Magnetoresistive MTJ stack having an unpinned, fixed synthetic anti-ferromagnetic structure

Patent metadata

Field	Value
Publication number	US-9793468-B2
Application number	US-201615199862-A
Country	US
Kind code	B2
Filing date	Jun 30, 2016
Priority date	May 31, 2006
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

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 magnetoresistive magnetic tunnel junction (MTJ) stack comprising:
a free magnetic region having one or more ferromagnetic materials;
a fixed magnetic region consisting essentially of an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure, wherein the unpinned, fixed SAF structure comprises:
a first layer of ferromagnetic materials, wherein the first layer of ferromagnetic materials includes cobalt, iron and boron,
a multi-layer region including a plurality of layers, wherein each layer of the plurality of layers of the multi-layer region includes one or more ferromagnetic materials, and
an anti-ferromagnetic coupling layer disposed between the first layer of ferromagnetic materials and the multi-layer region; and

a dielectric layer disposed (i) between the free magnetic region and the fixed magnetic region and (ii) on the first layer of ferromagnetic materials.

2. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 1 wherein more than one layer of the plurality of layers of the multi-layer region includes cobalt.

3. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 1 wherein more than one layer of the plurality of layers of the multi-layer region includes a cobalt alloy.

4. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 1 wherein the first layer of ferromagnetic materials is a cobalt-iron-boron alloy having an amorphous crystalline structure.

5. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 1 wherein the free magnetic region has a circular shape.

6. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 1 wherein the free magnetic region includes a synthetic anti-ferromagnetic (SAF) structure.

7. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 6 wherein the synthetic anti-ferromagnetic (SAF) structure of the free magnetic region is a tri-layer structure.

8. A magnetoresistive magnetic tunnel junction (MTJ) stack comprising:
a free magnetic region having a circular shape;
an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure, wherein the unpinned, fixed SAF structure comprises:
a first layer of one or more ferromagnetic materials, wherein the first layer of ferromagnetic materials includes cobalt, iron and boron,
a second layer of one or more ferromagnetic materials wherein the one or more ferromagnetic materials of the second layer includes cobalt,
a third layer of one or more ferromagnetic materials wherein the one or more ferromagnetic materials of the third layer includes cobalt, and
an anti-ferromagnetic coupling layer, wherein:
the anti-ferromagnetic coupling layer is disposed between the first and second layers, and
the third layer is disposed between the second layer and the anti-ferromagnetic coupling layer; and

a dielectric layer disposed (i) between the free magnetic region and the fixed magnetic region and (ii) on the first layer of ferromagnetic materials.

9. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 8 wherein the third layer of one or more ferromagnetic materials is an alloy including cobalt and iron.

10. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 8 wherein the second layer of one or more ferromagnetic materials includes a cobalt-iron alloy.

11. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 8 wherein the first layer of ferromagnetic materials is a cobalt-iron-boron alloy having an amorphous crystalline structure.

12. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 8 wherein the free magnetic region includes a synthetic anti-ferromagnetic (SAF) structure.

13. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 12 wherein the synthetic anti-ferromagnetic (SAF) structure of the free magnetic region includes a tri-layer structure.

14. A magnetoresistive magnetic tunnel junction (MTJ) stack comprising:
a free magnetic region having at least one layer of one or more ferromagnetic materials;
a fixed magnetic region consisting essentially of an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure, wherein the unpinned, fixed SAF structure comprises:
a first layer of one or more ferromagnetic materials, wherein the one or more ferromagnetic materials of the first layer includes cobalt,
a multi-layer region including a plurality of layers of ferromagnetic materials, wherein the plurality of layers of ferromagnetic materials includes a layer of one or more ferromagnetic materials including cobalt,
an anti-ferromagnetic coupling layer disposed between the first layer of one or more ferromagnetic materials and the multi-layer region; and

a dielectric layer disposed (i) between the free magnetic region and the fixed magnetic region and (ii) on the first layer of one or more ferromagnetic materials.

15. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 14 wherein the layer of one or more ferromagnetic materials of the plurality of layers of ferromagnetic materials of the multi-layer region is an alloy including cobalt and iron.

16. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 14 wherein the first layer of one or more ferromagnetic materials includes cobalt, iron and boron.

17. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 14 wherein the free magnetic region includes a free synthetic anti-ferromagnetic (SAF) structure.

18. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 17 wherein the free synthetic anti-ferromagnetic (SAF) structure of the free magnetic region includes a tri-layer structure.

19. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 14 wherein the free magnetic region has a circular shape.

20. The magnetoresistive magnetic tunnel junction (MTJ) stack of claim 14 wherein:
the free magnetic region has a circular shape,
wherein the first layer of one or more ferromagnetic materials includes cobalt, iron and boron, and
the dielectric layer is disposed on the first layer of one or more ferromagnetic materials of the fixed magnetic region.

Assignees

• Everspin Technologies Inc

Inventors

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

Classifications

• H01L43/08 Primary

  Electricity · mapped topic

• H01L43/10

  Electricity · mapped topic

• G11C11/161 Primary

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

• H01L27/222

  Electricity · mapped topic

• H01L43/02

  Electricity · mapped topic