Surface profile measurement of a highly reflective silicon wafer by phase-shifting interferometry

Abstract

In phase-shifting Fizeau interferometers, the phase-shift error and multiple-beam interference are the most common sources of systematic error affecting high-precision phase measurements. The nonsinusoidal waveforms can be minimized by applying synchronous detection with more than 4-sample. However, when the phase-shift calibration is inaccurate, these algorithms cannot eliminate the effects of nonsinusoidal characteristics. Moreover, when measuring the surface profile of highly reflective samples, the calculated phase is critically determined not only by the decrease in the fringe contrast but also by the coupling error between the harmonics and phase-shift error. In this paper, the phase errors calculated by conventional phase-shifting algorithms were estimated by considering the coupling error. We show that the 4N−3 algorithm, comprising the polynomial window function and the DFT term, has the smallest phase error among the conventional phase-shifting algorithms. The surface profile of the highly reflective silicon wafer was measured using a wavelength-tuning Fizeau interferometer and the 4N−3 algorithm.