Interfacial Creep in Thin Film Interconnect Structures in Micro-Systems

在多组分微系统的许多应用中，界面承受较大的剪应力和较高的相对应温度。这使得扩散调节的滑动过程(界面蠕变)能够在界面处运行。此外，微系统中的薄膜互连结构通常携带大电流密度，从而驱动电迁移。随着互连尺寸的缩小，界面成为电迁移过程中扩散的主要路径，由于施加的应力和电迁移，可能导致界面扩散通量之间的显著相互作用。随着微电子、MEMS和功能纳米复合材料中多材料组装的纳米级小型化趋势的出现，以及这些组装中界面面积的爆炸性增长，界面滑移可能会变得越来越突出，严重影响元件的性能和可靠性。在此，提出了一种综合的实验和分析工作，以获得薄膜-衬底界面在热机械和电载荷作用下的界面蠕变的基本力学观点。这项工作将结合蠕变测试，在有和没有施加电流的情况下，界面表征，本构模型和微电子设备结构的实验/分析研究。这项研究将突出应力和电流在促进/抑制界面滑动方面的相互作用。非技术性：这项工作的更广泛影响与其对整个微/纳米系统行业的技术相关性有关，因为它揭示了一种新现象，该现象可能会在未来成为一系列广泛组件的性能限制。在整个项目中，PI和他的团队将与行业密切合作，确定/解决新出现的相关问题，并让学生接触到行业。除了培训研究生和博士后，PI和他的团队还将通过当地的一个丰富计划与高中生合作，让他们接触到与微/纳米系统相关的材料研究和新出现的问题。还将向初中/高中科学教师提供暑期实习，目的是帮助他们开发与本研究一般领域相关的课程模块。

TECHNICAL In many applications of multi-component micro-systems, interfaces are subjected to large shear stresses and high homologous temperatures. This enables diffusionally accommodated sliding processes (interfacial creep) to operate at the interface. Furthermore, thin film interconnect structures in micro-systems often carry large electric current densities, which drive electromigration. As interconnect dimensions shrink, interfaces become the primary path for diffusion during electromigration, potentially leading to significant interactions between interfacial diffusive fluxes due to applied stress and electromigration. With the emerging trend towards nano-scale miniaturization of multi-material assemblies in microelectronics, MEMS and functional nano-composites, and the commensurately explosive growth in interfacial area inside these assemblies, interfacial sliding is likely to become increasingly prominent, severely impacting the performance and reliability of the component. Here, a comprehensive experimental and analytical effort is proposed in order to obtain fundamental mechanistic insight into interfacial creep at thin film-substrate interfaces under thermomechanical and electrical loads. The effort will combine creep testing with and without applied electrical current, interfacial characterization, constitutive modeling and experimental/analytical investigations of microelectronic device structures. This study will highlight the interaction between stress and electric current in promoting/inhibiting interfacial sliding. NON-TECHNICAL: The broader impact of the work is related to its technological relevance to the entire micro/nano-systems industry by bringing to light a new phenomenon which may become performance limiting in a wide array of components in the future. Throughout the project, the PI and his group will work closely with the industry to identify/address issues of emerging relevance, and expose students to the industry. In addition to training graduate students and post-docs, the PI and his group will work with high school students through a local enrichment program to expose them to materials research and emerging issues related to micro/nano-systems. Summer internships will also be offered to middle/high school science teachers with the aim of helping them develop lesson modules relevant to the general area of this research.