Directed block copolymer assembly for functional nanomaterials

Abstract

Block copolymer lithography has proven itself as a cost-effective, parallel, and scalable nanolithography for the densely packed periodic arrays of nanoscale features, whose typical dimension scale in 5 ~ 50 nm is beyond the resolution limit of conventional photolithography. Highly registered nanoscale morphologies in block copolymer thin films, that are achievable by directed assembly upon prepatterned substrates, are anticipated useful for diverse advanced applications including magnetic storage media, flash memory devices, and waveguides. Nevertheless, further progress of block copolymer lithography toward practical device fabrication has been largely impeded by the following formidable challenges; i) General strategy widely applicable to a spectrum of functional materials is required; ii) Substrate prepatterning must be compatible to a conventional parallel photolithography for low-cost, high-throughput process; iii) Overlay process should be allowed for complicated multi-layered device architectures; and iv) Various shapes of nanoscale features must be achievable for device oriented nanolithography. Herein, we present universal block copolymer lithography for a broad spectrum of materials including metals, semiconductors, ceramics, and polymers. Combining advanced film deposition techniques with block copolymer nanotemplates yielded the nanopatterned films of the various functional materials. The low surface roughness and sufficient surface functionality of the target functional materials were crucial for well-ordered nanostructured morphology. Furthermore, we demonstrate soft graphoepitaxy of block copolymer assembly as a facile, scalable nanolithography for highly ordered sub-30-nm scale features. Various morphologies of hierarchical block copolymer assembly were achieved by means of disposable topographic confinement of photoresist pattern. Unlike usual graphoepitaxy, soft graphoepitaxy generates the functional nanostructures of metal and semiconducto...