Infrared absorption studies of wet chemical oxides: Thermal evolution of impurities

We have used infrared absorption spectroscopy to study the thermal evolution (under ultrahigh vacuum conditions) of ultra-thin silicon oxide films grown in acid solutions (HCl, HNO3 and H2SO4). We find that hydrocarbon contaminants, either adsorbed on the oxide surface or physically trapped in the bulk, dissociate and become chemically incorporated into the thin oxide as additional silicon oxide, carbide, hydride and hydroxyl species. These species significantly influence the thermal evolution of the oxide films and persist up to the SiO desorption temperature (850-1000 degrees C) so that, once formed, these defects will be necessarily present in the final device structure.