Orientation control of cylinder forming block-copolymer on a modulated substrate – a theoretical study

The self-assembly of block copolymers BCPs provides a robust tool for nano-scale patterning. The low miscibility of the polymers in each block drives phase segregation, while the arrangement of each block in the molecule limits the extent of spatial separation resulting in nanoscale periodic morphologies. Unfortunately, micro-phase separation of BCP thin films on uniform substrates are far from perfect. Corrugated substrates showed a strong influence of BCP self-assembly resulting in improved long range order and orientation control. In addition, the effect of spatial modulation was observed in multi-stacked BCP thin films, where the newly added BCP layers are influenced by the topographyand chemical characteristics of the preceding layers.

A simulation using SCFT is employed to investigate the role of several key parameters including the commensurability between layers’ periodicities, topography height, and surface preferentiality of the substrate, on the orientation of cylinder forming BCP. We employ periodic templates with varying amplitude and extent to demonstrate the parameter space in which in-plane parallel or perpendicular structures are preferred. An approximate model is utilized to rationalize the SCFT results and efficiently explore this large parameter space.