Improvement of Thermal Tolerance of CoFeB-MgO Perpendicular-Anisotropy Magnetic Tunnel Junctions by Controlling Boron Composition

H. Honjo, S. Ikeda, H. Sato, S. Sato, T. Watanabe, S. Miura, T. Nasuno, Y. Noguchi, M. Yasuhira, T. Tanigawa, H. Koike, M. Muraguchi, M. Niwa, K. Ito, H. Ohno, T. Endoh

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

We investigated annealing temperature $T-{a}$ dependence of tunnel magnetoresistance (TMR) ratio and magnetic properties for perpendicular-anisotropy (CoFe)100-XBX/MgO magnetic tunnel junctions (MTJs) with single (CoFe)100-XBX/MgO interface (s-MTJ) and double CoFeB-MgO interface (d-MTJ) structures with various boron compositions X. High TMR ratio over 100% was observed in the s-MTJ with X=35 at.% after annealing at 360 °C-400 °C, whereas the s-MTJ with X=30 at.% showed the degradation of TMR ratio with the increase of Ta above 360 °C, resulting from the decrease of perpendicular anisotropy. The d-MTJ with X=25 at.% maintained high TMR ratio up to Ta = 400°C owing to its higher perpendicular anisotropy compared with the s-MTJ. The difference of perpendicular anisotropy between the s-MTJ and the d-MTJ can be attributed to higher interfacial anisotropy together with lower saturation magnetization of the d-MTJs. The lower saturation magnetization is attributable to two MgO layers that suppress boron diffusion from CoFeB layers, which was verified by cross-sectional line analysis using electron energy-loss spectroscopy.

Original languageEnglish
Article number7383297
JournalIEEE Transactions on Magnetics
Volume52
Issue number7
DOIs
Publication statusPublished - 2016 Jul

Keywords

  • CoFeB-MgO
  • STT-MRAM
  • magnetic tunnel junction

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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