Everspin Technologies, Inc.
Magnetic field sensor and method of manufacture

Abstract:

A magnetic field sensor that includes a differential bridge in which each path of the bridge includes a first type of magnetic field sensing device and a second type of magnetic field sensing device. The first and second types of magnetic field sensing devices differ in the magnetic moment imbalance present in the synthetic antiferromagnets (SAFs) included in their reference layers such that that different types of devices produce a different response to perpendicular magnetic fields, but the same response to in-plane magnetic fields. Such different magnetic moment imbalances in the SAFs of magnetic field sensing devices included in a bridge allow for accurate sensing of perpendicular magnetic fields in a differential manner that also cancels out interference from in-plane fields. Techniques for producing such magnetic field sensing devices on an integrated circuit are also presented. Moreover, the free layers within the magnetic field sensing devices can be adjusted in terms of their sensitivity range and level of sensitivity by manipulating the kink filed (Hk) for those free layers.