Thickness measurements of thin perfluoropolyether polymer films on silicon and amorphous-hydrogenated carbon with X-ray reflectivity, ESCA and optical ellipsometry

Abstract

Experimental techniques used to measure structural parameters of thin films such as thickness, density, and coverage provide important insights into the physical properties of these films. Structural parameters are also often used to predict the eventual performance of thin films. In this study, we use three different measurement techniques - X-ray reflectivity (XRR), electron spectroscopy for chemical analysis (ESCA), and optical ellipsometry - to measure the thickness of molecularly thin perfluoropolyether (PFPE) polymer films on silicon substrates and carbon overcoats. PFPE films are commonly used to lubricate surfaces in magnetic recording devices. Here, we use XRR to measure the absolute thickness of the films, which, in turn, is used to test the validity of ESCA and ellipsometry thickness measurements. Excellent agreement is found among the three methods, provided that a 25-Å electron mean-free path (MFP) is used for the PFPE film and the substrate in ESCA (single MFP model), that the bulk PFPE refractive index is used in ellipsometry, and that adventitiously adsorbed hydrocarbons are properly taken into account. (C) 2000 Academic Press.