Novel multi-alicyclic polymers for enhancing plasma etch resistance in 193 nm lithography

Fully multi-alicylic polymers designed for use as 193 nm photoresist materials have been synthesized by vinyl addition polymerization of tetracarbocyclic norbornene derivatives, t-butyl tetracyclo[4.4.0.1.2,5 17,10]dodec-8-ene-3-carboxylate (t-BDN) and 3-acetoxytetracyclo-[4.4.0.1.2,5 17,10]dodec-8-ene (AcODN). The alicyclic polymer backbones of these polymers provide plasma etch resistance and mechanical properties. Two pendant groups were introduced to provide the desired lithographic functions: the t-butyl carboxylate group as a carboxylic acid functionality masked by a protecting group undergoes acid-catalyzed thermolysis; and the acetoxy polar group influences adhesion, wettability and dissolution properties of the polymers. The polymer showed an acceptable high transmittance at 193 nm and good adhesion property. The plasma etch rates of the copolymer poly(t-BDN-co-AcODN) (85:15) using CF4/CHF3 mixed gas were 1.01 times with respect to a novolac based resist. The 0.2 μm line-and-space patterns were obtained with a dose of 45 mJ cm−2 using a KrF excimer laser stepper.