Etching characteristics and application of physical-vapor-deposited amorphous carbon for multilevel resist

Abstract

For the fabrication of a multilevel resist (MLR) based on a very thin, physical-vapor-deposited (PVD) amorphous carbon (a-C) layer, the etching characteristics of the PVD a-C layer with a SiOx hard mask were investigated in a dual-frequency superimposed capacitively coupled plasma etcher by varying the following process parameters in O-2/N-2/Ar plasmas: high-frequency/low-frequency combination (f(HF)/f(LF)), HF/LF power ratio (P-HF/P-LF), and O-2 and N-2 flow rates. The very thin nature of the a-C layer helps to keep the aspect ratio of the etched features low. The etch rate of the PVD a-C layer increased with decreasing fHF/fLF combination and increasing P-LF and was initially increased but then decreased with increasing N2 flow rate in O-2/N-2/Ar plasmas. The application of a 30 nm PVD a-C layer in the MLR structure of ArF PR/BARC/SiOx/PVD a-C/TEOS oxide supported the possibility of using a very thin PVD a-C layer as an etch-mask layer for the TEOS-oxide layer. (C) 2008 American Vacuum Society.