Wet oxidation

Abstract
We present results of calculations relating to the transport processes controlling wet oxidation of silicon. Our calculations, by the CNDO self-consistent molecular orbital method, relate to interstitial diffusion of the water molecule. They indicate that, in quartz, the molecule can diffuse in a spiral motion along the open c-axis channels. The motion energy predicted is small (∼ 0·2 eV if ionic polarization is ignored) and the incorporation energy significantly larger (∼1·75 eV, ignoring ionic polarization). The sum of the two is distinctly greater than the observed Arrhenius energy of about 0·8 eV. Possible explanations are discussed, the most likely being a significant ionic polarization energy estimated by separate methods to be about 0·9–1 eV in the incorporation energy. Another possibility involves the association of pairs of water molecules to form dimers which diffuse through the oxide.

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