Surface analysis using ellipsometry

A method and system for estimating the roughness and the contamination of a surface. A preferred embodiment of the present invention makes use of a mathematical model which gives indications of the metal roughness, expressed as the ratio of metal volume to air volume, and the contamination thickness values of a metal substrate (e.g. gold) for a determined contamination (e.g. organic). This model is based on a series of tables which represent the expected values of psi, i.e. the ratio between the amplitudes of the incident beam on the two polarization planes multiplied by the ratio of the amplitudes of the reflected beam on the polarization planes, and DELTA, i.e. the difference between the phases on the two polarization planes of the incident beam and the reflected beam, for a gold substrate having a predetermined roughness and a predetermined type of contamination (organic). Each table is built for a roughness value phi expressed as the ratio of metal volume to air volume and gives the values of psi and DELTA for a range of possible contaminations expressed as thickness of the contaminant film. Each table shows, for a predetermined value of phi, the expected values of psi and DELTA for an organic contaminant film having a thickness of 0, 10 . . . 100 Angstrom.