Abstract
Emerging nanoscale applications in energy, electronics, optics, and medicine can exhibit enhanced performance by incorporating nanoshaped structures (nanoshape structures here are defined as shapes enabled by sharp corners with radius of curvature < 5 nm). Nanoshaped fabrication at high-throughput is well beyond the capabilities of advanced optical lithography. Although the highest-resolution e-beams and large-area e-beams have a resolution limit of 5 and 18 nm half-pitch lines or 20 nm half-pitch holes, respectively, their low throughput necessitates finding other fabrication techniques. By using nanoimprint lithography followed by metal-assisted chemical etching, diamond-like nanoshapes with ~3 nm radius corners and 100 nm half-pitch over large areas have been previously demonstrated to improve the nanowire capacitor performance (by ~90%). In future dynamic random-access memory (DRAM) nodes (with DRAM being an exemplar CMOS application), the implementation of nanowire capacitors scaled to <15 nm half-pitch is required. To scale nanoshape imprint lithography down to these half-pitch values, the previously established atomistic simulation framework indicates that the current imprint resist materials are unable to retain the nanoshape structures needed for DRAM capacitors. In this study, the previous simulation framework is extended to study improved shape retention by varying the resist formulations and by introducing novel bridge structures in nanoshape imprinting. This simulation study has demonstrated viable approaches to sub-10 nm nanoshaped imprinting with good shape retention, which are matched by experimental data.
Highlights
Applications in the areas of energy storage[1,2], nanoscale photonics[3], plasmonic structures[4], multibit magnetic memory[5], terabit per sq. in. magnetic recording[6], and bionanoparticles[7,8] require high-throughput patterning and complex shape control at the nanoscale.Among nanofabrication techniques, the state-of-the-art form of optical lithography—193 nm immersion (193i) lithography—has plateaued at a resolution of ~38 nm halfpitch for gratings and ~50 nm half-pitch for more complex structures
The addition of more crosslinkers enhances the crosslinking percentage; given that bulk crosslinking levels are not achieved by this method, it does not provide a complete solution for nanoshape retention
In a previous article, a nanowire capacitor with a diamond-shaped pattern possessing a 3 nm sharp corner radius and 100 nm half-pitch led to an improvement in the capacitance by 90% compared to the current state of the art, and a further 10× increase in performance was expected with 10 nm half-pitch patterns
Summary
Crosslinking percentages of 75% and 60%, respectively. The shape and size dependence is evident in these data. Crosslinking is a spatial phenomenon and the probability of bond formation at a point in the nanoshape is a function of the amount of material surrounding the point within a certain radius. In bulk resist, this probability is constant except for local stochastic variations. The cross and diamond crosslinking curves are not identical, especially below 10 nm This observation clearly shows that nanoshape size and shape adversely affect bonding below 25 nm. It is believed that the difference in the crosslinking percentage curves between the cross and diamond nanoshape is primarily driven by the shape differences, which in turn influence the average number of carbon double-bond neighbors available for crosslinking. This difference is due to a decision made to limit the bonding time for computational cost reasons
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