Precise determination of metal effective work function and fixed oxide charge in MOS capacitors with high-κ dielectric

Effective metal work function, Φm,eff, and oxide charge, Qox, were determined on MOS capacitors with slanted high-κ dielectric. Φm,eff and Qox were extracted using flat-band voltage shift versus equivalent oxide thickness data, both deduced from the capacitance–voltage measurements. Slanted HfSiOx dielectric (initial thickness was 9 nm) was prepared by gradual etching in HF-based solution. As a metal electrode, thin Ru-films were deposited by MOCVD-derived technique—Atomic Vapor Deposition® on the slanted HfSiOx as well as SiO2 dielectrics. The Φm,eff of Ru was found to be 4.74 and 4.81 eV for Ru/HfSiOx and Ru/SiO2 gate stacks, respectively. Ultraviolet photoelectron spectroscopy yields the work function of 4.62 eV in agreement with the capacitance–voltage data. We also studied the I–V characteristics of the Ru/HfSiOx/Si MOS capacitors. The barrier height was found to be constant within the HfSiOx bulk.