Model prediction of radical composition in plasmas and correlation with measured etch characteristics of silicon dioxide

A computational model for plasma chemical reactions has been developed. An ab initio molecular orbital method was used to determine dissociation paths and their threshold energies. Plasma characteristics were calculated by a plasma kinetic method. The radical compositions in , with additional gases such as Ar, He and , were calculated. Radicals influencing the selective etching of over were analysed. With increased microwave power or decreased flow rate, density decreased and CF, C and F densities increased. The increase of radicals with abundant carbon relative to fluorine would result in high etch selectivity of over and a low etch rate. Increases in the concentration of F radicals are correlated with increases in etch rates. Electron temperature was high with He addition, and dropped with alone and Ar addition discharges. On the contrary, the electron density was high in the reverse order. The highest etch selectivity was obtained with He addition. A high electron temperature discharge would be one solution to obtain high etch selectivity of over .