Self-Aligned Metal Electrodes in Fully Roll-to-Roll Processed Organic Transistors

We demonstrate the production of organic bottom gate transistors with self-aligned electrodes, using only continuous roll-to-roll (R2R) techniques. The self-alignment allows accurate <5 mu m layer-to-layer registration, which is usually a challenge in high-speed R2R environments as the standard registration methods are limited to the millimeter range-or, at best, to tens of mu m if online cameras and automatic web control are utilized. The improved registration enables minimizing the overlap between the source/drain electrodes and the gate electrode, which is essential for minimizing the parasitic capacitance. The complete process is a combination of several techniques, including evaporation, reverse gravure, flexography, lift-off, UV exposure and development methods-all transferred to a continuous R2R pilot line. Altogether, approximately 80 meters of devices consisting of thousands of transistors were manufactured in a roll-to-roll fashion. Finally, a cost analysis is presented in order to ascertain the main costs and to predict whether the process would be feasible for the industrial production of organic transistors.