【作者】 黄建国；

【导师】 王向展；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2015， 硕士

【摘要】 随着航空航天技术的飞速发展,越来越多的由CMOS器件和CMOS集成电路构成的电子设备运用于航天技术当中,但在空间环境当中,存在着大量的空间粒子和射线,会增加电子设备失效的风险。为提高电子设备的使用寿命和可靠性能,对抗辐照技术进行更加深入的研究变得异常的重要。本文以NMOS晶体管在电离辐照总剂量效应(Total Ionizing Dose,TID)下的辐照缺陷和电流模型为研究课题,具体研究了辐照缺陷(固定电荷和界面态陷阱)和电流模型的建立方法,并对模型进行了验证与分析。本文基于总剂量辐照理论,分析了总剂量辐照效应对NMOS晶体管电学特性的影响。根据电路的实际应用情况,对栅极零偏置电压条件下晶体管的辐照性能模型进行研究,设计出了零偏置条件下的辐照实验方案。实验分别采用环形栅和普通栅结构以及不同栅宽的NMOS管进行总剂量辐照。通过对实验结果的深入分析,得出总剂量、栅极结构、宽长比对晶体管的亚阈值特性和输出特性曲线的影响。并采用McWhorter-Winokur的方法对辐照产生的缺陷进行了提取,而此方法提取不同宽度的NMOS晶体管的辐照缺陷时,其结果与宽度存在相关性,通过对提取原理的分析,本文提出了选取基本宽度作为提取的标准以方便辐照电流模型的建立。本文首先采用了总剂量辐照效应下,MIS(Mental-Insulator-Semiconductor)结构的辐照缺陷的建模方法,并对模型中电势的边界条件进行了详细的讨论,即使栅极处在零偏置条件下,由于不同材料之间存在功函数差,仍然会在氧化层中产生附加电场,并影响到整个辐照缺陷的形成,并在模型中加以考虑。然后通过MATLAB程序对模型进行数值求解,并讨论了不同栅极偏压,总剂量,氧化层厚度对固定电荷面密度和界面态密度以及阈值电压的影响。另外,实验所采用的LOCOS(Local Oxidation of Silicon)工艺普通栅NMOS管,辐照后主要关态泄漏电流存在于鸟嘴区,而此处氧化层的厚度在不断变化,将给辐照电流的计算带来一定的复杂度。基于此,本文提出将鸟嘴区的辐照缺陷等效到栅氧化层中的方法,以减少对电流计算的复杂程度。最后本文采用提出的辐照缺陷模型和缺陷等效模型以及辐照电流模型的求解结果对文献中的实验数据和本文的实验数据进行了很好的拟合。更多还原

【Abstract】 With the aerospace technology developed rapidly, more and more electronic equipment composed of CMOS device and CMOS integrated circuits used in the aerospace engineering, however, there are lots of space articles and rays in the aerospace environment will increase the failure risk of electronic equipment. To improve the reliability of the electronic equipment, the anti-radiation studies become very important.In this article, The NMOSFET’s models of defects(fixed charge and interface states) and currents induced by Total Ionizing Dose(TID) radiation when the gate biased on zero voltage were the study object. The main study was to find the approach to build the models and demonstrate the validity and accuracy of the models.According to radiation theory, the electrical properties of NMOSFET in the Total Ionizing Dose environment and properties with different gate voltage biased were analyzed. In according with integrated circuits applied situation, the radiation model with the condition of zero gate voltage biased is studied, and proposed the related radiation experiment.The radiation experiment was carried out on both conventional and enclosed-gate n-MOSFET with different gate width and total radiation dose. And the experimental data was analyzed to obtain the influence of transfer and output characteristic with different total radiation dose, gate structure and gate with. The densities of charge and interface states were extracted via McWhorter-Winokur’s method. However the extracted results were related with gate width and the reason was analyzed, and proposed the base width to standardize the extracted results to build the current model more convenient.The model of fixed charge and interface states was established with mental-insulator- semiconductor(MIS) structure in the total ionizing dose environment, and the boundary conditions of the model was studied in detail. Even though the gate without external voltage, the electric field also existed in the oxide, it was caused by the work function difference of mental and Si and considered in the model. And then the numerical solutions was obtained by the MATLAB program, the influence of fixed charge and interface states with different gate biased, total dose and oxide thickness was analyzed. In addition, the leakage current was main existed in the bird’s beak region of conventional MOSFET fabricated with LOCOS isolation process was radiated. However, the oxide thickness of bird’s beak region was changed with gate width; it will bring more complicated to calculated radiation current, therefore, the A new approach which takes the trapped charges in the bird’s beak as equivalent charges in the gate oxide was proposed to simplify the calculation of radiation current. At last, the numerical solutions of charge model and equivalent model agree well with other paper and ours experiment data.更多还原