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 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 made of said first and second type sublayers with at least one of said first and second type sublayers including therein one or more ferromagnetic elements; and
a first magnetic layer formed on top of said multilayered seed structure.
2. The magnetic random access memory element according to claim 1 , wherein said multilayered seed structure is non-magnetic.
3. The magnetic random access memory element according to claim 1 , wherein said multilayered seed structure is amorphous.
4. The magnetic random access memory element according to claim 1 , wherein one of said first and second type sublayers is made of Ta.
5. The magnetic random access memory element according to claim 1 , wherein one of said first and second type sublayers is made of CoFeB.
6. The magnetic random access memory element according to claim 1 , wherein one of said first and second type sublayers is made of FeZrB.
7. The magnetic random access memory element according to claim 1 , wherein said multilayered seed structure is made of [CoFeB/Ta] n with a Ta layer formed adjacent to said first magnetic layer.
8. The magnetic random access memory element according to claim 1 , wherein said multilayered seed structure has two or three repeats of said unit bilayer structure.
9. The magnetic random access memory element according to claim 1 , wherein said first magnetic layer has a first fixed magnetization direction substantially perpendicular to layer plane thereof.
10. The magnetic random access memory element according to claim 1 , wherein said first magnetic layer has a variable magnetization direction substantially perpendicular to layer plane thereof.
11. The magnetic random access memory element according to claim 1 , wherein said first magnetic layer has a multilayer structure formed by interleaving two different types of materials with at least one of said two different types of materials being magnetic.
12. The magnetic random access memory element according to claim 11 , wherein one of said two different types of materials is cobalt and the other one of said two different types of materials is platinum, palladium, or nickel.
13. The magnetic random access memory element according to claim 1 further comprising:
an insulating tunnel junction layer formed on top of said first magnetic layer; and
a second magnetic layer formed on top of said insulating tunnel junction layer.
14. The magnetic random access memory element according to claim 13 , wherein said first magnetic layer has a first fixed magnetization direction substantially perpendicular to layer plane thereof, said second magnetic layer has a variable magnetization direction substantially perpendicular to layer plane thereof.
15. The magnetic random access memory element according to claim 13 , wherein said first magnetic layer has a variable magnetization direction substantially perpendicular to layer plane thereof, said second magnetic layer has a first fixed magnetization direction substantially perpendicular to layer plane thereof.
16. The magnetic random access memory element according to claim 15 further comprising:
an anti-ferromagnetic coupling layer formed on top of said second magnetic layer; and
a third magnetic layer formed on top of said anti-ferromagnetic coupling layer,
wherein said third magnetic layer has a second fixed magnetization direction that is substantially perpendicular to layer plane thereof and is substantially opposite to said first fixed magnetization direction.
17. 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 first magnetic layer has a first fixed magnetization direction substantially perpendicular to layer plane thereof, said second magnetic layer has a second fixed magnetization direction that is substantially perpendicular to layer plane thereof and is substantially opposite to said first fixed magnetization direction.
18. The magnetic random access memory element according to claim 17 , wherein said second magnetic layer includes two magnetic sublayers in touching contact with each magnetic sublayer comprising cobalt and iron.
19. The magnetic random access memory element according to claim 17 further comprising:
an insulating tunnel junction layer formed on top on 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 layer plane thereof.