Chemical reaction dynamics of SiO₂ etching by CF₂ radicals: Tight-binding quantum chemical molecular dynamics simulations

The plasma etching of SiO₂ by CF₂ radicals was investigated using a newly developed etching process simulator based on tight-binding quantum chemical molecular dynamics (TB-QCMD). CF₂ radicals were continuously irradiated on the SiO₂(001) surface and then the dissociations of the C-F and Si-O bonds were observed. We also observed the generation of CO and CO₂ molecules and Si-F bonds, which is in good agreement with previous experiments. The formation of etching holes was realized after the continuous irradiation of CF₂ radicals. Furthermore, the effect of radical velocity on etching efficiency was also examined. The ratio of penetration depth to the width of irradiated atoms was examined for the evaluation of etching efficiency. The ratio increases as the irradiation velocity of CF₂ radicals increases. Our TB-QCMD etching process simulator is capable of predicting etching rate and aspect ratio depending on the velocity of irradiated radicals.