Acoustically-engineered multi-port AlN-on-silicon resonators for accurate temperature sensing

This paper reports on a novel silicon microresonator that is acoustically engineered to facilitate simultaneous yet independent piezoelectric transduction of multiple resonance modes with large difference in their temperature coefficient of frequency (TCF) and integer frequency ratios. A three-port aluminum-nitride-on-silicon (AlN-on-Si) microresonator prototype implemented based on this technique has two energy-trapped modes at 109 MHz and 218 MHz, with a TCF difference of ~7 ppm/°C, which are separately transduced through two isolated electrical ports. A small beat frequency extracted from an integer combination of these modes has a linear TCF of ~8300 ppm/°C, suitable for sensing the resonator temperature with high accuracy and resolution.