Investigation of reduction in etch rate of isolated holes in SiOCH

The reduction in the etch rate of isolated holes in SiOCH was investigated as functions of deposition condition of SiOCH, cap-layer presence, air-exposure time between lithography and etching, and degassing time between cap-layer etching and SiOCH etching. The amount of H2O in the films was evaluated using thermal-desorption spectroscopy (TDS). We conclude that the H2O adsorbed in SiOCH reduces the etch rate, and its degassing results in recovery of etch-rate reduction. Using the SiOCH film that can avoid the damage due to cap-layer deposition, the reduction in etch rate was restricted during two months of air exposure.