Magnetoresistive stacks with an unpinned, fixed synthetic anti-ferromagnetic structure and methods of manufacturing thereof

Patent metadata

Field	Value
Publication number	US-11744161-B2
Application number	US-202017120959-A
Country	US
Kind code	B2
Filing date	Dec 14, 2020
Priority date	May 31, 2006
Publication date	Aug 29, 2023
Grant date	Aug 29, 2023

Abstract

A magnetoresistive magnetic tunnel junction (MTJ) stack includes a free magnetic region, a fixed magnetic region, and a dielectric layer positioned between the free magnetic region and the fixed magnetic region. In one aspect, the fixed magnetic region consists essentially of an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure which comprises (i) a first layer of one or more ferromagnetic materials, including cobalt, (ii) a multi-layer region including a plurality of layers of ferromagnetic materials, wherein the plurality of layers of ferromagnetic materials include a layer of one or more ferromagnetic materials including cobalt, and (iii) an anti-ferromagnetic coupling layer disposed between the first layer and the multi-layer region. The free magnetic region may include a circular shape, the one or more ferromagnetic materials of the first layer may include cobalt, iron and boron, and the dielectric layer may be disposed on the first layer.

First claim

What is claimed is:

1. A method of fabricating a synthetic anti-ferromagnetic (SAF) structure in a magnetic tunnel junction (MTJ) stack, comprising:
forming a free magnetic layer; and
forming a fixed magnetic region with a unpinned synthetic anti-ferromagnetic (SAF) structure, wherein forming the fixed magnetic region includes:
forming a first ferromagnetic layer, wherein the first ferromagnetic layer comprises cobalt, iron, and boron;
forming a second ferromagnetic layer, wherein the second ferromagnetic layer comprises cobalt, iron, and boron;
forming a coupling layer between the first ferromagnetic layer and the second ferromagnetic layer; and
forming a ferromagnetic insertion layer between the first ferromagnetic layer and the coupling layer.

2. The method of claim 1 , wherein the ferromagnetic insertion layer comprises cobalt and iron.

3. The method of claim 1 , wherein the coupling layer is anti-ferromagnetic.

4. The method of claim 1 , wherein the second ferromagnetic layer includes an alloy having a different boron concentration than the first ferromagnetic layer.

5. The method of claim 1 , wherein forming the ferromagnetic insertion layer includes forming the ferromagnetic insertion layer on the first ferromagnetic layer.

6. The method of claim 1 , wherein forming the coupling layer includes forming the coupling layer on the ferromagnetic insertion layer.

7. The method of claim 1 , wherein the second ferromagnetic layer has a different thickness than the first ferromagnetic layer.

8. A method of fabricating a fixed magnetic region in a magnetic tunnel junction (MTJ) stack, comprising:
forming a first ferromagnetic layer on a seed layer;
forming an insertion layer on the first ferromagnetic layer, the insertion layer comprising cobalt and iron;
forming a coupling layer on the insertion layer, the coupling layer providing anti-ferromagnetic coupling between the first ferromagnetic layer and a second ferromagnetic layer; and
forming the second ferromagnetic layer on the coupling layer, wherein the second ferromagnetic layer comprises cobalt and boron;
wherein a resultant fixed magnetic region is an unpinned synthetic anti-ferromagnetic (SAF) structure, and wherein the resultant fixed magnetic region is configured to be positioned adjacent to a free magnetic region to form the magnetic tunnel junction (MTJ) stack.

9. The method of claim 8 , wherein the first ferromagnetic layer comprises cobalt and iron.

10. The method of claim 9 , wherein the first ferromagnetic layer further comprises boron.

11. The method of claim 8 , wherein the insertion layer comprises cobalt and iron.

12. The method of claim 11 , wherein the first ferromagnetic layer comprises at least two or more of: cobalt, iron, and boron.

13. The method of claim 8 , wherein the first ferromagnetic layer includes an amorphous crystalline structure.

14. A method of fabricating a magnetic tunnel junction (MTJ) stack, comprising:
forming a free magnetic region;
forming a fixed magnetic region consisting of an unpinned synthetic anti-ferromagnetic (SAF) structure, wherein forming the fixed magnetic region includes:
forming a first layer including at least cobalt and iron, wherein the first layer is formed on a seed layer;
forming a second layer including at least cobalt and iron;
forming a coupling layer between the first layer and the second layer; and
forming an insertion layer between the first layer and the coupling layer; and

forming an intermediate region between the free magnetic region and the fixed magnetic region.

15. The method of claim 14 , wherein each of the first layer and the second layer further includes boron.

16. The method of claim 15 , wherein the second layer includes a different boron concentration than the first layer.

17. The method of claim 14 , wherein the coupling layer is anti-ferromagnetic.

18. The method of claim 14 , wherein the first layer has a thickness different than a thickness of the second layer.

19. The method of claim 14 , wherein the insertion layer comprises cobalt and iron.

20. The method of claim 1 , wherein forming the second ferromagnetic layer includes forming the second ferromagnetic layer on the coupling layer.

Assignees

• Everspin Technologies Inc

Inventors

• Pietambaram Srinivas V
• Akerman Bengt J
• Whig Renu
• Janesky Jason A
• Rizzo Nicholas D
• Slaughter Jon M

Classifications

• H10N50/85

  Materials of the active region · CPC title

• H10N50/10 Primary

  Magnetoresistive devices · CPC title

• G11C11/161 Primary

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title

• H10N50/80

  Constructional details · CPC title

• H10B61/00

  Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices · CPC title