Fabrication of Magnetic Tunnel Junctions with Amorphous CoFeSiB Ferromagnetic Electrode for Magnetic Field Sensor Devices

The magnetic tunnel junctions (MTJs) with a soft magnetic CoFeSiB amorphous electrode and a MgO barrier layer were fabricated. A double annealing process was carried out to obtain the linear resistance response to the external magnetic field. The effect of the annealing temperature on the sensitivity of magnetic sensors was systematically investigated. We achieved a high sensitivity of 40%/Oe, where the sensitivity is defined as TMR/(2 H k ), where TMR is the tunnel magnetoresistance ratio and H k is the magnetic anisotropy field of the free layer of MTJs.