Pattern Generation by Using Multi-Step Room-Temperature Nanoimprint Lithography

We have demonstrated multi-step room-temperature nanoimprint lithography (RTNIL) using polystyrene (PS, average molecular weight 97 kg/mol) as the polymer layer for imprinting complex patterns. In separate experiments, single, double, and multiple (up to 10) sequential imprint steps were performed at imprint pressures between 1 to 30 MPa. To accomplish this demonstration, we designed and built a tool that controllably and repeatedly translated and pressed a sample into a stationary mold. The demonstrated inter-step alignment accuracy of this tool was ∼500 nm. Results of these experiments revealed the polymer deformation that results when nanoimprint is used to further deform a previously structured surface. The molds used in these experiments consisted of 400-nm-period diffraction gratings, as well as of rectangular structures of varying aspect ratios, ranging from 150 to 300 nm wide.