Abstract
Directed self-assembly of block copolymers (BCPs) enables nanofabrication at sub-10 nm dimensions, beyond the resolution of conventional lithography. However, directing the position, orientation, and long-range lateral order of BCP domains to produce technologically-useful patterns is a challenge. Here, we present a promising approach to direct assembly using spatial boundaries between planar, low-resolution regions on a surface with different composition. Pairs of boundaries are formed at the edges of isolated stripes on a background substrate. Vertical lamellae nucleate at and are pinned by chemical contrast at each stripe/substrate boundary, align parallel to boundaries, selectively propagate from boundaries into stripe interiors (whereas horizontal lamellae form on the background), and register to wide stripes to multiply the feature density. Ordered BCP line arrays with half-pitch of 6.4 nm are demonstrated on stripes >80 nm wide. Boundary-directed epitaxy provides an attractive path towards assembling, creating, and lithographically defining materials on sub-10 nm scales.
Highlights
Directed self-assembly of block copolymers (BCPs) enables nanofabrication at sub-10 nm dimensions, beyond the resolution of conventional lithography
Assembly of vertical lamellae can be controlled by tailoring template dimensions[20,21,22,23] as well as interfacial interactions between the template surfaces and polymer blocks[20,24], and feature density can be multiplied compared to the template dimensions to enhance resolution beyond the limits of conventional lithography[25,26]
Vertical lamellae propagate into the interior of each stripe, resulting in registered vertical line arrays that selectively form on stripes, self-align parallel to the boundaries, and register to wide and incommensurate stripes to multiply the feature density
Summary
Directed self-assembly of block copolymers (BCPs) enables nanofabrication at sub-10 nm dimensions, beyond the resolution of conventional lithography. Graphoepitaxy uses topographic features, such as trenches, whereas chemoepitaxy uses periodic chemical patterns to direct assembly of BCPs with controlled domain position, orientation, and lateral order. In both techniques, assembly of vertical lamellae can be controlled by tailoring template dimensions[20,21,22,23] as well as interfacial interactions between the template surfaces and polymer blocks[20,24], and feature density can be multiplied compared to the template dimensions to enhance resolution beyond the limits of conventional lithography[25,26]. The graphene stripes are atomically thin and smooth, presenting minimal topography, and have atomically faceted edges, resulting in abrupt transitions in surface composition at each stripe edge
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