Spin-transfer switching magnetic element utilizing a composite free layer comprising a superparamagnetic layer

• US 8,362,580 B2
• Filed: 12/08/2009
• Issued: 01/29/2013
• Est. Priority Date: 12/08/2009
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chen, Wei-Chuan, Kang, Seung H.
• Primary Examiner(s): NGUYEN, CUONG QUANG
• Application Number:
  US12/632,952
• Publication Number:
  US 20110133298A1
• Time in Patent Office: 1,148 Days
• Field of Search: 257/295, 257421-422, 257/E43.001, 257/E43.006
• US Class Current: 257/421
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

A system and method for forming a magnetic tunnel junction (MTJ) storage element utilizes a composite free layer structure. The MTJ element includes a stack comprising a pinned layer, a barrier layer, and a composite free layer. The composite free layer includes a first free layer, a superparamagnetic layer and a nonmagnetic spacer layer interspersed between the first free layer and the superparamagnetic layer. A thickness of the spacer layer controls a manner of magnetic coupling between the first free layer and the superparamagnetic layer.

Claims

1. A magnetic tunnel junction (MTJ) storage element comprising:

a stack comprising a pinned layer and a barrier layer; and

a composite free layer formed on the barrier layer, comprising a first free layer, a nonmagnetic spacer layer and a superparamagnetic layer, such that the spacer layer is interspersed between the first free layer and the superparamagnetic layer.

2. The MTJ storage element of claim 1, further comprising an interlayer exchange coupling between the first free layer and the superparamagnetic layer.

3. The MTJ storage element of claim 2, wherein a magnetic polarization of the first free layer is aligned parallel to a magnetic polarization of the superparamagnetic layer.

4. The MTJ storage element of claim 2, wherein a magnetic polarization of the first free layer is aligned anti-parallel to a magnetic polarization of the superparamagnetic layer.

5. The MTJ storage element of claim 1, further comprising an interlayer fringe coupling between the first free layer and the superparamagnetic layer.

6. The MTJ storage element of claim 5, wherein a magnetic polarization of the first free layer is aligned anti-parallel to a magnetic polarization of the superparamagnetic layer.

7. The MTJ storage element of claim 1, wherein the superparamagnetic layer is formed from a ferromagnetic layer of reduced thickness.

8. The MTJ storage element of claim 1, wherein the superparamagnetic layer is formed from an antiferromagnetic layer of reduced thickness.

9. The MTJ storage element of claim 1, wherein the superparamagnetic layer is formed from a nonmagnetic material doped with ferromagnetic elements.

10. The MTJ storage element of claim 1, wherein the superparamagnetic layer is formed from a ferromagnetic material doped with nonmagnetic elements.

11. The MTJ storage element of claim 1, wherein the superparamagnetic layer is formed from a laminated structure comprising one or more layers of ferromagnetic elements, interspersed with one or more layers of nonmagnetic elements.

12. The MTJ storage element of claim 1, further comprising an antiferromagnetic material in contact with the pinned layer, formed below the pinned layer.

13. The MTJ storage element of claim 1, wherein the pinned layer is a pinned layer stack comprising two or more layers.

14. The MTJ storage element according to claim 1, wherein the storage element is applied in an electronic device, selected from the group consisting of a set top box, music player, video player, entertainment unit, navigation device, communications device, personal digital assistant (PDA), fixed location data unit, and a computer, into which the MTJ storage element is integrated.

15. The MTJ storage element according to claim 1, wherein the storage element is integrated in a Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM).

16. The STT-MRAM device according to claim 15, wherein the STT-MRAM device is integrated in at least one semiconductor die.

17. A method of forming a magnetic tunnel junction (MTJ) storage element, the method comprising:

forming a stack comprising a pinned layer and a barrier layer; and

forming a composite free layer on top of the barrier layer comprising a first free layer, a nonmagnetic spacer layer and a superparamagnetic layer, such that the spacer layer is interspersed between the first free layer and the superparamagnetic layer.

18. The method of claim 17, further comprising coupling the first free layer and the superparamagnetic layer via interlayer exchange coupling.

19. The method of claim 18, wherein a magnetic polarization of the first free layer is aligned parallel to a magnetic polarization of the superparamagnetic layer.

20. The method of claim 18, wherein a magnetic polarization of the first free layer is aligned anti-parallel to a magnetic polarization of the superparamagnetic layer.

21. The method of claim 17, further comprising:

coupling the first free layer the superparamagnetic layer via interlayer fringe coupling.

22. The method of claim 21, wherein a magnetic polarization of the first free layer is aligned anti-parallel to a magnetic polarization of the superparamagnetic layer.

23. The method of claim 17, wherein the superparamagnetic layer is formed by reducing the thickness of a ferromagnetic or antiferromagnetic layer.

24. The method of claim 17, wherein the superparamagnetic layer is formed by doping a nonmagnetic material with ferromagnetic elements.

25. The method of claim 17, wherein the superparamagnetic layer is formed by doping a ferromagnetic material with nonmagnetic elements.

26. The method of claim 17, wherein the superparamagnetic layer is formed by interspersing one or more layers of nonmagnetic elements with one or more layers of ferromagnetic elements.

27. The method according to claim 17, wherein the MTJ storage element is applied in an electronic device, selected from the group consisting of a set top box, music player, video player, entertainment unit, navigation device, communications device, personal digital assistant (PDA), fixed location data unit, and a computer, into which the MTJ storage element is integrated.

28. The method according to claim 17, wherein the MTJ storage element is integrated in a Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM).

29. A magnetic tunnel junction (MTJ) storage element comprising:

a first magnetic means for holding a first polarization;

a composite magnetic means for holding a second polarization comprising

ferromagnetic means;

superparamagnetic means; and

nonmagnetic means interspersed between the ferromagnetic means and the superparamagnetic means, wherein a thickness of the nonmagnetic means controls a manner of coupling between the ferromagnetic means and the superparamagnetic means; and

insulating means interspersed between the first magnetic means and composite magnetic means to enable a flow of tunneling current between the first magnetic means and the composite magnetic means.

30. The MTJ storage element of claim 29, wherein the manner of coupling between the ferromagnetic means and the superparamagnetic means is interlayer exchange coupling.

31. The MTJ storage element of claim 30, wherein a magnetic polarization of the ferromagnetic means is aligned parallel to a magnetic polarization of the superparamagnetic means.

32. The MTJ storage element of claim 30, wherein a magnetic polarization of the ferromagnetic means is aligned anti-parallel to a magnetic polarization of the superparamagnetic means.

33. The MTJ storage element of claim 29, wherein the manner of coupling between the ferromagnetic means and the superparamagnetic means is interlayer fringe coupling.

34. The MTJ storage element of claim 33, wherein a magnetic polarization of the ferromagnetic means is aligned anti-parallel to a magnetic polarization of the superparamagnetic means.

35. The MTJ storage element of claim 29, wherein the superparamagnetic means is formed from a ferromagnetic or anti-ferromagnetic material of reduced thickness.

36. The MTJ storage element of claim 29, wherein the superparamagnetic means is formed from a nonmagnetic material doped with ferromagnetic elements.

37. The MTJ storage element of claim 29, wherein the superparamagnetic means is formed from a ferromagnetic material doped with nonmagnetic elements.

38. The MTJ storage element of claim 29, wherein the superparamagnetic means is formed from a laminated structure comprising one or more layers of ferromagnetic elements, interspersed with one or more layers of nonmagnetic elements.

39. The MTJ storage element according to claim 29, wherein the MTJ storage element is applied in an electronic device, selected from the group consisting of a set top box, music player, video player, entertainment unit, navigation device, communications device, personal digital assistant (PDA), fixed location data unit, and a computer, into which the MTJ storage element is integrated.

40. The MTJ storage element according to claim 29, wherein the MTJ storage element is integrated in a Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM).

41. A method of forming a magnetic tunnel junction (MTJ) storage element, the method comprising:

step for forming a stack comprising a pinned layer and a barrier layer; and

step for forming a composite free layer on top of the barrier layer comprising a first free layer, a nonmagnetic spacer layer and a superparamagnetic layer, such that the spacer layer is interspersed between the first free layer and the superparamagnetic layer.

42. The method of claim 41, further comprising coupling the first free layer and the superparamagnetic layer via interlayer exchange coupling.

43. The method of claim 42, wherein a magnetic polarization of the first free layer is aligned parallel to a magnetic polarization of the superparamagnetic layer.

44. The method of claim 42, wherein a magnetic polarization of the first free layer is aligned anti-parallel to a magnetic polarization of the superparamagnetic layer.

45. The method of claim 41, further comprising coupling the first free layer the superparamagnetic layer via interlayer fringe coupling.

46. The method of claim 45, wherein a magnetic polarization of the first free layer is aligned anti-parallel to a magnetic polarization of the superparamagnetic layer.

47. The method of claim 41, wherein the superparamagnetic layer is formed by reducing the thickness of a ferromagnetic or antiferromagnetic layer.

48. The method of claim 41, wherein the superparamagnetic layer is formed by doping a nonmagnetic material with ferromagnetic elements.

49. The method of claim 41, wherein the superparamagnetic layer is formed by doping a ferromagnetic material with nonmagnetic elements.

50. The method of claim 41, wherein the superparamagnetic layer is formed by interspersing one or more layers of nonmagnetic elements with one or more layers of ferromagnetic elements.

51. The method according to claim 41, wherein the MTJ storage element is applied in an electronic device, selected from the group consisting of a set top box, music player, video player, entertainment unit, navigation device, communications device, personal digital assistant (PDA), fixed location data unit, and a computer, into which the MTJ storage element is integrated.

52. The method according to claim 41, wherein the MTJ storage element is integrated in a Spin Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM).