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Dual-work-function metal gates fabricated by full silicidation (FUSI) of Co-Ni bi-layer with doped poly-Si were investigated for the first time, along with single-metal FUSI systems of CoSi2 and NiSi. Complete conversion of poly-Si into Co-Ni alloy silicided metal gate (FUSI) CoxNi1-xSi2 was demonstrated. Although a linear relationship between work function and Ni percentage was observed for FUSI of undoped poly-Si systems, the work functions of doped CoxNi1-xSi2 are almost identical to those of doped NiSi FUSI metal gates. The alloy FUSI metal gates explored in this letter provide a new class of metal gates for CMOS devices that combine the advantages of both NiSi and CoSi2, i.e., proper work function tunability of NiSi and high thermal stability of CoSi2.