Ellipsometry - Theory

Ellipsometry is an optical surface analysis technique based on measuring the change in polarization state of light after reflection from a flat surface.

The growing use of surface treatments (optics, semiconductor technology, metallurgy) has contributed to the development of optical techniques for surface analysis: interferometry, reflectometry and ellipsometry.

The principle of ellipsometry, which was discovered over a century ago, has been given a new lease of life by the use of microcomputers and electronic motor control, making it possible to automate and optimize measurements, as well as to operate them with ever-increasing complexity.

The strengths of ellipsometry lie in its non-destructive nature, its wide measurement range (thickness measurement from a fraction of a single-atom layer down to a few micrometers), and its in situ control capability, enabling thickness measurement of layers as they grow in real time.

A distinction must be made between single-wavelength ellipsometry, which is the simplest tool, but allows the identification of only two parameters, and spectroscopic ellipsometry, which carries out measurements over an entire spectrum and allows complex structures to be interpreted: multilayer, interface roughness, homogeneity, etc.