A Lorentz force magnetometer based on a piezoelectric-on-silicon square-extensional mode micromechanical resonator

Abstract

In this letter, we present a Lorentz force magnetic field sensor based on a thin-film piezoelectric-on-silicon (TPoS) CMOS-compatible resonator for the detection of an out-of-plane (perpendicular to the plane of fabrication) magnetic field. We here exploit the fundamental breathing mode of vibration in a suspended square plate, which is commonly referred to as the square-extensional (SE) mode. The symmetric stress profile of the SE mode avails stresses in the two orthogonal in-plane axes to be effectively coupled into a charge output through the piezoelectric transducers. This in turn enhances the output motional current from the device, which effectively determines the responsivity of the device. In this context, the responsivity has been defined as a ratio of output motional current to the external magnetic field, which has been further normalized against the input reference current of the device. The reported device has recorded a responsivity of 6950 ppm/T (μA/A.T) at a resonant frequency of 5.28 MHz and a reasonable mechanical quality (Q) factor of 1056 in air.

Single-structure 3-axis Lorentz force magnetometer based on an AlN-on-Si MEMS resonator

“…A similar square-plate structure has been reported previously for measuring the z-axis magnetic field, which utilizes two separate excitation current tracks mirrored across the diagonal axis of the plate to realize a loop current and excites the square-extensional mode 19 . Different from previous work, the device reported herein uses four separate excitation current tracks, which allows more flexible manipulation of four excitation currents in direction and frequency so that two vibration modes can be effectively excited for measurement of all 3-axis magnetic fields.…”

“…2b . For the measurement of the z-axis magnetic field, the square-extensional mode, as reported in previous work 19 , is used when all four excitation currents are injected in a loop, as shown in Fig. 2c .…”

Si-based MEMS resonant sensor: A review from microfabrication perspective

“…The canning speed and high order resonance is a characteristic of Q factor, amplitude and the mode-shape of the Si cantilever, having the resolution of first order and second order resonance to be as 0.83 nm, 0.42 nm respectively [175]. Ghosh et al presented a fabrication of magnetometer based WE mode thin film-piezoelectric-on -Si resonator showing the resonance frequency as 18 MHz and Q factor value (Q = 1500) and sensitivity as 63.27 mV/T under room temperature [176]. 2019 [196] x.…”

Si-based MEMS Resonant Sensor: A Review from Microfabrication Perspective

“…The canning speed and high order resonance is a characteristic of Q factor, amplitude and the mode-shape of the Si cantilever, having the resolution of first order and second order resonance to be as 0.83 nm, 0.42 nm respectively [175]. Ghosh et al presented a fabrication of magnetometer based WE mode thin film-piezoelectric-on -Si resonator showing the resonance frequency as 18 MHz and Q factor value (Q = 1500) and sensitivity as 63.27 mV/T under room temperature [176]. Phillippe et al [183] presented a co-integration of NEMS-CMOS oscillator having 0.35 µm circuit on a Silicon-on-insulation substrate.…”