A model for the accurate determination of the electromechanical coupling factor of thin film SAW devices on non-insulating substrates

We propose a circuital model that simulates the frequency response of surface acoustic wave (SAW) delay lines made on piezoelectric thin films on non-insulating substrates. The model, which takes into account the parasitic elements that distort the frequency response (due to the conductive substrate, airborne coupling and mounting), allows accurate values of the piezoelectric properties of the films (k² and ν_s) to be obtained. This model has been applied to SAW delay lines made on AlN thin films deposited on different silicon substrates. We show that the values deduced for k² if parasitic effects are not considered can be underestimated by up to 20 times.