Calibrating ESCA and ellipsometry measurements of perfluoropolyether lubricant thickness

Abstract

X-ray reflectivity (XRR) has been used as an absolute measurement of the thickness of perfluoropolyether (PFPE) lubricant layers on silicon substrates to determine the validity of thickness measurements by electron spectroscopy for chemical analysis (ESCA) and ellipsometry. Excellent agreement is found between these three methods, provided that a 25 /spl Aring/ escape depth for the PFPE film is used in ESCA and the bulk refractive index of the PFPE is used in ellipsometry. It is also essential to properly account for adventitiously adsorbed hydrocarbons.