Enhancing Cu Wire-Bonding Reliability by a Cu-Selective Passivation Coating

In response to the critical demand for enhanced reliability in semiconductor device packaging, under the rigorous safety standards of the automotive industry, the need to investigate the corrosion mechanisms of various ions present in epoxy molding compounds (EMCs) becomes essential. This paper highlights the challenges posed by halide-rich environments, particularly under chloride, bromide, fluoride, and, in addition, sulfate and sulfide ions, which may lead to corrosion and wirebond liftoff in copper-aluminum (Cu-Al) bonded devices. Using the immersion corrosion screening and SEM-EDX analysis, the effect of each ion is investigated individually, and the investigation unravels distinct corrosion insights with the chloride, bromide, and fluoride ions. Furthermore, our study reveals that applying passivation coatings significantly reduces the corrosion rate and wire-bond liftoff. The study also shows that sulfide ions can create a protective copper sulfide film, slowing down chloride-induced corrosion. Additionally, this paper explores direct copper-to- copper (Cu-Cu) bonding as an effective alternative to counteract ion-induced corrosion; this exhibits superior reliability by resisting corrosion and liftoff even in severe mixed ion environments. These results highlight the critical role of passivation strategies in improving the reliability of wire-bonded devices in harsh conditions.