MAGNETIC TUNNEL JUNCTION STRUCTURE FOR MRAM DEVICE
A magnetic tunnel junction stack is provided that includes nonmagnetic spacer layers between the free layer and the polarizer layer formed from magnesium oxide and tantalum nitride materials that balance the spin torques acting on the free layer. The design provided enables a deterministic final state for the storage layer and significantly improves the tunneling magnetoresistance value and switching characteristics of the magnetic tunnel junction for MRAM applications.
1 . A memory array comprising:
at least one bit cell including:
an antiferromagnetic structure including a reference layer;
a barrier layer disposed over the reference layer;
a free layer having a free layer magnetization direction disposed on the barrier layer, the reference layer, the barrier layer and the free layer forming a magnetic tunnel junction;
a nonmagnetic spacer layer disposed on the free layer;
a polarizer disposed on the magnetic spacer layer, the polarizer layer having a magnetization direction that is perpendicular to the free layer magnetization direction,
wherein the nonmagnetic spacer layer is disposed between the free layer of the magnetic tunnel junction and the polarizer, the nonmagnetic spacer layer comprising a thin layer of magnesium oxide (MgO) on the free layer and a layer of tantalum nitride (TaN) capping material on the thin layer of MgO.
2 . The magnetic device according to claim 1 , wherein the thin layer of magnesium oxide comprises a thickness of approximately 0.3 nanometers.
3 . The magnetic device according to claim 2 , wherein the layer of tantalum nitride capping material comprises a thickness between 1.0 and 5.0 nanometers.
4 . The magnetic device according to claim 3 , wherein the layer of tantalum nitride capping material comprises a thickness of approximately 1.0 nanometers.
5 . The magnetic device according to claim 3 , wherein the layer of tantalum nitride capping material comprises a thickness of approximately 5.0 nanometers.
6 . The magnetic device according to claim 1 , wherein the magnetic device is an orthogonal spin torque structure.
7 . The magnetic device according to claim 1 , wherein the reference layer and the free layer each comprise a CoFeB thin film layer having a thickness of approximately 2.3 nanometers and 1.85 nanometers, respectively.
8 . The magnetic device according to claim 1 , wherein the nonmagnetic spacer layer further comprises a copper layer having a thickness of approximately 5.0 nanometers.
9 . The magnetic device according to claim 8 , wherein the thickness of the layer of tantalum nitride capping material is approximately 1.0 nanometers.
10 . The magnetic device according to claim 8 , wherein the thickness of the layer of tantalum nitride capping material is approximately 3.0 nanometers.
11 . The magnetic device according to claim 8 , wherein the thickness of the layer of tantalum nitride capping material is approximately 5.0 nanometers.
12 . The magnetic device according to claim 2 , wherein the nonmagnetic spacer layer further comprises a copper layer having a thickness of approximately 10 nanometers, and wherein the layer of tantalum nitride capping material has a thickness of approximately 1.0 nanometers.