Internal Photoemission over HfO₂ and Hf(1-x)SixO₂ High-k Insulating Barriers: Band Offset and Interfacial Dipole Characterization

The band offsets at HfO 2 and Hf (1- x ) Si x O 2 high- k oxide interfaces with an aluminum metal gate and a silicon substrate have been characterized in detail by using internal photoemission spectroscopy. The quantitative comparison of the extracted energies on both sides of band offsets in the hafnium oxide, those in pure silicon oxide, suggests the presence of an interfacial dipole located at the HfO 2 /SiO 2 interface, which becomes less significant by adding silicon inside the HfO 2 film. Through the combination of internal photoemission and spectroscopic ellipsometry experiments, the band diagrams of Hf (1- x ) Si x O 2 films were determined for different silicon concentrations. This study shows that Si 3s and Hf 5d states give independent contributions to the conduction band.