Comparison of etching characteristics of SiO_2 with ArF photoresist in C_4F_6 and C_4F_8 based dual-frequency superimposed capacitively coupled plasmas

摘要

In this study, we compared the C_4F_6 and C_4F_8 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)), O_2 flow, and CH_2F_2 flow rate in the C_4F_8/ CH_2F_2/O_2/Ar and C_4F_6/CH_2F_2/O_2/Ar plasmas. The silicon oxide etch rates increased significantly in both chemistries with increasing f_(HF) and O_2 flow rate. The silicon oxide etch rates were higher in the C_4F_8/CH_2F_2/O_2/Ar than in the C_4F_6/CH_2F_2/O_2/Ar plasmas, but the PR etch rate was much higher in the C_4F_6/CH_2F_2/O_2/Ar than in the C_4F_8/CH_2F_2/O_2/Ar plasmas under the present experimental conditions. The slower oxide etch rate in the C_4F_6 based plasmas was attributed to the thicker steady-state fluorocarbon layer on the silicon oxide surface, while the faster PR etch rate in the C_4F_8 based plasmas was ascribed to the higher F radical density in the plasma.