Estimation of fixed charge densities in hafnium-silicate gate dielectrics

In this paper, an effective technique and methodology for the estimation of fixed charge components in high-k stacks was demonstrated by varying both the SiO₂ and high-k dielectric thicknesses. The SiO₂ thickness was scaled on a single wafer by uniformly changing the etch time of a thermally grown SiO₂ layer across the wafer. This minimized wafer-to-wafer variations and enables acquisition of statistically significant datasets. Layers with different thickness of both the nitrided and non-nitrided hafnium-silicate layers were then grown on these wafers to estimate all the interfacial and bulk charge components. The reproducibility and validity of this technique were demonstrated, and this method was used to compare the fixed charge levels in Hf-silicates (HfSiO) and nitrided-Hf-silicate (HfSiON) layers.