Effect of Ni Thickness Dependence on NiSi FUSI Metal Gate Characteristics

Effect of Ni thickness on NiSi fully silicided (FUSI) metal gate material and device characteristics were investigated using X-ray diffraction, cross-sectional transmission electron microscopy, sheet resistance, and device capacitance-voltage (C-V) and current-voltage measurements. 450, 600, and 750 Å Ni thicknesses were employed for full silicidation study of 800 Å poly-Si gate on The theoretically calculated Ni thickness (450 Å) for full silicidation of 800 Å poly-Si is insufficient, resulting in partial silicidation at the interface. Excess Ni thickness (750 Å) forms Ni-rich FUSI with higher sheet resistance than NiSi. It is also shown that the amount of flatband voltage shift in C-V and hence the metal gate work function remains constant once the total silicidation is achieved. No degradations to the interface as well as the electrical properties of gate dielectrics are observed with excess Ni.