晶粒尺度下硅通孔互连的电迁移失效机理研究

In order to study the electromigration failure mechanism of the TSV in the 3D package under the multi-physical loads, an integrated approach that combines accelerated electromigration tests, material properties, multi-physical modeling method will be developed. Considering the multicrystal characteristic of Cu-TSV, an elastoplastic constitutive model of Cu-TSV is developed based on crystal plasticity. An inverse analysis procedure based on genetic algorithm and response surface interpolation is developed to obtain constitutive model parameters of Cu-TSV based on nanoindentation tests. The electromigration test of Cu-TSV is conducted to study the electromigration properties and void evolution, and the influence of grain structure on electromigration diffusion. The electromigration computation model under grain scale is presented based on electromigration evolution equation and elastoplastic constitutive model of Cu-TSV. This electromigration computation model will be used to predict the electromigration void nucleation and propagation. Through the study of this project, the modeling method for electromigration failure analysis under the multi-physical loads will be presented, which will provide the theoretical and numerical basis for the 3D package design and electromigration failure control of TSV.

针对3D封装的硅通孔互连结构，结合电迁移试验、材料力学特性和多物理场建模的集成方法，研究电/热/力等多场耦合下的电迁移失效机理。考虑Cu-TSV的多晶体特性，基于晶体塑性理论发展Cu-TSV弹塑性本构模型；构建基于遗传算法结合响应面插值的材料力学性能参数反演辨识方法，结合纳米压痕实验，确定Cu-TSV材料的本构模型参数；开展电迁移试验，研究Cu-TSV的电迁移特性和微空洞扩展规律，以及微观晶粒结构对电迁移扩散的影响；建立考虑真实微观晶粒结构的Cu-TSV多晶体有限元模型，基于电迁移演化方程和弹塑性本构模型，构建晶粒尺度下的Cu-TSV电迁移计算模型，模拟Cu-TSV微空洞形成和扩展过程，全面理解Cu-TSV的电迁移演化规律和失效机理。通过本课题的研究，建立电迁移失效分析模型，为3D封装设计和TSV互连结构的电迁移失效防治提供理论基础和数值基础。

针对3D封装中硅通孔互连的电迁移失效问题，本项目从晶粒尺度水平上研究了Cu-TSV的力学特性和电迁移特性，揭示了Cu-TSV在电/热/力等多场耦合条件下的电迁移失效机理。基于晶体塑性理论发展了Cu-TSV弹塑性本构模型，结合纳米压痕实验，确定了Cu-TSV材料的本构模型参数，发现Cu-TSV引起的热机械应力差异与Cu-TSV的各向异性密切相关；基于电迁移试验研究了Cu-TSV的电迁移特性和微观晶粒结构对电迁移扩散的影响，研究表明，电迁移后的晶界破坏主要是低结晶度的随机晶界，高密度的焦耳热和Cu原子沿低结晶度晶界的高速扩散加速了Cu-TSV互连的电迁移失效；基于电迁移演化方程和弹塑性本构模型构建了Cu-TSV电迁移计算模型，对3D堆叠封装硅通孔结构进行数值模拟发现，Cu-TSV/微凸点界面处存在“电流拥集”，其电迁移空洞生成率最大，容易引发电迁移失效。另外，应力梯度引起的驱动力对电迁移失效影响较大，不同晶粒结构会造成不同的电迁移失效模式。项目完成了申请书中的研究内容，研究成果将为3D封装的可靠性设计和电迁移预测提供理论和数值分析方法。