Defect-Tolerant and Directional Wet-Etch Systems for Using Monolayers as Resists

We developed strategies based on self-assembly principles to etch substrates patterned with monolayer resists with high selectivity and etch directionality. Our strategies exploit the defined composition and order of these ultrathin resists and overcome their imperfections. Defects in a monolayer can be healed by additives present in an etch bath. Alternatively, large molecules that cannot diffuse through defects can be employed as etchants. It is also possible to taper structures using the competition between etching and the side-growth of a self-assembling etch barrier, nucleating from the originally patterned monolayer. The application of these concepts lets defect-sensitive monolayers become robust and versatile resists, which should promote their acceptance and use in microtechnology.