Preparation of Diamond Mold Using Electron Beam Lithography for Application to Nanoimprint Lithography

Diamond molds were fabricated by two types of fabrication processes, both of which use a conductive intermediate layer between the diamond surface and polymethylmethacrylate (PMMA) resist to prevent surface charge-up. Using a PtPd intermediate layer, electron beam lithography and ion beam etching, a denting line pattern of 600 nm width and 70 nm depth was fabricated. Using a carbon intermediate layer, electron beam lithography, PtPd lift-off and oxygen ion beam etching, a convex line pattern of 600 nm width and 110 nm height was fabricated. These diamond molds were pressed into PMMA on a silicon substrate that was heated to a temperature of 150°C and kept at a pressure of 23.5 MPa until the temperature dropped below 90°C, and then the diamond mold was released from the PMMA. The convex line pattern of 600 nm width and 150 nm height was imprinted using a denting diamond mold. The denting pattern of 1100 nm width and 180 nm height was imprinted using a convex diamond mold. PMMA patterns were transferred well over the imprinted area by the diamond molds.