Effect of Low-frequency Power on F, CF2 Relative Density and F/CF2 Ratio in Fluorocarbon Dual-Frequency Plasmas

Effect of low-frequency power on F, CF₂ relative density and F/CF₂ ratio, in C₂F₆, C₄F₈ and CHF₃ dual-frequency capacitively couple discharge driven by the power of 13.56 MHz/2 MHz, was investigated by using optical emission spectroscopy. High F, CF₂ relative density and high F/CF₂ ratio were obtained in a CHF₃ plasma. But for C2F6 and C4F8 plasmas, the F, CF₂ relative density and F/CF₂ ratio all decreased significantly due to the difference in both reactive paths and reactive energy. The increase of LF power caused simultaneous increase of F and CF₂ radical relative densities in C₄F₈ and CHF₃ plasmas, but led to increase of F with the decrease in CF₂ relative densities in C₂F₆ plasma due to the increase of lower energy electrons and the decrease of higher energy electrons in EEDF.