Design and Synthesis of New Alicyclic Acrylate Polymer with Androstane Moiety for 193nm Resist

• Published in: Journal of Photopolymer Science and Technology 1999, Vol.12(3), pp.477-486
• Main Authors: Aoai, Toshiaki, Sato, Kenichiro, Kodama, Kunihiko, Kawabe, Yasumasa, Nakao, Hajime, Yagihara, Morio
• Format: Article
• Language: English
• Subjects: adhesion to substrate; alicyclic acrylate polymer; androstane; deozycholic acid; dry-etching resistance
• ISSN: 0914-9244; 1349-6336
• DOI: 10.2494/photopolymer.12.477

Syntheses of new alicyclic (meth)acrylate polymers containing androstane moieties, especially cholic acid derivatives, and their characteristics were investigated for 193nm single layer resist. Among the derivatives, a deoxycholic acid structure was selected from the viewpoints of its ability for dry-etching resistance, adhesion on a substrate, and solubility for resist solvents. A work of adhesion, Ohnishi and ring parameters were used as measures for the adhesion and the dry-etching resistance in this study. In the syntheses of the polymers, the use of 3-β-methacryloyloxy-deoxycholic acid, which is the inverse configuration against the original 3-α-structure, was effective as a monomer, because the steric hindrance at 3-α-position degraded its polymerization ability. The polymers partially protected by acid labile groups showed a satisfactory adhesion, which was probably due to the hydrophilic hydroxyl group at the 12-position and the carboxyl group linked at the 17-position, and a good dry-etching resistance. On the lithographic imaging with these polymers, the reduction of the side reaction on the acid decomposition and also the control of the flexibility on the polymers largely affected their performance. The adjustment of the Tg values of the polymers by the co-polymerization and the change of the polymer backbone from the methacrylate to acrylate structure performed well on imaging under 193nm exposure.