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Nanoimprint lithography (NIL) was placed on the 2004 ITRS Roadmap, thus signifying its growing potential as a viable next-generation lithography technique. A particularly promising NIL technology is Step-and-Flash Imprint Lithography in which the pattern from a quartz template is transferred into a UV-curable silicon-rich monomer. The process of squeezing the monomer film during the imprint process produces significant flow-related pressures on the template which result in out-of-plane distortions (OPD). These OPD inherently produce in-plane distortions which compromise the quality of the resulting features. A single droplet imprint process, wherein a single puddle of monomer is used to cover the entire active area, suffers from throughput limitations due to the low imprint velocities that are required to control the flow-related pressures exerted on the template. In response to these limitations, recent research has focused on a multiple droplet imprint process wherein many droplets are dispensed and coalesce during the imprint process, resulting in lower flow-related pressures. In this paper, a numerical model is described that is capable of predicting both the pressures and the template distortions during a multiple droplet imprint process. The model consists of a finite element structural model of the template interfaced to a fluid-dynamic model of the flow through the gap; the distortion of the template affects the pressure applied on the template and vice versa, therefore a coupled, fluid-structure model is required. The pressure distribution during the imprint process is described by an analytical solution to the Reynolds equation that is modified to account for the coalescing process as well as the affects of absorption and surface tension. The modified solution is developed and verified through the use of computational fluid dynamic simulations. Results are described for a nominal set of conditions and a parametric study of the effect of droplet density is presented.
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