Infrared spectroscopy study of low-dielectric-constant fluorine-incorporated and carbon-incorporated silicon oxide films

Bonding characteristics of low-dielectric-constant (low-k) fluorine-incorporated silicon oxide (SiOF) and carbon-incorporated silicon oxide (SiOC) films prepared by plasma enhanced chemical vapor deposition were investigated by Fourier transform infrared spectroscopy (FTIR). The frequency of Si–O stretching vibration mode in SiOF film shifted to higher wave number (blueshift) with the increase of fluorine incorporation, while that in SiOC film shifted to lower wave number (redshift) as the carbon content increased. In ${\mathrm{N}}_2$ -annealed SiOC film, the Si–O stretching frequency slightly shifted to lower wave number. To elucidate these phenomena, we have developed the “bonding structure model” based on the electronegativity of an atom. The frequency shifts observed in the FTIR spectra of SiOF and SiOC films were well explained by this model.