Stress measurement of thin film on flexible substrate by using projection moiré method and heterodyne interferometry

Abstract

, "Stress measurement of thin film on flexible substrate by using projection moiré method and heterodyne interferometry," Opt. Eng. 55(6), 064102 (2016), doi: 10.1117/1.OE.55.6.064102. Abstract. We propose a stress measurement system based on a projection moiré method and heterodyne interferometry for thin films on a flexible substrate. In the measurement setup, a CMOS camera in which every pixel can receive a series of heterodyne moiré signals by using a continuously relative displacement with a constant velocity is used. Furthermore, the phase of the optimized sinusoidal curve and the surface profile of the flexible substrate are determined using a least-squares sine fitting algorithm. The thin-film stress is obtained by representing the cross-sectional curve of the surface profile by using a polynomial fitting method, estimating the resultant curvature radii of the uncoated and coated substrates, and using these two radii in the corrected Stoney formula. The proposed measurement system has the advantages of high accuracy, high resolution, and high capacity for substrates with high flexibility and a large measurement depth. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.