Highly manufacturable multi-level perpendicular MTJ with a single top-pinned layer and multiple barrier/free layers

In this paper, we first report a novel and highly manufacturable multi-level perpendicular magnetic tunnel junction (p-MTJ) with a single top-pinned layer and multiple barrier/free layers. In the proposed p-MTJ structure, all tunnel barriers and free layers lie under a thick pinned layer, which enables good resistance control and large coercivity due to the effect of small film roughness. We also developed a new CoFeB-based free layer and writing scheme to control the stray field and spin-transfer torque. As a result, four stable and well-separated resistance states were obtained in resistance-voltage curves with a 65-nm top-pinned p-MTJ.