Study of dry etching resistance of methacrylate polymers for ArF excimer laser lithography

We have investigated dry-etching resistance of methacrylate polymers for use as ArF chemically amplified resists and proposed a new etching model that can predict the etching rate very accurately. The examined polymers were methacrylate polymers with alicyclic groups. The polymers were dry etched using a LAM TCP-9400 machine under the chlorine-based gas conditions used for poly-silicon etching. The obtained etching rate was explained in term of a carbon-atom-density parameter known as the ohnishi parameter. However, the fitting accuracy is not good enough especially for alicyclic polymers (R=0.87). And a ring parameter model also resulted in a similar fitting accuracy (R=0.86). Hence, we proposed a new model that introduced polymer-structure dependence into the carbon-atom-density model. The new model gives excellent agreement with measured data (R=0.99). And it is very useful in designing ArF resist polymers and predicting etching resistance of future ArF resists.