Photogenerated Base in Polymer Imaging. Synthesis and Photopatterning of Poly(2-cyano-2-(p-vinylphenyl) Butanoic Acid)

Since the concept of chemical amplification was first introduced by us more that twelve years ago, a number of new resists based on acid-catalyzed thermolysis have been developed and commercialized. This report describes the first chemically amplified resist operating through photogenerated base. The concept is demonstrated with poly(2-cyano-2-(p-vinylphenyl)butanoic acid) which decarboxylates readily under basic conditions. A resist system consisting of this polymer and an amine photogenerator bis(2,6-dinitrobenzyloxy)carbonylhexan- 1,6-diamine has been formulated and tested in microlithography. The sensitivity of this resist is extremely high (1.4 mj/sq cm) with a very high contrast of 13. 7. This very high sensitivity confirms that chemical amplification is achieved as the photogenerated base is not consumed in the overall decarboxylation process. The mechanistic insights gained from the study of the decarboxylation process may be used in the designed of other resists involving more readily accessible polymers.