2, Tohoku University, Sendai, , Japan
3, JST-ACCEL, Saitama, , Japan
Nonvolatile spintronics based VLSIs, which are composed of memory cells of magnetic tunnel junctions (MTJ) with high endurance and high speed operation, are attracting much interest for realization of low power consumption edge devices with the arrival of the IoT era [1-3]. Perpendicular anisotropy CoFeB-MgO based MTJ (p-MTJ) with a synthetic ferrimagnetic (SyF) reference layer is a building block in the nonvolatile memory cells [4,5]. Thermal tolerance for annealing at temperature of 400C is required for the integration of the p-MTJs using standard CMOS back-end-of line process. We have demonstrated 10 nm diameter CoFeB-MgO based p-MTJs with the thermal tolerance of 400C . Here, we review development in the p-MTJs [8-10]. In particular, we describe about the material design knowledge of the controlling boron composition of CoFeB free layer, variation of magnetic properties in the reference layer by high temperature annealing, and dependence of the MTJ properties on the sputtering gas species.
This work was supported by STT-MRAM R&D program under Industry-Academic collaboration of CIES consortium, JSPS-EPSRC Core to Core Program, JST-ACCEL, and JST-OPERA.
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