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• Published in: IEEE transactions on electron devices 2020-01, Vol.67 (12), p.5368
• Main Authors: Miura, Sadahiko, Nishioka, Koichi, Naganuma, Hiroshi, Nguyen T V A, Honjo, Hiroaki, Ikeda, Shoji, Watanabe, Toshinari, Inoue, Hirofumi, Niwa, Masaaki, Tanigawa, Takaho, Noguchi, Yasuo, Yoshizuka, Toru, Yasuhira, Mitsuo, Endoh, Tetsuo
• Format: Article
• Language: English
• Subjects: Damage; Fokker-Planck equation; Interface stability; Low resistance; Magnetoresistivity; Physical vapor deposition; Pulse duration; Reactive ion etching; Switching; Thermal stability; Tunnel junctions; Tunnel magnetoresistance
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2020.3025749

We fabricated a quadruple-interface perpendicular magnetic tunnel junction (MTJ) (Quad-MTJ) down to 33 nm using physical vapor-deposition, reactive ion etching, and damage-control integration process technologies that we developed under a 300-mm process. We demonstrated the greater scalability and higher writing speed of Quad-MTJ compared with double-interface perpendicular MTJ: 1) it has twice the thermal stability factor—1X nm Quad-MTJ can achieve 10 years retention—while maintaining a low resistance-area product and high tunnel magnetoresistance ratio; 2) smaller overdrive ratio of write voltage to obtain a sufficiently low write-error rate; 2) smaller pulsewidth dependence of the switching current; and 4) more than double the write efficiency at 10-ns write operation down to 33-nm MTJ. The effective suppression of the switching current increase for higher write speeds was explained by the spin-transfer-torque model using the Fokker-Planck equation. Our 33-nm Quad-MTJ also achieved excellent endurance (at least 1011) owing to its higher write efficiency and low-damage integration-process technology. It is thus a promising method for low power, high speed, and reliable STT-MRAM with excellent scalability down to the 1X nm node.