Chemical vapor phase etching of polycrystalline selective to epitaxial Si and SiGe

Abstract

Combination of nonselective Si/SiGe growth with selective chemical vapor phase etching of poly-Si/SiGe was investigated with the aim to create epitaxial Si/SiGe in a selective manner. Directly after the nonselective deposition, an HCl vapor phase etching was performed within the same reactor (RPCVD) at different process conditions (HCl partial pressure, etching temperature) to remove the polycrystalline Si/SiGe selectively to the epitaxial material. Microloading effect of nonselective SiGe process was ignorable to that of selective SiGe process. Etching rate of poly-Si/SiGe was higher than that of epitaxial Si/SiGe. We found that there is a pattern size dependence of the etching process which becomes smaller by increasing HCl flow, indicating that high HCl flow condition is required for uniform epitaxial Si/SiGe thickness. Selectivity of polycrystalline to epitaxial Si/SiGe becomes higher with increasing etching temperature. The selectivity of polycrystalline to epitaxial etching for SiGe can be improved by adding a thin Si cap layer which will be partly removed during the etching process.