A multiple height-transfer interferometric technique

Abstract

We propose a multiple height-transfer interferometric technique based on concepts from both multiple wavelength interferometry and wavelength scanning interferometry. Conventional multiple wavelength interferometry requires accurate wavelength information for large step height measurement, while wavelength scanning interferometry is limited by mode-hop-free tuning range. Using the multiple reference heights, it is possible to bypass the wavelength determinations and achieve large step height measurement using relative phase changes. By applying this technique with a proposed multiple height calibration artifact, we experimentally demonstrated accuracy better than 1 micron over 100 mm in a workshop environment.