Viable strategy to minimize trap states of patterned oxide thin films for both exceptional electrical performance and uniformity in sol–gel processed transistors

A sustainable water etchant-based photopatterning method is proposed to achieve simultaneous oxide film patterning and remarkably minimize trap states of dielectric and semiconductor oxide films. By exquisitely controlling each processing parameter, well-defined aluminum oxide (AlO_x) dielectric and indium oxide (InO_x) semiconductor patterns are formed, despite using acid-free pure water etchant. The water etchant not only dissolves the nonultraviolet-irradiated regions but also promotes an effective hydrolysis reaction of irradiated regions, thereby forming low-defect oxide patterns. As a result, frequency-stable AlO_x capacitors with low leakage current and high-performance bias-stable InO_x TFTs with low activation energy are fabricated. In particular, photopatterned enhancement-mode InO_x TFTs exhibit remarkably improved electrical properties, stability, and uniformity—15-fold higher saturation mobility and remarkably low coefficient of variation of 12.04 cm² V⁻¹ s⁻¹ and 25.26%, respectively— compared with nonpatterned TFTs. With the proposed method, 3-V operating high-performance InO_x/AlO_x TFTs are successfully fabricated at a low processing temperature of 250 °C.