High aspect ratio fine pattern transfer using a novel mold by nanoimprint lithography

Abstract

To conduct our research, a Si mold with a high aspect nano trench pattern was fabricated using a new edge lithography process, and the pattern was replicated into PMMA films on Si wafer by thermal nanoimprint lithography. By using edge lithography, a SiO2 circular line pattern of 35 nm width and 3.5 μm height was obtained and the aspect ratio became 100. The Cr patterns were fabricated by a lift-off process by using the high aspect SiO2 nano patterns, and the Si substrate was etched by the advanced plasma etching of the gas switching process. A Si trench pattern of 25 nm width and 1.0 μm depth was obtained, and these Si trench patterns were used for nanoimprint molds. The aspect ratios of the nano trench patterns were about 10. The nano trench patterns were replicated into PMMA films with various molecular weights by thermal nanoimprint lithography. The pattern replication failed when the PMMA resins of 50 and 120 k molecular weights were used. It is found that the PMMA pattern was often broken during the demolding process and its strength was very important for the successful pattern replication of the high aspect pattern. A PMMA line pattern of 30 nm width and 230 nm height was successfully fabricated when the PMMA resin of 996 k molecular weight was used.