Acoustic Metrology for Fine Pitch Microbumps in 3DIC

The continuing shift to 3D integration requires formation of electrical interconnects between multiple vertically stacked Si devices to enable high speed, high bandwidth connections. Microbumps and through silicon vias (TSV) enable the high-density interconnects for die-to-die and die-to-wafer stacking for different applications. In this paper, we present acoustic metrology techniques for the measurement of multi-layer microbumps. One of the techniques, PULSE™ technology, is a very well-established mature solution for metal film thickness measurements. Repeatability and accuracy of the measurements more than adequately meets the process requirements. We also present a second nondestructive acoustic metrology for measuring taller copper pillars (> 30µm).