Paper 34.3 Analyzing the Effectiveness of Multiple-Detect Test Sets

Multiple-detect test sets have been shown to be effective in lowering defect level. Other researchers have noted that observing the effects of a defect can be controlled by sensitizing affected sites to circuit outputs but defect excitation is inherently probabilistic given a defect’s inherent, unknown nature. As a result, test sets that sensitize every signal line multiple times with varying circuit state has a greater probability of detecting a defect. In past work, the entire circuit is considered when varying circuit state from one vector to another for a given signal line. However, it may be possible to improve defect excitation by exploiting the localized nature of many defect types. Specifically, by varying circuit state in the physical region or neighborhood surrounding a line affected by a defect, the defect excitation and therefore detection can be improved. In this paper, we present a method for extracting a physical region surrounding a signal line but more importantly, techniques for analyzing the excitation characteristics of the region. Analysis ¢ of-detect test sets reveals £¥ ¤ that % ¦ ¤ to % of signal line regions do not achieve at least four unique states, indicating opportunity to further reduce defect level.