Electromigration Reliability in Ag Lines Printed with Nanoparticle Inks: Implications for Printed Electronics

Despite the appealing technical advantages of printed electronic (PE) technologies, there are very few studies on their technical maturity. Conductive materials are the primary substances used in PEs; therefore, electromigration (EM) is an important reliability aspect of printed conductive patterns. The inevitable porous nature of the printed lines is derived from the nanoparticle-dispersed inks and is a major concern for the EM reliability. Electromigration has been identified as the primary failure mode of interconnect lines used in semiconductor-integrated circuits. Electromigration is a high-current-density-induced mass transport phenomenon that manifests as voids, hillocks, and/or open circuits because of momentum exchange between the conduction electrons and host metal atoms in an external electric field. High temperature and current density accelerate damage, thereby increasing line resistance and reducing circuit lifetime. This study involves investigation of the EM characteristics of Ag lines patterned by using the electrohydrodynamic (EHD) printing technique based on the resistometric and Black theoretical models. It was observed that ion migration was directed toward the cathode for EHD-printed Ag lines, indicating that the electric field-ion interactions (direct force) dominated over the momentum transfer by the electron-ion interactions (wind force). The activation energy for EM in the EHD-printed lines indicates that the surface diffusion is critical to EM failure mechanism. This study is a pioneering work on characterizing the EM performance of the EHD-printed Ag lines and the EM failure mechanism.