Elementary Chemical Reactions on the SiO2 Surface in Fluorocarbon Plasma

Using DFT and DPLNO-CCSD(T) quantum chemistry methods, thresholds for elementary reactions occurring during atomic-layer etching of SiO2 in fluorocarbon plasma, as well as binding energies of key structures and adsorption energies of CF2 and F on the SiO2 surface were calculated. Calculations were made for two proposed etching mechanisms: at the SiO2/CxFy interface layer and through the formation of free F atoms in the fluorocarbon film. Calculations show that in the first case, the reaction is limited by the removal of reaction products, and in the second case, by the cleavage of C–F bonds in the fluorocarbon film under ion bombardment. In practice, the joint implementation of both mechanisms is possible. The diffusion of fluorine atoms across the CxFy film does not limit the process.