Control of bubble defects in UV nanoimprint

We studied UV nanoimprint in air and the elimination of bubble defects using pentafluoropropane, which has a vapor pressure of 0.15 MPa at 25 °C. Bubble defects are unavoidable when UV nanoimprint is carried out in air. Pillars fabricated in thin resin film by UV nanoimprint in air contain bubble defects since bubbles are not eliminated by resin squeezing and only a small amount of air is dissolved in the resin. By introducing pentafluoropropane under such experimental condition, bubble elimination by gas condensation was separately investigated. The bubble elimination phenomenon is completed within a few seconds under an imprint pressure of 0.5 MPa in a sufficiently high concentration of pentafluoropropane. No bubble defects are generated in the entire imprint area of 10×10 mm2 with an imprint pressure of 0.5 MPa at a hold time longer then 20 s and a pentafluoropropane flow higher than 150 sccm.