Spin-transfer MRAM structure and methods
AssigneeEverspin Technologies, Inc.
InventorsFrederick B. Mancoff, Nicholas D. Rizzo
Life of this patent
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Abstract
A spin-transfer MRAM bit includes a free magnet layer positioned between a pair of spin polarizers, wherein at least one of the spin polarizers comprises an unpinned synthetic antiferromagnet (SAF). The SAF may include two antiparallel fixed magnet layers separated by a coupling layer. To improve manufacturability, the layers of the SAF may be non-symmetrical (e.g., having different thicknesses or different inherent anisotropies) to assist in achieving proper alignment during anneal. The total magnetic moment of the SAF may be greater than that of the free magnet layer.
Claims16
A spin-transfer MRAM bit comprising a free magnet layer positioned between a first spin polarizer and a second spin polarizer, wherein at least one of the first and second spin polarizers comprises an unpinned synthetic antiferromagnet (SAF), wherein the unpinned SAF has a first fixed magnet layer with a first thickness, and a second fixed magnet layer with a second thickness that is not equal to the first thickness, and a coupling layer positioned between the first and second fixed magnet layers.
A spin-transfer MRAM bit comprising a free magnet layer positioned between a first spin polarizer and a second spin polarizer, wherein at least one of the first and second spin polarizers comprises an unpinned synthetic antiferromagnet (SAF), wherein the unpinned SAF has a first fixed magnet layer with a first intrinsic anisotropy, and a second fixed magnet layer with a second intrinsic anisotropy that is not equal to the first intrinsic anisotropy, and a coupling layer positioned between the first and second fixed magnet layers.
A method for forming a spin-transfer MRAM bit, comprising:
- forming a first spin polarizer;
- forming a first nonmagnetic spacer layer over the first spin polarizer;
- forming a free magnet layer over the first nonmagnetic spacer layer;
- forming a second nonmagnetic spacer layer over the free magnet layer;
- and
- forming a second spin polarizer over the second nonmagnetic spacer layer;
- wherein the step of forming a first spin polarizer or the step of forming the second spin polarizer includes forming an unpinned synthetic antiferromagnet (SAF), wherein the first fixed magnet layer is formed such that it has a first thickness, and the second fixed magnet layer is formed such that it has a second thickness that is not equal to the first thickness, and it has a coupling layer positioned between the first and second fixed magnet layers.
A method for forming a spin-transfer MRAM bit, comprising:
- forming a first spin polarizer;
- forming a first nonmagnetic spacer layer over the first spin polarizer;
- forming a free magnet layer over the first nonmagnetic spacer layer;
- forming a second nonmagnetic spacer layer over the free magnet layer;
- and
- forming a second spin polarizer over the second nonmagnetic spacer layer;
- wherein the step of forming a first spin polarizer or the step of forming the second spin polarizer includes forming an unpinned synthetic antiferromagnet (SAF), and wherein the unpinned SAF has a first fixed magnet layer with a first intrinsic anisotropy, a second fixed magnet layer with a second intrinsic anisotropy that is not equal to the first intrinsic anisotropy, and a coupling layer positioned between the first and second fixed magnet layers.
Dependencies are inferred from the claim text.