Method of etching MTJ using CO process chemistries

1. A method for fabricating a magnetic film structure, the method comprising:

forming a magnetic structure on a bottom electrode layer, wherein the magnetic structure includes:

at least one pinned bottom magnetic film layer having a fixed magnetic orientation;

at least one top magnetic film layer having a magnetic orientation that can be manipulated by a current; and

a tunneling layer between the at least one pinned bottom magnetic film layer and the at least one top magnetic film layer;

forming a metallic hard mask above the magnetic structure;

etching, by inductively-coupled plasma etching, the metallic hard mask, but not the magnetic structure, using a first chemistry;

starting etching of the magnetic structure using a second chemistry to form at least one magnetic bit, wherein the second chemistry is different from the first chemistry;

monitoring a signal of a spectral signature of a plasma at a predetermined wavelength while etching the magnetic structure;

stopping etching of the magnetic structure when a drop in the signal is observed; and

removing redeposited material from at least one sidewall of the at least one magnetic bit by over-etching the at least one pinned bottom magnetic film layer, the at least one top magnetic film layer, and the tunneling layer, wherein the over-etching uses inductively-coupled plasma etching.

2. The method of claim 1 , wherein the metallic hard mask comprises at least one of titanium, tantalum, titanium nitride, silicon dioxide, aluminum, or amorphous carbon.

3. The method of claim 2 , wherein the metallic hard mask comprises titanium nitride.

4. The method of claim 2 , wherein the metallic hard mask comprises titanium.

5. The method of claim 1 , wherein the second chemistry comprises carbon monoxide.

6. The method of claim 5 , wherein the second chemistry comprises a mixture of carbon monoxide and ammonia.

7. The method of claim 1 , wherein the second chemistry comprises methanol.

8. The method of claim 1 , wherein the first chemistry comprises a fluorine-based chemistry.

9. The method of claim 8 , wherein the second chemistry comprises carbon monoxide.

10. The method of claim 9 , wherein the second chemistry comprises a mixture of carbon monoxide and ammonia.

11. The method of claim 8 , wherein the second chemistry comprises methanol.

12. The method of claim 1 , further comprising forming a capping layer above the magnetic structure, wherein the metallic hard mask is formed above the capping layer.

13. The method of claim 12 , wherein the capping layer comprises ruthenium.

14. The method of claim 1 , further comprising forming a bottom antireflective coating above the metallic hard mask.

15. The method of claim 1 , further comprising forming and etching an oxide spacer above the magnetic bit.

16. The method of claim 1 , wherein said starting etching of the magnetic structure is performed at a higher power than said removing redeposited material.

17. The method of claim 1 , wherein said starting etching of the magnetic structure is performed at a higher frequency than said removing redeposited material.

18. The method of claim 1 , wherein said starting etching of the magnetic structure is performed at a lower pressure than said removing redeposited material.

19. The method of claim 1 , wherein:

said starting etching of the magnetic structure is performed at a higher power than said removing redeposited material;

said starting etching of the magnetic structure is performed at a higher frequency than said removing redeposited material; and

said starting etching of the magnetic structure is performed at a lower pressure than said removing redeposited material.

20. The method of claim 1 , wherein said removing redeposited material is performed using the second chemistry.