On the influence of magnetic flux guide location to the out-of-plane magnetic field sensing of chip-scale AMR sensor

Abstract

The anisotropic magneto-resistive (AMR) sensors could detect external magnetic fields through the change of magnetization and resistance. Typically made of thin films, the AMR sensors are generally only sensitive to the in-plane magnetic field. The AMR sensors with Ni pillar array structures as magnetic flux guides have been presented to enhance the detection of out-of-plane magnetic fields. However, the magnetic flux lines transmitted from adjacent pillars may interact with each other, so that their directions will be changed accordingly. Thus, the locations of pillar guides may influence the distribution of magnetic flux lines, and further change the out-of-plane magnetic field sensing performance of the AMR sensor. To gain insight on this design consideration, this study introduces a serpentine routing AMR film with flux guides distributed along each wire gaps. By varying the gap of the serpentine AMR wire and the distance between the pillar and the AMR wire, the influence of flux guide location on the out-of-plane magnetic field sensing is investigated. Through microfabrication processes, the flux guide array can be batch fabricated and defined at appropriate locations, and further monolithically integrated with AMR sensor. Measurements show that for a serpentine AMR sensor with a gap of 70μm, the sensitivity can be increased by 4.6-fold as the distance between flux guide and AMR film decreases from 20 μm to 0 μm. Moreover, when the flux guide fixed in the middle of gap of the serpentine AMR sensor, the sensitivity can be improved by 5.6-fold as the gap decreases from 70 μm to 50 μm.