Micromachined Two-Dimensional Weak Magnetic Field Sensors of Soft Magnetic Film/Planar Coil Laminated

Two-dimensional magnetic sensors of soft magnetic film/planar coil laminated have outstanding advantages in miniaturization and integration. However, due to the cumbersome process and complicated structure of the sensor, its yield rate is extremely low, and the gap between magnetic films is large, resulting in increased leakage flux and low sensitivity. Therefore, a high-performance soft magnetic film with through-holes/planar coil laminated micromagnetic sensor with mutual inductance (MI) is designed and the sensor is fabricated by micro-electromechanical system technology. The micromagnetic sensor can be processed in 15 steps, with a yield rate of more than 95%, and the gap between magnetic films can be effectively reduced, resulting in reduced leakage flux and improved sensitivity. Moreover, the effect of coil resistance is eliminated, the noise level of the proposed MI micromagnetic sensor is reduced and the detectivity can be significantly enhanced. The experiment result shows that the sensitivity of the proposed MI micromagnetic sensor is 46.5 mV/Oe in the range of 0 Oe-0.3 Oe, the voltage noise is as low as 0.8 mu V/root Hz, and the noise level reaches 17.2 mu Oe/v Hz. Therefore, the detectivity of the proposed MI micromagnetic sensor can reach 17.2 mu Oe (1.72 nT), which has significant potential in several areas, such as biosensing and geomagnetic navigation.