Sideway Scan, Solving the Achilles’ Heel of Scan-based Diagnosis

the IC industry has seen tremendous value in diagnosis-driven yield analysis for speeding up physical failure analysis and yield ramp-up. However poor diagnostic resolution of chain failures in scan-based tests is known to be the Achilles’ heel in this flow. To address the problem, we propose sideway scan, a hardware-based solution for chain diagnosis. Scan chains are divided into multiple groups by clock domains or layout constraints. By introducing cyclic sideway transmission paths across scan chains within a group, the architecture guarantees that the snapshot of a broken chain can be transmitted to one or more good chains and the broken chain can capture value from good chains. Compared with state-of-the-art schemes such as reversible scan and two-dimensional scan, it is the first time a solution can simultaneously accomplish the objectives of manageable hardware overhead, high resolution in volume diagnosis, and flexibility in adaptive diagnosis. Simulation-based experiments validate the effectiveness of sideway scan in diagnosing chain failures caused by single and multiple faults.