An aqueous‐base developable photoresist based on light‐induced cationic polymerization: Resist performance of poly(glycidyl methacrylate‐co‐methacrylic acid)

Abstract

AbstractAn aqueous‐base developable photoresist based on photoinduced cationic polymerization has been prepared by copolymerization of glycidyl methacrylate (GMA) and methacrylic acid (MAA). The copolymer containing 83 mol% of GMA unit is soluble in an aqueous base and crosslinked in the presence of photogenerated acid caused by acid‐initiated ring‐opening polymerization of pendant epoxide groups. Exposure results in the generation of acid and the subsequent baking process promotes the diffusion of photogenerated acid, which initiates the cationic crosslinking of the epoxide rings. It was also found that the sensitivity of the copolymer was remarkably enhanced when a divinyl ether monomer is added as a bifunctional crosslinker. The sensitivity enhancement may be caused by the high reactivity of the divinyl ether monomer in the presence of acid. The resist comprised of the copolymer, the vinyl ether monomer, and diphenyliodonium 9,10‐dimethoxy‐an‐thracene‐2‐sulfonate as photoacid generator exhibited the sensitivity of 20 mJ/cm2. A good pattern profile with high resolution was attained by exposure to a 365 nm light followed by a postexposure bake at 60°C for 3 min. © 1993 John Wiley & Sons, Inc.