Synthesis of novel fluoropolymers for 157-nm photoresists by cyclopolymerization

Abstract

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 have excellent transparency lower than 1.0 &#956;m^-1 at 157nm wave length. The number-average molecular weight (Mn) of the polymers is 4000 to 20000, the glass transition temperature (Tg) is 130 to 155 &deg;C and the decomposition temperature (Td) is about 400 &deg;C. Copolymerization reaction with the other monomers (ex. fluoroolefins,(meth)acrylates and vinyl esters) were also examined. The introduction of protecting group (ex. methoxylmethly, 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 &#956;m^-1, good solubility in the standard alkaline solution (0.26N N-tetramethylammonium hydroxide aqueous solution) and relatively high sensitivities below than 10mJ/cm<SUP>2</SUP>. 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.