HfO2/ZnO superlattice channel for transparent thin-film transistors fabricated by atomic layer deposition

• Main Authors: Tsung-Han Liu, 劉宗翰
• Other Authors: 賴聰賢
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/983j7f

碩士 === 國立中興大學 === 光電工程研究所 === 107 === This thesis uses Atomic Layer Deposition (ALD) to deposit multiple oxide layers. By using ZnO and HfO2 superlattice thin-film transistors, we expect two-dimensional electron gas that exists in the lattice structure can increase the mobility of transistors. In addition, we add passivation layers (HfO2), which is expected to improve the stability of transistors. The thin-film was annealed at the 200⁰C、350⁰C、450⁰C and 600⁰C with RTA. To analyze its properties including the crystallinity, carrier concentration, resistivity, and mobility, are performed measurment by XRD, Hall Effect, and transmittance. The device process was begun by using a shadow mask to define the channel length and width of transistors, and then evaporated Au/Ge as electrodes by using thermal evaporator. There are two main parts in the measurement analysis. First, we compare the electrical properties of HZO TFT and ZnO TFT with different channel length and width through the I-V electrical measurement, and then change the different HfO2/ZnO thickness ratio and different annealing temperatures. The second part is to analyze the stability of TFTs with different thickness ratios. In this experiment, we made four TFT structures, which are HfO2/ZnO thickness ratios of 1:10, 1:5, 1:2 and single-layer ZnO. After measurement and analysis, we can find that HfO2:ZnO = 1:10 shows well TFT performance, its mobility = 24.5 cm2/V-s, On/Off ratio = 1.1 x106, subthreshold swing = 2.59 V/decade, under stress test, HfO2: ZnO = 1:10 Vth shift is only 0.8 V, which is better than single-layer ZnO.