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

Abstract

Nickel fully-silicided (FUSI) gate work function Φm 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 NiFUSI gate Φm (4.01 - 4.11 eV) were obtained in a gate-first process flow (950 or 1000°C anneal) by an inserted ultra-thin (∼1 nm) interlayer on SiO2 dielectric. We further demonstrate that gate-first implementation of the interlayers in a XiSi/HfO2 gate stack can realize a low Φm of ∼4.28 eV without dopant incorporation or Ni-alloying. In addition, NiSi Φm modulation between Si midgap and band edge could be achieved by varying the interlayer thickness or Ni-silicide phase. © 2007 IEEE.