Evaluation of film adhesion to substrates by means of surface acoustic wave dispersion

For thin film structures acoustically classified as slow-on-fast systems, modeling and evaluation of their interfacial condition are known to be very complex and difficult due to dispersion and multi-mode excitation of acoustic waves. This paper presents a quantitative model and a reliable measurement procedure established for adhesion evaluation of such film structures. An effective interface model employing a virtual intermediate layer is utilized for the dispersion prediction of the surface acoustic wave, which is affected by various interfacial conditions. Through acoustic microscopy experiments, this model presents a potential method to classify the bonding condition. Comparisons with a destructive scratch test and an acoustic imaging verify the failure mode of the film structure.