To be better prepared to use laser based failure isolation techniques on field failures of complex integrated circuits, simple test structures without any failures can be used to study Optical Beam Induced Resistance Change (OBIRCH) results. In this article, four case studies are presented on the following test structures: metal strap, contact string, VIA string, and comb test structure. Several experiments were done to investigate why an OBIRCH image was seen in certain areas of a VIA string and not in others. One experiment showed the OBRICH variation was not related to the cooling and heating effects of the topology, or laser beam focusing. A 4 point probe resistance measurement and cross-sectional views correlated with the OBIRCH results and proved OBIRCH was able to detect a variation in VIA fabrication.

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