Selective epitaxial formation of semiconductor films
View Patent ↗Epitaxial layers are selectively formed in semiconductor windows by a cyclical process of repeated blanket deposition and selective etching. The blanket deposition phases leave non-epitaxial material over insulating regions, such as field oxide, and the selective etch phases preferentially remove non-epitaxial material while deposited epitaxial material builds up cycle-by-cycle. Quality of the epitaxial material improves relative to selective processes where no deposition occurs on insulators. Use of a germanium catalyst during the etch phases of the process aid etch rates and facilitate economical maintenance of isothermal and/or isobaric conditions throughout the cycles. Throughput and quality are improved by use of trisilane, formation of amorphous material over the insulating regions and minimizing the thickness ratio of amorphous:epitaxial material in each deposition phase.
1. A method of selectively forming semiconductor material in semiconductor windows, comprising:
providing a substrate within a chemical vapor deposition chamber, the substrate comprising insulating surfaces and single-crystal semiconductor surfaces;
blanket depositing semiconductor material over the substrate to deposit non-epitaxial semiconductor material over the insulating surfaces and simultaneously deposit epitaxial semiconductor material over the single-crystal semiconductor surfaces of the substrate, wherein blanket depositing includes manipulating a thickness ratio of the non-epitaxial semiconductor material over the insulating surfaces to the epitaxial semiconductor material over the single-crystal semiconductor surfaces to be less than about 1.6:1; and
selectively removing the non-epitaxial semiconductor material from over the insulating surfaces,
wherein blanket depositing and selectively removing are conducted within the chemical vapor deposition chamber
further comprising repeating blanket depositing and selectively removing in a plurality of cycles, wherein each cycle adds to a thickness of epitaxial material over the single-crystal semiconductor surfaces.
2. The method of claim 1 , wherein the semiconductor material comprises carbon-doped silicon.
3. The method of claim 2 , wherein the carbon-doped silicon comprises between about 0.1 atomic % and 3.6 atomic % substitutional carbon.
4. The method of claim 1 , wherein the single-crystal semiconductor surfaces include recessed source/drain regions, and the epitaxial material exerts stress on an intermediate channel region.
5. The method of claim 4 , wherein selectively removing comprises removing epitaxial material from sidewalls of the recessed source/drain regions while leaving epitaxial material at bottoms of the recessed source/drain regions.
6. The method of claim 1 , wherein blanket depositing comprises forming predominantly amorphous semiconductor material over the insulating surfaces.
7. The method of claim 1 , wherein each blanket depositing step deposits a ratio of non-epitaxial material thickness over the insulating surfaces to epitaxial material thickness over the single-crystal semiconductor surfaces of between about 1.0:1 and about 1.3:1.
8. The method of claim 1 , wherein the epitaxial material comprises in situ phosphorus- and carbon-doped silicon.
9. The method of claim 1 , wherein selectively removing comprises flowing a germanium source and a halide source into the chemical vapor deposition chamber.
10. The method of claim 2 , wherein depositing further comprises forming a carbon-free capping layer over the carbon-doped silicon.
11. The method of claim 1 , wherein blanket depositing comprises non-selectively depositing.
12. The method of claim 1 , wherein blanket depositing comprises flowing vapor sources without halides.
13. The method of claim 1 , wherein the epitaxial material has a resistivity between about 0.4 mΩ·cm and 2 mΩ·cm.
14. The method of claim 1 , wherein blanket depositing comprises flowing trisilane into the chemical vapor deposition chamber.
15. The method of claim 1 , wherein blanket depositing further comprises flowing a suitable carbon source and a suitable electrical dopant source into the chemical vapor deposition chamber.
16. The method of claim 1 , wherein blanket depositing and selectively removing produces a net growth rate of the epitaxial semiconductor material of between about 4 nm/min and 11 nm/min.
17. The method of claim 1 , wherein blanket deposition comprises depositing between about 1 nm and 10 nm of the epitaxial semiconductor material in each cycle.
18. The method of claim 1 , wherein blanket depositing and selectively removing are isothermal and isobaric processes conducted in a chemical vapor deposition chamber.
19. The method of claim 4 , wherein the epitaxial material exerts lateral tensile strain on the intermediate channel region.