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

Patent metadata

Field	Value
Publication number	US-10897008-B2
Application number	US-202016890215-A
Country	US
Kind code	B2
Filing date	Jun 2, 2020
Priority date	May 31, 2006
Publication date	Jan 19, 2021
Grant date	Jan 19, 2021

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 fixed magnetic region in a magnetic tunnel junction (MTJ) stack, comprising:
forming a first ferromagnetic layer including one or more of: cobalt, iron, and boron, wherein the first ferromagnetic layer is formed on a seed layer including tantalum;
forming a second ferromagnetic layer;
forming an anti-ferromagnetic coupling layer between the first ferromagnetic layer and the second ferromagnetic layer; and
forming a third ferromagnetic layer between the first ferromagnetic layer and the anti-ferromagnetic coupling layer,
wherein the resultant fixed magnetic region consists of a fixed synthetic anti-ferromagnetic (SAF) structure without a pinning layer.

2. The method of claim 1 , wherein the first ferromagnetic layer includes an alloy having cobalt, iron, and boron, and the third ferromagnetic layer includes an alloy having cobalt and iron.

3. The method of claim 2 , wherein the first ferromagnetic layer includes an amorphous crystalline structure.

4. The method of claim 2 , wherein the second ferromagnetic layer includes an alloy having cobalt, iron, and boron.

5. The method of claim 1 , wherein the first and second ferromagnetic layers each include an alloy having cobalt, iron, and boron, and the second ferromagnetic layer includes an alloy having a different boron concentration than the first ferromagnetic layer.

6. The method of claim 1 , wherein forming the third ferromagnetic layer includes forming the third ferromagnetic layer on the first ferromagnetic layer.

7. The method of claim 1 , wherein forming the first ferromagnetic layer includes forming the first ferromagnetic layer using a cobalt-boron alloy, and forming the second ferromagnetic layer includes forming the second ferromagnetic layer using a cobalt-boron alloy on the anti-ferromagnetic coupling layer.

8. The method of claim 1 , wherein forming the first and second ferromagnetic layers each include using a cobalt-boron alloy, and the second ferromagnetic layer includes an alloy having a different boron concentration than the first ferromagnetic layer.

9. The method of claim 1 , wherein forming the anti-ferromagnetic coupling layer includes forming the anti-ferromagnetic coupling layer on the third ferromagnetic layer.

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

11. A method of fabricating a fixed magnetic region in a magnetic tunnel junction (MTJ) stack, comprising:
forming a first layer including a cobalt-iron-boron alloy, wherein the first layer is formed on a seed layer including tantalum;
forming a second layer including a cobalt-iron-boron alloy;
forming a coupling layer between the first layer and the second layer; and
forming a third layer including a cobalt-iron alloy between the first layer and the coupling layer,
wherein the resultant fixed magnetic region consists of a fixed synthetic anti-ferromagnetic (SAF) structure without a pinning layer.

12. The method of claim 11 , wherein the second layer includes a different boron concentration than the first layer.

13. The method of claim 11 , wherein the second layer includes a different thickness than the first layer.

14. The method of claim 11 , wherein forming the third layer includes forming the third layer on the first layer.

15. The method of claim 14 , wherein forming the coupling layer includes forming the coupling layer on the third layer.

16. The method of claim 11 , wherein the first layer includes an amorphous crystalline structure.

17. 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, fixed synthetic anti-ferromagnetic (SAF) structure, wherein forming the fixed magnetic region includes:
forming a first layer including a cobalt-iron-boron alloy, wherein the first layer is formed on a seed layer including tantalum;
forming a second layer including a cobalt-iron-boron alloy;
forming a coupling layer between the first layer and the second layer; and
forming a third layer between the first layer and the coupling layer; and

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

18. The method of claim 17 , wherein the first layer includes an amorphous crystalline structure.

19. The method of claim 17 , wherein the second layer includes a different boron concentration that the first layer.

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

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

• G11C11/161 Primary

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

• H01L43/10

  Electricity · mapped topic

• H01L43/08 Primary

  Electricity · mapped topic

• H01L43/02

  Electricity · mapped topic