GOALI: Understanding and Modeling Electromigration Induced Solder Degradation

技术概述：本研究的目标是(I)更好地了解微结构对锡基焊料中电迁移的驱动力和由此产生的质量扩散过程的影响，以及应力和温度驱动的扩散过程，以及(Ii)开发经过验证的预测模拟工具，以预测给定微结构参数下焊点的寿命。电迁移是一种质量扩散过程，归因于从导电电子到扩散金属原子的动量转移，随着时间的推移，这可能会导致退化和器件故障。随着锡基焊料向锡基焊料的转变和微电子器件的不断小型化，锡基焊料在驱动电迁移的电流密度不断增加的情况下，由于其复杂的行为，可靠性已成为一个主要问题。这项工作涉及到实验、建模和模拟的综合工作。实验工作集中在芯片规模的加速电迁移测试、封装测试结构和详细的材料表征，以考察微结构对退化的影响。这项工作与建模和模拟工作紧密结合在一起，重点是开发一个在颗粒尺度上扩散的模型，考虑电、机械和热驱动力。模型中既考虑了各向异性晶格扩散和晶界扩散，又考虑了力学响应中的晶体塑性。该模型将被实施到一个并行的有限元模拟工具中，该工具将根据实验进行验证，并用于预测典型微结构的失效时间。这项工作是与飞兆半导体的研究人员共同努力的，他们将领导实验工作，参与模拟工具的开发，并将在未来的封装设计过程中使用开发的工具。非技术摘要：这项研究解决了微电子设备中与锡基焊料相关的可靠性问题，这些问题是由于设备变得更小而产生的，目的是在降低成本和功耗的同时提高芯片速度。由于环境问题，锡基焊料现在已经取代了微电子设备中使用的铅基焊料。在现代器件中，当电流由非常小的焊料凸块携带时，在流经焊料的电子的驱动下，发生了一种称为电迁移的过程，即焊料实际上从焊料凸块的一端迁移到另一端。材料的这种迁移可能会导致失效，这是锡基焊料可靠性问题的一个主要来源。通过精心设计和制造微电子设备，可以减缓或完全阻止电迁移。为了做到这一点，必须更好地了解锡基焊料中的电迁移，以及基于这种理解的建模和仿真工具，这是本研究的重点。仙童半导体是一家美国公司和全球半导体解决方案提供商，该公司的研究人员是这项研究的合作者。这个项目将通过开发更准确地预测晶圆级封装的寿命和可靠性所需的知识来影响飞兆及其客户，并将提供一个关键的产品设计工具，以缩短上市时间并在全球市场保持竞争优势。该项目还将培训和装备本科生和研究生，参与材料和过程的基于物理的建模、计算工程和进行基础跨学科研究的新的先进方法的研究，以满足材料加工和设计方面的新的研究需求。

TECHNICAL SUMMARY:The goals of this research are (i) to gain a better understanding of the effect of microstructure on the driving forces and resulting mass diffusion processes associated with electromigration as well as stress and temperature driven diffusion processes in tin-based solder, and (ii) to develop validated predictive simulation tools to predict the lifetime of solder connections for given microstructural parameters. Electromigration is a mass diffusion process attributed to momentum transfer from conducting electrons to diffusing metal atoms, which, over time, may lead to degradation and device failure. With the conversion to tin-based solders and the continued miniaturization of microelectonic devices, reliability has become a major concern due to the complex behavior of tin-based solder subjected to increasing current densities that drive electromigration. This work involves an integrated effort involving experimentation, modeling, and simulation. The experimental work focuses on accelerated electromigration tests on chip scale package test structures and detailed materials characterization to investigate the effect microstructure has on degradation. This effort is closely coupled with the modeling and simulation work focused on developing a model for diffusion at the grain scale, considering the electrical, mechanical, and thermal driving forces. Both anisotropic lattice and grain boundary diffusion will be included in the model, as well as crystal plasticity in the mechanical response. The model will be implemented into a parallel, finite element simulation tool, which will be validated against experiments and used to predict time to failure for representative microstructures. This work is a collaborative effort with researchers at Fairchild Semiconductor, who will lead the experimental work, be involved in the development of simulation tools, and will use the tools developed in their future package design process.NON-TECHNICAL SUMMARY:This research addresses reliability issues associated with tin-based solders in microelectronic devices that are arising as devices become smaller in order to increase chip speed while reducing cost and power consumption. Due to environmental concerns, tin-based solders have now replaced lead-based solders used in microelectronic devices. When an electrical current is carried by a very small solder bump in a modern device, a process called electromigration occurs where the solder material actually migrates from one end of the solder bump to the other, driven by the electrons flowing through the solder. This migration of material may lead to failure, which is a major source of reliability concern in tin-based solders. Electromigration may be slowed or completely arrested through careful design and manufacture of the microelectronic device. In order to do this, a better understanding of electromigration in tin-based solder, and modeling and simulation tools based on that understanding must be developed, which is the focus of this research. Researchers at Fairchild Semiconductor, a US company and global provider of semiconductor solutions, are collaborators on this research. This project will impact Fairchild and its customers by developing the knowledge needed to more accurately predict the life and reliability of wafer level packaging and will provide a critical product design tool to shorten time to market and maintain a competitive advantage in the global market. This project will also train and equip undergraduate and graduate students involved in the research in new advanced methods for physics based modeling of materials and processes, computational engineering, and conducting fundamental interdisciplinary research to address emerging research needs in material processing and design.