High-resolution coherence scanning immersion interferometry for characterization of sub-micrometer surface structures

Abstract Coherence scanning interferometry is an optical, non-contact measurement technique employed for the high-resolution three-dimensional characterization of surface topography. In order to enhance the lateral resolution of an interference microscope, a Linnik interferometer with immersion objectives of high numerical aperture was set up and used to measure technical surfaces. This study demonstrates the impact of an immersion medium to improve the lateral resolution and compares immersion and non-immersion systems in terms of signal formation and transfer characteristics in the three-dimensional spatial frequency domain. The measurement results of transparent mr-NIL210 gratings show a significant improvement in signal quality using immersion systems compared to the non-immersion system. Furthermore, measurement results of hemispheres sub-structured by substrate conformal imprint lithography are presented. Finally, measurements are presented on various line pairs whose period lengths are close to and below the Abbe limit and it is explained how these can still be resolved.