Synthesis and characterization of radiation-sensitive polymers and their application in lithography

The goal of this dissertation is to synthesize and characterize novel polymers designated as resists for lithographic applications. Although significant progress has been achieved in the design and preparation of new resists over the past decades, much remains to be accomplished. The focus of this research is to address some critical issues frequently encountered in designing new resists: (i) dry-etch resistance. A resist material must have sufficient dry-etch resistance for pattern transfer. Polyhedral oligosilsesquioxane methacrylate (POSS) is a structurally well-defined monomer that has an inorganic silica-like pendant group. In this work, a series of POSS-containing polymeric resists were synthesized and characterized. The results have shown that incorporation of POSS into the polymers increased their dry-etch resistance without sacrificing the sensitivity. A morphological study of the polymer films by high-resolution TEM was conducted in an effort to shed some light on how the silica cages assemble in the resist film; (ii) compatibility of polymer matrices and photoacid generators in chemically amplified resists. Chemically amplified resists, formulated by physically blending a polymer and a photoacid generator, can pose problems such as phase separation and nonuniform PAG distribution in the resist film. To circumvent these problems, a photoacid generating monomer was synthesized. A series of novel resists were prepared by copolymerization of this monomer with various comonomers. These resists offer a number of advantages over physically blended resists, such as excellent film formation behavior and high sensitivity. In contrast with the polymer/PAG blends, these resists had high acid generating efficiency independent of components and compositions of the polymers. In addition, the homopolymer of this monomer acted as a high sensitivity negative resist that did not suffer solvent-induced swelling phenomenon due to its single-component character.