Structural Analysis of Ionic Photobase Generators and Lithographic Patterning of Polysilane Films Containing the Photobase Generators

Abstract

Photobase generator is recently attracting more attention because it is freed from oxygen inhibition and metal corrosion, compared to photoacid generator and photo radical generator. 2-(9-Oxoxanthen-2-yl)propionic acid (OXTA) has an absorption in the range of i-line wavelength and it can form a salt with phosphazene base (P₂tBu). It is photobase generator (PBG) to generate an organic superbase efficiently by UV irradiation. In this study, we synthesized a series of salts of OXTA and P₂tBu (OXTA-P₂tBu) at several anion-cation ratio. Then, we analyzed the PBG with each ratio by pH, UV absorption and ESR, and calculated OXTA-P₂tBu complex by (TD)B3LYP/6-31+G(d,p) level. The crystal of OXTA-P₂tBu synthesized at optimum ratio was analyzed by single crystal X-ray diffraction and we described the crystal structure. Furthermore, we obtained nega-type pattern with polysilane solution containing OXTA-P₂tBu in the optimum ratio.