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

• US 9,608,038 B2
• Filed: 06/06/2016
• Issued: 03/28/2017
• Est. Priority Date: 12/10/2010
• Status: Active Grant

• Current Assignee: Avalanche Technology Incorporated
• Original Assignee: Avalanche Technology Incorporated
• Inventors: Wang, Zihui, Zhou, Yuchen, Gan, Huadong, Huai, Yiming
• Primary Examiner(s): Henry, Caleb
• Assistant Examiner(s): AMER, MOUNIR S
• Application Number:
  US15/174,754
• Publication Number:
  US 20160284762A1
• Time in Patent Office: 295 Days
• US Class Current: 1/1
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/14 containing iron or nickel H01F10/126 , H01F10/13, H01F10/16 take precedence
• CPC Class Codes: H01F 10/16 containing cobalt H01F10/126 , H01F10/13 take precedence
• CPC Class Codes: H01F 10/3222 Exchange coupled hard/soft multilayers, e.g. CoPt/Co or NiFe/CoSm nanocomposite spring magnets H01F1/0579
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3286 Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
• CPC Class Codes: H01F 10/329 Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect
• CPC Class Codes: H01F 41/302 for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices spin-exchange-coupled multilayers H01F10/32
• CPC Class Codes: H01F 41/307 insulating or semiconductive spacer
• CPC Class Codes: H01L 29/66984 Devices using spin polarized carriers
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials

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.

Claims

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.