Ellipsometry is a powerful analytical tool for the characterization of thin films in many materials, including semiconductors, dielectric films, metals and polymers. Also known as Spectroscopic Ellipsometry (SE), it is a non-contact, non-destructive optical technique, which measures the polarization change of reflected light after interaction with a sample. This change in polarization is related to material properties.

Ellipsometry is primarily used to measure film thickness, the refractive index (n) and the extinction coefficient (k), but it can also be used to investigate other properties that affect the polarization of light, such as roughness, optical anisotropy (birefringence), crystalline nature, composition, optical bandgap and thermal expansion. Please note that this technique does not measure these parameters directly. In order to extract useful information about thin films, a model is constructed that describes the optical parameters of the sample. Then, the unknown parameters are fitted to obtain a best match between the theoretical response and the experimental data.