Ultrahigh Selective Etching of SiO[sub 2] Using an Amorphous Carbon Mask in Dual-Frequency Capacitively Coupled C[sub 4]F[sub 8]/CH[sub 2]F[sub 2]/O[sub 2]/Ar Plasmas

Highly selective etching of a silicon dioxide layer using a very thin physical-vapor-deposited amorphous carbon layer (PVD-ACL) was investigated in a dual-frequency superimposed capacitively coupled plasma etcher. The following process parameters of the /Ar plasmas were manipulated: flow ratio, high frequency (HF) power , and low frequency power . A wide processing window existed to produce the ultrahigh etch selectivities of a layer using the patterned PVD-ACL mask. The etch gas flow ratio played a critical role in determining the process window for ultrahigh silicon oxide/ ACL etch selectivity due to the disproportionate change in the degree of polymerization on the and ACL surfaces. Etching of the ArF photoresist/bottom antireflective coating (BARC)/ /ACL/silicon-oxide-stacked structure allows the use of a very thin PVD-ACL as an etch mask layer for the etching of high aspect ratio silicon dioxide patterns.