TMR device with low magnetostriction free layer

• US 20090122450A1
• Filed: 11/08/2007
• Published: 05/14/2009
• Est. Priority Date: 11/08/2007
• Status: Abandoned Application

• Current Assignee: Headway Technologies Incorporated
• Original Assignee: Headway Technologies Incorporated
• Inventors: Zhang, Kunliang, Li, Min, Wang, Hui-Chuan, Zhao, Tong
• Application Number:
  US11/983,329
• Publication Number:
  US 20090122450A1
• Time in Patent Office: Days
• US Class Current: 360/324.200
• 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 comprised of CoB_X with a λ between −5×10⁻⁶ and 0 on a MgO_X tunnel barrier. Optionally, a FeCo/CoB_X free layer configuration may be used where x is about 1 to 30 atomic %. Trilayer configurations represented by FeCo/CoFeB/CoB_X, FeCo/CoB_X/CoFeB, FeCo_Y/CoFe_W/CoB_X, or FeCo_Y/FeB/CoB_X 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 substituted for CoBx in the aforementioned embodiments. A 15 to 30% in improvement in TMR ratio over a conventional CoFe/NiFe free layer is achieved while maintaining a low Hc and RA<3 ohm-um². In bilayer or trilayer embodiments, λ between −5×10⁻⁶ and 5×10⁻⁶ is achieved by combining CoBx (−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 MgOx on the pinned layer;

(c) a free layer comprised of CoB_X or FeB_V formed on the tunnel barrier layer where x and v are from about 1 to 30 atomic %; and

(d) a capping layer on the free layer.

2. The magnetoresistive element of claim 1 wherein said free layer is a single layer comprised of CoB_X or FeB_V with a thickness from about 20 to 60 Angstroms.

3. The magnetoresistive element of claim 1 wherein the free layer has a bilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer and an upper CoB_X layer having a λ

between about −

5×

10<sup>−

6</sup> and 0, said FeCo_Y layer has a thickness between about 2 and 10 Angstroms and said CoB_X layer has a thickness between about 20 and 50 Angstroms.

4. The magnetoresistive element of claim 1 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle Co_UFe_WB_Z layer having a thickness of about 5 to 20 Angstroms 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 an upper CoB_X layer having a λ

between about −

5×

10<sup>−

6</sup> and 0, said lower FeCo layer has a thickness between about 2 and 10 Angstroms and said upper CoB_X layer has a thickness between about 20 and 40 Angstroms.

5. The magnetoresistive element of claim 1 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle CoB_X layer having a λ

from about −

5×

10<sup>−

6</sup> to 0, and an upper Co_UFe_WB_Z layer having a thickness of about 5 to 20 Angstroms 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 %, said lower FeCo_Y layer has a thickness between about 2 and 10 Angstroms, and said middle CoB_X layer is between about 20 to 40 Angstroms thick.

6. The magnetoresistive element of claim 1 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle CoFe_W layer where w is from 0 to 100 atomic % and is unequal to y, and an upper CoB_X layer, said lower FeCo_Y and middle CoFe_W layers each have a thickness between about 2 and 10 Angstroms and said upper CoB_X layer has a thickness from about 20 to 40 Angstroms.

7. The magnetoresistive element of claim 1 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % and having a thickness of about 2 to 10 Angstroms formed on the tunnel barrier layer, a middle FeB_v layer having a thickness of about 2 to 10 Angstroms, and an upper CoB_X layer with a thickness from about 20 to 40 Angstroms.

8. 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 MgOx on the pinned layer;

(c) a free layer comprised of Co_PNi_RFe_SB_T or CoNiFeBM formed on the tunnel barrier layer wherein p is from about 5 to 90 atomic %, r is from about 5 to 20 atomic %, s is between about 5 and 90 atomic %, t is from about 1 to 30 atomic %, and p+r+s+t=100 atomic %, and M is one of V, Ti, Zr, Nb, Hf, Ta, or Mo; and

(d) a capping layer on the free layer.

9. The magnetoresistive element of claim 8 wherein said free layer is a single layer comprised of Co_PNi_RFe_SB_T or CoNiFeBM with a thickness from about 20 to 60 Angstroms, and M has a content of <

10 atomic % in the CoNiFeBM alloy.

10. The magnetoresistive element of claim 8 wherein the free layer has a bilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer and an upper Co_PNi_RFe_SB_T or CoNiFeBM layer, said FeCo_Y layer has a thickness between about 2 and 10 Angstroms and said Co_PNi_RFe_SB_T or CoNiFeBM layer has a thickness between about 20 and 50 Angstroms.

11. The magnetoresistive element of claim 8 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle Co_UFe_WB_Z layer having a thickness of about 5 to 20 Angstroms 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 an upper Co_PNi_RFe_SB_T or CoNiFeBM layer, said lower FeCo layer has a thickness between about 2 and 10 Angstroms and said upper Co_PNi_RFe_SB_T or CoNiFeBM layer has a thickness between about 20 and 40 Angstroms.

12. The magnetoresistive element of claim 8 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle Co_PNi_RFe_SB_T or CoNiFeBM layer, and an upper Co_UFe_WB_Z layer 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 %.

13. The magnetoresistive element of claim 8 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle CoFe_W layer where w is from 0 to 100 atomic % and is unequal to y, and an upper Co_PNi_RFe_SB_T or CoNiFeBM layer.

14. The magnetoresistive element of claim 8 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle FeB_V layer, and an upper Co_PNi_RFe_SB_T or CoNiFeBM layer.

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

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

(b) forming a tunnel barrier layer on said pinned layer by depositing a first Mg layer on the pinned layer, performing a natural oxidation process to form a MgOx layer, and then depositing a second Mg layer on the MgOx layer;

(c) forming a free layer on the MgOx tunnel barrier layer, said free layer is comprised of CoB_X or FeB_V where x and v are from about 1 to 30 atomic %; and

(d) forming a capping layer on the free layer.

16. The method of claim 15 wherein the free layer has a bilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer and an upper CoB_X layer having a k between about −

5×

10<sup>−

6</sup> and 0, said FeCo_Y layer has a thickness between about 2 and 10 Angstroms and said CoB_X layer has a thickness between about 20 and 50 Angstroms.

17. The method of claim 15 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle Co_UFe_WB_Z layer having a thickness of about 5 to 20 Angstroms 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 an upper CoB_X layer having a λ

between about −

5×

10<sup>−

6</sup> and 0, said lower FeCo layer has a thickness between about 2 and 10 Angstroms and said upper CoB_X layer has a thickness between about 20 and 40 Angstroms

18. The method of claim 15 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % formed on the tunnel barrier layer, a middle CoFe_W layer where w is from 0 to 100 atomic % and w is unequal to y, and an upper CoB_X layer having a λ

between about −

5×

10<sup>−

6</sup> and 0, said lower FeCoy and middle CoFe_W layers each have a thickness between about 2 and 10 Angstroms and said upper CoB_X layer has a thickness from about 20 to 40 Angstroms.

19. The method of claim 15 wherein the free layer has a trilayer configuration with a lower FeCo_Y layer where y is from 0 to 100 atomic % and having a thickness of about 2 to 10 Angstroms formed on the tunnel barrier layer, a middle FeB_V layer having a thickness of about 2 to 10 Angstroms, and an upper CoB_X layer with a λ

between about −

5×

10<sup>−

6</sup> and 0 and a thickness from about 20 to 40 Angstroms.

20. A method of forming a free layer in a TMR sensor in a magnetic device, comprising:

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

(b) forming a tunnel barrier layer on said pinned layer by depositing a first Mg layer on the pinned layer, performing a natural oxidation process to form a MgOx layer, and then depositing a second Mg layer on the MgOx layer;

(c) forming a free layer comprised of Co_PNi_RFe_SB_T or CoNiFeBM on the tunnel barrier layer wherein p is from about 5 to 90 atomic %, r is from about 5 to 20 atomic %, s is between about 5 and 90 atomic %, t is from about 1 to 30 atomic %, and p+r+s+t=100 atomic %, and M is one of V, Ti, Zr, Nb, Hf, Ta, or Mo; and

(d) forming a capping layer on the free layer.