Electro-Optical Probing for Capturing Fast-to-Rise Scan Chain Failures

The paper discusses an imaging sensor exhibiting a fast-to-rise sanity check failure from a scan chain test. The DUT was prepared for backside analysis in a portable daughter-card [1] that enabled the analyst to easily shift between testing platforms such as a standard imaging tester bench and compact scan diagnosis system [2], while being inspected under the Electro-Optical Probing (EOP) machine. To find a failing flip-flop in several-thousands long chain, broken scan chain analysis was performed to narrow down the search to a few chain links was implemented. EOP methods of fault isolation were employed to verify the location of the broken scan cell in those selected flip-flops. Finally, parallel lapping was done to confirm the location of the failing flip-flop under a SEM.