Investigation of Polycrystalline Nickel Suicide Films as a Gate Material

The work function of polycrystalline nickel suicide IiIm formed by rapid thermal annealing (RTA) has been studied using capacitance-voltage (C-V) measurements and metal-oxide semiconductor (MOS) structures. The effect of sintering temperature on work function has also been studied. Results show that the work function of n⁺-doped NiSi gate is about 4.6 eV and is stable from 400 to 800°C. For p⁺-doped NiSi gate, the work function is 5 eV. The gate-substrate leakage current is small and the oxide quality is similar to that in Al-gate MOS capacitors even for oxides as thin as 8 nm. The poly-gate depletion effect (PDE) has also been investigated by quasi-static C-V. Compared with that of poly-Si and poly-Si_1-xGe_x, no PDE is observed in suicide-gate n-MOS device even when the gate is undoped. The results suggest that nickel suicide film may be used as a potential gate material in complementary MOS or thin-lilm transistor devices.