Study and optimization of the parameters governing the block copolymer self-assembly: toward a future integration in lithographic process

In this paper, we present our studies on polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymer systems to produce cylindrical morphology in the thin film configuration. More specifically, we focus on the different accessible parameters to optimize the processing conditions for the self-assembly of this block copolymer. We studied the self-assembly process of the block copolymer film spin-coated on different random brushes obtained by varying several parameters such as the film thickness, and the annealing time and temperature. We have shown that the thin-film morphology (in-plane, out-of-plane or mixed ones) critically depends on those different parameters and that a subtle optimization of them will provide almost defect-free nanostructures. We also examined the morphology of the self assembled features in the interior of the block copolymer thin film after the subsequent removal of the PMMA block structured domain. This process leads to the film top-nanostructures spanning across the whole film thickness. We evidenced also that high aspect-ratio nanostructures in bulk silicon can be obtained with such optimized films through CMOS-compatible dry-etching approach. To conclude, we show that the above-optimized self assembly parameters can be directly combined with 193nm-resist based patterns through the graphoepitaxy approach to achieve useful features for advanced lithography.