Large-diameter roll mold fabrication method using a small-diameter quartz roll mold and UV nanoimprint lithography

The roll-to-roll (RTR) technique is a high-throughput method for nanoimprint lithography (NIL); however, the fabrication of the roll mold for RTR NIL is difficult because of the cylindrical shape of the mold. Roll molds are usually fabricated by rolling up a nickel-plated foil imprinted with a nanopattern, but this method generates a seam. To produce a seamless nanoscale mold, we have previously developed a technique for direct writing with an electron beam (EB) onto a rotating cylindrical substrate. The method uses a cylindrical substrate (the roll mold substrate) coated with a resist that is written upon directly by an EB while the roll mold substrate is rotated in a vacuum. However, the throughput of this technique is very low. In an attempt to overcome this problem, we investigated a roll diameter amplification method using direct transfer from a patterned small mold. The roll mold was made of synthetic quartz, and its diameter was 30 mm. This roll mold was dipped in hydrogen silsesquioxane, which acts as high-resolution negative-type EB resist. The mold coated with the EB resist was subjected to EB lithography at an acceleration voltage of 30 kV and an EB current of 100 nA. After development, 520 nm line patterns were obtained on the quartz roll mold. The transparent roll mold was subsequently used to transfer the pattern directly onto a large mold at a rotation speed of 0.2 rpm, a nip force of 60 N, and a UV dose of 60 mW/cm(2). The diameter of the large mold was 150 mm, and the mold was covered with a UV-curable film. The width of the transfer lines was 510 nm. By using a large mold made of the resulting patterned polymer, RTR UV-NIL was carried out at a feed speed of 1 mm/s, a nip pressure of 0.25 MPa, and a UV dose of 87 mW/cm2. The transfer film was the same UV-curable film. The replicated lines widths were 590 nm; this large value was caused by deformation of the polymer mold during the RTR NIL process. The roll diameter amplification method is therefore very effective for RTR UV-NIL, because a small-diameter roll can be used as the master mold. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3657524]