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

Abstract

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 micro-magnetic sensor with mutual inductance is designed and the sensor is fabricated by Micro-Electro-Mechanical System technology. The micro-magnetic 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 mutual inductance micro-magnetic sensor is reduced and the detectivity can be significantly enhanced. The experiment result shows that the sensitivity of the proposed mutual inductance micro-magnetic sensor is 46.5 mV/Oe in the range of 0 Oe~0.3 Oe, the voltage noise is as low as 0.8 μV/√Hz, and the noise level reaches 17.2 μOe/√Hz. Therefore, the detectivity of the proposed mutual inductance micro-magnetic sensor can reach 17.2 μOe (1.72 nT), which has significant potential in several areas, such as biosensing and geomagnetic navigation.