First BEOL-compatible, 10 ns-fast, and Durable 55 nm Top-pSOT-MRAM with High TMR (>130%)

We demonstrated a novel Top-pSOT-MRAM structure by directly fabricating the SOT channel on top of a standard STT-MTJ device. This integration breakthrough significantly simplifies the implementation of SOT technology, as it leverages the standard STT-MRAM process flow. The key element of our proposed Top-pSOT-MRAM is the top electrode comprising a Ru etch-stop layer and a W/Ta composite SOT material, which serves as a bridge connecting the free layer of the MTJ and the Top SOT channel. This Top-pSOT-MRAM device exhibits a high TMR exceeding 130% and excellent thermal stability during the BEOL process up to 400 ^o C. When assisted by STT, the field-free SOT switching achieves impressive speed, as fast as 10 ns, and demonstrates robust endurance exceeding 10 ¹⁰ cycles. Top-pSOT-MRAM at a scaled size of 55 nm maintains a high thermal stability factor (Δ) of 62, guaranteeing a retention time of 10 years with a low error rate of 1 ppm.