The H-2 plasma treatment for spin-on carbon (SOC) hard mask in the trilayer resist process is expected to serve as a reliable alternative to single layer resist process for 45 nm nodes and beyond. The authors have investigated this treatment with a view to suppress the deformation of SOC by oxide etching. The wiggling profile of SOC drastically improves due to the formation of a thicker diamondlike amorphous carbon structure by the H-2 plasma treatment with higher-energy hydrogen ions. (C) 2008 American Vacuum Society.