Synthesis of novel fluoropolymer for 157nm photoresists by cyclo-polymerization

Novel fluoropolymers having partially fluorinated monocyclic( 5-membered and 6-membered ring) structure have been synthesized with radical cyclo-polymerization, which have C-F bond in the polymer main chain and also possess fluorocontaining acidic alcohol group. These polymers has excellent transparency lower than 1.0 mu m(-1) at 157 nm wave length. The number-average molecular weight (Mn) of the polymers is 4000 to 20000,the glass transition temperature (Tg) is 130 to 155 degreesC and the decomposition temperature (Td) is about 400degreesC. Copolymerization reaction with the other monomers (ex. fluoroolefins,(meth)acrylates and vinyl esters) were also examined. The introduction of protecting group (ex. methoxymethyl, and t-butoxycarbonyl group) to alcohol units of the polymer can be applied before or after polymerization reaction. We also evaluated fundamental resist performances. These have excellent transparency of 0.5 to 1.5 mu m(-1), good solubility in the standard alkaline solution(0.26N N-tetramethylammmonium hydroxide aqueous solution) and relatively high sensitivities below than 10mJ/cm(2). The imaging results of the above fluoropolymer based positive-working resists are presented. Under 100-nm line and space pattern are delineated in 200-nm thick film by using the phase shift mask.