An Integrated Micro-Fluxgate Magnetic Sensor with Sputtered Ferromagnetic Core

In this paper a double axis planar micro-Fluxgate magnetic sensor is presented. The ferromagnetic core material, the Vitrovac 6025 X, has been deposited on top of the coils with the DC-magnetron sputtering technique, a new type of procedure with respect the existing solutions in the field of Fluxgate sensor. This procedure allows us to obtain a core with the good magnetic properties of the amorphous ferromagnetic material, typical of a core 25 mum thick, but with a thickness of only 1 mum, typical of a core electrodeposited. The micro-Fluxgate has been realized in a 0.5 mum CMOS process using copper metal lines to realize the excitation coil and aluminum metal lines for the sensing coils. Applying a triangular excitation current of 18 mA peak at 100 kHz the magnetic sensitivity achieved is about 0.45 mV/muT, suitable for detecting the Earth´s magnetic field (plusmn50 muT), while the linearity error is 1.15% of the full scale. The maximum angle error of the sensor, evaluating the Earth magnetic field, is 3.4deg. The power consumption of the sensor is about 13.7 mW