Magnetic tunnel junction device

• US 8,216,703 B2
• Filed: 02/21/2008
• Issued: 07/10/2012
• Est. Priority Date: 02/21/2008
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated (TDK Corporation)
• Original Assignee: Everspin Technologies Incorporated
• Inventors: Sun, Jijun, Slaughter, Jon M.
• Primary Examiner(s): BERNATZ, KEVIN M
• Application Number:
  US12/035,011
• Publication Number:
  US 20090213503A1
• Time in Patent Office: 1,601 Days
• Field of Search: None
• US Class Current: 428/811.1
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• CPC Class Codes: G11B 5/3906 Details related to the use of magnetic thin film layers or to their effects
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3272 by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1121 Multilayer
• CPC Class Codes: Y10T 428/1143 with defined structural feature

Abstract

A magnetic tunnel junction (MTJ) (10) employing a dielectric tunneling barrier (16), useful in magnetoresistive random access memories (MRAMs) and other devices, has a synthetic antiferromagnet (SAF) structure (14, 16), comprising two ferromagnetic (FM) layers (26, 41; 51, 58; 61, 68) separated by a coupling layer (38, 56, 66). Improved magnetoresistance (MR) ratio is obtained by providing a further layer (44, 46, 46′, 47, 52, 62), e.g. containing Ta, preferably spaced apart from the coupling layer (38, 56, 66) by a FM layer (41, 30-2, 54). The further layer (44, 46, 46′, 47, 52, 62) may be a Ta dusting layer (44) covered by a FM layer (30-2), or a Ta containing FM alloyed layer (46), or a stack (46′) of interleaved FM and N-FM layers, or other combination (47, 62). Furthering these benefits, another FM layer, e.g., CoFe, NiFe, (30, 30-1, 51, 61) is desirably provided between the further layer (44, 46, 46′, 47, 52, 62) and the tunneling barrier (16). Ta, Zr, Hf, Ti, Mg, Nb, V, Zn, Cr, NiFeX, CoFeX and CoFeBX (X═Ta, Zr, Hf, Ti, Mg, Nb, V, Zn, Cr) are useful for the further layer (44, 46, 46′, 47, 52, 62).

Claims

1. A magnetic tunnel junction device, comprising:

a synthetic antiferromagnet (SAF) structure having at least first and second ferromagnetic (FM) layers separated by a coupling layer, wherein the first FM layer has first and second portions;

a further FM layer containing Ta, Zr, Hf, Ti, Mg, Nb, V, Zn, Cr or a combination thereof and a FM material as an alloy, spaced apart from the coupling layer by at least the first portion of the first FM layer and

a dielectric tunnel barrier proximate the second portion of the first FM layer.

2. The device of claim 1, wherein the dielectric tunnel barrier contacts the second portion of the first FM layer.

3. The device of claim 1, further comprising a top electrode and wherein the SAF structure is a free SAF structure and the second FM layer abuts the top electrode.

4. The device of claim 3, further comprising a still further layer containing one or more of Ta, Zr, Hf, Ti, Mg, Nb, V, Zn, Cr or a combination thereof, located between the second FM layer and the top electrode.

5. The device of claim 1, wherein the further FM layer comprises a stack of double layers having sequential layers of FM material interleaved with layers of N-FM material comprising Ta, Zr, Hf, Ti, Mg, Nb, V, Zn, Cr or a combination thereof.

6. The device of claim 1, wherein at least one of (i) the first portion of the first FM layer and (ii) the second portion of the first FM layer comprises one or more of CoFe, NiFe, NiFeCo, or CoFeX where X is a N-FM material.

7. The device of claim 6, wherein X comprises boron.

8. The device of claim 1, wherein the SAF structure is a free SAF structure and the further FM layer is located at least 20 Angstroms from the tunnel barrier.

9. The device of claim 1, wherein the SAF structure is a pinned SAF structure and the further FM layer is located at least 5 Angstroms from the tunnel barrier.

10. An electronic device, comprising:

a top electrode;

a tunnel barrier;

a free synthetic anti-ferromagnetic (SAF) structure located between the tunnel barrier and the top electrode and comprising;

first and second ferromagnetic (FM) layers, wherein the first FM layer overlies the tunnel barrier and the second FM layer underlies the top electrode;

a non-ferromagnetic (N-FM) coupling layer comprising one or more of Ru, Re, Os, Ir, and Rh, located between the first and second FM layers;

a further FM layer containing a N-FM material and a FM material as an alloy located between the coupling layer and the first FM layer, the N-FM material consisting of at least one of the materials selected from Ta, Zr, Hf, Ti, V, Nb, Mg, Zn, and Cr; and

a still further FM layer located between the coupling layer and the further FM layer.

11. The device of claim 10, wherein the first FM layer separates the further FM layer from the tunnel barrier by a distance of at least 20 Angstroms.

12. The device of claim 10, wherein the N-FM material and the FM material of the further FM layer are approximately in the ratio of about 5-25% N-FM to about 75-95% FM material.

13. The electronic device of claim 10 wherein the further FM layer comprises alternating layers of FM and N-FM material, the N-FM material layers being of thickness 3 Angstroms or less.

14. The electronic device of claim 10 further comprising an additional layer containing N-FM material between the top electrode and the second FM layer.

15. The electronic device of claim 10 further comprising a N-FM layer between the non-ferromagnetic (N-FM) coupling layer and the still further FM layer.

16. The device of claim 10, wherein the further FM layer contains an amount of N-FM material corresponding to 3 bulk Angstroms or less.

17. An electronic device incorporating a pinned synthetic anti-ferromagnetic (SAF) structure, comprising:

a pinning layer;

a tunnel barrier;

a pinned synthetic anti-ferromagnetic (SAF) structure between the tunnel barrier and the pinning layer and comprising;

first and second ferromagnetic (FM) layers, wherein the first FM layer underlies the tunnel barrier and the second FM layer overlies the pinning layer;

a non-ferromagnetic (N-FM) coupling layer comprising one or more of Ru, Re, Os, Ir, and Rh, located between the first and second FM layers;

a further FM layer containing a N-FM material and a FM material as an alloy located between the coupling layer and the first FM layer, the N-FM material consisting of at least one of the materials selected from Ta, Zr, Hf, Ti, V, Nb, Mg, Zn, and Cr; and

an additional FM layer located between the coupling layer and the further FM layer.

18. The device of claim 17, wherein the first FM layer separates the further FM layer from the tunnel barrier by a distance of at least 5 Angstroms.

19. The device of claim 17, wherein the N-FM material and the FM material of the further FM layer are approximately in the ratio of about 5-25% N-FM to about 75-95% FM material.

20. The electronic device of claim 17 further comprising a N-FM layer between the non-ferromagnetic (N-FM) coupling layer and the additional FM layer.

21. The device of claim 17, wherein the further FM layer contains an amount of N-FM material corresponding to 3 bulk Angstroms or less.