Electromigration Investigations of Al-Cu Interconnect Reliability

随着半导体器件的不断缩小，由电迁移引起的金属互连损伤引起的失效已经成为一个重要的问题和担忧。在铝互连线中添加少量铜可以提高其抗电迁移的能力，这一点已经有一段时间了。然而，这种铜的确切作用还不是很清楚。在这项提案中，PI将结合理论建模和各种实验技术来检查和阐明铜在铝合金互连线电迁移诱导破坏的早期阶段所起的作用。此外，PI将开发一种可靠的方法，将加速应力测试的结果外推到正常操作条件。他们工作的具体结果将包括：1.开发电迁移过程的微观模型。对用来外推加速应力测试结果的常规模型的重新评估。确定了“布莱克定律”中正确的温度依赖关系。3.确定了铝-铜金属线中铜和铝扩散的应力诱导激活能的物理意义。测定铜和铝-铜在这些体系中的沉淀迁移率，以及它们在阻止铝扩散中所起的具体作用。卢瑟福背散射测量电流诱导的铜在铝-铜互连线中的扩散。聚焦离子束测量薄膜形态(即颗粒尺寸分布)在电迁移中的作用。这些研究将直接解决微电子工业中的一个现实问题，并将在目前对高应力条件下金属扩散的理解方面取得重大进展。

9975893HeskettWith the continual shrinking of semiconductor devices, failures due to electromigration-induced damage in metal interconnects have become a significant problem and concern. It has been known for some time that the addition of small amounts of copper in aluminum interconnects increases their resistance to electromigration. However, the exact role of this copper is not well understood. In this proposal the PIs will combine theoretical modeling with a variety of experimental techniques to examine and clarify the role of copper in the early stages of electromigration-induced damage of aluminum alloy interconnects. Furthermore the PIs will develop a reliable method for extrapolating the results of accelerated stress tests to normal operating conditions.Specific outcomes of their work will include the following:1. Development of a microscopic model of the electromigration process.2. Reevaluation of the conventional model used to extrapolate the results of accelerated stress tests. (Determination of the correct temperature dependence in "Black's Law".)3. Determination of the physical meaning of the stress-induced activation energy for copper and aluminum diffusion in Al-Cu metal lines.4. Determination of copper and aluminum-copper precipitate mobility in these systems as well as the specific role they play in blocking aluminum diffusion.5. Rutherford Backscattering measurements of the current-induced diffusion of copper in Al-Cu interconnects.6. Focused Ion Beam measurements of the role of film morphology (i.e. grain size distribution) in electromigration.These studies will directly address a real world problem in the microelectronics industry and will result in a significant advance in current understanding of metal diffusion under highly stressed conditions.***