Cross-section set and chemistry model for the simulation of c-C4F8 plasma discharges

Great interest exists in c-C4F8 (octafluorocyclobutane or perfluorocyclobutane) etching plasma discharges due to their selectivity and potential for decreasing global warming gas emissions. In order to allow computational exploration of the discharge physics, a numerical model for a c-C4F8 discharge has been constructed. A set of cross sections has been assembled for electron collisions with c-C4F8 based on a combination of ab initio calculations, beam measurements, and swarm (i.e., electron transport coefficient) analysis. In addition, a chemical reaction set has been proposed and an axisymmetric numerical model has been used to test the cross section and chemical reaction set against experiments. Results show that measured trends are reproduced and absolute values are well represented. A mechanism is suggested for negative atomic fluorine ion (F−) behavior with respect to power.