Thermal stability of HfO2/Si (001) films prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen

HfO2 films on silicon substrates have been prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen. Synchrotron radiation photon-electron spectroscopy was used to investigate the thermal stability of HfO2 films under and ultrahigh vacuum environment. At the temperature of 750 degrees C, HfO2 films begin to decompose. After being further annealed at 850 degrees C for 3 min, HfO2 films decomposes completely, partially to form Hf-silicide and partially to form gaseous HfO. Two chemical reactions are responsible for this decomposition process. A small amount of Hf-silicide, which is formed at the very beginning of growth, may results in the films grown subsequently to be loosened, and thereby leads to a relatively low decomposition temperature.