Nondestructive investigation of interface states in high‐ k oxide films on Ge substrate using X‐ray absorption spectroscopy

The unoccupied electronic structures of 5 nm thick high permittivity ( k ) oxides (HfO 2 , ZrO 2 , and Al 2 O 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 2 O 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. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)