Piezoelectric MEMS Resonators: A Review

Since two decades piezoelectric MEMS resonator research has been making a headway by leaps and bounds in multiple fronts such as micro/nanofabrication techniques, device and system design, monolithic integration, packaging, material engineering, etc. Piezoelectricity based frequency selective resonant tanks are an integral part of radio frequency communication, inertial sensors, infrared sensors, environmental monitoring modules, energy harvesters, etc. To improve the functionality of the aforementioned modules it is cardinal to understand the underlying concepts of resonator design, material selection, and performance enhancement techniques. Here in this review paper, a comprehensive overview of various piezoelectric thin-film material properties along with different commercial microfabrication platforms with CMOS integration facility is presented. The device characteristics greatly depend on the resonator mode shape and thus suitable modes and thin-film material configurations can be chosen depending on the target frequency, application, and power budget requirements. In addition to device modeling, a synopsis of the several acoustic and material engineering approaches to enhance the figure of merit of the resonator has been presented. The future avenues of piezoelectric MEMS cover a wide spectrum of possibilities such as 5G communication, quantum processing, frequency combs, photonics integration, gesture sensors, etc.