Dual-work-function metal gates by full silicidation of poly-Si with Co-Ni bi-Layers

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 CoSi/sub 2/ and NiSi. Complete conversion of poly-Si into Co-Ni alloy silicided metal gate (FUSI) Co/sub x/Ni/sub 1-x/Si/sub 2/ 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 Co/sub x/Ni/sub 1-x/Si/sub 2/ 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 CoSi/sub 2/, i.e., proper work function tunability of NiSi and high thermal stability of CoSi/sub 2/.