A high-sensitivity MEMS fluxgate sensor with double-layer induction coils fabricated by micro-casting

Abstract This paper presents a novel design of a micro-electro-mechanical-systems (MEMS) fluxgate sensor featuring double-layer induction coils. We utilize the micro-casting process which comprises two steps of using deep reactive ion etching to etch coil molds and filling the molds with molten Zn–Al alloy to form the coils. This process has the capacity to fabricate intricate three-dimensional coil structures, overcoming the limitations associated with the traditional electroplating process. The parameters of the core and the coils are optimized by Maxwell simulation software. Open-loop test results indicate that the fabricated sensor exhibits a sensitivity of 6091 V T −1 , a power consumption of 3.6 mW, a linear range of ± 220 µ T, a noise power density of 681 pT/√Hz@1 Hz and a bandwidth from DC to 122 Hz when excited by a 400 kHz sine wave with a root-mean-square value of 30 mA. Our study shows a significant improvement in sensor performance with a sensitivity at least twice that of comparable MEMS fluxgate sensors. This novel structure of double-layer induction coils not only pushes the design boundaries of MEMS fluxgate sensors but also holds promise for precision magnetic sensing.