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1030-G04-04

Patterning Submicron Features on Flexible Plastic Substrates by Optical Lithography Mária Péter1, Wim de Laat2, Peter T. M. Giesen1, Cheng-Qun Gui2, and Erwin R. Meinders1 1 Holst Centre, TNO-Netherlands Organisation for Applied Scientific Research, High Tech Campus 31, 5656 AE Eindhoven, Netherlands 2 Customized Imaging Solutions, ASML Netherlands B.V., De Run 6501, 5504 DR Veldhoven, Netherlands ABSTRACT Manufacturing transistors on thin flexible polymer foils is challenging and differs from standard Si processing due to the dimensional instability of the substrate influenced by moisture uptake, temperature and handling. A thorough analysis of material properties of the tested foil was performed to understand its behavior during lithography and subsequently to improve the processing. Imaging experiments on 100 µm polyethylene naphthalate (PEN) foils were performed with a PAS 5500/100D ASML step and repeat I-line (365 nm) system equipped with reticles having features of several microns and also sub-micrometer dimensions. A foil lamination process was developed to improve the dimensional stability during processing and to achieve a good surface flatness crucial for sub-micrometer imaging. The optimum process window for sub-micrometer critical dimensions was determined by performing a Focus Exposure Matrix (FEM) experiment in which the energy and focus were increased stepwise. The optimum imaging conditions were derived from SEM analysis. The results indicated a reproducible and good patterning accuracy for making patterns below 1µm size. INTRODUCTION The ‘System-in-Foil’ program line of the recently established open innovation research centre, the Holst Centre (NL), together with its partners invests large efforts to develop electronics on non-conventional, thin plastic flexible substrates. The main advantages of using such substrates compared to conventional semiconductor materials lie in lower manufacturing costs, flexibility, rollability, lighter weight and durability upon impact. The most advanced organic electronic systems are high efficiency color displays based on organic light emitting devices (OLEDs) [1]. Significant technological progress has also been made regarding the fabrication of thin-film transistors (TFTs) [2, 3] and thin-film organic photovoltaic cells for the generation of low-cost solar energy [4, 5]. One of the most appealing challenges is to develop patterning technologies on thin flexible substrates that allow the fabrication of high performance thin-film transistors (TFTs). A transistor consists of several patterned layers, e.g. gate electrode, dielectric, source-drain electrodes, and semiconductor that must be well aligned with respect to each other. We are currently aiming for micron-sized electrodes, and exploring possibilities to reduce the feature sizes below 1 µm and to achieve overlay accuracies within 30% of the critical dimension (CD) between the layers. The most commonly mentioned fabrication technology to pattern flexible substrates is ink-jet printing [6]. Disadvanta