Fast path selection for testing of small delay defects considering path correlations

Statistical timing models have been proposed to describe delay variations in very deep sub-micron process technologies, which have increasingly significant influence on circuit performance. Under a statistical timing model, testing of a path can detect potential delay failures caused by different small delay defects. Due to path correlations, the potential delay failures captured by two different paths overlap between each other more or less. It is difficult to find a given number of paths that can capture most potential delay failures. In this paper, the path selection problem is converted to a minimal space intersection problem, and a greedy path selection heuristics is proposed, the key point of which is to calculate the probability that the paths in a specified path set all meet the delay constraint. Statistical timing analysis technologies and heuristics are used in the calculation. Experimental results show that the proposed approach is time-efficient and achieves a higher probability of capturing delay failures in comparison with conventional path selection approaches.