Passivation Effect during the C4F8 + N2 Etch Process for SiOCH Low-k Films

Plasma-induced damage to low-k dielectric layers is a key issue in developing multi-level interconnection technology based on copper and low-k dielectrics. Changes in the chemical composition of the dielectric films after plasma processes often increase the dielectric constants of low-k materials. In this work, SiOCH low-k dielectric films were studied and etched by using a C₄F8+N₂ plasma for patterning. Nitrided fluorocarbon polymer films were observed after C₄F8+N₂ plasma etching. X-ray photoelectron spectroscopy was used to monitor the chemical bonding changes of the polymer films in terms of N₂ content in the C₄F8+N₂ mixture. With 40 \% N₂ in the mixture, the etch condition was optimized for high etch rate and selectivity. After photoresist stripping by using a N₂ plasma and removal of nitrided fluorocarbon polymer by HF dipping, the SiOCH layer had recovered its original dielectric constant of 2.80 without any pattern size change. KCI Citation Count: 8