Manufacturable high-speed CMOS back-end-of-line-compatible spin-orbit-torque magnetic random-access memory with β-tungsten

Abstract The magnetization switching driven by spin-orbit torque (SOT) has garnered significant interest due to its potential for realizing Spin-Orbit Torque Magnetic Random-Access Memory (SOT-MRAM). This design features distinctly separated read and write paths, promising enhanced device reliability and a more favorable window for minimizing read/write interference. Among many explored heavy metals which possess strong spin-orbit coupling, tungsten stands out as a particularly intriguing material, exhibiting substantial spin–orbit torques in thin films stabilized in the A15 (β-phase) structure. However, challenges arise from the low spin Hall angles (~ 0.01) observed in the energetically favorable α-phase tungsten. Integration of β-W with modern CMOS processes, particularly under the back-end-of-line (BEOL) thermal budget (400℃ 30 mins), remains problematic. In this study, we report a design strategy for achieving BEOL thermal budget in tungsten layers, focusing on β-tungsten (β-W) as a promising material for efficient spin-orbit torques (SOTs) with a recorded high spin Hall conductivity of approximately 4500 Ω-1cm-1 measured by spin-torque ferromagnetic resonance (ST-FMR) and Harmonic Hall resistance. Finally, we demonstrate 1 ns SOT switching with 146% tunneling magnetoresistance based on the proposed β-W film stack. This comprehensive investigation provides a manufacturable and CMOS comparable path for next-generation low-power MRAM and spintronics.