Growth of thin SiO2 films on clean Si (111) surfaces by low-pressure oxidation and their evaporation

Abstract

The growth kinetics of SiO2 films on clean Si (111) surfaces in dry oxygen at pressures up to 10−3 Torr and temperatures between room temperature and 850°C and the thermal evaporation kinetics of the SiO2 from the Si substrates at temperatures between 705 and 750°C in UHV are studied using Auger electron spectroscopy. There is no SiO2 growth at room temperature. The sensitivity ratio of the L2,3 VV Auger peak of Si to that of Si in SiO2 is found to be ≈ 8. Using this and ellipsometry the mean escape depths of electrons in SiO2 are determined to be (11 ± 4) Å and (16 ± 4) Å for electron energies of 76 to 91 eV and 512 eV, respectively. For film thicknesses up to 50 Å, on oxidation an initial fast and then a linear growth with an activation energy of 0.6 eV is found. For the fast part of the SiO2 evaporation likewise investigated an activation energy of 3.5 eV could be observed. The work experimentally confirms predictions of Ghez and van der Meulen for the oxidation mechanism of Si in the linear growth region.