Highly Scalable and Robust Mesa-Island-Structure Metal-Oxide Thin-Film Transistors and Integrated Circuits Enabled by Stress-Diffusive Manipulation

Abstract

The increasing interest in flexible and wearable electronics has demanded a dramatic improvement of mechanical robustness in electronic devices along with high-resolution implemented architectures. In this study, a site-specific stress-diffusive manipulation is demonstrated to fulfill highly robust and ultraflexible amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) and integrated circuits. The photochemically activated combustion sol–gel a-IGZO TFTs on a mesa-structured polyimide show an average saturation mobility of 6.06 cm2 V−1 s−1 and a threshold voltage of −0.99 V with less than 9% variation, followed by 10 000 bending cycles with a radius of 125 μm. More importantly, the site-specific monolithic formation of mesa pillar-structured devices can provide fully integrated logic circuits such as seven-stage ring-oscillators, meeting the industrially needed device density and scalability. To exploit the underlying stress-diffusive mechanism, a physical model is provided by using a variety of chemical, structural, and electrical characterizations along with multidomain finite-element analysis simulation. The physical models reveal that a highly scalable and robust device can be achieved via the site-specific mesa architecture, by enabling generation of multineutral layers and fine-tuning the accumulated stresses on specific element of devices with their diffusion out into the boundary of the mesa regions. © 2020 Wiley-VCH GmbH