Vapor-etch cyclic process

1. A method of selectively etching oxides over nitrides in a vapor-etch cyclic process, the method comprising:

in a first portion of the vapor-etch cyclic process:

exposing a substrate having oxide features and nitride features formed thereon to selected etchants in a vapor-phase chamber under conditions to etch the oxide features with selectively relative to the nitride features;

transferring the substrate to a post-etch heat treatment chamber; and

heating the substrate to remove etchant reaction products from the substrate; and

in a second portion of the vapor-etch cyclic process:

transferring the substrate from the post-etch heat treatment chamber to the vapor-phase chamber;

exposing the substrate to the selected etchants in the vapor-phase chamber under conditions to etch the oxide features with selectively relative to the nitride features;

transferring the substrate to the post-etch heat treatment chamber; and

heating the substrate to remove additional etchant reaction products from the substrate.

2. The method of claim 1 , wherein a first of the selected etchants is ammonia (NH 3 ).

3. The method of claim 1 , wherein a second of the selected etchants is hydrogen fluoride (HF).

4. The method of claim 1 , further comprising mixing the selected etchants in a gas mixing chamber prior to the selected etchants entering the vapor-phase chamber.

5. The method of claim 1 , wherein a volumetric gas flow rate of the selected etchants entering the vapor-phase chamber is from about 30 sccm to about 100 sccm.

6. The method of claim 1 , wherein a pressure in the vapor-phase chamber Is maintained within a range from about 20 mT to about 200 mT.

7. The method of claim 1 , wherein a pressure in the vapor-phase chamber Is maintained at about 40 mT.

8. The method of claim 1 , wherein a stage in the vapor-phase chamber on which the substrate is placed is maintained within a temperature range from about 20° C. to about 80° C.

9. The method of claim 1 , wherein a stage in the vapor-phase chamber on which the substrate is placed is maintained within a temperature range from about 25° C. to about 45° C.

10. The method of claim 1 , wherein an average time of the substrate in the vapor-phase chamber during the first portion of the process varies within a range from about 4 seconds to about 20 seconds.

11. The method of claim 1 , wherein a pressure in the post-etch heat treatment chamber is maintained in a range from about 100 mT to about 3000 mT.

12. The method of claim 1 , wherein a stage in the post-etch heat treatment chamber on which the substrate is placed is maintained within a temperature range from about 100° C. to about 300° C.

13. The method of claim 1 , wherein an average time of the substrate in the post-etch heat treatment chamber during the second portion of the process varies within a range from about 30 seconds to about 150 seconds.

14. The method of claim 1 , wherein etching of the substrate occurs in a non-plasma-based reaction.

15. A method of selectively etching oxides over nitrides in a vapor-etch cyclic process, the method comprising:

determining a number of cycles in the vapor-etch cyclic process, the number of cycles being at least two iterations of a substrate including oxide features and nitride features being exposed to etchants in a vapor-phase chamber followed by being heated in a post-etch heat treatment process, the substrate having oxide features and nitride features formed thereon;

exposing the substrate to ammonia (NH 3 ) and hydrogen fluoride (HF) etchants in the vapor-phase chamber in a first portion of the vapor-etch cyclic process under conditions to etch the oxide features with a threshold degree of selectively relative to the nitride features;

heating the substrate to remove etchant reaction products from the substrate in a second portion of the vapor-etch cyclic process; and

repeating the first portion and the second portion of the vapor-etch cyclic process for a remainder of the determined number of cycles.

16. The method of claim 15 , further comprising evacuating substantially all etchant gases from the vapor-phase chamber prior to beginning the post-etch heat treatment process.

17. The method of claim 15 , further comprising evacuating substantially all etchant reaction products from the vapor-phase chamber prior to beginning additional operations of exposing the substrate to the ammonia (NH 3 ) and the hydrogen fluoride (HF) etchants.

18. The method of claim 15 , wherein the first portion and the second portion of the vapor-etch cyclic process are performed in a single vapor-phase chamber.

19. The method of claim 15 , wherein the oxide features and the nitride features formed on the substrate define a portion of a DRAM memory cell.

20. A method of selectively etching oxides over nitrides in a vapor-etch cyclic process, the method comprising:

exposing a substrate having oxide features and nitride features formed thereon to selected etchants in a first portion of the vapor-etch cyclic process; and

heating the substrate to remove etchant reaction products from the substrate in a second portion of the vapor-etch cyclic process;

wherein oxide features are etched relative to the nitride features at a selectively of at least 50:1.

21. The method of claim 20 , further comprising:

determining whether a target oxide etch level has been reached; and

repeating the first portion and the second portion of the vapor-etch cyclic process for at least one additional cycle until the target oxide etch level is reached.

22. The method of claim 21 , further comprising predetermining an oxide-to-nitride selectivity ratio of the vapor-etch cyclic process prior to performing the method to approximate a number of iterations expected for repeating the first portion and the second portion of the vapor-etch cyclic process.

23. The method of claim 21 , further comprising:

determining an amount of oxide etch per each cycle of the vapor-etch cyclic process; and

determining an expected number of iterations expected for repeating the first portion and the second portion of the vapor-etch cyclic process.

24. A method of selectively etching oxides over nitrides in a vapor-etch cyclic process, the method comprising:

exposing a substrate to ammonia (NH 3 ) and hydrogen fluoride (HF) etchants in a vapor-phase chamber in a first portion of the vapor-etch cyclic process for a period of between 4 and 20 seconds, the substrate having exposed oxide features and nitride features formed thereon;

heating the substrate to remove etchant reaction products from the substrate in a second portion of the vapor-etch cyclic process; and

repeating the first portion and the second portion of the vapor-etch cyclic process at least once;

wherein the oxide features are etched with selectively of at least 50:1 relative to the nitride features.

25. The method of claim 24 , further comprising determining whether a target oxide etch level has been reached.

26. The method of claim 25 , further comprising:

based on a determination that the target oxide etch level has been reached, ending the vapor-etch cyclic process; and

based on a determination that the target oxide level has not been reached:

exposing the substrate in a further iteration to the ammonia (NH 3 ) and hydrogen fluoride (HF) etchants in the vapor-phase chamber; and

heating the substrate to remove additional etchant reaction products from the substrate.