Spatial distributions of power and ion densities in RF excited remote plasma reactors

Remote plasma systems operating at moderate pressures (tens to hundreds of milli-Torr) are being developed for use in deposition and etching of microelectronics materials. In particular, remote plasma-enhanced chemical vapour deposition (RPECVD) has been investigated for fabrication of μc-Si, Si3N4 and SiO2 films, as well as for plasma cleaning and passivation. RPECVD reactors typically consist of a narrow upstream plasma zone and a wide downstream deposition chamber. A sub-set of the reactants is made to flow through the upstream plasma zone, creating excited states which are mixed with additional reactants injected into the downstream deposition chamber. RPECVD systems are typically excited by a radio frequency electric field produced by a coil surrounding the upstream plasma zone with the intent of generating a plasma that is well confined to the upstream zone. It is common, however, for the plasma to extend downstream towards the substrate due to stray inductive fields and capacitive coupling. In this paper, a computer model for remote plasma reactors is described, with which the spatial distributions of power deposition and ion densities are investigated. The characteristics of remote plasma reactors are presented and the influences of the operating conditions (geometry, gas pressure and RF frequency) on plasma confinement are investigated for He, O2 and He–SiH4 mixtures.