HIGH ANNEALING TEMPERATURE PERPENDICULAR MAGNETIC ANISOTROPY STRUCTURE FOR MAGNETIC RANDOM ACCESS MEMORY

• US 20160315118A1
• Filed: 04/06/2016
• Published: 10/27/2016
• Est. Priority Date: 04/21/2015
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Spin Transfer Technologies, Inc.
• Inventors: PINARBASI, Mustafa Michael, HERNANDEZ, Jacob Anthony, KARDASZ, Bartlomiej Adam
• Granted Patent: US 10,468,590 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01F 10/3272 by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets
• CPC Class Codes: H01F 10/3286 Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
• CPC Class Codes: H01F 41/302 for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices spin-exchange-coupled multilayers H01F10/32
• 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 perpendicular synthetic antiferromagnetic (pSAF) structure and method of making such a structure is disclosed. The pSAF structure comprises a first high perpendicular Magnetic Anisotropy (PMA) multilayer and a second high PMA layer separated by a thin Ruthenium layer. Each PMA layer is comprised of a first cobalt layer and a second cobalt layer separated by a nickel/cobalt multilayer. After each of the first and second PMA layers and the Ruthenium exchange coupling layer are deposited, the resulting structure goes through a high temperature annealing step, which results in each of the first and second PMA layers having a perpendicular magnetic anisotropy.

Claims

1. A magnetic device, comprising

a PMA seed multilayer comprised of a first seed layer and a nickel seed layer, the Ni seed layer being disposed over the first seed layer;

a first magnetic perpendicular magnetic anisotropy (PMA) multilayer disposed over the PMA seed multilayer, the first magnetic PMA multilayer comprising a first cobalt (Co) layer and a second Co layer, where the first Co layer and the second Co layer are separated by a first nickel/cobalt (Ni/Co) multilayer, wherein the first magnetic PMA multilayer has been annealed at a high temperature and has a magnetic direction perpendicular to its plane;

a thin Ruthenium (Ru) antiferromagnetic interlayer exchange coupling layer disposed over the first magnetic PMA multilayer;

a second magnetic PMA multilayer disposed over the thin Ru antiferromagnetic interlayer exchange coupling layer, the second magnetic PMA multilayer comprising a third Co layer and a fourth Co layer, where the third Co layer and the fourth Co layer are separated by a second nickel/cobalt (Ni/Co) multilayer, wherein the second magnetic PMA multilayer has been annealed at the high temperature and has a magnetic direction perpendicular to its plane;

wherein the first magnetic PMA multilayer, the thin Ru interlayer exchange coupling layer and the second magnetic PMA multilayer form a perpendicular synthetic antiferromagnet.

2. The magnetic device of claim 1 wherein the first seed layer comprises alpha phase tantalum nitride.

3. The magnetic device of claim 2 where in the first seed layer has a thickness of five nanometers.

4. The magnetic device of claim 1 wherein the first seed layer comprises tantalum.

5. The magnetic device of claim 4 where in the first seed layer has a thickness of five nanometers.

6. The magnetic device of claim 1 wherein the high temperature is 350 degrees Celsius or higher.

7. The magnetic device of claim 1 wherein the first Co layer has a thickness of 0.3 nanometers, the second Co layer has a thickness of 0.18 nanometers.

8. The magnetic device of claim 7, wherein the first Ni/Co multilayer comprises a nickel layer having a thickness of 0.6 nanometers and a cobalt layer having a thickness of 0.2 nanometers.

9. The magnetic device of claim 8, wherein the first Ni/Co multilayer is repeated five times.

10. The magnetic device of claim 1, wherein the Ni seed layer of the PMA seed multilayer has a thickness ranging from 0.5 nanometers to 0.95 nanometers.

11. The magnetic device of claim 1, wherein the Ni seed layer of the PMA seed multilayer has a thickness of 0.93 nanometers.

12. The magnetic device of claim 1, wherein the thin Ruthenium (Ru) antiferromagnetic interlayer exchange coupling layer has a thickness of 0.85 nanometers.

13. The magnetic device of claim 1, wherein the first Co layer has a thickness of 0.3 nanometers, the second Co layer has a thickness of 0.18 nanometers, the third Co layer has a thickness of 0.18 nanometers, the fourth Co layer has a thickness of 0.18 nanometers.

14. The magnetic device of claim 13, wherein the first Ni/Co multilayer comprise a first Ni layer having a thickness of 0.6 nanometers and fifth Co layer having a thickness of 0.2 nanometers.

15. The magnetic device of claim 14 wherein the first Ni/Co multilayer comprises five Ni/Co multilayers.

16. The magnetic device of claim 13, wherein the second Ni/Co multilayer comprise a sixth Co layer having a thickness of 0.2 nanometers and second Ni layer having a thickness of 0.6 nanometers.

17. The magnetic device of claim 16 wherein the second Ni/Co multilayer comprises five Ni/Co multilayers.

18. The magnetic device of claim 1, further comprising:

a non-magnetic tunneling barrier layer over the second magnetic PMA multilayer;

a free magnetic layer over the non-magnetic tunneling barrier layer, the free magnetic layer having a magnetic direction that can precess between a first direction and a second direction, the non-magnetic tunneling barrier layer spatially separating the free magnetic layer from the second magnetic PMA multilayer; and

wherein the second magnetic PMA multilayer, the non-magnetic tunneling barrier layer, and the free magnetic layer form a magnetic tunnel junction.

19. A method of manufacturing a synthetic antiferromagnetic structure having a magnetic direction perpendicular to its plane, comprising:

depositing a PMA seed multilayer, wherein the depositing of a PMA seed multilayer step comprises;

depositing a first seed layer, and

depositing a nickel (Ni) seed layer over the first seed layer;

depositing a first magnetic perpendicular magnetic anisotropy (PMA) multilayer over the PMA seed multilayer, wherein the depositing of a first magnetic PMA multilayer step comprises;

depositing a first cobalt (Co) layer over the PMA seed multilayer;

depositing a first nickel/cobalt (Ni/Co) multilayer over the first Co layer; and

depositing a second Co layer over the first Ni/Co multilayer, wherein the second Co layer is separated from the first Co layer by the first Ni/Co multilayer;

depositing a thin Ruthenium (Ru) antiferromagnetic interlayer exchange coupling layer over the first magnetic PMA multilayer;

depositing a second magnetic PMA multilayer over the thin Ru antiferromagnetic interlayer exchange coupling layer, wherein the depositing of second magnetic PMA multilayer step comprises;

depositing a third Co layer over the thin Ru antiferromagnetic interlayer exchange coupling layer;

depositing a second Ni/Co multilayer over the third Co layer; and

depositing a fourth Co layer over the second Ni/Co multilayer, wherein the fourth Co layer is separated from the third Co layer by the second Ni/Co multilayer;

annealing at high temperature for a time sufficient to increase perpendicular magnetic anisotropy of the first magnetic PMA multilayer and second magnetic PMA multilayer such that the first magnetic PMA multilayer has a magnetic direction perpendicular to its plane and the second magnetic PMA multilayer has a magnetic direct perpendicular to its plane.

20. The method of claim 19, wherein the annealing step comprises annealing at 350 degrees Celsius or higher.

21. The method of claim 20, wherein the annealing step further comprises annealing for a period of at least two hours.

22. The method of claim 19, wherein the depositing a first magnetic PMA multilayer step is performed by dc magnetron sputtering.

23. The method of claim 19, wherein the depositing a second magnetic PMA multilayer step is performed by dc magnetron sputtering.

24. The method of claim 19, wherein the depositing a Ni seed layer over the first seed layer step comprises depositing the Ni seed layer such that the Ni seed layer has a thickness of at least 0.93 nanometers.

25. The method of claim 19, wherein the depositing a first seed layer step comprises depositing a layer of alpha phase tantalum nitride.

26. The method of claim 25, wherein the depositing a layer of alpha phase tantalum nitride step comprises depositing a layer of alpha phase tantalum nitride having a thickness of at least 0.5 nanometers.

27. The method of claim 19, wherein the depositing a thin Ru antiferromagnetic interlayer exchange coupling layer comprises depositing a layer of Ru having a thickness of 0.85 nanometers.

28. The method of claim 19, further comprising

depositing a non-magnetic tunneling barrier layer over the second magnetic PMA multilayer;

and

depositing a free magnetic layer over the non-magnetic tunneling barrier layer, the free magnetic layer having a magnetic direction that can precess between a first direction and a second direction, the non-magnetic tunneling barrier layer spatially separating the free magnetic layer from the second magnetic PMA multilayer, wherein the second magnetic PMA multilayer, the non-magnetic tunneling barrier layer, and the free magnetic layer form a magnetic tunnel junction.