Perpendicular spin transfer torque (STT) memory cell with double MgO interface and CoFeB layer for enhancement of perpendicular magnetic anisotropy

摘要

A magnetic tunnel junction (MTJ) for use in a magnetoresistive random access memory (MRAM) has a CoFeB alloy free layer located between the MgO tunnel barrier layer and an upper MgO capping layer, and a CoFeB alloy enhancement layer between the MgO capping layer and a Ta cap. The CoFeB alloy free layer has high Fe content to induce perpendicular magnetic anisotropy (PMA) at the interfaces with the MgO layers. To avoid creating unnecessary PMA in the enhancement layer due to its interface with the MgO capping layer, the enhancement layer has low Fe content. After all of the layers have been deposited on the substrate, the structure is annealed to crystallize the MgO. The CoFeB alloy enhancement layer inhibits diffusion of Ta from the Ta cap layer into the MgO capping layer and creates good crystallinity of the MgO by providing CoFeB at the MgO interface.