MOLECULAR DESIGN AND SYNTHESIS OF 3-OXOCYCLOHEXYL METHACRYLATE FOR ARF AND KRF EXCIMER-LASER RESIST

We originally designed 3-oxocyclohexyl methacrylate (OCMA) for an acid-labile component in chemical amplification. The key concept of the molecular design of the 3-oxocyclohexyl substituent was the introduction of acidic protons at the alpha position of the elimination site by using a ketone functional group. OCMA was synthesized by esterification of 1,3-cyclohexanediol and methacryloyl chrloride followed by pyridinium dichromate oxidation. Using AIBN as an initiator, we also prepared Poly(OCMA-co-AdMA) (AdMA: adamantyl methacrylate) by a thermally included radical copolymerization of OCMA and AdMA. The resist comprises the copolymer and 10 wt % of triphenylsulfonium hexafluoroantimonate as a photoacid generator (PAG). This resist has high sensitivity, good thermal stability, good dry etch resistance, and good postexposure delay durability. Using a KrF excimer laser stepper (NA = 0.45) and 2-propanol mixed aqueous alkali developer, we obtained 0.3-mum line and space patterns with our resist. A resist with 1 wt % of the PAG has an acceptable transmittance at 193 nm, so we believe this resist is suitable for ArF excimer lithography.