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 an ultrahigh vacuum environment. At the temperature of 750 ^\circC, HfO₂ films begin to decompose. After being further annealed at 850 ^\circC 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 result in the films grown subsequently to be loosened, and thereby leads to a relatively low decomposition temperature.