The Effect of an Yttrium Interlayer on a Ni Germanided Metal Gate Workfunction in $\hbox{SiO}_{2}/\hbox{HfO}_{2}$

In this letter, the tuning of a nickel fully germanided metal gate effective workfunction via a hyperthin yttrium (Y) interlayer at the bottom of the metal electrode was demonstrated on both SiO
₂
and HfO
₂
. By varying the Y interlayer thickness from 0 to 9.6 nm, a full range of workfunction tuning from 5.11 to 3.65 eV has been achieved on NiGeY/SiO
₂
stacks. It was also found that the chemical potential of the material that is adjacent to the gate electrode/gate insulator plays an important role in the determination of the effective workfunction. This work-function tuning window was observed to decrease to a range of 5.08-4.25 eV on NiGeY/HfO
₂
stacks.