High frequency AlN MEMS resonators with integrated nano hot plate for temperature controlled operation

This paper presents the design and experimental verification of the first MEMS resonator ovenized by means of an integrated nano hot plate suspended over the micromechanical resonant element. This first prototype is formed by a composite structure in which a fully anchored Aluminum Nitride (AlN) Lateral Field Excited-Floating (LFE-F) Contour-Mode MEMS resonator (CMR) and a nanoscale heating element are perfectly overlapped and separated by a sub-micron air gap. The placement of the heating element outside the body of the resonator, but suspended over it, allowed maintaining the electromechanical properties of the device unchanged (same k_t²·Q compared to the non-ovenized case). This resulted in a 968 MHz ovenized microresonator with quality factor, Q, of ~1800, electromechanical coupling coefficient, k_t², of ~0.9% and motional resistance, R_m, of ~50 Ω. At the same time, efficient ovenization of the MEMS resonator (CMR temperature rise factor of 18.3 K/mW) is achieved by scaling the dimensions of the heating element (i.e. implementing a nano hot plate) and minimizing the air gap between the resonator and the heater.