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

Epitaxial growth of a NiSi(2) layer was observed on S(+) ion-implanted Si(100) at a low temperature of 550 degrees C. Depending on the S(+) dose and the Ni thickness, we identified different nickel silicide phases. High quality and uniform epitaxial NiSi(2) layers formed at temperatures above 700 degrees 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 NiSi(2) 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.