Theory of Ellipsometry

Ellipsometry is based on measuring the changes of the  amplitude and phase of polarized light when reflected on a sample surface under defined angle.

Spectroscopic ellipsometry measures these parameters (Psi and Delta) not only for one specific wavelength but for a complete spectral range. By fitting the simulated spectra of tan(Psi) and cos(Delta) it is possible to measure beside the layer thickness much more complex layer characteristics like refractive index, absorption, roughness, components ratio,..., depending on the physical model used in the fitting algorithm.

The interaction between the light and the sample surface changes the linear polarized light into elliptically polarized light. This change is analysed by the spectrometer after travelling through a defined analyzer.