Abstract
Complex nanoshaped structures (nanoshape structures here are defined as shapes enabled by sharp corners with radius of curvature <5 nm) have been shown to enable emerging nanoscale applications in energy, electronics, optics, and medicine. This nanoshaped fabrication at high throughput is well beyond the capabilities of advanced optical lithography. While the highest-resolution e-beam processes (Gaussian beam tools with non-chemically amplified resists) can achieve <5 nm resolution, this is only available at very low throughputs. Large-area e-beam processes, needed for photomasks and imprint templates, are limited to ~18 nm half-pitch lines and spaces and ~20 nm half-pitch hole patterns. Using nanoimprint lithography, we have previously demonstrated the ability to fabricate precise diamond-like nanoshapes with ~3 nm radius corners over large areas. An exemplary shaped silicon nanowire ultracapacitor device was fabricated with these nanoshaped structures, wherein the half-pitch was 100 nm. The device significantly exceeded standard nanowire capacitor performance (by 90%) due to relative increase in surface area per unit projected area, enabled by the nanoshape. Going beyond the previous work, in this paper we explore the scaling of these nanoshaped structures to 10 nm half-pitch and below. At these scales a new “shape retention” resolution limit is observed due to polymer relaxation in imprint resists, which cannot be predicted with a linear elastic continuum model. An all-atom molecular dynamics model of the nanoshape structure was developed here to study this shape retention phenomenon and accurately predict the polymer relaxation. The atomistic framework is an essential modeling and design tool to extend the capability of imprint lithography to sub-10 nm nanoshapes. This framework has been used here to propose process refinements that maximize shape retention, and design template assist features (design for nanoshape retention) to achieve targeted nanoshapes.
Highlights
New applications in varied fields such as energy storage[1], nanoscale photonics[2], plasmonic nanostructures[3], multi-bit magnetic memory[4], terabit per square inch magnetic recording[5], and bio-nanoparticles[6, 7] require high-throughput patterning with complex shape control at the nanoscale
Higher-resolution large-area patterns are currently manufactured by complementing photolithography with self-aligned double patterning (SADP) and multiple lithography-etch steps
Directed self-assembly (DSA) is being explored, both SADP and DSA are primarily restricted to periodic features[8,9,10]
Summary
In all-atom MD, atoms are modeled as point particles with mass and optionally electric charge. Non-bonded interactions are divided into van der Waals and electrostatic components. The van der Waals interactions is modeling using a Lennard-Jones potential function and the electrostatic component with a Coulomb potential. KBT ð1Þ where, KEavg = average kinetic energy of the system of particles m = mass of particle v = velocity of particle kB = Boltzmann’s constant T = temperature. Note that the forcefield (from quantum mechanics), atom positions, and velocity profile (from statistical mechanics/kinetic theory) are the only inputs to the model. No other material properties are input, rather they are derived from the MD model. This capability of MD is powerful at the nanoscale
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