Engineered Magnetic Layer with Improved Perpendicular Anisotropy using Glassing Agents for Spintronic Applications

• US 20130221460A1
• Filed: 07/13/2012
• Published: 08/29/2013
• Est. Priority Date: 02/29/2012
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Headway Technologies Incorporated
• Inventors: Jan, Guenole, Wang, Yu-Jen, Tong, Ru-Ying
• Granted Patent: US 8,698,260 B2
• Time in Patent Office: Days
• US Class Current: 257/421
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• 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 10/3259 Spin-exchange-coupled multilayers comprising at least a nanooxide layer [NOL], e.g. with a NOL spacer
• CPC Class Codes: H01F 10/3286 Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
• CPC Class Codes: H01F 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A magnetic element in a spintronic device or serving as a propagation medium in a domain wall motion device is disclosed wherein first and second interfaces of a free layer with a perpendicular Hk enhancing layer and tunnel barrier, respectively, produce enhanced surface perpendicular anisotropy to increase thermal stability in a magnetic tunnel junction. The free layer may be a single layer or a composite and is comprised of a glassing agent that has a first concentration in a middle portion thereof and a second concentration less than the first concentration in regions near first and second interfaces. A CoFeB free layer selectively crystallizes along first and second interfaces but maintains an amorphous character in a middle region containing a glass agent providing the annealing temperature is less than the crystallization temperature of the middle region.

Claims

1. A magnetic tunnel junction (MTJ) element including a ferromagnetic layer with at least two interfaces that produce interfacial perpendicular anisotropy, comprising:

(a) a tunnel barrier layer;

(b) the ferromagnetic layer that has a first interface with said tunnel barrier layer and a second interface with a perpendicular Hk enhancing layer formed on a surface of the ferromagnetic layer that is opposite a surface adjoining the tunnel barrier layer, the ferromagnetic layer comprises a glassing agent (G) made of Mo or W and having a first concentration in a middle portion thereof and a second concentration less than the first concentration in portions of the ferromagnetic layer proximate to the first and second interfaces; and

(c) the perpendicular Hk enhancing layer.

2. The MTJ element of claim 1 wherein the first concentration of glassing agent inhibits crystallization and maintains an amorphous character in the middle portion of the ferromagnetic layer.

3. The MTJ element of claim 1 wherein a glassing agent content incrementally increases from the second concentration at the first and second interfaces to the first concentration in the middle portion of the ferromagnetic layer.

4. The MTJ element of claim 1 wherein the glassing agent (G) is deposited as a single layer or as a laminated configuration wherein each glassing agent layer is from 0.1 to 5 Angstroms thick.

5. The MTJ element of claim 1 wherein the ferromagnetic layer is a composite of a plurality of layers in which one or more layers contain a glassing agent (G) and the layers adjoining the first and second interfaces have a smaller concentration of glassing agent (G) than a layer proximate to a middle of the ferromagnetic layer.

6. The MTJ element of claim 2 wherein the ferromagnetic layer is comprised of an alloy of one or more of Co, Fe, and Ni, or an alloy of one or more of Co, Fe, Ni, and B, and is doped with the glassing agent (G) having a concentration of about 1% to 30% in the ferromagnetic layer.

7. The MTJ element of claim 6 wherein the ferromagnetic layer is a single layer or a laminated stack of layers comprised of an alloy of one or more of Co, Fe, Ni, and B with a thickness between about 5 and 30 Angstroms, or is an alloy of one or more of Co, Fe, and Ni with a thickness from about 5 to 30 Angstroms.

8. The MTJ element of claim 1 wherein the perpendicular Hk enhancing layer is comprised of an oxide, a nitride, or a lamination of oxide and/or nitride layers of one or more of Si, Ba, Ca, La, Mn, Zn, Hf, Ta, Ti, B, Cu, Cr, V, Mg, and Al, or is one of Ta, Ti, B, Ag, Au, Cu, Cr, Nb, Zr, V, Mg, or Al.

9. The MTJ element of claim 1 wherein the tunnel barrier layer is made of an oxide or nitride of one or more of Si, Ti, Ba, Ca, La, Mn, V, Al, Ti, Zn, Hf, Mg, Ta, Ti, B, Cu, and Cr.

10. The MTJ element of claim 8 wherein the perpendicular Hk enhancing layer is embedded with magnetic particles of an alloy of one or more of Co, Fe, Ni, and B.

11. The MTJ element of claim 1 wherein the interfacial perpendicular anisotropy dominates a shape anisotropy field of the ferromagnetic layer such that a magnetization direction is oriented out of the plane of the ferromagnetic layer.

12. The MTJ element of claim 11 wherein the ferromagnetic layer is a free layer and the magnetization direction of the free layer determines a “

1”

or “

0”

magnetic state in a memory device.

13. The MTJ element of claim 1 wherein a top surface of the MTJ element is connected to one or more other adjacent MTJ elements by one or more wires to form an array thereby enabling one or more of the MTJ elements to be selectively written to or read during a write process or read process, respectively.

14. The MTJ element of claim 12 further comprised of a seed layer, pinned layer, and a capping layer in a bottom spin valve configuration wherein the seed layer, pinned layer, tunnel barrier layer, free layer, perpendicular Hk enhancing layer, and the capping layer are sequentially formed on a substrate.

15. The MTJ element of claim 12 further comprised of a seed layer, pinned layer, and a capping layer in a top spin valve configuration wherein the seed layer, perpendicular Hk enhancing layer, free layer, tunnel barrier layer, pinned layer, and the capping layer are sequentially formed on a substrate.

16. The MTJ element of claim 14 wherein the pinned layer has an interface with the tunnel barrier layer and an interface with the seed layer, there is a first concentration of glassing agent in a middle portion of the pinned layer and a second concentration of glassing agent in portions of the pinned layer proximate to the interfaces with the tunnel barrier layer and seed layer.

17. A domain wall motion device, comprising:

(a) a pinned magnetic layer having a first width;

(b) a tunnel barrier contacting a top surface of the pinned layer;

(c) a free layer having a width substantially larger than the first width, and forming a first interface with the tunnel barrier layer and a second interface with a perpendicular Hk enhancing layer formed on a surface of the free layer that is opposite a surface at the first interface, there is a glassing agent made of Mo or W with a first concentration in a middle portion of the free layer and a second concentration less than the first concentration in portions of the free layer proximate to the first and second interfaces, and wherein domain walls extend vertically between first and second interfaces to establish magnetic domains including a switchable magnetic domain aligned above the pinned magnetic layer;

(d) the perpendicular Hk enhancing layer; and

(e) a capping layer that contacts a top surface of the perpendicular Hk enhancing layer, the domain wall motion device is electrically connected to a current/voltage source and to a readout device to enable read and write processes.

18. The domain wall motion device of claim 17 wherein the glassing agent (G) inhibits crystallization and maintains an amorphous character in the middle portion of the free layer.

19. The domain wall motion device of claim 17 wherein a glassing agent content incrementally increases from the second concentration at the first and second interfaces to the first concentration in the middle portion of the free layer.

20. The domain wall motion device of claim 17 wherein the glassing agent (G) is deposited as a single layer or as a laminated configuration wherein each glassing agent layer is from 0.1 to 5 Angstroms thick.

21. The domain wall motion device of claim 17 wherein the free layer is a composite of a plurality of layers in which one or more layers contain a glassing agent (G) and the layers adjoining the first and second interfaces have a smaller concentration of glassing agent (G) than that of a layer proximate to a middle of the free layer.

22. The domain wall motion device of claim 18 wherein the free layer is comprised of an alloy of one or more of Co, Fe, and Ni, or an alloy of one or more of Co, Fe, Ni, and B, and is doped with the glassing agent (G) with a concentration of about 1% to 30% in the free layer.

23. The domain wall motion device of claim 18 wherein the free layer is a single layer or a laminated stack of layers comprised of an alloy of one or more of Co, Fe, Ni, and B with a thickness between about 5 and 30 Angstroms, or is an alloy of one or more of Co, Fe, and Ni with a thickness from about 5 to 30 Angstroms.

24. The domain wall motion device of claim 18 wherein the perpendicular Hk enhancing layer is comprised of an oxide, a nitride, or a lamination of oxide and/or nitride layers of one or more of Si, Ba, Ca, La, Mn, Zn, Hf, Ta, Ti, B, Cu, Cr, V, Mg, and Al, or is one of Ta, Ti, B, Ag, Au, Cu, Cr, Nb, Zr, V, Mg, or Al.

25. The domain wall motion device of claim 18 wherein the tunnel barrier layer is made of an oxide or nitride of one or more of Si, Ti, Ba, Ca, La, Mn, V, Al, Ti, Zn, Hf, Mg, Ta, Ti, B, Cu, and Cr.

26. The domain wall motion device of claim 24 wherein the perpendicular Hk enhancing layer is embedded with magnetic particles of an alloy of one or more of Co, Fe, Ni, and B.

27. The domain wall motion device of claim 18 wherein the interfacial perpendicular anisotropy dominates a shape anisotropy field of the free layer such that a magnetization direction is oriented out of the plane of the free layer.

28. The domain wall motion device of claim 18 wherein a top surface thereof is connected to one or more other adjacent domain wall motion devices by one or more wires to form an array thereby enabling one or more of the domain wall motion devices to be selectively written to or read during a write process or read process, respectively.

29. A method of forming a MTJ element exhibiting interfacial perpendicular anisotropy at a first interface between a free layer and an adjoining tunnel barrier layer and at a second interface between the free layer and an adjoining perpendicular Hk enhancing layer, comprising:

(a) providing a pinned layer formed on a substrate;

(b) forming a tunnel barrier layer on the pinned layer;

(c) depositing a free layer having a bottom surface that forms a first interface with a top surface of said tunnel barrier, and having a top surface that forms a second interface with a subsequently deposited perpendicular Hk enhancing layer, the free layer comprises a glassing agent made of Mo or W with a first concentration in a middle portion thereof that crystallizes at a first temperature, and a second glassing agent concentration less than the first concentration in top and bottom portions of the ferromagnetic layer proximate to the first and second interfaces such that the top and bottom portions crystallize at a second temperature less than the first temperature;

(d) forming the perpendicular Hk enhancing layer on the free layer;

(e) forming a capping layer that contacts a top surface of the perpendicular Hk enhancing layer; and

(f) performing an anneal process.

30. The method of claim 29 wherein the anneal process is performed at a temperature that is less than the first temperature and greater than the second temperature.

31. The method of claim 29 wherein the glassing agent (G) is formed with a concentration between about 1% and 30% in the free layer.

32. The method of claim 31 wherein the glassing agent (G) is deposited as a single layer or as a laminated configuration in which each glassing agent layer is from 0.1 to 5 Angstroms thick.

33. The method of claim 31 wherein the free layer is a composite with a plurality of layers wherein one or more layers contain the glassing agent (G) and the layers adjoining the first and second interfaces have a smaller concentration of glassing agent (G) than that of a layer proximate to a middle of the free layer.

34. The method of claim 29 wherein the free layer is a single layer or a laminated stack of layers comprised of an alloy of one or more of Co, Fe, Ni, and B with a thickness between about 5 and 30 Angstroms, or is an alloy of one or more of Co, Fe, and Ni with a thickness from about 5 to 30 Angstroms.

35. The method of claim 29 wherein the perpendicular Hk enhancing layer is comprised of an oxide, a nitride, or a lamination of oxide and/or nitride layers of one or more of Si, Ba, Ca, La, Mn, Zn, Hf, Ta, Ti, B, Cu, Cr, V, Mg, and Al, or is one of Ta, Ti, B, Ag, Au, Cu, Cr, Nb, Zr, V, Mg, or Al.