Multilayer block copolymer meshes by orthogonal self-assembly

Abstract

Continued scaling-down of lithographic-pattern feature sizes has brought templated self-assembly of block copolymers (BCPs) into the forefront of nanofabrication research. Technologies now exist that facilitate significant control over otherwise unorganized assembly of BCP microdomains to form both long-range and locally complex monolayer patterns. In contrast, the extension of this control into multilayers or 3D structures of BCP microdomains remains limited, despite the possible technological applications in next-generation devices. Here, we develop and analyse an orthogonal self-assembly method in which multiple layers of distinct-molecular-weight BCPs naturally produce nanomesh structures of cylindrical microdomains without requiring layer-by-layer alignment or high-resolution lithographic templating. The mechanisms for orthogonal self-assembly are investigated with both experiment and simulation, and we determine that the control over height and chemical preference of templates are critical process parameters. The method is employed to produce nanomeshes with the shapes of circles and Y-intersections, and is extended to produce three layers of orthogonally oriented cylinders.

Non-native three-dimensional block copolymer morphologies

“…For example, lamellar domains orient perpendicularly to underlying lamellar morphologies (Fig. 2)303132. This ‘crossed' alignment completely eliminates stretching/compression of the polymer chains along the long axis of the coil (i.e., normal to the lamellar interblock interface).…”

“…BCP assembly is known to be responsive to confinement333435, guiding trenches363738 (i.e., grapho-epitaxy3940), topographic disruptions41424344, and substrate roughness4546, corrugations303132 or faceting474849. BCPs typically respond according to commensurability, reorienting and distorting to preserve their bulk equilibrium morphology.…”

Non‐Native Block Copolymer Thin Film Nanostructures Derived from Iterative Self‐Assembly Processes

“…c,d) Nanomesh pattern obtained via orthogonal self‐assembly of PS‐ b ‐PDMS BCPs of different molecular weights on bare Si (scale bars: 100 nm) and on a circular template obtained by electron beam lithography from a hydrogen silsesquioxane resist (scale bars: 500 nm), respectively. Adapted under the terms of the Creative Commons Attribution 4.0 International License Copyright 2016, the Authors. Published by Springer Nature.…”

“…This intermediate “responsive layering” approach allows one to manipulate BCP self‐assembly toward non‐native 3D morphologies as each self‐assembled BCP film acts as both a component of the final functional structure and a guiding pattern for the subsequent nanostructured layers. Consequently, immobilized BCP patterns can be used as a topographic or chemical template for a subsequent BCP layer and complex 3D structures can be obtained by iterative self‐assembly of layers of BCPs with different molecular weights or compositions . Tavakkoli et al explored this particular facet for the formation of cross‐point structures derived from self‐assembly of BCPs with different periodicities .…”

Nanoscale Block Copolymer Self‐Assembly and Microscale Polymer Film Dewetting: Progress in Understanding the Role of Interfacial Energies in the Formation of Hierarchical Nanostructures

“…Extensive literature including comprehensive review articles on the directed self‐assembly of block copolymers is available . Many DSA approaches, for instance, aim at improving long‐range order in BCP SA, to enable pattern density multiplication and to guide BCP domains into distinct patterns matching requirements of semiconductor technologies . The guiding structures in DSA are mostly realized by chemical or topographical prepatterning of surfaces .…”