Epitaxial growth of relaxed silicon germanium layers
View Patent ↗A relaxed silicon germanium structure comprises a silicon buffer layer produced using a chemical vapor deposition process with an operational pressure greater than approximately 1 torr. The relaxed silicon germanium structure further comprises a silicon germanium layer deposited over the silicon buffer layer. The silicon germanium layer has less than about 10 7 threading dislocations per square centimeter. By depositing the silicon buffer layer at a reduced deposition rate, the overlying silicon germanium layer can be provided with a “crosshatch free” surface.
1. A method of producing a relaxed silicon germanium structure, the method comprising:
epitaxially depositing a silicon-containing layer using a chemical vapor deposition process with an operational pressure greater than approximately 1 torr; and
heteroepitaxially depositing a germanium-containing layer over the silicon-containing layer, wherein the germanium-containing layer has a lattice constant that differs from a lattice constant of the silicon-containing layer, and wherein the germanium-containing layer has a surface roughness that is less than approximately 3 nm rms; and
relaxing the germanium-containing layer.
2. The method of claim 1 , further comprising tuning a process parameter so as to provide the germanium-containing layer with a crosshatch free surface topology, wherein the process parameter is selected from the group consisting of carrier flow rate, silicon-containing layer deposition rate, silicon-containing layer deposition temperature, and silicon-containing layer point defect density.
3. The method of claim 1 , wherein the germanium-containing layer is a crosshatch free layer.
4. The method of claim 1 , wherein the silicon-containing layer has a thickness less than approximately 2 nm.
5. The method of claim 1 , wherein the silicon-containing layer has a thickness between approximately 1 nm and approximately 2 nm.
6. The method of claim 1 , wherein the germanium-containing layer has a surface roughness that is less than approximately 2 nm rms.
7. The method of claim 1 , wherein the germanium-containing layer has a surface roughness that is less than approximately 1.5 nm rms.
8. The method of claim 1 , wherein the silicon-containing layer is deposited at a growth rate of less than approximately 0.50 nm min −1 .
9. The method of claim 1 , wherein the silicon-containing layer is deposited at a growth rate of less than approximately 0.20 nm min −1 .
10. The method of claim 1 , wherein the silicon-containing layer is deposited at a temperature between approximately 630° C. and approximately 670° C.
11. The method of claim 1 , further comprising depositing a strained silicon layer over the germanium-containing layer, wherein the strained silicon layer and the germanium-containing layer are deposited in situ within a single process chamber.
12. The method of claim 1 , wherein relaxing comprises continuing heteroepitaxially depositing the germanium-containing layer until the layer has a thickness greater than the critical thickness.