原子层尺度可控的InGaZnO薄膜和异质结构制备及其应用研究

The transparent indium gallium zinc oxide (IGZO) film is a promising wide bandgap semiconducting oxide for high quality thin-film transistors (TFTs) in modern display devices owing to their technologically important features, including their high electron mobility, large Ion/Ioff ratio, high transparency, etc. Nevertheless, systematic composition engineering of this material, high-k dielectrics/IGZO interfacial controlling, and the stability of IGZO-based TFTs still remain incomplete. To improve the material and electrical properties, atomic layer deposition (ALD) of IGZO films has been first proposed in this project. Through modulating the cation ratio, the microstructural, compositional, and physical properties will be investigated to optimize the optical and electrical properties of IGZO films. High-k dielectrics such as HfO2, HfAlO, and HfO2/Al2O3 will also be grown by ALD in the same chamber, which is selected as the insulator for the transistor. The interfacial properties of high-k/IGZO heterostructure will be controlled by in-situ method, which is a key point to improve the electrical properties of IGZO-TFTs. In addition, the effect of rapid thermal annealing or plasma treatments on the structural, compositional, optical, and electrical stability of IGZO films and the characteristics of TFTs will be well understood. The physical mechanism and the influencing factors in determining electrical properties of IGZO films will be achieved by optimizing the ALD growth process, high-k dielectrics, and fabrication conditions. The experimental and theoretical results obtained in this work will provide a strong basis for improving the device characteristics of IGZO-TFTs.

铟镓锌氧 (IGZO)薄膜具有可低温淀积、透明性好、导电率高及均匀度佳等特点，是透明电子学领域新兴的宽禁带半导体材料。但多元IGZO薄膜在组分精确控制及晶体管(TFT)应用等方面，仍存在诸多问题。本项目(1)利用原子层淀积(ALD)方法精确的组分控制能力，制备原子层级可控的多元IGZO薄膜，对其生长规律、制备条件进行深入研究，探索元素组分、缺陷与薄膜光电特性的内在规律，获得高性能IGZO薄膜制备的最佳工艺；(2)ALD高K栅介质的工艺优化及其与IGZO异质结构的界面特性调控，通过原位测试分析手段，筛选出适合于IGZO-TFT的高K栅介质及其制备方法；(3) 探究改善高K栅介质/IGZO-TFT运行稳定性的方法，探明快速热退火条件和等离子处理方法对界面、表面修补作用的物理机制。通过优化的IGZO组分比、高K栅介质和后处理工艺，为进一步提高IGZO-TFT器件特性提供实验参数和理论依据。

宽禁带的IGZO薄膜具备较高的迁移率、较低的制备温度、很好的均一性、可见光全透明等优点，并且相应的薄膜晶体管（TFT）器件拥有低的阈值电压、高的电流开关比等良好的器件特性，有着巨大的应用潜力，这也对薄膜材料本身的物理和化学性能提出了更高了要求，面临着诸多技术性难题。本研究项目针对新型的IGZO材料及其TFT器件，利用近几年发展起来的优秀薄膜生长技术—原子层淀积（ALD）来制备IGZO薄膜。取得的主要成果有：（1）实现了在原子层尺度上高质量多元ZnO薄膜的可控制备，掌握相应的组分精确调控的方法，并获取了相应的工艺参数、生长规律和薄膜质量控制因素。为后续氧化物半导体相关器件的器件奠定了坚实的基础。（2）优化了ALD生长HfO2、Al2O3、HfAlO和HfSiO以及TiAlO等高k介质的生长工艺，筛选出了HfO2、Al2O3和HfAlO等适合IGZO-TFT器件的高k栅介质，并优化出相应的制备工艺参数。在此基础上，提出了N掺杂的IGZO/α-IGZO/N掺杂的IGZO的多层沟道结构来提高器件的迁移率和稳定性。（3）掌握了提高IGZO-TFT器件性能的快速热退火工艺、微波退火工艺以及表面钝化等关键技术，通过不同的栅介质和沟通层揭示影响了ZnO基TFT器件的界面态形成机理，阐明了器件运行时的物理机制。（4）探索了ZnO、IGZO等氧化物半导体材料与新型的高k介质以及半导体Si之间的能带对准情况研究，为厘清基于IGZO薄膜晶体管的电学特性影响因素和分析其内在物理机制，提供理论参考。同时还研究了其他基于ZnO基半导体的纳米器件和特性。项目研究成果，为进一步改善IGZO薄膜的TFT器件特性提供了实验和理论依据。

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