Unraveling metallic contaminants in complex polyimide heterostructures using deep ultraviolet spectroscopic ellipsometry

Metallic contaminants in complex heterostructures are important topics due to their significant roles determining physical properties as well devices' performance. Particularly, of polyimide via on Al pad and Cu redistribution layer (RDL) have shown exotic for advanced semiconductor packaging systems. One main problem is leakage current variations, which affect the performance devices, yet its origin far from understood. Furthermore, metal contaminations, if any, would occur at buried interfaces, it particularly challenging probe them. Until now, electronic optical metallic not been studied extensively. Herewith, using spectroscopic ellipsometry broad deep ultraviolet (DUV) range supported with finite-difference time-domain calculations, we determine various concentration influence device under-bump vias RDL architectures, especially metal–bump interface surface between RDL. The dielectric function reveals varying contamination levels different metals responsible chip embedded within ∼50 nm polyimide, distinguishable concentrations (1.3%–30% relative volume fraction), agreement contact measurements highly structures. Our result shows potency DUV paves way nondestructive, quality control metrology applications integrated electronics