The unoccupied electronic structures of 5 nm thick high permittivity (k) oxides (HfO 2, ZrO 2, and Al 2O 3) and SiO 2 films on Ge substrates were examined using O K-edge X-ray absorption spectroscopy. Comparative studies with those on Si substrates showed contrasts in the conduction bands, which should be due to the formation of interface states. In the Al 2O 3 and SiO 2 films, GeO 2 layers are formed at the interface and they suppress in part the formation of detrimental germanate phases. In contrast, in the HfO 2 and ZrO 2 films, no signature of the Ge-oxide phase is observed but some germanate phases are expected to prevail, suggesting a degradation of the gate oxide characteristics.
- High-k dielectrics
- X-ray absorption spectroscopy