Application of Micromachined $Y$ -Cut-Quartz Bulk Acoustic Wave Resonator for Infrared Sensing

This paper presents the design, fabrication, and characterization of thermal infrared (IR) imaging arrays operating at room temperature which are based on Y-cut-quartz bulk acoustic wave resonators. A novel method of tracking the resonance frequency based upon the measurement of impedance is presented. High-frequency (240-MHz) micromachined resonators from Y-cut-quartz crystal cuts were fabricated using heterogeneous integration techniques on a silicon wafer. A temperature sensitivity of 22.16 kHz/°C was experimentally measured. IR measurements on the resonator pixel resulted in a noise equivalent power of 3.90 nW/Hz^1/2, a detectivity D* of 1 × 10⁵ cm · Hz^1/2/W, and a noise equivalent temperature difference of 4 mK in the 8- to 14-μm wavelength range. The thermal frequency response of the resonator was determined to be faster than 33 Hz, demonstrating its applicability in video-rate uncooled IR imaging. This work represents the first comprehensive thermal characterization of micromachined F-cut-quartz resonators and their IR sensing response.