Opticla dispersion analysis within the IR range of thermally grown and TEOS depostied SiO_2 films

摘要

SiO_2 thin films, with films, with thickness ranging between approximately 13 and 95 nm, have been thermally grown at 950degC in dry oxygen and cheemically vapor deposited at low pressures (0.3 Torr) by decomposition of tetraethylorthosilicate (TEOS) at 710degC, on Si(100) substrates. Dispersion analysis was performed on Fourier transform infrared (FTIR) transmission spectra fo these films within the range 900-1400 cm~-1. It was found that the spectra were best described within this range, by four Lorentz oscillators locate near 1060, 1089, 1165 and 1220cm~-1 almost independent fo film thickness. The polarization of the oscillators (proportional to their strength) was found to increase slightly, and their widths to decrease, with film thickness. From the study of the FTIR spectra obtained at room temperature, it was suggested that at this temperature, a considerable number of Si-O-Si angles in these SiO_2 films are distributed in a way expected at higher temperatures and that the distribution of the Si-O-Si angles depends on the thermal history of the film and the method fo growth.