Scaling magnetic tunnel junction down to single-digit nanometers-Challenges and prospects

Magnetic tunnel junction (MTJ), a spintronics device, has been intensively developed in the past couple of decades because of its high potential in terms of non-volatility, fast operation, virtually infinite endurance, scalability, and compatibility with complementary metal-oxide-semiconductor (CMOS) integrated circuits as well as their process and circuits. Today, high-volume manufacturing of spin-transfer torque magnetoresistive random access memory based on MTJ has been initiated for embedded memory applications in CMOS logic. Whether MTJ is scalable along with the advancement of CMOS technology is critical for the technology's future. Here, we review the scaling of MTJ technology, from in-plane anisotropy MTJs to perpendicular interfacial- or shape-anisotropy MTJs. We also discuss challenges and prospects in the future 1X- and X-nm era.