Thermal acid generator, resist undercoat material and patterning process

摘要

A thermal acid generator of generating an acid on heating above 100° C. has formula: CF₃CH(OCOR)CF₂SO₃^-(R¹)₄N⁺ wherein R is alkyl or aryl, R¹ is hydrogen, alkyl, alkenyl, oxoalkyl, aryl, aralkyl or aryloxoalkyl, or R¹ may bond together to form a ring with N. The sulfonic acid generated possesses an ester site within molecule so that less bulky acyl groups to bulky groups may be incorporated therein. The thermal acid generator provides a sufficient acid strength, is less volatile due to a high molecular weight, and ensures film formation. Upon disposal of used resist liquid, it may be converted into low accumulative compounds.