A Cost Effective Technique for Diagnosis of Scan Chain Faults

Scan based diagnosis plays a critical role in failure mode analysis for yield improvement. However, as the logic circuitry associated with scan chains constitute a significant fraction of a chip's total area the scan chain itself can be subject to defects. In some cases, it has been observed that scan chain failures may account up to 50% of total chip failures. Hence, scan chain testing and diagnosis have become very crucial in recent years. This paper proposes a hardware-assisted low complexity and area efficient scan chain diagnosis technique. The proposed technique is simple to implement and provides maximum diagnostic resolution for stuck-at faults. The proposed technique can be further extended to diagnose scan chain's timing faults.