Effective work function engineering by sacrificial lanthanum diffusion on HfON-based 14 nm NFET devices

Abstract

In this paper, the impact of metallic lanthanum (La) deposited by Radio-Frequency PVD on effective work function (WFeff) of HfON-based NFET devices in a sacrificial metal gate-first approach is evaluated for the first time. Engineering of WFeff towards N+ without leakage degradation is demonstrated by tuning both the pedestal TiN thickness and the as-deposited metallic La dose. WFeff shift is related to a La-induced interfacial dipole (5), whose value has been correlated to the effective La dose into HfON/SiON stack after diffusion annealing, which has been accurately measured through a spectroscopic method based on La X-Ray Fluorescence (XRF).