Double pinned magnetoresistance element with temporary ferromagnetic layer to improve annealing
View Patent ↗A double pinned magnetoresistance element has a temporary ferromagnetic layer, two PtMn antiferromagnetic pinning layers, and two associated synthetic antiferromagnetic (SAF) pinned layer structures, the temporary ferromagnetic layer operable to improve annealing of the two PtMn antiferromagnetic pinning layers and the two associated SAFs to two different magnetic directions that are a relative ninety degrees apart.
1. A magnetoresistance element deposited upon a substrate, comprising:
a plurality of layers deposited in a stack of layers upon the substrate, the stack of layers comprising first and second antiferromagnetic pinning layers and a free layer structure disposed between the first and second antiferromagnetic pinning layers; and
a temporary ferromagnetic layer deposited over a top of the stack of layers, the top being distal from the substrate.
2. The magnetoresistance element of claim 1 , wherein the stack of layers further comprises:
a first pinned layer structure; and
a second pinned layer structure, wherein the first antiferromagnetic pinning layer is deposited proximate to the first pinned layer structure, and wherein the second antiferromagnetic pinning layer is deposited proximate to the second pinned layer structure, such that the first and second pinned layer structures are deposited between the first and second antiferromagnetic pinning layers, wherein magnetic field directions in the first and second antiferromagnetic pinning layers are annealed to have different directions.
3. The magnetoresistance element of claim 2 , wherein the temporary ferromagnetic layer is comprised of CoFe.
4. The magnetoresistance element of claim 3 , wherein the temporary ferromagnetic layer has a thickness of about two nanometers before it is removed.
5. The magnetoresistance element of claim 2 , wherein the stack of layers further comprises:
a first nonmagnetic layer deposited between the first pinned layer structure and the free layer structure; and
a second nonmagnetic layer deposited between the second pinned layer structure and the free layer structure, wherein a material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer to be greater than 0.5 nm while allowing a desired partial pinning between the second pinned layer structure and the free layer structure, wherein the material of the second nonmagnetic layer is selected to allow a thickness of the first nonmagnetic layer of greater than 0.5 nm to allow a magnetic coupling between the second pinned layer structure and the free layer structure to be between a maximum ferromagnetic coupling and a maximum antiferromagnetic coupling.
6. The magnetoresistance element of claim 5 , wherein the second nonmagnetic layer is comprised of a material selected to provide an adjustable RKKY coupling between the second pinned layer structure and the free layer structure.
7. The magnetoresistance element of claim 5 , wherein the second nonmagnetic layer is comprised of Ru.
8. The magnetoresistance element of claim 7 , wherein a thickness of the second nonmagnetic layer is between about 0.5 nm and about 4.0 nm.
9. The magnetoresistance element of claim 7 , wherein a thickness of the second nonmagnetic layer is between about 2.0 nm and about 4.0 nm.
10. The magnetoresistance element of claim 7 , wherein a material and a thickness of the first nonmagnetic layer is selected to allow substantially zero magnetic coupling between the first pinned layer structure and the free layer structure.
11. The magnetoresistance element of claim 7 , wherein the first nonmagnetic layer is comprised of Cu, Au or Ag.
12. The magnetoresistance element of claim 7 , wherein a thickness of the first nonmagnetic layer is between about 2.0 nm and about 3.0 nm.
13. The magnetoresistance element of claim 5 , wherein the magnetoresistance element comprises a spin valve.
14. The magnetoresistance element of claim 5 , wherein the magnetoresistance element comprises a GMR sensing element.
15. The magnetoresistance element of claim 5 , wherein the magnetoresistance element comprises a TMR sensing element.
16. The magnetoresistance element of claim 5 , wherein the free layer structure comprises first and second ferromagnetic free layers coupled together with no spacer layer between the first and second ferromagnetic free layers.
17. The magnetoresistance element of claim 16 , wherein the first ferromagnetic free layer is comprised of CoFe and the second ferromagnetic free layer is comprised of NiFe.
18. The magnetoresistance element of claim 5 , wherein the magnetoresistance element has a yoke shape.
19. The magnetoresistance element of claim 18 , wherein a length (L) of the yoke shape and a length (d) of lateral arms of the yoke shape are each at least three times a width (w) of the yoke shape, and the width (w) of the yoke shape is between about one μm and about twenty μm, wherein the length (L) is a longest dimension of the yoke shape.
20. method of fabricating a magnetoresistance element, comprising:
depositing a plurality of layers in a stack of layers upon a substrate, the stack of layers comprising first and second antiferromagnetic pinning layers and a free layer structure disposed between the first and second antiferromagnetic pinning layers; and
depositing a temporary ferromagnetic layer over a top of the stack of layers, the top being distal from the substrate.
21. The method of claim 20 , wherein the stack of layers further comprises:
a first pinned layer structure; and
a second pinned layer structure, wherein the first antiferromagnetic pinning layer is deposited proximate to the first pinned layer structure; and wherein the second antiferromagnetic pinning layer is deposited proximate to the second pinned layer structure, such that the first and second pinned layer structures are deposited between the first and second antiferromagnetic pinning layers, wherein magnetic field directions in the first and second antiferromagnetic pinning layers are annealed to have different directions, the method further comprising:
removing the temporary ferromagnetic layer.
22. The method of claim 21 , wherein the temporary ferromagnetic layer is comprised of CoFe.
23. The method of claim 21 , wherein the temporary ferromagnetic layer has a thickness of about two nanometers before it is removed.
24. The method of claim 21 , wherein the removing comprises ion beam etching to remove the temporary ferromagnetic layer.
25. The method of claim 24 , wherein the ion beam etching comprises ion beam etching for a time period of about thirty seconds.
26. The method of claim 21 , wherein the stack of layers further comprises:
a first nonmagnetic layer deposited between the first pinned layer structure and the free layer structure; and
a second nonmagnetic layer deposited between the second pinned layer structure and the free layer structure, wherein a material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer to be greater than 0.5 nm while allowing a desired partial pinning between the second pinned layer structure and the free layer structure, wherein the material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer of greater than 0.5 nm to allow a magnetic coupling between the second pinned layer structure and the free layer structure to be between a maximum ferromagnetic coupling and a maximum antiferromagnetic coupling.
27. The method of claim 26 , further comprising:
before the removing the temporary ferromagnetic layer:
annealing the first pinned layer structure and the first antiferromagnetic pinning layer at a first annealing temperature, with a first annealing magnetic field, with a first annealing magnetic field direction, and with a first annealing duration; and
annealing the second pinned layer structure and the second antiferromagnetic pinning layer at a second annealing temperature, with a second annealing magnetic field, with a second annealing magnetic field direction, and with a second annealing duration, wherein:
the first annealing magnetic field direction is in a selected magnetization direction,
the second annealing magnetic field direction is different than the first annealing magnetic field direction, and
the first annealing magnetic field is higher than the second annealing magnetic field, wherein the second annealing magnetic field is selected to result in annealing of the second pinned layer structure and annealing of the second antiferromagnetic pinning layer without affecting the annealing of the first pinned layer structure or the annealing of the first antiferromagnetic pinning layer.
28. The method of claim 27 , wherein the first and second pinned layer structures are both comprised of two or more CoFe layers.
29. The method of claim 27 , wherein the first and second antiferromagnetic pinning layers are each comprised of PtMn, and wherein the first annealing magnetic field is about one Tesla, and wherein the second annealing magnetic field is about 0.12 Tesla.
30. The method of claim 29 , wherein the first annealing temperature is about two hundred ninety five degrees Celsius, wherein the second annealing temperature is about three hundred degrees Celsius, and wherein the first annealing duration is about one hour and the second annealing duration is about one hour.
31. The method of claim 26 , wherein a thickness of the second nonmagnetic layer is between about 0.5 nm and about 4 nm.
32. The method of claim 26 , wherein the second nonmagnetic layer is comprised of a material selected to provide an adjustable RKKY coupling between the first pinned layer structure and the free layer structure.
33. The method of claim 26 , wherein the second nonmagnetic layer is comprised of Ru.
34. The method of claim 21 , further comprising:
patterning at least a portion of the magnetoresistance element in a yoke shape.
35. The method of claim 34 , wherein a length (L) of the yoke shape and a length (d) of lateral arms of the yoke shape are each at least three times a width (w) of the yoke shape, and the width (w) of the yoke shape is between about one μm and about twenty μm, wherein the length (L) is a longest dimension of the yoke shape.
36. The method of claim 21 , further comprising:
depositing a cap layer over a selected one of the first or second antiferromagnetic pinning layer after the removing;
patterning at least a portion of the magnetoresistance element in a yoke shape.
37. The method of claim 36 , wherein a length (L) of the yoke shape and a length (d) of lateral arms of the yoke shape are each at least three times a width (w) of the yoke shape, and the width (w) of the yoke shape is between about one μm in and about twenty μm, wherein the length (L) is a longest dimension of the yoke shape.