Investigation of magnetostrictive film bulk acoustic resonators (MFBAR) for magnetic field sensing applications

This paper describes the realization of a miniaturized magnetic field sensor that is based on a film bulk acoustic resonator (FBAR) and works at similar to 0.87952 GHz resonant frequency. The sensor has a multilayer stack of Si/SiO2/Pt/ZnO/Fe65Co35 thin films with Fe65Co35 as a magnetic field sensing layer and zinc oxide (ZnO) as a piezoelectric actuation layer. The influence of an externally applied magnetic field (0-1992 Oe) has been investigated in terms of resonance frequency shift due to Delta E-effect. High magnetostrictive composition Fe65Co35 (65/35) was utilized for the optimal sensing response. The MFBAR resonator series resonance frequency (fs), parallel resonance frequency (fp), electromechanical coupling coefficient (K-t(2)), quality factor (Q), and figure of merit (FOM) were obtained 0.87952 GHz, 0.88252 GHz, 0.84%, 740.74 and 6.21, respectively. The magnetic sensor shows enhanced sensitivity (S) of 0.357 kHz/Oe with outstanding performance at high frequency and large magnetic field range (0-1992 Oe). A modified Butterworth-Van Dyke (mBVD) equivalent circuit model was developed and circuit parameters are extracted. The mBVD model provides insights into changes in the electrical behavior of the device when the sensor is exposed to a range of magnetic fields. This investigation represents a new kind of magnetic field sensor that is miniaturized, power efficient, high sensitivity, and very useful for low-field sensing applications in the limited space regime.

Automated summary

This paper describes the realization of a miniaturized magnetic field sensor that is based on a film bulk acoustic resonator (FBAR). The sensor has a multilayer stack of thin films with a magnetic field sensing layer and a piezoelectric actuation layer, providing enhanced sensitivity and high frequency performance.