STT-MRAM reference layer having substantially reduced stray field and consisting of a single magnetic domain

摘要

An STT MTJ cell is formed with a magnetic anisotropy of its free and reference layers that is perpendicular to their planes of formation. The reference layer of the cell is an SAF multilayered structure with a single magnetic domain to enhance the bi-stability of the magnetoresistive states of the cell. The free layer of the cell is etched back laterally from the reference layer, so that the fringing stray field of the reference layer is no more than 15% of the coercivity of the free layer and has minimal effect on the free layer.

主权项

1. An STT MTJ cell comprising:
a seed layer; a reference layer formed on said seed layer; a tunneling barrier layer formed on said reference layer; a free layer formed on said tunneling barrier layer; a capping layer formed on said free layer; wherein a width of said free layer is less than a width of said reference layer; and said reference layer is formed as a synthetic anti-ferro magnetically coupled pair of multi-layers of [Co/Pd], [Co/Ni] or [Co/Pt] alloys, said pair denoted AP1 and AP2 and said pair having perpendicular magnetic anisotropy (PMA), or formed as PMA L10 tetragonal alloys or comprising PMA L10 tetragonal alloys and wherein said anti-ferromagnetic coupling between said AP1 and AP2 occurs at a first or second RKKY peak by use of a coupling layer of Ru, Ir, Rh or Os, formed at a thickness between approximately 0.4 nm, for a first RKKY peak and approximately 0.9 nm for a second RKKY peak and dusted on both faces by a layer of Co of thickness approximately 4 A to further strengthen said coupling; said free layer and said reference layer have a magnetic anisotropy that is oriented perpendicular to their planes of formation; and wherein a stray field of said reference layer is substantially limited to a fringing field at its opposite lateral edges, whereby said stray field does not affect the magnetization of said free layer; and wherein a single domain state of said reference layer is formed to promote well defined magnetoresistive bi-stability.