Chemical etching of thin SiO _x C _y H _z films by post-deposition exposure to oxygen plasma

SiO _x C _y H _z films deposited in a O ₂ /TEOS plasma are post-exposed to an oxygen plasma. Real-time ellipsometric measurements combined with optical emission spectroscopy show a strong etching of the film in the first minutes. Spectroscopic ellipsometry, transmission electron microscopy (TEM) and Auger spectroscopy evidence structural modifications over several 10 nanometers. It is also shown that chemical reactions with O atoms are responsible for most of this effect and that during a deposition process there is really competition between deposition and etching by O atoms.