IR SPECTROSCOPIC INVESTIGATION OF SIO2 FILM STRUCTURE

The structure of thermally grown thin (0.01-1.2-mu-m) SiO2 films is studied using IR spectroscopy and computer analysis of the spectrum line shape. Deconvolution of the silicon oxygen stretching band into gaussian profiles is carried out with rather high accuracy. It is shown that the number of elementary bands varies from two to six with oxide thickness, band parameters (maximum position and full width at half-maximum) being independent of film thickness. A correlation is found between band maximum positions and calculated frequencies of transverse and longitudinal oxygen vibrational stretching modes for some definite values of the Si-O-Si bond angle. A model of thermally grown SiO2 film structure is developed in which the SiO2 network is considered as a mixture of 4- and 6-fold rings of SiO4 tetrahedra with inclusions of beta-cristobalite and/or chain fragments.