Tunnel barriers based on rare earth element oxides

• US 7,345,855 B2
• Filed: 09/07/2005
• Issued: 03/18/2008
• Est. Priority Date: 09/07/2005
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Parkin, Stuart Stephen Papworth
• Primary Examiner(s): CAO, ALLEN T
• Application Number:
  US11/221,624
• Publication Number:
  US 20070053113A1
• Time in Patent Office: 923 Days
• Field of Search: 360/122, 360/126, 360/324.2, 257/30, 257/E43.005, 257/E21.665, 365/173
• US Class Current: 360/324.2
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• CPC Class Codes: H01F 10/187 Amorphous compounds H01F10/3204 takes precedence
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3295 Spin-exchange coupled multilayers wherein the magnetic pinned or free layers are laminated without anti-parallel coupling within the pinned and free layers
• CPC Class Codes: H01F 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

Magnetic tunnel junctions are disclosed that include ferromagnetic (or ferrimagnetic) materials and a bilayer tunnel barrier structure that includes a layer of a rare earth oxide. The bilayer also includes a layer of crystalline material, such as MgO or Mg—ZnO. If MgO is used, then it is preferably (100) oriented. The magnetic tunnel junctions so formed enjoy high tunneling magnetoresistance, e.g., much greater than 100% at room temperature.

Claims

1. A device, comprising:

a tunnel barrier structure, the structure including

i) a first layer that includes a rare earth element oxide tunnel barrier, and

ii) a second layer that includes at least one of a crystalline MgO tunnel barrier and a crystalline Mg—

ZnO tunnel barrier; and

an underlayer in contact with the tunnel barrier structure, wherein the underlayer, the first layer, and the second layer are in proximity with each other, thereby enabling spin-polarized charge carrier transport between the underlayer and the first and second layers, wherein the underlayer includes a material selected from the group consisting of ferrimagnetic materials, ferromagnetic materials, and semiconducting materials.

2. The device of claim 1, wherein the first layer is amorphous.

3. The device of claim 1, wherein the underlayer includes at least one of Si and GaAs.

4. The device of claim 1, wherein the underlayer includes a material selected from the group consisting of ferrimagnetic materials and ferromagnetic materials.

5. The device of claim 4, further comprising an overlayer that includes a material selected from the group consisting of ferrimagnetic materials and ferromagnetic materials, wherein the underlayer, the tunnel barrier structure, and the overlayer form a magnetic tunnel junction.

6. The device of claim 4, wherein the second layer includes crystalline grains that are substantially (100) oriented.

7. The device of claim 1, the tunnel barrier structure further comprising an Al₂O₃ tunnel barrier.

8. The device of claim 1, wherein the rare earth element oxide includes an oxide of Lu.

9. The device of claim 1, wherein the rare earth element oxide includes an oxide of Gd.

10. The device of claim 1, wherein the rare earth element oxide includes an oxide of Yb.

11. A method of forming the device of claim 1, comprising:

forming the second layer by;

depositing at least one first metal onto a surface of the underlayer to form a metal layer thereon, wherein the surface is substantially free of oxide; and

directing at least one second metal, in the presence of oxygen, towards the metal layer to form a metal oxide tunnel barrier in contact with the underlayer, the oxygen reacting with the second metal and the metal layer, wherein the metal oxide tunnel barrier includes Mg; and

forming the first layer by forming a rare earth element oxide tunnel barrier over the metal oxide tunnel barrier.

12. The method of claim 11, wherein the metal oxide tunnel barrier includes a MgO tunnel barrier.

13. The method of claim 11, wherein the metal oxide tunnel barrier includes a Mg—

ZnO tunnel barrier.

14. The method of claim 11, further comprising annealing the metal oxide tunnel barrier to improve its performance.

15. A method of forming the device of claim 1, comprising:

depositing at least one first metal that includes Mg onto a surface of the underlayer to form a metal layer thereon, wherein the surface is substantially free of oxide; and

directing at least one second metal that includes a rare earth element, in the presence of oxygen, towards the metal layer to form a bilayer in contact with the underlayer, the bilayer including the first layer and the second layer.

17. The device of claim 10, wherein the first and second magnetic layers each include a Co—

Fe alloy, and the rare earth element oxide includes an oxide of at least one of Lu, Gd, and Yb.

18. The device of claim 10, wherein the device has a tunneling magnetoresistance of greater than 100% at room temperature.

19. The device of claim 10, wherein the device has a tunneling magnetoresistance of greater than 200% at room temperature.

20. The device of claim 10, wherein the device has a tunneling magnetoresistance of greater than 300% at room temperature.

16. A device, comprising:

a first magnetic layer;

a second magnetic layer, wherein each of the first and second magnetic layers includes a material selected from the group consisting of ferrimagnetic materials and ferromagnetic materials;

a first tunnel barrier layer that includes a rare earth element oxide tunnel barrier; and

a second tunnel barrier layer that includes at least one of a crystalline MgO tunnel barrier and a crystalline Mg—

ZnO tunnel barrier, the first and second tunnel barrier layers forming a bilayer of tunnel barriers, wherein the first magnetic layer, the tunnel barrier bilayer, and the second magnetic layer form a magnetic tunnel junction.