Granted Patent B2

US 9,166,146 · App. 14/166,813 · Granted Oct 20, 2015

Abstract

Claims (30)

1. A spin transfer torque magnetic random access memory (STT-MRAM) device including a plurality of memory elements, each of said plurality of memory elements comprising:

a magnetic reference layer with a first invariable magnetization direction substantially perpendicular to a layer plane thereof;

a magnetic free layer separated from said magnetic reference layer by an insulating tunnel junction layer, said magnetic free layer having a variable magnetization direction substantially perpendicular to a layer plane thereof;

a dielectric layer formed in contact with said magnetic free layer opposite said insulating tunnel junction layer; and

a first conductive layer formed in contact with said dielectric layer opposite said magnetic free layer.

2. The STT-MRAM device of claim 1 , wherein each of said plurality of memory elements further comprises a second conductive layer formed in contact with said magnetic reference layer opposite said insulating tunnel junction layer.

3. The STT-MRAM device of claim 1 , wherein said dielectric layer has a relative permittivity of greater than 10.

4. The STT-MRAM device of claim 1 , wherein said dielectric layer is formed of a ferroelectric material.

5. The STT-MRAM device of claim 1 , wherein said dielectric layer is formed of a material selected from the group consisting of lead titanate, lead zirconate titanate, lead lanthanum zirconate titanate, barium titanate, lithium niobate, and combinations thereof.

6. The STT-MRAM device of claim 1 , wherein said magnetic reference layer and said magnetic free layer each is formed of an alloy comprising cobalt, iron, and boron.

7. The STT-MRAM device of claim 1 , wherein at least one of said magnetic reference layer and said magnetic free layer has a multilayer structure formed by interleaving two different types of materials with at least one of said two different types being magnetic.

8. The STT-MRAM device of claim 1 , wherein each of said plurality of memory elements further comprises a magnetic fixed layer separated from said magnetic reference layer by an anti-ferromagnetic coupling layer, said magnetic fixed layer has a second invariable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite said first invariable magnetization direction.

9. The STT-MRAM device of claim 8 , wherein each of said plurality of memory elements further comprises a second conductive layer formed in contact with said magnetic fixed layer opposite said anti-ferromagnetic coupling layer.

10. A spin transfer torque magnetic random access memory (STT-MRAM) device including a plurality of memory elements, each of said plurality of memory elements comprising:

a magnetic reference layer with a first invariable magnetization direction substantially perpendicular to a layer plane thereof;

a magnetic free layer separated from said magnetic reference layer by an insulating tunnel junction layer, said magnetic free layer having a variable magnetization direction substantially perpendicular to a layer plane thereof;

a magnesium oxide layer formed in contact with said magnetic free layer opposite said insulating tunnel junction layer;

a dielectric layer formed adjacent to said magnesium oxide layer opposite said magnetic free layer; and

a first conductive layer formed in contact with said dielectric layer opposite said magnesium oxide layer.

11. The STT-MRAM device of claim 10 , wherein each of said plurality of memory elements further comprises a second conductive layer formed in contact with said magnetic reference layer opposite said insulating tunnel junction layer.

12. The STT-MRAM device of claim 10 , wherein said dielectric layer has a relative permittivity of greater than 10.

13. The STT-MRAM device of claim 10 , wherein said dielectric layer is formed of a ferroelectric material.

14. The STT-MRAM device of claim 10 , wherein said dielectric layer is formed of a material selected from the group consisting of lead titanate, lead zirconate titanate, lead lanthanum zirconate titanate, barium titanate, lithium niobate, and combinations thereof.

15. The STT-MRAM device of claim 10 , wherein said magnetic reference layer and said magnetic free layer each is formed of an alloy comprising cobalt, iron, and boron.

16. The STT-MRAM device of claim 10 , wherein at least one of said magnetic reference layer and said magnetic free layer has a multilayer structure formed by interleaving two different types of materials with at least one of said two different types being magnetic.

17. The STT-MRAM device of claim 10 , wherein each of said plurality of memory elements further comprises a magnetic fixed layer separated from said magnetic reference layer by an anti-ferromagnetic coupling layer, said magnetic fixed layer has a second invariable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite said first invariable magnetization direction.

18. The STT-MRAM device of claim 17 , wherein each of said plurality of memory elements further comprises a second conductive layer formed in contact with said magnetic fixed layer opposite said anti-ferromagnetic coupling layer.

19. A method for switching resistance state of a memory element including a perpendicular magnetic tunnel junction therein, the method comprising the steps of:

applying a first voltage pulse to said memory element; and

after applying said first voltage pulse, instantly applying a second voltage pulse with opposite polarity to said first voltage pulse to said memory element.

Assignments (7)