Manufacturing and characterization of CMOS-MEMS magnetic field microsensors with isolated cavities

Abstract

The study investigates a magnetic field (MF) microsensor with isolated cavities manufactured utilizing complementary metal oxide semiconductor (CMOS)-microelectromechanical system technology. This microsensor, which is a type of magnetic transistor, comprises four identical magnetic sensing elements, each featuring an emitter, a base, two collectors, and an additional collector. The magnetic transistor operates on the principles of the Lorentz force. This force is employed to modulate the electrical properties of the transistor, responding to changes in the surrounding MF. The MF microsensor chip is fabricated using the commercial CMOS process. Upon completing the CMOS process, post-processing is employed to etch the silicon substrate of the microsensor chip, generating isolated cavities on the silicon substrate. These isolated cavities effectively mitigate substrate leakage current, enhancing the sensitivity of the MF microsensor. The experimental results reveal that the sensitivity of the microsensor without isolated cavities is 60 mV T−1. In contrast, the microsensor with isolated cavities exhibits a sensitivity of 121 mV T−1. A comparison between microsensors with and without isolated cavities depicts that the sensitivity of the MF microsensor with isolated cavities doubled.