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Shoji Ikeda1 2 3

1, Tohoku University, Sendai, , Japan
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 [7]. 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.

References:
[1] H. Ohno et al., Tech. Dig. -Int. Electron Devices Meet. 2010, 9.4.1.
[2] T. Endoh et al., IEEE J. Emerging and Selected Topics in Circuits and Systems, Vol. 6, 109 (2016).
[3] T. Hanyu et al., Proceedings of the IEEE, 104, 10, pp.1844-1863 (2016).
[4] S. Ikeda et al., Nature Mater. 9, 721 (2010).
[5] H. Sato et al., Jpn. J. Appl. Phys. 56, 0802A6 (2017).
[6] H. Sato et al., Jpn. J. Appl. Phys. 53, 04EM02 (2014).
[7] H. Honjo et al., 2015 Symp. on VLSI Tech. Dig. of Tech. Paper 2015, T161.
[8] H. Honjo et al., IEEE Trans. Mag. 52, 3401104 (2016).
[9] H. Honjo et al., AIP Adv. 7, 055913 (2017)/.
[10] H. Honjo et al., IEEE Trans. Mag. 53, 2501604 (2017).

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