Asymmetric fluid-structure dynamics in nanoscale imprint lithography

similar. In Figures 6.7 and 6.8, the simulation results follow the experimentaldata for small values of time. For large t, there seems to be a DC offset in thedata. This discrepancy could be due to the factors previously discussed.Despite the differences in the actual values, these results indicate that theassumption of a lubrication flow governed by Reynolds equation can be used tomodel the squeezing process in SFIL. Further refinements can be made in boththe simulations and the experimental setup to obtain improved data, especially forsmaller film thickness measurements. An automated system that allows actualimprinting of the template onto a wafer substrate would probably yieldrepeatability in the data and be less prone to particle contamination.6.4.2 Experiments with Unfiltered WaterThe following data presented here are for two conditions. Initially, thewater used was unfiltered distilled water. It was believed that this water wassufficiently clean. However, it was decided that filtering this water with 0.02-micron filters could not adversely the results. Therefore, the first set of data isfrom unfiltered distilled water and the second set is from filtered distilled water.In this section results from the experiments with unfiltered water are presented.Figure 6.10 shows that the gap decreases very little for six microns ofdownward actuation. Further, the change in the angle of inclination relative to thesubstrate seems to be negligible. This suggests that particles between thetemplate and substrate have been squeezed very hard. Visual inspection throughthe quartz template shows that there are isolated particles distributed across thesurface of the substrate. However, only an automated active stage system canpotentially eliminate particles.90