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

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