Organic Thin-Film Transistors and Circuits Fabricated by Stencil Lithography on Full-Wafer Flexible Substrates

Abstract

Electronic devices based on organic semiconductors, such as field-effect transistors (OTFTs) and organic diodes have attracted significant interest as possible inexpensive and flexible alternatives to inorganic devices. Despite considerable improvement in technology and in device properties, the sufficient level of reproducibility to insure industrial acceptance of these devices has not yet been reached. This work outlines the possibility of fabrication of various organic, pentacene-based, electronic devices and circuits on a single, flexible chip, using combination of classic photolithography techniques and several levels of full-wafer stencil fabrication methods. The results from the DC and AC characterization of fabricated devices and circuits are comparable to the state of the art and demonstrate the potential of the developed technology. Obtained OFETs show good MOSFET-like behavior in both transfer and output characteristics while reaching low-field mobility as high as µ0 = 0.5 cm2/Vs. Organic diodes present a fully functional rectification ability up to several hundreds of kHz as well as basic logic circuits as p-type inverters. We have demonstrated that the combination of standard photolithography and multi-level stencil lithography is a feasible, cost-effective and reliable fabrication method. In addition, it has been shown that the choice of electrode metals (Au for source and drain, Al for gate) based on their work function significantly improves the contact resistance and rectification properties of organic diodes.