Bottom electrode for MRAM device
View Patent ↗A multi-layered bottom electrode for an MTJ device on a silicon nitride substrate is described. It comprises a bilayer of alpha tantalum on ruthenium which in turn lies on a nickel chrome layer over a second tantalum layer.
1. A bottom electrode for an MTJ device on a silicon nitride substrate having a top surface, comprising:
on said top surface, a bilayer that comprises a nickel chrome portion on a tantalum containing portion;
a layer of ruthenium on said bilayer;
a layer of alpha tantalum on said ruthenium layer wherein said alpha tantalum layer has a roughness value that is no greater than about 5 Angstroms;
said MTJ device being on said alpha tantalum layer; and
a protective layer that covers said MTJ device.
2. The bottom electrode described in claim 1 wherein said tantalum containing portion is tantalum or tantalum nitride.
3. The bottom electrode described in claim 2 wherein said nickel chrome portion has a thickness between about 20 and 30 Angstroms.
4. The bottom electrode described in claim 2 wherein said tantalum containing portion has a thickness between about 20 and 50 Angstroms.
5. The bottom electrode described in claim 2 wherein said protective layer is selected from the group consisting of SiO 2 , SiN, and SiON and has a thickness between about 500 and 1,500 Angstroms.
6. The bottom electrode described in claim 2 wherein said ruthenium layer has a thickness between about 30 and 100 Angstroms.
7. The bottom electrode described in claim 2 wherein said alpha tantalum layer has a thickness between about 100 and 150 Angstroms.