(A) study on process engineering of indium-based oxide semiconductor using atomic layer deposition and its application to high resolution flexible display

Abstract

Oxide semiconductors have been actively studied owing to their remarkable characteristics such as high mobility, low leakage current, large-area uniformity, and transparency for active matrix flat-panel displays, power devices, sensing devices and computing devices. Atomic layer deposition (ALD) has attracted much attention, particularly for applications in nanoelectronics because of its atomic-level controllability and high-quality product. This study deal with indium-based oxide semiconductor process engineering using atomic layer deposition and application to high resolution display which is 3-D structure thin film transistor. Firstly, ALD processing design was conducted the plasma-enhanced atomic layer deposition (PEALD) process was controlled to deposit a homogeneous indium aluminum oxide semiconductor film. Trimethylaluminum (TMA) and dimethyl aluminum isopropoxide (DMAI) were the two precursors used to form aluminum oxide. The TMA- and DMAI-based indium aluminum oxide films exhibited quite different composition characteristics. Thus, the surface reactions between indium and aluminum precursors during the multi-step (A→B→O) PEALD process were scrutinized by density functional theory (DFT) simulation. DMAI was utilized as the precursor of AlOx in the PEALD process, a carrier suppressor of an indium oxide (In$_2$O$_3$) semiconductor, to fabricate indium aluminum oxide thin-film transistors. The demand for ultra-high resolution displays for next-generation VR/AR display applications is increasing. Accordingly, scale-down of transistors is in progress, and research on vertical transistors and channel layers deposited by atomic layer deposition is required. This study presents a vertical channel oxide thin film transistor fabricated by PEALD with line width of 1 um and showing stable electrical properties under bending radius of 0.5mm without degradation. Our device serves as a suitable candidate for a transistor in next generation 2000 ppi foldable and rollable display.