by atomic oxygen and hydrogen and hydrogen desorption are involved in the oxidation.