Improvement in Thermal Stability of Nickel Silicides Using NiNx Films

Abstract

A nickel nitride (NiNx) 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 degrees C. The nitrogen content in the NiNx film could be controlled by varying the N-2 flow ratio during deposition. When the NiNx 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 degrees C, the sheet resistances (R-s) of the NiSi layers formed from the NiNx 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 NiNx film can improve its thermal stability.