Boundary-directed epitaxy of block copolymers

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 technologicallyuseful 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.

Materials Science Challenges to Graphene Nanoribbon Electronics

“…Unless a scalable lithography technique with much improved resolution is developed, it is not clear if lithography will ever yield sub-10 nm wide GNRs with smooth edges, needed to harness superior electronic properties. There have been a number of promising efforts to pattern sub-10 nm features: notably, directed self-assembly (DSA) of block copolymers, extreme ultraviolet (EUV) lithography, and self-aligned quadruple patterning (SAQP). , While most experimental and simulation studies agree that edge roughness is detrimental to the performance of GNR FETs, ,, other works have concluded that a small amount of edge roughness is acceptable and will not significantly degrade the I on / I off or I on . This dichotomy is further evidenced by the demonstration of superior FET performance using GNRs grown heteroepitaxially in h-BN trenches that may possess mixed edge character .…”

“…More work is needed to reduce pitch, decrease seed size, and improve seed uniformity in order to realize dense unidirectional arrays of more monodisperse sub-5 nm GNRs (Figure ). One approach to realizing tightly pitched sub-5 nm seeds could be to exploit directed self-assembly using block copolymers in combination with infiltration synthesis. ,− Regarding challenge 3, devices realizing high G on approaching the quantum conductance limit of 77 μS (2 e 2 / h ) still need to be demonstrated. The GNRs synthesized on Ge have long segments of smooth armchair edges, but more work is needed to elucidate the potential effect of the minor edge roughness that may exist on charge transport properties.…”

Hierarchical Self-Assembly of Thickness-Modulated Block Copolymer Thin Films for Controlling Nanodomain Orientations inside Bare Silicon Trenches

“…Nanodomain (2): When W = 480 nm, there are tendencies of forming BCP nanodomains both parallel to the sidewall (L║) and bottom surface (L═) (Figure 1e). As a result, a T-junction tilt boundary of the BCP nanodomain [29][30][31] is formed and well-aligned along the thickness-gradient direction (T = 0.83 L0, L0 = periodicity of the lamellar structure). Figure 1f).…”

Self-Aligned Assembly of a Poly(2-vinylpyridine)-b-Polystyrene-b-Poly(2-vinylpyridine) Triblock Copolymer on Graphene Nanoribbons

“…The model used in this work relies on a particle-based representation of copolymer molecules, which has been described extensively in the literature − and validated with available experimental data for copolymer thin films. − Here, we only mention the model’s main characteristics that are used to simulate our system of interest. All n A- b -B- b -A block copolymer chains in our system are in a constant volume and constant temperature environment and discretized into N beads.…”