Photochemical synthesis of amorphous SiO2 derived from tetramethoxy silane using excimer lamps

Photochemical synthesis of SiO2 films from tetramethoxy silane (TMOS) using Ar2 (9.9 eV), Xe2 (7.2 eV) or KrCl (5.6 eV) excimer lamp was examined. Impurities in TMOS were characterized by the Karl Fischer method and gas chromatography–mass spectroscopy (GC–MS) combination. It was found that impurities in TMOS, for example, oligomers such as dimers, trimers and tetramers as well as water, determined volatility and thickness of the TMOS film on silicon wafer. It was observed in both infrared (IR) absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) that carbon-related peaks disappeared with illumination at photon energy of either 7.2 or 9.9 eV. It was also found in XPS O 1s spectra that Si–O–C bonds were transformed into Si–O–Si bonds with illumination at photon energy of 9.9 eV. XPS Si 2p results implied that the suboxide was not generated in SiO2 with illumination. Thus, it was confirmed that synthesized solid films with illumination at a photon energy of 9.9 eV were identified as SiO2. SEM observation indicated that synthesized SiO2 films had a flat surface without pores.