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 process for forming a strained semiconductor layer over a substrate, the process comprising:
forming an epitaxial Ge-containing layer on a substrate, wherein the epitaxial Ge-containing layer has a germanium content in the range of about 50 atomic percent to about 100 atomic percent; and
depositing a strained epitaxial semiconductor layer over the epitaxial Ge-containing layer by chemical vapor deposition using a deposition gas comprising trisilane.
2. The process of claim 1 in which depositing the strained epitaxial semiconductor layer comprises depositing a strained epitaxial Si layer.
3. The process of claim 2 in which depositing the strained epitaxial semiconductor layer comprises depositing the strained epitaxial Si layer onto a cure Ge layer.
4. The process of claim 1 in which depositing comprises maintaining the substrate at a temperature in the range of about 325° C. to about 475° C.
5. The process of claim 1 in which depositing comprises maintaining a deposition pressure in the range of about 1 Torr to about 100 Torr.
6. The process of claim 1 comprising depositing the strained epitaxial semiconductor layer at a deposition rate in the range of about 5 Å/minute to about 50 Å/minute.
7. The process of claim 1 in which depositing is conducted in a single-wafer, horizontal gas flow reactor.
8. The process of claim 1 in which the substrate comprises a single crystal Si layer.
9. A process for forming a strained semiconductor layer over a substrate, the process comprising:
providing a single crystal Si substrate in a single-wafer, horizontal gas flow reactor;
depositing an epitaxial Ge-containing layer on the single crystal Si substrate; and
depositing a strained epitaxial semiconductor layer onto the epitaxial Ge-containing layer by chemical vapor deposition using a deposition gas comprising trisilane, wherein the substrate is maintained at a temperature between about 325° C. and about 475° C. during deposition of the strained epitaxial semiconductor layer.
10. The process of claim 9 , further comprising heating the substrate after depositing the strained epitaxial semiconductor layer, wherein heating the substrate comprises increasing the temperature of the substrate to a temperature in the range of about 400° C. to about 525° C.
11. The process of claim 9 in which depositing the strained epitaxial semiconductor layer comprises maintaining a deposition pressure in the range of about 1 Torr to about 100 Torr.
12. The process of claim 1 , wherein the epitaxial Ge-containing layer has a germanium content of about 99 atomic percent or higher.
13. The process of claim 9 , wherein the deposited epitaxial Ge-containing layer has a germanium content in the range of about 50 atomic percent to about 100 atomic percent.
14. The process of claim 9 , wherein the deposited epitaxial Ge-containing layer has a germanium content of about 99 atomic percent or higher.
15. A method comprising:
providing a substrate in a reaction chamber, wherein an epitaxial germanium-containing layer is provided on the substrate; and
depositing a strained epitaxial semiconductor layer over the germanium-containing layer by chemical vapor deposition using a deposition gas comprising trisilane, wherein the strained epitaxial semiconductor layer is deposited at a deposition rate between about 5 Å min −1 and about 50 Å min −1 , and at a temperature between about 325° C. and about 475° C.
16. The method of claim 15 , wherein the epitaxial germanium-containing layer has a germanium content in the range of about 50 atomic percent to about 100 atomic percent.
17. The method of claim 15 , wherein the epitaxial germanium-containing layer has a germanium content greater than about 99 atomic percent.
18. The method of claim 15 , wherein depositing the strained epitaxial semiconductor layer comprises delivering trisilane to the reaction chamber at a flow rate between about 5 mg min −1 and about 50 mg min −1 .