Researchers from Beihang University, Aix-Marseille University and Université Paris-Saclay, in collaboration with Truth Memory Corporation, demonstrated a highly efficient orbital torque-driven magnetic tunnel junction (MTJ).
The researchers say that in standard SOT-MRAM devices, the β-phase tungsten (β-W) write electrodes suffer from high electrical resistance and strict thickness limitations. To overcome both issues, the researchers harnessed the hidden degree of freedom, the orbital angular momentum.
The researchers found that a precisely tuned ruthenium-tungsten (Ru/W) bilayer write electrode can be used as a highly efficient charge-to-orbital-to-spin converter, and so maintain a strong perpendicular magnetic anisotropy and tunneling magnetoresistance (TMR), even when produced in a high-temperature manufacturing process. The researchers fabricated the MTJ devices on an industrial 8-inch MRAM pilot line and verified that the devices demonstrate highly uniform resistance across the wafer.
Performance tests confirmed this design as a highly viable commercial candidate because it dramatically lowered writing voltage and enabled ultra-fast 28.7-picosecond switching, while unlocking a shared-electrode structure that can shrink device area by an impressive 45% for massive future power and density improvements.
Earlier this year, TMC successfully demonstrated the world's first 8 Mb SOT-MRAM chip, using a 110 nm technology node. TMC developed a fully-integrated wafer-level SOT-MRAM manufacturing flow based on an autonomous 8-inch platform compatible with mainstream CMOS back-end processes. TMC says that through optimized magnetic stack engineering and low-damage etching with precise sidewall passivation, it has developed high-performance SOT-MTJ arrays with 150 nm.
