Patterning of aluminum-doped zinc oxide electrode using I-line lithography

Abstract

Among the metal oxide semiconductors, indium tin oxide is attractive because it has high carrier mobility, stability and transparency. But indium is rare in Earth’s crust and toxic. Also it is brittle and cannot be applied to flexible devices. On the other hands, the methods to fabricate the transistors are pulsed laser deposition, atomic layer deposition？, metal organic chemical vapor deposition, etc. These methods require high vacuum, and high temperature conditions, and therefore large scale fabrication is difficult. In this work, we used zinc and aluminum oxides due to their abundance and they can be used to flexible devices. Zinc and aluminum oxides do not make cracks that indium tin oxide makes. And also di-ketone ligands with vinyl moiety were used for photosensitivity. The sol-gel process was used, which does not require high vacuum and high temperature conditions. and enables large scale fabrication. We used photoinitiator for 365 nm irradiation. When the vinyl moiety is exposed by I-line, cross-linking is generated. Then, cross-linking makes zinc aluminum oxide compound insoluble in the developer and patterns of the oxide can be made on the substrate. Furthermore new ligand which has no need of photoinitiator was used. That ligand has amino benzene moiety. Amino benzene has better I-line absorption ability than first ligand when the ligand is exposed by I-line, $\pi$ to $\pi$ * transition occurs. After that, cross-linking is generated by hydrolysis and condensation. Finally, the low temperature solution-processed amorphous oxide thin film transistors were demonstrated using the photosensitive sol-gel process.