Polyhedral oligomeric silsesquioxane (POSS) based resists: Material design challenges and lithographic evaluation at 157 nm

In this paper we describe the lithographic behavior and related material properties of a new class of chemically amplified, positive tone, silicon-containing methacrylate photoresists incorporating the polyhedral oligomeric silsesquioxane (POSS) group as the etch-resistant component. POSS-bearing monomers were copolymerized with methacrylic acid (MA), tertbutyl methacrylate (TBMA), tert-butyl trifluoro methacrylate (TBTFMA), itaconic anhydride (IA), and 2-(trifluoromethyl) acrylic acid (TFMA), in various compositions. A perfluorooctylsulfonate-based photoacid generator (PAG) was used to deprotect TBMA (or TBTFMA) to base soluble carboxylic acid by heating after exposure. XPS and angular XPS analysis were used to examine possible surface segregation phenomena. It was proven that POSS surface enrichment occurs for the POSS-TBMA copolymers while surface segregation may be reduced if suitable additional resist components are selected. The POSS-based resists were studied for 157-nm lithographic applications and found to have high sensitivity (<10 mJ/cm(2) under open field exposure), no silicon outgassing, and sub-100-nm resolution capabilities. Ninety nanometer patterns in 100-nm thick films were resolved. At present, their absorbance is high (similar to4 mum(-1)) for single-layer lithographic applications at 157 nm; however, high etch resistance in oxygen plasma makes them suitable for bilayer schemes.