Epitaxial growth of NiSi₂ induced by sulfur segregation at the NiSi₂/Si (100) interface

Epitaxial growth of a NiSi₂ layer was observed on S⁺ ion-implanted Si(100) at a low temperature of 550°C. Depending on the S⁺ dose and the Ni thickness, we identified different nickel silicide phases. High quality and uniform epitaxial NiSi₂ layers formed at temperatures above 700°C with a 20-nm Ni on high dose S⁺ implanted Si(100), whereas no epitaxy was observed for a 36-nm Ni layer. We assume that the presence of sulfur at the silicide/Si(100) interface favors the nucleation of the NiSi₂ phase. The S atom distributions showed ultrasteep S depth profiles (3 nm/decade) in the silicon, which results from the snow-plow effect during silicidation and the segregation of S to the interface due to the low solubility of S in both Si and the silicide.