As mobile electronics industry pushes forward, their products demand lower power,smaller components, and greater integration. To help achieve these goals, high-Q micromachined resonators provide an avenue to bring low-power oscillators, sensors, and multi-modal filters onchip. Recently, thin-film piezoelectric-onsubstrate(TPoS) resonators have proved to offer low motional impedances with high Q in air and excellent linearity (high power handling). In these resonators, the piezoelectric layer drives and senses the vibration of a resonant body formed from the substrate (Figure 1). For the lateral-mode resonator lateral dimensions of the device (defined by lithography) determine theresonant frequency. At higher frequencies, the acoustic wavelength decreases; forcing the device features (width) to become excessively small, and consequently causing the motional impedance to rise. To compensate for the scaled transduction area, larger device lengths or higher order modes can be utilized. This will increase the overall resonant structure size allowing for a greater transduction area and electromechanical coupling.



"3D schematic of a 3rd order TPoS resonator"



"Mode shape of the 3rd order TPoS resonator"



"SEM of a typical 3rd order TPoS resonator with acoustic reflectors"