NONDESTRUCTIVE DYNAMIC EVALUATION OF THIN NITI FILM ADHESION

Thin layer materials may be considered as composites of the substrate and deposited film. The degree of stress transfer between the two comp onents, i.e. the adhesion, will influence the dynamical response of th e thin layer composite characterized by its resonance frequency. A sem i-empirical adhesion parameter gamma was defined which varies between 1, indicating perfect adhesion, and 0, indicating no adhesion. Resonan ce measurements were carried out on the Ni50Ti50/SiO2/Si system, emplo ying a high-resolution mechanical vibration technique. To confirm that the parameter gamma truly reflects the quality of the adhesion, NiTi films of different thicknesses were sputter-deposited on a Si substrat e and 1 - gamma, reflecting the degree of deviation from pure elastic coupling through the interface, was measured. It was found that NiTi/S i yields gamma values of about 0.8, reflecting partial adhesion. Annea ling improves the adhesion of NiTi films on Si. This improvement of th e adhesion was followed in situ.