Thermally Robust Perpendicular SOT-MTJ Memory Cells with STT-Assisted Field-Free Switching
Journal
IEEE Transactions on Electron Devices
Journal Volume
68
Journal Issue
12
Pages
6623-6628
Date Issued
2021
Author(s)
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 ?) 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 ?) multilayer buffer. The thermally induced Pt-Fe interdiffusion is effectively reduced by the W (3 ?) 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. ? 1963-2012 IEEE.
Subjects
Damping constant
field-free switching
magnetic tunnel junction (MTJ)
spin Hall angle
spin-orbit torque (SOT)
Antiferromagnetic materials
Binary alloys
Cobalt compounds
Damping
Energy efficiency
Etching
Iron alloys
Multilayers
Platinum alloys
Semiconductor storage
Spin orbit coupling
Switching
Tantalum compounds
Textures
Tunnel junctions
Tunnelling magnetoresistance
Face-centered cubic
Ferromagnetic resonance measurements
Magnetic tunnel junction
Micromagnetic simulations
Spin transfer torque
Synthetic antiferromagnets
Thermally induced
Tunnel magnetoresistance
Magnetic devices
SDGs
Type
journal article