MAGNETIC TUNNEL JUNCTION STRUCTURE FOR MRAM DEVICE

• US 20160087193A1
• Filed: 09/22/2014
• Published: 03/24/2016
• Est. Priority Date: 09/22/2014
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Spin Transfer Technologies, Inc.
• Inventors: Pinarbasi, Mustafa, Kardasz, Bartek
• Granted Patent: US 9,337,412 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/329 Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials
• CPC Class Codes: Y10S 977/935 Spin dependent tunnel, SDT, junction, e.g. tunneling magnetoresistance, TMR

Abstract

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.

Claims

1. A magnetic device, comprising

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; and

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, the.

7. The magnetic device according to claim 1, wherein the magnetic device is an orthogonal spin torque structure.

8. 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.

9. 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.

10. The magnetic device according to claim 9, wherein the thickness of the layer of tantalum nitride capping material is approximately 1.0 nanometers.

11. The magnetic device according to claim 9, wherein the thickness of the layer of tantalum nitride capping material is approximately 3.0 nanometers.

12. The magnetic device according to claim 9, wherein the thickness of the layer of tantalum nitride capping material is approximately 5.0 nanometers.

2. (canceled)

3. The magnetic device according to claim 2, wherein the thin layer of magnesium oxide comprises a thickness of approximately 0.3 nanometers.

4. The magnetic device according to claim 3, wherein the layer of tantalum nitride capping material comprises a thickness between 1.0 and 5.0 nanometers.

5. The magnetic device according to claim 4, wherein the layer of tantalum nitride capping material comprises a thickness of approximately 1.0 nanometers.

6. The magnetic device according to claim 4, wherein the layer of tantalum nitride capping material comprises a thickness of approximately 5.0 nanometers.

13. The magnetic device according to claim 3, 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.

14. A memory array comprising:

at least one bit cell including;

an antiferromagnetic structure including a reference layer;

a barrier layer disposed on the reference layer;

a free layer disposed on the barrier layer;

a nonmagnetic spacer layer disposed on the free layer, the nonmagnetic spacer including a layer of tantalum nitride capping material; and

a polarizer disposed on the nonmagnetic spacer.

15. The memory array according to claim 14, wherein the nonmagnetic spacer layer further comprises a layer of magnesium oxide having a thickness of approximately 0.3 nanometers.

16. The memory array according to claim 15, wherein the layer of tantalum nitride capping material comprises a thickness between 1.0 and 5.0 nanometers.

17. The memory array according to claim 14, wherein the at least one bit cell is an orthogonal spin torque structure.

18. The memory array according to claim 14, wherein the nonmagnetic spacer layer further comprises a copper layer having a thickness of approximately 5.0 nanometers.

19. The memory array according to claim 18, wherein the layer of tantalum nitride capping material comprises a thickness between 1.0 and 5.0 nanometers.

20. The memory array according to claim 15, 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.