Magnetic random access memory with multilayered seed structure
View Patent ↗The present invention is directed to a magnetic random access memory element that includes a multilayered seed structure formed by interleaving a first type sublayer and a second type sublayer to form one or more repeats of a unit bilayer structure and a first magnetic layer formed on top of the multilayered seed structure. The unit bilayer structure is made of the first and second type sublayers with at least one of the first and second type sublayers including therein one or more ferromagnetic elements. The multilayered seed structure may be amorphous or non-magnetic or both. The unit bilayer structure may be made of CoFeB and Ta sublayers.
1. A magnetic random access memory element comprising:
a non-magnetic seed structure formed by interleaving layers of nickel with layers of chromium; and
a first magnetic layer formed on top of said non-magnetic seed structure, said first magnetic layer having a first fixed magnetization direction substantially perpendicular to a layer plane thereof.
2. The magnetic random access memory element according to claim 1 , wherein said first magnetic layer has a multilayer structure formed by interleaving a third type material with a fourth type material, at least one of said third and fourth type materials being magnetic.
3. The magnetic random access memory element according to claim 2 , wherein said third type material is Co and said fourth type material is Ni, Pd, or Pt.
4. The magnetic random access memory element according to claim 2 , wherein one of said third and fourth type materials is nickel.
5. The magnetic random access memory element according to claim 2 further comprising:
an anti-ferromagnetic coupling layer formed on top of said first magnetic layer; and
a second magnetic layer formed on top of said anti-ferromagnetic coupling layer,
wherein said second magnetic layer has a second fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first fixed magnetization direction.
6. The magnetic random access memory element according to claim 5 , wherein said second magnetic layer includes at least two magnetic sublayers, one of said at least two magnetic sublayers having a multilayered structure formed by interleaving a fifth type material with a sixth type material, at least one of said fifth and sixth type materials being magnetic.
7. The magnetic random access memory element according to claim 6 , wherein one of said third and fourth type materials and one of said fifth and sixth type materials are the same.
8. The magnetic random access memory element according to claim 1 further comprising:
an anti-ferromagnetic coupling layer formed on top of said first magnetic layer; and
a second magnetic layer formed on top of said anti-ferromagnetic coupling layer,
wherein said second magnetic layer has a second fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first fixed magnetization direction.
9. The magnetic random access memory element according to claim 8 , wherein said second magnetic layer includes at least two magnetic sublayers, one of said at least two magnetic sublayers being made of CoFeB, another one of said at least two magnetic sublayers having a multilayered structure formed by interleaving a fifth type material with a sixth type material, at least one of said fifth and sixth type materials being magnetic.
10. The magnetic random access memory element according to claim 9 , wherein said fifth type material is Co and said sixth type material is Ni, Pt, or Pd.
11. The magnetic random access memory element according to claim 9 , wherein said multilayered structure formed by interleaving said fifth type material with said sixth type material is formed adjacent to said anti-ferromagnetic coupling layer.
12. The magnetic random access memory element according to claim 8 further comprising:
an insulating tunnel junction layer formed on top of said second magnetic layer; and
a third magnetic layer formed on top of said insulating tunnel junction layer,
wherein said third magnetic layer has a variable magnetization direction substantially perpendicular to a layer plane thereof.
13. The magnetic random access memory element according to claim 12 , wherein said third magnetic layer includes at least a magnetic sublayer made of CoFeTa or CoFeHf.
14. The magnetic random access memory element according to claim 12 , wherein said third magnetic layer is made of CoFeB.
15. A magnetic random access memory element comprising:
a multilayered seed structure formed by interleaving layers of nickel with layers of chromium; and
a first magnetic layer formed on top of said multilayered seed structure, said first magnetic layer having a first fixed magnetization direction substantially perpendicular to a layer plane thereof,
wherein said multilayered seed structure is amorphous.
16. A magnetic random access memory element comprising:
a multilayered seed structure formed by interleaving a first type material with a second type material, at least one of said first and second type materials including therein one or more ferromagnetic elements; and
a first magnetic layer formed on top of said multilayered seed structure, said first magnetic layer having a first fixed magnetization direction substantially perpendicular to layer plane thereof,
wherein said first type material is Cr and said second type material is NiFe.