A statistical study of magnetic tunnel junctions for high-density spin torque transfer-MRAM (STT-MRAM)

We have demonstrated a robust magnetic tunnel junction (MTJ) with a resistance-area product RA=8 Ω—μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> that simultaneously satisfies the statistical requirements of high tunneling magnetoresistance TMR ≫ 15σ(R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> ), write threshold spread σ(Vw)/≪Vw≫ ≪7.1%, breakdown-to-write voltage margin over 0.5V, read-induced disturbance rate below 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> , and sufficient write endurance, and is free of unwanted write-induced magnetic reversal. The statistics suggest that a 64Mb chip at the 90-nm node is feasible.