Poly (phenyl methacrylate-co-methacrylic acid) as a dry-etching durable positive electron resist

Copolymers of phenyl methacrylate and methacrylic acid (φ-MAC) have been investigated as dry-etching durable positive electron resists. φ-MAC´s are preheated above 170°C to crosslink the polymers by intermolecular acid anhydride bonds. The crosslinked φ-MAC´s become insoluble and do not swell even in development with strong solvents. They also have excellent thermal stability. These properties contribute to their high sensitivity of 5 µC/cm², γ(contrast) = 2.0, and resolution finer than 0.2-µm line patterns (65 µC/cm²). φ-MAC´s have excellent dry-etching durabilities (e.g., 2 times stronger than PMMA in reactive sputter etching) and good adhesion to the substrate due to the protective effect of benzene rings and the adherent effect of carboxylic acid groups, respectively. The good properties of φ-MAC´s make them prospective in the submicrometer electron lithography.