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

Experimental techniques used to measure structural parameters of thin films such as thickness, density, and coverage provide important insights into t he 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), electr on spectroscopy for chemical analysis (ESCA), and optical ellipsometry-to m easure the thickness of molecularly thin perfluoropolyether (PFPE) polymer films on silicon substrates and carbon overcoats. PFPE films are commonly u sed to lubricate surfaces in magnetic recording devices. Here, we use XRR t o measure the absolute thickness of the films, which, in turn, is used to t est the validity of ESCA and ellipsometry thickness measurements. Excellent agreement is found among the three methods, provided that a 25-Angstrom el ectron mean-free path (MFP) is used for the PFPE film and the substrate in ESCA (single MEP model), that the bulk PFPE refractive index is used in ell ipsometry, and that adventitiously adsorbed hydrocarbons are properly taken into account. (C) 2000 Academic Press.