Bendable wireless sensors and millimetre-wave transmitters using thinned SiGe BiCMOS Acronym: Bend-IT

• Applicants: Professor Dr.-Ing. Frank Ellinger; Professor Dr. Bernd Tillack
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 356463945

Bend-IT aims at exploring and demonstrating the world-wide´s first mechanically-flexible wireless sensors operating at millimetre-wave frequencies. The project is based on a very fast silicon bipolar complementary metal-oxide-semiconductor (BiCMOS) technology, which is thinned below 20 µm to enable bendability. The technology features transistors with transit frequencies up to 500 GHz. Hence, very high operation frequencies of 200 GHz are possible, thereby massively reducing the antenna size and allowing its integration on the chip. This decreases circuit dimensions and costs for applications in the area of the future internet of things (IoT). BiCMOS based temperature, light and/or pressure sensors will be used. Power supply is enabled by flexible thin-film batteries provided by our partner Varta. Hence, for the first time, extremely thin and bendable active millimetre-wave sensor systems are realizable.The key scientific questions and corresponding challenges are as follows: How does the thinning impact devices (such as the antenna, transistors, transmission lines, capacitors, inductors and resistors) and circuits at such very high frequencies? As a promising side effect, the thinning will lower the substrate losses and improve the performances of the devices. Which impacts have the bending and the induced mechanical stress at such high frequencies? How can we measure the compact chips at millimetre-wave frequencies if they are bended? How can we model the thinning and bending? The thinning can be considered by adapting the parameters of existing device models. However, the characterization required for the modelling of the bending is challenging at millimetre-wave frequencies. Here we take advantage that in bended condition a contactless system testing via the integrated antennas is possible. Several approaches will be investigated to mitigate and compensate the system impact of bending. Examples: current mirrors with low sensitivity against bending, negative feedback and circuit topologies exhibiting opposite trends as function of mechanical stress. To realise a complete frontend with the given resources, analogue modulation is targeted. The sensor modulates a 200 GHz oscillator. By means of a 200 GHz power amplifier the modulated sensor signal is amplified to produce an output power beyond 20 mW. Finally, the signal is radiated via the on-chip antenna.

• DFG Programme: Research Grants