► Wireless Indium-Gallium-Zink-Oxide TranSmitters and Devices On Mechanically-Flexible Thin-Film Substrates (W I S D O M II)


Professor Dr.-Ing. Frank Ellinger

Technische Universität Dresden
Institut für Grundlagen der Elektrotechnik und Elektronik
Professur für Schaltungstechnik und Netzwerktheorie                                                   

Professor Dr. Gerhard Tröster

ETH Zürich
Electronics Laboratory – Wearable Computing

Project Summary

Today, electronics is implemented on rigid substrates. However, many objects in daily-life are not rigid- they are bendable, stretchable and even foldable. Examples are paper, tapes, our body, our skin and textiles. Until today there is a big gap between electronics and bendable daily-life items. Concerning this matter, the DFG priority program FFlexCom aims at paving the way for a novel research area: Wireless communication systems fully integrated on an ultra-thin, bendable and flexible piece of plastic or paper. With flexibility we mean in the following mechanical flexibility. In the last years the speed of flexible devices has massively been improved. However, to enable functional flexible systems and operation frequencies up to the sub-GHz range, the speed of flexible devices must still be increased by several orders of magnitude requiring novel system and circuit architectures, component concepts, technologies and materials. In this regard, the W I S D O M project has the following goals: – Development of technology for first fully integrated wireless flexible transmitter chip: Due to the high mobility of around 15 cm2/Vs in combination with the possibilities for low temperature device fabrication on plastic substrates, we will apply InGaZnO technology. In addition to the field effect transistors (FETs), appropriate inductors, capacitors, resistors and diodes are integrated on a single chip. – Operation frequency of transmitter and circuits of at least 25 MHz and up to 100 MHz: To maximize the operation frequency this transmitter can be based on an oscillator. Because of the positive feedback and since consequently oscillators need gains of only slightly beyond unity, operation up to close the maximum frequency of oscillation (fmax) of the technology is possible. Due to the amplification until saturation, sufficiently high output signals are generated which are suited to transmit signals up to 100 m. Data transmission up to 1 Mb/s is possible by on/off keying or pulse position modulation of the oscillator signal. – Improvement of the speed of flexible transistors up to 300 MHz: To increase the transit frequency (ft) and fmax of the InGaZnO based FETs up to 300 MHz, we will investigate flexible transistors with channel length of only 100 nm. These thin film transistor (TFTs) will be fabricated using a novel fabrication process based on focused ion beam etching. – Bending radii of fully transmitter chip down to 2 mm and strain investigations: We investigate the impact of strain induced by bending on the devices performance and research for circuit architectures enabling corresponding robustness. – Modelling of all required devices: We will advance e.g. our SPICE Level-3 TFT model. Bending effects will be included into the device models. – Considerations for applications: The research will focus on the data transmission for flexible sensor systems, e.g. for medical applications.