Magnetic tunnel junction (MTJ) memory element having tri-layer perpendicular reference layer

Patent metadata

Field	Value
Publication number	US-9608038-B2
Application number	US-201615174754-A
Country	US
Kind code	B2
Filing date	Jun 6, 2016
Priority date	Dec 10, 2010
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

The present invention is directed to an STT-MRAM device comprising a plurality of memory elements. Each of the memory elements includes an MTJ structure in between a seed layer and a cap layer. The MTJ structure includes a magnetic free layer structure and a magnetic reference layer structure with an insulating tunnel junction layer interposed therebetween; and a magnetic fixed layer separated from the magnetic reference layer structure by an anti-ferromagnetic coupling layer. The magnetic reference layer structure includes a first magnetic reference layer formed adjacent to the insulating tunnel junction layer and a second magnetic reference layer separated from the first magnetic reference layer by an intermediate magnetic reference layer. The first, second, and intermediate magnetic reference layers have a first invariable magnetization direction substantially perpendicular to layer planes thereof. The magnetic fixed layer has a second invariable magnetization direction that is opposite to the first invariable magnetization direction.

First claim

What is claimed is:

1. A spin transfer torque magnetic random access memory (STT-MRAM) device comprising a plurality of memory elements, each of said memory elements including a magnetic tunnel junction (MTJ) structure in between a non-magnetic seed layer and a non-magnetic cap layer, said MTJ structure comprising:
a magnetic free layer structure and a magnetic reference layer structure with an insulating tunnel junction layer interposed therebetween; and
a magnetic fixed layer separated from said magnetic reference layer structure by an anti-ferromagnetic coupling layer,
wherein said magnetic reference layer structure includes a first magnetic reference layer formed adjacent to said insulating tunnel junction layer and a second magnetic reference layer separated from said first magnetic reference layer by an intermediate magnetic reference layer, said first, second, and intermediate magnetic reference layers having a first invariable magnetization direction substantially perpendicular to layer planes thereof, said magnetic fixed layer has a second invariable magnetization direction that is substantially perpendicular to a layer plane thereof and is opposite to said first invariable magnetization direction, said magnetic free layer structure includes one or more magnetic free layers.

2. The STT-MRAM device according to claim 1 , wherein said intermediate magnetic reference layer is made of a material comprising cobalt, iron, and tantalum.

3. The STT-MRAM device according to claim 1 , wherein said intermediate magnetic reference layer is made of a material comprising cobalt, iron, and molybdenum.

4. The STT-MRAM device according to claim 1 , wherein said intermediate magnetic reference layer is made of a material comprising cobalt, iron, and tungsten.

5. The STT-MRAM device according to claim 1 , wherein said intermediate magnetic reference layer is made of a material comprising cobalt, iron, and niobium.

6. The STT-MRAM device according to claim 1 , wherein said intermediate magnetic reference layer is made of a material comprising cobalt, iron, and hafnium.

7. The STT-MRAM device according to claim 1 , wherein said intermediate magnetic reference layer is made of a material comprising cobalt, iron, and zirconium.

8. The STT-MRAM device according to claim 1 , wherein said second magnetic reference layer is made of cobalt, or iron, or an alloy of cobalt and iron.

9. The STT-MRAM device according to claim 1 , wherein said first magnetic reference layer is made of a material comprising cobalt, iron, and boron.

10. The STT-MRAM device according to claim 1 , wherein said magnetic free layer structure includes a first magnetic free layer formed adjacent to said insulating tunnel junction layer and a second magnetic free layer separated from said first magnetic free layer by a non-magnetic perpendicular enhancement layer, said first and said second magnetic free layers having respectively a first and a second variable magnetization directions that are substantially perpendicular to layer planes thereof and are parallel to each other.

11. The STT-MRAM device according to claim 10 , wherein said non-magnetic perpendicular enhancement layer is made of magnesium oxide.

12. The STT-MRAM device according to claim 10 , wherein each of said first magnetic reference layer and said first magnetic free layer is made of a material comprising cobalt, iron, and boron.

13. The STT-MRAM device according to claim 1 , wherein said magnetic free layer structure includes a magnetic free layer formed adjacent to said insulating tunnel junction layer, said magnetic free layer having a variable magnetization direction substantially perpendicular to a layer plane thereof.

14. The STT-MRAM device according to claim 13 , wherein each of said first magnetic reference layer and said magnetic free layer is made of a material comprising cobalt, iron, and boron.

15. The STT-MRAM device according to claim 13 , wherein said magnetic free layer structure further includes a magnetic dead layer separated from said magnetic free layer by a non-magnetic perpendicular enhancement layer, said magnetic dead layer comprising at least one ferromagnetic element.

16. The STT-MRAM device according to claim 15 , wherein said magnetic dead layer is made of a material comprising cobalt, iron, and boron.

17. The STT-MRAM device according to claim 15 , wherein said non-magnetic perpendicular enhancement layer is made of magnesium oxide.

18. The STT-MRAM device according to claim 1 , wherein said magnetic fixed layer has a multilayer structure formed by interleaving layers of a first material with layers of a second material, at least one of said first and second materials being magnetic.

19. The STT-MRAM device according to claim 18 , wherein said first material is cobalt or a material comprising cobalt and iron.

20. The STT-MRAM device according to claim 18 , wherein said second material is nickel, or platinum, or palladium.

Assignees

• Avalanche Technology Inc

Inventors

• Wang Zihui
• Zhou Yuchen
• Gan Huadong
• Huai Yiming

Classifications

• H01F10/3286 Primary

  Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy · CPC title

• H01L29/66984

  Electricity · mapped topic

• H01F10/329

  Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect · CPC title

• H01L43/02

  Electricity · mapped topic

• H01F41/302

  for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices (spin-exchange-coupled multilayers H01F10/32) · CPC title