Improving the Detectability of Resistive Open Faults in Scan Cells

Recent studies have shown that new tests are required for the detection of a large percentage of scan cell internal open faults which are not detected by the existing tests. However, the additional coverage due to the new tests drops significantly when opens with moderate resistances are considered. In this paper we propose to augment earlier test methods to detect internal scan chain opens with a wider range of resistances. The newly proposed method includes application of tests at higher temperatures and modifications to an earlier proposed flush test. We also present an analysis to explain the additional coverage obtained by the proposed test methods.