A chemically amplified positive-working resist system based on poly(norbornene carboxylic acid esters) is described.
a-Methylbenzyl norbornene carboxylate(MBNC) was prepared as a new protected monomer from norbornene carboxylic acid and a-methylbenzyl alcohol. This monomer MBNC was polymerized with metathesis catalyst $WC1_6$ and copolymerized with a-methylbenzyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene(MBDOC) to raise glass transition temperatures of the product copolymer up to 214℃. a-Methylbenzyl protecting group of polymers were released as styrene by heating to 297℃ regenerating polymeric carboxylic acid which was soluble in aqueous alkaline. Acidolytic deprotection of a-methylbenzyl group was also successfully carried out at 170℃ in the presence of acid. The temperature of deprotection of a methylbenzyl group was rather low 140℃. It was concluded that a phtoresist system could be formulated with the polymers of a-methylbenzyl norbornene carboxylate and photoacid generator such as triphenylsulfonium hexafluoroantimonate. Positive-tone image could be resolved by exposing the resist film in deep UV region, post baking and developing in the tetramethylammonium hydroxide solution.
