A multi-method approach to assess ionic migration and its impact on the reliability of polyimide coatings in microelectronic applications

The reliable performance of organic coatings in microelectronics is crucial for ensuring device longevity. However, exposure to humidity and electrical stress can degrade insulation properties and significantly reduce operational life. Unraveling the underlying failure mechanisms in organic and other high-impedance (HiZ) insulating materials is challenging, yet essential. One potential contributor – ion migration – remains insufficiently explored despite its possible detrimental effects. This work addresses this gap by systematically investigating the role of ionic contaminants from the surrounding environment in accelerating insulation failure. Our novel comprehensive multi-method approach combines high resolution, time-resolved current measurements during electrical stress tests, Electrochemical Impedance Spectroscopy (EIS), and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) to capture both transient electrical responses and migration-driven ion distributions within the polyimide matrix. Experiments with Ag⁺, Cu²⁺, and K⁺ ions reveal that the specific ion type critically influences the time-to-failure, with distinct failure modes observed – suggesting electrochemical processes at the interface between coating and metal as key breakdown mechanisms, leading to dendrite growth and localized alkalization. Weibull statistical analysis proves that wear-out mechanisms cause the sample failure. Complementary modeling efforts, including a simplified physical model and a detailed 1D finite element simulation based on the Nernst-Planck-Poisson framework, further elucidate the dynamics of charge transport and ion migration, thereby reinforcing our experimental findings. By advancing our understanding of the interplay between ion migration and insulation degradation, this work goes beyond statistical failure models and deepens the fundamental knowledge of physical failure mechanisms in polyimide coatings. It provides a robust, multifaceted methodology for reliability investigations in wet environments. This approach holds promise for broader applications in the assessment and design of resilient layers in insulating systems.