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

Abstract

Recently, thin-film transistors (TFTs) have extended their applications to diverse electronics such as flexible/wearable displays, [1-6] health monitoring sensors, [7-10] and artificial neuromorphic devices. [11-13] Particularly, there is growing interest in the display applications for bendable electronics which require high mechanical flexibility, relatively low-temperature processing, and high-resolution device

Skin-Compatible Amorphous Oxide Thin-Film-Transistors with a Stress-Released Elastic Architecture

“…In this modelling, a 30% lateral strain was applied to the a-IGZO TFT by considering the maximum strain of the epidermis [23,24]. As shown in Figure 1, the highest stress was induced in the gate dielectric layer for the conventional PDMS substrate because of the large Young's modulus of Al 2 O 3 (Table 1) [25]. Importantly, this simulation suggests that the reverse-trapezoid structure can efficiently lower the stress distributions in the whole region of the stretchable a-IGZO TFTs compared to conventional PDMS, as shown in Figure 1a,b.…”

“…On the contrary, the a-IGZO TFTs on the reverse-trapezoid PDMS showed about 5% variation of saturation mobility and threshold voltage under 10% strain. These variations in the electrical properties might be related to the generation of oxygen vacancy in a-IGZO thin-films by the mechanical stress, leading to a negative threshold voltage shift and increased saturation mobility of a-IGZO TFTs [25][26][27]. Although the electrical changes abruptly increased over 10% under 15% strain, importantly, the stretchable a-IGZO TFTs on the reverse-trapezoid PDMS exhibited appropriate operation as switching devices to realize stretchable TFT-based skin-compatible applications.…”

4‐1:Invited Paper:Highly Robust Flexible IGZO TFTs and Integrated Circuits

“…[3,4] The flexible devices can be transferred into stretchable substrates without obstructions and inconveniences to fulfill the established or commercialized complex fabrications. [5][6][7] So, the realization of highly flexible devices can be the most important foundation to obtain meaningful stretchable applications. Among state-of-the-art thinfilm transistors (TFTs), metal-oxide semiconductors are especially suitable materials for next-generation flexible and stretchable electronics owing to their high optical transparency and good electrical performance.…”

“…Due to mechanical weakness of the ultrathin substrate, various studies have attempted to achieve flexible feasibility of a-IGZO TFTs. [5,7,[9][10][11] New design for the devices was proposed to pattern the electrodes and semiconductor layers into mesh and strip shape. [7,12] Although the proposed layout can certainly improve the mechanical stability of a-IGZO TFTs, the maximum stress is generally occurred in gate insulator layers in the device structures due to their high young's modulus.…”

Stress-Released Amorphous Oxide/Carbon Nanotube CMOS Amplifier Circuits for Skin-Compatible Electronics

“…Based on the advancements, a nanofiber network of metal oxide TFTs enabled e-skin-like multifunctional sensors . However, it is known that the a -IGZO TFTs could suffer from various instabilities caused by the mechanical strain, resulting in diverse performance variation and degradation. , To address this issue, highly reliable flexible a -IGZO TFTs have been demonstrated on a 15 μm thick polyimide (PI) substrate by using the mesa structure, effectively lowering the stress induced in the films . PI substrate materials can be judiciously regarded as biocompatible because of the capacity to accommodate in vivo environments .…”