[20p-E304-1~13] 16.1 Fundamental properties, evaluation, process and devices in disordered materials

▼ [20p-E304-5] Flexible Solution-processed Metal Oxide Thin Film Transistors Operated at 23 MHz Achieved by a Damage-free Patterning Process

〇(D)Xiaozhu Wei¹, Shohei Kumagai¹, Kotaro Tsuzuku², Akifumi Yamamura¹, Tatsuyuki Makita¹, Mari Sasaki¹, Shun Watanabe¹, Jun Takeya¹ (1.UTokyo., 2.Pi-crystal, Inc.)

Keywords:metal-oxide semiconductors, solution process, high speed

Metal oxide transistors (MOSs) have emerged as a promising platform for thin film transistor (TFT) because of their high uniformity, high electron mobility and satisfactory stability, even in the amorphous phase. Vacuum-based MOS deposition technology has been established for years, but its high initial cost and restricted deposition area limit the large area fabrication. As an alternative solution, solution-processed MOSs have been developed, and attracting more and more attention in recent years, whereas they are still less-used due to lower performance and lack of integration technology compared with vacuum-based type. Here, state-of-the-art solution-processed indium-zinc-oxide (IZO) TFTs with high electron mobility, almost zero threshold voltage, excellent atmospheric stability and compatibility with wet patterning process has been developed. To meet the high-speed operation requirement of advanced applications, we developed a damage-free patterning proces s, using a photoresist that can be processed with aqueous Na₂CO₃ as a mild developer instead of conventional developers such as tetramethylammonium hydroxide. Based on the concept of printed/flexible high speed electronics, solution-processed IZO were fabricated on polyimide substrate. The as-fabricated TFTs with a channel length (L) of 20.0 μm showed high up to 7 cm² V⁻¹ s⁻¹, even with L of 1.7 μm, saturation mobility more than 1 cm² V⁻¹ s⁻¹ and high on-off current ratio up to 10¹⁰ . In addition, potential application to high-speed electronic circuits was demonstrated by cutoff frequency measurements, and a cutoff frequency of 23 MHz was achieved at 10 V. Furthermore, the IZO-based TFTs functioned well under moderate bending stress. Therefore, this technology is expected to open up opportunities for practical high-speed flexible applications.