PRECESSIONAL SPIN CURRENT STRUCTURE FOR MRAM

• US 20180248110A1
• Filed: 02/28/2017
• Published: 08/30/2018
• Est. Priority Date: 02/28/2017
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Spin Transfer Technologies, Inc.
• Inventors: Kardasz, Bartlomiej Adam, PINARBASI, Mustafa Michael
• Granted Patent: US 10,665,777 B2
• Time in Patent Office: Days
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A magnetoresistive random-access memory (MRAM) is disclosed. MRAM device has a magnetic tunnel junction stack having a significantly improved performance of the free layer in the magnetic tunnel junction structure. The MRAM device utilizes a precessional spin current (PSC) magnetic structure in conjunction with a perpendicular MTJ where the in-plane magnetization direction of the PSC magnetic layer is free to rotate. The precessional spin current magnetic layer a first and second precessional spin current ferromagnetic layer separated by a nonmagnetic precessional spin current insertion layer.

Claims

1. A magnetic device, comprising

a first synthetic antiferromagnetic structure in a first plane, the first synthetic antiferromagnetic structure including a magnetic reference layer, the magnetic reference layer having a magnetization vector that is perpendicular to the first plane and having a fixed magnetization direction;

a nonmagnetic tunnel barrier layer in a second plane and disposed over the magnetic reference layer;

a free magnetic layer in a third plane and disposed over the nonmagnetic tunnel barrier layer, the free magnetic layer having a magnetization vector that is perpendicular to the third plane and having a magnetization direction that can precess from a first magnetization direction to a second magnetization direction, the magnetic reference layer, the nonmagnetic tunnel barrier layer and the free magnetic layer forming a magnetic tunnel junction;

a nonmagnetic spacer layer in a fourth plane and disposed over the free magnetic layer, the magnetic coupling layer comprising MgO;

a precessional spin current magnetic structure in a fifth plane that is physically separated from the free magnetic layer and coupled to the free magnetic layer by the nonmagnetic spacer layer, the precessional spin current magnetic structure having a magnetization vector with a magnetization direction in the fifth plane which can freely rotate in any magnetic direction in the fifth plane, the precessional spin current magnetic structure comprising a first precessional spin current ferromagnetic layer, a nonmagnetic precessional spin current insertion layer and a second precessional spin current ferromagnetic layer, the first precessional spin current ferromagnetic layer being disposed over the nonmagnetic spacer layer, the nonmagnetic precessional spin current insertion layer being disposed over the first precessional spin current ferromagnetic layer, and the second precessional spin current ferromagnetic layer being disposed over the nonmagnetic precessional spin current insertion layer; and

a capping layer in a sixth plane and disposed over the precessional spin current magnetic structure;

wherein electrons of an electrical current passing through the precessional spin current magnetic structure are aligned in the magnetic direction of the precessional spin current magnetic layer and injected into the nonmagnetic spacer, the free magnetic layer, the nonmagnetic tunnel barrier layer, and the magnetic reference layer, and wherein the magnetization direction of the precessional spin current magnetic structure precesses, thereby causing spin transfer torque to assist switching of the magnetization vector of the free magnetic layer.

2. The magnetic device of claim 1 wherein the nonmagnetic precessional spin current insertion layer is constructed of a material having a spin diffusion length exceeding two (2) nanometers.

3. The magnetic device of claim 1 wherein the nonmagnetic precessional spin current insertion layer is constructed of a thin film of Ru.

4. The magnetic device of claim 3 wherein the thin film of Ru has a thickness of at least one nanometer.

5. The magnetic device of claim 3 wherein the thin film of Ru has a thickness of 1.5 nanometers.

6. The magnetic structure of claim 1, wherein the first precessional spin current ferromagnetic layer comprises a thin film of Fe, the nonmagnetic precessional spin current insertion layer comprises a material with a long spin diffusion length, and the second precessional spin current ferromagnetic layer comprises a thin film of CoFeB.

7. The magnetic structure of claim 6, wherein the thin film of Fe has a thickness of 0.4 nanometers.

8. The magnetic structure of claim 6, wherein the thin film of Fe has a thickness of 0.6 nanometers.

9. The magnetic structure of claim 6 wherein the thin film of CoFeB is comprised of forty percent Co, forty percent Fe and twenty percent B.

10. The magnetic structure of claim 9 wherein the thin film of CoFeB has a thickness of 1.7 nanometers.

11. The magnetic structure of claim 9 wherein the thin film of CoFeB has a thickness of 1.85 nanometers.

12. The magnetic structure of claim 6, wherein the material with a long spin diffusion length is selected from the group consisting of Ru, Cu, Ag, Au, Mg and Al.

13. The magnetic structure of claim 1 wherein the free magnetic layer has an effective magnetic anisotropy such that its easy axis magnetization axis points away from the perpendicular direction and forms an angle with respect to perpendicular plane.

14. A method of manufacturing a magnetic device over a substrate, comprising:

depositing a first synthetic antiferromagnetic structure over the substrate, the first synthetic antiferromagnetic structure being in a first plane, the first synthetic antiferromagnetic structure having a magnetization vector that is perpendicular to the first plane and having a fixed magnetization direction;

depositing an exchange coupling layer over the first synthetic antiferromagnetic structure, the exchange coupling layer being in a second plane;

depositing a second synthetic antiferromagnetic structure over the substrate, the second synthetic antiferromagnetic structure being in a third plane, the second synthetic antiferromagnetic structure including a magnetic reference layer, the second synthetic antiferromagnetic structure and the magnetic reference layer having a magnetization vector that is perpendicular to the third plane and having a fixed magnetization direction;

depositing a nonmagnetic tunnel barrier layer in a fourth plane, the nonmagnetic tunnel barrier disposed over the magnetic reference layer;

depositing a free magnetic layer in a fifth plane, the free magnetic layer disposed over the nonmagnetic tunnel barrier layer and having a magnetization vector that is perpendicular to the fifth plane, the free magnetic layer having a magnetization direction that can precess from a first magnetization direction to a second magnetization direction, wherein the magnetic reference layer, the nonmagnetic tunnel barrier layer and the free magnetic layer form a magnetic tunnel junction;

depositing a nonmagnetic spacer layer in a sixth plane and disposed over the free magnetic layer;

depositing a precessional spin current magnetic structure in a seventh plane that is physically separated from the free magnetic layer and coupled to the free magnetic layer by the nonmagnetic spacer layer, the precessional spin current magnetic structure having a magnetization vector with a magnetization direction in the seventh plane which can freely rotate in any magnetic direction in the seventh plane, wherein depositing the precessional spin current magnetic structure comprises;

depositing a first precessional spin current ferromagnetic layer, the first precessional spin current ferromagnetic layer being disposed over the nonmagnetic spacer layer,

depositing a nonmagnetic precessional spin current insertion layer, the nonmagnetic precessional spin current insertion layer being disposed over the first precessional spin current ferromagnetic layer, and

depositing a second precessional spin current ferromagnetic layer, the second precessional spin current ferromagnetic layer being disposed over the nonmagnetic precessional spin current insertion layer;

depositing a capping layer in an eighth plane, the capping layer being disposed over the precessional spin current magnetic layer;

annealing the magnetic device at a temperature of 400 degrees Celsius or greater.

15. The method of claim 14, wherein the step of depositing the free magnetic layer includes depositing a material having magnetocrystalline anisotropy such that the free magnetic layer has an effective magnetic anisotropy where its easy axis magnetization axis points away from the perpendicular direction and forms an angle with respect to perpendicular plane.

16. The method of claim 14 wherein the substrate has complementary metal oxide semiconductor circuitry fabricated thereon.