Lateral Ge segregation and strain evolution in SiGe alloys during the formation of nickel germano-silicide on a relaxed Si_(0.73)Ge_(0.27) epilayer

摘要

Ge segregation and strain evolution in the SiGe alloys during the formation of nickel germano-silicide on a relaxed Si_(0.73)Ge_(0.27) epilayer are studied in temperature range of 300-900 ℃. The continuous NiSiGe film on SiGe epilayer is formed at 500 ℃ and below, which applies tensile stress on the underlying unreacted SiGe layer. When temperature rises to 600 ℃ and above, the NiSiGe film begins to agglomerate, resulting in the formation of Ge-rich SiGe regions scattering among NiSiGe grains in the surface due to Ge lateral segregation from NiSiGe. During these processes, Ge is preferentially rejected from the NiSiGe grains giving rise to the transformation of NiSiGe to NiSi with increase of temperature and the increase of Ge content in the Ge-rich SiGe at the NiSiGe grain boundaries. The enlarged lattice constant of Ge-rich SiGe and the volume expansion of NiSiGe grains make the Ge-rich SiGe alloy under compressive strain. No significant Ge segregation is observed between Ni(SiGe) and the underlying SiGe layer even at higher temperature.