Alloying effects in Ni Silicide for CMOS applications

The solid-state reaction of Ni/Si in the presence of other elements is investigated. The alloying effects on both NiSi/Si Schottky contacts and Ni fully silicided (FUSI) gates on SiO₂ dielectric are studied by phase, composition, and electrical characterization tools. The results show that after silicidation Er, Y, and Al all segregated at the Ni-silicide surface rather than piled up at the Ni-silicide/Si interface due to their high affinity to oxygen, therefore little modulation of Schottky barrier height was observed. In contrast, Ho- and Er-alloyed Ni FUSI gates showed significant work function modulation, which could be related to the crystallinity change of the NiSi film in the presence of these elements.