Efficient removers for poly(methylmethacrylate)

As nanotechnology approaches molecular scales, issues of surface contamination by unremoved resists will play an important role in device fabrication. Electron beam lithography of polymethylmethacrylate (PMMA) resist is still among the most widely used nanofabrication techniques, so it is relevant to study its residual contamination on both exposed and unexposed surfaces using a variety of resist removers. We systematically characterized the effectiveness of several different strippers. Our experiments show that 1,2-dichloroethane is an efficient PMMA remover, and can produce almost the same surface roughness as the original ${\mathrm{SiO}}_2$ surface (i.e., no contamination), whereas the popular PMMA remover, acetone, cannot. Estimates of the polymer–solvent Flory–Huggins interaction parameters and surface–solvent interfacial energy (from contact angle measurements) satisfactorily predict the effectiveness of the solvents. This method should also be applicable to any PMMA-like films on any substrate to find a good surface cleaner.