The electromigration study of thin-film structured Sn3.5Ag and Ag using continuous observation and reliability enhancement approach

Abstract

Thin-film materials have been widely used in advanced technologies because of their flexible structure and superior working performance. However, the reliability of thin films that are employed in electronic devices has become an increasing concern. In this study, thin-film-structured Ag and Sn3.5Ag samples were prepared to observe their reliability behaviors during electromigration (EM) tests at low and high current densities. Under a low current density (8.89 × 104 A/cm2), the Ag stripe shows good resistance to EM, and microstructural changes are only observed in the Sn3.5Ag sample. In the high current density test (8.89 × 105 A/cm2), the microstructures of both samples undergo a significant change; however, the Ag sample shows superior performance than the Sn3.5Ag sample in terms of total experimental duration. Ag exhibits a better EM resistivity than Sn3.5Ag owing to the difference in EM activation energy causing the difference in atomic diffusivity. Moreover, it shows that pre-heating is an efficient method to enhance the EM resistivity of thin-film metals. The findings of this study provide a criterion for manufacturers to select suitable thin-film metals as far as EM is concerned and how to minimize the impact due to EM.