Abstract
Coherence scanning interferometry is established as a powerful noncontact, three-dimensional, metrology technique used to determine accurate surface roughness and topography measurements with subnanometer precision. The helical complex field (HCF) function is a topographically defined helix modulated by the electrical field reflectance, originally developed for the measurement of thin films. An approach to extend the capability of the HCF function to determine the spectral refractive index of a substrate or absorbing film has recently been proposed. In this paper, we confirm this new capability, demonstrating it on surfaces of silicon, gold, and a gold/palladium alloy using silica and zirconia oxide thin films. These refractive index dispersion measurements show good agreement with those obtained by spectroscopic ellipsometry.
Highlights
The complex refractive index of a material is one of the most important parameters used to design a variety of optical products and optical coatings
coherence scanning interferometry (CSI) is a well-established technique for surface topography, and the introduction of various approaches including the helical complex field (HCF) function to CSI extended this capability to cover thin film thickness determination
This paper presents an expose of a proposed further extension of the HCF function to the refractive index determination of substrates or absorbing films
Summary
The complex refractive index of a material is one of the most important parameters used to design a variety of optical products and optical coatings. Determination theory based on the HCF function [6,8], it is relatively straightforward to determine the refractive index of absorbing thin films or substrates [7] because this methodology generates potential refractive index functions prior to optimization. This method has the advantages that no additional hardware is required and complex numerical optimization problem is avoided. This paper presents an evaluation of the HCF-based method for the determination of the spectral refractive index and demonstrates the efficacy of the technique by characterizing three different material substrates
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