Design and Implementation of a 4Kb STT-MRAM with Innovative 200nm Nano-ring Shaped MTJ

Programmability is as a severe challenge in development of spin-transfer torque magnetic random access memory (STT-MRAM). Theoretical analysis have indicated that nano-ring shaped magnetic tunneling junction (NR-MTJ) can achieve lower write current and higher write reliability compared to conventional elliptical-shaped MTJ (E-MTJ). In this work, we successfully patterned the NR-MTJ with 200nm outer diameter and 120nm inner diameter in commercial manufacturing facility, designed and fabricated a 4Kb STT-MRAM test chip with NR-MTJs. Testing results demonstrated successful read and write functionalities of our chip, and proved the theocratically-predicted electrical properties of NR-MTJs.