Aluminum Nitride nano-plate infrared sensor with self-sustained CMOS oscillator for nano-watts range power detection

This paper presents, for the first time, a fast (thermal time constant of 1.3 ms) and sensitive (responsivity of 310 Hz/μW) Infrared detector consisting of an Aluminum Nitride (AlN) nano-plate resonator (NPR) connected to a compact and low power CMOS self-sustained oscillator (fabricated in the AMIS 0.5 μm CMOS process) as a direct frequency readout. A high performance (quality factor Q = 1283 and electromechanical coupling coefficient k_t² = 1.56%) MEMS resonant structure based on a thin AlN (250 nm thick) NPR coated with Si₃N₄ (100 nm thick) as IR absorber was fabricated and tested, showing a measured temperature coefficient of frequency (TCF) of -35 ppm/K and FEM simulated temperature rise factor of 72.5 mK/μW. Thanks to the high electromechanical performance of the MEMS resonator, a compact and low power (2.3 mW) self-sustained CMOS oscillator circuit was used as a direct frequency readout, enabling the demonstration of a novel uncooled IR detector with a low Noise Equivalent Power (NEP) of 3.5 nW/Hz^1/2.