Non-Destructive Characterization of Multilayer Structures by Low-Coherence Interferometry

Z.V. Djinovic(a)(b), L. Manojlovic(b), M.C. Tomic(c)
a: Institute of Sensor and Actuator Systems, Vienna University of Technology, Vienna 1040, Austria
b: Integrated Microsystems Austria, Wiener Neustadt 2700, Austria
c: Institut Bezbednosti, Belgrade 11000, Serbia

Abstract

We present here a non-destructive technique for characterization of multilayer structures based on low-coherence interferometry. This technique is capable to give information of physical thickness and index of refraction of the subjected sample regardless of how many different layers exist along the optical trip. The main limitation is if the investigated materials are transparent for the used optical wavelength. We performed sensing set up in the form of single-mode fiber-optic Michelson interferometer composed of one 2×2 optical coupler. There were tested three and five layers foils composed of sandwich structure made by alternation of polyarilate (PAR) and glue layer. We achieved a success discriminate the interface between the two different materials with accuracy of about 40 nm by analyzing low-coherence interferograms.