Design and Characterization of an ALN Piezoelectric Mems Magnetometer

This work presents an in-house design, fabrication, and characterization of a resonant piezoelectric MEMS device using the Thin-film Piezoelectric-on-Silicon (TPoS) process of AlN to realize a Lorentz force-based magnetic sensor. The magnetometer is designed by employing the flapping-mode of the rectangular resonator fixed at the center of the two opposite edges. The resonator is characterized by Laser Doppler Vibrometer and electrical measurements which show a resonance frequency of 356 kHz with
$Q$
of 767 in air. The output voltage of the magnetometer shows a linear increase with magnetic field strength indicating sensitivity and responsivity of 79.28 mV/T and 2128 ppm/T respectively. The frequency response of the device also shows a phase inversion upon reversing the direction of the magnetic field. The measured instability in the magnetic field was 0.283 µT extracted from Allan deviation, to the best our knowledge the lowest value among state-of-the-art A1N MEMS magnetometers.