Investigating Physical and Electrical Changes in Ni-FUSI/SiO2 Gate Stacks

The thermal stability and phase characteristics for the Ni-FUSI formed on SiO₂ gate dielectrics by a novel integration process were investigated. The electrical resistivity and surface morphology of Ni/Si layers at varies of annealing temperatures were examined by X-ray diffraction (XRD), sheet resistance, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The structure of the formed nickel silicide films undergoes a transformation of a low resistivity-NiSi to a high resistivity-NiSi₂ phase with increasing of annealing temperature. It has been found that a mixed-phase of Ni₂Si, NiSi and NiSi₂ was commonly observed during phase transformation. Complete conversion of intermediate silicide phases to the final NiSi₂ phase by a unique integration process to achieve NiSi phase stabilize at temperature 900degC and delay the agglomeration. The focus of present work is to facilitate the correlations of Ni-Si phase transformation with its electrical and morphological properties.