First Demonstration of Interface-Enhanced SAF Enabling 400°C-Robust 42 nm p-SOT-MTJ Cells with STT-Assisted Field-Free Switching and Composite Channels

CMOS compatible 400°C-robust 42 nm perpendicular spinorbit torque magnetic tunnel junction (p-SOT-MTJ) devices with the tunnel magnetoresistance (TMR) ratio of 130% is demonstrated for the first time by the interface-enhanced synthetic anti-ferromagnet (SAF) and the improved ion-beam etching (IBE). The record high 440oC thermal robustness of SAF is achieved. The SAF field (H SAF ) and the magnetic coupling between Co/Pt multilayer (ML) and reference layer are enhanced by the magnet-coupling fcc-texture multilayer (MCFTM) buffer. The Pt-Fe inter-diffusion during thermal stress is effectively reduced by the W(3Å)-based texture-decoupling diffusion multi-barrier (TDDMB) for magnetic field immunity. The composite SOT channel of TaN/W and Ta/W breaks the thickness limitation of β-W (< ~5 nm) and enlarges the MTJ etching window. The TaN/W channel exhibits the large effective spin Hall angle of ~ -0.27. The deterministic field-free SOT writing with spin-transfer torque (STT) assist is achieved. The size dependence on STT-assisted SOT switching is investigated using micromagnetic simulation.