Combined low-coherence interferometry and spectrally resolved reflectometry for nondestructive characterization of small-diameter high-aspect ratio micro-fabricated and micro-machined structures and multilayer membranes

摘要

We propose novel tool employing both low coherence interferometer and spectrally resolved reflectometer sensor. We discuss application of this novel tool for measurements of the narrow high aspect ratio structures. We demonstrate that the visible reflectance spectrum of such structures allows us to extend range of interferometer to measure depth trenches with diameter from 2 μm to 1 mm, with reproducibility 10 nm - 100 nm depending on range of the thin film thickness. We also present of this novel tool for measurement of ultra-thin coated pressure sensor membranes. Application of an auxiliary spectral reflectometer allows correcting for systematic errors of low coherence interferometer which can be as large as 1.5 - 2 μm.