Flexible organic integrated circuits free of parasitic capacitance fabricated through a simple dual self-alignment method

Abstract

In integrated circuits (ICs), the parasitic capacitance is one of the crucial factors that degrade the circuit dynamic performance; for instance, it reduces the operating frequency of the circuit. Eliminating the parasitic capacitance in organic transistors is notoriously challenging due to the inherent tradeoff between manufacturing costs and interlayer alignment accuracy. Here, we overcome such a limitation using a cost-effective method for fabricating organic thin-film transistors and rectifying diodes without redundant electrode overlaps. This is achieved by placing all electrodes horizontally and introducing sub-100 nm gaps for separation. A representative small-scale IC consisting of five-stage ring oscillators based on the obtained nonparasitic transistors and diodes is fabricated on flexible substrates, which performs reliably at a low driving voltage of 1 V. Notably, the oscillator exhibits signal propagation delays of 5.8 µs per stage at a supply voltage of 20 V when utilizing pentacene as the active layer. Since parasitic capacitance has been a common challenge for all types of thin-film transistors, our approach may pave the way toward the realization of flexible and large-area ICs based on other emerging and highly performing semiconductors.

Keywords

flexible electronics / integrated circuits / organic thin-film transistors / parasitic capacitance / self-alignment

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