Low resistance tunneling magnetoresistive sensor with natural oxidized double MgO barrier

• US 8,337,676 B2
• Filed: 08/05/2010
• Issued: 12/25/2012
• Est. Priority Date: 11/16/2005
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated
• Original Assignee: Headway Technologies Incorporated
• Inventors: Zhao, Tong, Zhang, Kunliang, Wang, Hui Chuan, Chen, Yu-Hsia, Li, Min
• Primary Examiner(s): MCDONALD, RODNEY GLENN
• Application Number:
  US12/806,082
• Publication Number:
  US 20100320076A1
• Time in Patent Office: 873 Days
• Field of Search: 204/192.2, 204/192.22
• US Class Current: 204/192.2
• 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 pinned layer by a DC sputtering process in a first chamber which is a sputter deposition chamber, said first Mg layer contacts the ferromagnetic pinned layer;

(b) performing a natural oxidation (NOX) process at an ambient temperature on said first Mg layer in a second chamber which is an oxidation chamber to form a MgO layer thereon;

(c) depositing a second Mg layer on said MgO layer by a DC sputtering process in a the first sputter deposition chamber; and

(d) depositing a free layer on said second Mg layer in the first sputter deposition chamber;

said free layer contacts the second Mg layer.

2. The method of claim 1 further comprised of an annealing process following the free layer deposition, said annealing process comprises a temperature range of about 250°

C. to 300°

C. with an applied magnetic field of about 8000 Oe for about 2 to 10 hours.

3. The method of claim 2 wherein the tunnel barrier layer becomes a uniform MgO layer as a result of the annealing process.

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

(a) sequentially forming a seed layer, anti-ferromagnetic (AFM) layer, and a pinned layer on a substrate;

(b) depositing a first Mg layer on said pinned layer by a DC sputtering process in a first chamber, said first Mg layer contacts the pinned layer;

(c) forming a MgO layer on said first Mg layer by a natural oxidation process at an ambient temperature in a second chamber;

(d) depositing a second Mg layer on said MgO layer by a DC sputtering process in the first chamber to form a Mg/MgO/Mg tunnel barrier layer; and

(e) sequentially forming a free layer and a cap layer on the Mg/MgO/Mg tunnel barrier layer in the first chamber, said free layer contacts the second Mg layer.

5. The method of claim 4 further comprised of an annealing process following the cap layer deposition, said annealing process comprises a temperature range of about 250°

C. to 300°

C. with an applied magnetic field of about 8000 Oe for about 2 to 10 hours.

6. The method of claim 5 wherein the tunnel barrier layer becomes a uniform MgO layer as a result of the annealing process.