TMR device with novel free layer

• US 20100073828A1
• Filed: 09/22/2008
• Published: 03/25/2010
• Est. Priority Date: 09/22/2008
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated (TDK Corporation)
• Original Assignee: Headway Technologies Incorporated (TDK Corporation)
• Inventors: Zhang, Kunliang, Li, Min, Wang, Hui-Chuan, Zhao, Tong
• Granted Patent: US 8,747,629 B2
• Time in Patent Office: Days
• US Class Current: 360/324.120
• 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 magnetoresistive element in a magnetic device, comprising:

(a) a synthetic anti-parallel (SyAP) pinned layer;

(b) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface opposite the first surface that contacts a free layer; and

(c) a composite free layer with a FL1/FL2/FL3 configuration, comprising;

(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;

(2) a FL2 layer formed on the FL1 layer and comprising (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 comprises Co_(100-Z)B_Z where z is 10 to 40 atomic %, a composite structure represented by (CoB/CoFe)_n where n is ≧

1 or (CoB/CoFe)_m/CoB where m is ≧

1, or a CoBQ alloy where Q is one of Ni, Mn, Tb, W, Hf, Zr, Nb, or Si.

2. The magnetoresistive element of claim 1 wherein the FL1 layer has a thickness between about 2 and 15 Angstroms.

3. The magnetoresistive element of claim 1 wherein M in the CoFeM alloy is one of Ni, Mn, Tb, W, Hf, Zr, Nb, Si, and B.

4. The magnetoresistive element of claim 1 wherein the tunnel barrier layer is comprised of MgO, MgZnO, ZnO, Al₂O₃, TiOx, AlTiO, HfOx, ZrOx, or a combination of two or more of the aforementioned materials.

5. The magnetoresistive element 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.

6. The magnetoresistive element of claim 1 wherein the FL2 layer thickness is between about 2 and 10 Angstroms.

7. The magnetoresistive element of claim 1 wherein the FL3 layer comprises Co_(100-Z)B_Z and has a thickness from about 10 to 100 Angstroms.

8. The magnetoresistive element of claim 1 wherein the FL3 layer comprises CoB/CoFe and said CoB layer has a thickness from about 10 to 100 Angstroms, and said CoFe layer has a thickness between about 2 and 10 Angstroms.

9. The magnetoresistive element of claim 1 wherein the FL3 layer comprises (CoB/CoFe)_n where n is ≧

2 or (CoB/CoFe)_m/CoB where m is ≧

1, 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.

10. 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/coupling/AP1 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;

(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 comprises Co_(100-Z)B_Z where z is 10 to 40 atomic %, a composite structure represented by (CoB/CoFe)_n where n is ≧

1 or (CoB/CoFe)_m/CoB where m is ≧

1, or a CoBQ alloy where Q is one of Ni, Mn, Tb, W, Hf, Zr, Nb, or Si.

11. The method of claim 10 further comprised of forming a capping layer on the FL3 layer.

12. The method of claim 10 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.

13. The method of claim 10 wherein M in the CoFeM alloy is one of Ni, Mn, Tb, W, Hf, Zr, Nb, Si, and B.

14. The method of claim 10 wherein the tunnel barrier is comprised of MgO, MgZnO, ZnO, Al₂O₃, TiOx, AlTiO, HfOx, ZrOx, or a combination of two or more of the aforementioned materials.

15. The method of claim 14 wherein said tunnel barrier is comprised of MgO and is formed by sputter depositing a first Mg layer on said AP1 layer, performing a natural oxidation process to yield a MgO layer, and then sputter depositing a second Mg layer on the MgO layer.

16. The method of claim 10 wherein the FL3 layer comprises Co_(100-Z)B_Z and has a thickness from about 10 to 100 Angstroms.

17. The method of claim 10 wherein the FL3 layer comprises CoB/CoFe and said CoB layer has a thickness from about 10 to 100 Angstroms, and said CoFe layer has a thickness between about 2 and 10 Angstroms.

18. The method of claim 10 wherein the FL3 layer comprises (CoB/CoFe)_n where n is ≧

2 or (CoB/CoFe)_m/CoB 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.

19. The method of claim 10 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.

20. The method of claim 10 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.