The Refractive Index of Homogeneous SiO_(2) Thin Films

摘要

The effect of the through-thickness inhomogeneity of SiO_(2) films on their refractive index is studied. The SiO_(2) films, deposited by tetraethoxysilane pyrolysis on plane-parallel oriented crystalline quartz substrates and on silicon plates, were etched layer-by-layer in Pliskin's solution. The refractive index and the geometric thickness of films were calculated from the measured ellipsometric angles after each etching. The determination errors of the refractive indices as functions of the film thickness, which result from the measurement errors of the polarization angles and substrate parameters, are numerically analyzed. For SiO_(2) films thicker than 20nm, no effect of inhomogeneity is found. The refractive indices of thinner films were observed to depend on the thickness. The reasons for such dependences are discussed.