C₂F₆/O₂/Ar Plasma Chemistry of 60MHz/2MHz Dual- frequency Discharge and Its Effect on Etching of SiCOH Low-k Films

This work investigated C₂F₆/O₂/Ar plasma chemistry and its effect on the etching characteristics of SiCOH low-k dielectrics in 60MHz/2MHz dual-frequency capacitively coupled discharge. For the C2F6/Ar plasma, the increase in the LF power led to an increased ion impact, prompting the dissociation of C₂F₆ with higher reaction energy. As a result, fluorocarbon radicals with a high F/C ratio decreased. The increase in the discharge pressure led to a decrease in the electron temperature, resulting in the decrease of C₂F₆ dissociation. For the C2F6/O2/Ar plasma, the increase in the LF power prompted the reaction between O₂ and C₂F₆, resulting in the elimination of CF₃ and CF₂ radicals, and the production of an F-rich plasma environment. The F-rich plasma improved the etching characteristics of SiCOH low-k films, leading to a high etching rate and a smooth etched surface.