Improvement of the performance of ZnO TFTs by low-temperature supercritical fluid technology treatment

In this paper, the supercritical CO2 (SCCO2) fluid technology is successfully applied to improve the electrical characteristics of sputtered ZnO TFTs at low temperature (150 °C). After the treatment of SCCO2 fluids mixed with water, the ZnO TFT exhibited superior transfer characteristics and lower threshold voltage. According to X-ray photoelectron spectroscopy (XPS) analyses, the improvements were attributed to the increase of binding energies of Zn–O bonds, hydrogen-related donors and the reduction of traps at the grain boundaries in ZnO thin films. In addition, the crystalline quality and microstructure of ZnO thin films were also investigated by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The transmittance of the ZnO film was measured by an N&K analyzer 1280 (N&K Technology, Inc.), which is a new type of thin-film measurement system.