Evaluation of imperfect gold/glass interfaces using scanning acoustic microscopy

A quantitative measurement method for the evaluation of thin film adhesion is desired in a wide range of thin film applications. As an example, we investigated the bonding conditions of gold layers on glass substrate. The interface was modified by introducing a thin layer of silicone oil. With increasing oil thickness we assume the adhesion to get worse. Using quantitative scanning acoustic microscopy (SAM) surface acoustic waves (SAW) dispersion curves were measured. Significant variations with the oil layer thickness were found. By fitting the measured data to theoretical curves, stiffness constants which describe the quality of adhesion, can be derived. Our theoretical model is based on the quasi-static model developed by BAIK and THOMPSON. Variation of the interfacial stiffness constants leads to good adhesion Rayleigh-type SAWs propagate on the samples, whereas in the case of bad adhesion a Sezawa-type SAW is generated. The SAM measurements are in good agreement with destructive measurements using the scratch test.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.