Photochemical acid generation from copolymers based on camphorsulfonyloxymaleimide and acidolytic deprotection

Abstract

A new sulfonyloxymaleimide monomer, N-(10-camphorsulfonyloxy)maleimide (CSOMI), has been synthesized and copolymerized with styrene derivatives (XSt) to make photoacid-generating polymers P(CSOMI/XSt). The amount of photochemically generated 10-camphorsulfonic acid (CSA) from the polymer films was determined in percent conversion of CSOMI units by colorimetry using tetrabromophenol blue as an acid indicator. The capability of photochemical generation of the bulky CSA was enhanced either by adding hydroquinone as a hydrogen donor or by incorporation of p-hydroxystyrene (HOSt) into the polymer chains as a XSt. Upon exposure to 250-nm light with 300 mJ cm(-2) the film of the phenolic copolymer P(CSOMI/HOSt) was found to undergo 19% conversion of CSOMI units and it further increased to 23% conversion when 5 wt% hydroquinone was included in the film. The thermal and photoacidolytic deprotection of the tert-butoxycarbonyl (t-BOC) protected copolymers having CSOMI units was investigated in detail. The complete deprotection of side-chain t-BOC groups was accomplished by the photogenerated CSA, thereby providing a significant change in solubility of the polymers. Thus the applicability of the polymers as a single-component photoresist was verified. (C) 1999 Elsevier Science B.V. All rights reserved.