Magnetic tunnel junction structures and related methods
View Patent ↗The disclosure is directed to spin-orbit torque (“SOT”) magnetoresistive random-access memory (“MRAM”) (“SOT-MRAM”) structures and methods. A new structure of the SOT channel has one or more magnetic insertion layers superposed or stacked with one or more heavy metal layer(s). Through proximity to a magnetic insertion layer, a surface portion of a heavy metal layer is magnetized to include a magnetization. The magnetization within the heavy metal layer enhances spin-dependent scattering, which leads to increased transverse spin imbalance.
1. A structure, comprising:
a magnetic tunnel junction structure including a reference layer, a free layer and a tunneling barrier layer sandwiched between the reference layer and the free layer; and
a spin-orbit torque layer vertically adjacent to the free layer of the magnetic tunnel junction structure, the spin-orbit torque layer including a vertical stack of a first heavy metal layer and a first magnetic layer,
wherein the first heavy metal layer and the first magnetic layer are laterally adjacent to one another and at least one of the first heavy metal layer or the first magnetic layer interfaces with the free layer of the magnetic tunnel junction.
2. The structure of claim 1 , wherein the first magnetic layer has a thickness smaller than or equal to one third of a thickness of the free layer of the magnetic tunnel junction structure.
3. The structure of claim 1 , wherein the first magnetic layer interfaces with the free layer.
4. The structure of claim 3 , further comprising a second magnetic layer on a surface of the spin-orbit torque layer that is opposite to the first magnetic layer.
5. The structure of claim 1 , wherein the first heavy metal layer interfaces with the free layer.
6. The structure of claim 5 , further comprising a second heavy metal layer on a surface of the spin-orbit torque layer that is opposite to the first heavy metal layer.
7. The structure of claim 1 , wherein the first heavy metal layer is on a first surface of the spin-orbit torque layer and a magnetic layer is on a second surface of the spin-orbit torque layer that is opposite to the first surface of the spin-orbit torque layer.
8. A memory device, comprising:
a substrate;
a transistor over the substrate, the transistor having a first source or drain terminal, a second source or drain terminal and a gate terminal; and
a magnetoresistive random access memory cell over the transistor, the magnetoresistive random access memory cell including a magnetic tunnel junction structure and a spin-orbit torque structure vertically adjacent to the magnetic tunnel junction structure and coupled to the first source or drain terminal of the transistor;
wherein the spin-orbit torque structure includes a first heavy metal layer, and a first magnetic insertion layer interfacing with the first heavy metal layer from both a vertical direction and a lateral direction, and
wherein the first magnetic insertion layer is one of a Co and Pt multilayer or a Co and Ni multilayer, and has perpendicular magnetic anisotropy.
9. The memory device of claim 8 , wherein the magnetic tunnel junction structure includes a reference layer, a free layer and a tunnel barrier layer sandwiched between the reference layer and the free layer and wherein the free layer and the reference layer both include perpendicular anisotropy.
10. The memory device of claim 8 , wherein the first heavy metal layer is platinum.
11. The memory device of claim 8 , wherein:
the first heavy metal layer includes a comb shape having at least two tooth elements, and
the first magnetic insertion layer is positioned between the two tooth elements of the first heavy metal layer.
12. The memory device of claim 8 , wherein the first heavy metal layer is one or more of tungsten, platinum, or tantalum.
13. A structure, comprising:
a substrate;
a first heavy metal layer over the substrate;
a first magnetic layer adjacent to the first heavy metal layer, a first surface of the first magnetic layer interfacing a first surface of the first heavy metal layer;
a second magnetic layer adjacent to the first heavy metal layer, a second surface of the second magnetic layer interfacing a second surface of the first heavy metal layer, the second surface of the first heavy metal layer being opposite to the first surface of the first heavy metal layer; and
a second heavy metal layer adjacent to the first magnetic layer, a second surface of the second heavy metal layer interfacing a second surface of the first magnetic layer, the second surface of the first magnetic layer opposing the first surface of the first magnetic layer; and
a magnetic tunnel junction structure vertically adjacent to one or more of the first heavy metal layer or the first magnetic layer, the magnetic tunnel junction structure including a reference layer, a tunneling barrier layer and a free layer,
wherein a combined thickness of the first magnetic layer and the second magnetic layer is smaller than or equal to one third of a thickness of the free layer of the magnetic tunnel junction structure.
14. The structure of claim 13 , wherein the first heavy metal layer and the first magnetic layer are laterally adjacent to one another.
15. The structure of claim 13 , wherein the first heavy metal layer and the first magnetic layer are vertically adjacent to one another.
16. The structure of claim 13 , wherein the first heavy metal layer is one or more of tungsten, platinum, or tantalum.
17. The structure of claim 13 , wherein the first magnetic layer is one of a Co and Pt multilayer or a Co and Ni multilayer, and has perpendicular magnetic anisotropy.
18. The structure of claim 13 , wherein the first magnetic layer is one of a CoFeB magnetic alloy or a NiFe magnetic alloy, and has in-plane magnetic anisotropy.
19. A memory device, comprising:
a substrate;
a transistor over the substrate, the transistor having a first source or drain terminal, a second source or drain terminal and a gate terminal; and
a magnetoresistive random access memory cell over the transistor, the magnetoresistive random access memory cell including a magnetic tunnel junction structure and a spin-orbit torque structure vertically adjacent to the magnetic tunnel junction structure and coupled to the first source or drain terminal of the transistor;
wherein the spin-orbit torque structure includes a first heavy metal layer, and a first magnetic insertion layer interfacing with the first heavy metal layer from both a vertical direction and a lateral direction, and
wherein the first magnetic insertion layer is one of a CoFeB magnetic alloy or a NiFe magnetic alloy, and has in-plane magnetic anisotropy.