On the attainment of optimum developer parameters for PMMA resist

Because of the uniquely high resolution offered by poly(methyl methacrylate) (PMMA) for practically all forms of lithography, its technological significance remains strong. We have found significantly higher contrast developers for PMMA which have shown improved resolution, less susceptibility to proximity effects and better lift-off properties with no loss of sensitivity to exposure. We report data which demonstrate an improvement in contrast by more than 35% with the addition of as little as 1.3% methyl ethyl ketone (mek) to other common developers. We discuss a model which explains the observed contrast enhancement and predicts that for small changes, an increase in either mek concentration, temperature or develop time increases contrast. We include experimental evidence in support of temperature and mek related improvements.