Roll-to-roll UV imprint lithography for flexible electronics

We propose a roll-to-roll UV imprint lithography tool as a way to pattern flexible PET foil with mu m-resolution. As a way to overcome dimensional instability of the foil and its effect on overlay, a self-align approach was investigated, that permits to make several layers in a single lithography step. Flexible Ni-stamps were used, with a single level and with 2 levels. The stamps were fabricated on wafers using conventional optical lithography and Si etching. Thin Ni replica, both single and multilevel, were obtained by electroplating using a thickness of 50 mu m. The flexible Ni stamps were attached on the main drum that is placed on a conventional roll-to-roll machine. Resist was dispensed drop by drop by valve-jet nozzle using solvent-free UV resist. The imprint speed was of 0.35 m/min, using a UV illumination of 2 W. Fifty imprints were made in a row, equivalent to 20 m foil length. High imprint quality was observed with good reproducibility. All features type were replicated, from 500 mu m contact pads to 800 nm wide trenches and 1 mu m wide lines. A resolution of 800 nm in 1 mu m thick resist was obtained for single level imprint. Multi-level imprints (2 levels) show the same quality in replication with a resolution of 1 gm. (C) 2011 Elsevier B.V. All rights reserved.