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January 15, 2015

Non-Destructive Acoustic Metrology for Void Detection in TSV’s

Presented at IWLPC 2014

Advanced interconnect technologies such as Through Silicon Vias (TSV) have become an integral part 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. In this paper, we describe a laser-based acoustic technique in which a short laser pulse generates broadband acoustic waves that propagate in the TSV structure. An optical interferometer detects the surface displacement caused by the acoustic waves reflecting within the structure as well as other acoustic waves traveling near the surface that has information about the structure dimensions and irregularities. Sensitivity of the technique to detect various types of voids has been confirmed by performing cross-section microscopy. Measurements typically take few seconds per site and can be easily adopted for in-line process monitoring. The technique has also demonstrated capability for measuring copper pillar stacks, characterizing bonding voids and delamination.

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