Abstract

Precise isolation and resolution of scan chain defects are more critical than ever due to increased reliance on scan-based design to achieve desired test content. At the same time, its diagnosis is becoming more difficult as product design increases in complexity alongside shrinking fabrication processes. In this paper, we present a new scan chain diagnosis procedure that is centered on Load Pass Unload Fail/Load Fail Unload Pass (LPUF/LFUP) and Scan Shift Logic State Mapping (SSLSM) techniques to isolate both stuck-at and timing scan chain faults without the design overhead and defect assumptions of previously proposed methods. More importantly, this procedure is extended to analyze scan chain with multiple defects, which is becoming a more frequent occurrence as process scales down in size.

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