A 2.8 GHz combined mode of vibration aluminum nitride MEMS resonator with high figure of merit exceeding 45

This paper presents the first demonstration of a high frequency (2.8 GHz), lateral field excited (simple two masks fabrication process), combined lateral-thickness extensional mode of vibration aluminum nitride (AlN) micro-electromechanical systems (MEMS) resonator with unprecedentedly high figure of merit (k
_t
²
·Q> 45). For the first time, a single interdigital electrode was employed to excite a high frequency mode of vibration in an AlN plate (1.5 μm thick) by making use of both the d
₃₃
and d
₃₁
AlN piezoelectric coefficients. The resulting MEMS resonator showed high quality factor, Q~2000, (thanks to the high quality AlN film directly deposit on top of the Silicon substrate) and the highest electromechanical coupling coefficient ever reported for AlN MEMS resonators employing a single electrode, k
_t
²
~2.5% (thanks to the coherent combination of d
₃₃
and d
₃₁
coefficients to transduce one single mechanical mode of vibration).