Broadband Light Profile Microscopy: A Rapid and Direct Method for Thin Film Depth Imaging

Abstract

Light profile microscopy† (LPM) is a recently developed technique of optical inspection that is used to record micrometer scale images of thin film cross-sections on a direct basis. This technique uses a novel right-angle imaging geometry that shows outstanding contrast for subtle interface structures and morphologies that are invisible to conventional methods of inspection. When laser sources are used for sample illumination, image contrast is provided by luminescence and elastic and/or inelastic scatter. When a white-light excitation source is used for LPM, primary contrast is obtained from elastic scatter, while secondary contrast results from refraction, secondary transmission, and secondary reflection from material phases. We term this mode of inspection broadband light profile microscopy (BB-LPM). It is implemented with a compact, easily aligned apparatus and minimal sample preparation, and it shows outstanding interface contrast similar to laser LPM. In this work we demonstrate BB-LPM as a method for direct imaging of the layers structures of a variety of thin film samples of industrial and manufacturing interest.