Interferometry for Ellipso-Height-Topometry – Part 1: Coherence scanning on the base of spacial coherence
Abstract:A modified Linnik and a Mirau interferometer are introduced which can be used for Ellipso-Height-Topometry. With these, a set of topographies can be measured, where the measured height H(x, y), the ellipsometric angles Φ(x, y), Δ(x, y) and the degree of polarization P(x, y) all refer to the same pixels of the raster. This coherent set of topographies can be used to calculate topographies of further quantities, e. g. the complex refractive index N(x, y) = N(x, y) – k(x, y) i of bulk surfaces or parameters of thin films, even for discontinuous structures. Material maps which indicate the presence of specific materials and show their exact location in the frame can be generated.
In part I, these interferometric configurations are described and results are presented. It is shown that for oblique incidence, which is obligatory for an ellipsometric detection, the envelope of the interferogram or correlogram can be narrowed for improved z-scan (vertical) discrimination, even in the case of the height detection. By a theoretical analysis, we prove that this is an effect of conventional spatial coherence as a function of the width of the source and can be utilized without any source modulation or source shaping even for small spectral bandwidth of the radiation. This is verified for tungsten incandescent lamps, and for LED's. In part II algorithms for ellipsometric measurements, calibration procedures and first complete topography sets are presented.
Document Type: Research Article
Affiliations: Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, D-70569 Stuttgart, Germany
Publication date: 2003-03-01