High annealing temperature perpendicular magnetic anisotropy structure for magnetic random access memory
A perpendicular synthetic antiferromagnetic (pSAF) structure and method of making such a structure is disclosed. The pSAF structure can be a first high perpendicular Magnetic Anisotropy (PMA) multilayer and a second high PMA layer separated by a thin Ruthenium layer. Each PMA layer can be a first cobalt layer and a second cobalt layer separated by a nickel/cobalt multilayer. After each of the first and second PMA layers and the Ruthenium exchange coupling layer are deposited, the resulting structure goes through a high temperature annealing step, which results in each of the first and second PMA layers having a perpendicular magnetic anisotropy.
1. A magnetic device, comprising
a PMA seed multilayer comprised of a first seed layer and a nickel (Ni) seed layer, the Ni seed layer being disposed over the first seed layer, the first seed layer comprising a layer of α-TaN;
a first magnetic perpendicular magnetic anisotropy (PMA) multilayer disposed over the PMA seed multilayer, the first magnetic PMA multilayer comprising a first cobalt (Co) layer and a second Co layer, where the first Co layer and the second Co layer are separated by a first nickel/cobalt (Ni/Co) multilayer, wherein the first magnetic PMA multilayer has been annealed at a temperature of 350 degrees Celsius or higher, and has a magnetic direction perpendicular to its plane;
a Ruthenium (Ru) antiferromagnetic interlayer exchange coupling layer disposed over the first magnetic PMA multilayer;
a second magnetic PMA multilayer disposed over the Ru antiferromagnetic interlayer exchange coupling layer, the second magnetic PMA multilayer comprising a third Co layer and a fourth Co layer, where the third Co layer and the fourth Co layer are separated by a second nickel/cobalt (Ni/Co) multilayer, wherein the second magnetic PMA multilayer has been annealed at the temperature of 350 degrees Celsius or higher, and has a magnetic direction perpendicular to its plane;
wherein the first magnetic PMA multilayer, the Ru interlayer exchange coupling layer and the second magnetic PMA multilayer form a perpendicular synthetic antiferromagnet.
2. The magnetic device of claim 1 where in the first seed layer has a thickness of five nanometers.
3. The magnetic device of claim 1 wherein the first Co layer has a thickness of 0.3 nanometers, the second Co layer has a thickness of 0.18 nanometers.
4. The magnetic device of claim 3 , wherein the first Ni/Co multilayer comprises a nickel layer having a thickness of 0.6 nanometers and a cobalt layer having a thickness of 0.2 nanometers.
5. The magnetic device of claim 4 , wherein the first Ni/Co multilayer is repeated five times.
6. The magnetic device of claim 1 , wherein the Ni seed layer of the PMA seed multilayer has a thickness ranging from 0.5 nanometers to 0.95 nanometers.
7. The magnetic device of claim 1 , wherein the Ni seed layer of the PMA seed multilayer has a thickness of 0.93 nanometers.
8. The magnetic device of claim 1 , wherein the Ruthenium (Ru) antiferromagnetic interlayer exchange coupling layer has a thickness of 0.85 nanometers.
9. The magnetic device of claim 1 , wherein the first Co layer has a thickness of 0.3 nanometers, the second Co layer has a thickness of 0.18 nanometers, the third Co layer has a thickness of 0.18 nanometers, the fourth Co layer has a thickness of 0.18 nanometers.
10. The magnetic device of claim 9 , wherein the first Ni/Co multilayer comprise a first Ni layer having a thickness of 0.6 nanometers and fifth Co layer having a thickness of 0.2 nanometers.
11. The magnetic device of claim 10 wherein the first Ni/Co multilayer comprises five Ni/Co multilayers.
12. The magnetic device of claim 9 , wherein the second Ni/Co multilayer comprise a sixth Co layer having a thickness of 0.2 nanometers and second Ni layer having a thickness of 0.6 nanometers.
13. The magnetic device of claim 12 wherein the second Ni/Co multilayer comprises five Ni/Co multilayers.
14. The magnetic device of claim 1 , further comprising:
a non-magnetic tunneling barrier layer over the second magnetic PMA multilayer;
a free magnetic layer over the non-magnetic tunneling barrier layer, the free magnetic layer having a magnetic direction that can precess between a first direction and a second direction, the non-magnetic tunneling barrier layer spatially separating the free magnetic layer from the second magnetic PMA multilayer; and
wherein the second magnetic PMA multilayer, the non-magnetic tunneling barrier layer, and the free magnetic layer form a magnetic tunnel junction.
15. The magnetic device of claim 1 , wherein the first seed layer further comprises a layer of Ta.