Method of manufacturing 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 comprises a first high perpendicular Magnetic Anisotropy (PMA) multilayer and a second high PMA layer separated by a thin Ruthenium layer. Each PMA layer is comprised of 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 method of manufacturing a synthetic antiferromagnetic structure having a magnetic direction perpendicular to its plane, comprising:
depositing a PMA seed multilayer, wherein the depositing of a PMA seed multilayer step comprises:
depositing a first seed layer, and
depositing a nickel (Ni) seed layer over the first seed layer;
depositing a first magnetic perpendicular magnetic anisotropy (PMA) multilayer over the PMA seed multilayer, wherein the depositing of a first magnetic PMA multilayer step comprises:
depositing a first cobalt (Co) layer over the PMA seed multilayer;
depositing a first nickel/cobalt (Ni/Co) multilayer over the first Co layer; and
depositing a second Co layer over the first Ni/Co multilayer, wherein the second Co layer is separated from the first Co layer by the first Ni/Co multilayer;
depositing a Ruthenium (Ru) antiferromagnetic interlayer exchange coupling layer over the first magnetic PMA multilayer;
depositing a second magnetic PMA multilayer over the thin Ru antiferromagnetic interlayer exchange coupling layer, wherein the depositing of second magnetic PMA multilayer step comprises:
depositing a third Co layer over the Ru antiferromagnetic interlayer exchange coupling layer;
depositing a second Ni/Co multilayer over the third Co layer; and
depositing a fourth Co layer over the second Ni/Co multilayer, wherein the fourth Co layer is separated from the third Co layer by the second Ni/Co multilayer;
annealing at a temperature of 350 degrees Celsius or higher for a time sufficient to increase perpendicular magnetic anisotropy of the first magnetic PMA multilayer and second magnetic PMA multilayer such that the first magnetic PMA multilayer has a magnetic direction perpendicular to its plane and the second magnetic PMA multilayer has a magnetic direct perpendicular to its plane.
2. The method of claim 1 , wherein the annealing step further comprises annealing for a period of at least two hours.
3. The method of claim 1 , wherein the depositing a first magnetic PMA multilayer step is performed by dc magnetron sputtering.
4. The method of claim 1 , wherein the depositing a second magnetic PMA multilayer step is performed by dc magnetron sputtering.
5. The method of claim 1 , wherein the depositing a Ni seed layer over the first seed layer step comprises depositing the Ni seed layer such that the Ni seed layer has a thickness of at least 0.93 nanometers.
6. The method of claim 1 , wherein the depositing a first seed layer step comprises depositing a layer of alpha phase tantalum nitride.
7. The method of claim 6 , wherein the depositing a layer of alpha phase tantalum nitride step comprises depositing a layer of alpha phase tantalum nitride having a thickness of at least 0.5 nanometers.
8. The method of claim 1 , wherein the depositing a thin Ru antiferromagnetic interlayer exchange coupling layer comprises depositing a layer of Ru having a thickness of 0.85 nanometers.
9. The method of claim 1 , further comprising:
depositing a non-magnetic tunneling barrier layer over the second magnetic PMA multilayer; and
depositing 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, wherein the second magnetic PMA multilayer, the non-magnetic tunneling barrier layer, and the free magnetic layer form a magnetic tunnel junction.