Study on transparent oxide thin film transistors with low thermal budget post-treatments

• Main Authors: Teng, Li-Feng, 鄧立峯
• Other Authors: Liu, Po-Tsun
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/78056947262316473209

博士 === 國立交通大學 === 光電工程研究所 === 101 === Recently, transparent metal oxide semiconductor attracts great attention due to the characteristics of high mobility, high transparency, room temperature deposited, and high process compatibility with present solid-state semiconductor technologies. Among several novel oxide semiconductors, amorphous InGaZnO (a-IGZO) thin film received considerable attention for their use in next-generation active matrix liquid crystal display (AMLCD) and active-matrix organic light-emitting diode display (AMOLED) technologies. The sputter-deposited a-IGZO active layer typically requires thermal annealing at around 300℃ for 30 min or longer to achieve a satisfactory device performance and stability. In this study, we presents a novel microwave annealing process for a-IGZO TFT fabrication with low thermal budget process. Microwave heating process can transfer the energy directly to the target materials by absorption of microwave energy throughout the volume of the material. Among its advantages include low thermal budget, rapid heating process, thermal uniformity, suppression of unexpected species diffusion, and selective heating of materials, which is impossible with the typical furnace annealing process, microwave annealing is highly promising for a-IGZO TFT manufacturing. The performance of a-IGZO TFTs with microwave annealing are well competitive with its counterpart with furnace annealing at 450℃ for 1 hour with a carrier mobility of 13.5 cm2/Vs, threshold voltage of 3.28 V, and subthreshold swing of 0.43 V/decade. Although a-IGZO TFTs performed good electrical performance, containing the rare-dispersive elements will increase the cost and be a critical issue for the long-term applications. Therefore, rare elements-free transparent metal oxide semiconductors are considered to be the promising candidates for the next generation display technologies. In this work, we developed a novel rare elements-free oxide semiconductor, amorphous AlZnSnO (a-AZTO), TFT technologies. The band-gap of a-AZTO is larger than 3.6 eV, therefore it shows high transparency in visible light region. We have investigated the effects of SnO2 content on performance of a-AZTO TFTs. Moreover, we employed the plasma treatment to enhance the electrical reliability of a-AZTO TFTs. The experiment results showed that the O2 and N2O plasma could effectively oxidize Sn in back channel of a-AZTO thin film and improve the reliability and stability of a-AZTO TFTs. Furthermore, we decreased the fabrication temperature from 450°C to 350°C by H2 plasma process and remained great performance of a-AZTO TFTs. In the end of this study, a supercritical fluid (SCF) technology is proposed at 150°C to enhance the electrical performance and reliability of a-AZTO TFTs. The SCF provides good liquid-like solvency and high gas-like diffusivity, giving it excellent transport capacity to take the H2O molecules into metal oxide films and terminate the traps in metal oxide films by the oxidization reaction.