Non-Destructive Acoustic Metrology and Void Detection in 3x50 mu m TSV

Through Silicon Via (TSV) technology represents one key aspect of 3-D 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 10x100 and 5x50 mu m via structures were reported. In this work, we report on measurements of 3x50 mu m vias with aspect ratio of similar to 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.