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

Metallic contaminants in complex heterostructures significantly impact the physical properties and the performance of semiconductor devices. In advanced electronics packaging, the quality polyimide via on Al pad and Cu redistribution layer (RDL) is critical. Induced Leakage current variations from metal contaminants, affecting device performance, is located at the interface of these devices, posing challenges for in-situ detection. In this work, we utilize spectroscopic ellipsometry (SE) in broad deep ultraviolet (DUV) range supported with finite-difference time-domain (FDTD) calculations, to determine optical properties of semiconductor heterostructures with varying metal contaminants and probe the under-bump vias, RDL architectures, and at the metal-bump interface between the RDL. Our work reveals that the complex dielectric function and theoretical simulation can detect the relative depth and type of the contaminants, in agreement with contact measurements. Our result shows the potential of broad-range SE and for non-destructive quality control and metrology applications in integrated advanced electronics packaging systems.