Enhanced Fault Localization strategies through versatile Sample Preparation Techniques for Electro Migration defect preservation and characterization

This paper presents a cutting-edge extension of the package-die level sample preparation approach that allows for a versatile fault localization step in identifying the electromigration signature (EM) in power-integrated circuits that utilize Copper Redistribution Layer (CuRDL) technology. This innovative methodology demonstrates a comprehensive understanding of the nature of the defect by manipulating well-known failure analysis (FA) methods to pinpoint the exact location where the defect resides. The process consists of backside sample preparation, followed by fault localization using the Optical Beam Induced Resistance Change (IR-Obirch) method. Then, it continues with the newly introduced package lapping method from the frontside under controlled conditions. The analysis further characterizes the defect using advanced cross-sectional analysis techniques, including Focused Ion Beam (FIB) and Energy Dispersive X-ray (EDX), which are widely employed in semiconductor analysis. As a result, the signature of the copper element, which had already blended, was identified, and suggested the mechanism of its migration from the anode terminal toward the cathode terminal in the metal interconnection layer. The failure mechanism suggested signs of penetration through the photosensitive layer, which finally resulted in electrical breakdown and severely impacted the area. Based on the achieved results, by leveraging a combination of FA techniques, analysts were able to gain a deeper understanding of the root cause of the defect and can develop targeted solutions to address it.