Low resistance tunneling magnetoresistive sensor with composite inner pinned layer

• US 20080299679A1
• Filed: 05/29/2007
• Published: 12/04/2008
• Est. Priority Date: 05/29/2007
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated
• Original Assignee: Headway Technologies Incorporated
• Inventors: Chen, Yu-Hsia, Zhang, Kunliang, Li, Min, Wang, Hui-Chuan, Zhao, Tong
• Granted Patent: US 7,602,033 B2
• Time in Patent Office: Days
• US Class Current: 438/3
• 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: B82Y 40/00 Manufacture or treatment of nanostructures
• 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: 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: 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 41/303 with exchange coupling adjustment of magnetic film pairs, e.g. interface modifications by reduction, oxidation
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A high performance TMR sensor is fabricated by employing a composite inner pinned (AP1) layer in an AP2/Ru/AP1 pinned layer configuration. In one embodiment, there is a 10 to 80 Angstrom thick lower CoFeB or CoFeB alloy layer on the Ru coupling layer, a and 5 to 50 Angstrom thick Fe or Fe alloy layer on the CoFeB or CoFeB alloy, and a 5 to 30 Angstrom thick Co or Co rich alloy layer formed on the Fe or Fe alloy. A MR ratio of about 48% with a RA of <2 ohm-um² is achieved when a CoFe AP2 layer, MgO (NOX) tunnel barrier, and CoFe/NiFe free layer are used in the TMR stack. Improved RA uniformity and less head noise are observed. Optionally, a CoFe layer may be inserted between the coupling layer and CoFeB or CoFeB alloy layer to improve pinning strength and enhance crystallization.

Claims

1. A pinned layer in a magnetoresistive element of a magnetic device, comprising:

(a) an outer pinned (AP2) layer;

(b) a coupling layer having one side formed on the AP2 layer; and

(c) an inner pinned (AP1) layer formed on a side of the coupling layer opposite the AP2 layer, said AP1 layer has a composite configuration comprised of at least a

(1) a CoFeB or CoFeB alloy layer;

(2) a Fe or Fe alloy layer formed on the CoFeB or CoFeB alloy layer; and

(3) a Co or Co alloy layer formed on the Fe or Fe alloy layer wherein said Co or Co alloy layer contacts a tunnel barrier layer in the magnetoresistive element.

2. The pinned layer of claim 1 wherein said magnetoresistive element is a tunneling magnetoresistive (TMR) sensor further comprised of a seed layer formed on a substrate, an anti-ferromagnetic (AFM) layer on the seed layer, a free layer formed on the tunnel barrier layer, and a capping layer on the free layer, said AP2 layer contacts the AFM layer.

3. The pinned layer of claim 1 wherein the CoFeB or CoFeB alloy has a thickness between about 10 and 80 Angstroms, the Fe or Fe alloy layer has a thickness from about 5 to 50 Angstroms, and the Co or Co alloy layer has a thickness between about 5 and 30 Angstroms.

4. The pinned layer of claim 1 wherein the CoFeB layer has a composition represented by Co_(100-X-Y)Fe_XB_Y where x is from about 5 to 95 atomic % and y is from about 5 to 40 atomic %.

5. The pinned layer of claim 1 wherein the Fe alloy comprises Co, Ni, or B and has a Fe content of at least 25 atomic %, the Co alloy has a Co content of greater than 90 atomic %, and the CoFeB alloy has a composition represented by CoFeBM where M is one or more of Ni, Zr, Hf, Ta, Mo, Nb, Pt, Cr, Si, and V.

6. The pinned layer of claim 1 wherein the AP1 layer is further comprised of a CoFe layer formed between the coupling layer and the CoFeB or CoFeB alloy layer.

7. The pinned layer of claim 1 wherein the tunnel barrier layer is comprised of MgO, AlOx, TiOx, TiAlOx, MgZnOx, or any combination of the aforementioned materials.

8. A TMR sensor in a magnetic device, comprising:

a seed layer, AFM layer, pinned layer, tunnel barrier layer, free layer, and capping layer that are sequentially formed on a substrate, said pinned layer is comprised of

(a) an outer pinned (AP2) layer formed on the AFM layer;

(b) a coupling layer having one side formed on the AP2 layer; and

(c) an inner pinned (AP1) layer formed on a side of the coupling layer opposite the AP2 layer, said AP1 layer has a composite configuration comprised of at least

(1) a CoFeB or CoFeB alloy layer;

(2) a Fe or Fe alloy layer formed on the CoFeB or CoFeB alloy layer; and

(3) a Co or Co alloy layer formed on the Fe or Fe alloy layer wherein said Co or Co alloy layer contacts the tunnel barrier layer.

9. The TMR sensor of claim 8 wherein said AP2 layer is CoFe, the coupling layer is Ru, and the AP1 layer has a CoFeB/Fe/Co configuration in which the CoFeB layer has a thickness between about 5 and 50 Angstroms and a composition represented by Co_(100-X-Y)Fe_XB_Y where x is from about 5 to 95 atomic % and y is from about 5 to 40 atomic %, the Fe layer has a thickness from about 5 to 50 Angstroms, and the Co layer has a thickness from about 5 to 30 Angstroms.

10. The TMR sensor of claim 8 wherein the AP1 layer is further comprised of a CoFe layer formed between the CoFeB or CoFeB alloy layer and the coupling layer.

11. The TMR sensor of claim 8 wherein the Fe alloy comprises Co, Ni, or B and has a Fe content of at least 25 atomic %, the Co alloy has a Co content of greater than 90 atomic %, and the CoFeB alloy has a composition represented by CoFeBM where M is one or more of Ni, Zr, Hf, Ta, Mo, Nb, Pt, Cr, Si, and V.

12. The TMR sensor of claim 9 wherein the seed layer is Ta/Ru, the AFM layer is IrMn, the tunnel barrier layer is comprised of MgO, the free layer is made of CoFe/NiFe, and the capping layer has a Ta/Ru configuration.

13. A method of forming a pinned layer in a TMR sensor in a magnetic device, comprising:

(a) forming an outer (AP2) layer;

(b) forming a coupling layer having one side on the AP2 layer; and

(c) forming an inner (AP1) layer on a side of the coupling layer opposite the AP2 layer, said AP1 layer has a composite configuration comprised of

(1) a CoFeB or CoFeB alloy layer;

(2) a Fe or Fe alloy layer formed on the CoFeB or CoFeB alloy layer; and

(3) a Co or Co alloy layer formed on the Fe or Fe alloy layer wherein said Co or Co alloy layer contacts a tunnel barrier layer in the TMR sensor.

14. The method of claim 13 wherein said TMR sensor is further comprised of a seed layer formed on a substrate, an anti-ferromagnetic (AFM) layer on the seed layer, a free layer formed on the tunnel barrier layer, and a capping layer on the free layer, said AP2 layer contacts the AFM layer.

15. The method of claim 13 further comprised of forming an additional AP1 layer made of CoFe between the CoFeB or CoFeB alloy layer and coupling layer.

16. The method of claim 13 wherein the CoFeB or CoFeB alloy layer has a thickness between about 10 and 80 Angstroms and a composition represented by Co_(100-X-Y)Fe_XB_Y where x is from about 5 to 95 atomic % and y is from about 5 to 40 atomic %, or a composition represented by CoFeBM where M is one or more of Ni, Zr, Hf, Ta, Mo, Nb, Pt, Cr, Si, and V.

17. The method of claim 13 wherein the Co or Co alloy layer has a thickness between about 5 and 30 Angstroms and the Co alloy has a Co content greater than 90 atomic %, and said Fe or Fe alloy layer has a thickness of about 5 to 50 Angstroms and the Fe alloy comprises Co, Ni, or B and has a Fe content of at least 25 atomic %.

18. The method of claim 13 further comprised of annealing the TMR sensor comprising said pinned layer at a temperature between about 240°

C. and 340°

C.

19. The method of claim 13 further comprising the formation of a surfactant layer between the CoFeB or CoFeB alloy layer and the Co or Co alloy layer, or forming a surfactant layer between the Co or Co alloy layer and the tunnel barrier layer.

20. The method of claim 13 further comprising a plasma treatment of the CoFeB or CoFeB alloy layer prior to forming the Co or Co alloy layer, or a plasma treatment of the Co or Co alloy layer prior to forming the tunnel barrier layer.