Plasma chemistry of He/O2/SiH4 and He/N2O/SiH4 mixtures for remote plasma-activated chemical-vapor deposition of silicon dioxide

Publisher Website
Google Scholar
Abstract
Remote plasma‐activated chemical‐vapor deposition (RPACVD) provides a means to deposit thin dielectric films with low ion bombardment and while having high selectivity in generating precursors. In RPACVD of SiO2, gas mixtures of He/O2 or He/N2O are passed through a plasma, producing radicals and excited states that are mixed with silane downstream. Excited states produced in the plasma and precursor species produced by these reactions then flow to the substrate. Although high‐quality SiO2 films can be produced by RPACVD, the gas‐phase deposition precursors have not been identified. A two‐dimensional plasma chemistry model is described, and results from that model are used in a discussion of possible gas‐phase precursors for SiO2 deposition. In particular, the formation and transport of silanols (SiH2O and SiH3O) are examined as a function of gas mixture, power deposition, and geometry. It is found that the fluxes of SiH2O, SiH3O, and SiH3 are sufficient to account for the observed deposition rates; while systematic dependencies of the fluxes of HSiO and SiO discount them as being deposition precursors. He/N2O/SiH4 mixtures differ from He/O2/SiH4 mixtures by providing larger fluxes of SiH3 to the substrate, while the fluxes of SiH2O, SiH3O, and O2(1Δ) are significantly less.