Maskless Mechanical Structuring of Thermally Annealed ITO Electrodes for Transparent Thin-Film Transistors

This study presents the first application of maskless mechanical microfabrication to indium tin oxide (ITO), a brittle transparent conducting oxide, demonstrating its viability as a patterning strategy for transparent device integration. Unlike conventional photolithography or chemical etching, this approach enables direct, lithography-free structuring of transparent conductors through precision mechanical loading. It eliminates resist- and etchant-based steps, thereby reducing the overall process complexity and mitigating potential etch-induced damage and residue contamination. ITO films (∼100 nm thick), deposited via DC magnetron sputtering, were thermally annealed at 300 °C to enhance machinability. Annealing improved optical transmittance at 550 nm (from 85.7% to 88.3%) and reduced sheet resistance by 63.5%, indicating increased film density and crystallinity. Mechanical loading precisely controlled between 4 and 12 mN enables selective material removal, with complete separation of annealed films achieved at 6 mN. To demonstrate applicability to transparent electronics, ZnO thin-film transistors (TFTs) were fabricated using mechanically defined ITO source/drain electrodes, yielding robust n-type operation with an on/off ratio of 2.4 × 10 6 and channel lengths as short as ∼1.3 μm. This work pioneers mechanical microfabrication for transparent conductive oxide (TCO) films and establishes a lithography-free strategy that is extendable to other TCO materials for next-generation display and electronics applications.