Thermal and Acid-Catalyzed Deesterification and Rearrangement of Poly(2-cyclopropyl-2-propyl 4-vinylbenzoate) and Their Application to Lithographic Imaging

Poly(2-cyclopropyl-2-propyl 4-vinylbenzoate) releases 2-cyclopropylpropene at about 160 °C. Although the thermal deprotection temperature is about 80 and 30 °C lower than that of the corresponding fert-butyl ester and poly(4-(tert-butoxycarbonyloxy)styrene), respectively, a minor concomitant rearrangement to the 4-methyl-3-pentenyl ester occurs in the case of the cyclopropyl carbinol ester (about 10%). The temperature of deprotection that converts the ester polymer to poly(4-vinylbenzoic acid) can be lowered by photochemically generating a strong acid in the solid state. However, the acid-catalyzed thermolysis favors rearrangement (about 66%) over deprotection. The thermal and acid-catalyzed deesterification and rearrangement can be exploited in the design of new resist materials that are developed in a negative mode either with nonpolar organic solvents or with aqueous base, depending on the postexposure bake temperature. Cross-linking through the 4-methyl-3-pentenyl group is also discussed. © 1990, American Chemical Society. All rights reserved.