Synthesis and polymerization of 3-(t-butoxycarbonyl)-1-vinylcaprolactam and application as deep UV resists

Poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam) (PBCVC) was synthesized and evaluated as a potential deep UV photoresist. The synthesized polymer has excellent transmittance at 248 nm (absorbance = 0.018 mu m(-1)). In addition, PBCVC possesses good thermal stability up to 220 degrees C and a high glass transition temperature (174 similar to 190 degrees C). The thermal deprotection of side chain ester groups of PBCVC occurs at 220 degrees C, whereas in the presence of acid the cleavage of the t-butyl ester groups of PBCVC begins at about 80 degrees C, and followed by evolution of carbon dioxide at about 150 degrees C. Deprotection of PBCVC gave the corresponding polymer, poly(1-vinylcaprolactam-3-carboxylic acid). The contrast of the PBCVC resist system was not deteriorated with the post-exposure delay (PED) time.