TMR device with novel free layer structure

• US 8,456,781 B2
• Filed: 07/30/2012
• Issued: 06/04/2013
• Est. Priority Date: 02/01/2010
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated
• Original Assignee: Headway Technologies Incorporated
• Inventors: Zhao, Tong, Wang, Hui-Chuan, Li, Min, Zhang, Kunliang
• Primary Examiner(s): Klimowicz, Will J
• Application Number:
  US13/561,206
• Publication Number:
  US 20130001189A1
• Time in Patent Office: 309 Days
• Field of Search: 360324-3242, 148/108, 148/121, 296/030.7, 296/030.8, 296/031.3, 296/031.4
• US Class Current: 360/324.12
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• 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 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• CPC Class Codes: G11B 5/3163 Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers
• CPC Class Codes: G11B 5/3906 Details related to the use of magnetic thin film layers or to their effects
• 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 41/303 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 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials
• CPC Class Codes: Y10T 29/49034 Treating to affect magnetic properties
• CPC Class Codes: Y10T 29/49052 by etching

Abstract

A composite free layer having a FL1/insertion/FL2 configuration where a top surface of FL1 is treated with a weak plasma etch is disclosed for achieving enhanced dR/R while maintaining low RA, and low λ in TMR or GMR sensors. The weak plasma etch removes less than about 0.2 Angstroms of FL1 and is believed to modify surface structure and possibly increase surface energy. FL1 may be CoFe, CoFe/CoFeB, or alloys thereof having a (+) λ value. FL2 may be CoFe, NiFe, or alloys thereof having a (−) λ value. The thin insertion layer includes at least one magnetic element such as Co, Fe, and Ni, and at least one non-magnetic element. When CoFeBTa is selected as insertion layer, the CoFeB:Ta ratio is from 1:1 to 4:1.

Claims

1. A method of forming a magnetoresistive element in a TMR sensor, comprising:

(a) forming a seed layer on a substrate;

(b) depositing a first ferromagnetic layer (FL2) on the seed layer, said (FL2) layer has an inner surface contacting the seed layer, an outer surface facing away from the seed layer, and is comprised of one or more of Co_WFe_(100-W) where w is from 0 to about 100 atomic %, Ni_ZFe_(100-Z) where z is from about 70% to 100%, and an alloy wherein CoFe or NiFe are combined with one or more elements selected from Ni, Ta, Mn, Ti, W, Zr, Hf, Tb, Nb, and B;

(c) performing a weak plasma etch treatment (PT) on the outer surface of said first ferromagnetic layer (FL2) thereby forming a modified (FL2) layer that has one or both of a modified surface structure and increased surface energy with respect to other portions of the (FL2) layer;

(d) sequentially depositing an insertion layer (INS) and a second ferromagnetic layer (FL1) on the modified surface of the first ferromagnetic layer (FL2) to give a composite free layer with a (FL2)(PT)/(INS)/(FL1) configuration, said insertion layer has at least one magnetic element selected from Fe, Co, and Ni and at least one non-magnetic element selected from Ta, Ti, W, Zr, Hf, Nb, Mo, V, Mg, and Cr, and said second ferromagnetic layer is comprised of one or more of Co_WFe_(100-W), [Co_WFe_(100-W)]_(100-Y)B_Y where w is from 0 to about 100% and y is from 10 atomic % to about 40 atomic %, and an alloy of Co_WFe_(100-W), or [Co_WFe_(100-W)]_(100-Y)B_Y that is comprised of one or more additional elements including Ni, Ta, Mn, Ti, W, Zr, Hf, Tb, and Nb;

(e) sequentially forming a non-magnetic spacer, pinned layer, and antiferromagnetic (AFM) layer on the (FL1) layer; and

(f) forming a capping layer on the AFM layer.

2. The method of claim 1 wherein the non-magnetic spacer is a tunnel barrier layer that is comprised of one or more of MgO, MgZnO, ZnO, Al₂O₃, TiOx, AlTiO, HfOx and ZrOx.

3. The method of claim 2 wherein the tunnel barrier is comprised of MgO and wherein formation of the MgO tunnel barrier layer is comprised of depositing a first Mg layer, performing a natural oxidation process to form a MgO layer, and then depositing a second Mg layer on the MgO layer.

4. The method of claim 1 further comprised of performing an annealing step after step (f) wherein the annealing conditions comprise a temperature between about 240°

C. and 340°

C. with an applied magnetic field of at least 2000 Oe for about 2 to 10 hours.

5. The method of claim 1 wherein the second ferromagnetic layer has a thickness from about 2 to 40 Angstroms and is comprised CoFeB, CoFe/CoFeB, or CoFe/CoFeB/CoFe.

6. The method of claim 1 wherein the insertion layer has a thickness from about 2 to 10 Angstroms and is further comprised of B to give a CoFeBTa composition wherein the ratio of CoFeB to Ta is from about 1:

1 to 4;

1.

7. The method of claim 1 wherein the insertion layer has a CoTa composition wherein the ratio of Co to Ta is from about 1:

1 to 4;

1.

8. The method of claim 1 wherein the first ferromagnetic layer has a thickness from about 2 to 50 Angstroms and is comprised of CoFe, NiFe, or CoFe/NiFe/CoFe.

9. The method of claim 1 wherein the weak plasma etch comprises Ar or another inert gas at a pressure greater than about 0.01 Torr and with a power less than about 20 Watts.

10. The method of claim 1 further comprised of performing a weak plasma etch treatment (PT) on a top surface of the second ferromagnetic layer (FL1) prior to depositing the non-magnetic spacer.