MEMS profilometry by low coherence phase shifting interferometry: Effect of the light spectrum for high precision measurements

A white light interferometer can be used to measure profiles of a few nanometers and is therefore particularly well adapted for micro electro mechanical systems characterization. We present theoretical and experimental results on the profile precision as a function of the light source spectrum. We demonstrate that even if a broadband source is used in the phase shifting mode, the knowledge of the light spectrum allows to calculate a correction factor. This factor determines the local effective wavelength and can be used in order to increase the measurement precision of sample profiles.