Thin layer mechanical constants extraction using SAW and stratified Green functions - examples of SAW sensitivity to silica layer

A complete sequence of softwares has been developed to identify mechanical parameters of thin layers made of aluminum and silica deposited on piezoelectric substrates. It starts from SAW (surface acoustic wave) devices measurements and the software's sequence includes - automatic extraction of SAW velocities from measurements - computation of SAW velocity in layered media - automatic identification of material parameters to fit extracted SAW velocities. The sequence is completed with a powerful periodic FEA/BIM (finite element analysis/boundary integral method) software which enables to take into account the presence of a silica layer over aluminum IDT (inter-digited transducer). The paper describes the overall method and gives some numerical results for quartz substrate.