A study on the thermal stabilities of the NiGe and Ni_1-xTa _x Ge systems

The thermal stabilities of the Ni-silicide and Ni-germanide systems were compared, and that of the Ni0.9 Ta0.1 Ge alloy system was also studied. Although the NiSi film had a stable low sheet resistance (Rs) in the formation temperature range from 300 to 650°C, NiGe exhibited an abrupt increase of Rs from 500°C due to the severe agglomeration. The doping of the Ni film with Ta slightly improved the thermal stability of NiGe due to the formation of a Ta-rich layer on top of NiGe and subsequent reduction of the surface-free energy of NiGe with outside ambient. During the additional thermal annealing after NiGe formation, the germanide films formed from Ni-Ta alloy also exhibited slightly improved thermal stability characteristics as compared to the pure Ni-germanide system.