Spatially‐Resolved Spectroscopic Characterization of Reflective and Transparent Materials at a Micro‐Meter Scale Using Coherence Scanning Interferometry

Abstract

The development of new technologies and innovative products today is often accompanied by the emergence of new micro and nanomaterials. Due to their wider use in many applications, performing accurate characterization of these materials is becoming essential. The high performance of coherence scanning interferometry for materials characterization in terms of topographic, roughness and thickness measurements as well as for tomographic analysis of transparent layers has already been well demonstrated. However, demands regarding the spectral characterization of these materials requires new operation modes using the combination of spectral measurements with high resolution imaging. In this work we present a technique for local spectral measurements by careful processing of the entire interferometric signal over the scanned depth at each pixel in the image, so providing spatially resolved measurements in both the lateral and axial directions. Being a far‐field technique, and because the sample is illuminated with a white light source, spectral information is obtained over large areas (150 × 150 μm2) at the same time and for all the wavelengths. Spectroscopic mapping of a sample consisting of four different materials (Si, Al, Ag, Ti) and depth‐resolved measurements performed through a thin layer of PDMS are reported. Spectral measurements are made over an area of about 1–2 μm2, with an axial resolution of 1 μm, these features being dependent on the optical parameters of the system.