A Micro-Oven Controlled Dual-Mode Piezoelectric MEMS Resonator With ± 190 ppb Stability Over −40 to 105 °C Temperature Range

This letter presents a dual-mode piezoelectric microelectromechanical system (MEMS) resonator with an in-chip micro-oven for resonator temperature control. The piezoelectric MEMS resonator simultaneously operates in width-extensional (WE) mode with a high temperature turnover point, and torsion-bending (TB) mode with a large temperature coefficient of frequency (TCF) based on a phase-locked loop based system. Exploiting the difference in frequency-temperature characteristics of these two modes, accurate temperature sensing and precise close-loop micro-oven heating control are achieved by phase locking the resonator at its turnover point temperature of WE mode. Measured real-time frequency stability of the reported micro-oven controlled MEMS resonator is ±190 ppb over an extended industrial temperature range of -40 °C to 105 °C, indicating potential applications in high-end timing field, such as macro base stations and instrumentations.