Magnetic tunnel junction with low defect rate after high temperature anneal for magnetic device applications

Patent metadata

Field	Value
Publication number	US-9842988-B2
Application number	US-201514803111-A
Country	US
Kind code	B2
Filing date	Jul 20, 2015
Priority date	Jul 20, 2015
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A magnetic tunnel junction is disclosed wherein the reference layer and free layer each comprise one layer having a boron content from 25 to 50 atomic %, and an adjoining second layer with a boron content from 1 to 20 atomic %. One of the first and second layers in each of the free layer and reference layer contacts the tunnel barrier. Each boron containing layer has a thickness of 1 to 10 Angstroms and may include one or more B layers and one or more Co, Fe, CoFe, or CoFeB layers. As a result, migration of non-magnetic metals along crystalline boundaries to the tunnel barrier is prevented, and the MTJ has a low defect count of around 10 ppm while maintaining an acceptable TMR ratio following annealing to temperatures of about 400° C. The boron containing layers are selected from CoB, FeB, CoFeB and alloys thereof including CoFeNiB.

First claim

We claim:

1. A magnetic tunnel junction (MTJ) element in a magnetic device, comprising:
(a) a reference layer with an AP2/NM1/AP1 configuration wherein AP2 is a first magnetic layer, AP1 is a second magnetic layer that adjoins a tunnel barrier along a first surface, and NM1 is a first non-magnetic layer that enables anti-ferromagnetic coupling between AP1 and AP2, or provides a moment diluting effect in the reference layer, the AP1 layer is comprised of a first layer with a boron content between 25 and 50 atomic %, and a second layer with a low boron content between 1 and 20 atomic % and the second layer is amorphous that contacts the tunnel barrier;
(b) the tunnel barrier; and
(c) a free magnetic layer stack comprised of a first free magnetic layer with a boron content between 25 and 50 atomic %, and a second free magnetic layer with a low boron content between 1 and 20 atomic %, the first free magnetic layer forms an interface with the second free magnetic layer, and contacts a surface of the tunnel barrier that is opposite to the first surface, and wherein one or both of the first and second free layers have a multilayer configuration comprised of one or more layers consisting of B, and one or more layers selected from Co, Fe, CoFe, CoFeNi, CoFeB, and CoFeQ wherein Q is one of Zr, Hf, Nb, Ta, Mo, and W.

2. The MTJ element of claim 1 wherein each of the first and second layers in the AP1 layer have a composition that is selected from CoB, FeB, CoFeB, CoFeNiB, or CoFeBQ wherein Q is one of Zr, Hf, Nb, Ta, Mo, and W.

3. The MTJ element of claim 1 wherein each of the first and second layers in the AP1 layer has a thickness from about 1 to 10 Angstroms.

4. The MTJ element of claim 1 wherein each of the first free magnetic layer and second free magnetic layer has a thickness from about 1 to 10 Angstroms.

5. The MTJ element of claim 2 wherein one or both of the first and second layers in the AP1 layer are comprised of a bilayer configuration wherein one layer is Co, Fe, CoFe, CoFeNi, CoFeB, or CoFeQ, and a second layer is B.

6. The MTJ element of claim 2 wherein one or both of the first and second layers in the AP1 layer have a multilayer configuration comprised of one or more layers of B, and one or more layers selected from Co, Fe, CoFe, CoFeNi, CoFeB, and CoFeQ.

7. The MTJ element of claim 1 wherein the tunnel barrier is an oxide, oxynitride, or nitride of Mg, Ti, AlTi, MgZn, Al, Zn, Zr, Ta, or Hf, or is a native oxide of CoFeB, CoB, or FeB, or is a laminated stack of one or more of the aforementioned materials.

8. The MTJ element of claim 1 wherein NM1 is one of Ru, Rh, and Ir to give a synthetic anti-parallel (SyAP) configuration for the reference layer.

9. The MTJ element of claim 1 wherein the free magnetic layer stack has a FL1/FL2/NM2/FL3 configuration wherein FL1 is one of the first or second free magnetic layers, FL2 is the other of the first or second free magnetic layers, FL3 is a third free magnetic layer, and NM2 is a second non-magnetic layer that enables anti-ferromagnetic coupling between FL2 and FL3, or provides a moment diluting effect in the free magnetic layer stack.

10. The MTJ element of claim 1 wherein the magnetic device is a magnetoresistive random access memory (MRAM), spin-torque MRAM, embedded MRAM, or a spintronic device, or is a sensor in a read head.

11. A magnetic tunnel junction (MTJ) element in a magnetic device, comprising:
(a) a reference layer with an AP2/NM1/AP1 configuration wherein AP2 is a first magnetic layer, AP1 is a second magnetic layer that adjoins a tunnel barrier along a first surface, and NM1 is a first non-magnetic layer that enables anti-ferromagnetic coupling between AP1 and AP2, or provides a moment diluting effect in the reference layer, the AP1 layer is comprised of a first layer with a boron content between 25 and 50 atomic %, and a second layer with a low boron content between 1 and 20 atomic % and the second layer is amorphous that contacts the tunnel barrier, and wherein one or both of the first and second layers in the AP1 layer have a multilayer configuration comprised of one or more layers consisting of B, and one or more layers selected from Co, Fe, CoFe, CoFeNi, CoFeB, and CoFeQ wherein Q is one of Zr, Hf, Nb, Ta, Mo, and W;
(b) the tunnel barrier; and
(c) a free magnetic layer stack comprised of a first free magnetic layer with a boron content between 25 and 50 atomic %, and a second free magnetic layer that is one of CoB, FeB, or CoFeB with a low boron content between 1 and 20 atomic %, the first free magnetic layer forms an interface with the second free magnetic layer, and contacts a surface of the tunnel barrier that is opposite to the first surface, and wherein both of the first and second free magnetic layers have a multilayer configuration comprised of one or more layers of B, and one or more layers selected from Co, Fe, CoFe, CoFeNi, CoFeB, and CoFeQ.

Assignees

• Headway Tech Inc

Inventors

• Liu Huanlong
• Lee Yuan-Jen
• Zhu Jian
• Jan Guenole
• Wang Po-Kang

Classifications

• H01F10/3295

  Spin-exchange coupled multilayers wherein the magnetic pinned or free layers are laminated without anti-parallel coupling within the pinned and free layers · CPC title

• G11C11/161

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

• H01L43/08

  Electricity · mapped topic

• H01F41/307

  insulating or semiconductive spacer · CPC title

• H01L43/02

  Electricity · mapped topic