3T2M canted-type x SOT-MRAM: Field-free, high-energy-efficiency, and high-read-margin memory toward cache applications

Abstract

We propose a novel cell structure of spin–orbit torque (SOT) magnetic random-access memory (MRAM), which consists of three transistors and two canted-type x SOT magnetic tunnel junctions (3T2M) with opposite canting angle (+φ/-φ) on a shared heavy-metal, enabling a self-referencing scheme. Owing to the canting-angle-dependent switching polarity, the 3T2M unit keeps switching to complementary states without any complex structure, corroborating an excellent application potential for practical CMOS integration. Moreover, upon tailoring the canting angle and the ratio of field-like over damping-like torque in the free layer, the developed architecture demonstrates efficient and reliable field-free magnetization switching with a significantly improved read sensing margin (230 mV and 160 mV for reading “1” and “0”) and outstanding thermal stability (Δ∼70). The 3T2M cell exhibits 0.25 ns ultra-fast write speed, a 6 × reduced write energy of 35.41 fJ, and 23.65 fJ for “1” and “0” than the state-of-the-art.

Keywords

• Spin–orbit torque
• Canted type-x MTJ
• SOT-MRAM
• Sensing margin
• Reliability