Infrared ellipsometry investigation of SiO(x)N(y) thin films on silicon

The dielectric function ˜ε (˜ε = ε(1) + iε(2)) of silicon oxynitride films deposited on silicon wafers by dual ion-beam sputtering is determined by infrared ellipsometry between 580 and 5000 cm(-1). The phase-separation model is unable to reproduce the experimental data. The dependence of ˜ε on stoichiometry is analyzed with the microscopic Si-centered tetrahedron model. The random-bonding model with five SiO(4-j)N(j) (j = 0-4) tetrahedra gives a good description of the spectra, provided the dielectric function of the mixed tetrahedra is carefully chosen.