Study on atomic migration of copper through-silicon-vias with Bosch scallops

Abstract

In three-dimensional integration, atomic migration is a critical challenge for through‑silicon-via (TSV) reliability, especially under high electric current and thermal stress. Meanwhile, Bosch scallops, as the byproduct of Bosch process, can cause stress concentration around them, which further undermines TSV reliability. In this paper, the migration behavior of copper TSVs with Bosch scallops is assessed in an operational scenario using a migration model, while residual stress is taken into account. The possible failure location is studied first, followed by the mechanism of different migration modes. It is shown that the effect of stress on atomic migration manifests itself earlier than that of electric current. Besides, the periodic concentration fluctuation arises along the interface with Bosch scallops, and the amplitude of fluctuation increases as the width of Bosch scallops increases. Furthermore, the impacts of operation temperature and process temperature are investigated to guide the optimization design for the robust TSV structure.