Magnetic Tunnel Junctions Using Amorphous Materials as Reference and Free Layers

• US 20060098354A1
• Filed: 11/10/2004
• Published: 05/11/2006
• Est. Priority Date: 11/10/2004
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Parkin, Stuart Stephen Papwoth
• Granted Patent: US 7,351,483 B2
• Time in Patent Office: Days
• US Class Current: 360/324.2
• 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: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1121 Multilayer
• CPC Class Codes: Y10T 428/115 Magnetic layer composition
• CPC Class Codes: Y10T 428/1193 with interlaminar component [e.g., adhesion layer, etc.]

Abstract

Magnetic tunnel junctions are constructed from a MgO or Mg—ZnO tunnel barrier and amorphous magnetic layers in proximity with, and on respective sides of, the tunnel barrier. The amorphous magnetic layer preferably includes Co and at least one additional element selected to make the layer amorphous, such as boron. Magnetic tunnel junctions formed from the amorphous magnetic layers and the tunnel barrier have tunneling magnetoresistance values of up to 200% or more.

Claims

1. A structure, comprising:

a first amorphous magnetic layer including material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;

a second amorphous magnetic layer including material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;

at least one tunnel barrier selected from the group of tunnel barriers consisting of MgO and Mg—

ZnO, wherein the tunnel barrier is located between the first amorphous magnetic layer and the second amorphous magnetic layer; and

an antiferromagnetic layer that exchange biases the second amorphous magnetic layer, wherein the first amorphous magnetic layer, the second amorphous magnetic layer, and the tunnel barrier are in proximity with each other, thereby enabling spin-polarized current to pass between the first and second amorphous magnetic layers through the tunnel barrier.

2. The structure of claim 1, wherein the antiferromagnetic layer includes at least one of IrMn and PtMn.

3. The structure of claim 1, wherein the thickness of the antiferromagnetic layer is between 75 and 300 angstroms.

4. The structure of claim 1, wherein the tunnel barrier is (100) oriented.

5. The structure of claim 1, wherein each of the first and second amorphous magnetic layers includes Co and at least one additional element selected to make the layer amorphous.

6. The structure of claim 1, wherein each of the first and second amorphous magnetic layers includes an alloy of Co and Fe.

7. The structure of claim 1, wherein at least one of the first and second magnetic layers includes B to make it amorphous.

8. The structure of claim 7, wherein the B content is between 10 and 30 atomic percent.

9. The structure of claim 7, wherein the B content is between 10 and 25 atomic percent.

10. The structure of claim 7, wherein the B content is between 15 and 20 atomic percent.

11. The structure of claim 1, wherein at least one of the first and second amorphous magnetic layers includes an alloy of Co, Fe, and B.

12. The structure of claim 11, wherein the Co to Fe ratio is chosen so that the alloy would form a bcc-crystal structure in the absence of B.

13. The structure of claim 1, wherein each of the first and second amorphous magnetic layers includes an alloy of Co, Fe, and B.

14. The structure of claim 1, comprising a magnetic, crystalline interface layer between the tunnel barrier and one of the amorphous layers.

15. The structure of claim 14, wherein the magnetic crystalline interface layer includes an alloy of Co and Fe.

16. The structure of claim 1, comprising:

a first magnetic crystalline layer between and in contact with both the tunnel barrier and the first amorphous magnetic layer; and

a second magnetic crystalline layer between and in contact with both the tunnel barrier and the second amorphous magnetic layer.

17. The structure of claim 16, wherein each of the magnetic crystalline layers includes an alloy of Co and Fe.

18. The structure of claim 1, further comprising:

a capping layer over the first amorphous magnetic layer; and

a substrate under the antiferromagnetic layer.

19. The structure of claim 1, wherein the tunnel barrier is in contact with each of the first and second amorphous magnetic layers.

20. The structure of claim 1, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 50% at room temperature.

21. The structure of claim 1, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 100% at room temperature.

22. The structure of claim 1, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 160% at room temperature.

23. The structure of claim 1, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 200% at room temperature.

24. The structure of claim 1, wherein at least one of the first and second magnetic layers includes an element to make it amorphous, the element being selected from group consisting of Zr, Hf, and Si.

25. The structure of claim 1, wherein the tunnel barrier is crystalline.

26. The structure of claim 25, wherein the tunnel barrier includes polycrystalline grains.

27. A structure, comprising:

a first amorphous magnetic layer;

a second amorphous magnetic layer;

at least one tunnel barrier selected from the group of tunnel barriers consisting of MgO and Mg—

ZnO, wherein the tunnel barrier is located between the first amorphous magnetic layer and the second amorphous magnetic layer, and wherein the first amorphous magnetic layer, the second amorphous magnetic layer, and the tunnel barrier are in proximity with each other, thereby enabling spin-polarized current to pass between the first and second amorphous magnetic layers through the tunnel barrier;

an additional magnetic layer in proximity with the second amorphous magnetic layer; and

an antiferromagnetic coupling layer that couples the second amorphous magnetic layer and the additional magnetic layer, wherein the additional magnetic layer, the antiferromagnetic coupling layer, and the second amorphous magnetic layer form a synthetic antiferromagnet reference layer.

28. The structure of claim 27, further comprising an antiferromagnetic layer in proximity with the synthetic antiferromagnetic layer.

29. The structure of claim 28, wherein the antiferromagnetic layer includes at least one of IrMn and PtMn.

30. The structure of claim 27, wherein the antiferromagnetic coupling layer includes Ru.

31. The structure of claim 27, wherein the antiferromagnetic coupling layer includes Os.

32. The structure of claim 27, wherein the antiferromagnetic coupling layer includes at least one alloy from the group consisting of Ru alloys and Os alloys.

33. The structure of claim 27, wherein the additional magnetic layer includes an alloy of Co and Fe.

34. The structure of claim 33, wherein the additional magnetic layer includes amorphous magnetic material.

35. The structure of claim 33, wherein the Fe concentration of the additional magnetic layer is between 10 and 30 percent.

36. The structure of claim 27, wherein the tunnel barrier is (100) oriented.

37. The structure of claim 27, wherein each of the first and second amorphous magnetic layers includes Co and at least one additional element selected to make the layer amorphous.

38. The structure of claim 27, wherein each of the first and second amorphous magnetic layers includes an alloy of Co and Fe.

39. The structure of claim 27, wherein at least one of the first and second magnetic layers includes B to make it amorphous.

40. The structure of claim 39, wherein the B content is between 10 and 30 atomic percent.

41. The structure of claim 39, wherein the B content is between 10 and 25 atomic percent.

42. The structure of claim 39, wherein the B content is between 15 and 20 atomic percent.

43. The structure of claim 27, wherein at least one of the first and second amorphous magnetic layers includes an alloy of Co, Fe, and B.

44. The structure of claim 43, wherein the Co to Fe ratio is chosen so that the alloy would form a bcc-crystal structure in the absence of B.

45. The structure of claim 27, wherein each of the first and second amorphous magnetic layers includes an alloy of Co, Fe, and B.

46. The structure of claim 27, comprising a magnetic, crystalline interface layer between the tunnel barrier and one of the amorphous layers.

47. The structure of claim 46, wherein the magnetic crystalline interface layer includes an alloy of Co and Fe.

48. The structure of claim 27, comprising:

a first magnetic crystalline layer between and in contact with both the tunnel barrier and the first amorphous magnetic layer; and

a second magnetic crystalline layer between and in contact with both the tunnel barrier and the second amorphous magnetic layer.

49. The structure of claim 48, wherein each of the magnetic crystalline layers includes an alloy of Co and Fe.

50. The structure of claim 27, further comprising:

a capping layer over the first amorphous magnetic layer; and

a substrate under the synthetic antiferromagnet reference layer.

51. The structure of claim 27, wherein the tunnel barrier is in contact with each of the first and second amorphous magnetic layers.

52. The structure of claim 27, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 50% at room temperature.

53. The structure of claim 27, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 100% at room temperature.

54. The structure of claim 27, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 160% at room temperature.

55. The structure of claim 27, wherein the first amorphous magnetic layer, the tunnel barrier, and the second amorphous magnetic layer form a magnetic tunnel junction having a tunnel magnetoresistance of at least 200% at room temperature.

56. The structure of claim 27, wherein at least one of the first and second magnetic layers includes an element to make it amorphous, the element being selected from group consisting of Zr, Hf, and Si.

57. The structure of claim 27, wherein the tunnel barrier is crystalline.

58. The structure of claim 27, wherein the tunnel barrier includes polycrystalline grains.

59. The structure of claim 27, wherein the additional magnetic layer includes an alloy of at least one of Co, Ni, and Fe.

60. A method, comprising:

forming a tunnel barrier selected from the group of tunnel barriers consisting of MgO and Mg—

ZnO;

forming first and second amorphous ferromagnetic layers by depositing Co and at least one other element on respective underlayers, wherein the amorphous layers and the tunnel barrier are formed in proximity to one another to permit spin-polarized current to pass between the first and second amorphous layers through the tunnel barrier, thereby forming a magnetic tunnel junction; and

forming in proximity with the second amorphous layer at least one of the following;

i) an antiferromagnetic layer that exchange biases the second amorphous magnetic layer, and

ii) an additional magnetic layer and an antiferromagnetic coupling layer in proximity with the second amorphous magnetic layer, so that the additional magnetic layer, the coupling layer, and the second amorphous magnetic layer form a synthetic antiferromagnet reference layer, wherein the coupling layer couples the second amorphous magnetic layer and the additional magnetic layer.

61. The method of claim 60, wherein said at least one other element includes B.

62. The method of claim 60, wherein said at least one other element includes Zr.

63. The method of claim 60, wherein said at least one other element includes Hf.

64. The method of claim 60, wherein the amorphous ferromagnetic layers include respective thin crystalline layers that are in contact with the tunnel barrier.

65. The method of claim 60, wherein the tunnel barrier is (100) oriented.

66. The method of claim 60, comprising annealing the junction to improve its tunneling magnetoresistance.

67. The method of claim 66, wherein the junction is annealed at a temperature selected to yield a tunnel magnetoresistance of greater than 50% at room temperature.

68. The method of claim 66, wherein the junction is annealed at a temperature selected to yield a tunnel magnetoresistance of greater than 100% at room temperature.

69. The method of claim 66, wherein the junction is annealed at a temperature selected to yield a tunnel magnetoresistance of greater than 200% at room temperature.

70. The method of claim 66, wherein the junction is annealed at a temperature greater than 300°

C.

71. The method of claim 66, wherein the junction is annealed at a temperature greater than 340°

C.

72. The method of claim 66, wherein the junction is annealed at a temperature in the range of 300°

C. to 400°

C.

73. The method of claim 60, wherein the tunnel barrier includes a MgO tunnel barrier.

74. The method of claim 73, wherein the MgO tunnel barrier is formed by:

depositing Mg onto a surface of an underlayer to form a Mg layer thereon, wherein the surface is selected to be substantially free of oxide; and

directing additional Mg, in the presence of oxygen, towards the Mg layer to form a MgO tunnel barrier in contact with the oxide-free underlayer, the oxygen reacting with the additional Mg and the Mg layer.

75. The method of claim 60, wherein the tunnel barrier includes a Mg—

ZnO tunnel barrier.

76. A method of claim 75, wherein the Mg—

ZnO tunnel barrier is formed by;

depositing a metal layer onto a surface of an underlayer, wherein the surface is selected to be substantially free of oxide; and

directing additional metal towards the metal layer, in the presence of oxygen, to form a magnesium-zinc oxide tunnel barrier in contact with the oxide-free underlayer, the oxygen reacting with the additional metal and the metal layer, wherein;

at least one of the metal layer and the additional metal includes Zn, and

at least one of the metal layer and the additional metal includes Mg.

77. The method of claim 60, wherein at least one of the amorphous ferromagnetic layers is formed directly on the tunnel barrier.

78. The method of claim 60, wherein the tunnel barrier is formed directly on one of the amorphous ferromagnetic layers.