Comparison of etching characteristics of SiO₂ with ArF photoresist in C₄F₆ and C₄F₈ based dual-frequency superimposed capacitively coupled plasmas

In this study, we compared the C₄F₆ and C₄F₈ based plasma etching characteristics of silicon dioxide and ArF photoresist (PR) in a dual-frequency superimposed capacitively coupled plasma (DFS-CCP) etcher under different high- and low-frequency combinations (f_HF/f_LF), while varying the process parameters such as the dc self-bias voltage (V_dc), O₂ flow, and CH₂F₂ flow rate in the C₄F₈/CH₂F₂/O₂/Ar and C₄F₆/CH₂F₂/O₂/Ar plasmas. The silicon oxide etch rates increased significantly in both chemistries with increasing f_HF and O₂ flow rate. The silicon oxide etch rates were higher in the C₄F₈/CH₂F₂/O₂/Ar than in the C₄F₆/CH₂F₂/O₂/Ar plasmas, but the PR etch rate was much higher in the C₄F₆/CH₂F₂/O₂/Ar than in the C₄F₈/CH₂F₂/O₂/Ar plasmas under the present experimental conditions. The slower oxide etch rate in the C₄F₆ based plasmas was attributed to the thicker steady-state fluorocarbon layer on the silicon oxide surface, while the faster PR etch rate in the C₄F₈ based plasmas was ascribed to the higher F radical density in the plasma.