Water-Mediated Photochemical Treatments for Low-Temperature Passivation of Metal-Oxide Thin-Film Transistors

The low-temperature electrical passivation of an amorphous oxide semiconductor (AOS) thin-film transistor (TFT) is achieved by a deep ultraviolet (DUV) light irradiation-water treatment-DUV irradiation (DWD) method. The water treatment of the first DUV-annealed amorphous indium-gallium-zinc-oxide (a-IGZO) thin film is likely to induce the preferred adsorption of water molecules at the oxygen vacancies and leads to subsequent hydroxide formation in the bulk a-IGZO films. Although the water treatment initially degraded the electrical performance of the a-IGZO TFTs, the second DUV irradiation on the water-treated devices may enable a more complete metal oxygen metal lattice formation while maintaining low oxygen vacancies in the oxide films. Overall, the stable and dense metal oxygen metal (M-O-M) network formation could be easily achieved at low temperatures (below 150 degrees C). The successful passivation of structural imperfections in the a-IGZO TFTs, such as hydroxyl group (OH-) and oxygen vacancies, mainly results in the enhanced electrical performances of the DWD-processed a-IGZO TFTs (on/off current ratio of 8.65 X 10(9), subthreshold slope of 0.16 V/decade, an average mobility of ��6.94 cm(2) s(-1), and a bias stability of Delta V-TH �� 2.5 V), which show more than a 30% improvement over the simple DUV-treated a-IGZO TFTs.This work was partially supported by the Industrial Strategic Technology Development Program (No. 10045269) funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea) and Korea Evaluation Institute of Industry Technology (KEIT), by the Technology Innovation Program (No. 10047756) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea), and by the Industrial Strategic Technology Development Program (No. 10045145) funded the Ministry of Trade, Industry and Energy (MOTIE, Korea)