Electromigration behavior of silver thin film fabricated by electron-beam physical vapor deposition

Abstract

Electromigration (EM) is considered as a serious issue that threatens the reliability of electronic packaging. For the long-term reliability of the application of pure silver thin films, it is important to investigate its EM effect; however, there are limited studies focused on this aspect. In this study, the EM of a silver thin film deposited on a glass substrate was examined at a current density of 8.89 × 105 A/cm2 and room temperature of 15 °C. During the EM test, the new phenomenon of the thin-thread silver structures with a unique direction was noted. To explain this, finite element analysis was applied to simulate the temperature and direction of the current flow. The effect of thermal and stress migration could be ignored in this experiment based on the temperature distribution results. The electron wind force played an important role in the formation of the thin-thread silver with nucleation structure following the direction and strength of the electron flow. By analyzing the failure location, melting was observed near the cathode since the generation of the thin-thread silver decreased the contact area for passing current. Finally, reducing the grain boundaries was proposed as an approach to improve the reliability of the pure silver sample, which is paramount for manufactures.