Enhanced Block Copolymer Lithography Using Sequential Infiltration Synthesis

Block copolymer lithography is a promising approach to massively parallel, high-resolution, and low-cost patterning, but the inherently low etch resistance of polymers has limited its applicability to date. In this work, this challenge is overcome by dramatically increasing the plasma etch contrast of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) using spatially localized sequential infiltration synthesis (SIS) of alumina. The PMMA phase of self-assembled PS-b-PMMA block copolymer thin films was selectively infiltrated with alumina yielding an inorganic nanostructure mimicking the original block copolymer template that serves directly as a robust etch mask. SIS-modified films are resistant to a variety of plasma etching chemistries enabling the direct patterning of a range of substrates, including silicon, indium tin oxide, and permalloy, without the need for intermediate hard mask layers. This method considerably simplifies the fabrication of nanostructures in technologically relevant materials over large areas with improved transfer fidelity and pushes block copolymer lithography closer to practical use.