Improvement in Thermal Stability of Nickel Silicides Using NiNx Films

A nickel nitride (NiN x ) film is proposed as a Ni source for silicidation to improve the thermal stability of a nickel silicide (NiSi) layer. The stability of the film was investigated for temperatures above 700°C. The nitrogen content in the NiN x film could be controlled by varying the N 2 flow ratio during deposition. When the NiN x film was annealed, the formation temperature of the NiSi layer was higher than that of layers formed from the pure Ni film due to the retardation of Ni diffusion into the Si substrate by an amorphous Si-N layer at the nickel nitride/Si interface. After an additional annealing above 700°C, the sheet resistances (R s ) of the NiSi layers formed from the NiN x film remained low, while the R s of those formed from the pure Ni film increased sharply. Apparently, the suppression of the agglomeration of the NiSi layer by the utilization of the NiN x film can improve its thermal stability.