Magnetic exchange coupled MTJ free layer with double tunnel barriers having low switching current and high data retention

• US 10,332,576 B2
• Filed: 06/07/2017
• Issued: 06/25/2019
• Est. Priority Date: 06/07/2017
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hu, Guohan, Worledge, Daniel C.
• Primary Examiner(s): Cho, Sung Il
• Application Number:
  US15/616,283
• Publication Number:
  US 20180358065A1
• Time in Patent Office: 748 Days
• Field of Search: 365158
• 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 11/1675 Writing or programming circuits or methods
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• 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

Embodiments of the invention are directed to a magnetic tunnel junction (MTJ) storage element that includes a reference layer, a tunnel barrier and a free layer on an opposite side of the tunnel barrier layer from the reference layer. The reference layer has a fixed magnetization direction. The free layer includes a first region, a second region and a third region. The third region is formed from a third material that is configured to magnetically couple the first region and the second region. The first region is formed from a first material having a first predetermined magnetic moment, and the second region is formed from a second material having a second predetermined magnetic moment. The first predetermined magnetic moment is lower that the second predetermined magnetic moment.

Claims

1. A magnetic tunnel junction (MTJ) storage element comprising:

a first reference layer having a first fixed magnetization direction;

a first tunnel barrier layer;

a free layer on an opposite side of the first tunnel barrier layer from the first reference layer;

a second tunnel barrier on an opposite side of the free layer from the first tunnel barrier; and

a second reference layer having a second fixed magnetization direction, where the second reference layer is on an opposite side of the second tunnel barrier from the free layer;

where the free layer comprises;

a first region comprising a first material configured to include a first predetermined magnetic moment and a first switchable magnetization direction;

a second region comprising a second material configured to include a second predetermined magnetic moment and a second switchable magnetization direction;

a third region comprising a third material configured to include a third predetermined magnetic moment and a third switchable magnetization direction;

a first spacer material between the first region and the second region, where the first spacer material is configured to provide magnetic exchange coupling between the first region and the second region; and

a second spacer material between the second region and the third region, where the second spacer material is configured to provide magnetic exchange coupling between the second region and the third region;

where the first predetermined magnetic moment is configured to be lower than the second predetermined magnetic moment;

where the third predetermined magnetic moment is configured to be lower than the second predetermined magnetic moment;

where the first region, the second region, and the first spacer material are configured such that a direction of the first switchable magnetization direction changing causes a direction of the second switchable magnetization direction to change;

where the third region, the second region, and the second spacer material are configured such that a direction of the third switchable magnetization direction changing causes the direction of the second switchable magnetization direction to change.

2. The MTJ storage element of claim 1, where:

the first region is configured to receive spin torque electrons that are generated in the first reference layer; and

the third region is configured to receive spin torque electrons that are generated in the second reference layer.

3. The MTJ storage element of claim 2, where:

the first reference layer is configured to, based at least in part on the MTJ receiving a write pulse, generate an amount of spin torque electrons in the first reference layer material that is insufficient to initiate a process of switching the second switchable magnetization direction of the second region or the third switchable magnetization direction of the third region; and

the amount of spin torque electrons being generated in the first reference layer is sufficient to initiate a process of switching the first switchable magnetization direction of the first region.

4. The MTJ storage element of claim 3, where the first region is configured such that the first switchable magnetization direction switching assists the process of switching the second switchable magnetization direction of the second region based at least in part on the magnetic exchange coupling between the first region and the second region provided by the first spacer material.

5. The MTJ storage element of claim 2, where:

the second reference layer is configured to, based at least in part on the MTJ receiving a write pulse, generate an amount of spin torque electrons in the second reference layer material that is insufficient to initiate a process of switching the second switchable magnetization direction of the second region or the first switchable magnetization direction of the first region; and

the amount of spin torque electrons being generated in the second reference layer is sufficient to initiate a process of switching the third switchable magnetization direction of the third region.

6. The MTJ storage element of claim 5, where the third region is configured such that the third switchable magnetization direction switching assists the process of switching the second switchable magnetization direction of the second region based at least in part on the magnetic exchange coupling between the third region and the second region provided by the second spacer material.

7. The MTJ storage element of claim 1, where:

the first material is further configured to include a first predetermined activation energy;

the second material is further configured to include a second predetermined activation energy;

the third material is further configured to include a third predetermined activation energy; and

the second predetermined activation energy is configured to be higher than each of the first predetermined activation energy and the third predetermined activation energy.

8. The MTJ storage element of claim 1, where the first spacer material and the second spacer material comprise a nonmagnetic material.

9. The MTJ storage element of claim 1, where:

the first material includes dopants; and

a level of the dopants comprises within a range from about 5% to about 30% of the first material.