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<p>One candidate for ultimate non-volatile memory with ultralow power consumption is voltage-controlled magneto-resistive random-access memory (VC-MRAM). To develop VC-MRAM, it is important to fabricate high-performance magnetic tunnel junctions (MTJs), which require the epitaxial growth of an ultrathin ferromagnetic electrode on a crystalline tunnel barrier using a mass-manufacturing-compatible process. In this study, the grain-to-grain epitaxial growth of perpendicularly magnetized CoFe ultrathin films on polycrystalline MgO (001) was demonstrated using cryogenic-temperature sputtering on 300 mm Si wafers. Cryogenic-temperature sputtering at 100 K suppressed the island-like initial growth of CoFe on MgO without hampering epitaxy. Sub-nanometer-thick CoFe layers exhibited remarkable perpendicular magnetic anisotropy (PMA). An even larger PMA was obtained using an Fe-doped MgO (MgFeO) tunnel barrier owing to improved uniformity of the CoFe layer. A 0.8-nm-thick CoFe layer grown on MgFeO exhibited a magnetic damping constant as low as 0.008. The ultralow magnetic damping enables voltage-driven magnetization switching with a low write-error rate (WER) below 10<sup>-6</sup> at a pulse duration of 0.3 ns, and WER on the order of 10<sup>-3</sup> even for a relatively long pulse duration of 1.5 ns. These properties achieved using a mass-manufacturing deposition process can promote the development of VC-MRAM and other advanced spintronic devices based on MTJs.</p>

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Cryogenic-temperature grain-to-grain epitaxial growth of high-quality ultrathin CoFe layer on MgFeO tunnel barrier for high-performance magnetic tunnel junctions

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  • 发表日期：

    2025年10月17日

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  • Tomohiro Ichinose,
  • Tatsuya Yamamoto,
  • Takayuki Nozaki,
  • Kay Yakushiji,
  • Shingo Tamaru,
  • Shinji Yuasa

摘要

One candidate for ultimate non-volatile memory with ultralow power consumption is voltage-controlled magneto-resistive random-access memory (VC-MRAM). To develop VC-MRAM, it is important to fabricate high-performance magnetic tunnel junctions (MTJs), which require the epitaxial growth of an ultrathin ferromagnetic electrode on a crystalline tunnel barrier using a mass-manufacturing-compatible process. In this study, the grain-to-grain epitaxial growth of perpendicularly magnetized CoFe ultrathin films on polycrystalline MgO (001) was demonstrated using cryogenic-temperature sputtering on 300 mm Si wafers. Cryogenic-temperature sputtering at 100 K suppressed the island-like initial growth of CoFe on MgO without hampering epitaxy. Sub-nanometer-thick CoFe layers exhibited remarkable perpendicular magnetic anisotropy (PMA). An even larger PMA was obtained using an Fe-doped MgO (MgFeO) tunnel barrier owing to improved uniformity of the CoFe layer. A 0.8-nm-thick CoFe layer grown on MgFeO exhibited a magnetic damping constant as low as 0.008. The ultralow magnetic damping enables voltage-driven magnetization switching with a low write-error rate (WER) below 10-6 at a pulse duration of 0.3 ns, and WER on the order of 10-3 even for a relatively long pulse duration of 1.5 ns. These properties achieved using a mass-manufacturing deposition process can promote the development of VC-MRAM and other advanced spintronic devices based on MTJs.