Gas-phase kinetics in atmospheric-pressure plasma-enhanced chemical vapor deposition of silicon films

Atmospheric-pressure (AP) plasma-enhanced chemical vapor deposition of silicon (Si) films was numerically simulated. The AP plasma used for Si depositions was excited by a 150-MHz very high-frequency (VHF) electric power, which was capable of generating continuous glow discharges covering the entire electrode surface. The experimental film thickness profiles could be well fitted by the simulations by adjusting the electron density in the plasma. The results showed that, although neutral-neutral reactions proceed very rapidly due to the frequent collisions between the gas species, the dissociation of the source SiH4 molecules by electron impact is the key factor that governs the chemistry occurring in the AP-VHF plasma and promotes the film growth on the substrate. The input power dependences of electrical property of the Si films could be explained by the contribution of SiH3 radical to the deposition. It was also shown that, even though the plasma was continuous glow, the electron density changed in the direction of gas flow, suggesting that the very rapid nucleation of clusters and their growth into nanoparticles were occurring in the AP-VHF plasma.