Methods for etching carbon nano-tube films for use in non-volatile memories
Memory cells, and methods of forming such memory cells are provided that include a steering element coupled to a carbon-based reversible resistivity-switching material. In particular embodiments, methods in accordance with this invention etch a carbon nano-tube (“CNT”) film formed over a substrate, the methods including coating the substrate with a masking layer, patterning the masking layer, and etching the CNT film through the patterned masking layer using a non-oxygen based chemistry. Other aspects are also described.
1. A method comprising:
forming a carbon nano-tube (“CNT”) film over a substrate;
forming a protective liner over the CNT film;
forming an electrode over the protective liner;
coating the substrate with a masking layer;
patterning the masking layer;
etching the electrode, the protective liner and the CNT film through the patterned masking layer in a single etch step using a non-oxygen based chemistry and a substrate bias power of between about 50 and about 150 Watts;
forming a dielectric sidewall liner on sidewalls of the etched CNT film; and
forming a steering element coupled to the etched CNT film.
2. The method of claim 1 , wherein etching the CNT film includes:
loading the substrate into an plasma etch chamber; and
etching the substrate using boron trichloride (“BCl 3 ”) and dichlorine (“Cl 2 ”).
3. The method of claim 2 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 of about 70:1 to about 3:5.
4. The method of claim 2 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 of about 4:1 to about 1.8:1.
5. The method of claim 2 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 of about 5:2.
6. The method of claim 2 , wherein etching the substrate further comprises using argon (“Ar”).
7. The method of claim 6 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 to Ar of about 70:1:1 to about 3:5:5.
8. The method of claim 6 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 to Ar of about 4:1:1 to about 1.8:1:1.
9. The method of claim 6 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 to Ar of about 5:2:2.
10. The method of claim 2 , wherein the masking layer includes photoresist.
11. The method of claim 10 further comprising asking the photoresist.
12. The method of claim 11 , wherein the photoresist is ashed before etching the substrate.
13. The method of claim 11 , wherein the photoresist is ashed after etching the substrate.
14. The method of claim 11 , wherein ashing comprises a two-step ashing procedure.
15. A memory cell formed using the method of claim 1 .
16. A method of forming a memory cell, the method comprising:
forming a layer of a carbon nanotube (“CNT”) material above a substrate;
forming a protective liner over the CNT material;
forming an electrode over the protective liner;
etching the electrode, the protective liner and the CNT material in a single etch step in a plasma etch chamber using boron trichloride (BCl 3 ) and dichlorine (Cl 2 ), and a substrate bias power of between about 50 and about 150 Watts;
forming a dielectric sidewall liner on sidewalls of the etched CNT material; and
forming a steering element coupled to the etched CNT material.
17. The method of claim 16 , wherein the substrate bias power is between about 85 and about 110 Watts.
18. The method of claim 16 , wherein the substrate bias power is about 100 Watts.
19. The method of claim 16 , wherein etching the CNT material comprises using a ratio of BCl 3 to Cl 2 of about 70:1 to about 3:5.
20. The method of claim 16 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 of about 4:1 to about 1.8:1.
21. The method of claim 16 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 of about 5:2.
22. The method of claim 17 , wherein etching the substrate further comprises using argon (“Ar”).
23. The method of claim 22 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 to Ar of about 70:1:1 to about 3:5:5.
24. The method of claim 22 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 to Ar of about 4:1:1 to about 1.8:1:1.
25. The method of claim 22 , wherein etching the substrate comprises using a ratio of BCl 3 to Cl 2 to Ar of about 5:2:2.
26. The method of claim 16 , wherein the steering element comprises a diode.
27. The method of claim 26 , wherein forming the steering element comprises:
forming one or more layers of silicon above the substrate; and
etching the one or more layers of silicon.
28. The method of claim 27 , comprising etching the one or more layers of silicon and the CNT layer in a single etching step.
29. The method of claim 27 , comprising etching the one or more layers of silicon and the CNT layer separately.
30. A memory cell formed using the method of claim 17 .
31. A method of forming a memory cell, the method comprising:
forming a layer of a carbon nanotube (“CNT”) material above a substrate;
forming a protective liner over the CNT material;
forming an electrode over the protective liner;
using a non-oxygen based chemistry to etch the electrode, the protective liner and the CNT material in a single etch step at a substrate bias power of between about 50 and about 150 Watts to have nearly vertical sidewalls and little or no undercut of the CNT material;
forming a dielectric sidewall liner on sidewalls of the etched CNT material; and
forming a steering element coupled to the etched CNT material.
32. The method of claim 31 , wherein the steering element comprises a diode.
33. The method of claim 32 , wherein forming the steering element comprises:
forming one or more layers of silicon above the substrate; and
etching the one or more layers of silicon.
34. The method of claim 33 , comprising etching the one or more layers of silicon and the CNT layer in a single etching step.
35. The method of claim 33 , comprising etching the one or more layers of silicon and the CNT layer separately.
36. A memory cell formed using the method of claim 31 .