Magnetic memory device having buffer layer

Patent metadata

Field	Value
Publication number	US-10050192-B2
Application number	US-201615373342-A
Country	US
Kind code	B2
Filing date	Dec 8, 2016
Priority date	Dec 11, 2015
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

The disclosed technology generally relates to magnetic memory devices, and more particularly to spin transfer torque magnetic random access memory (STT-MRAM) devices having a magnetic tunnel junction (MTJ), and further relates to methods of fabricating the STT-MRAM devices. In an aspect, a magnetoresistive random access memory (MRAM) device has a magnetic tunnel junction (MTJ). The MTJ includes a magnetic reference layer including CoFeB, a magnetic free layer comprising CoFeB, and a barrier layer including MgO. The barrier layer is interposed between the magnetic reference layer and the magnetic free layer. The barrier layer has a thickness adapted to tunnel electrons between the magnetic reference layer and the magnetic free layer sufficient to cause a change in the magnetization direction of the variable magnetization under a bias. The MTJ further comprises a buffer layer comprising one or more of Co, Fe, CoFe and CoFeB, where the buffer layer is doped with one or both of C and N.

First claim

What is claimed is:

1. A magnetoresistive random access memory (MRAM) device comprising a magnetic tunnel junction (MTJ), the MTJ comprising:
a magnetic reference layer comprising CoFeB and having a fixed magnetization direction;
a magnetic free layer comprising CoFeB and having a variable magnetization direction;
a barrier layer comprising MgO, wherein the barrier layer is interposed between the magnetic reference layer and the magnetic free layer, and wherein the barrier layer has a thickness adapted to tunnel electrons between the magnetic reference layer and the magnetic free layer at a current density sufficient to cause a change in the magnetization direction of the magnetic free layer under a write bias; and
one or more buffer layers formed at one or both sides of the barrier layer, wherein each of the one or more buffer layers comprises one or more of Co, Fe, CoFe and CoFeB and is doped with one or both of C and N.

2. The MRAM device according to claim 1 , wherein the magnetic reference layer comprises a plurality of layers, and wherein one of the one or more buffer layers is one of the plurality of layers of the magnetic reference layer or a separate layer adjacent to the magnetic reference layer.

3. The MRAM device according to claim 2 , wherein another one of the one or more buffer layers is one of the plurality of layers of the magnetic free layer or a separate layer adjacent to the magnetic reference layer.

4. The MRAM device according to claim 1 , wherein the magnetic free layer comprises a plurality of layers, and wherein one of the one or more buffer layers is formed as one of the plurality of layers of the magnetic free layer or a separate layer adjacent to the magnetic free layer.

5. The MRAM device according to claim 4 , wherein another one of the one or more buffer layers is one of the plurality of layers of the magnetic reference layer or a separate layer adjacent to the magnetic reference layer.

6. The MRAM device according to claim 1 , wherein one of the one or more buffer layers is arranged adjacent to the barrier layer.

7. The MRAM device according to claim 1 , wherein one of the one or more buffer layers is interposed between the barrier layer and the magnetic free layer.

8. The MRAM device according to claim 1 , wherein at least one of the one or more buffer layers serves as part of one or both of the magnetic reference layer and the magnetic free layer.

9. The MRAM device according to claim 1 , wherein at least one of the one or more buffer layers serve as a diffusion buffer layer between two layers contacting opposite sides of the at least one of the one or more buffer layers, such that each one of the contacting layers is substantially free of atomic elements of the other one of the contacting layers.

10. The MRAM device according to claim 9 , wherein the diffusion buffer layer is adapted to impede diffusion therethrough of at least one of B and 0 in the magnetic reference layer and/or the magnetic free layer.

11. The MRAM device according to claim 1 , wherein the buffer layer induces a strain in the MTJ.

12. The MRAM device according to claim 1 , wherein the buffer layer has a thickness in the range of 0.2 nm-2 nm.

13. The MRAM device according to claim 1 , wherein the buffer layer comprises a concentration of C or N within the range of 1 to 8 atomic percent.

14. The MRAM device according to claim 1 , wherein the MRAM device is a spin-transfer torque MRAM (STT-MRAM).

15. The MRAM device according to claim 1 , wherein the magnetic reference layer and the magnetic free layer has a direction of magnetic anisotropy that is perpendicular with respect to a major plane of one or both of the magnetic reference layer and the magnetic free layer.

16. The MRAM device according to claim 1 , wherein the one or more buffer layers is doped with one or both of C and N at a concentration of 1 to 8 atomic percent.

Assignees

• Imec Vzw

Inventors

• Swerts Johan
• Sankaran Kiroubanand
• Lin Tsann
• Pourtois Geoffrey

Classifications

• G11C11/161

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

• G11C2211/5615

  Multilevel magnetic memory cell using non-magnetic non-conducting interlayer, e.g. MTJ · CPC title

• H01L43/10

  Electricity · mapped topic

• H01L27/222

  Electricity · mapped topic

• H01L43/08 Primary

  Electricity · mapped topic