周期性液氮冲击中锑化铟焦平面探测器结构可靠性研究

Both InSb chip fracture and indium bump interconnection failure appearing in InSb infrared focal plane arrays (IRFPAs) under liquid nitrogen shock cycles, limit its long-term applications. In the thermal cycling reliability of IRFPAs, several approaches for solving the thermal mismatch existed in IRFPAs are ambiguously described. But the evaluation criterion, the quantitative analysis and the optimization are almost not mentioned. So in this project, focusing on the 128×128 InSb IRFPAs, we will research the structural reliability of InSb IRFPAs in three aspects. 1. Basing on the proposed three dimensional equivalent modeling, taking account of the curing process of undefill, employing the viscoelastics characteristic of underfill and the viscoplastic characteristics of indium bump, we will create the structural modeling of InSb IRFPAs. Furthermore, we will adopt the deformation photographs of InSb IRFPAs, which are taken at 300 K, 77 K and 300K in sequential, respectively, to verify the accuracy of the modeling for InSb IRFPAs. 2. Analyzing the interaction and its deformation rule among the layered InSb IRFPAs, which appear in both the process of the underfill curing and the process of InSb chip thinning, we will explore the causes, which cause the InSb chip fracture and indium bump interconnection failure in the liquid nitrogen shock cycles, and infer the evaluation criterion, which is emplyed to solve the thermal mismatch existing in InSb IRFPAs. 3. expanding the created three dimentional modeling of InSb IRFPAs in the encapsulation of InSb IRFPAs assembly, we will explore the deformation rule of InSb chip depending on the balanced composite structure, which is attatched to the bottom surface of silicon readout integrated circuit, and predict the lifetime of InSb IRFPAs assembly enduring liquid nitrogen shock cycles without failure. All these findings will provide the theory for analyzing the structural design and the structural relibility of InSb IRFPAs, or other devices with similar structure.

周期性液氮冲击中出现的光敏元芯片碎裂和铟柱互连失效制约着红外焦平面探测器的长期应用。在焦平面探测器耐冲击报导中，虽有热失配解决方案的零星描述，但其评价标准尚未确立，定量分析及优化方向鲜有提及。课题以128×128 InSb探测器为研究对象，分3个方面进行研究。1.基于等效建模思想，考虑底充胶黏弹性和铟柱黏塑性形变特征，建立能描述探测器全工艺流程的三维结构模型，以连续三温度点（液氮冲击前300K、冲击后77K、升温至300K）测量的形变幅度及分布特征验证模型正确性；2.分析液氮冲击中层状材料之间的相互作用和形变规律，探讨器件失效诱因，明确芯片减薄和铟柱结构优化对InSb芯片形变的影响程度，提取出热失配解决方案的评价标准；3.建立组件封装模型，定量分析平衡复合物结构对InSb芯片形变的影响程度及作用规律，建立模型预测组件耐冲击次数。这为InSb焦平面探测器及类似结构器件的可靠性设计提供指导。

红外焦平面探测器是红外探测系统的关键核心部件，其在周期性液氮冲击中容易出现的光敏元芯片碎裂、铟柱互连局部失效、或边沿局部开裂等失效现象制约着其使用寿命。为揭示InSb红外焦平面探测器组件中典型失效模式的失效机理、失效诱因，找出相应的解决方案，解决措施，理清背后的理论支撑依据，课题以128×128 InSb探测器为研究对象，进行了3个方面的研究。1.基于提出的等效建模思想，考虑底充胶固化过程，铟柱黏塑性形变特征，建立了能够描述探测器全工艺流程的三维结构模型，模拟结果得到了实验验证，表明项目采用的建模方法切实可行，材料模型贴近生产实际，法线方向应变标准的采用正确，合适；2.针对典型失效模式，经系统分析后，我们认为：光敏元芯片碎裂源于热失配效应在InSb芯片中引入的张应力，主要分布于探测器中心区域；N电极附近的局部分层源于自由边效应在InSb芯片和底充胶界面处的剪切应力分量，该剪切应力分量也可引起铟柱局部互连失效；边沿开裂源于底充胶与硅读出电路界面处的剥离应力。此外明确了芯片减薄过程中探测器表面形变与芯片厚度的依赖关系，铟柱直径挑选依据。3.建立了探测器组件的结构分析模型，分析了平衡复合物结构对热失配应力的作用规律，评价了平衡复合物结构在消除热失配应力方面的效果，及其对器件失效模式的影响。这些研究结果为InSb焦平面探测器及类似结构器件的可靠性设计、优化提供了理论指导和评价标准，为后续器件使用寿命的延长提供了方向。