Metal Stress-Optic Effect and Its Application in Stress Measurement

Abstract Although the stress-optic effect has been widely used in stress analysis of dielectric materials, its application on metals was very limited. This is because metals cannot be penetrated by electromagnetic waves. This paper investigated the stress-optic effect of thin Cu films using a transmission method. The retardation of transmitted light caused by applied stress was obtained using an interferometric method. Based on the experimentally obtained relationship between stress and change in phase, the stress-optic coefficients of Cu film were determined. Then, experiments were conducted to demonstrate application of the stress-optic effect of metals on the stress measurement of a substrate/film assembly.