A planar fluxgate magnetic sensor for on-chip integration

In this paper, we present a planar fluxgate magnetic sensor for on-chip integration using silicon process technology. The fabrication process is simplified by using a newly developed sensing element which is composed of thin-film ferromagnetic cores at the top layer, and excitation and differential pick-up coils. The sensor core used is permalloy film deposited by sputtering. The coils are fabricated using a two-layer metallization process. The fabrication process for the sensing element is suitable for integrating the on-chip interface circuits. In order to achieve the optimum excitation condition, the sensing element structure is investigated by means of computation analysis. The sensing element is fabricated with 2-μm-thick, 1400-μm-long cores and excitation and pick-up coils (25 turns each). The sensing element fabricated using planar technology has a magnetic sensitivity of about 73 V/T at an excitation frequency of 1 MHz and a driver current of 150 mA_p-p.