High-precision surface measurement with an automated multiangle low coherence interferometer.

We propose a novel measurement system based on a low coherence Michelson interferometer and six-axis hexapod platform to accurately measure structures with high aspect ratio using different tilt angles of the measured surface. In order to realize automatic measurement, the system is designed to automatically perform autofocusing, adjust the tilt angle of the test surface, make surface measurements, and merge the measurement data sets. Due to certain topography, e.g., structures with high aspect ratio, the interferometer cannot obtain enough reflected light to evaluate the height information in some areas of the test surface. For this reason, we developed a measurement system that uses measurements from different tilt angles of the test surface and stitching algorithms to realize a complete surface measurement data set. The performance of the proposed measurement system is evaluated experimentally and compared to the results of measurements using a perthometer.