Ellipsometric characterization of CrTiAlN coating deposited at low temperatures by unbalanced magnetron sputtering

Ellipsometric characterization is presented of a CrTiAlN hard coating deposited by unbalanced magnetron sputtering at low temperatures. Such coatings find applications where the tool material cannot withstand temperatures exceeding 200 °C. The Cr/CrN/CrTiAlN coatings deposited using the UDP-850 equipment is characterized by UV-VIS and IR ellipsometry. A FIB cross-section is made and the thickness of the coating is measured using SEM. The roughness of the coating surface is determined by AFM. The ellipsometric measurements yielded data on the phase difference Δ, amplitude ratio ψ, the frequency dependent real (e1(ω)) and imaginary (e2(ω)) part of the dielectric function and the corresponding refractive and extinction indexes n(ω) and k(ω). The optical parameters are modelled by regression analysis implemented using the WVASE© software. A very good fit is achieved between the measured optical data and the corresponding models. The results show that the ellipsometric characterization data can be used to determine the surface structure, chemical composition and optical reflection characteristics of CrTiAlN hard coatings.