First demonstration of field-free SOT-MRAM with 0.35 ns write speed and 70 thermal stability under 400°C thermal tolerance by canted SOT structure and its advanced patterning/SOT channel technology

Abstract

For the first time, we demonstrated 55 nmCMOS/ spin-orbit-torque-device hybrid magnetic randomaccess memory (SOT-MRAM) cell with magnetic field free writing. For field free writing, we developed canted SOT device under 300 mm BEOL process full compatible with 400°C thermal tolerance. Moreover, we developed its advanced process as follows; SOT channel layer PVD process for high spin Hall angle under 400°C thermal tolerance, low damage RIE technology of MTJ for high TMR/thermal stability factor (Δ) and ultra-smooth surface metal via process under SOT channel to reduce contact resistance. By above developed technologies, our canted SOT devices fabricated under a 400°C thermal tolerance successfully achieved fast write speed of 0.35 ns without an external magnetic field, a large enough Δ of 70 for non-volatile memory (retention time is over 10 years), and a high TMR ratio of 167%, for the first time. Moreover, we successfully demonstrated field free SOT-MRAM performance.