Yttrium- and Terbium-Based Interlayer on $ \hbox{SiO}_{2}$ and $\hbox{HfO}_{2}$ 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 SiO
₂
and HfO
₂
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 SiO
₂
gate dielectric in a gate-first process (with 1000 degC anneal). NiSi Phi
_m
on SiO
₂
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 HfO
₂
gate dielectric using interlayer insertion makes this an attractive Phi
_m
modulation technique for Ni-FUSI gates on SiO
₂
and high-k dielectrics