Jason E. Meiring

Mesoscale modeling for SFIL simulating polymerization kinetics and densification

Step and Flash Imprint Lithography (SFIL) is a revolutionary next generation lithography option that has become increasingly attractive in recent years. Elimination of the costly optics of current step and scan imaging tools makes SFIL a serious candidate for large-scale commercial patterning of critical dimensions below ~50 nm. This work focuses on the kinetics of the UV curing of the liquid etch barrier and the resulting densification/contraction of the etch barrier as it solidifies during this step. Previous experimental work in our group has measured the bulk densification of several etch barrier formulations, typically about 9 % (v/v). It remains unknown, however, how much etch barrier contraction occurs during the formation of nano-scale features. Furthermore, it is of interest to examine how changes in monomer pendant group size impact imprinted feature profiles. This work provides answers to these questions through a combination of modeling and experimental efforts. Densification due to the photopolymerization reaction and the resulting shift from Van der Waals’ to covalent interactions is modeled using Monte-Carlo techniques. The model allows for determination of extent of reaction, degree of polymerization, and local density changes as a function of the etch barrier formulation and the interaction energies between molecules (including the quartz template). Experimental efforts focus on a new technique to examine trench profiles in the quartz template using TEM characterization. Additionally, SEM images of imprinted images from various etch barrier formulations were examined to determine local contraction of the etch barrier. Over a large range of etch barrier formulations, which range from 10 - 20 % volumetric contraction as bulk materials, it was found that dense 100 nm lines printed approximately the same size and shape.

Effects of etch barrier densification on step and flash imprint lithography

Previous work with the mechanical properties of step and flash imprint lithography etch barrier materials has shown bulk volumetric shrinkage trends that could impact imprinted feature dimensions and profile. This article uses mesoscopic and finite element modeling techniques to model the behavior of the etch barrier during polymerization. Model results are then compared to cross section images of template and etch barrier. Volumetric shrinkage is seen to impact imprinted feature profiles largely as a change in feature height.

Modeling of Self-Assembly Dynamics of Photolithographically Patterned MUFFINS Biosensor Arrays

The ability to mass produce biosensor arrays at low costs is an important target for the diagnostics industry. Our group has previously explored the batch production of mesoscale sized hydrogels as platforms for biosensors using photolithographic techniques. The individual hydrogel features were self-assembled through lateral capillary interactions to form a closed packed configuration and the pre-polymer medium was subsequently UV-cured to form the array. To understand the self-assembly dynamics, we investigated, through simulation, the flotation behavior of two assembling particles and its dependence on physical constants such as surface tension and particle density. Simulation results revealed that the objects tilt toward each other as they came into proximity. The tilt angle decreased with increasing surface tension but increased with increasing particle density. Understanding the details of the flotation behavior is necessary in the development of a full scale self-assembly model.