Spin transfer torque tunneling magnetoresistive device having a laminated free layer with perpendicular magnetic anisotropy
View Patent ↗A spin transfer torque magnetic junction includes a magnetic reference layer structure with magnetic anisotropy perpendicular to a substrate plane. A laminated magnetic free layer comprises at least three sublayers (e.g. sub-layers of 6 to 30 Angstroms of CoFeB, CoPt, FePt, or CoPd) having magnetic anisotropy perpendicular to the substrate plane. Each such sublayer is separated from an adjacent one by a tantalum dusting layer. An insulative barrier layer (e.g. MgO) is disposed between the laminated free layer and the magnetic reference layer structure. The spin transfer torque magnetic junction includes conductive base and top electrodes, and a current polarizing structure that has magnetic anisotropy parallel to the substrate plane. In certain embodiments, the current polarizing structure may also include a non-magnetic spacer layer (e.g. MgO, copper, etc).
1. A spin transfer torque magnetic junction comprising:
an electrically conductive base electrode layer defining a substrate plane;
a magnetic reference layer structure disposed on the base electrode layer and having magnetic anisotropy perpendicular to the substrate plane;
an insulative barrier layer disposed on the laminated magnetic reference layer structure;
a laminated magnetic free layer disposed on the insulative barrier layer and having magnetic anisotropy perpendicular to the substrate plane,
a current polarizing structure disposed on the laminated magnetic free layer and having magnetic anisotropy parallel to the substrate plane;
an electrically conductive top electrode layer disposed on the current polarizing structure;
wherein the laminated magnetic free layer comprises at least three sublayers of CoFeB, each CoFeB sublayer having a thickness in the range of 6 Angstroms to 16 Angstroms and being separated from an adjacent CoFeB sublayer by one of a plurality of tantalum dusting layers.
2. The spin transfer torque magnetic junction of claim 1 wherein the laminated magnetic free layer comprises no more than four sublayers of CoFeB.
3. The spin transfer torque magnetic junction of claim 1 wherein each of the plurality of tantalum dusting layers has a thickness in the range of 1 Angstroms to 7 Angstroms.
4. The spin transfer torque magnetic junction of claim 1 wherein the current polarizing structure comprises a CoPd layer that is adjacent to the top electrode layer, a CoFeB polarizing layer having a thickness greater than 20 Angstroms, and a MgO spacer layer that is adjacent to the laminated magnetic free layer and that has a thickness in the range of 2 to 8 Angstroms.
5. The spin transfer torque magnetic junction of claim 1 wherein the magnetic reference layer structure comprises a pinned layer comprising CoFeB that is disposed adjacent the insulative barrier layer, and a pair of antiferromagnetically coupled pinning layers, each having magnetic anisotropy perpendicular to the substrate plane.
6. The spin transfer torque magnetic junction of claim 5 wherein the magnetic reference layer structure further comprises an outer layer comprising an alloy of manganese that is disposed adjacent to the base electrode layer.
7. The spin transfer torque magnetic junction of claim 1 wherein the insulative barrier layer comprises MgO having a thickness in the range of 8 Angstroms to 20 Angstroms.
8. A spin transfer torque magnetic junction comprising:
an electrically conductive base electrode layer defining a substrate plane;
a current polarizing structure disposed on the base electrode layer and having magnetic anisotropy parallel to the substrate plane;
a laminated magnetic free layer disposed on the current polarizing structure and having magnetic anisotropy perpendicular to the substrate plane;
an insulative barrier layer disposed on the laminated magnetic free layer;
a magnetic reference layer structure disposed on the insulative barrier layer and having magnetic anisotropy perpendicular to the substrate plane;
an electrically conductive top electrode disposed on the magnetic reference layer structure;
wherein the laminated magnetic free layer comprises at least three sublayers of CoFeB, each CoFeB sublayer having a thickness in the range of 6 Angstroms to 16 Angstroms and being separated from an adjacent CoFeB sublayer by one of a plurality of tantalum dusting layers.
9. The spin transfer torque magnetic junction of claim 8 wherein each of the plurality of tantalum dusting layers has a thickness in the range of 1 Angstroms to 7 Angstroms.
10. The spin transfer torque magnetic junction of claim 8 wherein the current polarizing structure comprises a CoPd layer that is adjacent to the base electrode layer, a CoFeB polarizing layer having a thickness greater than 20 Angstroms, and a MgO spacer layer that is adjacent to the laminated magnetic free layer and that has a thickness in the range of 2 to 8 Angstroms.
11. The spin transfer torque magnetic junction of claim 8 wherein the magnetic reference layer structure comprises a pinned layer comprising CoFeB that is disposed adjacent the insulative barrier layer, and a pair of antiferromagnetically coupled pinning layers, each having magnetic anisotropy perpendicular to the substrate plane.
12. The spin transfer torque magnetic junction of claim 11 wherein the magnetic reference layer structure further comprises an outer layer comprising an alloy of manganese that is disposed adjacent to the top electrode layer.
13. The spin transfer torque magnetic junction of claim 11 wherein the insulative barrier layer comprises MgO having a thickness in the range of 8 Angstroms to 20 Angstroms.
14. The spin transfer torque magnetic junction of claim 11 wherein the laminated magnetic free layer comprises no more than four sublayers of CoFeB.
15. A spin transfer torque magnetic junction comprising:
an electrically conductive base electrode defining a substrate plane;
a magnetic reference layer structure disposed on the base electrode and having magnetic anisotropy perpendicular to the substrate plane;
an insulative barrier layer disposed on the laminated magnetic reference layer;
a laminated magnetic free layer disposed on the insulative barrier layer and having magnetic anisotropy perpendicular to the substrate plane;
a current polarizing structure disposed on the laminated magnetic free layer and having magnetic anisotropy parallel to the substrate plane;
an electrically conductive top electrode disposed on the current polarizing structure;
wherein the laminated magnetic free layer comprises first and third sublayers of CoFeB, each having a CoFeB sublayer thickness in the range of 6 Angstroms to 16 Angstroms, and a second sublayer comprising a ferromagnetic material selected form the group consisting of CoPt, FePt, and CoPd, and having a second sublayer thickness in the range of 10 Angstroms to 30 Angstroms; and
wherein the first and second sublayers are separated by a first tantalum dusting layer, and the second and third sublayers are separated by a second tantalum dusting layer.
16. The spin transfer torque magnetic junction of claim 15 wherein each of the first and second tantalum dusting layers has a thickness in the range of 1 Angstroms to 7 Angstroms.
17. The spin transfer torque magnetic junction of claim 15 wherein the current polarizing structure comprises a CoPd layer that is adjacent to the top electrode layer, a CoFeB polarizing layer having a thickness greater than 20 Angstroms, and a MgO spacer layer that is adjacent to the laminated magnetic free layer and that has a thickness in the range of 2 to 8 Angstroms.
18. The spin transfer torque magnetic junction of claim 15 wherein the magnetic reference layer structure comprises a pinned layer comprising CoFeB that is disposed adjacent the insulative barrier layer, and a pair of antiferromagnetically coupled pinning layers, each having magnetic anisotropy perpendicular to the substrate plane.
19. The spin transfer torque magnetic junction of claim 18 wherein the magnetic reference layer structure further comprises an outer layer comprising an alloy of manganese that is disposed adjacent to the base electrode layer.
20. The spin transfer torque magnetic junction of claim 15 wherein the insulative barrier layer comprises MgO having a thickness in the range of 8 Angstroms to 20 Angstroms.