Functionalized polymers for high-resolution photolithography

Polymers obtained by radical polymerization of maleic anhydride with different monomers are used in bilayer photoresists for the CARL (Chemical Amplification of Resist Lines) process. Aqueous-based silylation of resist patterns with bisaminopropyl-oligodimethylsiloxane enhances oxygen–plasma etch resistance and creates widened structures. Thus, the resolution capability of optical exposure tools can be used to the full extent and even structures beyond the optical resolution limit become accessible. Copolymerization of maleic anhydride with tBOC-maleimide or methacrylic acid t-butylester yields polymers for highly sensitive acid-catalyzed deep UV resists. With the use of a KrF excimer-laser stepper 0.25 μm structures are resolved.