C-Axis Aligned Crystalline InSnZnO Thin Film Using Mist Chemical Vapor Deposition and Deposition/Annealing Cyclic Method for Thin-Film Transistors Applications

Abstract

The mist chemical vapor deposition (mist-CVD) is used to deposit the $\textit{c}$ -axis aligned crystalline (CAAC) indium–tin–zinc oxide (InSnZnO) thin film, and the deposition process including two steps. The first step of InSnZnO deposition is to form a thin film on the substrate and the second step is an annealing process that improves the crystallinity of the InSnZnO thin film. By repeating the above two steps for four times, a 20-nm-thick CAAC-InSnZnO thin film is obtained. The X-ray diffraction (XRD), selective are electron diffraction, X-ray photoelectron spectroscopy (XPS), and Tauc plot are used to characterize the material properties of the CAAC-InSnZnO film. Moreover, the mist-CVD deposited CAAC-InSnZnO film is used as a channel layer of the thin-film transistor (TFT). Compared with the amorphous InSnZnO (a-InSnZnO)-based TFT, the CAAC-InSnZnO-based TFT exhibits higher field-effect mobility (68.1 cm $^{\text{2}}\cdot$ V $^{-\text{1}}\cdot$ s $^{-\text{1}}\text{)}$ , steeper subthreshold swing (SS) (83.7 mV/dec), larger ON/OFF current ratio (10 $^{\text{8}}\text{)}$ , and lower OFF-state drain leakage current (3.2 pA). In addition, the CAAC-InSnZnO TFT has more stable electrical characteristics after the negative bias illumination stress (NBIS) testing than the a-InSnZnO TFT.