RELIEF AND FUNCTIONAL PHOTOIMAGING WITH CHEMICALLY AMPLIFIED RESISTS BASED ON DI-TERT-BUTYL BUTENEDIOATE-CO-STYRENE

New photoimaging materials were formulated by dissolving photosensitiv e onium salts into the free-radical copolymer of di-tert-butyl trans-b utenedioate (di-tert-butyl fumarate) and styrene. Exposure to mid- or deep-UV, followed by baking, drastically altered material solubility, absorbency, and other properties, through mass cleavage of the polymer 's numerous ester groups by photogenerated strong acid catalyst (chemi cal amplification). With aqueous base or organic solvent as developer, respectively positive or negative relief images could be obtained wit h submicron resolution. The materials also showed other good qualities for their application as microlithographic resists, such as sensitivi ty (14-38 mJ/cm(2)), contrast (gamma = 4-7), transparency (0.17 mu m(- 1) at 254 nm), and thermal stability against both flow-distortion (T-g of 139 degrees C for fresh copolymer; 199 degrees C after deprotectio n) and depolymerization (>300 degrees C). The transformation of carbox ylic ester to acid or anhydride functional groups also facilitated an alternative method of development, in which various chemical species w ere selectively bound out of contacting solution to further alter the properties of photoselected areas of polymer film. Production of micro n-scale functional images, including dual-tone developability with amp hiphilic molecules, was demonstrated using fluorescent dyes.