Utilizing circuit structure for scan chain diagnosis

Scan chain diagnosis has become a critical issue to yield loss in modern technology. In this paper, we present a scan chain partitioning algorithm and a scan chain reordering algorithm to improve scan chain fault diagnosis resolution. In our scan chain partition algorithm, we take into consideration not only logic dependency but also the controllability between scan flip flops. After partition step, the ordering of scan cells is performed to decrease the range of suspect faulty scan cells by a bipartite matching reordering algorithm. The experimental results show that our method can reduce the number of suspect scan cells from 378-31 to at most 3 for most cases of ITC´99 benchmarks.