Chemistry and band offsets of HfO2 thin films on Si revealed by photoelectron spectroscopy and x-ray absorption spectroscopy

High-resolution photoelectron spectroscopy and x-ray absorption spectroscopy (XAS) measurements have been performed on HfO2 films grown on Si(0 0 1) for ULSI ultra-thin gate insulators to elucidate the chemistry and band offsets of interfacial silicate layers. The valence-band discontinuity is determined by subtracting valence-band spectra of H-terminated Si(0 0 1) from those of the HfO2 films on Si which have a HfO2/Hf1-xSixO2/Si double layer structure. On the other hand, the conduction-band discontinuity is clearly deduced by oxygen K-edge absorption spectra and O 1s photoelectron spectra. Consequently, two kinds of energy-band offsets of HfO2/Hf1-xSixO2 and Hf1-xSixO2/Si are determined separately. (C) 2004 Elsevier B.V. All rights reserved.