FTIR Plasma Phase Analysis of Hexamethyldisiloxane Discharge in Microwave Multipolar Plasma at Different Electrical Powers

Summary: In this paper, the gas phase composition of hexamethyldisiloxane (HMDSO) microwave plasma at 4 × 10 −3 mbar and of the corresponding films were studied by FTIR spectroscopy under different power conditions. At low powers, species with a chemical structure very similar to that of HMDSO were observed in the gas phase, whereas the film essentially contained short [(CH 3 ) 2 SiO] n ‐like chains with a low branching rate and the end group Si(CH 3 ) 3 . At higher powers, the chemical entities present in the gas phase contained several (SiO) x  bonds, whereas the branching rate in the film increased with the amount of SiH, SiC and SiO bonds. The interpretation of these observations led to a proposal involving a chemical mechanism. In this mechanism, the increasing decomposition of HMDSO into by‐products, which themselves increasingly decompose as the power is raised, plays a determining role. Comparison of FTIR plasma and deposit spectra showing the relationship between the HMDSO by‐products present in the plasma phase and the different functional groups and end groups present in the deposited films. image Comparison of FTIR plasma and deposit spectra showing the relationship between the HMDSO by‐products present in the plasma phase and the different functional groups and end groups present in the deposited films.