Band edge NMOS work function for nickel fully-silicided (FUSI) gate obtained by the insertion of novel Y-, Tb-, and Yb-based interlayers

Nickel fully-silicided (FUSI) gate work function Phi_n, was successfully tuned for the first time by the insertion of novel yttrium-(Y) based, terbium-(Tb) based, or ytterbium-(Yb) based interlayer at the gate/dielectric interface. Band edge Ni-FUSI gate Phi_m, (4.01 -4.11 eV) were obtained in a gate-first process flow (950 or 1000degC anneal) by an inserted ultra-thin (~1 nm) interlayer on SiO₂ dielectric. We further demonstrate that gate-first implementation of the interlayers in a NiSi/HfO₂ gate stack can realize a low Phi_m, of ~4.28 eV without dopant incorporation or Ni-alloying. In addition, NiSi Phi_m, modulation between Si midgap and band edge could be achieved by varying the interlayer thickness or M-silicide phase.