Improving Crystalline Orientation by Splitting IGO Active Layer into 2 µm Unit Width for High‐Performance Thin‐Film Transistors with Excellent Stability

ABSTRACT We demonstrate significant improvement in both the electrical performance and stability of polycrystalline indium‐gallium oxide (poly‐IGO) thin‐film transistors (TFTs) by employing an active split structure. Amorphous IGO (a‐IGO) films are patterned into unit‐widths of 2, 4, 10, and 20 µm and crystallized at 450°C on a hot plate. The crystalline structure depends on positions, with edge regions comprising more single‐crystal‐like grains than the center regions. Subsequent N 2 O plasma treatment and post‐N 2 O annealing effectively suppress oxygen vacancies and hydroxyl‐related defects, with a stronger effect in the smaller unit width IGO layer. The TFT with the 2 µm unit width exhibits field‐effect mobility (µ FE ) of 68.9 cm 2 V −1 s −1 and threshold voltage shift (ΔV TH ) of +0.1V under positive bias temperature stress (PBTS), whereas the 20 µm device shows µ FE of 43.2 cm 2 V −1 s −1 and a higher ΔV TH of +1.3V. A 19‐stage ring‐oscillator integrating active split TFTs demonstrates an oscillator frequency of 3.79 MHz at a supply voltage of 15 V. These results demonstrate that splitting the a‐IGO layer and crystallizing it enables high‐mobility, defect‐suppressed poly‐IGO, leading to high‐performance and stable oxide TFTs for display backplanes.