The comparison of multi-stepping algorithms for real-time thickness measurement of transparent thin films using polarization settings

Abstract

This paper presents the comparison of three-, four- and five-step techniques for measuring transparent thin-film thickness of and deposited on BK-7 substrates. The Sagnac interferometer was modified with phase shifting approach for the determination of thin-film thickness. The input light beam was split into reference and testing beams. Before the output light reaching the balanced photodetectors, the real-time signal detection was performed to obtain the output intensities of both beams using three-, four-, and five-polarization settings of an analyzer. The thicknesses could then be efficiently translated from the measured intensities. Thicknesses from three-, four- and five-stepping algorithms were compared with ones from the conventional FE-SEM measurement, and it was discovered that the former performed better with less errors. The findings show that the phase-shifting technique using three-polarization settings is more suitable for the thickness measurement of the transparent thin film.