Crack Identification in BEoL Stacks Using Acoustic Emission Testing and Nano X-ray Computed Tomography

• Published in: 2020 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) pp. 1 - 6
• Main Authors: Silomon, Jendrik, Gluch, Jurgen, Clausner, Andre, Paul, Jens, Zschech, Ehrenfried
• Format: Conference Proceeding
• Language: English
• Published: IEEE 20-07-2020
• Subjects: Acoustic emission; Acoustic measurements; Back End of Line; Chip Package Interaction; Copper; Force; Micro-crack; Semiconductor device measurement; Shearing; X-ray Computed Tomography; X-ray imaging
• ISSN: 1946-1550
• DOI: 10.1109/IPFA49335.2020.9260701

A novel approach is presented to evaluate the mechanical stability of back end of line (BEoL) stacks. A SRAM test vehicle manufactured in 28 nm technology with copper pillar bumps is used. To inflict damage to the BEoL of the given semiconductor device, external forces are applied to the copper pillars by shear loading using a tribo-indenter system. An acoustic emission (AE) detection sensor is attached to the sample to measure acoustic waves during the shear experiment as an indication for damage. The damage progression in the BEoL stack is extremely fast, hence details can't be resolved with the piezo sensors of the tribo-indenter anymore. However, due to the much higher temporal resolution AE measurements give a more precise insight into the damage process. The resulting damages are imaged using nano X-ray computed tomography (nXCT) as well as scanning electron microscopy (SEM). The results provide a better understanding of the origin and the propagation of damages in the BEoL stack.