POLYMERIC SULFONIUM SALTS AS ACID GENERATORS FOR EXCIMER-LASER LITHOGRAPHY

New polymers having sulfonium salt units in the main chain have been synthesized. Their photoactivity for excimer lasers (KrF, ArF) and their thermal stabilities have been elucidated. Phenyl-type polymeric sulfonium salts exhibit good thermal stability (dec. 274-304 degrees C). The photo-acid generating efficiency of the phenyl-type polymeric sulfonium salts for the ArF excimer laser (193.4 nm) increases with an increase in x. A phenyl-type polymeric sulfonium salt with x=0.478 exhibits 2.5 times the photoactivity for triphenylsulfonium trifluoromethanesulfonate (TPS) and lower absorption property than TPS, These results suggest that inner-filter effects for phenylene sulfide groups and electron donating properties for neighboring phenylthio groups control the photoactivity for polymers.