Simultaneous measurement of thicknesses and refractive indices of multiple layers by a low-coherence confocal interference microscope

Abstract

We propose a novel technique for simultaneous measurement of layer thicknesses and refractive indices of multiple layers. It is based on a combination of a confocal microscope and low-coherence interferometry. We derived an expression for the geometrical thickness and the refractive index of each layer from both tracing of a marginal ray accepted by a microscope objective and optical path matching conditions. Experimental verification of this method is illustrated by several samples that have a maximum of 13 layers. The geometrical thicknesses and refractive indices thus derived agreed well with those measured by a micrometer or cited from the literature.