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

• Applicant: Professor Dr.-Ing. Frank Ellinger
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 271795180

In W I S D O M (first phase) a fully integrated flexible, amorphous Indium-Gallium-Zinc-Oxide (IGZO) thin-film transistor (TFT) circuit technology was developed. The devices are integrated on a bendable 50 µm thin polyimide foil. A maximum frequency of oscillation (fmax) of up to 300 MHz and a transit frequency (fT) of up to 135 MHz were measured for TFTs with gate length of 0.5 µm. These results are world record values for IGZO TFTs on foil. Moreover, TFTs with gate length of 2 µm, higher yield and 85/40 MHz fmax/fT were designed enabling ICs with at least 20 transistors. Based on the latter technology, fully integrated transmitters for data communication are successfully demonstrated and measured. They are based on an on/off keying (OOK) modulator operating around 4 MHz which consumes only 0.7 mA at 3 V. Moreover, a fully integrated wireless bendable moisture sensor chip was designed envisioning e.g. the application for smart diapers. The chip includes the sensor, a decision circuit, an OOK transmitter, a frequency doubler and an antenna. Scalable compact models with good agreement between measured and simulated DC and high frequency characteristics were developed.The focus of W I S D O M II (new, second phase) will be on the development of a fully integrated bendable IGZO transceiver operating up to 100 MHz and 1 Mb/s, which consists of an optimized transmitter and receiver. We want to push the operating frequencies e.g. by: hybrid integration of our high speed but lower yield transistors for the speed relevant stages with up to 3 TFTs and the higher yield but slower transistors for the rest of the circuits requiring lower speed with up to 50 TFTs, frequency multipliers (e.g. × 8) in transmitters, quadrature oscillators enabling frequency quadruplication, frequency converter first and amplifier second receivers, and positive feedback to boost gain at highest frequencies while maintaining stability. Moreover, we want to improve the TFT speed, e.g. by further reduction of the gate length (e.g. with focussed ion beam techniques), active control of doping levels and traps, as well as reduction of contact parasitics. According to the FFlexCOM vision we want to show that wireless communication is possible using just a piece of bendable plastic foil without any rigid chips envisioning full communication transceivers which can be easily integrated in textiles.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1796: High Frequency Flexible Bendable Electronics for Wireless Communication Systems (FFLexCom)
• International Connection: United Kingdom
• Cooperation Partner: Professor Dr. Niko Münzenrieder