A CMOS-MEMS Ultrasensitive Thermometer Using Internal Resonance Iuduced Frequency Combs

This work demonstrates a CMOS-MEMS resonant thermometer with a temperature coefficient of frequency (TCF) as high as 59.2× compared to that of a regular resonator-based counterpart using frequency combs in an internal resonating (IR) beam resonator. Particularly, the time-varying amplitude modulated resonance signal due to energy exchange between the 1
^st
and 3
^rd
flexural modes in the IR resonator yields combs in the frequency domain. The comb generation occurs within a certain frequency range, and the comb spacing exhibits a certain dependency on the offset from the onset IR. By driving the resonator at a fixed frequency around its 1
^st
mode, the offset changes and therefore the comb spacing changes in response to temperature changes, yielding a TCF up to -11,481 ppm/°C in the comb spacing shift, a 59.2× higher against the -194 ppm/°C of the resonance frequency of a reference beam resonator. The results verify the IR induced frequency combs can serve as a promising approach towards ultrasensitive sensors.