Apparatus and method for forming chalcogenide semiconductor absorber materials with sodium impurities
A method and system for forming chalcogenide semiconductor absorber materials with sodium impurities is provided. The system includes a sodium vaporizer in which a solid sodium source material is vaporized. The sodium vapor is added to reactant gases and/or annealing gases and directed to a furnace that includes a substrate with a metal precursor material. The precursor material reacts with reactant gases such as S-containing gases and Se-containing gases according to various process sequences. In one embodiment, a selenization operation is followed by an annealing operation and a sulfurization operation and the sodium vapor is caused to react with the metal precursor during at least one of the annealing and the sulfurization steps to produce a chalcogenide semiconductor absorber material that includes sodium dopant impurities.
1. A method for forming a chalcogenide semiconductor absorber material, said method comprising:
disposing a substrate with metallic precursors thereon, in a furnace;
vaporizing sodium to produce a sodium vapor;
selenizing by causing thermal reaction between selenium and said metallic precursors in a selenization reaction in said furnace;
sulfurizing by causing thermal reaction between sulfur and said metallic precursors in a sulfurization reaction in said furnace after said selenization reaction; and
annealing after said selenization reaction,
wherein at least one of said sulfurizing and said annealing includes causing said sodium vapor to react with said metallic precursors.
2. The method as in claim 1 , wherein said sulfurizing is carried out after said annealing and at a lower temperature than said annealing and said annealing is carried out at a higher temperature than said selenization reaction.
3. The method as in claim 1 , wherein said sulfurization includes causing said sodium vapor to react with said metallic precursors by delivering a sulfur-containing gas mixture and said sodium vapor, to said furnace.
4. The method as in claim 1 , wherein said annealing includes causing said sodium vapor to react with said metallic precursors by delivering said sodium vapor to said furnace during said annealing.
5. The method as in claim 1 , wherein said vaporizing comprises heating a solid sodium source material, said solid sodium source material comprising at least one of NaF, NaCl, NaNO 3 , Na 2 SeO 3 , Ns 2 S and Na 2 Se.
6. The method as in claim 1 , wherein said vaporizing includes directing a carrier gas to a vaporizer unit, said sodium vapor comprises a sodium vapor stream, at least one of said sulfurizing and said annealing includes delivering said sodium vapor stream to said furnace, wherein said carrier gas comprises one of H 2 S, H 2 Se, N 2 and Ar.
7. The method as in claim 6 , wherein said carrier gas includes H 2 S and said causing said sodium vapor to react causes the sulfurization reaction.
8. The method as in claim 1 , wherein said causing said sodium vapor to react includes heating, and wherein the selenizing is performed prior to said causing said sodium vapor to react.
9. The method as in claim 1 , wherein the selenizing is performed prior to said causing said sodium vapor to react.
10. The method as in claim 1 , wherein the annealing is performed with an inert annealing gas and said sodium vapor prior to said causing said sodium vapor to react, using an annealing temperature higher than a temperature used in said causing said sodium vapor to react.
11. The method as in claim 1 , wherein said annealing is performed using an inert annealing gas, prior to said causing said sodium vapor to react.
12. A method for forming a chalcogenide semiconductor absorber material, said method comprising:
disposing a substrate with metallic precursors thereon, in a furnace;
vaporizing sodium to produce a sodium vapor;
selenizing by causing thermal reaction between selenium and said metallic precursors in a selenization reaction in said furnace;
sulfurizing by causing thermal reaction between sulfur and said metallic precursors in a sulfurization reaction in said furnace after said selenization reaction, said sulfurizing step including causing said sodium vapor to react with said metallic precursors; and
annealing after said selenization reaction.
13. The method as in claim 12 , wherein said sulfurizing is carried out after said annealing and at a lower temperature than said annealing and said annealing is carried out at a higher temperature than said selenization reaction.
14. The method as in claim 12 , wherein said sulfurization includes causing said sodium vapor to react with said metallic precursors by delivering a sulfur-containing gas mixture and said sodium vapor, to said furnace.
15. The method as in claim 12 , wherein said vaporizing includes directing a carrier gas to a vaporizer unit, said sodium vapor comprises a sodium vapor stream, said sulfurizing includes delivering said sodium vapor stream to said furnace, wherein said carrier gas comprises one of H 2 S, H 2 Se, N 2 and Ar.
16. The method of claim 15 , wherein said carrier gas comprises H 2 S.
17. The method of claim 12 , wherein said sulfurizing is performed after said annealing.
18. The method of claim 12 , wherein said sulfurizing is performed at a lower temperature than said annealing.
19. The method of claim 12 , wherein said annealing is performed at a higher temperature than said selenization reaction.
20. The method of claim 12 , wherein said sulfurization includes delivering a sulfur-containing gas mixture and said sodium vapor to said furnace.