157 nm Single-Layer and Bilayer Resists Based on #alpha#-Methylstyrene Polymers

摘要

#alpha#-Methylstyrene derivatives such as 4-tert-butoxycarbonyloxy-#alpha#-methylstyrene (BOCMST), 4-tert-butoxy-#alpha#-methylstyrene (BUOMST), 4-(hexafluoro-2-hydroxyisopropyl)-#alpha#-methylstyrene (F_6PMST),4-(hexafluoro-2-tert-butoxycarbonyloxyisopropyl)-#alpha#-methylstyrene (BOCF_6PMST) and 3,5-difluoro-4-tert-butoxycarbonyloxy-#alpha#-methylstyrene (BOCF_2MST) were newly prepared. These monomers were radically copolymerized with methacrylonitrile (MAN) using 2,2'-azobisisobutyronitrile. Ethoxyethyl,tetrahydropyranyl,and trimethylsilyl protected copolymers of MAN and 4-hydroxy-#alpha#-methylstyrene (HMST) were also prepared. The transmittance of these polymers 90.1 #mu#m thick) was 29-44% at 157nm. Dissolution properties of the polymers were studied. Trimethylsilyl protected MAN-HMST copolymer (MAN-SiMST) showed high etch resistance to oxygen plasma. Imaging was performed using MAN-SiMST as single-layer and bilayer resists.