Electron impact ionization cross-sections of carbon-fluorine environmental gases for photolithography

Abstract Fluorocarbon working gases have been extensively utilized in “dry” patterning techniques during photolithography in recent years. The ionization cross-sections of these gases are essential for simulating plasma processes in commonly used in plasma modeling software, such as COMSOL Multiphysics, ANSYS Fluent and BOLSIG+. While the electron impact ionization (EII) of CxFy molecules has been widely studied, there is still limited data on the EII cross-sections for CxFy molecules containing oxygen and nitrogen atoms. Using density functional theory, we adopted the Binary-Encounter-Bethe (BEB) method to calculate the EII cross-sections of seven CxFy molecules with oxygen and nitrogen atoms, resulting in a total of 21 molecules analyzed. We examined the effect of the electron propagator theory (EPT) correction on the EII cross-sections of these 21 fluorocarbon compounds. Our findings indicate that utilizing the Hartree-Fock wavefunction to calculate the molecular orbital binding energies, and substituting the first orbital binding energy with the ionization energy derived from a complete basis set, yields BEB cross-sections that align closely with experimental data, even without the EPT correction. We present a portion of the EII cross-sections for these CxFy molecules containing oxygen and nitrogen atoms. The discrepancies at the peak of the two BEB cross-sections for molecules with oxygen and nitrogen atoms remained within 5.8%.