Magnetoresistive memory device including a plurality of reference layers

Patent metadata

Field	Value
Publication number	US-11839162-B2
Application number	US-202117358990-A
Country	US
Kind code	B2
Filing date	Jun 25, 2021
Priority date	Nov 22, 2019
Publication date	Dec 5, 2023
Grant date	Dec 5, 2023

Abstract

Magnetoelectric or magnetoresistive memory cells may include a plurality of reference layers and optionally a plurality of free layers to enhance the tunneling magnetoresistance (TMR) ratio.

First claim

What is claimed is:

1. A memory device, comprising:
a first electrode;
a second electrode;
a magnetic tunnel junction located between the first electrode and the second electrode and comprising:
a plurality of reference layers spaced apart from each other;
at least one free layer; and
a first nonmagnetic tunnel barrier layer interposed between a most proximal one of the plurality of reference layers and the at least one free layer; and

a composite synthetic antiferromagnet (SAF) structure located between the first electrode and the magnetic tunnel junction, wherein the SAF structure comprises a first superlattice, a second superlattice, and an antiferromagnetic coupling layer located between the first superlattice and the second superlattice;
wherein:
the antiferromagnetic coupling layer comprises an iridium layer;
the first superlattice comprises the first superlattice of first cobalt layers and first platinum layers; and
the second superlattice comprises the second superlattice of second cobalt layers and second platinum layers.

2. The memory device of claim 1 , wherein:
the first superlattice comprises N1 repetitions of a first unit layer stack of the first cobalt layer and the first platinum layer, and a first capping cobalt layer, such that N1 of the first platinum layers are interlaced with (N1+1) of the first cobalt layers;
N1 is an integer in a range from 2 to 10;
the second superlattice comprises N2 repetitions of a second unit layer stack of the second cobalt layer and the second platinum layer, and a second capping cobalt layer, such that N2 first platinum layers are interlaced with (N2+1) second cobalt layers; and
N2 is an integer in a range from 2 to 10.

3. The memory device of claim 2 , further comprising a tungsten layer located between the SAF structure and the magnetic tunnel junction.

4. The memory device of claim 3 , further comprising a tantalum seed layer and a platinum seed layer located between the first electrode and the SAF structure.

5. The memory device of claim 4 , wherein:
the tantalum seed layer and the platinum seed layer are located over the first electrode;
the SAF structure is located over the tantalum seed layer and the platinum seed layer;
the tungsten layer is located over the SAF structure;
a first reference layer of the plurality of reference layers is located over the tungsten layer;
a second reference layer of the plurality of reference layers is located over the first reference layer;
the first nonmagnetic tunnel barrier layer is located over the second reference layer; and
the at least one free layer is located over the first nonmagnetic tunnel barrier layer.

6. A memory device, comprising:
a first electrode;
a second electrode;
a magnetic tunnel junction located between the first electrode and the second electrode and comprising at least one reference layer, at least one free layer, and a nonmagnetic tunnel barrier layer interposed between the at least one reference layer and the at least one free layer; and
a composite synthetic antiferromagnet (SAF) structure located between the first electrode and the magnetic tunnel junction,
wherein:
the SAF structure comprises a first superlattice, a second superlattice, and an antiferromagnetic coupling layer located between the first superlattice and the second superlattice;
the first superlattice comprises N1 repetitions of a first unit layer stack of a first cobalt layer and a first platinum layer, and a first capping cobalt layer, such that N1 of the first platinum layers are interlaced with (N1+1) of the first cobalt layers;
N1 is an integer in a range from 2 to 10;
the second superlattice comprises N2 repetitions of a second unit layer stack of a second cobalt layer and a second platinum layer, and a second capping cobalt layer, such that N2 first platinum layers are interlaced with (N2+1) second cobalt layers; and
N2 is an integer in a range from 2 to 10.

7. The memory device of claim 6 , further comprising:
a tungsten layer located between the SAF structure and the magnetic tunnel junction; and
a tantalum seed layer and a platinum seed layer located between the first electrode and the SAF structure.

8. The memory device of claim 7 , wherein:
the antiferromagnetic coupling layer comprises an iridium layer;
the tantalum seed layer and the platinum seed layer are located over the first electrode;
the SAF structure is located over the tantalum seed layer and the platinum seed layer;
the tungsten layer is located over the SAF structure;
the at least one reference layer is located over the tungsten layer;
the nonmagnetic tunnel barrier layer is located over the at least one reference layer; and
the at least one free layer is located over the nonmagnetic tunnel barrier layer.

9. The memory device of claim 8 , wherein the at least one reference layer comprises a first reference layer and a second reference layer which are spaced apart from each other.

Assignees

• Western Digital Tech Inc

Inventors

• Kalitsov Alan
• Stewart Derek
• Prasad Bhagwati
• Mihajlovic Goran

Classifications

• H10N50/80 Primary

  Constructional details · CPC title

• G11C11/161 Primary

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

• H01F10/329

  Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect · CPC title

• H01F10/3254

  the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ] · CPC title

• H01F10/3286

  Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy · CPC title