Thermally Robust Perpendicular SOT-MTJ Memory Cells With STT-Assisted Field-Free Switching

Ya Jui Tsou, Wei Jen Chen, Huan Chi Shih, Pang Chun Liu, C. W. Liu, Kai Shin Li, Jia Min Shieh, Yu Shen Yen, Chih Huang Lai, Jeng Hua Wei, Denny D. Tang, Jack Yuan Chen Sun

Research output: Contribution to journalArticlepeer-review

Abstract

A back-end-of-line compatible 400 °C thermally robust perpendicular spin-orbit torque magnetic tunnel junction (p-SOT-MTJ) memory cell with a tunnel magnetoresistance ratio of 130% is demonstrated. It features an energy-efficient spin-transfer-torque-assisted field-free spin-orbit torque (SOT) switching and a novel interface-enhanced synthetic antiferromagnet (SAF). The optimal SAF with a Ru (9 Å) spacer sandwiched by Co/Pt multilayers has a high SAF coupling field of 2.8 kOe. The parallel magnetic coupling between the CoFeB-based reference layer and the bottom Co/Pt multilayer is enhanced by a magnet-coupling face-centered cubic textured Co/Pt (5 Å) multilayer buffer. The thermally induced Pt-Fe interdiffusion is effectively reduced by the W (3 Å) trilayers of texture-decoupling diffusion multibarrier. The Ta/β -W and TaN/β -W composite SOT channels are thick enough to be the etching stop and sustain 400 °C annealing without transforming to α -W. Using the harmonic Hall voltage measurement, the Ta/W and TaN/W channels exhibit the large effective spin Hall angle of approximately -0.21 and -0.27, respectively. Scaling magnetic tunnel junction (MTJ) down to 30 nm size can reduce the switching time due to single-domain switching based on the micromagnetic simulation. The damping constant of ~0.018 is obtained by the ferromagnetic resonance measurement. A bigger damping constant reduces the switching time as predicted by the calibrated simulation.

Original languageEnglish
Pages (from-to)6623 - 6628
Number of pages6
JournalIEEE Transactions on Electron Devices
Volume68
Issue number12
DOIs
StatePublished - Dec 2021

Keywords

  • Annealing
  • Damping constant
  • field-free switching
  • Magnetic multilayers
  • magnetic tunnel junction (MTJ)
  • Magnetic tunneling
  • Magnetization
  • Magnetomechanical effects
  • Nonhomogeneous media
  • spin Hall angle
  • spin-orbit torque (SOT).
  • Switches

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