Multi-sensitive temperature sensor platforms using aluminum nitride MEMS resonators

This paper presents three MEMS platforms that exhibit multiple thermal sensitivities and multi-frequency capabilities. Multiple sensors with a variety of operating frequencies and thermal sensitivities can co-exist in the same device wafer. Aluminum nitride is the active layer of the three platforms. The impact of stack and substrate modifications on the performance of test devices is discussed as well. To test the platforms' performance, temperature sensors are realized using Lamb-acoustic-wave micro-electro-mechanical (MEMS) resonators, each one featuring a different thermal coefficient of frequency that scales with frequency. Resonators designed for frequencies between 200 MHz to 1.5 GHz operate at their first symmetric mode (S0) and feature first-order TCFs in the range from  −12 up to  −30 ppm °C⁻¹ depending on the frequency and design. Furthermore, TCFs of devices can be tailored to get smaller values through process variations. The platforms exhibit high electromechanical performance, with quality factors in excess of 1500 and maximum effective coupling coefficient of 6.43% for radio frequency (RF) applications above 1 GHz. (paper)