Yttrium- and Terbium-Based Interlayer on SiO2 and HfO2 Gate Dielectrics for Work Function Modulation of Nickel Fully Silicided Gate in nMOSFET

Novel yttrium- and terbium-based interlayers (Y_IL and Tb_IL, respectively) on SiO₂ and HfO₂ gate dielectrics were employed for NMOS work function Phi_m modulation of undoped nickel fully silicided (Ni-FUSI) gate. Bandedge Ni-FUSI gate Phi_m of ~4.11 and ~4.07 eV was obtained by insertion of ultrathin (~1 nm) Y_IL and Tb_IL, respectively, on the SiO₂ gate dielectric in a gate-first process (with 1000 degC anneal). NiSi Phi_m on SiO₂ could also be tuned between the Si midgap and the conduction bandedge E_C by varying the interlayer thickness. The achievement of NiSi Phi_m around 4.28 eV on the HfO₂ gate dielectric using interlayer insertion makes this an attractive Phi_m modulation technique for Ni-FUSI gates on SiO₂ and high-k dielectrics