104 research outputs found

    Fabrication and AC performance of flexible Indium-Gallium-Zinc-Oxide thin-film transistors

    Get PDF
    The internet of things or foldable phones call for a variety of flexible sensor conditioning and transceiver circuits. However, the realization of high-performance, large-area, and deformable analog circuits is limited by the materials and the processes compatible with mechanically flexible substrates. Among the different semiconductors, InGaZnO is one of the most promising materials to realize high-frequency flexible thin-film transistors (TFTs) and circuits. In this work, the effect of different geometries, including self-aligned, vertical, and double-gate structures on the AC behaviour of flexible IGZO TFTs is presented. All TFTs are based on Al2O3 insulating layers, InGaZnO semiconductor, and polyimide substrates. The presented TFTs exhibit state-of-the-art performance including a field-effect mobility up to 15 cm2 /Vs and a mechanical bendability down to radii of 3.5 mm. Due to different trade-offs required in the fabrication, flexible IGZO TFTs with the shortest channel length of 160 nm do not exhibit the highest measured frequency, whereas exceptional maximum oscillation and transit frequencies of 304 MHz and 135 MHz are demonstrated for 500 nm long self-aligned TFTs. Such optimized transistors can be used to realize entirely flexible analog circuits leading towards imperceptible electronic systems

    Flexible In-Ga-Zn-O thin-film transistors with sub-300-nm channel lengths defined by two-photon direct laser writing

    Get PDF
    In this work, the low-temperature (≤ 150 °C) fabrication and characterization of flexible Indium-Gallium-ZincOxide (IGZO) top-gate thin-film transistors (TFTs) with channel lengths down to 280 nm is presented. Such extremely short channel lengths in flexible IGZO TFTs were realized with a novel manufacturing process combining two-photon direct laser writing (DLW) photolithography with Ti/Au/Ti source/drain e-beam evaporation and lift-off. The resulting flexible IGZO TFTs exhibit a saturation field-effect mobility of 1.1 cm2V -1 s -1 and a threshold voltage of 3 V. Thanks to the short channel lengths (280 nm) and the small gate to source/drain overlap (5.2 µm), the TFTs yield a transit frequency of 80 MHz (at 8.5 V gate-source voltage) extracted from the measured S-parameters. Furthermore, the devices are fully functional when wrapped around a cylindrical rod with 6 mm radius, corresponding to 0.4 % tensile strain in the TFT channel. These results demonstrate a new methodology to realize entirely flexible nano-structures, and prove its suitability for the fabrication of short-channel transistors on polymer substrates for future wearable communication electronics

    Influence of uniaxial bending on IGZO TFTs: A study of materials and device

    Get PDF
    In recent years flexible electronics have gained relevance with applications such as displays, sensors and wearables. In that regard, studying how flexible transistors behave under bending has become of major importance. This work aims to fabricate indium gallium zinc oxide (IGZO) Thin Film Transistors (TFT) with the best bendability possible, without any major changes in the production techniques already used in the industry. To understand the influence of the substrate on flexible devices, TFTs were fabricated on polyimide substrates using different thicknesses, down to 25 μm, with and without parylene encapsulation layers on top of the device stack. To determine the position of the neutral strain plane, nanoindentation measurements were performed on different device layers at IKTS-Fraunhofer, within BET-EU project. The delamination of the substrates is a critical step, especially for thinner substrates. The concept of “paper blade” was used in this project to improve the yield of the delamination process. Initial bending measurements, using a 75 μm thick substrate, showed that bending radii of 45, 25 and 15 mm do not permanently change the performance of the TFTs. Tensile bending measurements with a radius of 1.25 mm were also performed, revealing that the 75 μm thick substrate achieves critical failure in <500 cycles, while the thinner substrate (25 μm) could withstand almost 1000 cycles. The most common failure mechanism observed under tensile bending was the appearance of cracks in the oxide dielectric when in direct contact with the polyimide substrate. These cracks do not appear in regions where molybdenum gates were in contact with the substrate, hence the mismatch between the coefficient of thermal expansion of the substrate and the dielectric thin film were identified as the reason for failure. This work shows that, even with intrinsically rigid materials as oxides and metals, it is possible to obtain reliable flexible TFTs, provided that proper stack engineering is considered for their fabrication

    Metal oxide semiconductor thin-film transistors for flexible electronics

    Get PDF
    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular, the realization of large-area digital circuitry like flexible near field communication tags and analog integrated circuits such as bendable operational amplifiers is presented. The last topic of this review is devoted for emerging flexible electronic systems, from foldable displays, power transmission elements to integrated systems for large-area sensing and data storage and transmission. Finally, the conclusions are drawn and an outlook over the field with a prediction for the future is provided

    Flexible a-IGZO phototransistor for instantaneous and cumulative UV-exposure monitoring for skin health

    Get PDF
    Flexible thin‐film phototransistors based on amorphous indium‐gallium‐zinc‐oxide semiconductor and a novel read‐out scheme allow for both real time and cumulative measurement of the ultraviolet light intensity. Furthermore, encapsulation in polydimethylsiloxane and lamination to human skin, as well as mechanical stability of the device is presented

    Radio frequency electronics on plastic

    Get PDF
    In this paper the recent progress of active high frequency electronics on plastic is discussed. This technology is mechanically flexible, bendable, stretchable and does not need any rigid chips. Indium Gallium Zinc Oxide (IGZO) technology is applied. At 2 V supply and gate length of 0.5 μm, the thin-film transistors (TFTs) yield a measured transit frequency of 138 MHz. Our scalable TFT compact simulation model shows good agreement with measurements. To achieve a sufficiently high yield, TFTs with gate lengths of around 5 μm are used for the circuit design. A Cherry Hopper amplifier with 3.5 MHz bandwidth, 10 dB gain and 5 mW dc power is presented. The fully integrated receiver covering a plastic foil area of 3 × 9 mm2 includes a four stage cascode amplifier, an amplitude detector, a baseband amplifier and a filter. At a dc current of 7.2 mA and a supply of 5 V, a bandwidth of 2 - 20 MHz and a gain beyond 15 dB were measured. Finally, an outlook regarding future advancements of high frequency electronics on plastic is given
    corecore