Study of Frequency Trimming Ability and Performance Enhancement of Thin-Film Piezoelectric-on-Silicon MEMS Resonators by Joule Heating via Localized Annealing

This article deliberately explores the frequency trimming and performance enhancement of piezoelectric MEMS resonators through localized annealing induced by Joule heating. Targeting the effective postfabrication treatment of thin-film piezoelectric-on-silicon (TPoS) resonators, we employ a novel annealing approach that modifies the silicon resonator body-bottom electrode interface to enable meticulous resonance frequency trimming and enhanced overall performance. By applying a controlled dc current directly through the resonator's body, precise resonance frequency shifts on the order of 0.1%-0.4% and significant increase in quality factor, from 981 to 2155, from 8214 to 9362, have been realized for rectangular-plate and disk-shaped resonators, respectively. Furthermore, this localized annealing process reduces the motional impedance from 3.43 to 1.65 k $\Omega $ for a rectangular-plate resonator and from 1.79 to 1.58 k $\Omega $ for a disk-shaped resonator, thus demonstrating its viability as a postfabrication treatment technique for a wide variety of MEMS devices. These results highlight the great potential of Joule heating-induced localized annealing in advancing RF systems that demand high precision, reliable filtering, and stable timing functions. This work provides new insights into the thermal annealing effects on MEMS resonators and lays a foundation for future innovations in related microsystem technologies.