Sub-Micron Oxide TFT for the Era of Oxide-Based Display

The oxide thin-film transistors (TFTs) with low processing temperature and high-performance metrics exhibit great potentials in advanced displays and flexible electronics. The demands of high integration density and high flexibility drive the investigations on the downscaling behavior and mechanical stability of oxide TFTs. This work investigates the channel length (L) downscaling of self-aligned top-gate (SATG) oxide TFTs and explores the mechanical stress instabilities of flexible double-gate (DG) TFTs. By optimizing 4-nm AlOx gate insulator (GI) and modifying the channel/GI interface, the high performance is successfully maintained on sub-500 nm oxide TFTs. Furthermore, the study reveals the impacts of the laser lift-off (LLO) process and mechanical stress on the flexible oxide TFT. The DG structure and fluorine plasma treatment can noticeably enhance the mechanical robustness of flexible oxide TFTs.

I. Introduction

Amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) have gained widespread attention in advanced displays and flexible integrated circuits (FICs) due to their exceptional performance, low power consumption, and simplified manufacturing processes [1], [2]. As the most representative AOS transistor, the Micro-scale amorphous indium-gallium-zinc (a-IGZO) TFT has been successfully applied to the mass production of large-area rigid displays. However, the increasing pixel-per-inch (PPI) of displays and growing integration density of FICs pose urgent demands on the downscaling of AOS TFTs. This is hindered by the parasitic short-channel effect [3], since the AOS channel is inherently populated with abundant native defects [4], thus demanding significantly strengthened gate controllability over such defective channel. Moreover, the AOS TFTs for flexible electronics further encounter the challenges of mechanical instabilities, plausibly also related to the diversified defect states in AOSs. The development of sub-Micron flexible AOS TFTs is highly expected to usher in the era of oxide-based flexible displays and electronics.