2D displacement measurement by sinusoidal phase modulation interferometer (comparison of two demodulation methods)

Abstract

2D measurement technology with sub-nanometer resolution is needed for the development of semiconductors with three-dimensional structures. In this study, the sinusoidal phase modulation interferometer was developed by incorporating an electro-optical modulator into an optical length measurement interferometer. Two types of phase demodulation algorithms are applied to image data to measure two-dimensional in-plane displacement. The first is a method that uses an artificial interference signal and a phase-locked loop, and the second is a method that obtains the phase by adding or subtracting between the data sampled at 12 times the modulation frequency.