Oxygen diluted hexamethyldisiloxane plasmas investigated by means of in situ infrared absorption spectroscopy and mass spectrometry

The gas phase species produced in rf plasmas of hexamethyldisiloxane (HMDSO ), Si2O(CH3)(6), diluted with oxygen, have been investigated. The complemen tarity of Fourier transform infrared absorption spectroscopy and mass spect rometry allows the determination of the most abundant neutral components pr esent in the discharge. The measurements reveal that methyl groups (CH3), a bundantly formed by the dissociation of the HMDSO molecule, are the precurs or for the most abundant species which stem from two kinds of reaction. The first kind of reaction is combustion of CH3 by oxygen-producing formaldehy de (COH2), formic acid (CO2H2), carbon monoxide (CO), carbon dioxide (CO2) and water. It is shown that high mass carbonated radicals, such as SixOyCzH t, first diffuse to the surface and then the carbon is removed by oxygen et ching to form CO2. The second is hydrocarbon chemistry promoted by CH3, pro ducing mainly hydrogen (H-2), methane (CH4) and acetylene (C2H2).