3D modeling of coherence scanning interferometry on 2D surfaces using FEM

Despite the fact that optical profilers, such as coherence scanning interferometers, are frequently used for fast and contactless topography measurements in various fields of application, measured profiles still suffer from the wave characteristics of light, which leads to systematic deviations that are still not sufficiently investigated. In order to analyze these systematic deviations and their physical relations, we apply a rigorous simulation model considering both the transfer characteristics of the measurement instrument as well as the geometry and material of different measurement objects. Simulation results are compared to measurement results for different polarizations, wavelengths and interferometer types, considering surface structures including edges, slopes and different materials as the main reasons for those deviations. Compared to former publications, a full three-dimensional (3D) modeling of the image formation with regard to two-dimensional (2D) surface structures is provided. The advantages of 3D modeling in contrast to a time efficient 2D approach are discussed. Further, an extract of an atomic force microscope (AFM) measurement result is used as the basis for the FEM simulation in one example in order to achieve most realistic simulation results.