Physical and electrical characterization of Ni–Si Phase transformation

The thermal stability and phase characteristics involved in processing nickel silicided films formed on three different gate dielectric layers (SiO2, HfSiO, and HfO2) were investigated. The electrical properties and surface morphology of Ni-Silicides formed by Ni–Si solid-state reaction were examined by X-ray diffraction (XRD), sheet resistance, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and capacitance–voltage (C–V) curves. Results show that the Ni-Silicide formations undergo a phase transformation from a low resistivity-NiSi to a high resistivity-NiSi2 phase, which has a strong dependence on annealing temperature despite underlying gate dielectric materials. It has been found that a mixed-phase of Ni2Si, NiSi and NiSi2 was commonly observed during phase transformation. A unique integration process was developed to obtain a thermally stable NiSi phase at high temperatures, which proved to delay the conversion of intermediate silicide phases to its terminal phase (NiSi2) effectively. The focus of the present work is to facilitate the correlations of Ni–Si phase transformation with its electrical and morphological properties.