Depositing conformal boron nitride film by CVD without plasma
A method of forming a boron nitride or boron carbon nitride dielectric produces a conformal layer without loading effect. The dielectric layer is formed by chemical vapor deposition (CVD) of a boron-containing film on a substrate, at least a portion of the deposition being conducted without plasma, and then exposing the deposited boron-containing film to a plasma. The CVD component dominates the deposition process, producing a conformal film without loading effect. The dielectric is ashable, and can be removed with a hydrogen plasma without impacting surrounding materials. The dielectric has a much lower wet etch rate compared to other front end spacer or hard mask materials such as silicon oxide or silicon nitride, and has a relatively low dielectric constant, much lower than silicon nitride.
1. A method of forming a dielectric layer, comprising:
receiving in a plasma processing chamber a substrate;
forming a boron nitride or boron carbon nitride film by a process comprising,
chemical vapor deposition of a boron-containing film on the substrate, at least a portion of the deposition being conducted without plasma; and
exposing the deposited boron-containing film to a plasma.
2. The method of claim 1 , wherein the depositing and treating operations are repeated at least once.
3. The method of claim 1 , wherein the depositing and treating operations are repeated a plurality of times.
4. The method of claim 1 , wherein the deposited film is sufficiently thin to allow complete penetration of the plasma for densification of the film.
5. The method of claim 1 , wherein the deposited film is no more than 10 Å thick.
6. The method of claim 1 , wherein the deposited film is about 5 Å thick.
7. The method of claim 1 , wherein the dielectric layer is at least 80% conformal.
8. The method of claim 1 , wherein the dielectric layer is a boron nitride layer.
9. The method of claim 1 , wherein the dielectric layer is a boron carbon nitride layer.
10. The method of claim 1 , wherein the plasma exposure is conducted in the presence of a nitrogen-containing species.
11. The method of claim 1 , further comprising, prior to forming the film, forming a nucleation layer on the substrate.
12. The method of claim 11 , wherein the nucleation layer comprises silicon nitride.
13. The method of claim 1 , further comprising, prior to depositing the film, pre-treating the substrate to enhance adhesion of the film.
14. The method of claim 13 , wherein the pre-treatment comprises exposing the substrate to an ammonia plasma.
15. The method of claim 1 , wherein the film formation comprises chemical vapor deposition using a boron hydride or organo-borane precursor without a plasma, followed by exposure of the deposited film to a nitrogen-containing plasma.
16. The method of claim 15 , wherein the nitrogen-containing plasma is an ammonia plasma.
17. The method of claim 15 , wherein the plasma further comprises a noble gas.
18. The method of claim 15 , wherein the plasma further comprises a hydrocarbon.
19. The method of claim 18 , wherein the precursor is a boron hydride.
20. The method of claim 1 , wherein a boron hydride or organo-borane boron-containing film precursor and a nitrogen-containing species are present in the chamber together for at least a portion of the film deposition operation.
21. The method of claim 20 , wherein the chemical vapor deposition and plasma exposure are performed by pulsing a plasma on and off in the presence of a boron hydride or organo-borane precursor and a nitrogen-containing species.
22. The method of claim 20 , wherein boron reactant flow into the processing chamber is such that a boron-containing precursor is only present when the plasma is off.
23. The method of claim 20 , wherein the film precursor is diborane.
24. The method of claim 20 , wherein the film precursor is an organo-borane.
25. The method of claim 24 , further comprising exposing the precursor to the substrate at a temperature sufficient to decompose the precursor to metallic boron.
26. The method of claim 25 , wherein the temperature is about 200 to 400° C.
27. The method of claim 1 , the film formation comprises chemical vapor deposition using a boron, hydrogen and nitrogen-containing species precursor without a plasma, followed by exposure of the deposited film to a plasma.
28. The method of claim 1 , further comprising removing the dielectric layer from the substrate by ashing.
29. The method of claim 28 , wherein the ashing is conducted with a hydrogen plasma.
30. The method of claim 3 , wherein the dielectric layer has a thickness of about 50 to 500 Å.