Effect of UV-Ozone Treatment on the Performance of ZnO TFTs Fabricated by RF Sputtering Deposition Technique

In this paper, bottom-gate thin-film transistors (TFTs) with zinc oxide (ZnO) channels were grown on Si substrates with an SiO₂ dielectric layer via the radio-frequency sputtering technique. The ZnO films were then subjected to 16 min of ultraviolet (UV)-ozone treatment, which resulted in fewer oxygen vacancies, enhanced crystallization, lower strain, lower surface roughness, and higher thin-film density, as well as improved surface energy and adhesion properties of the gallium zinc oxide source/drain electrodes. The UV-ozone 16-min ZnO active layer TFT with the preferable resistivity values by Hall measurement results. The optimal UV-ozone treatment time (16 min) led to the smallest full-width at half-maximum (0.4138°), smallest strain (2.61 × 10^-3), highest thin-film density (5.78 g/cm³), lowest surface roughness (1.75 nm), and largest surface energy (65.3 mJ/m²). The saturation mobility, subthreshold voltage, ON/OFF current ratio, and trap density of the ZnO TFTs with optimal UV-ozone treatment were 4.54 cm² V^-1 S^-1, 0.28 V/decade, 2.02 × 10⁷, and 2.61 × 10¹¹ eV^-1 cm^-2, respectively, indicating the potential of this structure to be applied to large-area flat-panel displays.