Calibration of Confocal Microscopes in 3D-Metrology

In this thesis, the technological basis for application and production of measurement standards especially suited for confocal microscopes used in surface metrology is presented. Additionally, the influence of various noise sources on the topography height determination from the confocal curve is considered. The sensitivity of a centre-of-mass, a crosscorrelation and a polynomial fit algorithm on these noise sources is analysed by deriving expressions for the height uncertainty in closed form. It is found that the latter algorithm is least effected by random noise. Furthermore, imaging properties of confocal microscopes are investigated by means of numerical simulations and comparative experimental data. Sources of systematic errors are determined by considering light interactions between microscope and specimens with geometrical basic cross-sections, such as inclined mirror and gratings with rectangular cross section. The results reveal that aberrations and also the geometry of the specimen have a great impact on the accuracy of the measurement result. The knowledge gained in the preceding work is used to design measurement standards, which can be used for a faithful calibration of confocal microscopes. Furthermore, a hot embossing process is employed to replicate the standards made from different materials into polymers. Measurement data is provided to prove the applicability of the replication process and the polymer standards.