Analysis of Low-k Dielectric Thin Films on Thick Substrates by Transmission FTIR Spectroscopy

摘要

Transmission Fourier-transform infrared (T-FTIR) spectra of thin films on thick substrates are characterized by strong interference fringes that hamper quantitative analysis of the observed thin film absorption bands. In this article, we review and present methods for removing these fringes to extract the pure thin film absorption coefficient from the experimental T-FTIR spectra. To illustrate the benefits of a recently developed method for removing such fringes, we analyze T-FTIR spectra for a series of a-SiO2 and a-SiOC:H thin films typically utilized in nano-electronic interconnect structures as low permittivity (i.e. low-k) interlayer dielectrics. The sources and magnitude of the errors present in analysis of both the uncorrected and corrected experimental T-FTIR spectra are compared. We demonstrate that conventional analysis of the uncorrected low-k a-SiOC:H T-FTIR spectra can lead to substantial quantitative errors that are dramatically reduced using the described method for appropriately removing the experimental thin film fringes. (C) The Author(s) 2014. Published by ECS. All rights reserved.