The aim of this study is to characterize the SiO₂ etching process developed in a magnetic triode experimental system fed by C₂F₆. The effect of some experimental parameter variation, namely of pressure, C₂F₆ flow, magnetic field intensity, upper electrode power (40 MHz), lower electrode power (13.56 MHz) on the SiO₂ etch rate has been studied and related to the absolute value of the self-induced voltage of the lower substrate electrode. The gas phase has been investigated by means of actinometric optical emission spectroscopy. Good correlation has been found between the gas density trends of CF₂ radicals and F atoms and the behaviour of etch rate, showing a significant dependence of the SiO₂ etching rate on both ion energy and F:CF₂ density ratio.