Spatial distributions of the absolute CF and CF2 radical densities in high-density plasma employing low global warming potential fluorocarbon gases and precursors for film formation

Abstract

Behaviors of gas species in electron cyclotron resonance (ECR) plasmas employing low global warming potential fluorocarbon gases of hexafluorobutadiene (C4F6) and hexafluoropropene (C3F6) with unsaturated carbon bonds together with the conventional octafluorocyclobutane (c-C4F8) are investigated. The spatial distributions of the absolute CF and CF2 radical densities are measured by combining the single-path infrared diode laser absorption spectroscopy and laser-induced fluorescence techniques. CF2 radicals have hollow-type distributions at all conditions in the ECR plasma reactor. However, the spatial distribution of the CF radical density differs greatly from that of the CF2 radical density. Behaviors of carbon atoms measured by vacuum ultraviolet absorption spectroscopy disagree with those of CF and CF2 radical densities. The behaviors of ion and fluorine species and the gas pressure in the plasma have been also evaluated. Fluorocarbon films with low dielectric constant of about 3.0 are deposited at a h...