An AlN-on-Si resonant IR sensor array with a large temperature coefficient of frequency

This work reports on novel AlN-on-Si flexural-mode resonators with a high fill-factor used as Infrared (IR) sensors. The devices are designed to achieve large temperature coefficient of frequency (TCF) utilizing the thermal expansion coefficient mismatch of different layers in the resonant stack. A 2×2 array of 4.6 MHz resonators with a quality factor (Q) of ~1140 is designed and fabricated using the InvenSense CMOS-MEMS process. Measured TCF values are as high as -137 ppm/K, noticeably higher than the expected TCF derived from temperature coefficient of elasticity (TCE) of AlN and silicon. The reported TCF value in this work is more than four times larger than the previously reported values for AlN-or silicon-based resonators and resonant detectors.