Using sub-resolution openings to aid in image reversal, directed self-assembly, and selective deposition

A method for treating a microelectronic substrate to form a chemical template includes patterning the substrate to form a trench structure with a plurality of trenches of a defined trench width and depositing a photoactive material on the substrate to overfill the trench structure to form a fill portion in the plurality of trenches and an overfill portion above the trench structure. The method further includes exposing the photoactive material to electromagnetic radiation comprising a wavelength that is at least four times greater than the defined trench width such that the overfill portion is modified by the exposure while the electromagnetic radiation fails to penetrate into the plurality of trenches leaving the fill portion unmodified and removing the modified overfill portion of the photoactive material to form a planarized filled trench structure for use as a chemical template for selective reactive ion etching, selective deposition, or directed self-assembly.