Computer Aided Patterning Design for Self-Assembled Microsphere Lithography (SA-MSL)

Abstract

In this paper, we use a finite difference time domain solver to simulate the near field optical properties of self-assembled microsphere arrays when exposed to an incoherent light source. Such arrays are typically used for microsphere lithography where each sphere acts as a ball lens, focusing ultraviolet light into an underlying photoresist layer. It is well known that arrays of circular features can be patterned using this technique. However, here, our simulations show that additional nanometer scale features can be introduced to the pattern by optimising the sphere dimensions and exposure conditions. These features are shown to arise from the contact points between the microspheres which produce paths for light leakage. For hexagonally close packed arrays, the six points of contact lead to star shapes in the photoresist. These star shapes have subfeature sizes comparable to the current achievable resolution of low-cost fabrication techniques.

Nanopatterning with Photonic Nanojets: Review and Perspectives in Biomedical Research

“…A straightforward method to increase processing throughput is exploiting multiple nanojets in parallel. Nanojet parallelization has been traditionally achieved by using an array of self-assembled microspheres [ 79 , 80 ]. In general, simple processes, such as spin coating, Langmuir–Blodgett, and template-assisted self-assembly [ 81 ], suffice to obtain a monolayer of hexagonally arranged spheres on top of a hydrophilic substrate [ 81 ].…”

Hole, Convex, and Silver Nanoparticle Patterning on Polystyrene Nanosheets by Colloidal Photolithography at Air–Water Interfaces

“…Colloidal lithography is an advanced facile, inexpensive, and high-throughput technique for fabricating various periodic micro- and nanostructural arrays, including nanoholes, nanopillars, nanorings, and even asymmetrically shaped patterns. − In this technique, single- or multilayered colloidal crystals are employed as templates or masks that are first deposited on a processable substrate, which is then subjected to the main nanofabrication process, such as deposition, − reactive-ion etching (RIE), − etchant-based wet etching, and illumination with ultraviolet (UV) light. − Further postprocessing is generally required to construct complex target structures on the substrate, in which the processing steps depend on the target structure.…”

“…UV-light-assisted colloidal lithography, i.e., colloidal photolithography, is one of the most widely used colloidal lithography techniques because it can be used under atmospheric conditions without special processing equipment. − In conventional colloidal photolithography, UV light is focused on small photoreactive layer spots underneath a colloidal monolayer, leading to the formation of patterns in the photoreactive film. Furthermore, oblique illumination with UV light shifts the focusing position from just under the colloid to one that is not in contact with the colloid, enabling patterns to be carved at desired positions on the underlying film.…”

“…Furthermore, oblique illumination with UV light shifts the focusing position from just under the colloid to one that is not in contact with the colloid, enabling patterns to be carved at desired positions on the underlying film. Positive or negative photoresists have been exclusively used as underlying films; − consequently, adapting conventional polymers for use in colloidal photolithography would greatly expand its applicability. , …”