15 March 2016 Innovative method to suppress local geometry distortions for fabrication of interdigitated electrode arrays with nano gaps
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In this paper we present a method to optimize the lithography process for the fabrication of interdigitated electrode arrays (IDA) for a lift-off free electrochemical biosensor. The biosensor is based on amperometric method to allow a signal amplification by redox cycling. We already demonstrated a method to fabricate IDAs with nano gaps with conventional mask aligner lithography and two subsequent deposition processes. By decreasing the distance down to the nanometer range the linewidth variation is becoming the most critical factor and can result in a short circuit of the electrodes. Therefore, the light propagation and the resist pattern of the mask aligner lithography process are simulated to optimize the lithography process. To optimize the outer finger structure assistant features (AsFe) were introduced. The AsFe allow an optimization of the intensity distribution at the electrode fingers. Hence, the periodicity is expanded and the outer structure of the IDA is practically a part of the periodic array. The better CD uniformity can be obtained by adding three assistant features which generate an equal intensity distributions for the complete finger pattern. Considering a mask optimization of the outer structures would also be feasible. However, due to the strong impact of the gap between mask and wafer at contact lithography it is not practicable. The better choice is to create the same intensity distribution for all finger structures. With the introduction of the assistant features large areas with electrode gap sizes in the sub 100 nm region are demonstrated.
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S. Partel, S. Partel, G. Urban, G. Urban, "Innovative method to suppress local geometry distortions for fabrication of interdigitated electrode arrays with nano gaps", Proc. SPIE 9780, Optical Microlithography XXIX, 978015 (15 March 2016); doi: 10.1117/12.2218527; https://doi.org/10.1117/12.2218527

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