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 (fHF/fLF), while varying the process parameters such as the dc self-bias voltage (Vdc), 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 fHF 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.