Comparison of the effective oxide thickness determined by ellipsometry with the result by medium energy ion scattering spectroscopy and high-resolution transmission electron microscopy

To develop the thin film metrology for the next generation technology of semiconductor industry, a set of oxide samples with nominal oxide thickness from 1.5 to 7.5 nm was prepared and their oxide thicknesses were measured by the three independent methods of spectroscopic ellipsometry, MEIS, and HRTEM. By fitting the various ellipsometric models to the corresponding experimental SE data, the thicknesses and refractive indices of ultrathin SiO₂ films were obtained. The effective refractive index of the oxide film increased exponentially as the film thickness decreased from 7.5 to 1.5 nm.