Study of oxygen/tetraethoxysilane plasmas in a helicon reactor using optical emission spectroscopy and mass spectrometry

Oxygen/tetraethoxysilane (O₂/TEOS) plasmas created in a low-pressure (2 mTorr) rf helicon reactor have been studied by optical emission spectroscopy and mass spectrometry as a function of the rf (13.56 MHz) power injected into the plasma, which is varied from 25 to 300 W. Complementary measurements for the interpretation of the mass spectrometric data have also been carried out using the threshold ionization mass spectrometry technique. It is shown that valuable information on the parent molecules is obtained by both optical emission spectroscopy and threshold ionization mass spectrometry techniques. At low rf power TEOS molecules and organic compounds like hydrocarbons (CH₄, C₂H₂) and alcohols (CH₃CH₂OH) as well as H₂, H₂O, CO, O₂, CO₂ are observed. At high rf power TEOS and O₂ molecules are totally or mostly depleted, the share of hydrocarbons decreases and carbon monoxide, carbon dioxide, water and hydrogen become the essential parts of the gas phase.