Epitaxial semiconductor deposition methods and structures
View Patent ↗Methods for depositing epitaxial films such as epitaxial Ge and SiGe films. During cooling from high temperature processing to lower deposition temperatures for Ge-containing layers, Si or Ge compounds are provided to the substrate. Smooth, thin, relatively defect-free Ge or SiGe layers result. Retrograded relaxed SiGe is also provided between a relaxed, high Ge-content seed layer and an overlying strained layer.
1. A method for forming a protective cap layer, the method comprising:
providing a strained epitaxial film; and
changing deposition conditions to provide a flow of a silicon precursor to the strained film to deposit a protective silicon cap layer having a silicon content of greater than 99.9% on the strained epitaxial film in situ at a deposition temperature between about 325° C. and about 475° C.
2. The method of claim 1 , wherein depositing the protective cap layer takes place at a deposition rate of between about 5 Å/min and about 50 Å/min.
3. The method of claim 1 , wherein the strained epitaxial film has a germanium content of about 99 atomic percent or higher.
4. The method of claim 1 , wherein the silicon precursor comprises trisilane.
5. The method of claim 4 , wherein providing a flow of the silicon precursor comprises flowing trisilane at a flow rate between about 5 mg/min to 50 mg/min.
6. The method of claim 1 , wherein providing a flow of the silicon precursor comprises maintaining a deposition pressure between about 1 Torr and 100 Torr.
7. A method of preventing agglomeration of a strained germanium-containing layer deposited on a relaxed buffer layer, the method comprising:
providing a structure having the strained germanium-containing layer deposited on the relaxed buffer layer;
providing a flow of a silicon precursor to the strained layer to deposit an epitaxial layer at a temperature between about 325° C. and about 475° C. to serve as a cap layer that prevents agglomeration of the strained germanium-containing layer, wherein the cap layer has a silicon content of greater than 99.9%.
8. The method of claim 7 , wherein depositing the epitaxial layer takes place at a deposition rate of between about 5 Å/min and about 50 Å/min.
9. The method of claim 7 , wherein the strained layer contains less than 1% silicon.
10. The method of claim 7 , wherein the relaxed buffer layer comprises SiGe.
11. The method of claim 7 , wherein the strained layer comprises a Ge layer.
12. The method of claim 7 , wherein the silicon precursor comprises trisilane.
13. The method of claim 7 , wherein providing a flow of the silicon precursor occurs at a deposition pressure between about 1 Torr and 100 Torr.
14. The method of claim 7 , further comprising increasing temperature to increase deposition speed after a sufficiently thick epitaxial layer is deposited at the deposition temperature between about 325° C. and about 475° C.
15. The method of claim 14 , wherein increasing temperature comprises reaching an elevated temperature between about 400° C. and about 525° C.