UV-nanoimprint with the assistance of gas condensation at atmospheric environmental pressure

Abstract

Nanoimprint should be carried out in an ordinary environment from the standpoint of cost-performance. However, bubble defects arise when the process is done in air and the problem can become worse with large patterns and thin resin films. UV-nanoimprint using resin droplets reduces air capture by expelling air during resin spreading and, in some cases, achieves bubble free UV-nanoimprint by air dissolution in resin. When the authors simulated the smooth spreading of a large resin droplet in wafer warping, resin spreading occurred on mold plateaus but hardly reached into mold recesses where a significant amount of air was sealed and the air in a mold recess was not completely dissolved in resin within 10 min under an imprint pressure of 0.5 MPa. In contrast, a captured gas of concentrated pentafluoropropane (CHF2CH2CF3, 1,1,1,3,3-pentafluoropropane, HFC-245fa, CAS No. 460-3-1) whose vapor pressure is 0.15 MPa at room temperature was completely condensed and dissolved within 2 s, leaving no trace of bubble defects in UV-nanoimprint. UV-nanoimprint with the assistance of gas condensation at atmospheric pressure thus handles spin coat resin film and dramatically improves throughput by quickly eliminating bubble defects. The authors confirmed that the process is applicable to thin resin film whose resulting residual layer is 25 nm thick.