High molecular weight block copolymer lithography for nanofabrication of hard mask and photonic nanostructures

An unusual dot pattern was realized via self-assembly of high molecular weight polystyrene-block-polydimethylsiloxane (PS-b-PDMS) copolymer by a simple one-step solvent annealing process, optimized based on Hansen solubility parameters. Annealing PS-b-PDMS under neutral solvent vapors at room temperature produces an ordered arrangement of dots with similar to 112 nm spacing and similar to 54 nm diameter. The template is highly resistant to dry etching with chlorine-based plasma, enabling its utilization on a variety of hard masks and substrates. The self-assembled PDMS dots were further exploited as a template for direct patterning of silicon, metal, and dielectric materials. This nanopatterning methodology circumvents expensive and time-consuming atomic layer deposition, wet processes, and sequential infiltration techniques. Application-wise, we show a process to fabricate nanostructured antireflection surfaces (nanocones) on a 2 in. silicon wafer, reducing the reflectance of planar silicon from 35% to below 0.5% over a broad wavelength range. Alternatively, nanocones made of TiO2 on silicon exhibit low reflectance (<3%) and improved transmittance into the substrate at the visible wavelength range. The measured optical properties concur with the simulation results. The versatility of the PS-b-PDMS templates was further utilized for nanopatterning materials such as silicon-on-insulator substrates, gallium arsenide, aluminum indium phosphide, and gallium nitride, which are important in electronics and photonics. (C) 2018 Elsevier Inc. All rights reserved.