Adhesion Characterization of Redistribution Layer

Continuous miniaturization of interconnects and conductive trace circuitries in advanced packaging is driving a reduction in feature sizes and effective contact area for copper trace patterns. As adhesion strength is proportional to the size of the bonded surface area, smaller feature sizes in fine circuit patterns for advanced packaging may pose an increased delamination risk. This warrants a need to study and understand the interface adhesion properties for small scale copper trace at 20μm and below. This paper presents the application of peel test method to measure the peel strength of copper redistribution layer (RDL). Analysis using finite element model further demonstrates how the peel test data can be utilized to characterize the adhesion properties at the copper to substrate interface.