Combined Thickness and Permittivity Measurement of Thin Layers with Open-Ended Coaxial Probes

Abstract

This paper presents a method to measure both the thickness and the permittivity of thin layers simultaneously with an open-ended coaxial probe. This is achieved by comparing complex permittivity measurements with finite element (FEM) simulations of the probe. The method necessitates a priori knowledge of the backing material permittivity and the frequency variation of the layer permittivity. A finite element model of the probe is made in the FEM simulation software Comsol Multiphysics, and a matrix of simulations spanning the relevant layer thickness and permittivity range is generated. The measured permittivity spectra can then be compared with the simulation matrix to estimate layer thickness and permittivity.