Addressing Electromigration Challenges in 3D Integrated Circuits

In 1965, Gordon Moore observed that consistent improvements in semiconducting manufacturing technology would correspond to reductions in transistor dimensions, with the number of transistors in an integrated circuit doubling about every two years. “Moore’s law” heralded the information age, but it is reaching its limits as physical and economic constraints now prohibit continued transistor size reductions.

Three-dimensional integrated circuit (3D IC) technology has emerged as the most promising way to sustain Moore’s law trends in IC manufacturing. The technology involves multiple chips stacked vertically on a substrate, which can enable current computational trends and provide supreme performance. Yet, while many chip-stacking techniques have been developed recently, electromigration remains an issue since overheating can occur as a result of the required higher current densities.

Shen et al. provided a systematic and detailed review of studies that outline electromigration failures and the reliability of different components of 3D IC packaging technology.

“We discuss many of the various techniques that have been developed for 3D IC over the last decade, including through-silicon vias (TSVs), micro-bumps, low melting point tin-bismuth solders, redistribution layers, and copper-to-copper direct bonding,” says author Yingxia Liu.

The study also offers potential solutions to some of the issues in the various techniques. For example, while normal large diameter TSVs are typically not problematic in terms of EM, their fabrication can sometimes include defects and dust contamination on the bonding surface, which can reduce their electromigration immunity.

“We hope our paper helps encourage further improvements in the development of 3D IC technology,” says Liu.

With the insight provided by this study, Moore’s law may continue to predict the industry’s trajectory.

Source: “Electromigration in three-dimensional integrated circuits,” by Zesheng Shen, Siyi Jing, Yiyuan Heng, Yifan Yao, K. N. Tu, and Yingxia Liu, Applied Physics Reviews (2023). The article can be accessed at http://doi.org/10.1063/5.0139658 .