Vacuum ultraviolet-absorption spectroscopy and delocalized plasma-induced emission used for the species detection in a down-stream soft-etch plasma reactor

Vacuum ultraviolet-absorption spectroscopy (AS) and emission spectroscopy (ES) from delocalized probe plasma are implemented in the downstream chamber of a soft-etch industrial plasma reactor. A capacitively coupled plasma plasma, running in the upper compartment in He/NF₃/NH₃/H₂ mixtures at about 1 Torr, produces reactive species which flow through a shower head into a downstream chamber, where they can etch different μ-electronic materials: Si, SiO₂, SiN, etc. The ES reveals the presence of F atoms, while the dissociation rates of NF₃ and NH₃ are deduced from the AS, as well as the density of HF molecules, produced by chemical chain-reactions between dissociation products of NF₃, NH₃, and H₂. The variations of HF density as a function of the NH₃ flow rate suggest the possible formation of NH₄F molecules in the plasma.