Non-destructive acoustic metrology and void detection in 3×50μm TSV

Through Silicon Via (TSV) technology represents one key aspect of 3D integration. International Technology Roadmap for Semiconductors (ITRS) has identified a need for an in-line metrology for characterizing voids in TSV structures. We have previously described a laser-based acoustic technique which can be used to detect voids in vias. Results for 10×100 and 5×50μm via structures were reported. In this work, we report on measurements of 3×50μm vias with aspect ratio of ∼17:1. Accuracy of the laser acoustic technique is validated by comparison with cross section images obtained using focused ion beam scanning electron microscopy (FIB-SEM). Measurements typically take a few seconds per site making this non-contact, non-destructive technology an attractive option for in-line void detection.