Thickness Control of Coatings by Means of Modulated IR Radiometry Francisco Macedo,* Filipe Vaz, Ana C. Fernandes, Jean L. Nzodoum Fotsing, Juergen Gibkes, Josef Pelzl, Bruno K. Bein Introduction In contrast to the materials development approach, con- sisting of changing the deposition conditions in order to obtain thin films most appropriate for a certain protective or decorative application, in this work thin films prepared by reactive magnetron sputtering are analyzed from a different point of view, namely with respect to the film thickness. To this finality, sets of multifunctional TiC x O y thin films of similar compositions and structural arrangements of approximately equal thermal transport properties, but different thicknesses are analyzed with respect to the effective thermal transport properties and the film thicknesses by means of modulated IR radiometry. The values obtained for the film thickness by this non-contact non-destructive thermal wave technique are compared with the data obtained by microscopic destructive mea- surements, in order to analyze the error limits and limitations of film thickness measurements based on modulated IR radiometry. Applying modulated IR radiometry, a thermal wave technique based on the excitation of thermal waves in two- layer systems by means of modulated laser beam heating and on the detection of the thermal response by IR radiometry, appropriate for remote detection in deposition chambers and industrial applications, [1] and using an inverse solution of the two-layer thermal wave problem, [2] by which direct relations are established between the relative extrema of the inverse calibrated thermal wave phase lag signals measured as a function of the heating modulation frequency, the thermal parameters of thin films and coatings are determined, [3] namely the ratio of the thermal effusivities coating-to-substrate, the coating’s thermal diffusion time, and the coating thickness. Due to the fact that the inverse solution of the two-layer thermal wave problem is given in analytical mathematical form and based on the principles of error propagation, the error limits for the thermal coating parameters and for the Full Paper F. Macedo Physics Department, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal E-mail: fmacedo@fisica.uminho.pt F. Vaz, A. C. Fernandes Physics Department, University of Minho, Campus de Azure ´m, 4800-058 Guimaraes, Portugal J. L. N. Fotsing, J. Gibkes, J. Pelzl, B. K. Bein Exp.Phys.III, Solid State Spectroscopy, Ruhr-University Bochum, D-44780 Bochum, Germany Coatings prepared by reactive magnetron sputtering of approximately equal thermal trans- port properties but differing coating thicknesses are analyzed by means of non-contact non- destructive modulated IR radiometry. For the quantitative interpretation, the measured thermal wave signals are calibrated, using the signals measured for a homogenous opaque solid of smooth surface. The relative minima of the inverse calibrated phase lag signals are interpreted with respect to the effective thermal transport properties and to the coating thickness using an inverse solution of the two-layer thermal wave problem. Based on measurements of various coatings, the limitations of this thermal wave method and the errors of measurement for the coating thickness are discussed by comparing with microscopic measurements. S592 Plasma Process. Polym. 2009, 6, S592–S598 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/ppap.200931503