[Analysis of reflective IR transmittance spectra at oblique incidence of micrometer SiO2 films on c-Si substrate].

The reflective infrared transmittance spectra at oblique incidence of SiO2 films deposited on c-Si wafer have been measured. The thickness of the films was micrometer quantity. The spectra showed many differences from the common transmittance (or absorption) spectra in the range of 900-1 250 cm(-1). The reflectivity peak at 1100 cm(-1) was found and its position was essentially fixed. With the thickness increased, the drop of peak at 1100 cm(-1) and hollow at 1200 cm(-1) became gradually slow. As the thickness increased to be over 2 micrometers, the shape of the spectra in 1075-1250 cm(-1) did not change obviously. The analysis showed that the measured spectrum was composed of reflectivity spectrum and absorption spectrum of the SiO2 film, which occurred at Air/SiO2 interface and SiQ2 layer respectively. When the thickness was over one micrometer and the film had considerable absorption, the contribution from reflectivity spectrum became very obvious. So the absorption is not the only factor in the analysis of these spectra.