Ellipsometric measurement of solid fluorocarbon film thickness on magnetic recording media

Abstract

Solid fluorocarbon films were deposited on carbon overcoated magnetic recording media. The films were made by direct ion beam deposition of fluorocarbon monomers. This paper presents ellipsometric measurements on films over a range of thickness from 0.5 to 12.5 nm. Film thickness was measured using ellipsometry, and the chemical composition was studied using x-ray photoelectron spectroscopy (XPS). A high-speed ellipsometer was set up to map thickness over the whole media surface. The ellipsometric angle Δ was found to be linearly related with the film thickness. Since the escape depth of the XPS is comparable to the film thickness, the XPS senses the underlying carbon as well as the carbon in the film. As a result, the apparent ratio of fluorine to carbon depends on the film thickness. The ion beam deposition technique can be used to produce films with controlled thickness and uniform composition.