Physical mechanism of work function modulation due to impurity pileup at Ni-FUSI/SiO(N) interface

The physical mechanism of work function modulation caused by impurity pileup at Ni-FUSI/SiO(N) interface were investigated. We proposed and verified a new model which can explain the Phim-eff modulation both nMOS (As P and Sb) and pMOS (B). In our model, the position and concentration of impurity at interface determine the direction and the extent of Phim-eff modulation. We have also developed a new method to introduce impurity atoms at the interface after FUSI gate formation, in which the amount of Phim-eff modulation is higher than that for the conventional process