UV roll-to-roll nanoimprint lithography (R2RNIL) is a patterning technique for continuous replication of nano- and micro-scale features from a template to a flexible or rigid substrate. This patterning technique can, for example, enable the manufacture of bit-patterned magnetic storage media and photonics for displays. The UV R2R nanoimprint process consists of ink-jetting thousands of micron-scale drops on a substrate filling the patterned template by capillary and viscous forces, photo-polymerization of the imprint material and de-molding of the patterned resist. Two critical parameters in the process are: the residual layer thickness (RLT), which should be uniform and thin for the subsequent etch processing; and the imprint time, which should be small for high-throughput.
A multi-scale model and simulation is created for the filling process to predict the RLT and imprint time for different processing conditions. The model includes the capillary elastohydrodynamics to study the coupled fluid-structure interaction of the flexible substrate during drop merging and feature filling and is based on lubrication and membrane theory. We have created a multi-drop simulation capable of simulating the flow and merging of more than a 1000 drops, and predicting the variations of RLT and imprint time as a function of biaxial and uniaxial web-tension, the magnitude of the web-tension, the position of the template, the number and arrangement of drops, and the viscous and surface wetting characteristics of the fluid. We show that imprint time decreases in proportion to the initial number of drops. The variation of the RLT depends sensitively on the web-tension and direction, the distribution of droplets and the location of the template. These results are summarized in a set of operating rules for R2RNIL.