Three-Dimensional Magnetic Memory Devices with Buffer Layers

• US 20190207094A1
• Filed: 08/14/2018
• Published: 07/04/2019
• Est. Priority Date: 12/28/2017
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Spin Transfer Technologies
• Inventors: Gajek, Marcin, Tzoufras, Michail
• Granted Patent: US 10,693,056 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: H10B 61/22 of the field-effect transistor [FET] type
• 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
• CPC Class Codes: H10N 52/01 Manufacture or treatment
• CPC Class Codes: H10N 52/80 Constructional details

Abstract

A magnetic memory device is provided. The magnetic memory device includes: (i) a cylindrical core, (ii) a metallic buffer layer that surrounds the cylindrical core, (iii) a first ferromagnetic layer that surrounds the metallic buffer layer, (iv) a barrier layer that surrounds the first ferromagnetic layer, and (v) a second ferromagnetic layer that surrounds the barrier layer. The cylindrical core, the metallic buffer layer, the first ferromagnetic layer, the barrier layer, and the second ferromagnetic layer collectively form a magnetic tunnel junction.

Claims

1. A magnetic memory device comprising:

a cylindrical core;

a metallic buffer layer that surrounds the cylindrical core;

a first ferromagnetic layer that surrounds the metallic buffer layer;

a barrier layer that surrounds the first ferromagnetic layer; and

a second ferromagnetic layer that surrounds the barrier layer, wherein the cylindrical core, the metallic buffer layer, the first ferromagnetic layer, the barrier layer, and the second ferromagnetic layer collectively form a magnetic tunnel junction.

2. The magnetic memory device of claim 1, wherein:

a magnetization of the first ferromagnetic layer parallels an interface of the metallic buffer layer and the first ferromagnetic layer; and

the metallic buffer layer reduces an interfacial anisotropy contribution, resulting from the interface between the metallic buffer layer and the first ferromagnetic layer, to an anisotropy of the first ferromagnetic layer, the interfacial anisotropy being in a direction that is perpendicular to the magnetization of the first ferromagnetic layer.

3. The magnetic memory device of claim 2, wherein the interfacial anisotropy is magnetic anisotropy.

4. The magnetic memory device of claim 1, wherein:

when the metallic buffer layer is a first material, the first ferromagnetic layer has a first thermal stability; and

when the metallic buffer layer is a second material different from the first material, the first ferromagnetic layer has a second thermal stability greater than the first thermal stability.

5. The magnetic memory device of claim 4, wherein the second material is selected from the group consisting of:

aluminum, magnesium, ruthenium, and rhenium.

6. The magnetic memory device of claim 1, wherein:

the first ferromagnetic layer has a first set of characteristics; and

the second ferromagnetic layer has a second set of characteristics that at least partially differ from the first set of characteristics.

7. The magnetic memory device of claim 6, wherein a magnetic ground state of the first and second ferromagnetic layers is based, at least in part, on characteristics of the first and second ferromagnetic layers, respectively.

8. The magnetic memory device of claim 7, wherein the first and second sets of characteristics include:

(i) thicknesses of the first and second ferromagnetic layers and (ii) heights of the first and second ferromagnetic layers, respectively.

9. The magnetic memory device of claim 7, wherein the magnetic ground state is one of an out-of-plane ground state or a vortex ground state.

10. The magnetic memory device of claim 7, wherein the magnetic ground state of the first and second ferromagnetic layers is further based on characteristics of the cylindrical core.

11. The magnetic memory device of claim 10, wherein the characteristics of the cylindrical core include:

(i) a radius of the cylindrical core and (ii) a height of the cylindrical core.

12. The magnetic memory device of claim 1, wherein:

the first ferromagnetic layer is a storage layer; and

the second ferromagnetic layer is a reference layer.

13. The magnetic memory device of claim 1, wherein:

the first ferromagnetic layer is a reference layer; and

the second ferromagnetic layer is a storage layer.

14. The magnetic memory device of claim 1, wherein:

the cylindrical core is a non-magnetic metal; and

the cylindrical core is configured to receive a current.

15. The magnetic memory device of claim 14, wherein:

the received current flows radially through the metallic buffer layer, the first ferromagnetic layer, and the barrier layer towards the second ferromagnetic layer; and

radial flow of the current through the barrier layer and the second ferromagnetic layer imparts a torque at least on a magnetization of the first ferromagnetic layer.

16. The magnetic memory device of claim 15, wherein the magnetization of the first ferromagnetic layer changes from a first direction to a second direction when the current satisfies a threshold.

17. The magnetic memory device of claim 16, wherein:

the first direction is a first chirality; and

the second direction is a second chirality opposite to the first chirality.

18. The magnetic memory device of claim 1, wherein the barrier layer insulates the first ferromagnetic layer from the second ferromagnetic layer.

19. The magnetic memory device of claim 1, wherein the cylindrical core, the metallic buffer layer, the first ferromagnetic layer, the barrier layer, and the second ferromagnetic layer are coaxial with one another.

20. The magnetic memory device of claim 1, further comprising:

a first terminal lead connected to the cylindrical core; and

a second terminal lead connected to the second ferromagnetic layer.