A New Paradigm for Diagnosing Hold-Time Faults in Scan Chains

• Main Author: 徐瑞榮
• Other Authors: Hung-Ming Chen PhD
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/40959614320992669060

碩士 === 國立交通大學 === 電機資訊學院碩士在職專班 === 94 === As the continuing improvement on the semiconductor process technology and EDA (Electronic Design Automation) industry, it allows the current digital IC design to put more functions within the limited silicon die area. However, a million-gate- count design makes the chip testing become more difficult , so DFT(Design for Testability) has gained a lot of popularity recently. The use of the scan chain structure can lower down the difficulty in testing and/or diagnosing complex chips, as the gate count grows, the overhead of scan chains increases accordingly as well. Thus, whether these scan chains function correctly or not will affect the final yield of the chip. Therefore, some mechanisms are needed in order to find out the faulty scan chains if necessary. In the literature, the stuck-at fault is the most popular fault model. For today’s DSM (deep sub-micron) or even nanometer designs, however, this traditional stuck-at fault model is often not adequate when it comes to the fault diagnosis. Other more realistic fault models have been in use, such as the transition fault model (slow to rise, slow to fall), the path delay fault model, the bridge fault model, and the hold- time violation fault model, etc. In the past, the hold-time violation fault model is rarely discussed. But today, it occurs more often and has been one of the main targets in scan chain diagnosis. This thesis will particularly focus on this type of fault model. We propose a new greedy algorithm to explore the faulty flip-flops in the scan chains. As compared to the previous methods, this algorithm is particularly robust and able to identify the fault with a higher success rate, even under some non-ideal situations, e.g., when there are multiple hold-time faults in the scan chain, when the core logic is also faulty, or when the hold-time faults are intermittent.