Room temperature, ion energy-controlled deposition of silicon nitride films in a SiH₄-N₂ plasma

Abstract

In this study, silicon nitride films were deposited in SiH₄-N₂ plasma using a plasma-enhanced chemical vapor deposition system at room-temperature. The radio frequency bias power impact on the films characteristics (deposition rate, refractive index, and surface roughness) was examined. Ion energy information (energy level, energy flux) collected using an ion energy analysis system was correlated with the film characteristics. Increasing the bias power increased the ion energy, more noticeably with the high ion energy. For the same variations in the bias power, the ion energy flux initially decreased considerably and then varied little. A similar variation was noticed in both film characteristics. Both the deposition rate and the refractive index were strongly correlated with the ratio of high ion energy to low ion energy rather than high or low ion energy. A similar dependency was also observed for the refractive index. The dependency of surface roughness changed from ion energy to ion energy flux. The roles of the ion energy flux were further examined by implicating them in AFM images. The low ion energy flux was identified as a contributor to the extreme peaks that significantly deteriorated the surface roughness. The highest deposition rate, highest refractive index, and smallest surface roughness obtained were 183 Å/min, 2.06, and 0.230 nm, respectively.