Understanding plasma enhanced chemical vapor deposition mechanisms in tetraethoxysilane-based plasma

The mechanisms of plasma-enhanced chemical vapor deposition using tetraethoxysilane (TEOS)-based plasma were investigated by monitoring the plasma via experimental and computational approaches using a quadrupole mass spectrometer/residual gas analyzer and coupled plasma-gas flow simulation. For experimental measurements, plasma was generated from a TEOS/inert gas mixture, that is, Ar/TEOS or He/TEOS. The results showed that a larger number of TEOS fragments (i.e., silicon complex species) were generated in the He/TEOS plasma than in the Ar/TEOS plasma. Plasma simulation showed that the He/TEOS plasma has a higher electron temperature than the Ar/TEOS plasma, enhancing the dissociation reactions by electron impact. The spatial distributions of TEOS fragments of this mixture observed in the plasma simulation showed that the number of TEOS fragments reaching the wafer surface increased as the O2 ratio of the gas mixture increased. However, a further increase in the O2 flow rate beyond a certain ratio caused the number of signals to decrease. This is attributed to the changes in the determining step from the gas-phase reaction of SiO production to the diffusion of SiO from the portion near the inlet. We also found that metastable species such as Ar*, O2*, and O* are the main contributors to the generation of atomic oxygen (O), which is closely related to the high deposition rate.