Multilayers having reduced perpendicular demagnetizing field using moment dilution for spintronic applications

• US 20120280336A1
• Filed: 05/04/2011
• Published: 11/08/2012
• Est. Priority Date: 05/04/2011
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: MagIC Technologies Inc (TDK Corporation)
• Inventors: Jan, Guenole, Tong, Ru Ying, Kula, Witold
• Granted Patent: US 8,592,927 B2
• Time in Patent Office: Days
• 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: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A magnetic element is disclosed that has a composite free layer with a FM1/moment diluting/FM2 configuration wherein FM1 and FM2 are magnetic layers made of one or more of Co, Fe, Ni, and B and the moment diluting layer is used to reduce the perpendicular demagnetizing field. As a result, lower resistance x area product and higher thermal stability are realized when perpendicular surface anisotropy dominates shape anisotropy to give a magnetization perpendicular to the planes of the FM1, FM2 layers. The moment diluting layer may be a non-magnetic metal like Ta or a CoFe alloy with a doped non-magnetic metal. A perpendicular Hk enhancing layer interfaces with the FM2 layer and may be an oxide to increase the perpendicular anisotropy field in the FM2 layer. 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 element comprising a stack of layers including a composite free layer with at least two interfaces that produce interfacial perpendicular anisotropy, comprising:

(a) a tunnel barrier layer;

(b) the composite free layer having a FM1/moment diluting layer/FM2 configuration wherein the first ferromagnetic (FM1) layer has a first interface with the tunnel barrier layer and the second ferromagnetic (FM2) layer has a second interface with a perpendicular Hk enhancing layer, the first and second interfaces produce interfacial perpendicular anisotropy in the adjoining FM1 and FM2 layers, respectively; and

(c) the perpendicular Hk enhancing layer.

2. The magnetic element of claim 1 wherein the FM1 and FM2 layers are made of an Fe rich alloy with one or more of Co, Ni, and B, or are a Co rich alloy with one or more of Fe, Ni, and B.

3. The magnetic element of claim 2 wherein each of the FM1 and FM2 layers have a thickness from about 5 to 20 Angstroms.

4. The magnetic element of claim 1 wherein the moment diluting layer is non-magnetic and is one or more of Ta, Al, Si, B, V, Ti, Mg, Hf, Cr, Cu, Ag, and Au.

5. The magnetic element of claim 1 wherein the moment diluting layer is an alloy of two or more of Co, Ni, and Fe that is doped with one or more of Ta, Al, Si, V, B, Ti, Mg, Hf, Cr, Cu, Ag, Au, or Os wherein the dopant metal content is between 5 and 50 atomic % in the alloy.

6. The magnetic element of claim 1 wherein the perpendicular Hk enhancing layer is MgO, SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, or HfOx, or one of Ru, Ta, Ti, B, V, Mg, Ag, Au, Cu or Cr.

7. The magnetic element of claim 6 further comprised of magnetic particles made of one or more of Fe, Co, Ni, and B embedded in the perpendicular Hk enhancing layer.

8. The magnetic element of claim 1 wherein the interfacial perpendicular anisotropy dominates a shape anisotropy in the FM1 and FM2 layers and thereby causes the magnetization in both of the FM1 and FM2 layers to be oriented perpendicular to the planes of the FM1 and FM2 layers.

9. The magnetic element of claim 1 wherein the tunnel barrier layer is comprised of MgO, AlOx, TiOx, or HfOx, or is a laminate of one or more of the aforementioned oxides.

10. The magnetic element of claim 1 wherein the magnetic element is part of a magnetic tunnel junction (MTJ) and an array of said MTJs is used for digital storage in a MRAM, spin transfer MRAM, or another spintronic device.

11. A magnetic tunnel junction with a bottom spin valve configuration, comprising:

(a) a seed layer formed on a substrate;

(b) a pinned layer formed on the seed layer;

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

(d) a composite free layer having a FM1/moment diluting layer/FM2 configuration wherein the first ferromagnetic (FM1) layer has a first interface with the tunnel barrier layer and the second ferromagnetic (FM2) layer has a second interface with a bottom surface of a perpendicular Hk enhancing layer, the first and second interfaces produce interfacial perpendicular anisotropy in the adjoining FM1 and FM2 layers, respectively;

(e) the perpendicular Hk enhancing layer; and

(f) a capping layer that contacts a top surface of the perpendicular Hk enhancing layer.

12. The magnetic tunnel junction of claim 11 wherein the FM1 and FM2 layers each have a thickness from about 5 to 20 Angstroms and are made of an Fe rich alloy with one or more of Co, Ni, and B, or are a Co rich alloy with one or more of Fe, Ni, and B.

13. The magnetic tunnel junction of claim 11 wherein the moment diluting layer is non-magnetic and is one or more of Ta, Al, Si, B, V, Ti, Mg, Hf, Cr, Cu, Ag, and Au.

14. The magnetic tunnel junction of claim 11 wherein the moment diluting layer is an alloy of two or more of Co, Ni, and Fe that is doped with one or more of Ta, Al, Si, V, B, Ti, Mg, Hf, Cr, Cu, Ag, Au, or Os wherein the dopant metal content is between 5 and 50 atomic % in the alloy.

15. The magnetic tunnel junction of claim 11 wherein the perpendicular Hk enhancing layer is a single layer or a laminate comprised of one or more oxides selected from MgO, SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, and HfOx, and has a resistance x area (RA) value less than a RA value of the tunnel barrier layer.

16. The magnetic tunnel junction of claim 15 further including magnetic particles comprised of one or more of Fe, Co, Ni, and B that are embedded in the perpendicular Hk enhancing layer.

17. The magnetic tunnel junction of claim 16 wherein the tunnel barrier layer and perpendicular Hk enhancing layer are both comprised of MgO and the capping layer is made of Ru.

18. A magnetic tunnel junction with a top spin valve configuration, comprising:

(a) a seed layer formed on a substrate;

(b) a perpendicular Hk enhancing layer formed on the seed layer;

(c) a composite free layer having a FM2/moment diluting layer/FM1 configuration wherein the first ferromagnetic (FM1) layer has an interface with a bottom surface of a tunnel barrier layer and the second ferromagnetic (FM2) layer has an interface with a top surface of the perpendicular Hk enhancing layer, the interfaces produce interfacial perpendicular anisotropy in the adjoining FM1 and FM2 layers, respectively;

(d) the tunnel barrier;

(e) a pinned layer formed on the tunnel barrier layer; and

(f) a capping layer as the uppermost layer in the top spin valve configuration.

19. The magnetic tunnel junction of claim 18 wherein the FM1 and FM2 layers each have a thickness from about 5 to 20 Angstroms and are made of an Fe rich alloy with one or more of Co, Ni, and B, or are a Co rich alloy with one or more of Fe, Ni, and B.

20. The magnetic tunnel junction of claim 18 wherein the moment diluting layer is non-magnetic and is one or more of Ta, Al, Si, B, V, Ti, Mg, Hf, Cr, Cu, Ag, and Au.

21. The magnetic tunnel junction of claim 18 wherein the moment diluting layer is an alloy of two or more of Co, Ni, and Fe that is doped with one or more of Ta, Al, Si, V, B, Ti, Mg, Hf, Cr, Cu, Ag, Au, or Os wherein the dopant metal content is between 5 and 50 atomic % in the alloy.

22. The magnetic tunnel junction of claim 18 wherein the perpendicular Hk enhancing layer is a single layer or a laminate comprised of one or more oxides selected from MgO, SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, and HfOx, and has a resistance x area (RA) value less than a RA value of the tunnel barrier layer.

23. The magnetic tunnel junction of claim 22 further including magnetic particles comprised of one or more of Fe, Co, Ni, and B that are embedded in the perpendicular Hk enhancing layer.

24. The magnetic tunnel junction of claim 22 wherein the seed layer has a free energy of oxide formation substantially greater than that of the oxide selected for the perpendicular Hk enhancing layer.

25. 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 composite free layer having a width substantially larger than the first width and with a FM1/moment diluting layer/FM2 configuration wherein the first ferromagnetic (FM1) layer has a first interface with the tunnel barrier layer and the second ferromagnetic (FM2) layer has a second interface with a bottom surface of a perpendicular Hk enhancing layer, the first and second interfaces produce interfacial perpendicular anisotropy in the adjoining FM1 and FM2 layers, respectively, and wherein domain walls extend vertically through the composite free layer 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.

26. The domain wall motion device of claim 25 wherein the moment diluting layer is made of one or more of Ta, Al, Si, B, V, Ti, Mg, Hf, Cr, Cu, Ag, Au, and Os.

27. The domain wall motion device of claim 25 wherein the perpendicular Hk enhancing layer is a single layer or a laminate comprised of one or more oxides selected from MgO, SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, and HfOx.

28. The domain wall motion device of claim 25 wherein the composite free layer is part of a wire in an array of wires that is used to store digital information.

29. A method of forming a magnetic element exhibiting interfacial perpendicular anisotropy at interfaces between a composite free layer and certain adjoining layers, 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 FM1/moment diluting layer/FM2 configuration wherein the first ferromagnetic (FM1) layer has a first interface with the tunnel barrier layer and the second ferromagnetic (FM2) layer has a second interface with a bottom surface of a subsequently deposited perpendicular Hk enhancing layer, the first and second interfaces produce interfacial perpendicular anisotropy in the adjoining FM1 and FM2 layers, respectively;

(d) forming the perpendicular Hk enhancing layer on the FM2 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 perpendicular Hk enhancing layer is a single layer or a laminate comprised of one or more oxides selected from MgO, SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, and HfOx.

31. The method of claim 30 wherein the capping layer has a free energy of oxide formation substantially greater than that of the oxide in the perpendicular Hk enhancing layer.

32. The method of claim 29 wherein the FM1 and FM2 layers each have a thickness from about 5 to 20 Angstroms and are made of an Fe rich alloy with one or more of Co, Ni, and B, or are a Co rich alloy with one or more of Fe, Ni, and B.

33. The method of claim 29 wherein the moment diluting layer is non-magnetic and is one or more of Ta, Al, Si, B, V, Ti, Mg, Hf, Cr, Cu, Ag, and Au.

34. The method of claim 29 wherein the moment diluting layer is an alloy of two or more of Co, Ni, and Fe that is doped with one or more of Ta, Al, Si, V, B, Ti, Mg, Hf, Cr, Cu, Ag, Au, or Os wherein the dopant metal content is between 5 and 50 atomic % in the alloy.

35. A method of forming a magnetic element exhibiting interfacial perpendicular anisotropy at interfaces between a composite free layer and certain adjoining layers, comprising:

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

(b) forming a perpendicular Hk enhancing layer on the seed layer;

(c) depositing a free layer having a FM2/moment diluting layer/FM1 configuration wherein the first ferromagnetic (FM1) layer has a first interface with a subsequently deposited tunnel barrier layer and the second ferromagnetic (FM2) layer has a second interface with a top surface of the perpendicular Hk enhancing layer, the first and second interfaces produce interfacial perpendicular anisotropy in the adjoining FM1 and FM2 layers, respectively;

(d) forming a tunnel barrier layer on the FM1 layer;

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

(f) forming a capping layer on the pinned layer; and

(g) performing an anneal process.

36. The method of claim 35 wherein the perpendicular Hk enhancing layer is a single layer or a laminate comprised of one or more oxides selected from MgO, SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, and HfOx.

37. The method of claim 36 wherein the seed layer has a free energy of oxide formation substantially greater than that of the oxide in the perpendicular Hk enhancing layer.

38. The method of claim 35 wherein the FM1 and FM2 layers each have a thickness from about 5 to 20 Angstroms and are made of an Fe rich alloy with one or more of Co, Ni, and B, or are a Co rich alloy with one or more of Fe, Ni, and B.

39. The method of claim 35 wherein the moment diluting layer is non-magnetic and is one or more of Ta, Al, Si, B, V, Ti, Mg, Hf, Cr, Cu, Ag, and Au.

40. The method of claim 35 wherein the moment diluting layer is an alloy of two or more of Co, Ni, and Fe that is doped with one or more of Ta, Al, Si, V, B, Ti, Mg, Hf, Cr, Cu, Ag, Au, or Os wherein the dopant metal content is between 5 and 50 atomic % in the alloy.