VOLTAGE-SWITCHED MAGNETIC RANDOM ACCESS MEMORY (MRAM) AND METHOD FOR USING THE SAME

• US 20150332748A1
• Filed: 05/19/2014
• Published: 11/19/2015
• Est. Priority Date: 05/19/2014
• Status: Active Grant

• Current Assignee: Avalanche Technology Incorporated
• Original Assignee: Avalanche Technology Incorporated
• Inventors: Wang, Zihui, Wang, Xiaobin, Gan, Huadong, Zhou, Yuchen, Huai, Yiming
• Granted Patent: US 9,443,577 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/165 Auxiliary circuits
• CPC Class Codes: G11C 11/1659 Cell access
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: G11C 11/5607 using magnetic storage elements
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

The present invention is directed to a magnetic random access memory comprising a first magnetic tunnel junction (MTJ) including a first magnetic reference layer and a first magnetic free layer with a first insulating tunnel junction layer interposed therebetween; a second MTJ including a second magnetic reference layer and a second magnetic free layer with a second insulating tunnel junction layer interposed therebetween; and an anti-ferromagnetic coupling layer formed between the first and second variable magnetic free layers. The first and second magnetic free layers have a first and second magnetization directions, respectively, that are perpendicular to the layer planes thereof. The first magnetic reference layer has a first pseudo-fixed magnetization direction substantially perpendicular to the layer plane thereof. The second magnetic reference layer has a second pseudo-fixed magnetization direction that is substantially perpendicular to the layer plane thereof and is substantially opposite to the first pseudo-fixed magnetization direction.

Claims

1. A magnetic random access memory (MRAM) element comprising:

a first magnetic tunnel junction (MTJ) including a first magnetic reference layer and a first magnetic free layer with a first insulating tunnel junction layer interposed therebetween;

a second MTJ including a second magnetic reference layer and a second magnetic free layer with a second insulating tunnel junction layer interposed therebetween; and

an anti-ferromagnetic coupling layer that couples said first and second magnetic free layers to each other.

2. The MRAM element of claim 1, wherein said first magnetic reference layer has a first pseudo-fixed magnetization direction substantially perpendicular to a layer plane thereof, said second magnetic reference layer has a second pseudo-fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first pseudo-fixed magnetization direction.

3. The MRAM element of claim 1, wherein said first magnetic free layer has a first variable magnetization direction substantially perpendicular to a layer plane thereof, said second magnetic free layer has a second variable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first variable magnetization direction.

4. The MRAM element of claim 1, wherein said first magnetic free layer has a first magnetic moment, said second magnetic layer has a second magnetic moment substantially smaller than said first magnetic moment.

5. The MRAM element of claim 1, further comprising a first contact formed adjacent to said first magnetic reference layer opposite said first insulating tunnel junction layer and a second contact formed adjacent to said second magnetic reference layer opposite said second insulating tunnel junction layer.

6. The MRAM element of claim 1, wherein said first and second magnetic free layers each is made of an alloy comprising cobalt, iron, and boron.

7. The MRAM element of claim 1, wherein said first and second magnetic free layers each comprises two magnetic sublayers with a tantalum sublayer interposed therebetween.

8. The MRAM element of claim 1, wherein said first and second magnetic reference layers each is made of an alloy comprising cobalt, iron, and boron.

9. The MRAM element of claim 1, wherein said first and second magnetic reference layers each has a multilayer structure formed by interleaving two different types of materials with at least one of said two different types of materials being magnetic.

10. The MRAM element of claim 1, wherein said anti-ferromagnetic coupling layer is made of ruthenium or tantalum.

11. The MRAM element of claim 1, wherein each of said first and second insulating tunnel junction layers is made of magnesium oxide or aluminum oxide.

12. The MRAM element of claim 1, wherein each of said first and second insulating tunnel junction layers has an RA value in the range of about 20 to 2000 Ω

·

μ

m².

13. The MRAM element of claim 1, further comprising a first anti-ferromagnetic layer formed adjacent to said first magnetic reference layer opposite said first insulating tunnel junction layer.

14. The MRAM element of claim 13, further comprising a second anti-ferromagnetic layer formed adjacent to said second magnetic reference layer opposite said second insulating tunnel junction layer.

15. The MRAM element of claim 1, wherein said first magnetic reference layer has a first pseudo-fixed magnetization direction substantially perpendicular to a layer plane thereof, said second magnetic reference layer has a second pseudo-fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first pseudo-fixed magnetization direction, said first magnetic free layer has a first variable magnetization direction substantially perpendicular to a layer plane thereof, said second magnetic free layer has a second variable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first variable magnetization direction, said first magnetic free layer has a first magnetic moment, said second magnetic layer has a second magnetic moment substantially smaller than said first magnetic moment.

16. The MRAM element of claim 15, further comprising a first contact formed adjacent to said first magnetic reference layer opposite said first insulating tunnel junction layer and a second contact formed adjacent to said second magnetic reference layer opposite said second insulating tunnel junction layer.

17. A method for switching the MRAM element of claim 16 from low to high resistance state, comprising the steps of:

applying an electric potential with a positive terminal electrically connected to said second contact and a negative terminal electrically connected to said first contact to partially rotate said first pseudo-fixed magnetization direction, thereby allowing said first and second variable magnetization directions to switch from parallel to anti-parallel orientation with respect to said first and second pseudo-fixed magnetization directions; and

removing said electric potential to allow said first pseudo-fixed magnetization direction to rotate back.

18. A method for switching the MRAM element of claim 16 from high to low resistance state, comprising the steps of:

applying an electric potential with a positive terminal electrically connected to said first contact and a negative terminal electrically connected to said second contact to partially rotate said second pseudo-fixed magnetization direction, thereby allowing said first and second variable magnetization directions to switch from anti-parallel to parallel orientation with respect to said first and second pseudo-fixed magnetization directions; and

removing said electric potential to allow said second pseudo-fixed magnetization direction to rotate back.