Characterization of Water as an Impurity in SiO2 Films Deposited on Si by Chemical Vapor Deposition Using Si(OC2H5)4

SiO2 films (thickness : 500 nm) deposited on Si(100) by plasma- and thermal-assisted chemical vapor deposition (CVD) using tetraethylorthosilicate (TEOS) were studied by Fourier transform infrared spectroscopy (FTIR), etch rate, and variable-energy positron annihilation spectroscopy. As the substrate temperature at deposition was raised, the density of the SiO2 films increased and the Si-OH impurity content decreased. On the other hand, Si-OH impurities in the SiO2 films could not be removed even at a substrate temperature of 440°C The Si-OH content in plasma-assisted CVD SiO2 films was much lower than that in thermal-assisted CVD SiO2 films at the same substrate temperature. It was found from FTIR and the positron study that the water tended to exist as Si-OH clusters, whose surroundings had more open space than those of normally bonded O3≡Si-O-Si≡O3.