Simulations of novel nanostructures formed by capillary effects in lithography

High aspect ratio three-dimensional nanostructures are of tremendous interest to a wide range of fields such as photonics, plasmonics, fluid mechanics, and biology. Recent developments in capillary force lithography (CFL) have focused on taking advantage of the formation of menisci to enhance the functionality of small size-scale structures. In this study, simulations of the three-dimensional shapes of equilibrium menisci formed in capillaries with various cross-section geometries are studied. The capillary cross sections include regular polygons and equilateral star-shapes with sharp and rounded corners. The characteristic dimension of the physical lithography systems which are simulated is on the order of 100 nm. At such size-scale, surface-tension-effects are predominant, and as a consequence, our simulations demonstrate that nanometer-sized structures with great application potentials can be fabricated. Specifically, this study demonstrates that surfaces with three-dimensional nanoscale structures can be fabricated from templates with micron or sub-micron features through the development of cusps in the corners of the polygonal capillaries. Quantitatively, the effects of contact angle, corner angle, meniscus confinement, and corner rounding radius are examined and scaling analyses are presented to describe the dependencies of the height variation across the meniscus on these parameters. These simulations serve as useful guides for extending the development and implementation of capillary force lithography.

Here we show the elevations as well as the three-dimensional profile of the menisci formed in polygonal and star-shaped capillaries.Figure optionsDownload high-quality image (68 K)Download as PowerPoint slideResearch highlights
► At zero gravity, menisci formed in capillaries with regular polygonal or star-shaped cross sections are partial spheres.
► Analytical solutions of the height variation on the menisci formed in regular polygonal and star-shaped capillaries are presented.
► Height variation of the meniscus shows power-law dependency on the rounding radius of the corners of polygonal or star-shaped capillaries.
► High aspect ratio three-dimensional structures can be fabricated by using star-shaped capillaries in CFL.