Optimization of Sputtering Parameters and Their Effect on Structural and Electrical Properties of CAAC-IGZO Thin-Film Transistors

A c-axis aligned crystalline indium gallium zinc oxide (CAAC-IGZO) possesses unique properties beneficial for thin-film transistors (TFTs). In this study, we investigate the effect of oxygen ratio and radio frequency (RF) power on the structural, electrical, and operational characteristics of CAAC-IGZO thin films. Films were deposited on SiO2 substrates using an RF sputtering system equipped with a target containing In, Ga, Zn, and O with a composition ratio of 1:1:1:4. The effect of oxygen percentage on the structural characteristics was analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM). The oxygen percentage in the film was found to play a crucial role in forming the CAAC-IGZO and orientation of the thin films. With increasing O2 fraction, the (009)-preferred orientation of the films improved. X-ray absorption spectroscopy also validated the improved orientations of the CAAC-IGZO with high O2 concentrations up to 70%. In terms of TFT performance, however, the device with 3.3% oxygen exhibited the best performance with a saturation mobility of 10.9 cm2 V- 1 s- 1. TFT devices were prepared at a low oxygen fraction (10%) with different RF power inputs from 100 to 250 W, where the device prepared with highest power (250 W) showed the best performance.

Automated summary

The effect of oxygen ratio and radio frequency (RF) power on the properties of CAAC-IGZO thin films was investigated. It was found that oxygen percentage plays a crucial role in film orientation, with 3.3% oxygen showing the best performance in TFT devices.