Spin transfer MRAM device with magnetic biasing
First Claim
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1. A method to improve performance of a magnetic random access memory, comprising:
- providing an MTJ magnetic memory element, having an anisotropy field whose direction of magnetization in a free layer may be switched by passing through said free layer a spin polarized current having, in the absence of any external magnetic field, a first minimum value;
providing a magnetic biasing field generated by a current in a wire that passes over said MTJ; and
through application of said magnetic biasing field, at a magnitude that about equals or exceeds said anisotropy field, enabling said MTJ free layer to be switched by passing through said free layer a spin polarized current having a second minimum value that is less than said first minimum value.
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Abstract
The addition of segmented write word lines to a spin-transfer MRAM structure serves to magnetically bias the free layer so that the precessional motion of the magnetization vector that is set in play by the flow of spin polarized electrons into the free layer allows said magnetic vector to be switched rather than to oscillate between two easy axis directions.
123 Citations
17 Claims
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1. A method to improve performance of a magnetic random access memory, comprising:
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providing an MTJ magnetic memory element, having an anisotropy field whose direction of magnetization in a free layer may be switched by passing through said free layer a spin polarized current having, in the absence of any external magnetic field, a first minimum value; providing a magnetic biasing field generated by a current in a wire that passes over said MTJ; and through application of said magnetic biasing field, at a magnitude that about equals or exceeds said anisotropy field, enabling said MTJ free layer to be switched by passing through said free layer a spin polarized current having a second minimum value that is less than said first minimum value. - View Dependent Claims (2, 3, 4)
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5. A process to manufacture a magnetic random access memory, comprising:
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depositing an under-layer on a substrate; depositing an antiferromagnetic pinning layer on said under-layer; depositing a magnetically pinned fixed reference layer on said pinning layer; depositing a tunneling barrier layer on said pinned layer; depositing a free layer on said pinned layer; depositing a non-magnetic layer on said free layer; depositing, on said non-magnetic layer, a magnetic drive layer that spin polarizes electrons that pass through it; depositing a capping layer, having a top surface, on said magnetic drive layer; magnetizing said magnetic drive layer in a direction perpendicular to said top surface; patterning all deposited layers to form an MTJ stack; forming a bit line that contacts said upper surface and runs in a first direction; and forming a word line that is insulated from said bit line and runs in a second direction that is different from said first direction, whereby current through said word line serves to magnetically bias said free layer when spin polarized electrons, generated by said magnetic drive layer, pass through said free layer, thereby enabling a direction of magnetization in said free layer to be switched. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A magnetic random access memory, comprising:
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an under-layer on a substrate; an antiferromagnetic pinning layer on said under-layer; a magnetically pinned fixed reference layer on said pinning layer; a tunneling barrier layer on said pinned layer; a free layer on said pinned layer; a non-magnetic layer on said free layer; on said non-magnetic layer, a magnetic drive layer that spin polarizes electrons that pass through it; a capping layer, having a top surface, on said magnetic drive layer; said magnetic drive layer being magnetized in a direction perpendicular to said top surface; all deposited layers having been patterned in to the form an MTJ stack; a bit line that contacts said upper surface and runs in a first direction; and a word line that is insulated from said bit line and runs in a second direction that is different from said first direction, whereby current through said word line serves to magnetically bias said free layer when spin polarized electrons, generated by said magnetic drive layer, pass through said free layer, thereby enabling a direction of magnetization in said free layer to be switched. limited set will be simultaneously half selected. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification