Al₂O₃/HfO₂ nanolaminate dielectric boosting IGZO-based flexible thin-film transistors

• Main Authors: Shi, Qiuwei, Aziz, Izzat, Ciou, Jin-Hao, Wang, Jiangxin, Gao, Dace, Xiong, Jiaqing, Lee, Pooi See
• Other Authors: School of Materials Science and Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Materials; Nanolaminate Dielectric; Thin-Film Transistors
• Online Access: https://hdl.handle.net/10356/164674
• Institution: Nanyang Technological University

Flexible thin-film transistors (TFTs) have attracted wide interest in the development of flexible and wearable displays or sensors. However, the conventional high processing temperatures hinder the preparation of stable and reliable dielectric materials on flexible substrates. Here, we develop a stable laminated Al2O3/HfO2 insulator by atomic layer deposition at a relatively lower temperature of 150 °C. A sputtered amorphous indium-gallium-zinc oxide (IGZO) with the stoichiometry of In0.37Ga0.20Zn0.18O0.25 is used as the active channel material. The flexible TFTs with bottom-gate top-contacted configuration are further fabricated on a flexible polyimide substrate with the Al2O3/HfO2 nanolaminates. Benefited from the unique structural and compositional configuration in the nanolaminates consisting of amorphous Al2O3, crystallized HfO2, and the aluminate Al–Hf–O phase, the as-prepared TFTs present the carrier mobilities of 9.7 cm2 V−1 s−1, ON/OFF ratio of ~ 1.3 × 106, subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec−1, signifying a high-performance flexible TFT, which simultaneously able to withstand the bending radius of 40 mm. The TFTs with nanolaminate insulator possess satisfactory humidity stability and hysteresis behavior in a relative humidity of 60–70%, a temperature of 25–30 °C environment. The yield of IGZO-based TFTs with the nanolaminate insulator reaches 95%.