Pellicle membrane for spectroscopic ellipsometry of viscous samples

Spectroscopic ellipsometry is a common non-destructive technique used to measure the thickness of thin films as well as their optical refractive index (n(λ)) and absorption coefficient (k(λ)). This technique relies on collecting a specular reflection from the surface of a sample over a range of wavelengths while measuring the polarization of the reflected light. Spectroscopic ellipsometry is predominantly used for non-viscous samples since measurements on viscous samples, such as liquids, are limited due to variations that cause inhomogeneity in the surface. Previous techniques have focused on measuring the optical parameters at the boundaries of liquids and solid materials or air. A light guide is used to propagate the light through a channel to the proximity of this liquid/material or air boundary. For ellipsometers with horizontal stages this is common practice, but many ellipsometers have vertical stages making it extremely difficult to use this method. In this presentation we describe a pellicle membrane that has made it possible to perform spectroscopic ellipsometry on liquid samples. As an example, we present results of measurements on distilled water allowing for accurate d