Lin Yuan-Yu, Hsu Che-Chen, Tseng Ming-Hung, Shyue Jing-Jong, Tsai Feng-Yu
Department of Materials Science and Engineering, National Taiwan University , 1, Section 4, Roosevelt Road, Taipei 106, Taiwan, R.O.C.
Research Center for Applied Science, Academia Sinica , Taipei 115, Taiwan, R. O. C.
ACS Appl Mater Interfaces. 2015 Oct 14;7(40):22610-7. doi: 10.1021/acsami.5b07278. Epub 2015 Oct 5.
Passivation is a challenging issue for the oxide thin-film transistor (TFT) technologies because it requires prolonged high-temperature annealing treatments to remedy defects produced in the process, which greatly limits its manufacturability as well as its compatibility with temperature-sensitive materials such as flexible plastic substrates. This study investigates the defect-formation mechanisms incurred by atomic layer deposition (ALD) passivation processes on ZnO TFTs, based on which we demonstrate for the first time degradation-free passivation of ZnO TFTs by a TiO2/Al2O3 nanolaminated (TAO) film deposited by a low-temperature (110 °C) ALD process. By combining the TAO passivation film with ALD dielectric and channel layers into an integrated low-temperature ALD process, we successfully fabricate flexible ZnO TFTs on plastics. Thanks to the exceptional gas-barrier property of the TAO film (water vapor transmission rate (WVTR)<10(-6) g m(-2) day(-1)) as well as the defect-free nature of the ALD dielectric and ZnO channel layers, the TFTs exhibit excellent device performance with high stability and flexibility: field-effect mobility>20 cm2 V(-1) s(-1), subthreshold swing<0.4 V decade(-1) after extended bias-stressing (>10,000 s), air-storage (>1200 h), and bending (1.3 cm radius for 1000 times).
对于氧化物薄膜晶体管（TFT）技术而言，钝化是一个具有挑战性的问题，因为它需要长时间的高温退火处理来修复工艺过程中产生的缺陷，这极大地限制了其可制造性以及与诸如柔性塑料基板等对温度敏感材料的兼容性。本研究调查了原子层沉积（ALD）钝化工艺在ZnO TFT上引发的缺陷形成机制，基于此，我们首次展示了通过低温（110°C）ALD工艺沉积的TiO2/Al2O3纳米层状（TAO）薄膜对ZnO TFT进行无退化钝化。通过将TAO钝化膜与ALD介电层和沟道层结合成一个集成的低温ALD工艺，我们成功地在塑料上制造了柔性ZnO TFT。得益于TAO膜出色的气体阻隔性能（水蒸气透过率（WVTR）<10(-6) g m(-2) day(-1)）以及ALD介电层和ZnO沟道层的无缺陷特性，这些TFT表现出具有高稳定性和柔韧性的优异器件性能：场效应迁移率>20 cm2 V(-1) s(-1)，在长时间偏置应力（>10,000 s）、空气存储（>1200 h）和弯曲（半径1.3 cm，1000次）后，亚阈值摆幅<0.4 V decade(-1)。
