TMR device with low magnetorestriction free layer

• US 8,472,151 B2
• Filed: 04/11/2012
• Issued: 06/25/2013
• Est. Priority Date: 11/08/2007
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated (TDK Corporation)
• Original Assignee: Headway Technologies Incorporated (TDK Corporation)
• Inventors: Wang, Hui-Chuan, Zhao, Tong, Li, Min, Zhang, Kunliang
• Primary Examiner(s): Haley, Joseph
• Assistant Examiner(s): POLO, GUSTAVO D
• Application Number:
  US13/444,497
• Publication Number:
  US 20120193738A1
• Time in Patent Office: 440 Days
• Field of Search: 360313-328
• US Class Current: 360/324.12
• 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 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/18 Measuring magnetostrictive properties
• CPC Class Codes: G11B 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• 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: G11B 5/3912 Arrangements in which the active read-out elements are transducing in association with active magnetic shields, e.g. magnetically coupled shields G11B5/3916 takes precedence
• 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: 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: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect

Abstract

A high performance TMR sensor is fabricated by employing a free layer with a trilayer configurations represented by FeCo/CoFeB/CoB, FeCo/CoB/CoFeB, FeCo/CoFe/CoB, or FeCo/FeB/CoB may also be employed. Alternatively, CoNiFeB or CoNiFeBM formed by co-sputtering CoB with CoNiFe or CoNiFeM, respectively, where M is V, Ti, Zr, Nb, Hf, Ta, or Mo may be included in a composite free layer or as a single free layer in the case of CoNiFeBM. A 15 to 30% in improvement in TMR ratio over a conventional CoFe/NiFe free layer is achieved while maintaining low Hc and RA<3 ohm-um². In bilayer or trilayer embodiments, magnetostriction (λ) between −5×10⁻⁶ and 5×10⁻⁶ is achieved by combining CoB (−λ) and one or more layers having a positive λ.

Claims

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

(a) a stack of layers comprised of a seed layer, anti-ferromagnetic (AFM) layer, and a pinned layer sequentially formed on a substrate;

(b) a tunnel barrier layer made of MgO on the pinned layer;

(c) a free layer having a trilayer configuration with a lower Fe or FeCo layer formed on the tunnel barrier layer, and a stack formed on the Fe or FeCo layer consisting of a first layer made of FeB, Co, CoFe wherein the Fe content is unequal to a Fe content in the FeCo layer, or Co_UFe_WB_Z where u is from about 1 to 95 atomic %, w is from 0 to about 70 atomic %, and z is from about 1 to 30 atomic %, and a second layer that is CoB_X with a magnetostriction (λ

) between about −

5×

10<sup>−

6</sup> and 0; and

(d) a capping layer on the free layer.

2. The magnetoresistive element of claim 1 wherein the first layer is Co_UFe_WB_Z with a thickness of about 5 to 20 Angstroms that contacts a top surface of the FeCo_Y layer, the lower FeCo_Y layer has a thickness between about 2 and 10 Angstroms, and the CoB_X layer is the uppermost layer in the trilayer configuration and has a thickness between about 20 and 40 Angstroms.

3. The magnetoresistive element of claim 1 wherein the CoB_X layer contacts a top surface of the FeCo_Y layer and has thickness from about 20 to 40 Angstroms, the lower FeCo_Y layer has a thickness between about 2 and 10 Angstroms, and the first layer that is Co_UFe_WB_Z is the uppermost layer in the trilayer configuration and has a thickness of about 5 to 20 Angstroms.

4. The magnetoresistive element of claim 1 wherein the lower FeCo_Y layer and the first layer that is a CoFe_V layer each have a thickness between about 2 and 10 Angstroms, and the CoB_X layer is the uppermost layer in the trilayer configuration and has a thickness from about 20 to 40 Angstroms.

5. The magnetoresistive element of claim 1 wherein the lower FeCo_Y layer has a thickness of about 2 to 10 Angstroms, the first layer is FeB with a thickness of about 2 to 10 Angstroms, and the CoB_X layer has a thickness from about 20 to 40 Angstroms and is the uppermost layer in the trilayer configuration.