铟锌氧化物薄膜晶体管的低频噪声特性及其可靠性应用

As switching elements and driving circuits, indium zinc oxide thin film transistors (IZO TFT) have been widely used in the active matrix organic light emitting diode. Through combination of low frequency noise with IZO TFTs, the dominant noise source and mechanism is determined, the relationship between low frequency noise and reliability have been studied, and a newly characterization method of defects in the devices is proposed which can be used in the selection of reliable devices and as a diagnostic and prediction tool of device quality and reliability. .Firstly, the properties of low frequency noise in the IZO TFTs have been investigated, the physical explanation behind the empirical mobility fluctuation model is determined. By considering of density of states (DOS), parasitical source/drain junction resistance, self-heating effects and current crowding effects, the physical and analytical model based on surface potential is proposed. Secondly, the extraction method for defects in the channel and oxide trapped charges are proposed based on the measurement of low frequency noise and then verified by using of I-V & C-V and material characterization method. In the last, variations of defects before and after stress are measured while the degradation mechanism are analysis and thus a theoretical model are proposed, which is expected to provide a diagnostic and prediction tool in reliability physics for IZO TFTs. From the characterization of defects based on low frequency noise, the effects of manufacture process, device structure and channel material on the device properties have been studied based on average Hooge’s parameter.

作为开关元件与驱动电路，铟锌氧化物薄膜晶体管在AMOLED领域得到广泛应用。本项目拟研究IZO TFT低频噪声的来源与物理机制，明确低频噪声与IZO TFT可靠性的相关性，提出IZO TFT基于低频噪声的缺陷表征、工艺评价与可靠器件无损筛选方法。.首先，针对器件低频噪声来源开展实验研究，明确迁移率随机涨落现象的物理机制；考虑缺陷态密度、源/漏结寄生电阻、自热、电流拥挤等二级效应，基于表面势建立IZO TFT低频噪声的物理与解析模型，并将其嵌入仿真器。随后，构建器件有源层内缺陷、氧化层固定电荷基于低频噪声的提取与表征方法，并采用I-V法、电导法与材料表征方法进行验证。最后，基于低频噪声提取IZO TFT中缺陷态在应力实验前后的变化，揭示器件电性能的退化规律并构建相关物理模型，形成基于低频噪声的可靠性表征与评价方法，基于Hooge因子讨论制备工艺、器件结构、沟道材料对器件本征电学性能的影响。

铟锌氧化物薄膜晶体管（IZO TFT）是AMOLED的核心器件，其可靠性将直接影响系统的稳定与性能。作为一种新型可靠性无损电学表征方法，低频噪声可反映半导体材料与器件中的潜在缺陷，具有极高的应用价值。.本项目针对IZO TFT等器件，在研究器件低频噪声来源、明确低频噪声影响机制、建立低频噪声物理模型的基础上，构建器件缺陷态的表征方法，并将其应用于器件可靠性评价与筛选中。主要完成内容包括：.1. IZO薄膜晶体管中低频噪声的来源、影响机制与模型研究.针对IZO TFT及其相关器件的低频噪声特性展开实验与理论研究，系统研究了以上器件低频噪声的来源与主导机制，基于ΔN-Δμ模型提取了器件的平带电压噪声功率谱密度、霍格因子等参数；此外，明确接触电阻、短沟效应对器件低频噪声特性的影响，基于低频噪声分析器件载流子输运通道的变化。初步构建IZO TFT低频噪声特性的物理与解析模型，并首次分析Bsim模型对IZO TFT的适用性。.2. IZO薄膜晶体管中缺陷态的表征方法与验证.针对IZO TFT及其相关器件，基于I-V曲线构建器件表面势的提取方法。基于ΔN-Δμ模型，基于低频噪声提取器件局域态的分布，并结合表面势分析器件局域态随能级的变化。基于隧穿因子，分析器件绝缘层内缺陷态随空间的分布。基于变频C-V法，提取器件沟道内局域态随能级的分布，并与基于低频噪声所提取的数据进行对比验证。.3. IZO薄膜晶体管低频噪声与可靠性之间的相关性.本项目针对IZO TFT及其相关器件的可靠性进行实验与仿真研究，针对常规应力（电应力、光电应力、温度、氢环境等）与极端环境应力（辐射、静电等）下IZO TFT器件I-V与低频噪声特性的变化开展测试与分析，通过低频噪声定量分析与判断器件内部缺陷态随空间与能级的变化。在国际上首次报道IZO TFT在静电与液氦低温环境下器件低频噪声特性的变化。..项目执行期间，培养硕士生五名、博士研究生一名，发表SCI索引期刊论文二十篇，有八篇论文发表在电子器件国际顶尖期刊IEEE Electron Device Letters、IEEE Trans. Electron Device和IEEE Journal of the Electron Device Society上；获得国防科技进步一等奖一项。