Oxidation processes on the H2O chemisorbed Si(100) surface studied by in-situ infrared spectroscopy

The oxidation processes on the Si(100)-(2 x 1)surface during exposure to H2O and subsequent thermal annealing were investigated using in-situ infrared absorption spectroscopy in the multiple internal reflection geometry. Exposure to H2O results in the oxidation of Si-Si bonds (dimer bond and backbonds) even at room temperature. Upon annealing up to 500 degrees 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 SiH2(SiO). We demonstrate that most of the hydride species are driven out from the surface by annealing up to 500 degrees C, but an intermediate oxidation species (SiH(O-3)) persists up to 600 degrees 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. (C) 1998 Elsevier Science B.V. All rights reserved.