Structural changes in poly(methyl methacrylate) during deep-etch X-ray synchrotron radiation lithography .3. Mode of action of the developer

The structural changes in poly(methyl methacrylate) (PMMA) caused by radiochemical reactions are predominantly governed by a decrease in molar mass and a splitting of side chains. It can be shown that the removal of the irradiated parts of PMMA is not a pure physical dissolving, but that there is a chemical reaction proceeding, the products of which are well soluble in polar solvents. This special type of reaction restricts this process on the irradiated areas and hence explains the high selectivity of the developing of the lithographic structures. Knowledge of these mechanisms leads to the prediction that isotactic PMMA shows an increased selectivity of the developing agent. Further improvements and optimizations of etching and developing an therefore possible.