TMR device with novel free layer

• US 8,747,629 B2
• Filed: 09/22/2008
• Issued: 06/10/2014
• Est. Priority Date: 09/22/2008
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated
• Original Assignee: Headway Technologies Incorporated
• Inventors: Wang, Hui-Chuan, Zhao, Tong, Li, Min, Zhang, Kunliang
• Primary Examiner(s): King, Roy
• Assistant Examiner(s): WU, JENNY R
• Application Number:
  US12/284,454
• Publication Number:
  US 20100073828A1
• Time in Patent Office: 2,087 Days
• Field of Search: 204/192.1, 306/324.2, 428811-8113, 360/324.2
• 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: 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 5/33 Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing onlySingle head using magnetic domains for scanning G11B5/4946; multiple head for scanning G11B5/4907 and subgroups ; general details therefor G11B5/133 - G11B5/255
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/3929 Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect

Abstract

A TMR sensor with a free layer having a FL1/FL2/FL3 configuration is disclosed in which FL1 is FeCo or a FeCo alloy with a thickness between 2 and 15 Angstroms. The FL2 layer is made of CoFeB or a CoFeB alloy having a thickness from 2 to 10 Angstroms. The FL3 layer is from 10 to 100 Angstroms thick and has a negative λ to offset the positive λ from FL1 and FL2 layers and is comprised of CoB or a CoBQ alloy where Q is one of Ni, Mn, Tb, W, Hf, Zr, Nb, and Si. Alternatively, the FL3 layer may be a composite such as CoB/CoFe, (CoB/CoFe)_n where n is ≧2 or (CoB/CoFe)_m/CoB where m is ≧1. The free layer described herein affords a high TMR ratio above 60% while achieving low values for λ (<5×10⁻⁶), RA (1.5 ohm/μm²), and Hc (<6 Oe).

Claims

1. A method of forming a sensor element in a magnetic device, comprising:

(a) sequentially forming a stack of layers comprised of a seed layer, anti-ferromagnetic (AFM) layer, and a SyAP pinned layer having an AP2 layer/coupling layer/AP1 layer configuration on a substrate wherein the AP2 layer contacts said AFM layer;

(b) forming a tunnel barrier having a first surface that contacts said AP1 layer and a second surface opposite the first surface;

(c) forming a composite free layer having a FL1/FL2/FL3 configuration on the tunnel barrier, said composite free layer is comprised of;

(1) a FL1 layer contacting the second surface of the tunnel barrier layer, said FL1 layer comprises Fe_(100-X)Co_X where x is from 0 to 100 atomic %, or a FeCoM alloy where M is one of Ni, Mn, Tb, W, Hf, Zr, Nb, Si, or B;

(2) a FL2 layer formed on the FL1 layer, said FL2 layer comprises (Co_100-VFe_V)_100-YB_Y where v is 10 to 70 atomic %, and y is from 5 to 40 atomic %, or a CoFeB alloy; and

(3) a FL3 layer disposed on the FL2 layer, said FL3 layer is a composite structure represented by (CoB/CoFe)_n where n is ≧

1 or (CoB/CoFe)_m/CoB where m is ≧

1.

2. The method of claim 1 wherein the FL3 layer has a CoB/CoFe/CoB/CoFe configuration, and each of said CoFe layers has a thickness between about 2 and 10 Angstroms.

3. The method of claim 1 wherein the FL3 layer comprises CoB and CoFe layers formed in an alternating fashion in a (CoB/CoFe)_n structure where n is ≧

1 or in a (CoB/CoFe)_m/CoB structure where m is ≧

1, and said CoB layers have a combined thickness from about 10 to 100 Angstroms, and each of said CoFe layers has a thickness between about 2 and 10 Angstroms.

4. The method of claim 1 wherein the FL1 layer has a thickness between about 2 and 15 Angstroms and the FL2 layer has a thickness between about 2 and 10 Angstroms.

5. The method of claim 1 further comprised of performing an anneal process comprising an applied magnetic field of about 8000 to 13000 Oe and a temperature between about 250°

C. and 270°

C. for a period of about 2 to 5 hours.

6. The method of claim 1 wherein the CoFeB alloy in the FL2 layer is represented by CoFeBQ where Q is one of Ni, Mn, Tb, W, Hf, Zr, Nb, and Si.