Sputtered A1N Thin Films for Piezoelectric MEMS Devices

Piezoelectric films have been demonstrated to be attractive for micromechanical systems (MEMS) devices. Among the piezoelectric films used, AlN film has been less explored. In this study, AlN resonators and accelerometers, utilizing longitudinal and transverse piezoelectric effects respectively, were demonstrated. Resonators with Q of 1000 and electromechanical coupling (k_t ²) of 6.5% were achieved at ~2 GHz. Accelerometers were fabricated and tested with charge sensitivities ranging between 0.06 to 0.45 pC/g depending on device designs. Important material properties of sputtered AlN films - C₃₃ of 435 GPa, e₃₃ of 1.55 C/m², and e₃₁ of -0.58 C/m² - were extracted by fitting finite element analysis (FEA) simulated values to measured results.