Improvement in etch selectivity of SiO_2 to CVD amorphous carbon mask in dual-frequency capacitively coupled C_4F_8/CH_2F_2/O_2/Ar plasmas

摘要

Highly selective etching of a SiO_2 layer using a chemical vapor deposited (CVD) amorphous carbon (a-C) mask pattern was investigated in a dual-frequency superimposed capacitively coupled plasma etcher. The following process parameters of the C_4F_8/CH_2F_2/O_2/Ar plasmas were varied: the CH_2F_2/(CH_2F_2 + O_2) flow ratio (Q(CH_2F_2)), the high frequency power (Phf). and the low frequency power (P_(LF)). It was found a process window exists to obtain infinitely high etch selectivity of the SiO_2 layer to the CVD a-C. The process parameters of Q(CH_2F_2), P_(HF). and P_(LF) played critical roles in determining the process window for oxide/CVD a-C etch selectivity, presumably due to the disproportionate degree of polymerization on the SiO_2 and CVD a-C surfaces.