EXTRACTION OF D31 PIEZOELECTRIC COEFFICIENT OF ALN THIN FILM

Piezoelectric materials have the property of electro-mechanical coupling, which is very useful in Micro Electro Mechanical Systems (MEMS). Aluminium Nitride (AlN) thin film is an ideal candidate for resonators in on-chip front end circuit. The piezoelectric coupling coefficient d(31) is responsible for the excitation in longitudinal mode resonators. Direct measurement of the value of d(31) is still an area of research. We propose a method to extract the piezoelectric coefficient d(31) from the transmission characteristics of a resonator. The average extracted value of d(31) is -0.943 pC/N with standard deviation 0.21 pC/N, which is comparable with reported values.