Enhancement-/Depletion-Mode TiO<sub>2</sub> Thin-Film Transistors via O<sub>2</sub>/N<sub>2</sub> Preannealing
Jie Zhang, Guangyang Lin, Peng Cui, Meng Jia, Zhengxin Li, Lars Gundlach, Yuping Zeng
Abstract
Metal-oxide thin-film transistors (TFTs) promise to enable lightweight and low-power applications, such as ultrathin active matrix displays and low-cost RF identification tags. However, most reported high-performance metal-oxide TFTs contain high-cost indium and gallium elements, leading to constraints in costsensitive application. Herein, we present enhancement/depletion-mode (E-/D-mode) TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TFTs via O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> preannealing of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> channel material prior to device fabrication process. It is found that the O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -annealed TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TFTs exhibit improved performances compared to N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -annealed TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> TFTs, including increased mobility (μ), higher ON-/OFF-current ratio (ION/IOFF), and lower subthreshold swing (SS). This can be attributed to the passivation effects of O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> annealing, which leads to less oxygen vacancies at the channel and channel/oxide interface. On the other hand, the ionized oxygen vacancies result in the increased electron concentration in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -annealed films and, thus, the negative shift of Vth in the TFT performance. This article delivers a possible approach to improve oxide TFT performance by passivation of oxygen vacancies. Furthermore, the controlled annealing process has a great potential in the logic inverter applications when both Eand D-mode TFTs are implemented.