Polymers from aryl cyclic sulfonium zwitterions-photosensitive materials cast from and developed in water

Upon photolysis or heating, aryl cyclic sulfonium (ACS) zwitterions polymer ize by ring-opening and loss of charge to yield nonionic polymers. These wa ter-soluble monomers potentially are useful for photolithography because th ey can be cast from and developed in water. The ACS zwitterion from bisphen ol A, 1,1'-[isopropylidenebis(6-hydroxy-3,1-phenylene)] bis (tetrahydrothio phenium hydroxide) bis(inner salt) (1) is a negative-tone, photosensitive m aterial that after photolysis yields a crosslinked film. Unexposed regions are removed by water. The cured film has a low dielectric constant, high vo lume resistivity, a high degree of planarization, low residual stress, ther mogravimetric stability, acceptable fracture toughness, and high hardness. These are desirable properties for a dielectric material used in microelect ronic applications. However, a shortcoming of the material is its low T-g, at about 140 degrees C. A second ACS zwitterion, 1,1'-[fluorenylidenebis(6- hydroxy-3,1-phenylene)] bis(tetrahydrothiophenium hydroxide) bis(inner salt ) (2) was prepared that yields a crosslinked polymer with a higher T-g of a bout 190 degrees C. (C) 2000 John Wiley & Sons, Inc.