13.3 A 22nm 32Mb Embedded STT-MRAM with 10ns Read Speed, 1M Cycle Write Endurance, 10 Years Retention at 150°C and High Immunity to Magnetic Field Interference

STT-MRAM is a promising solution for next-generation embedded non-volatile memory (NVM), supporting a wide range of applications. Compared to traditional embedded Flash [1]–[2], STT-MRAM is a CMOS-compatible low-temperature back-end-of-the-line (BEOL) memory, requiring only 2-to-5 extra masks. It is a byte-alterable NVM with excellent write speed, write endurance (>1M cycles), and high-temperature data retention capability. In this work, a 32Mb STT-MRAM using a 0.0456µm2 bit cell is fabricated using a 22nm ultra-low leakage (ULL) CMOS process. A WL-voltage generation system, with distributed local constant-current kickers, and power-gating switches is used to overdrive the WL to achieve a higher read margin, while maintaining low-standby current and fast wake-up. Sense amplifiers (SAs) with segment trimming and adaptive timing control are designed to support reliable reads from −40 to 125°C. A smart write, with multiple write pulses controlled by adaptive write-verify and a temperature compensated write bias, is used for efficient write operation. Magnetic field interference is reduced by six orders of magnitude by adding a shielding film to the packaged die.