Innovative UV nanoimprint lithography using a condensable alternative chlorofluorocarbon atmosphere

The effectiveness of using a condensable gas in UV nanoimprint lithography has been demonstrated. The problem of bubble defects, which is inherent in UV nanoimprinting under non-vacuum conditions, can be overcome using a condensable alternative chlorofluorocarbon gas, 1,1,1,3,3-pentafluoropropane (PFP). UV nanoimprint lithography using PFP was successfully performed for a 45-nm half-pitch pattern with a thin residual layer, which is required for UV nanoimprinting. PFP reduces the viscosity and demolding force of the UV-curable resins. These properties are helpful in increasing the throughput and reliability of the UV nanoimprinting process. PFP occasionally causes large pattern shrinkage and degrades the pattern quality depending on the monomer chemical structures included in the UV-curable resins. These drawbacks can be mitigated by selecting monomers with low PFP absorption. We demonstrated that appropriate line-width roughness and line-edge roughness can be obtained for 22-nm node NAND flash memories and 20,000 repeated imprints were achieved with a single mold by using PFP.