Multi-pass spectroscopic ellipsometry

• Published in: Thin solid films 2014-03, Vol.555, p.143-147
• Main Authors: Stehle, Jean-Louis, Samartzis, Peter C., Stamataki, Katerina, Piel, Jean-Philippe, Katsoprinakis, George E., Papadakis, Vassilis, Schimowski, Xavier, Rakitzis, T. Peter, Loppinet, Benoit
• Format: Article
• Language: English
• Subjects: Aluminum; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Multi-pass spectroscopic ellipsometry; Optical instruments, equipment and techniques; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Phase; Physics; Polarimeters and ellipsometers; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Silicon oxide; Very thin films
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.05.148

Spectroscopic ellipsometry is an established technique, particularly useful for thickness measurements of thin films. It measures polarization rotation after a single reflection of a beam of light on the measured substrate at a given incidence angle. In this paper, we report the development of multi-pass spectroscopic ellipsometry where the light beam reflects multiple times on the sample. We have investigated both theoretically and experimentally the effect of sample reflectivity, number of reflections (passes), angles of incidence and detector dynamic range on ellipsometric observables tanΨ and cosΔ. The multiple pass approach provides increased sensitivity to small changes in Ψ and Δ, opening the way for single measurement determination of optical thickness T, refractive index n and absorption coefficient k of thin films, a significant improvement over the existing techniques. Based on our results, we discuss the strengths, the weaknesses and possible applications of this technique. •We present multi-pass spectroscopic ellipsometry (MPSE), a multi-pass approach to ellipsometry.•Different detectors, samples, angles of incidence and number of passes were tested.•N passes improve polarization ratio sensitivity to the power of N.•N reflections improve phase shift sensitivity by a factor of N.•MPSE can significantly improve thickness measurements in thin films.