Browsing by Subject "Nanoimprint"
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Item High-Throughput Transfer Imprinting for Organic Semiconductors(2013-08-06) Choo, GihoonDevelopment of nanoimprint lithography(NIL) has enabled high-throughput and high-resolution patterning over the optical limitation. In recent years, thermal nanoimprint has been used to directly pattern functional materials such as organic semiconductors because heat and pressure used in thermal nanoimprint do not damage functional materials. However, issues such as residual layer removal and mold contamination still limit the application of nanoimprint for organic semiconductor patterning. In this work, nanoimprint-based transfer imprinting of organic semiconductor is studied. In the same time the suggested technique is simulated with COMSOL multi-physics simulator to understand its mechanism. This transfer printing technique utilize thermal nanoimprint scheme to enable residual-layer-free patterning of organic semiconductors without mold contamination. The transfer imprinting technique is amenable to roll-to-roll process for high-throughput patterning of organic semiconductors for low-cost organic electronic applications.Item Nanoimprint Lithography for Functional Polymer Patterning(2012-02-14) Cui, DehuOrganic semiconductors have generated huge interested in recent years for low-cost and flexible electronics. Current and future device applications for semiconducting polymers include light-emitting diodes, thin-film transistors, photovoltaic cells, chemical and biological sensors, photodetectors, lasers, and memories. The performance of conjugated polymer devices depends on two major factors: the chain conformation in polymer film and the device architecture. Highly ordered chain structure usually leads to much improved performance by enhancing interchain interaction to facilitate carrier transport. The goal of this research is to improve the performance of organic devices with the nanoimprint lithography. The work begins with the controlling of polymer chain orientation in patterned nanostructures through nanoimprint mold design and process parameter manipulation, and studying the effect of chain ordering on material properties. After that, step-and-repeat thermal nanoimprint technique for large-scale continuous manufacturing of conjugated polymer nanostructures is developed. The actual chain orientation of molecular groups in polymer micro- and nanostructures patterning by nanoimprint is complicated. However, this information is crucial for intelligently controlling the electrical and photophysical properties of conjugated polymers by nanoimprint. Systematic investigation of polymer chain configuration by Raman spectroscopy is carried out to understand how nanoimprint process parameters, such as mold pattern size, temperature, and polymer molecular weight, affects polymer chain configuration. The results indicate that chain orientation in nanoimprinted polymer micro- and nanostructures is highly related to the nanoimprint temperature and the dimensions of the mold structures. The ability to create nanoscale polymer micro- and nanostructures and manipulate their internal chain conformation establishes an original experimental platform that enables studying the properties of functional polymers at the micro- and nanoscale and understanding their fundamental structure-property relationships. In addition to the impact on basic research, the techniques developed in this work are important in applied research and development. Large-area conjugated polymer micro- and nanostructures can be easily fabricated by thermal step-and-repeat nanoimprint for organic flat-panel displays, organic circuits and organic solar panels. The ability to manipulate chain orientation through nanoimprint presents a new route to fine-tune the electrical and photophysical properties of conjugated polymers, which can lead to improved performance for all organic electronics. The techniques developed here also allow for easy incorporation of other micro- and nanoscale soft functional polymers in miniaturized devices and systems for new applications in electronics, photonics, sensors and bioengineering.Item Simulation of UV nanoimprint lithography on rigid and flexible substrates(2016-12) Jain, Akhilesh; Bonnecaze, R. T. (Roger T.); Sreenivasan, S.V.; Willson, C. Grant; Schunk, P. Randall; Ganesan, VenkatNanoimprint lithography (NIL) is a low cost, high throughput process used to replicate sub-20 nm feature from a patterned template to a rigid or flexible substrate. Various configurations for NIL are analyzed and classified based on type of template and substrate. The steps involved in pattern transfer using roller template based NIL are identified and models to study these steps are proposed. Important process parameters such as maximum web speed possible, required UV intensity, minimum droplet size and pitch and required force on the roller are calculated. The advantages, disadvantages and optimal process window for the different configurations are identified. Droplet spreading is simulated in NIL with rigid substrates in order to study the effect of droplet size, droplet placement error, gas diffusion and template pattern on throughput and defectivity. Square arrangement is found to be the optimum arrangement for achieving minimum throughput. Large droplet-free regions on the substrate edge and error in droplet placement error have significant impact on the throughput. A fluid flow model with average flow permeability is presented to account for flow in the template patterns. Optimum droplet dispensing for multi-patterned templates is achieved by distributing droplet volume according to local filling requirements. Non-fill defects in NIL are classified into pocket, edge and channel defects. A model to predict the size of non-fill defects based on imprint time and droplet size is presented. Defect characterization is presented for various pattern-types. A model is presented to determine the time required for the encapsulated gas to diffuse into the resist. The coupled fluid-structure interaction in NIL with flexible substrate is studied by simulating the web deformation as the droplet spreads on the substrate. It is found that the flexible substrate can be modeled as a membrane due to the lack of rigidity. RLT variation reduces as the number of droplets or the web tension increases. For the magnitude of RLT variation, thinner residual layers require higher web tension. The position of the template on the substrate is important and template positioned at the corner of the substrate is found to provide the least RLT variation.