Engineered magnetic layer with improved perpendicular anisotropy using glassing agents for spintronic applications

• US 8,710,603 B2
• Filed: 02/29/2012
• Issued: 04/29/2014
• 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
• Primary Examiner(s): Vu, David
• Assistant Examiner(s): FOX, BRANDON C
• Application Number:
  US13/408,555
• Publication Number:
  US 20130221459A1
• Time in Patent Office: 790 Days
• Field of Search: 257/421, 257/441, 438/3
• US Class Current: 257/421
• 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

Abstract

A magnetic element 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 (MTJ). The free layer may be a single layer or a composite and is comprised of one or more glassing agents that have a first concentration in a middle portion thereof and a second concentration less than the first concentration in regions near first and second interfaces. As a result, a CoFeB free layer, for example, 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. The magnetic element may be part of a spintronic device or serve as a propagation medium in a domain wall motion device.

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 first glassing agent concentration in a middle portion thereof and a second glassing agent concentration less than the first glassing agent concentration but greater than zero 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 glassing agent (G) is one or more of Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg to inhibit crystallization and maintain an amorphous character in the middle portion of the ferromagnetic layer.

3. 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 a glassing agent (G) with a concentration of about 1% to 30% in the ferromagnetic layer.

4. The MTJ element of claim 3 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 and 30 Angstroms.

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

6. 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.

7. 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.

8. The MTJ element of claim 7 wherein the perpendicular Hk enhancing layer is embedded with magnetic particles of an alloy of one or more of Co, Fe, Ni, and B.

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 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.

11. The MTJ element of claim 10 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.

12. The MTJ element of claim 11 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.

13. The MTJ element of claim 12 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.

14. The MTJ element of claim 11 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.

15. 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.

16. 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 first glassing agent concentration in a middle portion of the free layer and a second glassing agent concentration less than the first glassing agent concentration but greater than zero 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.

17. The domain wall motion device of claim 16 wherein the glassing agent(G) is one or more of Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg to inhibit crystallization and maintain an amorphous character in the middle portion of the free layer.

18. The domain wall motion device of claim 17 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 a glassing agent (G) with a concentration of about 1% to 30% in the free layer.

19. The domain wall motion device of claim 17 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 and 30 Angstroms.

20. The domain wall motion device of claim 17 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.

21. The domain wall motion device of claim 20 wherein the perpendicular Hk enhancing layer is embedded with magnetic particles of an alloy of one or more of Co, Fe, Ni, and B.

22. The domain wall motion device of claim 17 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.

23. The domain wall motion device of claim 17 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.

24. The domain wall motion device of claim 17 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.

25. The domain wall motion device of claim 16 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.

26. The domain wall motion device of claim 16 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.

27. 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 first glassing agent concentration in a middle portion thereof that crystallizes at a first temperature, and a second glassing agent concentration less than the first concentration but greater than zero 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.

28. The method of claim 27 wherein the anneal process is performed at a temperature that is less than the first temperature and greater than the second temperature.

29. The method of claim 27 wherein the glassing agent (G) is one or more of Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg, and is formed with a concentration between about 1% and 30% in the free layer.

30. The method of claim 29 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.

31. The method of claim 27 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 and 30 Angstroms.

32. The method of claim 27 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.

33. 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 first glassing agent (G) made of Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg, and a second glassing agent (B) wherein a first concentration of glassing agents (G+B) in a middle portion of the ferromagnetic layer is greater than a second concentration of glassing agents (G+B) in portions of the ferromagnetic layer proximate to the first and second interfaces; and

(c) the perpendicular Hk enhancing layer.

34. The MTJ element of claim 33 wherein the first glassing agent has a greater concentration in the middle portion of the ferromagnetic layer than in portions proximate to the first and second interfaces.

35. The MTJ element of claim 33 wherein the second glassing agent begins to diffuse within the ferromagnetic layer at a temperature of about 240°

C., and the first glassing agent begins to diffuse within the ferromagnetic layer at a temperature of about 400°

C.

36. 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 has a magnetic alloy/G/magnetic alloy configuration wherein a glassing agent (G) made of Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg has a first concentration in the G layer and a second concentration less than the first concentration in the alloy portions of the ferromagnetic layer proximate to the first and second interfaces, the glassing agent is deposited as a single layer or as a laminate wherein each glassing agent layer is from 0.1 to 5 Angstroms thick; and

(c) the perpendicular Hk enhancing layer.

37. The MTJ of claim 36 wherein the magnetic alloy layers are comprised of one or more of Co, Fe, Ni, and B.

38. 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 magnetic alloy/G/magnetic alloy configuration and 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 (G) made of Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg with a first concentration in the middle G layer and with a second concentration less than the first concentration in the magnetic alloy portions of the free layer proximate to the first and second interfaces, the glassing agent is deposited as a single layer or as a laminate wherein each glassing agent layer is from 0.1 to 5 Angstroms thick, 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.

39. The domain wall motion device of claim 38 wherein the magnetic alloy layers are comprised of one or more of Co, Fe, Ni, and B.

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

(a) providing the tunnel barrier layer formed on a substrate;

(b) depositing the ferromagnetic 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 ferromagnetic layer has a magnetic alloy/G/magnetic alloy configuration with a middle layer made of a glassing agent that is Si, Ta, P, Nb, Hf, Ti, Pd, Be, Cr, Zr, Cu, Os, V, or Mg with a first concentration that crystallizes at a first temperature, and wherein the magnetic alloy layers have a second glassing agent concentration less than the first concentration that crystallize at a second temperature less than the first temperature, and 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;

(c) forming the perpendicular Hk enhancing layer on the ferromagnetic layer; and

(d) performing an anneal process.

41. The method of claim 40 wherein the anneal process is performed at a temperature that is less than the first temperature and greater than the second temperature.