Chemical Reaction Dynamics of SiO_2 Etching by CF_2 Radicals: Tight-Binding Quantum Chemical Molecular Dynamics Simulations

摘要

The plasma etching of SiO_2 by CF_2 radicals was investigated using a newly developed etching process simulator based on tight-binding quantum chemical molecular dynamics (TB-QCMD). CF_2 radicals were continuously irradiated on the SiO_2(001) surface and then the dissociations of the C-F and Si-O bonds were observed. We also observed the generation of CO and CO_2 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 CF_2 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 CF_2 radicals increases. Our TB-QCMD etching process simulator is capable of predicting etching rate and aspect ratio depending on the velocity of irradiated radicals.