Novel highly scalable multi-level cell for STT-MRAM with stacked perpendicular MTJs

Abstract

We fabricated a new scalable multi-level cell for spin transfer torque magnetoresistive random-access memory that consists of stacked perpendicular magnetic tunnel junctions (MTJs) with a diameter of 50nm using one step etching. The cell features series-connecting MTJs using perpendicular magnetic anisotropy at the CoFeB/MgO interface and a well controlled stray field from the pinned layers resulting in Hshift~0. The cell demonstrated four-level operation with low-voltage switching (<; 0.5 V).