# US 11,443,790 B2 · Spinel containing magnetic tunnel junction and method of making the same

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,443,790 B2
- Document ID: US11443790B2
- Status: Granted
- Kind: B2
- Application number: 17/192,354
- Filed: 2021-03-04
- Published: 2022-02-03
- Granted: 2022-09-13
- Earliest claimed: 2020-07-31
- Assignees: Western Digital Technologies, Inc.
- Applicants: Western Digital Technologies, Inc.
- Inventors: Bhagwati Prasad; Derek Stewart; Matthew Carey; Tiffany Santos
- Web page: https://patentgrep.com/patent/US11443790B2

## CPC

- G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell}
- G11C 11/1659: {Cell access}
- G11C 11/1675: {Writing or programming circuits or methods}
- G11C 11/18: using Hall-effect devices
- H01F 10/3272: {by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets}
- H01F 10/3286: {Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy}
- H01F 41/307: {insulating or semiconductive spacer}
- H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10N 50/01: Manufacture or treatment
- H10N 50/10: Magnetoresistive devices
- H10N 50/80: Constructional details
- H10N 50/85: Materials of the active region
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H10B: ELECTRONIC MEMORY DEVICES
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A magnetoresistive memory device includes a first electrode, a second electrode that is spaced from the first electrode, and a perpendicular magnetic tunnel junction layer stack located between the first electrode and the second electrode. The perpendicular magnetic tunnel junction layer stack includes, from one side to another: a reference layer having a fixed reference magnetization direction, a first spinel layer located including a first polycrystalline spinel material having (001) texture along an axial direction that is perpendicular to an interface with the reference layer, a magnesium oxide layer including a polycrystalline magnesium oxide material having (001) texture along the axial direction, a second spinel layer including a second polycrystalline spinel material having (001) texture along the axial direction, and a ferromagnetic free layer.

## Claims

### Claim 1

A magnetoresistive memory device, comprising:
a first electrode;
a second electrode that is spaced from the first electrode; and
a perpendicular magnetic tunnel junction layer stack located between the first electrode and the second electrode, the perpendicular magnetic tunnel junction layer stack comprising, from one side to another:
a reference layer having a fixed reference magnetization direction;
a first spinel layer located including a first polycrystalline spinel material having (001) texture along an axial direction that is perpendicular to an interface with the reference layer;
a magnesium oxide layer including a polycrystalline magnesium oxide material having (001) texture along the axial direction;
a second spinel layer including a second polycrystalline spinel material having (001) texture along the axial direction; and
a ferromagnetic free layer.

### Claim 2 (depends on 1)

The magnetoresistive memory device of claim 1, wherein the reference layer and the ferromagnetic free layer are polycrystalline and have (001) texture along the axial direction.

### Claim 3 (depends on 2)

The magnetoresistive memory device of claim 2, wherein grains of the reference layer are epitaxially aligned to grains of the first spinel layer across an interface between the reference layer and the first spinel layer.

### Claim 4 (depends on 2)

The magnetoresistive memory device of claim 2, wherein grains of the ferromagnetic free layer are epitaxially aligned to grains of the second spinel layer across an interface between the ferromagnetic free layer and the second spinel layer.

### Claim 5 (depends on 1)

The magnetoresistive memory device of claim 1, wherein the perpendicular magnetic tunnel junction layer stack further comprises a magnesium oxide capping dielectric layer contacting the ferromagnetic free layer and spaced from the second spinel layer.

### Claim 6 (depends on 5)

The magnetoresistive memory device of claim 5, wherein:
the magnetoresistive memory device comprises a voltage controlled magnetic anisotropy magnetoresistive memory device;
the magnesium oxide capping dielectric layer includes grains having (001) texture along the axial direction; and
the grains of the ferromagnetic free layer are epitaxially aligned to the grains of the magnesium oxide capping dielectric layer across an interface between the magnesium oxide capping dielectric layer and the ferromagnetic free layer.

### Claim 7 (depends on 1)

The magnetoresistive memory device of claim 1, wherein the perpendicular magnetic tunnel junction layer stack further comprises a nonmagnetic metal dust layer located between the second spinel layer and the ferromagnetic free layer and comprising a metal that increases perpendicular magnetic anisotropy of a ferromagnetic alloy of the ferromagnetic free layer.

### Claim 8 (depends on 7)

The magnetoresistive memory device of claim 7, wherein the nonmagnetic metal dust layer consists essentially of the at least one elemental metal selected from Ir, Pd, Mg, Pt, W, Ta, Hf, Pd, Ru, or Rh.

### Claim 9 (depends on 7)

The magnetoresistive memory device of claim 7, wherein the nonmagnetic metal dust layer has a thickness in a range from 0.1 nm to 1.2 nm.

### Claim 10 (depends on 1)

The magnetoresistive memory device of claim 1, wherein:
the first spinel layer comprises a material having a formula M1x1Q1y1Ox1, in which 0.95<x1<1.05, 1.95<y1<2.05 and 3.95<z1<4.05 and M1 and Q1 are different metals; and
the second spinel layer comprises a material having a formula M2x2Q2y2Oz2, in which 0.95<x2<1.05, 1.95<y2<2.05 and 3.95<z2<4.05 and M2 and Q2 are different metals.

### Claim 11 (depends on 10)

The magnetoresistive memory device of claim 10, wherein each of the first spinel layer and the second spinel layer comprises a respective material that is independently selected from MgAl2O4, ZnAl2O4, SiMg2O4, SiZn2O4, MgGa2O4, doped derivatives therefrom in which a fraction of at least one metallic element is replaced with another metallic element while preserving the crystalline structure, or oxygen-deficient derivatives thereof.

### Claim 12 (depends on 10)

The magnetoresistive memory device of claim 10, wherein:
the first spinel layer has a formula Mgx1Aly1Oz1, in which 0.95<x1<1.05, 1.95<y1<2.05 and 3.95<z1<4.05; and
the second spinel layer has a formula Mgx2Aly2Oz2, in which 0.95<x2<1.05, 1.95<y2<2.05 and 3.95<z2<4.05.

### Claim 13 (depends on 12)

The magnetoresistive memory device of claim 12, wherein:
the first spinel layer comprises MgAl2O4; and
the second spinel layer comprises MgAl2O4.

### Claim 14 (depends on 1)

The magnetoresistive memory device of claim 1, further comprising a synthetic antiferromagnet (SAF) structure located between the first electrode and the reference layer.

### Claim 15 (depends on 1)

The magnetoresistive memory device of claim 1, wherein a combination of the first spinel layer, the magnesium oxide layer, and the second spinel layer comprises a dielectric tunnel barrier which has a thickness in a range from 0.6 nm to 2 nm.

### Claim 16 (depends on 1)

The magnetoresistive memory device of claim 1, wherein:
the first spinel layer has a thickness in a range from 0.2 nm to 0.8 nm;
the magnesium oxide layer has a thickness in a range from 0.2 nm to 1.4 nm;
the second spinel layer has a thickness in a range from 0.2 nm to 0.8 nm;
the ferromagnetic free layer comprises a CoFeB or CoFe layer having a thickness in a range from 0.5 nm to 2 nm; and
the reference layer comprises a CoFeB or CoFe layer having a thickness in a range from 0.8 nm to 1.2 nm.

### Claim 17

A method of forming a magnetoresistive memory device, comprising:
forming a first electrode over a substrate;
depositing a ferromagnetic reference layer, a spinel layer including an amorphous spinel material, a ferromagnetic free layer, and a magnesium oxide layer including a polycrystalline magnesium oxide material having (001) texture;
performing an anneal process to induce solid phase epitaxy of the spinel layer using the magnesium oxide layer as a crystallization template layer, wherein the amorphous spinel material is converted into a polycrystalline spinel material having (001); and
forming a second electrode prior to or after the anneal process.

### Claim 18

A method of forming a magnetoresistive memory device, comprising:
forming a first electrode over a substrate;
depositing a magnetic tunnel junction layer stack over the first electrode, wherein the magnetic tunnel junction layer stack comprises a ferromagnetic reference layer, a first spinel layer including a first amorphous spinel material, a magnesium oxide layer including a polycrystalline magnesium oxide material having (001) texture along an axial direction that is perpendicular to an interface with the first spinel layer, a second spinel layer including a second amorphous spinel material, and a ferromagnetic free layer;
performing an anneal process to induce solid phase epitaxy of materials of the first spinel layer and the second spinel layer using the magnesium oxide layer as a crystallization template layer, wherein the first amorphous spinel material is converted into a first polycrystalline spinel material having (001) texture along the axial direction and the second amorphous spinel material is converted into a second polycrystalline spinel material having (001) texture; and
forming a second electrode over a portion of the magnetic tunnel junction layer stack prior to or after the anneal process.

### Claim 19 (depends on 18)

The method of claim 18, wherein:
the ferromagnetic reference layer as deposited comprises a first amorphous metallic material;
the ferromagnetic free layer as deposited comprises a second amorphous metallic material;
the solid phase epitaxy converts the first amorphous metallic material into a first polycrystalline ferromagnetic material and converts the second amorphous metallic material into a second polycrystalline ferromagnetic material;
grains in the first polycrystalline ferromagnetic material are epitaxially aligned grains of the first polycrystalline spinel material during the solid phase epitaxy; and
grains in the second polycrystalline ferromagnetic material are epitaxially aligned to grains of the second polycrystalline spinel material during the solid phase epitaxy.

### Claim 20 (depends on 19)

The method of claim 19, further comprising forming a nonmagnetic metal dust layer directly on the second spinel layer, wherein the ferromagnetic free layer is formed on the nonmagnetic metal dust layer, and the nonmagnetic metal dust layer comprises a metal that increases perpendicular magnetic anisotropy of the second polycrystalline ferromagnetic material.