叠层芯片塑封器件中分层断裂的研究

【作者】 刘宇；

【导师】 王珺；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2011， 硕士

【摘要】 近年来,随着半导体元器件输入/输出端子数的增加和尺寸的小型化,二维封装已无法满足要求,密度高、功能强、性能好且成本低的3D高密度封装技术逐渐成为主流的封装形式。其中,叠层芯片封装应用最为广泛。它提高了封装效率、电性能和可靠性,同时降低了成本,在数据存储领域得到了广泛的应用。3D高密度封装技术虽然大幅度提高了器件的性能,但同时也引入了许多可靠性问题。一方面,三维封装引入了复杂的多层结构,当器件受热、力学载荷的共同作用时,如何保证不同材料之间界面的完整性不受影响就变得尤为重要。另一方面,生产工艺过程产生的微小缺陷,在热和力学载荷的作用下,这些缺陷会沿着界面开始传播。对于高密度塑封器件来说,界面分层断裂通常是造成其失效的主要原因。本文选取了双层芯片叠层和五层芯片叠层的两种3D高密度封装器件,分别对其进行高温高湿老化实验,利用超声扫描显微镜和SEM等手段,检测经过湿热老化后的器件中出现的界面分层现象,并对不同的分层模式进行观察和分析,总结了三种分层断裂模式并分析了失效的机理。为研究封装中不同材料之间界而的混合断裂,本文设计了一种双相材料样品和一种用于测试双相界面断裂参数的装置,可以对样品施加不同角度的拉力。针对高密度塑封器件中的Epoxy/Cu和Epoxy/PCB界面,进行断裂试验,测量界面断裂发生时的临界拉力值。通过弹性断裂力学分析,基于断裂实验结果可以得到界面断裂能量释放率和混合断裂相位角。通过分析Epoxy/Cu和Epoxy/PCB样品的界面断裂形貌,总结其断裂形式。通过对双层芯片叠层封装器件的高温高湿老化试验,观察到三种界面分层模式,这些分层为正应力作用下的张开型(mode-Ⅰ)断裂和切应力作用下的滑开型(mode-Ⅱ)断裂的混合模式。通过对五层芯片叠层封装器件的高温高湿老化试验,观察到器件底部三层芯片之间的贴片胶层内部会出现空洞,在第一、四、五层芯片底面与贴片胶之间的界面发生分层断裂。针对实际器件失效分析中出现的混合分层断裂,本文设计了一种双相材料样品和一种可以对样品施加不同角度拉力的装置,用于测试界面混合断裂参数。通过对Epoxy/Cu和Epoxy/PCB界面进行断裂试验研究,得到了两种界面在不同断裂相位角下的临界能量释放率,样品断裂模式分析显示不同相位角断裂形式可大致分为三种模式。本文的测试方法加裁角度可调，能够表征大范围相位角的情形，可以应用于电子封装中其它界面断裂参数的表征。更多还原

【Abstract】 In recent years, as the increasing of I/O numbers and miniaturization of size in semiconductor components,2-D packaging is hard to meet the requirements of applications. With higher density, powerful function, good performance and lower costs,3-D high density packaging, in which stacked-die packaging is most widely used, is becoming the major trend of packaging technology. Stacked-die packaging improves efficiency, electrical performance and reliability while reduces costs. It is widely used in data storage field.3-D high density packaging technologies have improved device performance significantly but also introduced many reliability problems. On one hand,3-D packaging introduced complex multilayer structures. The integrity of the interfaces between different materials becomes challenge when the device is subjected to thermal and mechanical loadings. On the other hand, the small defects, which were introduced during fabrication process, may propagate under mechanical and thermal loadings. Interfacial fracture is usually responsible for the failure of high density plastic packaging devices.In this study, two-die stacked and five-die stacked packaging devices were selected and subjected to highly-accelerated temperature and humidity stress test respectively. By using SAM and SEM technology, the interfacial delaminations in the devices were detected after the stress test. Different delamination modes were observed and analyzed. Three delamination fracture modes were summarized and the failure mechanisms were also analyzed. In order to study the interfacial mixed-mode fractures between different materials, a bi-material sample and a new apparatus to characterize the bi-material interfacial fracture were designed. The sample can be loaded in tension in different angles using the new apparatus. For the Epoxy/Cu and Epoxy/PCB interface of high density plastic packaging devices, fracture experiments were carrried out and the critical loading forces were measured when interfacial fracture occurred. The energy release rate of interfacial fracture and mode mixity were obtained based on the experimental results by the elastic fracture analysis. By analyzing interfaciai fracture morphology of Epoxy/Cu and Epoxy/PCB samples, the fracture modes were summarized.According to the hydrothermal stress test of two-die stacked die packaging devices, three interfacial delamination modes were observed. The delaminations exhibit mixed-mode case which includes opening mode (mode-Ⅰ) fracture with normal stress and sliding mode (mode-Ⅱ) fracture with shear stress According to the stress test of five-die stacked die packaging devices, voids were observed in die attached film layer among the bottom three die. Interfacial delaminations fracture between the bottom face of die and die attached film were also observed and analyzed. For the mixed-mode fracture in actual devices’failure analysis, we designed a bi-material sample and a new apparatus to characterize the mixed-mode fracture of the bi-material interface. According to the fracture experiments of Epoxy/Cu and Epoxy/PCB interface, the relationship between critical energy release rate and mode mixity were obtained. The fracture modes of different mode mixity can be divided into three modes according to the samples’fracture modes analysis. The sample can be loaded in tension in different angles. For the method can provide flexible loading angle, it is possible to cover large range of mode mixity cases. The method suggested in this study can be applied for fracture characterization of other interfaces in electronic packaging.更多还原