Ni/sub x/Ta/sub 1-x/Si and Ni/sub x/Pt/sub 1-x/Si ternary alloys for work function tuning on SiO/sub 2/, HfSiO/sub x/ and HfO/sub 2/ dielectrics

We present two new ternary alloy silicides with tunable work function ranging between 4.27eV to 4.7eV and 4.8eV to 5.0eV respectively for dual metal gate CMOS applications. Ni_xTa_1-xSi gates were investigated for NMOS and Ni_xPt_1-xSi gates were investigated for PMOS applications on SiO₂, HfO ₂ and HfSiO_x dielectrics. A large degree of tuning was observed on SiO₂ however the tuning range decreased as Hf content of the dielectric increased. It was also found that the thermal stability of nickel silicide was enhanced due to the incorporation of tantalum. Device results demonstrate thermally stable characteristics at 900degC, making them eligible candidate for gate first application. X-ray diffraction (XRD) confirmed presence of alloy silicide phases that were responsible for the work function tuning