A Review of Eigenmode and Frequency Control in Piezoelectric MEMS Resonators

Piezoelectric microelectromechanical systems (MEMS) resonators possess favorable properties, such as strong electromechanical coupling, high ${Q}$ , and polarized linear transduction, making them ideal for various applications, including timing, sensing, and RF communication. However, due to process nonidealities and temperature variations, these resonators characteristics may deviate from their designed frequency and resonant eigenmode, requiring careful compensation for stable and precise operation. Furthermore, certain devices, such as gyroscopic resonators, have two eigenmodes that need to be adjusted for frequency proximity and cross-mode coupling. Therefore, mode-shape manipulation can also be important in piezoelectric resonators and will be another focus of this article. Techniques for frequency and eigenmode control are classified into device- or system-level tuning, trimming, and compensation. This article will compare and discuss the effectiveness of these techniques in specific applications to provide a comprehensive understanding of frequency and eigenmode control in piezoelectric MEMS resonators, aiding the development of advanced MEMS devices for diverse applications.