Understanding the Effect of Ordered Twinning on Electromigration Failure in Advanced Metallic Interconnects

非技术总结：电迁移是一种发生在半导体工业和可穿戴和柔性电子等新技术中使用的金属中的故障。在这种类型的故障中，用于导电的小金属线（所谓的互连线）产生微小的空隙，并最终由于大量的电流而断裂，导致电子设备的整体故障。众所周知，电迁移是由金属材料的结构控制的，特别是其原子的排列方式。在典型的金属中，某些区域（称为晶界）在原子排列中显示出很大程度的无序，这是已知的，容易导致电迁移失败。在这个项目中，将研究具有有序原子结构（所谓的孪晶界）的新型纳米级金属材料，从而具有很高的防止电迁移的潜力。电迁移是电子工业发展的一个障碍，阻碍了进一步的小型化和更高的可靠性。就新的可穿戴和柔性电子技术而言，它限制了更广泛的大众市场应用。本研究中出现的对双边界金属电迁移的理解将有助于消除这些困难，并为互连设计提供新的方向。此外，研究生、本科生和高中生将获得指导和研究机会。研究生将指导参与该项目的本科生，以及通过UTD纳米探索者计划在PI实验室主持的高中生。通过做与这个项目相关的有意义的研究，高中生将受到启发，从事STEM领域的职业。技术总结：电迁移是一种扩散过程，在高电流密度的情况下，电子在导体中移动，促进金属晶格中原子的扩散，导致空洞和最终失效。扩散取决于微观结构；事实上，已知晶界由于其松散堆积的结构而有利于电迁移。另一方面，由于其有序的原子结构，孪晶界有望将扩散速度降低几个数量级。提出的研究旨在研究具有明确定义和可重复的孪晶边界的材料的潜在有益作用，因为相互连接具有增加的电迁移阻力。拟议的研究计划本质上是实验性的，旨在通过进行高电流密度和控制温度会导致失败的测试来深入了解孪生互连的电迁移行为。将进行高通量非原位电测试（用于统计显着的失效量化）和原位透射电子显微镜（TEM）测试的组合，以了解电迁移过程中孪晶微观结构的演变。本研究的目的是：i)量化孪生互连中的电迁移参数；ii)对原位瞬变电磁法电迁移行为进行表征，获得结构-性能关系；iii)比较孪生互连的电迁移性能与目前电子工业中使用的互连的公开数据。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical summary: Electromigration is a type of failure that occurs in metals used both in the semiconductor industry and in new technologies such as wearable and flexible electronics. In this type of failure, small metallic lines used to conduct electricity (so-called interconnects) develop microscopic voids and ultimately break due to a large amount of electrical current, leading to the overall failure of the electronic device. It is known that electromigration is controlled by the structure of the metallic material, in particular how its atoms are arranged. In typical metals, certain regions (called grain boundaries) display large levels of disorder in the atomic arrangement, and this is known to facilitate failure by electromigration. In this project, new kinds of nanoscale metallic materials with well-ordered atomic structures (so-called twin boundaries), and thus a high potential to prevent electromigration, will be studied. Electromigration is a barrier for the progress of the electronic industry, hampering further miniaturization and greater reliability. In the case of the new wearable and flexible electronic technologies, it limits broader mass-market applications. The understanding of electromigration in metals with twin boundaries emerging from this research will contribute to remove these difficulties, and enable new directions in the design of interconnects. Furthermore, mentoring and research opportunities for graduate, undergraduate and high school students will be enabled by this grant. The graduate students will engage in mentoring of undergraduates participating in the project, and of high-school students hosted in the PI lab through the Nanoexplorers program at UTD. By doing meaningful research related to this project, the high school students will be inspired to pursue careers in STEM. Technical summary: Electromigration is a diffusion process where electrons travelling in a conductor in a high-current-density scenario- promote the diffusion of atoms in the metallic lattice, leading to voids and eventually failure. Diffusion depends on the microstructure; in fact, grain boundaries are known to facilitate electromigration due to their loosely-packed structure. Twin boundaries, on the other hand, promise to slow diffusion by several orders of magnitude due to their ordered atomic structure. The proposed research aims to investigate the potentially-beneficial role of materials with well-defined and repeatable twin boundaries, as interconnects with increased resistance to electromigration. The proposed research program is experimental in nature, and aims to gain insights into the electromigration behavior of twinned interconnects by conducting tests where high current densities and controlled temperatures will cause failure. A combination of high-throughput ex-situ electrical tests for statistically-significant quantification of failure, and in-situ transmission electron microscopy (TEM) tests to understand the evolution of the twinned microstructure during electromigration, will be conducted. The objectives of the research are: i) To quantify the electromigration parameters in twinned interconnects; ii) To characterize in-situ TEM the electromigration behavior to obtain structure-property relations; and iii) to compare the electromigration performance of twinned interconnects with respect to published data from interconnects currently used in the electronic industry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.