Bottom electrode for MRAM applications
A substantially flat bottom electrode for magnetoresistive random access memory (MRAM) devices includes three components: a recessed bulk conductive material such as copper, a conductive liner lining the recess, and a cap layer, wherein the conductive liner is a harder material than the cap layer. The cap layer and the dielectric layer are coplanar having a height differential of less than 3 nanometers. The conductive liner has a lower chemical mechanical planarization removal rate. Also provided are processes for forming the bottom electrode.
1. A magnetoresistive random access memory (MRAM) device, comprising:
a bottom electrode embedded within a dielectric layer, the bottom electrode comprising a recessed metal conductor, a conductive liner lining a recess defined by the recessed metal conductor, and a cap material filling the recess to provide a top surface coplanar to a top surface of the dielectric layer having a height differential between the top surfaces of the cap layer and the dielectric layer of less than about 3 nanometers, wherein the conductive liner has a hardness greater than the cap layer;
a magnetic tunnel junction (MTJ) stack on the bottom electrode; and
a top electrode on the MTJ stack.
2. The MRAM device of claim 1 , wherein the cap material comprises tantalum nitride.
3. The MRAM device of claim 1 , wherein the conductive liner is a material selected from the group consisting of rhodium, palladium, platinum, osmium, ruthenium (Ru), combinations thereof, and combinations comprising at least one of the foregoing.
4. The MRAM device of claim 1 , wherein the conductive liner has a hardness greater than 12 GPa.
5. The MRAM device of claim 1 , wherein the MTJ stack comprises an anti-ferromagnetic layer, a pinning layer, and a free layer.
6. The MRAM device of claim 1 , wherein the MTJ stack comprises an anti-ferromagnetic layer, a tunnel barrier layer, and a free layer.
7. The MRAM device of claim 5 , wherein the top electrode is disposed on the free layer.
8. Then MRAM device of claim 1 , wherein the conductive liner comprises ruthenium, rhodium, or combinations comprising at least one of the foregoing.
9. The MRAM device of claim 1 , wherein the conductive liner has a lower chemical mechanical planarization removal rate than the cap material.
10. A magnetoresistive random access memory (MRAM) device, comprising:
a bottom electrode embedded within a dielectric layer, the bottom electrode comprising a recessed metal conductor, a ruthenium conductive liner lining a recess defined by the recessed metal conductor, and a tantalum nitride cap material filling the recess to provide a top surface coplanar to a top surface of the dielectric layer having a height differential between the top surfaces of the tantalum nitride and the dielectric layer of less than about 3 nanometers;
a magnetic tunnel junction (MTJ) stack is disposed on the bottom electrode; and
a top electrode is disposed on the MTJ stack.
11. The MRAM device of claim 10 , wherein the bottom electrode has columnar grain growth.
12. The MRAM device of claim 10 , wherein the ruthenium conductive liner is at a thickness from 1 to 10 nanometers.
13. The MRAM device of claim 10 , wherein the ruthenium conductive liner is a non-conformal coating.
14. The MRAM device of claim 10 , wherein the ruthenium conductive liner is a conformal coating.
15. A process of forming a bottom electrode in a magnetoresistive random access memory (MRAM) device, the process comprising:
forming a recessed metal conductor in a dielectric layer;
conformally depositing a conductive liner material in a recess of the recessed metal conductor and the dielectric layer;
depositing a tantalum nitride cap layer in the recess on the conductive liner material and on the dielectric layer; and
polishing the tantalum nitride cap layer to the dielectric layer with a chemical mechanical planarization process, wherein a height differential between the tantalum nitride surface remaining in the recess and the dielectric layer surface is less than 3 nanometers, wherein the conductive liner material is harder than the tantalum nitride.
16. The process of claim 15 , wherein the conductive liner material comprises ruthenium.
17. The process of claim 15 , wherein the conductive liner material comprises ruthenium, rhodium, or combinations comprising at least one of the foregoing.
18. The process of claim 15 , wherein the conductive liner material has a lower chemical mechanical planarization removal rate than the tantalum nitride.
19. The process of claim 15 , wherein the metal conductor comprise copper, aluminum, tantalum, tungsten, tantalum nitride (TaN), titanium, titanium nitride (TiN), and/or a combination thereof.
20. The process of claim 15 , wherein the conductive liner material is at a thickness of 1 to 10 nanometers.