Compositional dependence of work function and Fermi level position of the HfN x/SiO 2 system

Abstract

In situ Kelvin Probe (KP) measurements performed on HfN x showed an increase of the vacuum work function as a function of N content from a value of 3.9 eV (silicon conduction band edge) for pure Hf to a value of 5 eV (silicon valence band edge) for x ∼ 2. In contrast, capacitance–voltage ( C– V) measurements showed that the effective work function increased only until x < 1 and saturated around a value of 4.6 eV (silicon midgap). This behavior is attributed to Fermi level pinning, which is probably due to oxidation of the HfN x during the reactive sputtering deposition step.