High-k dielectric layers (HfSixOy and ZrO2) with different film morphologies were investigated by tunneling atomic-force microscopy (TUNA). Different current distributions were observed for amorphous and nanocrystalline films by analyzing TUNA current maps. This even holds for crystalline layers where highly resolved atomic-force microscopy cannot detect any crystalline structures. However, TUNA enables the determination of morphology in terms of differences in current densities between nanocrystalline grains and their boundaries. The film morphologies were proven by high-resolution transmission electron microscopy. The investigations show TUNA as powerful current mapping tool for the characterization of morphology in thin high-k films on a nanoscale.

We have investigated the electrical behavior of high permittivity (high-k) hafnium–titanium–silicate $({\mathrm{Hf}}_x{\mathrm{Ti}}_y{\mathrm{Si}}_z\mathrm{O})$ layers with different Hf:Ti ratios in the films. The films are prepared by metalorganic chemical vapor deposition using a mixture of two single source precursors. Oxide and interface charges, leakage currents and conduction mechanisms are found to be a strong function of the film composition. The films with Hf content less than 10 at. % show lower levels of oxide and interface charges and higher dielectric constant whereas those with Hf content higher than 15 at. % have better leakage current properties. A strong evidence is presented that in films with Hf content lower than 10 at. % the conduction process is governed by a phonon-assisted tunneling, i.e., it is defined rather by the intrinsic properties of the material than by its defect structure.