Low resistance tunneling magnetoresistive sensor with natural oxidized double MgO barrier

• US 20070111332A1
• Filed: 11/16/2005
• Published: 05/17/2007
• Est. Priority Date: 11/16/2005
• 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 7,780,820 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 33/093 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: 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 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1143 with defined structural feature

Abstract

A high performance TMR sensor is fabricated by incorporating a tunnel barrier having a Mg/MgO/Mg configuration. The 4 to 14 Angstroms thick lower Mg layer and 2 to 8 Angstroms thick upper Mg layer are deposited by a DC sputtering method while the MgO layer is formed by a NOX process involving oxygen pressure from 0.1 mTorr to 1 Torr for 15 to 300 seconds. NOX time and pressure may be varied to achieve a MR ratio of at least 34% and a RA value of 2.1 ohm-um². The NOX process provides a more uniform MgO layer than sputtering methods. The second Mg layer is employed to prevent oxidation of an adjacent ferromagnetic layer. In a bottom spin valve configuration, a Ta/Ru seed layer, IrMn AFM layer, CoFe/Ru/CoFeB pinned layer, Mg/MgO/Mg barrier, CoFe/NiFe free layer, and a cap layer are sequentially formed on a bottom shield in a read head.

Claims

1. A method of forming a tunnel barrier layer in a tunneling magnetoresistive (TMR) sensor, comprising:

(a) depositing a first Mg layer on a ferromagnetic layer;

(b) performing a natural oxidation (NOX) process on said first Mg layer to form a MgO layer thereon; and

(c) depositing a second Mg layer on said MgO layer.

2. The method of claim 1 wherein said ferromagnetic layer is a first ferromagnetic layer and the method is further comprised of depositing a second ferromagnetic layer on said second Mg layer.

3. The method of claim 2 wherein the first and second Mg layers and the first and second ferromagnetic layers are deposited by a DC sputtering process in one or more chambers of a sputtering system.

4. The method of claim 3 wherein the NOX process is performed in an oxidation chamber of said sputtering system, said oxidation chamber is different than said one or more chambers of the sputtering system.

5. The method of claim 1 wherein the NOX process is performed in an oxidation chamber with an oxygen pressure between about 0.1 mTorr and 1 Torr for a period of about 15 to 300 seconds.

6. The method of claim 1 wherein the first Mg barrier has a thickness of about 4 to 14 Angstroms and the second Mg layer has a thickness from about 2 to 8 Angstroms.

7. The method of claim 1 wherein the TMR sensor is formed on a bottom shield in a magnetic read head and is comprised of a stack of layers in which a seed layer, an anti-ferromagnetic (AFM) layer, a pinned layer, said barrier layer, a free layer, and a cap layer are sequentially formed on the bottom shield.

8. The method of claim 1 wherein the first Mg layer is deposited on a ferromagnetic layer that is a synthetic anti-parallel (SyAP) pinned layer having an AP2/Ru/AP1 configuration wherein the AP2 layer is made of CoFe and the AP1 layer is comprised of Co_1-X—

YFe_XB_Y having a thickness from about 10 to 80 Angstroms wherein x is from about 5 to 95 atomic % and y is from about 5 to 30 atomic %.

9. The method of claim 7 wherein said free layer is Co_1-WFe_W/Ni_1-ZFe_Z wherein w is from about 10 to 90 atomic % and z is from about 5 to 70 atomic % or is a multilayered structure of alloys comprised of at least two of the elements Co, Fe, Ni, and B.

10. The method of claim 7 wherein the seed layer is Ta/Ru, Ta, Ta/NiCr, Ta/Cu, or Ta/Cr and the AFM layer is one of IrMn, MnPt, NiMn, OsMn, RuMn, RhMn, PdMn, RuRhMn, or MnPtPd.

11. A method of forming a TMR sensor in a magnetic device, comprising:

(a) depositing a first Mg layer on a ferromagnetic layer;

(b) forming a MgO layer on said first Mg layer; and

(c) depositing a second Mg layer on said MgO layer to form a Mg/MgO/Mg tunnel barrier layer.

12. The method of claim 11 wherein the MgO layer is formed by a rf-sputtering or reactive sputtering process.

13. The method of claim 11 wherein the MgO layer is formed by a NOX process comprising an oxygen pressure between about 0.1 mTorr and 1 Torr for a period of about 15 to 300 seconds, said NOX process partially oxidizes the first Mg layer.

14. The method of claim 11 wherein the ferromagnetic layer, first Mg layer, and second Mg layer are deposited by a DC sputtering process.

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

(a) a ferromagnetic layer; and

(b) a tunnel barrier layer formed on said ferromagnetic layer, said tunnel barrier layer is comprised of a lower Mg layer, a middle MgO layer, and an upper Mg layer.

16. The TMR sensor of claim 15 wherein said ferromagnetic layer is a SyAP pinned layer having an AP2/Ru/AP1 configuration wherein the AP2 layer is made of CoFe, and the AP1 layer is about 10 to 80 Angstroms thick and is comprised of Co_1-X—

YFe_XB_Y wherein x is from about 5 to 95 atomic % and y is from about 5 to 30 atomic %, said TMR sensor is further comprised of a free layer formed on said upper Mg layer.

17. The TMR sensor of claim 15 wherein said ferromagnetic layer is a SyAP pinned layer having an AP2/Ru/AP1 configuration wherein the AP2 layer is made of CoFe, and the AP1 layer has a multilayer structure comprised of CoFeB/Co_1-VFe_V wherein v is from about 10 to 90 atomic % and the thickness of the Co_1-VFe_V layer is from about 5 to 20 Angstroms.

18. The TMR sensor of claim 16 wherein the free layer is comprised of Co_1-WFe_W/Ni_1-ZFe_Z wherein w is from about 10 to 90 atomic % and z is from about 5 to 70 atomic % or is a multilayered structure of alloys comprised of at least two of the elements Co, Fe, Ni, and B.

19. The TMR sensor of claim 15 wherein the first Mg barrier has a thickness of about 4 to 14 Angstroms and the second Mg layer has a thickness from about 2 to 8 Angstroms.

20. The TMR sensor of claim 15 wherein the MgO layer has a thickness that is adjusted to provide a MR ratio of at least 34% and a RA value of about 2 ohm-um².

21. The TMR sensor of claim 15 wherein said magnetic device is a MRAM or read head and the TMR sensor has a bottom spin valve configuration in which a Ta/Ru seed layer, IrMn AFM layer, CoFe/Ru/CoFeB pinned (ferromagnetic) layer, said barrier layer, a CoFe/NiFe free layer, and a cap layer are sequentially formed on a substrate.